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   4500891篇
  免费   341549篇
  国内免费   10704篇
耳鼻咽喉   64379篇
儿科学   144220篇
妇产科学   122100篇
基础医学   638157篇
口腔科学   130478篇
临床医学   417166篇
内科学   861942篇
皮肤病学   99072篇
神经病学   367741篇
特种医学   174170篇
外国民族医学   1487篇
外科学   678278篇
综合类   105571篇
现状与发展   15篇
一般理论   1870篇
预防医学   370404篇
眼科学   106697篇
药学   332157篇
  18篇
中国医学   8465篇
肿瘤学   228757篇
  2018年   47874篇
  2017年   36493篇
  2016年   41618篇
  2015年   46924篇
  2014年   66782篇
  2013年   101958篇
  2012年   135115篇
  2011年   144418篇
  2010年   87065篇
  2009年   82693篇
  2008年   135503篇
  2007年   144425篇
  2006年   145777篇
  2005年   141940篇
  2004年   136206篇
  2003年   131303篇
  2002年   128005篇
  2001年   196856篇
  2000年   202871篇
  1999年   171706篇
  1998年   53141篇
  1997年   46947篇
  1996年   46648篇
  1995年   45362篇
  1994年   42260篇
  1993年   39720篇
  1992年   138346篇
  1991年   135277篇
  1990年   131496篇
  1989年   126466篇
  1988年   117323篇
  1987年   115477篇
  1986年   109300篇
  1985年   105384篇
  1984年   80144篇
  1983年   68487篇
  1982年   41956篇
  1981年   37811篇
  1979年   75273篇
  1978年   53936篇
  1977年   45355篇
  1976年   43090篇
  1975年   45701篇
  1974年   55371篇
  1973年   52871篇
  1972年   50059篇
  1971年   46854篇
  1970年   43493篇
  1969年   41073篇
  1968年   37924篇
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
211.
Objective: Polyunsaturated fatty acids n-3 (PUFA n-3) have shown effects in reducing tumor growth, in particular eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) abundantly present in fish oil (FO). When these fatty acids are provided in the diet, they alter the functions of the cells, particularly in tumor and immune cells. However, the effects of α-linolenic fatty acid (ALA), which is the precursor of EPA and DHA, are controversial. Thus, our objective was to test the effect of this parental fatty acid. Methods: Non-tumor-bearing and tumor-bearing Wistar rats (70 days) were supplemented with 1 g/kg body weight of FO or Oro Inca® (OI) oil (rich in ALA). Immune cells function, proliferation, cytokine production, and subpopulation profile were evaluated. Results: We have shown that innate immune cells enhanced phagocytosis capacity, and increased processing and elimination of antigens. Moreover, there was a decrease in production of pro-inflammatory cytokines (tumor necrosis factor-alpha (TNF-α) and interleukin 6 (IL-6)) by macrophages. Lymphocytes showed decreased proliferation capacity, increased cluster of differentiation 8 (CD8+) subpopulation, and increased TNF-α production. Conclusions: Oil rich in ALA caused similar immune modulation in cancer when compared with FO.  相似文献   
212.
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   
213.
214.
215.
216.
217.
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   
218.
219.
220.
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