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   3100875篇
  免费   236554篇
  国内免费   6297篇
耳鼻咽喉   44513篇
儿科学   95824篇
妇产科学   84052篇
基础医学   436911篇
口腔科学   88003篇
临床医学   277731篇
内科学   609225篇
皮肤病学   64606篇
神经病学   259614篇
特种医学   121914篇
外国民族医学   1193篇
外科学   468220篇
综合类   69398篇
现状与发展   1篇
一般理论   1218篇
预防医学   248959篇
眼科学   72284篇
药学   229915篇
  6篇
中国医学   6107篇
肿瘤学   164032篇
  2018年   35509篇
  2017年   26913篇
  2016年   29153篇
  2015年   32899篇
  2014年   45745篇
  2013年   70180篇
  2012年   97590篇
  2011年   102488篇
  2010年   59397篇
  2009年   55816篇
  2008年   96314篇
  2007年   102349篇
  2006年   102346篇
  2005年   99924篇
  2004年   95740篇
  2003年   92100篇
  2002年   90297篇
  2001年   137423篇
  2000年   141793篇
  1999年   120210篇
  1998年   34568篇
  1997年   31469篇
  1996年   31196篇
  1995年   29946篇
  1994年   28139篇
  1993年   26303篇
  1992年   96073篇
  1991年   92649篇
  1990年   89628篇
  1989年   86351篇
  1988年   80356篇
  1987年   79076篇
  1986年   75211篇
  1985年   71690篇
  1984年   54241篇
  1983年   46294篇
  1982年   28311篇
  1981年   25029篇
  1979年   50881篇
  1978年   35658篇
  1977年   30271篇
  1976年   28342篇
  1975年   30181篇
  1974年   36955篇
  1973年   35201篇
  1972年   33077篇
  1971年   30558篇
  1970年   28941篇
  1969年   27031篇
  1968年   24945篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Reproductive problems, including congenital malformations, reduced hatching success, and decreased survival of hatchlings, have been observed in colonial-nesting water birds at the San Francisco Bay National Wildlife Refuge (SFBNWR). Twenty-four black-crowned night heron (Nycticorax nycticorax) eggs were collected from SFBNWR in 1983. Twelve of these were collected from separate nests when late-stage embryos were pipping, and an additional egg was randomly collected from each nest for organochlorine analysis. Overt anomalies and skeletal defects were not apparent. Embryonic weights (with partially absorbed yolk sacs removed) were 15% lower (p less than 0.05) in SFBNWR embryos compared to control embryos from the Patuxent Wildlife Research Center (PWRC). Crown-rump length and femur length were shorter for SFBNWR embryos. The geometric mean polychlorinated biphenyl (PCB) concentration in SFBNWR eggs was 4.1 ppm wet weight, with a range of 0.8-52.0 ppm. A negative correlation (r = -0.61; p less than 0.05) existed between embryonic weight and log-transformed PCB residues in whole eggs collected from the same nest at SFBNWR, suggesting a possible impact of PCBs on embryonic growth. A correlation with embryonic weight did not occur for DDE [1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene] residues. Liver microsomal aryl hydrocarbon hydroxylase activity was neither significantly elevated nor correlated with PCB, DDE, or PCB plus DDE log-transformed residues. It is unknown whether the apparent association between PCBs and lower weight is persistent through hatching.  相似文献   
992.
We report a case of vasoactive-agent-induced priapism successfully treated in the emergency department with 10 mg of metaraminol injected into the corpora cavernosa.  相似文献   
993.
994.
The removal of N-linked oligosaccharides by peptide-N4-[N-acetyl-beta-glucoseaminyl]asparagine amidase (previously known as aspartoglycosylamine amidohydrolase and abbreviated N-glycanase) from the surface of blood or insect-transmissible forms of Trypanosoma cruzi markedly increased the capacity of these organisms to associate with (i.e., bind and penetrate) either mouse peritoneal macrophages or rat heart myoblasts. This effect was evidenced by a significant elevation in both the percentage of infected host cells and the average number of parasites per 100 cells. Conversely, N-glycanase treatment of either host cell markedly reduced both parameters to levels significantly below those obtained with cells mock treated with medium alone. The N-glycanase effect on the parasites was inhibited by heat inactivation of the enzyme or by the presence of fetuin, an N-glycanase substrate. The enhanced capacity of N-glycanase-treated T. cruzi to engage the host cells started to subside 2 h after the treatment, indicating the reversibility of the effect. The decreased reactivity of N-glycanase-treated macrophages or myoblasts with T. cruzi suggests that N-linked oligosaccharides on these host cells are involved in the initial phase of the cell infection process. Instead, because T. cruzi interacted more effectively with host cells after treatment with N-glycanase, parasite surface N-linked oligosaccharides would seem to interfere with the association.  相似文献   
995.
Nursing diagnosis as a critical component of the nursing process provides a common taxonomy to describe problems that nurses can treat and is a convenient, logical way to reference nursing standards. Theory is translated into practice with the use of population-specific prototype care guides and a written orders system. Nurses in leadership are responsible for providing the necessary resources to promote professional growth and facilitate desired change. Recommendations to assist with the implementation of nursing diagnosis are identified in Table 1. The system is dependent on staff nurses' professional commitment to learning and willingness to actively participate in change. Involvement of staff nurses continues to be a critical factor in the improvement of nursing practice.  相似文献   
996.
997.
998.
999.
The resolution of three 2-substituted derivatives of idazoxan is described. The enantiomers show large separations in activity in a variety of in vitro and in vivo tests, and the active isomers are all potent and selective antagonists at the alpha 2-adrenoreceptor. The significance of these results in relation to those published on the enantiomers of idazoxan and to those on optically active alpha 2-adrenoreceptor agonists is discussed.  相似文献   
1000.
Synthesis of Estradiol Haptens Two estradiol haptens, 4-(3β,17β-dihydroxyestran-7α-yl)butanoic acid ( 9 ) and 7α-(4-aminobutyl)-3β,17β-estradiols ( 13 ), were prepared from 19-nortestosterone by partial synthesis. The binding activity for the cytosol estrogen receptor was determined by competition against [3H]-estradiol; at a concentration of 2×10?7mol/l, compound 9 displaces 50% of [3H]-estradiol. Attached to AH-Sepharose 4B compound 9 allows the cytosol estrogen receptor from calf uterus to be concentrated 1800-fold by affinity chromatography.  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