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   778篇
  免费   43篇
  国内免费   11篇
耳鼻咽喉   2篇
儿科学   5篇
妇产科学   18篇
基础医学   145篇
口腔科学   13篇
临床医学   157篇
内科学   141篇
皮肤病学   10篇
神经病学   71篇
特种医学   13篇
外科学   133篇
综合类   9篇
预防医学   17篇
眼科学   3篇
药学   41篇
肿瘤学   54篇
  2023年   4篇
  2022年   4篇
  2021年   12篇
  2020年   5篇
  2019年   14篇
  2018年   17篇
  2017年   13篇
  2016年   13篇
  2015年   21篇
  2014年   26篇
  2013年   33篇
  2012年   65篇
  2011年   55篇
  2010年   22篇
  2009年   27篇
  2008年   51篇
  2007年   33篇
  2006年   52篇
  2005年   43篇
  2004年   29篇
  2003年   24篇
  2002年   27篇
  2001年   29篇
  2000年   31篇
  1999年   25篇
  1998年   5篇
  1997年   6篇
  1996年   7篇
  1995年   7篇
  1994年   11篇
  1993年   3篇
  1992年   12篇
  1991年   8篇
  1990年   6篇
  1989年   9篇
  1988年   9篇
  1986年   5篇
  1985年   5篇
  1984年   7篇
  1983年   4篇
  1980年   3篇
  1979年   5篇
  1977年   2篇
  1976年   4篇
  1975年   4篇
  1974年   8篇
  1973年   3篇
  1972年   6篇
  1971年   6篇
  1970年   6篇
排序方式: 共有832条查询结果,搜索用时 140 毫秒
1.

Background  

Antiphospholipid syndrome (APS) has been often associated to RPL since 1980 and some reports in the Literature rarely described antibodies to factor XII in patients with APS.  相似文献   
2.
In the present study, the primary tumor angiogenesis characteristics of 81 stage IV previously untreated breast cancers with synchronous metastasis to different distant sites (10 patients with soft tissue metastases, 31 with bone metastases, and 40 with visceral metastases) were analyzed. The primary intratumor microvessel density was assessed by immunohistochemical assay on paraffin-embedded primary tumor samples, using a monoclonal anti-CD34 antibody. The mean primary intratumor microvessel density (at 400× fields) was 78±39 (SD) microvessels per field. The microvessel density was not significantly related to the main clinical/pathological features of the tumor (age, cytohistological grade, DNA ploidy, diameter, and receptor status). The percentage of tumor cases with high primary intratumor microvessel density (cut-off median value of the series 73±39 microvessels/field) did not significantly differ in patients with bone, soft tissue, or visceral metastatic disease. Aanalysis of clinical outcome showed a significantly shorter time to progression and overall survival for patients with visceral metastases (P<0.001 and P<0.0002 by log-rank, respectively). Presence of visceral metastases was confirmed to be the only independent prognostic factor related to a worse TTP (hazard risk 2.15, 95% confidence interval 1.14–4.03, P<0.02) and overall survival (hazard risk 1.81, 95% confidence interval 0.98–3.35, P<0.06) by multivariate analysis. In conclusion, the assessment of neoangiogenesis of primary breast cancer by CD34 expression does not provide information predictive of different distant sites of metastasis. Received: 15 June 2001 / Accepted: 12 September 2001  相似文献   
3.
The thermal dilution method offers a number of advantages in the measurement of cardiac output particularly when measurements at frequent intervals over prolonged periods are required. The sources of error in the quantification of thermal indicator input and other factors pertinent to the applicability of this method to serial measurements in an automated clinical environment are discussed.  相似文献   
4.
Oocyte morphology predicts outcome of intracytoplasmic sperm injection   总被引:10,自引:14,他引:10  
To examine the influence of cytoplasmic morphology on the success rate of intracytoplasmic sperm injection (ICSI), the morphology of 837 metaphase II oocytes was assessed after cumulus stripping. The main abnormalities detected were excessive granularity, cytoplasmic inclusions such as vacuoles, smooth endoplasmic reticulum clustering and refractile bodies. Microinjection was performed in 538 oocytes with normal cytoplasm, 142 out of 161 with excessive granularity and 112 out of 138 with cytoplasmic inclusions. Very poor oocytes were not injected. No difference was found in fertilization rate. The embryos achieved cleaved normally and a similar number of good quality embryos among the three groups was noted. The outcome of transfer of embryos derived solely from normal oocytes (group A: 72 patients, 183 embryos) was compared with those from oocytes with cytoplasmic abnormalities (group B: 34 patients, 85 embryos). In group A, 17 clinical pregnancies (24% per patient, implantation rate 10%) were established. In group B, only one clinical pregnancy (3% per patient, implantation rate 1%) was established, from the transfer of embryos derived from oocytes with homogeneous granularity of the cytoplasm. No pregnancy resulted following the transfer of embryos from eggs with cytoplasmic inclusions. The difference was statistically significant. The outcome of ICSI is dependent on the quality of the oocytes retrieved. Normal fertilization and early embryo development were achieved in oocytes with abnormal cytoplasm morphology, but the resulting embryos failed to demonstrate the same implantation potential as those derived from oocytes with normal cytoplasm.   相似文献   
5.
6.
Detection of T suppressor cells in patients with organ allografts   总被引:16,自引:0,他引:16  
Specific immunosuppression of host's immune response to donor HLA antigens has been a major goal to clinical transplantation. Recent evidence has been accumulating to show that a distinct population of T cells expressing the CD8(+) CD28(-) phenotype display suppressor function and inhibit Th activation and proliferation by modulating the APC function. To assess the presence of Ts in transplant recipient's circulation, we have developed a flow cytometry method that measures the expression of costimulatory molecules on donor APC exposed to recipient Th and Ts. Our results demonstrate that quantitation of the capacity of CD8(+) CD28(-) T cells from patient circulation to suppress the activation of costimulatory molecules (CD80, CD86) on donor APC offers a reliable tool for monitoring specific immunosuppression against the graft in solid organ transplantation.  相似文献   
7.
8.
9.
Experimental studies have demonstrated that the GABAergic system modulates acetylcholine release and, through GABAA receptors, tonically inhibits cholinergic activity. Little is known about the effects of GABA on the cholinergic activity in the human central nervous system. In vivo evaluation of some cholinergic circuits of the human brain has recently been introduced using a transcranial magnetic stimulation (TMS) protocol based on coupling peripheral nerve stimulation with TMS of the motor cortex. Peripheral nerve inputs have an inhibitory effect on motor cortex excitability at short intervals (short latency afferent inhibition, SAI). We investigated whether GABAA activity enhancement by lorazepam modifies SAI. We also evaluated the effects produced by lorazepam on a different TMS protocol of cortical inhibition, the short interval intracortical inhibition (SICI), which is believed to be directly related to GABAA activity. In 10 healthy volunteers, the effects of lorazepam were compared with those produced by quetiapine, a psychotropic drug with sedative effects with no appreciable affinity at cholinergic muscarinic and benzodiazepine receptors, and with those of a placebo using a randomized double-blind study design. Administration of lorazepam produced a significant increase in SICI  ( F 3,9= 3.19, P = 0.039)  . In contrast to SICI, SAI was significantly reduced by lorazepam  ( F 3,9= 9.39, P = 0.0002)  . Our findings demonstrate that GABAA activity enhancement determines a suppression of SAI and an increase of SICI.  相似文献   
10.
Our studies on the formation of Sindbis virus proteins have established that: 1. one of the two envelope proteins (E2) accumulates in infected cells as a higher molecular weight precursor that is slowly converted to the virion protein; 2. the large protein (mol. wt 130000 daltons), that accumulates in cells infected with a temperature-sensitive mutant of Sindbis virus contains sequences of the three virion proteins; and 3. the protein (mol. wt. 100000 daltons) isolated from BHK cells infected with Sindbis virus is related in sequence to the two envelope proteins.We have investigated the formation of defective-interfering (DI) particles of Sindbis virus and their ability to inhibit the replication of standard virus. BHK cells infected with passages of Sindbis virus containing DI particles accumulate a species of RNA (20S) that is about half the molecular weight of the 26S RNA. We have demonstrated by competitive hybridization experiments that 20S RNA contains half the sequences of 26S RNA. We also present evidence that in contrast to 26S RNA, 20S does not bind to polysomesin vivo and is not translatedin vitro.Presented on the Meeting on Studies on Virus Replication of the Commission of the European Communities in Brüssel, May 1974.  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