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   1077606篇
  免费   71941篇
  国内免费   1372篇
耳鼻咽喉   15022篇
儿科学   34715篇
妇产科学   28658篇
基础医学   153805篇
口腔科学   29605篇
临床医学   95136篇
内科学   204349篇
皮肤病学   24439篇
神经病学   81765篇
特种医学   43039篇
外国民族医学   201篇
外科学   163453篇
综合类   21727篇
现状与发展   1篇
一般理论   263篇
预防医学   74696篇
眼科学   24568篇
药学   86311篇
  7篇
中国医学   2805篇
肿瘤学   66354篇
  2019年   7802篇
  2018年   11345篇
  2017年   8945篇
  2016年   10137篇
  2015年   11309篇
  2014年   15309篇
  2013年   22274篇
  2012年   30666篇
  2011年   32447篇
  2010年   19031篇
  2009年   17884篇
  2008年   30079篇
  2007年   32182篇
  2006年   32834篇
  2005年   31172篇
  2004年   29879篇
  2003年   28681篇
  2002年   27682篇
  2001年   60087篇
  2000年   61543篇
  1999年   51003篇
  1998年   12487篇
  1997年   11028篇
  1996年   11043篇
  1995年   10348篇
  1994年   9359篇
  1993年   8879篇
  1992年   37842篇
  1991年   36338篇
  1990年   35818篇
  1989年   34360篇
  1988年   30949篇
  1987年   30038篇
  1986年   28251篇
  1985年   26482篇
  1984年   19236篇
  1983年   16129篇
  1982年   8829篇
  1979年   17052篇
  1978年   11418篇
  1977年   10252篇
  1976年   8852篇
  1975年   10085篇
  1974年   11663篇
  1973年   11286篇
  1972年   10765篇
  1971年   10101篇
  1970年   9262篇
  1969年   8944篇
  1968年   7926篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Adult rats were exposed to 1 ppm (1.96 mg/m3) ozone or air for 2 wk. Animals were sacrificed at 3, 5, 7, or 14 d after the onset of exposure, and samples of plasma and lung lavage were obtained. Heat-inactivated plasma and lavage from animals exposed to ozone for 5 or 7 d significantly increased DNA synthesis by lung pneumocytes compared with plasma or lavage from air-exposed animals. Fractionation of plasma and lavage samples indicated that the factor responsible had an isoelectric point of 6.45-6.75, and a molecular weight of 38 +/- 3 kDa. This factor has a dose-dependent effect on lung pneumocyte DNA synthesis in culture. It has no effect on cultured fibroblast DNA synthesis, and is distinct from a previously described factor in the plasma of these ozone-exposed animals that enhances fibroblast DNA synthesis. The factor is detectable within 5 d of exposure, and may hold some promise as a marker of early oxidant lung injury.  相似文献   
992.
The impairment of the functions of red blood cells or their destruction during storage can be delayed or even inhibited by oligoamines especially RE 1492 (N,N',N'-Tris-(4-phenylbutyl)benzene-1,3,5-trimethanamine). When citrated whole blood (WB) is stored at 4 degrees C for 7 d half of the red blood cells (RBC) have lost their ability to form rouleaux. Addition of 100 mumols/L RE 1492 maintains 50% reaggregability up to day 28th of storage. When citrated WB is stored at 37 degrees C the reaggregability has declined to 40 percent after 10 h. With 100 mumols/L RE 1492 no reduction of this property is observed up to 48 h. These results are correlated with the maintainance of the discocyte form of RBC and a persistent filtrability of RBC suspensions through a 5 microns microporous membrane. With 100 mumols/L RE 1492 only one fifth of the haemolysis of untreated WB occurs. The efflux of potassium ions from RBC into the blood plasma during a 72 h storage is bisected by RE 1492. The binding of oxygen to RBC remains unchanged.  相似文献   
993.
994.
Trazodone hydrochloride is an oral antidepressant agent which has been associated with the improvement of erections in impotent men and the development of prolonged erections or priapism in potent men. An in vivo study in animal and human subjects was performed to gain experience with the effect of intracavernosal trazodone. In the anesthetized New Zealand White rabbit, intracavernosal trazodone or its major metabolite m-chlorophenylpiperazine (m-CPP) produced full penile erection in 76% and 84% of animals studied respectively with doses ranging from one to 15 mg. On the other hand, intracavernosal administration of five mg. papaverine resulted in a prolonged erection in 90% of animals studied. In 13 selected volunteer patients, intracavernosal trazodone caused tumescence but not full penile erection with corporal body pressures of 28.2 +/- 5.8 mm. Hg. Intracavernosal papaverine or papaverine and phentolamine in these subjects resulted in significantly higher corporal body pressures of 58 +/- 18 mm. Hg (p less than .05). Intracavernosal administration of alpha adrenoceptor agonists but not normal saline resulted in complete detumescence of trazodone- or m-CPP-induced prolonged erection in the animal studies. Intracavernosal trazodone results in erectile activity that appears in part based on its local alpha blocking activity but like other intracavernosal alpha-blocking agents is not as effective in initiating penile erections as are intracavernosal agents that directly induce smooth muscle relaxation.  相似文献   
995.
996.
997.
We evaluated a commercially available polyclonal antibody to 17 beta-estradiol as the basis for an estrogen receptor (ER) assay of breast carcinoma in formalin-fixed paraffin tissues and then compared it with both the ER-ICA antibody in serial paraffin sections and the biochemical assay of corresponding fresh tissue. Using the estradiol antibody, 49 of 50 cases showed some cytoplasmic staining; 38 cases had nuclear staining. Sensitivity and specificity for different proportions of positive nuclear and cytoplasmic staining were calculated using receiver-operator characteristic curves. The optimum correlation with the biochemical assay was obtained with nuclear staining alone. Greater than 30% nuclear positivity as a cut-off point yielded a sensitivity of 76% and a specificity of 82%. The corresponding ER-ICA values in 38 cases yielded a sensitivity of 93% and a specificity of 56%. The methodology for the ER-ICA assay was more technically demanding in paraffin sections than that of the estradiol antibody and considerably more expensive. This study is the first to show that with nuclear staining only, and not cytoplasmic staining, as the parameter of positivity, the immunocytochemical assay of ER with anti-17 beta-estradiol antibody in routinely processed, formalin-fixed, archival material is an accurate and specific method for the determination of the ER status of breast carcinoma.  相似文献   
998.
999.
A case of Beh?et disease associated with aortic valve regurgitation treated with aortic valve replacement is reported. The patient was treated successfully with special surgical techniques for prevention of post operative paravalvular leakage and occurrence of pseudo aneurysm because the patient was under long-term steroid therapy for Beh?et disease.  相似文献   
1000.
Chronic alcohol treatment induces a variety of effects on the metabolism of neurotransmitters and the function of their receptors. Recent studies on alcohol dependence and/or functional tolerance to alcohol have clearly demonstrated that neurotransmitter-gated and receptor-coupled ion channels, as well as neurotransmitter receptor coupled with intracellular mediator systems, such as phosphatidylinositides and cyclic nucleotide-generating systems, are invariably suppressed during alcohol dependence. Future studies on the central actions of alcohol and on alcohol dependence should therefore be directed at the molecular changes in synaptic membrane-bound components such as neurotransmitter receptors, as well as on neurotransmitter release and relevant membrane-bound enzymes.  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