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   905540篇
  免费   62778篇
  国内免费   2348篇
耳鼻咽喉   12565篇
儿科学   28840篇
妇产科学   26246篇
基础医学   127361篇
口腔科学   24876篇
临床医学   75296篇
内科学   184308篇
皮肤病学   19105篇
神经病学   71912篇
特种医学   36591篇
外国民族医学   337篇
外科学   142914篇
综合类   19064篇
一般理论   247篇
预防医学   64988篇
眼科学   20206篇
药学   64188篇
中国医学   1823篇
肿瘤学   49799篇
  2018年   9275篇
  2017年   7313篇
  2016年   7830篇
  2015年   8903篇
  2014年   12608篇
  2013年   19488篇
  2012年   25988篇
  2011年   27639篇
  2010年   16792篇
  2009年   15961篇
  2008年   26423篇
  2007年   28018篇
  2006年   28162篇
  2005年   27702篇
  2004年   26527篇
  2003年   25678篇
  2002年   25259篇
  2001年   41503篇
  2000年   42727篇
  1999年   36388篇
  1998年   10024篇
  1997年   9196篇
  1996年   9118篇
  1995年   8486篇
  1994年   8120篇
  1993年   7627篇
  1992年   28290篇
  1991年   27068篇
  1990年   26485篇
  1989年   25435篇
  1988年   23610篇
  1987年   23232篇
  1986年   22304篇
  1985年   21198篇
  1984年   15857篇
  1983年   13505篇
  1982年   8118篇
  1979年   14622篇
  1978年   10224篇
  1977年   8649篇
  1976年   8170篇
  1975年   8967篇
  1974年   10716篇
  1973年   10198篇
  1972年   9677篇
  1971年   8940篇
  1970年   8597篇
  1969年   8033篇
  1968年   7697篇
  1967年   7094篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
994.
Ultrasensitive bright field in situ hybridization assays using enzyme metallography (EnzMet) have been developed and validated, but little is known regarding the applicability of EnzMet for immunophenotypic detection of protein via IHC. Superior resolution via discrete metallographic deposits offers the potential for enhancing high-resolution immunophenotyping. Using high-complexity tissue microarrays (TMAs), 88 common solid tumors were evaluated by automated EnzMet (Nanoprobes and Ventana). Targets were chosen to assess the ability of EnzMet to specifically localize encoded antigens in the nucleus (estrogen receptor), cytoplasm (cytokeratins), and cytoplasmic membrane (HER2) in TMAs. Results were compared with conventional IHC diaminobenzidine (DAB) immunostaining. There was full concordance between the EnzMet and conventional IHC results. Furthermore, the EnzMet reaction products did not appreciably diffuse, were dense and sharply defined, and provided excellent high-resolution differentiation of cellular compartments in paraffin sections for the nuclear, cytoplasmic, and cell membrane-localized antigens evaluated. The higher density of elemental silver deposited during enzyme metallography permitted evaluation of core immunophenotypes at a relatively low magnification, allowing more tissue to be screened in an efficient manner. This preliminary study shows the utility of using enzyme metallography for high-resolution immunophenotyping in TMAs.  相似文献   
995.
Brain morphology was examined using magnetic resonance imaging in 30 first-episode patients with a schizophreniclike psychosis, 15 chronic schizophrenics, and 20 neurological controls. Statistical analyses of computer-generated measurements of regions of interest were controlled for gender, age, social class, and total brain volume. Lateral ventricular size was increased in both first-episode and chronic schizophrenic patients, with greater significance on the left than on the right side. Only the chronic patients, however, had reduced temporal lobe size, which also was greater on the left side. No major correlations of regional brain morphological measurements with cognitive functioning were found, although some measurements of verbal memory were correlated with parahippocampal size. This is a report of a preliminary study that suggests that some morphological brain changes may be present at the time of first treatment for a psychotic illness, whereas others may occur later in the course of illness. Future prospective studies may determine the clinical significance of these changes and whether they progress with the development of illness chronicity.  相似文献   
996.
MCA, CA 15-3, CEA and CA 125 were determined in the serum of 49 patients with metastatic breast cancer and 38 patients with metastatic adenocarcinoma of other primary sites. By using the 99th percentile of the normal value distribution as the cut-off point, the positive predictive value (PV+) was found to be 85% (95% CI 76-94) for MCA, and 71% (95% CI 61-81) for CA 15-3. When receiver-operating-characteristic (ROC) curves were constructed, the PV+ for CA 15-3 was increased to 82% (95% CI 72-92), using 60 U ml-1 as the cut-off point. With the exception of two patients who had a slightly elevated MCA, MCA and CA 15-3 identified the same patients with breast cancer. By combining a positive MCA or CA 15-3 with a negative CEA and CA 125, further improvement of the PV+ could be achieved; 100% (95% CI 91-100). We conclude that MCA and CA 15-3 may play a useful role in discrimination between patients with metastatic breast cancer and those with adenocarcinoma of other primary sites.  相似文献   
997.
The tetracyclines in dermatology.   总被引:5,自引:0,他引:5  
Tetracycline is one of the most widely used antibiotics. It may share some properties with conventional immunosuppressive drugs and act as an anti-inflammatory agent in the treatment of inflammatory disease. This article reviews cutaneous diseases that have been treated with tetracyclines and their antiinflammatory and immunosuppressive properties.  相似文献   
998.
999.
Cultured brain cells from rat fetuses of ethanol-treated mothers demonstrated more than 2-fold elevations in choline acetyltransferase (ChAT) activity relative to those of control (saline-exposed) fetal brain cells. When cells from control animals were incubated in vitro for 5 days with 0.1% ethanol, ChAT activity was found to increase more than 4-fold. Brain cells from in utero ethanol-treated animals further exposed to ethanol in vitro for 5 days demonstrated significantly higher ChAT activity compared to cells exposed to ethanol only in vivo. These levels were more than 6 times greater than those of central nervous system cells never exposed to ethanol. Acetylcholinesterase (AChE) activity was significantly elevated (greater than 4-fold) in fetal brain cells when ethanol was present both in vivo and in vitro, but neither treatment alone resulted in any significant changes in AChE. These effects of ethanol on enzymes involved in acetylcholine metabolism may contribute to the different developmental neurologic abnormalities associated with fetal alcohol exposure.  相似文献   
1000.
Five years after treatment in a controlled trial, in which all had received self-exposure homework, a group of 40 agoraphobic outpatients retained marked improvement in agoraphobia, mood, and free-floating anxiety. Frequency of spontaneous panics decreased as much in those who had placebo and self-exposure as in those who received imipramine and self-exposure. Few patients, however, were completely well at 5 years and over half had received further treatment for agoraphobia during the follow-up. Patients who were still highly phobic at the end of the clinical trial were more often prescribed psychotropic medication during follow-up and remained phobic at 5 years. Phobic improvement had generalized more in those patients with very low than in those with moderate pretreatment Hamilton depression scores. Frequency of initial spontaneous panics did not predict outcome. Improvement in agoraphobia was associated with improved marital adjustment. Those who began with the best marital, work, and social adjustment were more improved in their phobias 5 years later.  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