首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   789篇
  免费   3篇
电工技术   4篇
化学工业   69篇
机械仪表   29篇
建筑科学   42篇
矿业工程   13篇
能源动力   4篇
轻工业   192篇
水利工程   7篇
石油天然气   10篇
武器工业   1篇
无线电   29篇
一般工业技术   364篇
冶金工业   1篇
原子能技术   1篇
自动化技术   26篇
  2012年   95篇
  2011年   105篇
  2010年   15篇
  2009年   2篇
  2008年   67篇
  2007年   63篇
  2006年   54篇
  2005年   48篇
  2004年   36篇
  2003年   41篇
  2002年   49篇
  2001年   38篇
  2000年   27篇
  1999年   11篇
  1998年   12篇
  1997年   17篇
  1996年   16篇
  1995年   6篇
  1994年   9篇
  1993年   9篇
  1992年   9篇
  1991年   7篇
  1990年   6篇
  1989年   10篇
  1988年   3篇
  1986年   5篇
  1985年   10篇
  1984年   3篇
  1983年   4篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1979年   2篇
  1978年   2篇
  1972年   1篇
  1967年   3篇
  1957年   1篇
  1954年   1篇
  1948年   2篇
排序方式: 共有792条查询结果,搜索用时 15 毫秒
71.

Objective

To assess the negative health consequences and associated costs of cigarette smoking in Germany in 2003 and to compare them with the respective results from 1993.

Methods

The number of deaths, years of potential life lost (YPLL), direct medical and indirect costs caused by active cigarette smoking in Germany in 2003 is estimated from a societal perspective. The method is similar to that applied by Welte et al, who estimated the cost of smoking in Germany in 1993. Therefore, a direct comparison of the results was possible. Methodological and data differences between these two publications and their effect on the results are analysed.

Results

In 2003, 114 647 deaths and 1.6 million YPLL were attributable to smoking. Total costs were €21.0 billion, with €7.5 billion for acute hospital care, inpatient rehabilitation care, ambulatory care and prescribed drugs; €4.7 billion for the indirect costs of mortality; and €8.8 billion for costs due to work loss days and early retirement. From 1993 to 2003, the proportionate mortality attributable to smoking remained relatively stable, rising from 13.0% to 13.4%. The smoking‐attributable deaths in men is lowered by 13.7% whereas that in women increased by 45.3%. Total real direct costs rose by 35.8%, and total real indirect costs declined by 7.1%, rendering an increase of 4.7% to real total costs. Accountable factors are changes in cigarette smoking prevalence and in disease‐specific mortality and morbidity, as well as a rise in general healthcare expenditure.

Conclusions

Despite the growing knowledge about the hazards of smoking, the smoking‐attributable costs increased in Germany. Further, female mortality attributable to smoking is much higher than it was in 1993.As a result of the devastating health consequences of smoking, many countries have implemented anti‐smoking measures. For example, Ireland and Italy banned smoking in all public buildings and at all workplaces, including pubs and restaurants. Several publications have shown that Germany is still rather friendly to the tobacco industry.1 This is also supported by recent decisions not to implement a smoking ban or to prohibit smoking in all public places. However, Germany increased the tax on tobacco products three times since 2004, which decreased cigarette sales and smoking prevalence in the age group 12–17 years.2,3The first cost‐of‐smoking study for Germany used 1993 as the reference year,4 and was published by some of us. Since then, three other studies have been published: one is by Ruff et al,5 which cannot be used for comparison because of a lack of methodological transparency, and two by Wegner et al,6,7 which considered only indirect costs. Thus, costs of smoking can be compared with only the first study.This study presents the most recent estimate for both direct and indirect costs of cigarette smoking in Germany, based on the latest available data and referring to the year 2003. As a similar method was applied, costs of smoking can be directly compared between 1993 and 2003.  相似文献   
72.
73.
Predicting the fate of microorganisms in the environment is increasingly warranted, especially for pathogenic strains. A major habitat of Escherichia coli, which encompasses commensal as well as pathogenic strains, is the gastrointestinal tract with conditions very different from the environment it encounters after shedding from the host or during cultivation in the laboratory. We developed two relevant growth conditions representative of intestinal (host-associated) and external (postshedding) environments to investigate the surficial properties and behaviors of a diverse subset of E. coli feedlot isolates. Surficial properties may determine an isolate's physical fate. A pronounced increase in cell hydrophobicity and concomitant biofilm mass formation was observed for isolates grown under external conditions. Isolates that exhibited the highest surface hydrophobicity also formed visible suspended aggregates under external conditions. Other than hydrophobicity, flagella-mediated motility was determinant in affecting E. coli biofilm formation under external conditions, with all four nonmotile E. coli isolates characterized as thin-biofilm formers. The majority (88%) of Ag43+ (outer membrane protein, antigen 43) isolates formed thick biofilms, whereas the majority (75%) of Ag43- isolates formed thin biofilms. The tested E. coli O157:H7 strain behaved differently from the environmental E. coli isolates: it displayed a low electrostatic charge, a small decrease in hydrophobicity upon shifts to external conditions, and very little biofilm formation. On the other hand, the commonly used laboratory strain E. coli K-12 displayed low hydrophobicity both intestinally and externally, but it formed significant biofilm mass under external conditions. Clearly, various E. coli strains manifest significant variability in surficial behavior. This variability is further modulated by growth conditions. The interacting strain-inherent and cultivation-dependent effects on surficial behavior may have broad consequences for the fate and ecology of pathogenic and commensal E. coli strains.  相似文献   
74.
氧化锆陶瓷已用作窑炉衬里,窑具、分散介质及球磨介质,加热管生氧敏元件,本文讨论了氧化锆陶瓷的市场特点及各种不同的稳定化作用,陶瓷材料发展的一种新趋势是建立在ZrO2-Al2O3系材料的开发与应用上。  相似文献   
75.
卡.  HH 曾艳 《国外金属矿山》1997,22(3):20-22,28
亚科夫列沃铁矿为保持年产450万t的生产水平和降低成本,采取了一系列技术措施,介绍了所进行的技术改造,内容包括地下采矿法,井上构筑物、地面运输、疏干排水系统、水电为气供应以及两种采矿法过渡时的地质力学问题。  相似文献   
76.
The effect of peripartal supplementation with concentrate enriched at 10% propylene glycol (PG) on metabolism, animal health, fertility, and milk production was studied using 234 cows from 8 dairy farms with production averages of 8019 to 10,656 kg/yr. The feeding schedule for the PG group (n=117) was as follows: 13 d antepartum: 1.5 kg/d (= 150 mL PG); 12 d antepartum until parturition: 3 kg/d (= 300 mL PG); 1 to 12 d postpartum: 1 kg/d (= 100 mL PG). Control cows (n=117) received the same concentrate without PG. From a subset of cows (PG: n = 43; control: n = 40), blood samples were collected at 6, 3, and 1 wk antepartum, 3 d antepartum, on the day of parturition, and 1, 3, 5, 7, 9, and 11 wk postpartum for the determination of nonesterified fatty acids (NEFA), beta-hydroxybutyrate (BHBA), insulin-like growth factor (IGF)-I, and activities of aspartate-aminotransferase (AST) and glutamate-dehydrogenase (GLDH). From another subset of cows (PG: n=11; control: n=10), blood samples were collected 1 wk antepartum, on the day of parturition, and 1 wk postpartum to determine immunophenotypical and functional parameters of blood neutrophils. From 1 wk antepartum to 1 d postpartum, concentrations of NEFA were significantly lower in cows receiving PG compared with controls. Also, concentrations of BHBA in cows receiving PG were significantly lower from 1 wk antepartum until 7 wk postpartum. Concentrations of IGF-I were significantly higher in the PG group, from 1 wk antepartum until 1 wk postpartum than in the control group. Activities of AST and GLDH did not differ between groups. Immunophenotypical and functional characteristics of blood neutrophils were not influenced by treatment nor were animal health, reproduction, or milk production. Although indicators of metabolic status were improved by peripartal use of PG-enriched concentrate, economic benefits are questionable for dairy farms with good nutritional programs, as economically important factors such as milk production, animal health, and fertility were not influenced.  相似文献   
77.
Streptococcus uberis is an important cause of mastitis in dairy cows throughout the world, particularly during the dry period, the period around calving, and during early lactation. Strategies for controlling Strep. uberis mastitis are poorly defined and are currently inadequate. Objectives of the present study were to evaluate efficacy of ceftiofur, a new broad-spectrum cephalosporin antibiotic, for treatment of experimentally induced Strep. uberis intramammary infections (IMI) in lactating dairy cows during early lactation and to determine whether extended therapy regimens enhanced efficacy of ceftiofur. Efficacy of extended ceftiofur intramammary therapy regimens was investigated in 37 mammary quarters of 23 dairy cows that developed clinical mastitis following experimental infection with Strep. uberis during early lactation. Cows that developed clinical mastitis during the challenge period were allocated randomly to 3 groups representing 3 different ceftiofur treatment regimens: 2-d (n = 7 mammary quarters), 5-d (n = 16 mammary quarters), and 8-d (n = 14 mammary quarters) treatment regimens. For all groups, 125 mg of ceftiofur hydrochloride was administered via intramammary infusion. A bacteriological cure was defined as an experimentally infected quarter that was treated and was bacteriologically negative for the presence of Strep. uberis at 7, 14, 21, and 28 d posttreatment. Percentage of Strep. uberis IMI eliminated was 43, 88, and 100% for the 2-, 5-, and 8-d ceftiofur treatment regimens, respectively. Both the 5- and 8-d ceftiofur extended therapy treatment regimens had significantly higher bacterial cure rates than the standard 2-d ceftiofur treatment regimen. The bacterial cure rate of the 8-d ceftiofur extended therapy group was marginally better (P = 0.052) than the 5-d ceftiofur extended therapy group. Results of this study indicate that ceftiofur therapy was effective for eliminating Strep. uberis experimental IMI, and 5- and 8-d extended ceftiofur therapy regimens were more effective than the standard 2-d treatment.  相似文献   
78.
The objective of this study was to evaluate whether supplementing Holstein cows with bovine somatotropin (bST; 142.8 mg/14 d), beginning at 21 d (±3 d) before expected calving and continuing through 42 d in milk (±3 d), affected the incidence rates of retained fetal membranes (RFM), metritis (MET), clinical mastitis (MAS), digestive problems (DIG), ketosis (KET), milk fever (MF), displaced abomasum (DA, left or right), lameness (LAM), or number of sick cows during the first 60 d in milk. Data for multiparous Holstein cows from 3 separate trials were merged for analyses (n = 437). Cows in the bST-supplemented group (n = 162) received biweekly subcutaneous injections of Posilac, whereas control cows (n = 166) and a group of cohorts (n = 109) were not supplemented. Incidences of disease were collected from the herd health records. Across all treatment groups, the incidence rates (number of diseased cows divided by the total number of cows) for RFM, MET, MAS, DIG, KET, MF, DA, and LAM were 8.47, 18.31, 16.02, 4.35, 4.35, 3.66, 3.20, and 3.66%, respectively. The incidence rates of RFM, MET, MAS, DIG, KET, MF, DA, and LAM for cows in the bST-supplemented, control, and cohort groups were 6.79, 7.83, and 11.93%; 16.05, 7.47, and 22.94%; 10.49, 18.07, and 21.10%; 1.23, 5.42, and 7.34%; 1.23, 6.02, and 6.42%; 2.47, 4.22, and 4.59%; 2.47, 3.61, and 3.67%; and 3.70, 3.61, and 3.67%, respectively. The percentages of sick cows (number of cows having one or more cases of disease divided by the total number of cows) in the bST-supplemented, control, and cohort groups were 33.95, 43.37, and 49.54%, respectively. Significant chi-squared values were detected between the bST-supplemented and control groups for MAS, DIG, and KET, with a greater number of healthy cows in the bST-supplemented group. No differences in incidences of diseases or sick cows were detected between the control and cohort groups. Results indicated that a low dose of bST supplemented to Holstein cows for 3 wk prepartum through 60 d in milk reduced the incidences of some calving-related diseases compared with nonsupplemented controls or cohorts. Importantly, no negative effects of bST supplementation on postpartum calving diseases were detected compared with nonsupplemented cows.  相似文献   
79.
Stable isotope fractionation analysis of an aquifer heavily contaminated with benzene (up to 850 mg L(-1)) and toluene (up to 50 mg L(-1)) at a former hydrogenation plant in Zeitz (Saxonia, Germany) has suggested that significant biodegradation of toluene was occurring. However, clear evidence of benzene biodegradation has been lacking at this site. Determining the fate of benzene is often a determining factor in regulatory approval of a risk-based management strategy. The objective of the work described here was the demonstration of a new tool that can be used to provide proof of biodegradation of benzene or other organics by indigenous microorganisms under actual aquifer conditions. Unique in situ biotraps containing Bio-Sep beads, amended with 13C-labeled or 12C nonlabeled benzene and toluene, were deployed at the Zeitz site for 32 days in an existing groundwater monitoring well and used to collect and enrich microbial biofilms. Lipid biomarkers or remaining substrate was extracted from the beads and analyzed by mass spectrometry and molecular methods. Isotopic analysis of the remaining amounts of 13C-labeled contaminants (about 15-18% of the initial loading) showed no alteration of the 12C/13C ratio during incubation. Therefore, no measurable exchange of labeled compounds in the beads by the nonlabeled compounds in the aquifer materials occurred. Isotopic ratio analysis of microbial lipid fatty acids (as methyl ester derivatives) from labeled benzene- and toluene-amended biotraps showed 13C enrichment in several fatty acids of up to delta (13C) 13400%o, clearly verifying benzene and toluene biodegradation and the transformation of the labeled carbon into biomass by indigenous organisms under aquifer conditions. Fatty acid profiles of total lipid fatty acids and the phospholipid fatty acid fraction and their isotopic composition showed significant differences between benzene- and toluene-amended biotraps, suggesting that different microbial communities were involved in the biodegradation of the two compounds.  相似文献   
80.
The objectives of this study were to determine antimicrobial resistance patterns of Staphylococcus aureus strains isolated from bovine clinical mastitis cases and to subtype the strains by polymerase chain reaction (PCR) technique based on coagulase gene polymorphism. Two hundred sixty-five S. aureus isolates collected from individual animals in different herds (n = 235) from 1995 to 2004 were tested for susceptibility to penicillin, ampicillin, amoxicillin-clavulanate, oxacillin, oxytetracycline, enrofloxacin, kanamycin-cephalexin, and trimethoprim-sulfamethoxazole using the agar disc diffusion test. Strains were also tested for β-lactamase production. A total of 29.8% of the strains were susceptible to all antimicrobial agents tested. The highest resistance was observed in 63.3% of the strains against β-lactam antibiotics, penicillin and ampicillin. Oxytetracycline resistance was observed in 27.9% of the strains, either alone or in combination with β-lactams. No resistance was detected for amoxicillin-clavulanate, oxacillin, enrofloxacin and kanamycin-cephalexin. β-Lactamase production and resistance to β-lactam antibiotics were usually correlated. Resistance against β-lactams increased from 43.5% in 1995 to 58 to 77% from 1999 to 2004.One hundred twenty-five strains were examined for coagulase gene polymorphism. The isolates were subtyped into 4 types by coagulase gene-based PCR. A predominant 1000-bp PCR product was observed in 60.8% of the isolates typed. The results indicate that a few coagulase gene types of S. aureus are responsible for the majority of bovine clinical mastitis cases in one province of Central Anatolia region, Turkey.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号