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   111170篇
  免费   45806篇
  国内免费   2177篇
耳鼻咽喉   1807篇
儿科学   4580篇
妇产科学   831篇
基础医学   18440篇
口腔科学   5862篇
临床医学   17047篇
内科学   26656篇
皮肤病学   7836篇
神经病学   14683篇
特种医学   3479篇
外国民族医学   13篇
外科学   16612篇
综合类   7974篇
现状与发展   10篇
一般理论   24篇
预防医学   7550篇
眼科学   2147篇
药学   9746篇
  48篇
中国医学   4457篇
肿瘤学   9351篇
  2024年   719篇
  2023年   980篇
  2022年   1913篇
  2021年   3667篇
  2020年   7595篇
  2019年   11949篇
  2018年   11243篇
  2017年   12655篇
  2016年   13107篇
  2015年   13425篇
  2014年   13618篇
  2013年   14100篇
  2012年   6599篇
  2011年   6585篇
  2010年   10702篇
  2009年   6714篇
  2008年   3620篇
  2007年   2610篇
  2006年   2551篇
  2005年   1983篇
  2004年   1940篇
  2003年   2342篇
  2002年   2154篇
  2001年   2067篇
  2000年   1458篇
  1999年   743篇
  1998年   271篇
  1997年   250篇
  1996年   176篇
  1995年   159篇
  1994年   133篇
  1993年   85篇
  1992年   143篇
  1991年   88篇
  1990年   108篇
  1989年   68篇
  1988年   76篇
  1987年   57篇
  1986年   56篇
  1985年   43篇
  1984年   44篇
  1983年   27篇
  1982年   17篇
  1981年   16篇
  1979年   49篇
  1978年   23篇
  1977年   23篇
  1975年   31篇
  1974年   37篇
  1973年   15篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
Power estimations are important for optimizing genotype‐phenotype association study designs. However, existing frameworks are designed for common disorders, and thus ill‐suited for the inherent challenges of studies for low‐prevalence conditions such as rare diseases and infrequent adverse drug reactions. These challenges include small sample sizes and the need to leverage genetic annotation resources in association analyses for the purpose of ranking potential causal genes. We present SimPEL, a simulation‐based program providing power estimations for the design of low‐prevalence condition studies. SimPEL integrates the usage of gene annotation resources for association analyses. Customizable parameters, including the penetrance of the putative causal allele and the employed pathogenic scoring system, allow SimPEL to realistically model a large range of study designs. To demonstrate the effects of various parameters on power, we estimated the power of several simulated designs using SimPEL and captured power trends in agreement with observations from current literature on low‐frequency condition studies. SimPEL, as a tool, provides researchers studying low‐frequency conditions with an intuitive and highly flexible avenue for statistical power estimation. The platform‐independent “batteries included” executable and default input files are available at https://github.com/precisionomics/SimPEL .  相似文献   
44.
45.
46.
47.
Poland is one of the countries distinguished by a long and colorful past. Undergoing numerous turbulent socio-economic changes forced by the course of history, Poland is now one of the member states of the European Union. Experiencing low water quantity and high contamination levels in surface waters, Poland is following other EU countries in the effort to reach a “good” water status. Herein are presented impacts of changes in Polish history on water legislation, management, and research, as well as explanations for the perceptible split between engineering and scientific approaches to the aquatic issues. Drawbacks caused by unsatisfactory state research funding for the sciences and division of the water related contemporary scientific interests are also discussed.  相似文献   
48.
49.

Background

South Africa is the first sub‐Saharan African country to legislate, fund and implement free preschool education. Human rights and restitution were at the forefront of the political struggle for democracy in South Africa. Levelling the playing fields by improving the school readiness of children disadvantaged by the racist policies of Apartheid is essential to the transformation of South African society.

Methods

A review of published and unpublished documents on Grade R was undertaken, and access and enrolment data come from the National Department of Basic Education's Education Management Information System (EMIS).

Results

A decade after initiation in 2005, 79% of 5‐year‐olds was enrolled in a preschool class; the vast majority of them in free public schools. Grade R is near universal and on track to becoming compulsory. It is part of the Foundation Phase (Grades 1–3) of schooling, falling under the Department of Basic Education, but also part of a broader national strategy to improve early child development under the direction of an Inter‐Departmental Steering. Evaluations demonstrate wide access to Grade R and high uptake, especially in the poorest areas. However, the quality of Grade R provision in these areas is not up to standard because of low levels of funding; inadequate training, supervision, remuneration and retention of Grade R teachers; insufficient learner support materials; and inadequate monitoring and quality assurance.

Conclusions

Lack of quality, amongst other factors, contributes to a widening school performance gap between children from more and less privileged areas. Quality of Grade R as well as earlier learning and subsequent years of schooling must be improved to achieve South Africa's aim to reduce poverty and inequality through, amongst others, parent and family involvement, learning in the home and preschool preparation.  相似文献   
50.
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