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   2933506篇
  免费   220683篇
  国内免费   4860篇
耳鼻咽喉   41709篇
儿科学   92795篇
妇产科学   80231篇
基础医学   431749篇
口腔科学   82403篇
临床医学   263832篇
内科学   562479篇
皮肤病学   63839篇
神经病学   233240篇
特种医学   111680篇
外国民族医学   653篇
外科学   446152篇
综合类   66339篇
现状与发展   13篇
一般理论   1053篇
预防医学   230236篇
眼科学   69468篇
药学   219231篇
  9篇
中国医学   5807篇
肿瘤学   156131篇
  2018年   31725篇
  2017年   24092篇
  2016年   26871篇
  2015年   30515篇
  2014年   43269篇
  2013年   65190篇
  2012年   89460篇
  2011年   95005篇
  2010年   56319篇
  2009年   53151篇
  2008年   89448篇
  2007年   95692篇
  2006年   96284篇
  2005年   93698篇
  2004年   90144篇
  2003年   86920篇
  2002年   84072篇
  2001年   130137篇
  2000年   133413篇
  1999年   112431篇
  1998年   33196篇
  1997年   29371篇
  1996年   29447篇
  1995年   27794篇
  1994年   25829篇
  1993年   24337篇
  1992年   88778篇
  1991年   86929篇
  1990年   85015篇
  1989年   81877篇
  1988年   75711篇
  1987年   74228篇
  1986年   69739篇
  1985年   67168篇
  1984年   50592篇
  1983年   43163篇
  1982年   26141篇
  1981年   23681篇
  1979年   47864篇
  1978年   34328篇
  1977年   28622篇
  1976年   27261篇
  1975年   29392篇
  1974年   35657篇
  1973年   33958篇
  1972年   32070篇
  1971年   30160篇
  1970年   28099篇
  1969年   27012篇
  1968年   24598篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
Summary To evaluate the potential effect of androgens on the development and growth of human colorectal adenomas, the prevalence and concentration of cytosolic androgen receptors (AR) were analysed in 26 adenomas and 19 samples of normal colonic mucosa by a hybrid ligand receptor-binding assay. AR were detected in 7 of the adenomas (26.9%), and in 6 of the normal mucosa samples (31.6%). In the adenomas, AR levels demonstrated were low, ranging from 6 to 31 fmol/mg cytosol protein, and dissociation constants (Kds) ranged from 0.17–2.7x10-9 M. Of 13 adenomas excised from men, 6 (46%) had positive receptor activity, whereas only 1 of 13 (7.7%) from women was positive (P=0.03, Fisher's exact test). There was no correlation between AR titre and patient age, or between adenoma size and histological type or degree of dysplasia. In normal mucosa, AR levels ranged from 7 to 33 fmol/mg and Kds ranges from 0.24–3.1x10-9 M. There was no significant difference between either AR prevalence or levels in the adenomas and normal mucosa. The sex difference was exclusive to the adenoma. Endogenous androgen may play a role in adenoma development early in the promotional process.  相似文献   
982.
983.
Background: t(14; 18)/bcl-2 gene rearrangement (R) is claimedto impart a worse rate of complete remission and disease-freesurvival in diffuse large cell lymphoma (DLCL). DEL 6q has alsobeen associated with poor outcome. Design: Retrospective studyof 54 patients with either diffuse large cell or immunoblasticlymphoma who had cytogenetics and/or molecular studies performed.Results: Patient characteristics, complete remission rate, andtime to treatment failure (TTF) were similar at three year follow-upfor groups with and without t(14; 18)/BCL-2R Survival was worsefor the former but the difference was not statistically significant.For DEL 6q, patient characteristics and survival rates weresimilar at three year follow-up for patients with and withoutthe abnormality. TTF was worse for the former but this was notstatistically significant. Conclusion: This study, with equalor greater number of patients with t(14; 18) than previous reports,fails to show a worse prognosis for patients with the t(14;18) chromosomal abnormality. A definite association will awaitfurther accrual of patients and a meaningul multivariate analysis. lymphoma, BCL-2, cytogenetics, DEL 6q  相似文献   
984.
The prevalence of heavy alcohol consumption is a major problem of increasing proportions throughout the world. Although alcohol sensitizing drugs and more recently serotonin uptake inhibitors are drug interventions with some following, their long term beneficial consequences have yet to be demonstrated. In recent years, we have demonstrated that manipulating activity in the renin-angiotensin system will dramatically alter voluntary alcohol consumption in rats. Based on these findings, the present study evaluated the ability of a class of drugs known as the angiotensin converting enzyme inhibitors to reduce voluntary alcohol drinking in laboratory animals. These drugs prevent the conversion of angiotensin I to angiotensin II. They have been licensed for use in Europe and North America and are indicated in the treatment of hypertension. Our experiments showed that both captopril (Capoten, Squibb) and enalapril (Vasotec, Merck Sharpe & Dohme) can reduce alcohol drinking in both normotensive and hypertensive animals regardless of whether the pattern of intake is in a bout or of a less exaggerated nature. Furthermore, this change in alcohol intake can occur without concomitant changes in blood pressure, plasma renin activity, overall fluid balance, or the distribution and metabolism of alcohol. Taken together these findings suggest that the angiotensin converting enzyme inhibitors should be evaluated in a clinical setting for they may prove to be a useful new treatment or treatment adjunct for alcohol abuse in humans.  相似文献   
985.
986.
A prospective randomized study was done to compare the fluid contamination rates of two methods used to determine cardiac output by thermodilution under in-use conditions. Fifty patients were randomly assigned to have cardiac output measured by the capped syringe or closed loop method, and were followed with quantitative cultures of fluid and catheter. The two treatment groups (n = 25 each) were comparable in terms of age, sex, intensive care unit location, underlying diagnosis, and mean number of cardiac output determinations performed in the first 24 hours after placement of the catheter line. No differences in the rates of fluid contamination were seen at any time between the two groups. The overall fluid contamination rate was 2/124 cultures (1.8% with 95% confidence interval +/- 4.1%) with one colony of Staphylococcus epidermidis from a closed loop sample and one colony of Pseudomonas maltophilia in a capped syringe sample. Although no difference in contamination rates was documented, the closed loop system required less nursing time and effort.  相似文献   
987.
Hypomagnesemia is not an infrequent finding in diuretic-induced hypokalemia. Potassium replacement therapy in these cases may be ineffective in raising serum potassium levels unless normal magnesium concentrations are restored.  相似文献   
988.
989.
Endocarditis due to Kingella species   总被引:1,自引:0,他引:1  
  相似文献   
990.
Using indirect immunohistochemistry and an antiserum raised against rat corticotrophin-releasing factor (CRF) we have outlined an asymmetric network of cells and varicose fibers in sheep adrenal cortex. This network was not associated with the larger splanchnic nerves, but was occasionally found in small bundles or with blood vessels; in most instances fibers were found weaving independently through cortical parenchyma. A plexus of fibers was found in the zona reticularis, with a few fibers ramifying into adjacent medulla. Uni or bipolar cells were found throughout the cortex, with the greatest frequency at the corticomedullary junction; a multipolar-type cell was also found in this area. Staining of varicose structures and most cells was abolished by incubation with excess rat CRF 1-41, but not by ovine CRF or a range of other peptides. Though the immunoreactive species has not as yet been identified, it may thus share homology with sequences present in rat but not ovine CRF.  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