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   1693篇
  免费   91篇
  国内免费   31篇
耳鼻咽喉   20篇
儿科学   27篇
妇产科学   28篇
基础医学   211篇
口腔科学   90篇
临床医学   145篇
内科学   601篇
皮肤病学   21篇
神经病学   80篇
特种医学   69篇
外科学   194篇
综合类   24篇
预防医学   107篇
眼科学   12篇
药学   125篇
中国医学   19篇
肿瘤学   42篇
  2023年   21篇
  2022年   22篇
  2021年   52篇
  2020年   33篇
  2019年   58篇
  2018年   48篇
  2017年   39篇
  2016年   45篇
  2015年   57篇
  2014年   68篇
  2013年   73篇
  2012年   111篇
  2011年   124篇
  2010年   66篇
  2009年   73篇
  2008年   105篇
  2007年   130篇
  2006年   81篇
  2005年   94篇
  2004年   94篇
  2003年   74篇
  2002年   46篇
  2001年   42篇
  2000年   42篇
  1999年   11篇
  1998年   20篇
  1997年   15篇
  1996年   7篇
  1995年   11篇
  1994年   7篇
  1993年   9篇
  1992年   7篇
  1991年   10篇
  1990年   6篇
  1989年   11篇
  1988年   13篇
  1987年   5篇
  1986年   6篇
  1985年   8篇
  1984年   9篇
  1983年   4篇
  1982年   5篇
  1979年   4篇
  1978年   6篇
  1977年   5篇
  1976年   6篇
  1975年   4篇
  1973年   3篇
  1970年   6篇
  1968年   3篇
排序方式: 共有1815条查询结果,搜索用时 15 毫秒
1.
CONTEXT AND OBJECTIVE: The safety and efficacy of drug-eluting stents reduce the need for surgical revascularization. The objective of the present study was to investigate whether paclitaxel or rapamycin-eluting stent are effective in avoiding the need for coronary-artery bypass grafting. METHODS: This was a systematic review of the literature using the methodology of the Cochrane Collaboration. The type of study considered was controlled randomized trials; the type of intervention was drug-eluting or bare-metal stents; and the main outcome investigated was coronary-artery bypass grafting. RESULTS: The ten studies included in this systematic review did not show any statistically significant difference between the drug-eluting stents and the bare-metal stents with regard to the outcome of coronary-artery bypass grafting (confidence interval: 0.31 to 1.42). CONCLUSION: The surgical revascularization rate was not reduced by the use of drug-eluting stents.  相似文献   
2.
Statistical analysis of 550 isolated maxillo-facial fractures is presented. Data obtained illustrated the important number of maxillo-facial fractures in Sao Paulo, the automobilistics accidents were responsible for most maxillo-facial trauma, the jaw and the malar were more predominant than the others structures and the conservative treatment was the most used one.  相似文献   
3.
The intravenous injection of rabbit anti-rat kidney serum in rats produces, with a latency of 30 to 60 seconds, the triad sinus bradycardia (or S-A blockade), systemic hypotension and apnea. Recordings of the intracardiac pressures showed a rise in the right and a simultaneous fall in the left ventricular pressure, 30 to 60 seconds after the serum injection. These initial effects were followed by pulmonary edema and death. Bilateral vagotomy prevented the bradycardia and apnea, but not the intracardiac changes, edema and death. Atropine also prevented the bradycardia, but not the apnea, edema and death. Experiments using alpha and beta adrenergic blocking agents seem to indicate that the edema is not caused by the release of catecholamines. It is suggested that the edema could be explained by a rise in the pulmonary capillary pressure, due to the antigen-antibody reaction. The triad bradycardia, systemic hypotension and apnea seems to be the first sign of the pulmonary edema, is reflex in nature, and is assumed to be due to stimulation of J receptors in the lungs, by a mechanical effect (edema). Phenylbutazone and acetylsalicylic acid give a partial protection against the pulmonary edema. Ultramorphological observations of lungs with edema were described.  相似文献   
4.
Fifty-one strains of Escherichia coli isolated from humans, swine, food, and water and identified as enterotoxinogenic by the Y-1 adrenal cell assay, were examined for heat-labile enterotoxin (LT) production by the passive immune hemolysis test. Cholera antitoxin, anti-choleragenoid and anti-LT were used as antisera. Cholera antitoxin was much more potent than anti-choleragenoid and LT antiserum in the detection of LT-positive strains. All strains isolated from pigs and sausage were negative in tests made with LT antiserum. A few strains isolated from humans, food, and water also gave negative results. These data showed that the passive immune hemolysis test is not as efficient as the Y-1 adrenal cell assay in the detection of enterotoxinogenic E. coli strains.  相似文献   
5.
6.
7.
The characteristics of trabecular bone in human fetuses at seven to nine months of intra-uterine life were studied in the vestibular surface of the mental and body portions of the mandible. In the mental portion, many circular trabeculae joined by "bridges" were observed in the alveolar region (AR). In the 8-month old fetus are trabeculae with tortuous disposition in the medium region (MR). Oblique trabeculae with superior and inferior dispositions defining a triangular area (future mental fossae) are verified in 9-month old fetuses. Trabeculae circularly disposed and vascular foramina are present close to the apex of this area. In the basilar region (BR) some trabeculae obliquely oriented are observed disposed near to the mandibular symphysis. The longitudinal bundles of collagen fibers assume an antero-posterior direction. At 9-month age the vascular foramina range from 6 to 20 microns and the osteocyte lacunae ranging from 1 to 4 microns diameter, are present in mandibles from all ages examined. In the body portion the presence of circular trabeculae joined by "bridges" is the main characteristic of the AR. In the MR most of the trabeculae are circular and the longitudinal trabeculae of this region assume an antero-posterior direction. The laminar, antero-posterior and juxtaposed trabeculae lying parallel to mandible base are a characteristic of the BR. The bundles of collagen fibers exhibit the same pattern of the trabeculae. The vascular foramina of the BR are smaller than that of the precedent regions. In the body portion of the mandible from all ages examined the osteocyte lacunae range from 1 to 4 microns in diameter.  相似文献   
8.
To assess the magnitude of discrepant results obtained by routine Haemophilus influenzae serotyping, 258 isolates, collected by the epidemiological surveillance system in Brazil from individuals with invasive diseases or carriage, were evaluated by two slide agglutination (SlAg) methods: SlAg method 1, by which strains were initially screened with a serotype b-specific antiserum, and SlAg method 2, by which strains were tested against all serotype-specific antisera in parallel. Investigators comparing results of the two SlAg methods with those obtained by capsule type-specific PCR were blinded to the method used. The serotype prevalence rates found by the three methods were significantly different, involving discrepancies mainly between serotype b and noncapsulated (NC) isolates. For invasive isolates (n = 131), the overall agreement rate between SlAg method 1 or 2 and PCR was 68.0 or 88.3%, respectively, whereas for colonizing isolates (n = 127) the corresponding rate was 46.5 or 94.2%, respectively. SlAg method 2 improved the ascertainment of serotypes over that obtained with SlAg method 1, demonstrating good correlation with PCR. Use of the polyvalent antiserum as a screening reagent for SlAg for invasive and colonizing isolates showed poor discriminatory power, with a sensitivity of 65.8% and a specificity of 91.7%. We stress the importance of using a well-standardized SlAg methodology and suggest that reference laboratories should utilize PCR routinely to confirm SlAg results and to check all nonspecific SlAg reactions and apparent NC isolates by SlAg in order to provide reliable data on the prevalence of H. influenzae serotypes in the H. influenzae type b vaccine era.  相似文献   
9.
OBJECTIVE: In the present work we studied the H1 and H2 histamine receptor expression and function in HBL-100 and MCF-10A cells, derived from non-tumorigenic human breast epithelia, and in MCF-10T, the H-ras-transfected MCF-10A counterpart. The signal transduction pathways associated with these receptors, and the expression of proto-oncogenes c-fos, c-myc and c-jun at the mRNA and protein levels, were examined. RESULTS: Saturation analysis using intact cells, showed two binding sites for [3H]tiotidine and [3H]mepyramine. Pretreatment of purified membrane with guanosine 5'-ythiotriphosphate resulted in the loss of the low affinity component for [3H]tiotidine binding, and of the high affinity component for [3H]mepyramine. In both cases, there was no modification in the total number of sites for both ligands. Neither H1 nor H2 agonists stimulated cyclic AMP production, though this pathway is functional in these cells. On the other hand, both H1 and H2 agonists enhanced phosphoinositide turnover in a dose-dependent fashion, and this induction is pertussis toxin-insensitive. H1 and H2 agonists did not influence the expression of c-myc or c-fos mRNA, nor their encoded proteins. CONCLUSIONS: These results indicate that the three cell lines examined showed functional H1 and H2 histamine receptors, which are involved in the metabolic turnover of inositol phosphates but are ineffective in the modulation of the cyclic AMP response. The fact that H2 receptors have lost their ability to stimulate cyclic AMP production would imply the loss of a regulatory mechanism of cell growth.  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