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   28751篇
  免费   1859篇
  国内免费   76篇
耳鼻咽喉   251篇
儿科学   627篇
妇产科学   497篇
基础医学   4066篇
口腔科学   655篇
临床医学   2660篇
内科学   5702篇
皮肤病学   481篇
神经病学   3127篇
特种医学   1141篇
外国民族医学   55篇
外科学   3932篇
综合类   378篇
一般理论   19篇
预防医学   2254篇
眼科学   890篇
药学   1968篇
中国医学   32篇
肿瘤学   1951篇
  2022年   194篇
  2021年   394篇
  2020年   238篇
  2019年   390篇
  2018年   438篇
  2017年   375篇
  2016年   404篇
  2015年   552篇
  2014年   737篇
  2013年   1092篇
  2012年   1614篇
  2011年   1675篇
  2010年   924篇
  2009年   853篇
  2008年   1576篇
  2007年   1710篇
  2006年   1625篇
  2005年   1659篇
  2004年   1567篇
  2003年   1467篇
  2002年   1435篇
  2001年   428篇
  2000年   377篇
  1999年   375篇
  1998年   318篇
  1997年   310篇
  1996年   264篇
  1995年   251篇
  1994年   220篇
  1993年   216篇
  1992年   251篇
  1991年   215篇
  1990年   197篇
  1989年   215篇
  1988年   212篇
  1987年   226篇
  1986年   193篇
  1985年   201篇
  1984年   237篇
  1983年   202篇
  1982年   235篇
  1981年   222篇
  1980年   203篇
  1979年   196篇
  1978年   168篇
  1977年   128篇
  1976年   151篇
  1975年   138篇
  1974年   167篇
  1973年   130篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
It has been proposed that dietary linoleic acid lowers blood pressure (BP) by being converted to arachidonic acid and prostanoids of the two-ene series. We tested the effects of linoleic acid on plasma arachidonic acid, blood pressure, blood viscosity, and RBC cation transport. Oleic acid, the major dietary monounsaturated fat and which is not a prostanoid precursor, was used as a control. Seventeen adults consumed 23 g/d of linoleic acid or oleic acid provided by genetic variants of safflower seed, each for 4 weeks in a double-blind crossover design. Linoleic and oleic acids were enriched significantly in the plasma cholesteryl esters, phospholipids and triglycerides during the respective periods of supplementation but there was no increase in arachidonate. Mean BP was 116.1/76.8 during ingestion of oleic and 113.6/74.6 during ingestion of linoleic acid (p = 0.09 systolic, p = 0.12 diastolic). The power of the study was over 75% for detecting a significant (p less than 0.05) effect of 4 mm Hg in systolic BP or diastolic BP. Whole blood and plasma viscosity, and RBC Li/Na countertransport, Na/K cotransport, and Na pump systems (Vmax) were unchanged during the protocol. Therefore, variations in dietary linoleic or oleic acids are unlikely to have major effects on BP or on several membrane-dependent erythrocyte functions related to hypertension.  相似文献   
82.
83.
84.
Complex interactions in Parkinson's disease: a two-phased approach.   总被引:4,自引:0,他引:4  
The identification of pathogenic mutations in the three genes alpha-synuclein, parkin, and ubiquitin carboxy-terminal hydrolase L1 (UCHL1) has elucidated the ubiquitin proteasome system (UPS) and its potential role as a causal pathway in Parkinson's disease (PD). In addition, polymorphisms of these three genes have been shown to be independently associated with PD. In a sample of 298 unrelated PD cases and 185 controls, we applied a two-phased approach of recursive partitioning and logistic regression analyses to explore complex interactions. For women only, we observed an epistatic interaction of UCHL1 and alpha-synuclein genotypes with significant effects on PD risk (odds ratio = 2.42; P = 0.003). Our findings are consistent with the hypothesis that PD is a multigenic disorder of the UPS.  相似文献   
85.
86.
Evaluative composite measurement scales (CMS) are increasingly used in medicine to measure complex constructs in the absence of a reference criterion or ‘gold standard’. However, the level of measurement provided by these instruments has usually been given little attention. This paper explores the influence of the characteristics of the item set and weighting on the level of measurment of an evaluative CMS. The approach is illustrated with an application to the scoring system of the Nottingham Health Profile. Simulations are provided to indicate when the composite score of item responses, on an ordinal or pass—fail scale, could be considered to achieve the properties of an interval scale.  相似文献   
87.
A new radiolucent device for increased accuracy of CT-guided fine-needle punctures permits precise determination of the optimum angle, depth, and position of the fine needle, which can be preset from the data supplied on the CT monitor. Puncture and repeat scans for controlling the tip of the needle can be performed with the patient in a stationary position. The device is designed as a belt that holds a needle holder sheath and a goniometric scale, both of which can be moved to varying positions around the patient.  相似文献   
88.
Bulimia nervosa is a health problem of increasing magnitude that is estimated to affect 2–5% of the American adolescent and young adult female population. Because of the magnitude of this clinical problem and because of the importance of the upper gastrointestinal tract in its expression, a intradepartmental program of health care for patients affected with the disease was initiated. Eleven consecutive symptomatic bulimic individuals have been evaluated jointly by the gastroenterology and the psychiatry departments of the University of Pittsburgh. Five of these 11 individuals were found to have clinically important upper gastrointestinal pathology including ulcerative esophagitis, erosive gastritis, duodenal ulcer, and delayed gastric emptying. These gastrointestinal conditions could have been either a result of or have contributed to the symptomatology of these five patients. These data suggest that bulimic subjects have clinically important gastroenterological disease processes that require specific diagnosis and treatment independent of the psychiatric treatment provided for the bulimic condition.This work was supported in part by grants from NIDDK AM 32556.  相似文献   
89.
Our purpose was to investigate the eliciting threshold concentration of formaldehyde in formaldehyde-sensitive individuals in the occluded and non-occluded patch teat and to evaluate the relationship in repeated open application test (ROAT) with a product containing a formaldehyde releaser. 20 formaldehyde-sensitive patients and a control group of 20 healthy volunteer were included in the study. Occluded and non-occluded patch tests with formaldehyde solutions form 25 to 10,000 ppm. and ROAT for I week with a leave-on cosmetic product containing on average 300 ppm formaldehyde. Were carried out simultaneously on each subject. In the occluded patch test. 1/2 of the 20 patients only reacted to 10,000 ppm formaldehyde. 9 reacted to 5,000 ppm. 3 reacted to 1.000 ppm. 2 reacted to 500 ppm and I reacted to 25 ppm. No definite positive reactions were observed in the non-occluded patch test or in the ROAT No positive reactions were observed in the control group to any of the test procedures. We concluded that the threshold concentration for occluded patch test to formaldehyde in formaldehyde-sensitive patients was 250 ppm. The threshold in occluded patch test corresponded to the degree of sensitivity Definite positive reactions in the ROAT were not seen, either indicating that they are unlikely to happen with the type of product used or that the exposure time was too short.  相似文献   
90.
Modulation of DNA synthesis by 2,3,7,8-tetrachlorodi-benzo-p-dioxin(TCDD) was studied in primary cultures of hepatocytes and inrat liver epithelial cells (WB-F344) to develop models for studieson the interactions between the activated Ah receptor and cellulargrowth control. In hepatocytes TCDD either positively or negativelymodulated EGF-stimulated DNA synthesis. In the presence of ethlnylestradiol10–12 M TCDD moderately increased EGF-stimulated DNA synthyesis(  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