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   4428篇
  免费   201篇
  国内免费   22篇
耳鼻咽喉   36篇
儿科学   46篇
妇产科学   69篇
基础医学   515篇
口腔科学   49篇
临床医学   247篇
内科学   1133篇
皮肤病学   44篇
神经病学   359篇
特种医学   111篇
外科学   945篇
综合类   15篇
一般理论   1篇
预防医学   61篇
眼科学   185篇
药学   358篇
中国医学   10篇
肿瘤学   467篇
  2023年   31篇
  2022年   48篇
  2021年   107篇
  2020年   48篇
  2019年   62篇
  2018年   89篇
  2017年   64篇
  2016年   82篇
  2015年   105篇
  2014年   120篇
  2013年   142篇
  2012年   244篇
  2011年   255篇
  2010年   154篇
  2009年   128篇
  2008年   267篇
  2007年   271篇
  2006年   256篇
  2005年   253篇
  2004年   233篇
  2003年   243篇
  2002年   227篇
  2001年   96篇
  2000年   107篇
  1999年   121篇
  1998年   68篇
  1997年   62篇
  1996年   52篇
  1995年   38篇
  1994年   43篇
  1993年   36篇
  1992年   59篇
  1991年   54篇
  1990年   33篇
  1989年   42篇
  1988年   38篇
  1987年   31篇
  1986年   44篇
  1985年   30篇
  1984年   22篇
  1983年   19篇
  1982年   25篇
  1981年   13篇
  1979年   25篇
  1977年   13篇
  1976年   13篇
  1975年   13篇
  1972年   14篇
  1971年   12篇
  1968年   19篇
排序方式: 共有4651条查询结果,搜索用时 15 毫秒
21.
22.
Summary The histological grades of prostatic carcinoma, as defined by Gleason, were correlated with three methods of morphometry in 254 step-sectioned prostates obtained at autopsy. The variables studied were 1) the number of tumours in each prostate; 2) bilaterality and 3) tumour volume. Each characteristic yielded a statistically significant correlation with histological grade. The strongest correlations were obtained using tumour volume. These autopsy studied help to explain the inconsistent results obtained from morphometric analyses of surgical material, and lend support to the Gleason system as a means of predicting tumour behavior.Supported in part by research contracts PH 64-10, NCI-72-3213, N01-CP-53521; Grant R01-CA-33644; and the Grant-in-Aid for Cancer Research (33) from the Ministry of Health and Welfare  相似文献   
23.
This paper presents clinical observations/results of the application of an alternate method to traditional conservative management of subluxations and dislocations of the glenohumeral joint on major junior hockey players. The proposed program involves three stages: 1) rest and nutrition, 2) interferential current and faradic muscle stimulation, and 3) a traditional progressive-resistance weight-training program in conjunction with a specially designed orthosis. Current scientific theory on soft tissue healing and repair is reviewed as the backdrop to the proposed regimen. The resulting 100% success rate is compared to the success rate of conventional conservative therapeutic programs. The orthosis is a potentially useful therapeutic device permitting safe ranges of shoulder movement during the healing process, but scientific investigation is needed to determine the precise effect of the orthosis within the proposed therapy program.  相似文献   
24.
Helicobacter pylori can produce a persistent infection in the human stomach, where chronic and active inflammation, including the infiltration of phagocytes such as neutrophils and monocytes, is induced. H. pylori may have a defense system against the antimicrobial actions of phagocytes. We studied the defense mechanism of H. pylori against host-derived peroxynitrite (ONOO(-)), a bactericidal metabolite of nitric oxide, focusing on the role of H. pylori urease, which produces CO(2) and NH(3) from urea and is known to be an essential factor for colonization. The viability of H. pylori decreased in a time-dependent manner with continuous exposure to 1 microM ONOO(-), i.e., 0.2% of the initial bacteria remained after a 5-min treatment without urea. The bactericidal action of ONOO(-) against H. pylori was significantly attenuated by the addition of 10 mM urea, the substrate for urease, whereas ONOO(-)-induced killing of a urease-deficient mutant of H. pylori or Campylobacter jejuni, another microaerophilic bacterium lacking urease, was not affected by the addition of urea. Such a protective effect of urea was potentiated by supplementation with exogenous urease, and it was almost completely nullified by 10 microM flurofamide, a specific inhibitor of urease. The bactericidal action of ONOO(-) was also suppressed by the addition of 20 mM NaHCO(3) but not by the addition of 20 mM NH(3). In addition, the nitration of L-tyrosine of H. pylori after treatment with ONOO(-) was significantly reduced by the addition of urea or NaHCO(3), as assessed by high-performance liquid chromatography with electrochemical detection. These results suggest that H. pylori-associated urease functions to produce a potent ONOO(-) scavenger, CO(2)/HCO(3)(-), that defends the bacteria from ONOO(-) cytotoxicity. The protective effect of urease may thus facilitate sustained bacterial colonization in the infected gastric mucosa.  相似文献   
25.
Recent progress in molecular and cellular biology has led to the development of numerous effective cardiovascular drugs. However, there are still a number of diseases for which no known effective therapy exists, such as peripheral arterial disease, ischaemic heart disease, restenosis after angioplasty, and vascular bypass graft occlusion. Currently, gene therapy is emerging as a potential strategy for the treatment of cardiovascular disease despite its limitations. The first human trial in gene therapy for cardiovascular disease was started at 1994 to treat peripheral vascular disease using vascular endothelial growth factor (VEGF). Then, many different potent angiogenic growth factors were tested in clinical trials to treat peripheral arterial disease and ischaemic heart disease. Improvement of clinical symptoms in peripheral arterial disease and ischaemic heart disease has been reported. This review focuses on the future potential of gene therapy for the treatment of cardiovascular disease. In the future, gene therapy might become a real pharmacotherapy to treat cardiovascular disease.  相似文献   
26.
A neural network-based similarity index for clustering DNA microarray data   总被引:3,自引:0,他引:3  
A common approach to the analysis of gene expression data is to define clusters of genes that have similar expression. A critical step in cluster analysis is the determination of similarity between the expression levels of two genes. We introduce a neural network-based similarity index as a non-linear similarity index and compare the results with other proximity measures for Saccharomyces cerevisiae gene expression data. We show that the clusters obtained using Euclidean distance, correlation coefficients, and mutual information were not significantly different. The clusters formed with the neural network-based index were more in agreement with those defined by functional categories and common regulatory motifs.  相似文献   
27.
Epithelial neoplasms of appendix are infrequent, and their pathological features are not fully characterized. We collected 33 cases of appendiceal tumors and examined immunohistochemically the expression of cytokeratins (CK, CK7, and CK20), mucin core protein (MUC1, MUC2, MUC5AC, and MUC6), E-cadherin, chromogranin A, and p53 protein. Gene analysis of TP53 was also conducted on exons 5 to 8. Clinically, mucinous tumors were predominant in females. Immunohistochemically, all the tumors expressed CK20, whereas CK7 was positive in one third of the cases. Similarly, MUC2 was expressed in all the tumors, whereas MUC1 and MUC5AC were detected in about a half of the cases. Although chromogranin A-positive cells are generally sparse in normal appendix, they were more common in mucinous tumors than in nonmucinous tumors. Contrary to the previous data reported (Mod Pathol 2002;15:599-605), mucinous carcinoma exhibited a higher frequency of p53-positive cells (mean 29%) compared with mucinous adenoma (2.8%) (P < .001), whereas nonmucinous tumors showed high levels of p53-positive cells to similar extent (51%-67%) in both adenoma and carcinoma. The high expression of p53 protein coincided with the presence of mutations in multiple sites of TP53 gene in mucinous tumors. This is the first report that characterized the immunophenotypic profile of appendiceal epithelial neoplasms with an emphasis of a higher frequency of p53 positivity in mucinous carcinoma cases compared with mucinous adenoma in the appendix.  相似文献   
28.
29.
Action of strychnine to cortical neurons   总被引:1,自引:0,他引:1  
  相似文献   
30.
Summary Effect of chronic clonidine treatment on the response to glucose of rat pancreatic B-cells was investigated. Clonidine treatment was carried out for 10 days by dissolving the drug into drinking water at a concentration of 10 g/ml. Control rats were given drug-free tap water. Serum insulin responses to glucose (750 mg/kg, i. v.) of clonidinetreated rats were much smaller than those of control rats. However, after 1 day's withdrawal of clonidine, the rise in the serum insulin level induced by glucose was approximately 2-fold larger in clonidine-treated rats as compared to that in control rats. Since clonidine treatment decreased body weight of the rat by 10%–20% in 10 days, the same experiments were carried out with rats whose body weight loss was made comparable to that of clonidine-treated rats by restricting food for 10 days. Then, some animals of the group thus treated had food-restriction discontinued for 1 day. In both of the above two groups, no increment in glucoseinduced rise in serum insulin level was observed. Islets of Langerhans isolated from clonidine-treated rats showed pronounced insulin releasing capacity in response to glucose. Insulin content per islet of the clonidine-treated rat was slightly larger than that of control rat. These results indicate that the enhancement of serum insulin response to glucose following clonidine treatment is mainly attributable to the hyper-responsiveness developed in the pancreatic B-cells.  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