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   1083717篇
  免费   72416篇
  国内免费   1397篇
耳鼻咽喉   15186篇
儿科学   34977篇
妇产科学   28832篇
基础医学   154688篇
口腔科学   29709篇
临床医学   95738篇
内科学   205276篇
皮肤病学   24564篇
神经病学   82411篇
特种医学   43213篇
外国民族医学   201篇
外科学   164307篇
综合类   21820篇
现状与发展   1篇
一般理论   274篇
预防医学   75299篇
眼科学   24721篇
药学   86758篇
  7篇
中国医学   2815篇
肿瘤学   66733篇
  2019年   7967篇
  2018年   11542篇
  2017年   9127篇
  2016年   10339篇
  2015年   11513篇
  2014年   15593篇
  2013年   22640篇
  2012年   31183篇
  2011年   32822篇
  2010年   19303篇
  2009年   18091篇
  2008年   30367篇
  2007年   32523篇
  2006年   33136篇
  2005年   31423篇
  2004年   30117篇
  2003年   28916篇
  2002年   27880篇
  2001年   60168篇
  2000年   61608篇
  1999年   51104篇
  1998年   12522篇
  1997年   11068篇
  1996年   11079篇
  1995年   10379篇
  1994年   9384篇
  1993年   8902篇
  1992年   37893篇
  1991年   36360篇
  1990年   35815篇
  1989年   34369篇
  1988年   30946篇
  1987年   30068篇
  1986年   28288篇
  1985年   26544篇
  1984年   19248篇
  1983年   16178篇
  1982年   8878篇
  1979年   17125篇
  1978年   11448篇
  1977年   10272篇
  1976年   8871篇
  1975年   10106篇
  1974年   11693篇
  1973年   11314篇
  1972年   10810篇
  1971年   10121篇
  1970年   9290篇
  1969年   8965篇
  1968年   7938篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Norethisterone enanthate (NET-En), an established intramuscular long-acting contraceptive agent, has previously been shown to be effective in inhibiting fertility in two rodent species even 4 days after oral ingestion. Pharmacokinetics of NET and NET-En were studied after oral and intramuscular doses in two animal species and a few women. The results suggest that the NET-En was absorbed within a day in all the species after oral dose. The estimates of relative bioavailability ranged from 13 to 51% in rabbits, monkeys, and women. The elimination half-life was 5–10 days. The presence of the active component, NET, in the circulation over the experimental period of 15 days suggests that NET-En could be useful as a long-acting oral pill. The suppression of progesterone levels during the luteal phase of menstrual cycle in women also supports this finding.  相似文献   
993.
The effects of lentinan on peripheral blood mononuclear cell (PBMC) expression of IL-2 receptor in patients with chronic hepatitis B in vitro and in vivo were studied. The expression percentage of IL-2 receptor in 44 patients with chronic hepatitis before treatment was 36.74 +/- 7.74, which was lower than healthy subjects, and was 48.92 +/- 3.79 after 2 months treatment of lentinan, which was approximated the normal control. PBMC from 30 patients with chronic hepatitis B were cultured in vitro with or without lentinan. The percentage of expression IL-2 receptor was 12.81 +/- 2.62 without lentinan and was 35.70 +/- 4.87 in the presence of lentinan. The concentration of lentinan stimulating expression of IL-2 receptor was between 0.2 to 200 g.ml-1. The results suggest that lentinan stimulates expression of IL-2 receptor on PBMC, which is associated with the therapeutic effectiveness of lentinan treatment.  相似文献   
994.
995.
996.
Species-level identification of Acanthamoeba isolates is difficult and gives little or no indication of the isolate's pathogenicity. We identified two amplification-based genetic markers that were highly correlated with pathogenicity in Acanthamoeba spp. One marker, designed to amplify a 485-bp fragment of the small-subunit ribosomal RNA gene (ssrDNA), was preferentially amplified from the nonpathogenic strains; amplifications from the pathogenic strains yielded anomalous fragments of 650 and 900?bp. A second marker was developed on the basis of the anomalous 650-bp fragment. Primers to this sequence preferentially amplified a noncoding locus (called Ac6) only from the pathogenic strains. These two genetic markers may be useful for identification of pathogenic Acanthamoeba spp. strains.  相似文献   
997.
 Rhabdomyosarcoma (RMS) is occasionally found in the female genital tract, and mostly appears as one of the heterologous mesenchymal components in uterine carcinosarcoma designated as malignant mixed müllerian tumour (MMMT). We examined the biological properties of a pure rhabdomyosarcoma (RMS) cell line designated FU-MMT-3, which was newly established from a surgical specimen taken from a patient with uterine MMMT. We also evaluated c-myc and MYCN gene amplification in three RMS cell lines (including FU-MMT-3) derived from three MMMTs by Southern blot analysis. FU-MMT-3 cells were propagated continuously for 57 serial passages over a 2-year period in vitro. FU-MMT-3 was able to produce tumours demonstrating pure RMS in athymic nude mice. Cytogenetically, FU-MMT-3 showed a triploidy pattern, with complex karyotypic abnormalities including trisomy of chromosome 8. All three RMS cell lines, including FU-MMT-3, showed amplification of the c-myc gene (approximately fourfold to eightfold), while no cell lines demonstrated MYCN gene amplification. FU-MMT-3 is considered to provide a useful system for the study of the biological behaviour of RMS in MMMTs. Extra copies of chromosome 8 and c-myc gene amplification may be associated with the rhabdomyoblastic differentiation in MMMT. Received: 7 January 1997 / Accepted: 2 May 1997  相似文献   
998.
999.
1000.
A foregut cyst is formed as a result of abnormal budding and pinching of the tracheobronchial tree when bronchial buds develop to form the primitive respiratory tree. Foregut cysts are clinically classified as bronchogenic, esophageal, enterogastric, or ciliated hepatic. We present a foregut cyst that occurred in the retroperitoneum and was difficult to distinguish from other retroperitoneal cystic mass lesions. Magnetic resonance imaging was useful in revealing the cyst's continuity to adjacent organs. Received: 19 June 1995/Accepted: 23 July 1995  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