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   999515篇
  免费   75414篇
  国内免费   2611篇
耳鼻咽喉   12985篇
儿科学   34538篇
妇产科学   28496篇
基础医学   145423篇
口腔科学   27766篇
临床医学   90571篇
内科学   194166篇
皮肤病学   22978篇
神经病学   79304篇
特种医学   38420篇
外国民族医学   305篇
外科学   149670篇
综合类   23788篇
一般理论   394篇
预防医学   77949篇
眼科学   22651篇
药学   72019篇
  14篇
中国医学   2034篇
肿瘤学   54069篇
  2018年   10557篇
  2017年   8238篇
  2016年   9384篇
  2015年   10607篇
  2014年   14430篇
  2013年   22013篇
  2012年   28986篇
  2011年   30826篇
  2010年   18509篇
  2009年   17465篇
  2008年   28792篇
  2007年   30469篇
  2006年   30975篇
  2005年   29640篇
  2004年   28925篇
  2003年   27801篇
  2002年   26813篇
  2001年   46928篇
  2000年   48040篇
  1999年   40285篇
  1998年   11213篇
  1997年   10136篇
  1996年   10206篇
  1995年   9810篇
  1994年   9122篇
  1993年   8520篇
  1992年   32272篇
  1991年   31488篇
  1990年   31037篇
  1989年   29894篇
  1988年   27188篇
  1987年   27340篇
  1986年   25461篇
  1985年   24616篇
  1984年   18422篇
  1983年   15530篇
  1982年   9310篇
  1981年   8396篇
  1979年   16887篇
  1978年   12239篇
  1977年   10326篇
  1976年   9761篇
  1975年   10187篇
  1974年   12325篇
  1973年   11847篇
  1972年   10886篇
  1971年   10120篇
  1970年   9380篇
  1969年   8727篇
  1968年   8111篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Gas-to-liquid (GTL) products are synthetic hydrocarbons produced from natural gas using a catalytic process known as the Fischer–Tropsch process. This process yields a synthetic crude oil that consists of saturated hydrocarbons which can subsequently be refined to a range of products analogous to those obtained from petroleum refining. However, in contrast to their petroleum-derived analogs, GTL products are essentially free of unsaturated or aromatic compounds and do not contain any sulfur-, oxygen-, or nitrogen-containing compounds. Under new chemical substance notification requirements, an extensive testing program covering the entire portfolio of GTL products has been undertaken to assess their hazardous properties to human health and environment. The results of these studies have been summarized in a two-part review. Part 1 provides an overview of the mammalian toxicity hazardous properties of the various GTL products. This second part of the review focuses on the aquatic, sediment, terrestrial, and avian toxicity studies which assess the ecotoxicological hazard profile of the GTL products. Many challenges were encountered during these tests relating to dosing, analysis and interpretation of results. These are discussed with the intent to share experiences to help inform and shape future regulatory mandates for testing of poorly soluble complex substances. As was the case with the mammalian toxicology review, there were a few cases where adverse effects were found, but overall the GTL products were found to exert minimal adverse ecotoxicological effects and these were less severe than effects observed with their conventional, petroleum-derived analogs.  相似文献   
72.
Introduction: Diabetes Mellitus has been considered an epidemic by the World Health Organization, with a high risk of morbidity and mortality. The treatment of this pathology consists in glycemic control, which can be done by oral hypoglycemic agents, insulin therapy, dietary guidance, regular physical activity, and psychosocial support. In addition, other adjuvant treatments are employed, such as phytotherapic, and one of the most used plants is Bauhinia forficata.

Areas covered: In the current review, patents using Bauhinia forficata for the Diabetes Mellitus treatment have been analyzed. There were 03 patents in WIPO, 01 in Espacenet, 01 in USPTO, and 02 in INPI.

Expert opinion: Patents on the adjuvant treatment of Diabetes Mellitus by Bauhinia forficata are discussed. Although there are some phytotherapy products containing this medicinal plant which has hypoglycemic effect here is still a need for the development of more products based on natural resources, for the treatment of this pathology, without side effects and with other benefits, to assist in the glycemia control in diabetic patients, and to improve their quality of life.  相似文献   

73.
74.
75.

Objective

To determine differences between men and women in hazardous drinking, heavy cannabis use and hypnosedative use according to educational level and employment status in the economically active population in Spain.

Method

Cross-sectional study with data from 2013 Spanish Household Survey on Alcohol and Drugs on individuals aged 25-64 [n = 14,113 (women = 6,171; men = 7,942)]. Dependent variables were hazardous drinking, heavy cannabis use and hypnosedative consumption; the main independent variables were educational level and employment situation. Associations between dependent and independent variables were calculated with Poisson regression models with robust variance. All analyses were stratified by sex.

Results

Hazardous drinking and heavy cannabis use were higher in men, while women consumed more hypnosedatives. The lower the educational level, the greater the gender differences in the prevalence of this substances owing to different consumption patterns in men and women. While men with a lower educational level were higher hazardous drinkers [RII = 2.57 (95%CI: 1.75-3.78)] and heavy cannabis users [RII = 3.03 (95%CI: 1.88-4.89)] compared to higher educational level, in women the prevalence was the same. Women with a lower education level and men with a higher education level had higher hypnosedative consumption. Unemployment was associated with increased heavy cannabis use and hypnosedative use in both women and men and with lower hazardous drinking only in women.

Conclusions

There are differences between men and women in the use of psychoactive substances that can be explained by the unequal distribution of substance use in them according to educational level. Unemployment was associated with substance use in both men and women.  相似文献   
76.
77.
78.
79.
80.
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