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   2620273篇
  免费   191702篇
  国内免费   7702篇
耳鼻咽喉   34708篇
儿科学   85924篇
妇产科学   72063篇
基础医学   368555篇
口腔科学   70589篇
临床医学   238339篇
内科学   523029篇
皮肤病学   63288篇
神经病学   217941篇
特种医学   101912篇
外国民族医学   736篇
外科学   393016篇
综合类   50574篇
现状与发展   5篇
一般理论   980篇
预防医学   197539篇
眼科学   57133篇
药学   190332篇
  8篇
中国医学   5394篇
肿瘤学   147612篇
  2021年   21076篇
  2019年   21646篇
  2018年   30421篇
  2017年   23522篇
  2016年   27283篇
  2015年   30732篇
  2014年   41997篇
  2013年   62385篇
  2012年   83359篇
  2011年   87675篇
  2010年   52912篇
  2009年   50887篇
  2008年   81816篇
  2007年   86671篇
  2006年   88183篇
  2005年   84348篇
  2004年   81038篇
  2003年   78257篇
  2002年   75377篇
  2001年   128764篇
  2000年   131606篇
  1999年   110835篇
  1998年   31663篇
  1997年   28233篇
  1996年   28458篇
  1995年   27573篇
  1994年   25256篇
  1993年   23559篇
  1992年   85278篇
  1991年   81678篇
  1990年   78865篇
  1989年   76126篇
  1988年   69542篇
  1987年   68041篇
  1986年   63607篇
  1985年   60566篇
  1984年   45031篇
  1983年   38006篇
  1982年   22522篇
  1981年   20030篇
  1979年   39000篇
  1978年   27479篇
  1977年   23294篇
  1976年   21538篇
  1975年   22855篇
  1974年   26827篇
  1973年   25407篇
  1972年   23772篇
  1971年   21975篇
  1970年   20174篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
142.
143.
Children who expect they can bring about good outcomes and avoid bad outcomes tend to experience more personal successes. Little is known about factors that contribute to these ‘control expectancies’. The purpose of the present study was to determine whether children's internal control expectancies occur in the context of parents’ internal control expectancies, low family strain, and high family cohesiveness and whether these factors are more strongly related to daughters’ than sons’ control expectancies. A community sample of 85 children aged 9–11 years and their parents (85 mothers; 63 fathers) completed rating scales. Fathers’ more internal control expectancies and mothers’ reports of fewer family strains were associated with daughters’ but not sons’ greater internal control expectancies, and greater family cohesiveness was related to both daughters’ and sons’ internal control orientations. These findings suggest that family factors may contribute to children's, particularly daughters’, development of internal control expectancies.  相似文献   
144.
Individuals with sudden unilateral deafness offer a unique opportunity to study plasticity of the binaural auditory system in adult humans. Stimulation of the intact ear results in increased activity in the auditory cortex. However, there are no reports of changes at sub-cortical levels in humans. Therefore, the aim of the present study was to investigate changes in sub-cortical activity immediately before and after the onset of surgically induced unilateral deafness in adult humans. Click-evoked auditory brainstem responses (ABRs) to stimulation of the healthy ear were recorded from ten adults during the course of translabyrinthine surgery for the removal of a unilateral acoustic neuroma. This surgical technique always results in abrupt deafferentation of the affected ear. The results revealed a rapid (within minutes) reduction in latency of wave V (mean pre = 6.55 ms; mean post = 6.15 ms; p < 0.001). A latency reduction was also observed for wave III (mean pre = 4.40 ms; mean post = 4.13 ms; p < 0.001). These reductions in response latency are consistent with functional changes including disinhibition or/and more rapid intra-cellular signalling affecting binaurally sensitive neurons in the central auditory system. The results are highly relevant for improved understanding of putative physiological mechanisms underlying perceptual disorders such as tinnitus and hyperacusis.  相似文献   
145.
146.
147.
148.
In the 6th Basic Plan for Long-Term Electricity Supply and Demand (6th BPE) for Korea, for the first time, the environmental costs of air pollution caused by oxides of sulfur (SOx), oxides of nitrogen (NOx), and particulate matters (PM) from power plants were estimated and included. However, several deficiencies in evaluating the environmental costs were found. In this study, (1) the validity of the environmental costs used in the 6th BPE was assessed, (2) a systematic approach was suggested and used to improve the environmental costs estimation, and (3) the sensitivity of the cost of generating electricity to the environmental costs by fuel type with the proposed approach was discussed. We found that the applied environmental costs used in the 6th BPE did not fully include the demographic characteristics of Korea. By applying more realistic parameter values, it was found that the newly estimated environmental cost was about 23 times higher than the cost estimated in the original 6th BPE for coal-fired power plants and about 1.5 times higher for liquefied natural gas (LNG)-fired power plants, suggesting that LNG-fired power plants are more economical if using more realistic environmental costs. Thus, it is critical to check the validity of parameter values when calculating environmental costs.  相似文献   
149.
150.
We present a patient with both dynamic left ventricular outflow tract obstruction and valvular aortic stenosis. The aortic valve was calcified, and velocities and gradients measured by continuous‐wave Doppler met standard criteria for severe aortic stenosis. The increased subvalvular velocities invalidated assumptions of the simplified Bernoulli equation; correction using the longer form of the Bernoulli equation suggested a lower but still significant gradient. The complex shape of the subvalvular spectral Doppler envelope indicated supranormal systolic function and dynamic left ventricular outflow obstruction. Left heart catheterization with an end‐hole catheter was required to determine the subvalvular and valvular components of the obstruction.  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