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   7154篇
  免费   400篇
  国内免费   45篇
耳鼻咽喉   130篇
儿科学   219篇
妇产科学   226篇
基础医学   754篇
口腔科学   186篇
临床医学   650篇
内科学   1440篇
皮肤病学   129篇
神经病学   487篇
特种医学   261篇
外科学   1368篇
综合类   145篇
一般理论   3篇
预防医学   587篇
眼科学   231篇
药学   354篇
中国医学   28篇
肿瘤学   401篇
  2023年   52篇
  2022年   135篇
  2021年   212篇
  2020年   153篇
  2019年   191篇
  2018年   250篇
  2017年   171篇
  2016年   179篇
  2015年   175篇
  2014年   260篇
  2013年   314篇
  2012年   508篇
  2011年   533篇
  2010年   269篇
  2009年   259篇
  2008年   366篇
  2007年   361篇
  2006年   360篇
  2005年   327篇
  2004年   324篇
  2003年   293篇
  2002年   286篇
  2001年   142篇
  2000年   162篇
  1999年   144篇
  1998年   63篇
  1997年   56篇
  1996年   40篇
  1995年   27篇
  1994年   39篇
  1993年   32篇
  1992年   81篇
  1991年   81篇
  1990年   66篇
  1989年   55篇
  1988年   55篇
  1987年   61篇
  1986年   75篇
  1985年   65篇
  1984年   30篇
  1983年   21篇
  1980年   16篇
  1979年   33篇
  1978年   23篇
  1977年   16篇
  1976年   22篇
  1975年   14篇
  1974年   30篇
  1973年   25篇
  1972年   19篇
排序方式: 共有7599条查询结果,搜索用时 31 毫秒
1.
2.
3.
4.
5.
6.
This study qualitatively examined factors that influenced contraceptive choices in a sample of young, HIV-infected women. Individual qualitative interviews were conducted among 30 vertically and horizontally HIV-infected women (= 26 African American) from the ages of 14 to 24 years (Mean age = 20.9 years). We recruited sample groups with the following characteristics: (a) current contraceptive/condom use with ≥1 child (= 11); (b) current contraceptive/condom use with no children (= 12); and (c) no current contraceptive/condom use with no children (= 7). A semi-structured interview guide was used to ask participants about factors influencing past and current contraceptive choices. Individual interviews were digitally recorded and transcribed verbatim; analyses to identify core themes were informed by the Grounded Theoretical approach. Young, HIV-infected women did not identify their HIV serostatus or disease-related concerns as influential in their contraceptive decisions. However, they reported that recommendations from health-care providers and input from family and friends influenced their contraceptive choices. They also considered a particular method’s advantages (e.g., menstrual cycle improvements) and disadvantages (e.g., increased pill burden) when selecting a method. Findings suggested that HIV-infected young women’s contraceptive decisions were influenced by factors other than those related to their infection.  相似文献   
7.
We report on 3 patients with pseudoathetosis, which are involuntary, slow, writhing movements due to loss of proprioception.  相似文献   
8.
18F-2beta-Carbomethoxy-3beta-(4-chlorophenyl)-8-(2-fluoroethyl)nortropane (18F-FECNT), a PET radioligand for the dopamine transporter (DAT), generates a radiometabolite that enters the rat brain. The aims of this study were to characterize this radiometabolite and to determine whether a similar phenomenon occurs in human and nonhuman primate brains by examining the stability of the apparent distribution volume in DAT-rich (striatum) and DAT-poor (cerebellum) regions of the brain. METHODS: Two rats were infused with 18F-FECNT and sacrificed at 60 min. Extracts of brain and plasma were analyzed by high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometric (LC-MS) techniques. Two human participants and 3 rhesus monkeys were injected with 18F-FECNT and scanned kinetically, with serial arterial blood analysis. RESULTS: At 60 min after the injection of rats, 18F-FECNT accumulated to levels about 7 times higher in the striatum than in the cortex and cerebellum. The radiometabolite was distributed at equal concentrations in all brain regions. The LC-MS techniques identified N-dealkylated FECNT as a major metabolite in the rat brain, and reverse-phase HPLC detected an equivalent amount of radiometabolite eluting with the void volume. The radiometabolite likely was 18F-fluoroacetaldehyde, the product expected from the N-dealkylation of 18F-FECNT, or its oxidation product, 18F-fluoroacetic acid. The distribution volume in the cerebellum increased up to 1.7-fold in humans between 60 and 300 min after injection and 2.0 +/- 0.1-fold (mean +/- SD; n = 3) in nonhuman primates between 60 and 240 min after injection. CONCLUSION: An 18F-fluoroalkyl metabolite of 18F-FECNT originating in the periphery confounded the measurements of DAT in the rat brain with a reference tissue model. Its uniform distribution across brain regions suggests that it has negligible affinity for DAT (i.e., it is an inactive radiometabolite). Consistent with the rodent data, the apparent distribution volume in the cerebellum of both humans and nonhuman primates showed a continual increase at late times after injection, a result that may be attributed to entry of the radiometabolite into the brain. Thus, reference tissue modeling of 18F-FECNT will be prone to more errors than analysis with a measured arterial input function.  相似文献   
9.
Post-traumatic retinal detachment occurs frequently as a late consequence of progressive vitreous changes, especially following penetrating injuries. Occasionally, it develops soon after the trauma, without preceding proliferative vitreoretinopathy, is based on posterior vitreous detachment and morphologically resembles an idiopathic retinal detachment. It is possible that the posterior vitreous detachment in these cases is encouraged by the presence of intravitreal hemorrhage.  相似文献   
10.
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