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   454819篇
  免费   40435篇
  国内免费   31227篇
耳鼻咽喉   4303篇
儿科学   4812篇
妇产科学   6321篇
基础医学   55450篇
口腔科学   7904篇
临床医学   61699篇
内科学   67761篇
皮肤病学   4878篇
神经病学   25195篇
特种医学   17656篇
外国民族医学   259篇
外科学   45767篇
综合类   71620篇
现状与发展   104篇
一般理论   39篇
预防医学   28447篇
眼科学   13465篇
药学   46962篇
  449篇
中国医学   25262篇
肿瘤学   38128篇
  2024年   1342篇
  2023年   6530篇
  2022年   17450篇
  2021年   22102篇
  2020年   16326篇
  2019年   14560篇
  2018年   15383篇
  2017年   13668篇
  2016年   13193篇
  2015年   20076篇
  2014年   24958篇
  2013年   22257篇
  2012年   32831篇
  2011年   36967篇
  2010年   23214篇
  2009年   18412篇
  2008年   24636篇
  2007年   24459篇
  2006年   24361篇
  2005年   23737篇
  2004年   15444篇
  2003年   14492篇
  2002年   12486篇
  2001年   10609篇
  2000年   11177篇
  1999年   11824篇
  1998年   7307篇
  1997年   7165篇
  1996年   5692篇
  1995年   5195篇
  1994年   4329篇
  1993年   2839篇
  1992年   3650篇
  1991年   3163篇
  1990年   2772篇
  1989年   2425篇
  1988年   1999篇
  1987年   1751篇
  1986年   1434篇
  1985年   1153篇
  1984年   644篇
  1983年   449篇
  1982年   306篇
  1981年   291篇
  1980年   227篇
  1979年   254篇
  1978年   88篇
  1977年   91篇
  1974年   106篇
  1973年   93篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
An indirect enzyme-linked immunosorbent assay (ELISA) for the detection of hexoestrol (HES) was developed, optimized and validated for the analysis of HES in pork. Many parameters, such as the volume ratio of solution A and solution B, colour developing time, pH value, incubation time, the volume ratio of the standard solution and diluted antiserum, blocking solution, blocking condition, coating solution and coating condition were studied and optimized in the paper. The regression equation of the final inhibition curve is y = - 0.3345x + 1.4955, R2=0.9913. The linear range is 0.1-8.1 ng/ml, and the IC50 is 0.671 ng/ml. The specificity of the assay was evaluated by the cross-reactivity rates of six compounds, of which two structurally related compounds had a relatively higher cross-reactivity rate of 25% and 6%. HES was added into a pork sample at 5 ng/g level and then the sample was extracted. The recovery is between 49.6% and 79.2%, and the variation coefficient is 0.164.  相似文献   
52.
给药系统     
近年来,伴随着药物治疗的快速发展.以药理活性非常强的药物为代表,开发出许多用药时必须给予足够关注的药物,“用药最适化”这一概念逐渐成为人们非常关注的问题。这主要是为了实现用药时的最佳形式。尽可能地根据选择或者需要控制药物的浓度.时间模式。输送到药物的作用表达部位。实现治疗用药的安全性。但是,历来的方法却很难实现这一点,通过利用新的技术和方法调控药物在体内的动态变化,以获得最好治疗效果为中心的药物使用方法和药剂正在开发之中。这就是给药系统,使用可以表达自身概念的语言来命名。虽然都是以各种药物在体内的动态过程作为调控对象,但是还分为①controlled release(调控释放给药);②开发新的给药途径、克服药物吸收障碍;③靶向给药(targeting)等三个途径。  相似文献   
53.
Fully soluble hemostatic fiber (FHF) is made from cotton yarn through a series of chemical reactions with NaOH and chloroacetic acid. The major component of FHF is carboxymethylcellulose. FHF is a kind of biodegradation macromolecule material that can disassociate into a low-molecular-weight compound or a simple substance by hydrolytic and enzymatic courses. The purpose of the present study is to investigate the hemostatic mechanism of FHF. The study indicated that FHF can stop bleeding by physical, chemical and physiological routes. In the physical route, expansion of carboxymethylcellulose in FHF stops bleeding by forming a mechanical clog after contacting with the blood. In the chemical route, the platelets can quickly aggregate around FHF and stimulate releasing and disaggregating reactions, after contacting with the rough surface of FHF, producing thrombus and hemostasis. In the physiological route, gluey particles with negative charges can activate intrinsic coagulation systems by activating the blood coagulation factor XII after FHF dissolution.  相似文献   
54.
55.
现将我院2002-2005年收治住院的急性心肌梗死患者56例的心理干预及护理体会,报告如下:  相似文献   
56.
Bone morphogenetic protein (BMP) was isolated from the bone matrix of swine and partially purified by means of differential precipitation and molecular sieve chromatography. The molecular weight of BMP estimated by SDS-gel electrophoresis was 19,000 dalton. Bioassay by implanting two milligrams of BMP fraction into thigh muscles of mice resulted in bone formation in 100% of the experimental animals.
  相似文献   
57.
PURPOSE: Perineural invasion is a frequent occurrence in salivary adenoid cystic carcinoma (ACC) and may prevent complete surgical resection. Studies have indicated that nerve growth factor (NGF) and its high-affinity receptor tyrosine kinase A (TrkA) may play a role in perineural invasion in several malignancies in which perineural invasion is observed. The present study was conducted to investigate the expression of NGF and TrkA in salivary ACC and to examine the effects of NGF on adhesion, migration and invasion capacities of a salivary ACC cell line (SACC-83) in vitro. PATIENTS AND METHODS: Expression of NGF and TrkA was explored using immunohistochemistry in paraffin-embedded tissues of 32 cases of salivary ACC. The effects of NGF on in vitro adhesion, migration, and invasion capacities of the SACC-83 cell line were examined using an MTT assay and a modified Boyden chamber assay respectively. RESULTS: In ACC specimens, 31 (96.9%) and 32 (100%) tumors showed immunoreactivity for NGF and TrkA respectively. Significant correlations were found between NGF/TrkA expression levels and perineural invasion (P < .05). In cell adhesion assay, the percent adherences of SACC-83 cells co-cultured with 25 ng/ml NGF at 1.5 hours and 5, 25 ng/ml NGF at 6 hours were significantly higher than that co-cultured with 0 ng/ml NGF (P < .05). However, high concentration of NGF (500 ng/ml) resulted in a significant inhibition of invasion (P < .05). CONCLUSION: Overexpression of NGF and TrkA in human salivary ACC tissues may constitute a reason for perineural invasion in salivary ACC.  相似文献   
58.
59.
A prospective study was conducted with patients with pulmonary infections who were consecutively admitted to the three community hospitals in Benghu from July 1986 to May 1987, and to the children's hospital in Nanjing from September 1986 to January 1987. Antibodies to Lpi-8, Lm, Ld, and Lg were measured by the micro-agglutination test. During the study period, 150 adult patients (100 pairs sera) and 212 control healthy people and 110 pairs sera of childhood patients and 173 children without respiratory tract infections were investigated. The diagnosis of legionellosis was based on seroconversion (fourfold rise in titer to greater than 1:32 or static titer of greater than 1:32) and clinical and radiographic features of legionnaires' disease. About 11% legionella infection in hospitalized adult patients with pulmonary infections, and about 5.45% in children with atypical pneumonias.  相似文献   
60.
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