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   32382篇
  免费   1614篇
  国内免费   145篇
耳鼻咽喉   421篇
儿科学   574篇
妇产科学   570篇
基础医学   4320篇
口腔科学   1171篇
临床医学   2525篇
内科学   7589篇
皮肤病学   797篇
神经病学   2496篇
特种医学   1305篇
外科学   5317篇
综合类   219篇
一般理论   2篇
预防医学   995篇
眼科学   514篇
药学   2184篇
中国医学   46篇
肿瘤学   3096篇
  2021年   611篇
  2020年   284篇
  2019年   428篇
  2018年   606篇
  2017年   429篇
  2016年   476篇
  2015年   563篇
  2014年   743篇
  2013年   834篇
  2012年   1310篇
  2011年   1420篇
  2010年   774篇
  2009年   738篇
  2008年   1285篇
  2007年   1351篇
  2006年   1387篇
  2005年   1411篇
  2004年   1370篇
  2003年   1317篇
  2002年   1318篇
  2001年   1222篇
  2000年   1387篇
  1999年   1203篇
  1998年   397篇
  1997年   281篇
  1996年   305篇
  1995年   276篇
  1994年   239篇
  1993年   226篇
  1992年   795篇
  1991年   753篇
  1990年   677篇
  1989年   697篇
  1988年   674篇
  1987年   663篇
  1986年   675篇
  1985年   601篇
  1984年   428篇
  1983年   350篇
  1979年   340篇
  1978年   233篇
  1977年   200篇
  1975年   199篇
  1974年   226篇
  1973年   207篇
  1972年   197篇
  1971年   209篇
  1970年   203篇
  1969年   224篇
  1968年   174篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
We have found that steroid bolus withdrawal prior to graft reperfusion increased the incidence of acute cellular rejection (ACR). This study aims to clarify how initial steroid bolus (ISB) injection at reperfusion influences the kinetics of CD8(+) alloreactive immune responses immediately after living donor liver transplantation (LDLT). A total of 49 hepatitis C virus (HCV)-infected recipients were classified into 3 groups according to hierarchical clustering by preoperative CD8(+)CD45 isoforms. The naive T cell proportion was considerably higher in Group I than in Groups II and III, whereas Group II recipients had the highest effector memory (EM) T cells and Group III the highest effector T cells. The frequency of ACR was significantly higher in recipients without ISB than in those with ISB. In particular, the ACR rates were the highest in Group II without ISB. Following ISB, the proportion of effector T cells was promptly upregulated within 6 hours after graft reperfusion, simultaneously with the upregulation of CD27(-)CD28(-) subsets, interferon-gamma (IFN-gamma), tumor necrosis factor-alpha and perforin expression, which significantly correlated with increasing interleukin (IL)-12 receptor beta 1 cells. These were then downregulated to below preoperative levels by tacrolimus (Tac) administered at 24 hours. These changes did not occur in the absence of ISB. In Group II without ISB, the downregulation of IL-12Rbeta1(+) cells was the greatest, consistent with the highest rates of ACR and mortality (60%). In conclusion, ISB must be done in place, especially in Group II with preexisting high EM T cells, to enable the development of early allograft acceptance.  相似文献   
24.
25.
26.
Suda  J; Eguchi  M; Akiyama  Y; Iwama  Y; Furukawa  T; Sato  Y; Miura  Y; Suda  T; Saito  M 《Blood》1987,69(2):508-512
A male neonate with Down's syndrome and congenital myeloproliferative disorder was studied. His blood picture showed the unique coexistence of leukocytosis with matured cells and a large number of blast cells. The in vitro proliferation and differentiation of blast cells into various lineages in the presence of phytohemagglutinin-stimulated leukocyte conditioned medium (PHA-LCM) was examined by using a liquid culture and a methylcellulose culture system. The differentiation of blast cells into myeloid cells was confirmed by specific cytochemical stainings, electron microscopy, and an immunologic study. No specific factors in the plasma of the patient promoted the proliferation or differentiation of blast cells. The cellular composition of colonies grown in methylcellulose culture from single blast cells was studied by a micromanipulation technique. High plating efficiency was observed. Of 136 cultures, 78 showed colony growth. Half of the blast cells were colony-forming cells that could proliferate and differentiate into basophils, neutrophils, eosinophils, macrophages, and erythrocytes in the presence of PHA-LCM. Using the blast cells with a high differentiation capacity to the basophil pathway, we studied the effect of recombinant granulocyte-macrophage colony-stimulating factor (GM- CSF). Recombinant GM-CSF support neutrophils, eosinophils, and macrophages but not typical basophils. These findings of the cell differentiation of blast cells into various kinds of cells in vitro were in agreement with the finding of neutrophilia, eosinophilia, basophilia, and thrombocythemia in this patient.  相似文献   
27.
N Sato 《Nihon Geka Gakkai zasshi》1986,87(12):1511-1525
The relationship between nutritional status and muscle strength was examined in 73 patients with gastrointestinal carcinoma preoperatively. Nutritional status was assessed by measuring various nutritional parameters. Muscle strength was determined by measurements of %grip strength and respiratory muscle strength expressed as %maximal expiratory and inspiratory pressure (%MEP and %MIP). The results were as follows: %GS was significantly low in the patients who showed low values in body weight (%ideal body weight: %IBW), mid-arm muscle circumference (%AMC), serum albumin (Alb), serum prealbumin (PA), total peripheral lymphocyte count (TLC), and/or nutritional surgical risk index (NRI). %MEP was significantly low in the patients who showed low values in %IBW, %AMC, triceps skin fold, Alb, PA, retinol binding protein, NRI, and/or nutritional assessment index (NAI). %MIP was significantly low in the patients who showed low values in %IBW, %AMC, creatinine height index, Alb, PA, NRI, and/or NAI. %MEP and %MIP were significantly correlated with %GS. Preoperative %GS value was significantly low in the esophageal cancer patients with postoperative pulmonary complications. It was suggested that %GS was a simple and useful nutritional parameter for detecting depletion of the muscle mass and visceral proteins, for respiratory muscle strength, and for functional capacity of muscle.  相似文献   
28.
Cellular electrophysiological effects of membrane lipid peroxidation by t-butyl hydroperoxide (TBH) were studied in the rabbit sinoatrial (SA) node. Superfusion for 1-5 min with 300 microM TBH caused an initial increase and subsequent decrease in the spontaneous firing frequency of the SA node. Voltage clamp experiments revealed that TBH initially enhanced but later blocked the Ca2+ current. Thus, membrane lipid peroxidation appears to accelerate and then suppress physiological automaticity by causing biphasic changes in the Ca2+ current.  相似文献   
29.
Ca-antagonistic activities of cerebral vasodilators, nicardipine and 1-(3,4-dimethoxyphenyl)-2-(4-diphenylmethylpiperazinyl)ethanol dihydrochloride (NC-1100) were tested on basilar and renal arteries, thoracic aorta and portal vein of rabbit, and rat vas deferens. Both the cerebral vasodilators used herein had a selectivity to basilar arteries. The selectivity to the basilar arteries is considered to be one of the factors in deciding the pharmacological property of the cerebral vasodilators.  相似文献   
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