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   939504篇
  免费   66739篇
  国内免费   1370篇
耳鼻咽喉   13067篇
儿科学   24473篇
妇产科学   23321篇
基础医学   134006篇
口腔科学   28525篇
临床医学   81064篇
内科学   185046篇
皮肤病学   19326篇
神经病学   72712篇
特种医学   37226篇
外国民族医学   79篇
外科学   153232篇
综合类   18090篇
现状与发展   1篇
一般理论   235篇
预防医学   62048篇
眼科学   21539篇
药学   73026篇
  3篇
中国医学   2180篇
肿瘤学   58414篇
  2018年   9102篇
  2017年   7144篇
  2016年   7920篇
  2015年   9033篇
  2014年   12193篇
  2013年   17741篇
  2012年   24503篇
  2011年   25504篇
  2010年   15032篇
  2009年   14498篇
  2008年   24964篇
  2007年   26104篇
  2006年   26896篇
  2005年   25810篇
  2004年   24958篇
  2003年   24033篇
  2002年   23557篇
  2001年   54875篇
  2000年   56699篇
  1999年   47122篇
  1998年   10822篇
  1997年   9553篇
  1996年   9659篇
  1995年   8992篇
  1994年   8343篇
  1993年   7665篇
  1992年   35618篇
  1991年   34011篇
  1990年   32842篇
  1989年   31971篇
  1988年   29097篇
  1987年   28349篇
  1986年   26358篇
  1985年   25214篇
  1984年   17904篇
  1983年   15198篇
  1982年   7818篇
  1981年   6791篇
  1979年   15809篇
  1978年   10622篇
  1977年   9080篇
  1976年   7885篇
  1975年   8656篇
  1974年   10491篇
  1973年   9888篇
  1972年   9393篇
  1971年   8883篇
  1970年   8452篇
  1969年   7947篇
  1968年   7230篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
Clinicopathological and electron microscopical findings of eight cases of enzootic nasal adenocarcinoma of sheep, diagnosed solely in one big flock in Slovenia between years 2001 and 2003 are described. All affected sheep were female, their mean age was 4.5 ± 1.5 years and they either belonged to the Istrian pramenka breed (five sheep) or were crossbreeds (three sheep). Tumours that arose from the ethmoid area of the nasal cavity were unilateral in six cases (75%) and bilateral in two cases (25%). All tumours were classified as adenocarcinomas by histopathological examination and they displayed either a combination of tubular and papillary growth or less often solely tubular proliferation. No metastases were detected in regional lymph nodes, brain or other organs. Electron microscopical studies performed on the reprocessed paraffin‐embedded tissues revealed the presence of the virus‐like particles with an average diameter between 70 and 90 nm.  相似文献   
33.
34.
35.
36.
Inter-individual variations in the development of silicosis, even within the same environments, have been reported, which suggest the contribution of genetic factors in silicosis aetiology. The aim of the present study was to determine whether there is any significant genetic influence on the development of silicosis. Furthermore, which genetic loci are responsible for the pulmonary response to silica exposure? Eight strains of inbred mice were used to examine the genetic influence on the lung fibrotic response to silica exposure. After intercross-breeding between the most susceptible and most resistant strains, a genome-wide linkage analysis of quantitative trait loci (QTL) was performed. Hydroxyproline was applied as an index, and genotypes of 167 marker genes were analysed by fragment analysis using a capillary-type sequencer. There was significant inter-strain difference in the mean concentration of hydroxyproline contents among the eight strains of mice. Breeding studies were conducted between the most susceptible, C57BL/6J, and the most resistant strain, CBA/J. A genome-wide linkage analysis of silica-exposed intercrossed cohorts identified significant QTL on chromosome 4 and suggestive QTL on chromosomes 3 and 18. The present study demonstrates that genetic factors may play a significant role in fibrotic-lung responses to silica; one significant and two suggestive quantitative trait loci were identified.  相似文献   
37.
To examine the prevalence of Internet sex networking among men who have sex with men (MSM) in Hong Kong and risk behaviors associated with the behavior, a telephone survey of 15,230 Hong Kong Chinese men aged 18-60 was conducted. Of the 283 active MSM (having engaged in some MSM behaviors in the last 6 months) identified, 17.7% had networked for MSM partners via the Internet in the last 6 months. Younger age (odds ratio [OR] for age < or = 25 vs. age >25 = 4.67, 95% confidence interval [CI] = 2.35-9.28) and being an anal-sex MSM (OR = 4.72, 95% CI=2.36-9.44) were independent predictors of Internet sex networking. Being an Internet sex networker was associated with some risk behaviors such as having contracted a sexually transmitted disease (adjusted OR = 4.79, 95% CI = 1.34-17.11), having had > or = 3 MSM partners (adjusted OR = 4.74, 95% CI = 2.20-10.23), and having engaged in anal sex (adjusted OR = 3.95, 95% CI = 1.89-8.23). HIV prevention programs for MSM should thereby include Internet-based interventions.  相似文献   
38.
Atherosclerotic renal artery stenosis (ARAS) may cause hypertension, progressive renal failure, and recurrent pulmonary edema. It typically occurs in high risk patients with coexistent vascular disease elsewhere. Most patients with ARAS are likely to die from coronary heart disease or stroke before end-stage renal failure occurs. Recent controlled trials have shown that most patients undergoing angioplasty to treat renovascular hypertension still need antihypertensive agents 6 or 12 months after the procedure. Nevertheless, the number of antihypertensive agents required to control blood pressure adequately is lower following angioplasty than for medication alone. Trials assessing the value of revascularization for preserving renal function or preventing clinical events are only in the early recruitment phase. Revascularization should be undertaken in patients with ARAS and resistant hypertension or heart failure, and probably in those with rapidly deteriorating renal function or with an increase in plasma creatinine levels during angiotensin-converting enzyme inhibition. With or without revascularization, medical therapy using antihypertensive, hypolipidemic and antiplatelet agents is necessary in almost all cases.  相似文献   
39.
40.
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