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   21724篇
  免费   562篇
  国内免费   176篇
耳鼻咽喉   66篇
儿科学   1147篇
妇产科学   774篇
基础医学   2974篇
口腔科学   234篇
临床医学   1166篇
内科学   5755篇
皮肤病学   352篇
神经病学   1777篇
特种医学   662篇
外国民族医学   1篇
外科学   3508篇
综合类   690篇
预防医学   795篇
眼科学   319篇
药学   1150篇
  2篇
中国医学   278篇
肿瘤学   812篇
  2023年   113篇
  2022年   258篇
  2021年   366篇
  2020年   251篇
  2019年   1425篇
  2018年   1354篇
  2017年   633篇
  2016年   227篇
  2015年   282篇
  2014年   427篇
  2013年   444篇
  2012年   386篇
  2011年   418篇
  2010年   312篇
  2009年   299篇
  2008年   311篇
  2007年   294篇
  2006年   303篇
  2005年   246篇
  2004年   224篇
  2003年   225篇
  2002年   174篇
  2001年   153篇
  2000年   116篇
  1999年   114篇
  1998年   94篇
  1997年   92篇
  1996年   82篇
  1995年   69篇
  1994年   62篇
  1993年   59篇
  1992年   43篇
  1991年   61篇
  1990年   47篇
  1989年   40篇
  1988年   31篇
  1987年   43篇
  1985年   1059篇
  1984年   1784篇
  1983年   1149篇
  1982年   1241篇
  1981年   1205篇
  1980年   998篇
  1979年   897篇
  1978年   830篇
  1977年   704篇
  1976年   798篇
  1975年   556篇
  1974年   505篇
  1973年   559篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
In a comprehensive study of 80 patients with vasculitis, 4 had concurrent hepatitis B virus (HBV) infection. Polyarteritis nodosa was present in 2 and in the other 2, cutaneous vasculitis, presenting clinically as palpable or Henoch-Schönlein purpura. In one of these patients skin biopsies demonstrated granular deposits of IgM, C3, C4, and the hepatitis B surface antigen (HBsAg) and electron-dense deposits of aggregated 20-nm particles resembling HBsAg in postcapillary venules. Evidence for circulating HBsAg-immune complexes included increased serum C1q binding activity, decreased serum complement, and a cryoprecipitate containing both HBsAg and IgM anti-HBs. Aggregated 20-nm particles resembling intact HBsAg were also seen by negative staining electron microscopy of the serum cryoprecipitate. This patient fulfills all the criteria for a specific immune complex vasculitis caused by his immune response to a chronic HBV infection. These findings emphasize that HBV infection may be associated with small vessel vasculitis as well as polyarteritis nodosa, mixed cryoglobulinemia, and glomerulonephritis. A similar immune response to other viral infections may be expressed as palpable (Henoch-Schönlein) purpura also.  相似文献   
92.
The sister chromatid exchange (SCE) incidence and growth kinetics have been studied by means of an in vitro bromodeoxyuridine (BrdU) chromosome labeling method in the bone marrow cells of 17 acute myeloblastic leukemia (AML) patients with only diploid cells at diagnosis, remission, and relapse of the disease. At diagnosis, the cells tended to exhibit a low SCE frequency as compared to that during remission. An increased SCE frequency was observed after chemotherapy during remission or relapse. At diagnosis and relapse, when leukemic blast cells predominated in the marrow, they were characterized by the predominance of cells that had undergone only one cell cycle after BrdU exposure. In contrast, the marrow cells during remission tended to resemble the control pattern of growth kinetics, with a predominance of cells undergoing second and third cell cycles in the presence of BrdU. These results suggest that the growth rate of leukemic and nonleukemic cells is different, and that chemotherapy can cause an increased SCE frequency in the marrow cells of AML patients irrespective of the state of the disease.  相似文献   
93.
《Immunity》2020,52(4):683-699.e11
  1. Download : Download high-res image (202KB)
  2. Download : Download full-size image
  相似文献   
94.
The regulatory role of vitamin D receptor (VDR) gene variants of Bsm I, Apa I, Taq I, and Fok I polymorphisms on vitamin D(3)-modulated macrophage phagocytosis with live Mycobacterium tuberculosis and lymphoproliferative response to M. tuberculosis culture filtrate antigen (CFA) was studied in patients with pulmonary tuberculosis (n = 46) and in normal healthy subjects (NHS) (n = 64). Vitamin D(3) at a concentration of 1 x 10(-7) M enhanced the phagocytic potential of normal subjects who had a phagocytic index of less than 20%. This increase was seen in subjects with the genotypes BB (p = 0.017), AA (p = 0.016), tt (p = 0.034), and FF (p = 0.013) and the extended genotype BBAAtt (p = 0.034). Normal subjects with BBAAtt performed better phagocytosis than individuals with bbaaTT genotype (p = 0.034). Vitamin D(3) at 10(-9), 10(-8), and 10(-7) M concentrations suppressed the lymphoproliferative response to CFA antigen in normal subjects. This decreased lymphocyte response was observed in normal individuals with the genotypes BB (p = 0.0009), tt (p = 0.016), and FF (p = 0.008) and the extended genotype BBAAtt (p = 0.02). Addition of vitamin D(3) had no significant effect on macrophage phagocytosis and lymphoproliferative response to CFA in pulmonary TB patients. This may be due to the unresponsive nature of the cells to the action of vitamin D(3) or the downregulated VDR expression by virtue of the disease, which renders them inactive. The genotypes BB, tt, and the extended genotype BBAAtt may be associated with increased expression of VDR which in turn regulate the action of vitamin D(3) and modulate the immune functions to M. tuberculosis in NHS.  相似文献   
95.
小鼠胚胎干细胞植入大鼠脑内分化的研究   总被引:5,自引:1,他引:5  
刘述  谢瑶  陈系古  姚志彬 《神经解剖学杂志》2002,18(4):298-300,T059
观察小鼠胚胎干细胞植入大鼠隔区和海马内之后的分化状况。以 SD大鼠为宿主 ,将胚胎干细胞移植入宿主隔区和海马内 ,移植后在 l、2、3、4和 8周取脑 ,冰冻切片 ,进行 Nissl染色和 M6、NSE、GFAP免疫组织化学反应。胚胎干细胞移植入大鼠隔区和海马之后 ,从第 2周开始表达 M6、GFAP、NSE等抗原 ,持续至第 4周 ,主要位于移植区内 ,较少迁移。小鼠胚胎干细胞移植入大鼠隔区和海马内之后 ,分化为神经元和神经胶质细胞  相似文献   
96.
An imprint immunofixation (IIF) technique for the characterization of electrofocused immunoglobulins (Ig) is described. Electrofocused proteins are blotted (imprinted) from the separating polyacrylamide gel to agarose gels by gel-to-gel overlays. The protein imprints are chemically fixed in the agarose gels with a solution of 46% methanol, 8% acetic acid and 46% water. The imprinted Ig are then identified radioimmunologically, using an indirect system with monoclonal mouse anti-human Ig antibodies in the first layer and 125I-labelled rabbit anti-mouse Ig in the second, followed by autoradiography. The method is sensitive and permits characterization of Ig in unconcentrated cerebrospinal fluid. By sequential imprinting, each separated specimen can be characterized for up to 10 separate antigenic determinants without loss of sensitivity.  相似文献   
97.
Fluocortin butyl (FCB) is a newly synthesized corticosteroid with a high ratio of topical to systemic activity. FCB was studied in a multi-center, double-blind, placebo-controlled trial of therapy of perennial rhinitis. The study was conducted between January and May 1981. Patients evaluated suffered from either chronic allergic or chronic nonallergic rhinitis or both. A total of 306 patients from 16 investigative centers were evaluated by comparing FCB to placebo. Three separate dosage regimens were employed. Patients received a total daily dose of 2, 4, or 8 mg. FCB was found to be an effective therapeutic agent. It reduced symptoms of nasal congestion, rhinorrhea, postnasal drainage, and sneezing. It also markedly reduced the use of concomitant medications (chlorpheniramine maleate and/or pseudoephedrine). Relief of symptoms was noted as early as the first week of therapy, and the degree of improvement increased progressively during the study. There was little difference between the relief produced by the 4 mg and 8 mg regimens. Both of these were superior to the 2 mg regimen. The drug was well tolerated; no significant side effects were noted.  相似文献   
98.
Bronchodilator efficacy of metaproterenol sulfate aerosol therapy delivered either by canister or jet nebulizer was compared in 25 patients, 13 with severe asthma and 12 with COPD. Treatment was carried out in double-blind crossover fashion on 2 days and consisted of either metaproterenol sulfate solution 15 mg in 2.3 ml administered from a jet nebulizer or three puffs of metered-dose metaproterenol sulfate (total 1.95 mg) inhaled sequentially. FVC and FEV1 were monitored before and after therapy for 2 hr. In 13 asthmatic patients, FEV1 increased from a baseline mean of 0.83 L to 1.57 L at 2 hr after jet nebulizer therapy and increased from 0.84 L to 1.52 L after canister therapy. In 12 patients with COPD, FEV1 increased from 0.58 L to 0.78 L after jet nebulizer therapy and from 0.57 L to 0.76 L after canister therapy. FVC also increased similarly after each form of therapy. The two types of aerosol therapy were equally effective and were without side effects. Canister therapy has the advantage over jet nebulizer therapy by being convenient and cheaper.  相似文献   
99.
Distinguishing characteristics of a new neuroblastoma cell line   总被引:3,自引:0,他引:3  
The characteristics of a new neuroblastoma cell line (MC-NB-1) established from the bone marrow of a 2-year-old male are described. Morphologically, the cells appear as flattened and epithelial-like or as small and spherical. Electron microscopy demonstrated microtubules and dense core secretory granules. The doubling time was approximately 35 hr. Isoenzyme patterns and catecholamine secretion indicated a human line of neuronal origin. The soft agar tumor colony forming system demonstrated drug resistance in vitro comparable to in vivo nonresponsiveness. The stemline karyotype of MC-NB-1 is 44,Y,del(1) (p22:), -4, -7, +del(7)(q22:), -16, +t(7;16)(16pter leads to 16q24::7q22 leads to 7q32), -17. Additionally, double-minute bodies were observed. However, no evidence of homogeneous staining regions (HSRs) were detected.  相似文献   
100.
Treatment with 17 alpha-methyltestosterone and with some synthetic androgens prevents attacks of hereditary angioedema (HAE). However, the potential hepatotoxicity of 17 alpha-alkylated androgens raises the problem of long-term prophylactic use of these agents. Therefore we compared the efficacy in preventing HAE attacks of 17 alpha-alkylated steroids (danazol and stanozolol) with non-17 alpha-alkylated derivatives (quinbolone, nandrolone decanoate and mesterolone). As the latter group proved ineffective, it seems that a drug's efficacy in preventing HAE attacks is connected to its 17 alpha-alkylation. Moreover, our long-term observations with the minimum effective dose of danazol seem to indicate the absence of important collateral effects.  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