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   192347篇
  免费   3888篇
  国内免费   433篇
耳鼻咽喉   2746篇
儿科学   7382篇
妇产科学   5825篇
基础医学   24835篇
口腔科学   5723篇
临床医学   14971篇
内科学   34517篇
皮肤病学   4469篇
神经病学   11404篇
特种医学   10559篇
外国民族医学   97篇
外科学   28894篇
综合类   1078篇
一般理论   1篇
预防医学   16130篇
眼科学   4269篇
药学   13345篇
  2篇
中国医学   135篇
肿瘤学   10286篇
  2018年   3462篇
  2017年   3836篇
  2016年   3119篇
  2015年   4794篇
  2014年   4201篇
  2013年   3271篇
  2012年   9644篇
  2011年   4519篇
  2010年   2080篇
  2009年   3761篇
  2008年   1905篇
  2007年   2624篇
  2006年   2883篇
  2005年   11021篇
  2004年   12508篇
  2003年   8089篇
  2002年   3322篇
  2001年   4301篇
  2000年   1660篇
  1999年   5810篇
  1998年   498篇
  1995年   368篇
  1992年   6852篇
  1991年   7088篇
  1990年   7335篇
  1989年   6935篇
  1988年   6461篇
  1987年   6227篇
  1986年   5946篇
  1985年   5235篇
  1984年   3585篇
  1983年   2908篇
  1982年   999篇
  1981年   765篇
  1980年   835篇
  1979年   3827篇
  1978年   2361篇
  1977年   1781篇
  1976年   1559篇
  1975年   2473篇
  1974年   3105篇
  1973年   2738篇
  1972年   2756篇
  1971年   2741篇
  1970年   2555篇
  1969年   2464篇
  1968年   2237篇
  1967年   2163篇
  1966年   1898篇
  1965年   1131篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
The experimental infection of immunocompetent and immunodeficient athymic mice with an avirulent encephalitogenic Toxoplasma strain (DX strain) was employed to study the ensuing encephalitic process by use of histological and immunocytochemical methods. In the acute phase of the infection Toxoplasma cysts and tachyzoites were accompanied by an infiltrate composed of macrophages, CD4+ and CD8+ T cells. In the chronic stage a granulomatous encephalitis developed. In contrast to immunocompetent NMRI mice, athymic nude NMRI mice died 3 weeks post-infection because of a generalized toxoplasmosis with predominant involvement of the brain. A salient feature of murine Toxoplasma encephalitis was up-regulation of class I and II major histocompatibility complex (MHC) gene products. Class I antigen was widely expressed on microglial cells and astrocytes. Class II antigen was only expressed on microglial cells despite a considerable astrogliosis. Our results indicate a differential expression of MHC-determined antigens on brain cells in acute and chronic murine Toxoplasma encephalitis.  相似文献   
92.
Total gastrectomy is discussed as the operation of choice among different surgical approaches for gastric carcinoma. We prefer the performance of an elective total gastrectomy with systematic lymphadenectomy (compartments I and II) and obligatory splenectomy. A retrospective study of 1,704 consecutive cases of gastric carcinomas showed a better outcome following total gastrectomy in relationship to distal subtotal gastrectomy, but these results cannot be used as evidence because of the lack of a prospective study. Nevertheless, a precise analysis of our cases in regard to tumor site and tumor type could show a frequency of only 6% to maximally 30%, in which elective total gastrectomy may represent a procedure too extensive to justify for an oncological course.  相似文献   
93.
The alkylating agent ifosfamide synthesized according to own method at the Institute of Pharmaceutical Industry, Warsaw, was compared in biological evaluations with Holoxan (Asta-Werke's ifosfamide). No significant differences between tested compounds were found in respect of acute toxicity and antitumor activity in experimental systems in mice.  相似文献   
94.
95.
96.
97.
A retrospective study of 232 bladder tumours with minimum follow-up 5 years is presented. The carcinoma was superficial in 66%, muscle-invasive in 31% and could not be staged in 3%. Primary treatment was mainly transurethral resection for superficial tumour, but was cystectomy or radiotherapy in 22 of 29 T1 G3. Of the superficial tumours, 71% recurred. Progression to higher T stage occurred in 15% of Ta and 29% of T1 tumours, and half of these patients died of bladder cancer. The corrected 5-year survival rates in grades 1, 2A, 2B and 3-4 were 96, 84, 64 and 43%, and in stages Ta, T1, T2 and T3 they were 94, 69, 40 and 31%. All patients with T4 tumour died within 4 years. Among the 45 patients with 40 Gy irradiation + cystectomy, the corrected 5-year survival rate was 83% in superficial and 64% in muscle-invasive tumours, and among the 38 with radical radiotherapy the rates in T1-3 were 46, 36 and 13%. Transurethral resection was successful in most Ta cases. Most T1 tumours were, like T2-4, of higher grade than Ta. Prognosis was worse in T1 than in Ta. After progression to muscle-invasive disease, even during close follow-up the outlook was poor, as poor as for patients with primary muscle-invasive disease.  相似文献   
98.
(E)-5-(2-Bromovinyl)-2'-deoxyuridine (1; BrVUdR) inhibits the replication of herpes simplex virus type 1 (HSV-1) and of varicella-zoster virus (VZV) in vitro at concentrations of 0.01 to 0.23 mumol/l, whereas herpes simplex virus type 2 (HSV-2) is influenced only at 5.5 to 27 mumol/l. In comparison to some classical and newly developed antiherpetics, i. e. 5-iodo-2'-desoxyuridine (2; idoxuridine, IDU), 9-beta-D-arabinofuranosyladenine (4; vidarabine Ara-A), 9-(2-hydroxyethoxymethyl) guanine (5; acyclovir, ACV) and 2'-fluoro-5-iodo-1-beta-D-aracytosine (6;FIAC) the following order of decreasing activity was found:1 greater than 6 greater than 5 greater than 2 greater than 4 (against HSV-1) and 6 greater than 2 greater than 5 greater than 1 greater than 4 (against HSV-2). The high selectivity of the antiviral effect of BrVUdR towards HSV-1 and TZV is based on the fact, that proliferation of different mammalian cell lines is inhibited by 50% only at concentrations as high as 90 to 170 mumol/l, resulting in a therapeutical index of 1000 to 10,000. Successful treatment of an HSV-1 encephalitis in mice as well as an HSV-1 keratitis of rabbits confirmed the efficiency of 1 in experimental animal infections. No toxic side effects in both local and systemic applications were observed. Promising data from cell culture and animal experiments recommend 1 as a potential candidate for the local and systemic treatment of HSV-1 and VZV infections in man.  相似文献   
99.
This content was analysed in patients with chronic periodontitis and in control subjects. In periodontal disease, it was characterized by higher mean concentrations of glycine, proline, tyrosine and delta-aminovaleric acid than in controls (p less than 0.001). However, the range of values varied considerably in the two groups. There were differences between periodontitis and control samples in the proportions of proline to serine (p less than 0.01) and proline to glutamic acid and glutamine (p less than 0.05). Bacterial contamination and decomposition of salivary proteins is responsible for the elevated salivary levels of glycine, proline, tyrosine and delta-aminovaleric acid in the periodontal group.  相似文献   
100.
A significant increase of LDL-apolipoprotein B by 13% and LDL-cholesterol by 19% was observed in a group of 9 patients with hyperlipoproteinaemia Type III after bezafibrate treatment. Additional administration of colestipol caused a significant decrease of both LDL-apolipoprotein B by 18% and LDL-cholesterol by 25%. In 10 patients of hyperlipoproteinaemia Type IIb a significant decrease of both LDL-apolipoprotein B by 28% and LDL-apolipoprotein B by 18% was observed after bezafibrate therapy. When bezafibrate was given together with colestipol a further decrease of both LDL-cholesterol by 17% and LDL-apolipoprotein B by 16% occurred. HDL-cholesterol concentration increased significantly in both groups of hyperlipaemic patients during therapy. This may be the effect of both bezafibrate and colestipol. It is concluded that bile acid resins may effectively prevent the LDL-cholesterol concentration increase observed sometimes after clofibrate analogues.  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