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   18955篇
  免费   1790篇
  国内免费   42篇
耳鼻咽喉   154篇
儿科学   553篇
妇产科学   335篇
基础医学   2766篇
口腔科学   400篇
临床医学   2234篇
内科学   4040篇
皮肤病学   450篇
神经病学   1455篇
特种医学   712篇
外科学   3099篇
综合类   460篇
一般理论   10篇
预防医学   1624篇
眼科学   271篇
药学   1265篇
中国医学   19篇
肿瘤学   940篇
  2021年   224篇
  2020年   173篇
  2019年   266篇
  2018年   256篇
  2017年   243篇
  2016年   257篇
  2015年   286篇
  2014年   416篇
  2013年   597篇
  2012年   892篇
  2011年   838篇
  2010年   467篇
  2009年   502篇
  2008年   769篇
  2007年   849篇
  2006年   819篇
  2005年   824篇
  2004年   761篇
  2003年   727篇
  2002年   674篇
  2001年   571篇
  2000年   677篇
  1999年   542篇
  1998年   305篇
  1997年   258篇
  1996年   258篇
  1995年   206篇
  1994年   207篇
  1993年   210篇
  1992年   494篇
  1991年   467篇
  1990年   413篇
  1989年   435篇
  1988年   415篇
  1987年   390篇
  1986年   375篇
  1985年   336篇
  1984年   334篇
  1983年   238篇
  1982年   155篇
  1981年   162篇
  1980年   144篇
  1979年   268篇
  1978年   169篇
  1977年   142篇
  1976年   144篇
  1975年   127篇
  1974年   166篇
  1973年   165篇
  1972年   157篇
排序方式: 共有10000条查询结果,搜索用时 117 毫秒
71.
72.
73.
The morbidity of osteoporosis is caused by fractures. Vertebral fractures lead to pain and disability and a decrease in quality of life. A Working Party of the European Foundation for Osteoporosis has developed a specific questionnaire for patients with established vertebral osteoporosis. This questionnaire is intended for use in clinical trials. The questionnaire consists of questions and visual analogue scales in the following domains: pain, activities of daily living, jobs around the house, mobility, leisure and social activities, general health perception and mood. The questionnaire has been translated from English into French, German, Italian, Hebrew, Swedish and Dutch. The questionnaire is currently being validated in a multicentre study involving patients with stable osteoporosis and control subjects. Preliminary results indicate that the reproducibility is sufficient and that the questionnaire is able to discriminate between patients with vertebral osteoporosis and control subjects.  相似文献   
74.
75.
Abstract— Interviews with parents of a non-referred sample of 11–16-year-old girls ( n = 82) revealed that a significantly greater proportion of mothers with a lifetime: history of any psychiatric disorder also reported one or more recent undesirable life events focused on the adolescent compared with mothers with no such history, Lifetime episodes of maternal depression and recent undesirable life events exerted significant additive effects on the likelihood of depression occurring in the previous 12 months in adolescent girls. Some families may be "life event prone" as a consequence of lifetime episodes of parental psychopathology.  相似文献   
76.
The objective of this study was to examine the release of insulin from cultured islet cells, taken from the pancreas of newborn and adult rats, in response to gastric inhibitory polypeptide (GIP), cholecystokinin-8 (CCK-8), calcitonin gene-related peptide (CGRP), and pancreastatin. GIP (10(-9)-10(-7) M) potentiated glucose-stimulated release of insulin in a dose-dependent fashion from both newborn and adult islet cells. CCK-8 (greater than 10(-8) M) also increased glucose-stimulated release of insulin from newborn islet cells, however its effect was not significant and not as strong as that observed with adult islet cells. Culture of newborn islet cells for 3 weeks with media containing high concentrations of glucose (16.7 mM) enhanced insulin release in response to CCK-8. CGRP did not affect the release of insulin from newborn islet cells, whereas at 10(-10) M, it reduced the release of insulin from adult islet cells by 66 +/- 4%. Pancreastatin (10(-9)-10(-8) M) did not affect the release of insulin from newborn islet cells when cells were incubated with 4.2 mM glucose, whereas it stimulated the release of insulin from adult islet cells in a dose-dependent fashion. When incubated with 16.7 mM glucose, pancreastatin inhibited the release of insulin from both newborn and adult islet cells. These results indicate that newborn islet cells experience developmental changes which render them responsive to enteric peptides.  相似文献   
77.
78.
Linear alkyl chains containing 2, 10 and 18 carbon atoms were grafted to 10% of the urethane nitrogens in a polyether-polyurethane. The polyurethane was synthesized from methylene bis(p-phenyl isocyanate), 1,4-butanediol, and polytetramethylene oxide of 1000 molecular weight in a molar ratio of 3/2/1. Fourier transform infrared spectroscopy and attenuated total reflectance optics were used to study the adsorption of 5.0 mg/ml human serum albumin (HSA) at 37 degrees C to the derivatized and non-derivatized polymers. Both delipidized HSA and HSA containing 6.5 mol stearic acid per mol of albumin were used to study the effect of chain length upon the initial adsorption rate, the total amount adsorbed in 1 h, and the desorption rate. The initial adsorption rates revealed that non-specific adsorption was similar upon all four polymers. An increase in initial adsorption rate upon the C-18 derivatized polymer was attributed to a specific binding interaction between the HSA and the grafted alkyl chains. The conformational stability of the HSA also affected the adsorption rate. The total amount adsorbed after 1 h decreased as the alkyl chain length increased from 2 to 18 methylene groups. The desorption rate decreased in magnitude as the alkyl chain length increased from C-2 to C-18. These results support a hypothesis that alkyl chain length influences the interaction between albumin and an alkylated polymer system.  相似文献   
79.
For the past 45 years, there has been a great deal of debate regarding the health issues surrounding the fluoridation of public water supplies. In order to assess the association between fluoridation and hip fracture, we identified 129 counties across the United States considered to be exposed to public water fluoridation and 194 counties without exposure. Data from the Health Care Financing Administration and the Department of Veterans Affairs were used to calculate the incidence of hip fracture among white persons, aged 65 years or older, in fluoridated and nonfluoridated counties. There was a small statistically significant positive association between fracture rates and fluoridation. The relative risk (95% confidence interval) of fracture in fluoridated counties compared to nonfluoridated counties was 1.08 (1.06 to 1.10) for women and 1.17 (1.13 to 1.22) for men. As comparisons were made at the grouped level, it may be inappropriate at this time to draw inferences at the individual level. The relationship observed at the county level needs to be duplicated at the individual level with more precise measures of fluoride exposure.  相似文献   
80.
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