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   6502篇
  免费   4篇
电工技术   2篇
化学工业   13篇
建筑科学   2篇
轻工业   4篇
水利工程   1篇
石油天然气   1篇
无线电   9篇
一般工业技术   11篇
冶金工业   6454篇
自动化技术   9篇
  2023年   1篇
  2019年   2篇
  2016年   1篇
  2015年   1篇
  2014年   1篇
  2011年   3篇
  2007年   2篇
  2006年   2篇
  2005年   3篇
  2003年   11篇
  2002年   1篇
  2001年   4篇
  2000年   4篇
  1999年   159篇
  1998年   1920篇
  1997年   1132篇
  1996年   755篇
  1995年   386篇
  1994年   344篇
  1993年   386篇
  1992年   49篇
  1991年   102篇
  1990年   104篇
  1989年   89篇
  1988年   101篇
  1987年   87篇
  1986年   76篇
  1985年   59篇
  1983年   12篇
  1982年   32篇
  1981年   47篇
  1980年   57篇
  1978年   26篇
  1977年   180篇
  1976年   350篇
  1975年   10篇
  1955年   4篇
  1954年   3篇
排序方式: 共有6506条查询结果,搜索用时 15 毫秒
101.
102.
Sera from 82 cases of leptospirosis (confirmed by micro-agglutination tests or IFAT) and 108 patients with other diseases were investigated using the microcapsule agglutination test (MCAT) for leptospirosis. The overall sensitivity (90.2%), specificity (96.3%), positive predictive value (94.9%), negative predictive value (92.9%), and accuracy of the MCAT (93.7%) were encouraging. MCAT is simple, can be performed by unskilled personnel with minimum laboratory facilities, and produces results in 3 h. MCAT would be a reliable serodiagnostic test for rapidly screening individuals for leptospirosis, in various geographical areas of Thailand.  相似文献   
103.
BACKGROUND: Questionnaire-based surveys from several countries have consistently detected adverse health associated with home dampness and mould growth. METHODS: To test the validity of questions commonly used to indicate the presence of indoor mould, questionnaires were administered in 403 homes where dust samples were taken for viable fungi and air samples for ergosterol. RESULTS: Geometric mean concentrations of the total viable fungi were 255 (SE 116) x 10(3) CFU/g when mouldy odours were reported and 155 (SE 55) when odours were not reported (P = 0.01). Similarly, reported water damage was associated with a 50% increase (P = 0.06). Geometric mean concentrations of the predominantly indoor-source fungi, Aspergillus plus Penicillium, were twice as high when mould or mildew was reported than when not mentioned (P = 0.01). The presence of reported mould or water damage was unrelated to the presence of detectable levels of ergosterol. There was evidence for reporting bias: in the presence of low concentrations of viable fungi in dust, respondents reporting allergies were more likely to report visible mould growth (odds ratio [OR] = 1.8, 95% confidence interval [CI]: 0.9-3.5, P = 0.10. In the presence of elevated concentrations of dust fungi, respondents who smoked were less likely to report visible mould growth, (OR = 0.4, 95% CI: 0.2-0.7, P = 0.005). CONCLUSIONS: Reported mould, water damage, and mouldy odours were associated with elevated levels of indoor fungi. However, inaccuracy was high and there was evidence of a systematic reporting bias. Future research should concentrate on developing accurate objective measures of exposure to fungi, and then use this information to develop valid questionnaires. Currently, objective measures not questionnaires, are recommended to clarify the health effects of indoor fungi.  相似文献   
104.
105.
Pantoprazole is a specific inhibitor of the H+/K(+)-ATPase of the gastric parietal cell. The dose-dependency of a range of pantoprazole pharmacokinetic characteristics was studied. Twelve healthy male subjects were given 10, 20, 40 and 80 mg pantoprazole intravenously according to a randomized, single blind, 4-period change-over scheme. The area under the concentration vs time curve (AUC) and the maximum serum concentration (Cmax) showed a linear increase in line with the dose. Apparent volume of distribution (Vd area), clearance (Cl) and terminal half-life (t1/2) were independent of the dose. The dose-independent elimination of pantoprazole was attributed to the lack of interaction of the drug with cytochrome P450. In clinical practice, a good predictable response, as well as a low potential for interaction with other drugs might be expected.  相似文献   
106.
OBJECTIVE: To determine the relative influences of induction of withdrawal bleedings secretory transformation, and reduction of mitosis in glands on prevention of endometrial hyperplasia during long-term hormonal replacement therapy. DESIGN: Observational expanded clinical case report. SETTING: Reproductive Endocrine Department of Hospital Necker, Paris, France, and Pathology Department of Women's Hospital, Los Angeles County and University of Southern California Medical Center, Los Angeles, California. PATIENTS: Postmenopausal women seeking treatment for symptomatic menopause. INTERVENTIONS: Endometrial biopsy and/or ambulatory hysteroscopy. MAIN OUTCOME MEASURE: Endometrial histology including progestational maturation patterns and glandular epithelial mitosis rates. Macroscopic endometrial appearance. RESULTS: The use of larger doses of E2 and P induced more marked secretory changes and more frequent withdrawal bleeding than the lower doses. There was no evidence of endometrial hyperplasia after 5 years of E2/P replacement therapy independently of bleeding pattern or progestational maturation. Consistent reduction of mitosis rates in glandular epithelium was found after 9 or more days of P administration in each cycle. CONCLUSIONS: Control of endometrial growth is mainly related to control of mitosis in glands by a relatively low doses of P. Induction of withdrawal bleeding and endometrial secretory transformation, which require larger doses of Progesterone, do not provide additional benefit for prevention of hyperplasia. Induction of amenorrhea with a relatively low dose of P may be offered to women seeking hormone replacement therapy with similar levels of safety.  相似文献   
107.
The Shc adaptor protein, hereafter referred to as ShcA, possesses two distinct phosphotyrosine-recognition modules, a C-terminal Src homology 2 (SH2) domain and an N-terminal phosphotyrosine-binding (PTB) domain, and is itself phosphorylated on tyrosine in response to many extracellular signals. Phosphorylation of human ShcA at Tyr-317 within its central (CH1) region induces binding to the Grb2 SH2 domain and is thereby implicated in activation of the Ras pathway. Two shc-related genes (shcB and shcC) have been identified in the mouse. shcB is closely related to human SCK, while shcC has not yet been found in other organisms. The ShcC protein is predicted to have a C-terminal SH2 domain, a CH1 region with a putative Grb2-binding site, and an N-terminal PTB domain. The ShcC and ShcB SH2 domains bind phosphotyrosine-containing peptides and receptors with a specificity related to, but distinct from, that of the ShcA SH2 domain. The ShcC PTB domain specifically associates in vitro with the autophosphorylated receptors for nerve growth factor and epidermal growth factor. These results indicate that ShcC has functional SH2 and PTB; domains. In contrast to shcA, which is widely expressed, shcC RNA and proteins are predominantly expressed in the adult brain. These results suggest that ShcC may mediate signaling from tyrosine kinases in the nervous system, such as receptors for neurotrophins.  相似文献   
108.
Human apolipoprotein (apo) E, a polymorphic protein with three common alleles, epsilon 2, epsilon 3, and epsilon 4, plays an important role in lipoprotein metabolism. This article describes the association of this polymorphism with lipids, apolipoproteins, and lipoproteins with a particular regard to lipoprotein particles, as defined by their apolipoprotein content, as well as the risk of myocardial infarction in a multicenter population-based case-control study (ECTIM study). In the ECTIM study, 574 male patients aged 25 to 64 were examined 3 to 9 months after myocardial infarction in four regions participating in the World Health Organization MONICA project: Belfast (Northern Ireland) and Lille, Strasbourg, and Toulouse (France). Control subjects (n = 722) were randomly selected from the regional populations. The distribution of apoE phenotypes was significantly different across the four control samples (P = .04), with a higher frequency of the epsilon 4 allele in Belfast (14.3%) than in Toulouse (8.2%). The association of apoE polymorphism with biological measurements was studied in the control groups (n = 640) after men with coronary heart disease or those taking hypolipidemic drugs were omitted, with the apoE3/3 phenotype as a reference after adjustment for concomitant factors. Individuals carrying the epsilon 2 allele had lower levels of plasma cholesterol, low-density lipoprotein cholesterol (LDL-C), and apoB and higher levels of triglycerides, very-low-density lipoprotein cholesterol (VLDL-C), apoC-III, apoE, lipoprotein (Lp) C-III:B, and Lp E:B. However, the effect of the epsilon 2 allele on triglyceride, VLDL-C, apoE, and Lp E:B parameters was heterogeneous across the populations.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
109.
110.
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