全文获取类型
收费全文 | 486篇 |
免费 | 1篇 |
专业分类
电工技术 | 3篇 |
综合类 | 8篇 |
化学工业 | 2篇 |
金属工艺 | 1篇 |
机械仪表 | 3篇 |
建筑科学 | 2篇 |
矿业工程 | 1篇 |
能源动力 | 1篇 |
轻工业 | 2篇 |
水利工程 | 2篇 |
无线电 | 18篇 |
一般工业技术 | 1篇 |
冶金工业 | 437篇 |
自动化技术 | 6篇 |
出版年
2020年 | 1篇 |
2014年 | 1篇 |
2013年 | 1篇 |
2012年 | 2篇 |
2011年 | 3篇 |
2010年 | 4篇 |
2009年 | 1篇 |
2008年 | 1篇 |
2007年 | 6篇 |
2006年 | 3篇 |
2005年 | 1篇 |
2004年 | 3篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 8篇 |
1998年 | 123篇 |
1997年 | 90篇 |
1996年 | 48篇 |
1995年 | 30篇 |
1994年 | 15篇 |
1993年 | 29篇 |
1992年 | 4篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1985年 | 7篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 10篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 16篇 |
1976年 | 52篇 |
排序方式: 共有487条查询结果,搜索用时 15 毫秒
91.
Central hemodynamics was studied by thermodilution in 16 patients with acquired mitral defect during surgery under conditions of hypothermia without perfusion. Cooling and surgical correction were carried out under superficial ether anesthesia with morphine and droperidol. A 28% decrease of the minute circulation volume is observed as early as under general anesthesia and at the very beginning of cooling (10.8% more); this decrease is caused by rarer heart contractions and increase of the total peripheral vascular resistance as a result of body response to cool exposure. An almost 10 degrees C drop of body temperature (to 27.2 +/- 0.2 degrees C) involves a just 13% decrease of the cardiac index in comparison with the value at the beginning of cooling. Injection of droperidol before cooling blocks the increase of the total peripheral resistance in a dose-dependent mode (about 0.13 mg/kg of droperidol is needed for sufficiently complete prevention of the increase of total peripheral resistance), and thus maintains the stroke and cardiac indexes at a sufficiently high level. Morphine (in doses of up to 2.3 mg/kg) did not bring about such an effect. 相似文献
92.
D Gautrin C Infante-Rivard TV Dao M Magnan-Larose D Desjardins JL Malo 《Canadian Metallurgical Quarterly》1997,155(6):1841-1847
Atopy, specific IgE sensitization, and bronchial hyperresponsiveness (BHR) were examined in a cohort of 769 apprentices starting career programs in animal health or veterinary medicine (Group 1), pastry making (Group 2), and dental hygiene (Group 3). The hypothesis were that: (1) a proportion of subjects can be "sensitized" although no significant specific occupational exposure has occurred; and (2) there is a relationship between baseline specific sensitization to work-related antigens and host characteristics. Skin tests were administered using 11 common inhalants and specific allergens, including six laboratory animal extracts, three cereal antigens, alpha-amylase, and latex. Methacholine challenge tests were performed. The prevalence of atopy was 54.4% in Group 1, 58.1% in Group 2, and 52.5% in Group 3. Skin reactivity to work-specific proteins was as follows: laboratory animal proteins, 13.8% in Group 1, 14.0% in Group 2, and 15.6% in Group 3. No subject was sensitized to alpha-amylase, whereas 1.2% in Group 1, 5% in Group 2, and 4.1% in Group 3 were sensitized to flour. Five subjects reacted to latex. BHR (PC20 < or = 8 mg/ml) was present in 17.6%, 21.2%, and 14.8% of subjects in Groups 1, 2, and 3, respectively. Specific sensitization was associated with positive skin reactions to common allergens, work-related symptoms, and BHR. These results suggest that students starting career programs with exposure to high-molecular-weight allergens have a low but substantial frequency of specific sensitization to work-related allergens that is related to atopy and BHR. 相似文献
93.
EK Khusnutdinova TV Viktorova IM Khidiiatova RI Fatkhlislamova TE Ivashchenko 《Canadian Metallurgical Quarterly》1997,33(9):1291-1296
Data on allelic polymorphism of MET and D7S23 DNA loci linked to the human cystic fibrosis gene studied in three Bashkir ethnic groups and some Volga-Ural populations (Tartars, Maris, Mordovians, Udmurts, Chuvashs, and Komis) are presented. Udmurts were found to be substantially different from Bashkirs, Tartars, Mordovians, and Chuvashs by the allele frequency distribution observed for MET, while Komis and Bashkirs differed by this parameter from Mordovians and Maris. Comparative analysis of restriction fragment length polymorphism (RFLP) at the D7S23 locus revealed statistically significant differences in genotype frequencies between Bashkirs of the Arkhangel' skii region and populations of Mordva and Udmurtia. In this respect, the Mordovian population appeared to be notably different from the populations of Bashkortostan, Tatarstan, Marii-El, Udmurtiya, Chuvashiya, and Komis. Genetic distances were calculated and corresponding dendrograms were constructed on the basis of data on Met-H, CS.7, and the ApoB locus hypervariable region allelic frequencies. Three ethnogeographic Bashkir groups belonging to one tree branch were found to be closely related to the populations of Tartars, Maris, Udmurts, and Chuvashs and substantially different from Komis and Mordovians. Thus, the position of Volga-Ural populations on the dendrogram corresponds to the degree of relationship between the Finno-Ugric and Turkic populations, confirming the usefulness of DNA polymorphism analysis for the study of the genetic structure of populations. 相似文献
94.
TV Lasukova EV Uskina SA Afanas''iev IV Ponomarenko NV Naryzhnaia AM Cherniavski? IuB Lishmanov 《Canadian Metallurgical Quarterly》1997,60(5):51-53
Comparative study of the cardioprotective effect of antioxidants emoxipin and hystochrom was conducted in patients with chronic ICD during and after operation for aorto-coronary shunting. Both drugs effectively inhibited LPO activation and reduced the reperfusion damage to the myocardium recorded according to the release of MB-PCK into the blood. The new antioxidant hystochrom proved to be more effective. Its prevalent effect is associated with its higher antioxidant activity. 相似文献
95.
INTRODUCTION: Comprehensive emergency medical services and helicopter aeromedical transport systems have been developed based on the principle that early definitive care improves outcome. The purpose of this study was to compare outcomes between patients transported by helicopter and those transported by ground. METHODS: Data were obtained from the North Carolina Trauma Registry for the period between 1987 and 1993 on all patients transported by helicopter and ground admitted to one of the eight state designated trauma centers. Study patients included only those who were transported directly from the scene of injury to the trauma center (interhospital transfers were excluded). Mortality (outcome) was compared after patient stratification by injury severity and transport time, using Cochran-Mantel-Haenszel statistics and logistic regression-derived probabilities of survival. RESULTS: One thousand three hundred forty-six patients (7.3% of the total) were transported from scene to trauma center by helicopter and 17,144 were transported by ground. In patients transported by helicopter, the mean Trauma Score was lower (12 +/- 3.6) versus 14.3 +/- 3.6 (p < 0.001) and the mean Injury Severity Score was higher (17 +/- 11.1) versus 10.8 +/- 8.4 (p < 0.001). A trend toward increased survival was observed among patients transported by helicopter with a higher Injury Severity Score. Statistical significance was achieved only for patients with a Trauma Score between 5 and 12 and Injury Severity Score between 21 and 30. CONCLUSION: The large majority of trauma patients transported by both helicopter and ground ambulance have low injury severity measures. Outcomes were not uniformly better among patients transported by helicopter. Only a very small subset of patients transported by helicopter appear to have any chance of improved survival based on their helicopter transport. This study suggests that further effort should be expended to try to better identify patients who may benefit from this expensive and risky mode of transport. 相似文献
96.
This paper is an update on the issue of dental student debt and provides additional data and an exploration of continued trends which were outlined by Douglass and Fein in the 1995 IOM study of The Future of Dental Education. Dental school tuitions have continued to increase at rates at or above the consumer price index. These tuition bills are increasingly being met by debt financing on the part of the students. These trends are described and then related to recent data on the future plans of dental school seniors. The second part of the paper will provide new updated date on dentists' incomes and analyze the trend in dental fees versus the consumer price index. The final section provides a summary of pay back mechanisms currently being offered to students. 相似文献
97.
OE Surnina VI Lupandin OS Silivanova TV Zvereva 《Canadian Metallurgical Quarterly》1997,47(4):658-663
Two groups of children (5-6-year-old and 7-8-year-old) were presented with pairs of sound signals of the same or different durations. Sound signal durations in pairs could be 1.0, 1.2, 1.5, and 2.0 sec. The children had to detect the difference between the sounds in a pair. The obtained data were compared to the analogous results shown by the 18-39-year-old subjects. It was found out that the ability to discriminate intervals of short duration substantially improved with age. This phenomenon in presumably connected with perfection of the short-term memory. Independently of the subject's age, the order of presentation of signals in a pair influences the ability to discriminate between their durations. 相似文献
98.
OBJECTIVE: Treatment with metformin is occasionally associated with the development of severe lactic acidosis. However, this is usually observed in patients with major contraindications to the drug. In this study, we aimed to determine the prevalence of conditions currently regarded as either contraindications or cautions to the use of metformin in patients with NIDDM. RESEARCH DESIGN AND METHODS: The case notes of metformin-treated NIDDM patients (mean age 62 years) attending a United Kingdom university hospital diabetes clinic over a 3-month period were reviewed according to criteria reflecting a pragmatic view of current prescribing recommendations. RESULTS: Of 89 consecutive patients whose notes could be evaluated in detail, only 41 (46%) had no contraindications or cautions to metformin whatsoever. Concomitant chronic disorders associated with a potentially increased risk of hyperlactatemia were renal impairment (n = 2; plasma creatinine concentrations 1.7 and 2.3 mg/dl, respectively), cardiac failure (n = 2), and chronic liver disease (n = 2). Other potentially relevant disorders included ischemic heart disease (n = 20), clinical proteinuria (n = 14), peripheral vascular disease (n = 22), and pulmonary disease (n = 7). Multiple conditions (i.e., two, three, or four) were present in eight, five, and one patient(s), respectively. CONCLUSIONS: More than half the patients in our series had concomitant conditions or complications conventionally regarded as cautions or contraindications to metformin; approximately 10% had a multiplicity of such conditions. Regular surveillance is necessary to detect the development of complications such as renal impairment. Vigilance is also required in view of the increased risk of major intercurrent illnesses, which may independently disturb lactate metabolism in patients with NIDDM. Metformin should be withdrawn promptly under such circumstances. 相似文献
99.
IuP Altukhov EIu Pobedonostseva LP Filatova TV Malinina NSh Lapteva AI Grigor''ev ON Larina 《Canadian Metallurgical Quarterly》1998,361(5):709-711
Currently, the treatment of falciparum malaria is seriously compromised by spreading drug resistance. We studied the effects of camptothecin, a potent and specific topoisomerase I inhibitor, on erythrocytic malaria parasites in vitro. In Plasmodium falciparum, camptothecin trapped protein-DNA complexes, inhibited nucleic acid biosynthesis, and was cytotoxic. These results provide proof for the concept that topoisomerase I is a vulnerable target for new antimalarial drug development. 相似文献
100.
JP Dubey MC Jenkins DS Adams MM McAllister R Anderson-Sprecher TV Baszler OC Kwok NC Lally C Bj?rkman A Uggla 《Canadian Metallurgical Quarterly》1997,83(6):1063-1069
Hairpin ribozymes with high cleavage activities were designed. An extra sequence was introduced at the 3'-end of the hairpin ribozyme to increase the binding to the substrate RNA, as compared to the wild-type hairpin ribozyme. A three-way junction (TWJ) was formed between the newly designed ribozyme and the substrate RNA. The complex with a solid TWJ showed less RNA cleavage activity than the wild-type hairpin ribozyme. However, the ribozyme with a TWJ with five unpaired bases or propandiol phosphate linkers had higher cleavage activity than the parent ribozyme without the TWJ. When a cis-cleavage system, in which the 5'-end of the substrate RNA was conjugated to the 3'-end of the ribozyme, was employed, the complex with the TWJ containing unpaired bases was also cleaved faster than the complex with the solid TWJ. This suggested that these differences in the cleavage activities were derived from the confirmation, and this was proven by nondenaturing gel electrophoresis. The TWJ hairpin ribozyme containing unpaired bases is able to bind strongly with substrate RNAs and to cleave them efficiently. Since the three-way ribozyme presented here is more active than the wild-type ribozyme, this type of ribozyme can serve as a more efficient tool to control RNA activities in vitro and in vivo. 相似文献