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   1777篇
  免费   129篇
  国内免费   39篇
耳鼻咽喉   51篇
儿科学   92篇
妇产科学   82篇
基础医学   167篇
口腔科学   45篇
临床医学   239篇
内科学   316篇
皮肤病学   15篇
神经病学   44篇
特种医学   269篇
外科学   166篇
综合类   27篇
一般理论   13篇
预防医学   219篇
眼科学   25篇
药学   69篇
肿瘤学   106篇
  2023年   8篇
  2021年   20篇
  2020年   11篇
  2019年   20篇
  2018年   26篇
  2017年   25篇
  2016年   17篇
  2015年   24篇
  2014年   42篇
  2013年   61篇
  2012年   77篇
  2011年   74篇
  2010年   79篇
  2009年   71篇
  2008年   71篇
  2007年   100篇
  2006年   68篇
  2005年   76篇
  2004年   52篇
  2003年   40篇
  2002年   53篇
  2001年   46篇
  2000年   44篇
  1999年   41篇
  1998年   58篇
  1997年   56篇
  1996年   52篇
  1995年   45篇
  1994年   46篇
  1993年   33篇
  1992年   10篇
  1991年   24篇
  1990年   19篇
  1989年   34篇
  1988年   31篇
  1987年   18篇
  1986年   20篇
  1985年   19篇
  1984年   19篇
  1983年   12篇
  1982年   13篇
  1981年   14篇
  1980年   18篇
  1979年   14篇
  1978年   10篇
  1977年   18篇
  1976年   11篇
  1975年   9篇
  1922年   14篇
  1921年   13篇
排序方式: 共有1945条查询结果,搜索用时 15 毫秒
21.
The development of both adenocarcinoma of the jejunum and in situ squamous carcinoma of the oesophagus in an adult coeliac patient is described. Good evidence that adenocarcinoma of jejunum occurs more frequently in patients with coeliac disease has recently become available though this association has been suggested for some time. While oesophageal carcinoma has long been associated with coeliac disease, in situ carcinoma of oesophagus has not been previously described in these circumstances. We feel that the risk of this complication, as calculated from published series, warrants a screening programme for oesophageal malignancy in adult coeliacs.  相似文献   
22.
23.
24.
25.
Predictive value of normal sperm morphology: a structured literature review   总被引:12,自引:0,他引:12  
The aim of the study was to conduct a structured review of theliterature published on the use of normal sperm morphology,as an indicator of male fertility potential in the in-vitrofertilization (IVF) situation, and to establish the universalpredictive value of this semen parameter. Published literaturein which normal sperm morphology was used to predict fertilizationand pregnancy, during the period 1978-1996, was reviewed. Atotal of 216 articles were identified by the sourcing methodology,but only 49 provided data that could be tabulated and analysed.Of these, only 18 provided sufficient data for statistical analysis.Fifteen studies used the strict criteria to evaluate sperm morphology,two used World Health Organization (WHO) guidelines and oneused both the strict criteria and the WHO guidelines. All thestudies (n=10) using the 5 and 14% normal sperm morphology thresholds(strict criteria) produced positive predictive values for IVFsuccess. In the prediction of pregnancy, 82% (9/11) and 75%(6/8) of the studies produced positive predictive values whenusing the 5% and 14% thresholds respectively. Aggregating thedata produced around the 5% normal sperm morphology threshold(strict criteria), the overall fertilization rates were 59.3%(1979/3337; per oocyte) for the 4% group and 77.6% (10345/13327;per oocyte) for the >4% group, and the overall pregnancyrates were 15.2% (60/395; per cycle) and 26.0% (355/1368; percycle) respectively. The no-transfer rates across the 5% thresholdwere 24.0% (86/359; per cycle) in the 4% group compared to 7.4%(80/1088; per cycle) in the >4% group. The inclusion of anaccurately evaluated normal sperm morphology count as an integralpart of the standard semen analysis makes this analysis stillthe most cost-effective means of evaluating the male factor.  相似文献   
26.
Contact skin immunization of mice with reactive hapten antigen and subsequent airway challenge with the same hapten induces immediate airflow obstruction and subsequent airway hyper‐reactivity (AHR) to methacholine challenge, which is dependent on B cells but not on T cells. This responsiveness to airway challenge with antigen is elicited as early as 1 day postimmunization and can be adoptively transferred to naïve recipients via 1‐day immune cells. Responses are absent in 1‐day immune B‐cell‐deficient JH?/? mice and B‐1 B‐cell‐deficient xid male mice, as well as in recipients of 1‐day immune cells depleted of cells with the B‐1 cell phenotype (CD19+ B220+ CD5+). As B‐1 cells produce immunoglobulin M (IgM), we sought and found significantly increased numbers of anti‐hapten IgM‐producing cells in the spleen and lymph nodes of 1‐day immune wild‐type mice, but not in xid mice. Then, we passively immunized naive mice with anti‐hapten IgM monoclonal antibody and, following airway hapten challenge of the recipients, we showed both immediate airflow obstruction and AHR. In addition, AHR was absent in complement C5 and C5a receptor‐deficient mice. In summary, this study of the very early elicited phase of a hapten asthma model suggests, for the first time, a role of B‐1 cells in producing IgM to activate complement to rapidly mediate asthma airway reactivity only 1 day after immunization.  相似文献   
27.
Chitin is the second most abundant biopolymer in nature, where it protects crustaceans, parasites, fungi, and other pathogens from the adverse effects of their environments, hosts, or both. Because chitin does not exist in mammals, it had been assumed that the chitinases that degrade it are also restricted to lower life forms. However, chitinases and chitinase-like proteins have recently been noted in mice and human subjects. The prototypic chitinase, acidic mammalian chitinase, was also noted to be induced during T(H)2 inflammation through an IL-13-dependent mechanism. It was also shown to play an important role in the pathogenesis of T(H)2 inflammation and IL-13 effector pathway activation and demonstrated to be expressed in an exaggerated fashion in human asthmatic tissues. The finding that chitinases contribute to host anti-parasite responses and asthmatic T(H)2 inflammation support the concept that asthma might be a parasite-independent anti-parasite response.  相似文献   
28.
IL-11: insights in asthma from overexpression transgenic modeling   总被引:8,自引:0,他引:8  
The evolution of our understanding of IL-11 mirrors, in many ways, the problems that are faced by investigators in the post-genome era and the types of techniques that might need to be used to deal with these issues. IL-11 was discovered as a soluble factor in fibroblast supernatants that stimulated the proliferation of "IL-6-dependent" plasmacytoma cells. It was subsequently demonstrated to be an important stimulator of platelet reconstitution and a pleiotropic regulator of nonrespiratory tissues. In the lung, IL-11 is produced by a variety of structural cells and eosinophils in response to a variety of stimuli, including TGF-beta, major basic proteins, and viruses. IL-11 is also detected in exaggerated quantities at sites of virus infection. Its potential effector functions at these sites were defined with constitutive and inducible overexpression transgenic modeling systems which demonstrated that IL-11 causes nodular mononuclear infiltrates, airway remodeling with subepithelial fibrosis, airways obstruction, and airways hyperresponsiveness and can block alveolar development when expressed during development. In accord with these murine findings, IL-11 is selectively expressed in eosinophils and epithelial cells in patients with moderate and severe asthma where expression correlates directly with disease severity and inversely with FEV(1). Studies using transgenic mice also demonstrated that IL-11 inhibits antigen-induced tissue inflammation. Thus IL-11 might be an important regulator of inflammatory and remodeling responses in the asthmatic airway.  相似文献   
29.
30.
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