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   705799篇
  免费   48957篇
  国内免费   1307篇
耳鼻咽喉   9168篇
儿科学   23275篇
妇产科学   17603篇
基础医学   110390篇
口腔科学   19956篇
临床医学   63750篇
内科学   134329篇
皮肤病学   16159篇
神经病学   49437篇
特种医学   25737篇
外国民族医学   76篇
外科学   104474篇
综合类   14833篇
现状与发展   2篇
一般理论   160篇
预防医学   51392篇
眼科学   16320篇
药学   53955篇
  3篇
中国医学   2371篇
肿瘤学   42673篇
  2021年   5434篇
  2018年   7860篇
  2017年   6107篇
  2016年   6822篇
  2015年   7548篇
  2014年   10260篇
  2013年   15380篇
  2012年   20494篇
  2011年   21483篇
  2010年   12716篇
  2009年   11929篇
  2008年   19984篇
  2007年   21502篇
  2006年   21895篇
  2005年   20432篇
  2004年   19982篇
  2003年   18938篇
  2002年   18448篇
  2001年   36325篇
  2000年   36894篇
  1999年   30377篇
  1998年   7875篇
  1997年   6662篇
  1996年   6969篇
  1995年   6627篇
  1994年   6096篇
  1993年   5589篇
  1992年   22967篇
  1991年   22924篇
  1990年   22309篇
  1989年   22076篇
  1988年   20035篇
  1987年   19417篇
  1986年   18467篇
  1985年   17305篇
  1984年   12697篇
  1983年   10741篇
  1982年   5921篇
  1979年   11518篇
  1978年   8128篇
  1977年   6832篇
  1976年   6594篇
  1975年   7268篇
  1974年   8498篇
  1973年   8141篇
  1972年   7658篇
  1971年   7127篇
  1970年   6877篇
  1969年   6306篇
  1968年   5780篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
Summary A case of bilateral congenital pseudarthrosis of the clavicle in a baby boy is described. The patient is fully asymptomatic, and no functional impairment is present. This is probably only the seventh case described of this rare congenital anomaly.  相似文献   
53.
Regional effects of craniotomy on cerebral circulation and metabolism, such as regional cerebral blood flow (rCBF), regional cerebral oxygen consumption (rCMRO2), regional oxygen extraction fraction (rOEF), and regional cerebral blood volume (rCBV) were examined by a PET (positron emission tomography) study concerning surgery that was performed on unruptured aneurysm patients. Eight patients with intracranial un-ruptured aneurysms were studied pre- and post-operatively by the 15O labelled-gas steady-state method, using HEADTOME-III. All patients underwent aneurysmal surgery performed by the transsylvian approach. There was a significant increase in the mean OEF values taken from the whole-brains of 8 patients, but there was not a significant change in CBF, CMRO2 or CBV. The increase in OEF was caused by decrease of O2 content, which was caused by post-operative decrease in the Hb value. So, this OEF increase was not the direct effect of craniotomy. In 2 patients, the rCBF and rCMRO2, in the fronto-temporal region (where craniotomy was performed) increased post-operatively. This regional effect suggests transient reactive hyperemia following compressive ischemia during the operative procedure, and metabolic demands for recovery of brain function. In 2 other patients, who had relatively low rCBFs during the pre-operative study, rCBF and rCMRO2 in the bi-frontal region had decreased more at the post-operative study. This change appears to have been caused by removal of cerebrospinal fluid and depression of the frontal lobe. From this study, it becomes evident that the regional effect of craniotomy on cerebral circulation and metabolism is not so great, when adequate microsurgical techniques are used.  相似文献   
54.
In the present study, we examined the effect of CsA on the in vitro production of Ig and on the in vitro production of molecules known to have B-cell growth and differentiation activities, such as IL-6 and sCD23. For the purpose of this study, we developed an experimental In vitro system closely resembling an In vivo model of ongoing B-cell activation. Pre-activated B cells proliferated and produced IgM optimally when they were re-cultured in the presence of IL-2/IL-6. CsA down-regulated the IL-2/IL-6-induced proliferative responses of pre activated B cells by at least 50%., but it up-regulated IgM production in the same experiments. This up regulating effect was not cytokine-related since it was also seen when cells were re-cultured in the absence of any cytokines. Optimal release of sCD23 was observed when SAC-pre-activated B cells were re cultured in the presence of IL-4 or IL-4 plus IL-2 and CsA up-regulated significantly the release of this molecule in these cultures. Finally, CsA was shown to inhibit PHA-induced cell proliferation of PBMC and to up-rcgulate IL-6 production in the same cultures. We conclude that CsA can amplify in vitro both the production of Ig and the release of sCD23 by pre activated B cells. This finding, in combination with the CsA-induced up-regulation of lectin-induced IL-6 production, may have clinical implications in disease states with an ongoing immune activation, where prolonged administration of CsA might be anticipated.  相似文献   
55.
To investigate the role of cell-mediated immunity (CMI) in glomerulonephritis (GN), we identified the infiltrating immune cells both within the glomerulus and in the interstitium. Frozen sections from 103 patients with various forms of GN: 10 with minor glomerular abnormality (MGA) as control, 10 with minimal change nephrotic syndrome (MCNS), 10 with membranous nephropathy (MN), 9 with focal glomerulosclerosis (FGS), 30 with IgA nephropathy (IgAN), 22 with acute post streptococcal glomerulonephritis (APSGN), and 2 with rapidly progressive glomerulonephritis (RPGN) were examined using monoclonal antibodies (MoAb) by indirect immunoalkaline-phosphatase labelling. In most glomerulonephritis, monocyte/M phi and helper/inducer T cells were predominantly infiltrating in the interstitium, but intraglomerular infiltration was rare, except for APSGN. This interstitial infiltration increased proportionally to the level of serum creatinine, and was most prominent in RPGN. Apparently different distribution was seen in APSGN, that is, prominent increase in total number of intra-glomerular monocyte/M phi infiltration with slightly increased T cells. The change was correlated with time after onset; namely the more leucocytic infiltration was observed when the tissue was taken earlier. These data suggest that in APSGN, monocyte/M phi accumulate in glomeruli via cell mediated immunity in addition to humoral immune mechanism resulting in glomerular hypercellularity, whereas in most chronic glomerulonephritis interstitial leucocyte infiltration, particularly helper T cells and monocyte/M phi may play an important role in the progression of glomerulonephritis.  相似文献   
56.
In experiments on albino rats it was established that three administrations of indomethacin in a dose of 0.01 g/kg body weight induced a severe damage of the liver characterized by disturbances of hepatocytic membranes, bile-producing and protein-producing functions of the liver, an enhancement of lipid peroxidation, a decrease of reduced glutathione pool. Antioxidants (tocopherol acetate, essentiale, legalon, flacumin) limit manifestations of indomethacin, hepatotoxicity, as a result of which tha functional-biochemical disorders in the liver show up to a lesser degree. During the combined use of antioxidants in indomethacin-induced lesions of the liver their hepatoprotective activity increases.  相似文献   
57.
58.
A chemically defined medium for the culture of mature oligodendrocytes   总被引:3,自引:0,他引:3  
A new chemically defined medium consisting of equal parts of Dulbecco modified Eagle's and Ham's F-12 media supplemented with insulin, sodium selenite, putrescine, and D+ galactose, which allows the long-term survival of mature oligodendrocyte pure cultures, is described. Immunohistochemical staining has shown that over 90% of the cells become positive for myelin proteins shortly following subculture. Contaminating astrocytes (2%) do not survive in this medium. Biochemical data have indicated that these purified oligodendrocytes express 2'3'-cyclic nucleotide 3'-phosphohydrolase and UDP-galactose ceramide galactosyltransferase activities. Electron microscopical examination revealed that the oligodendrocytes were mostly of medium-dark type and appeared to be identical to cells cultured in serum-containing medium. The ability to maintain pure oligodendrocyte cultures in such a defined medium will allow investigations concerning exogenous and endogenous factors involved in oligodendrocyte metabolism.  相似文献   
59.
Zolpidem and alpidem, two imidazopyridines with high affinity for the type I benzodiazepine recognition site, have recently been proposed as preferential hypnotic (zolpidem) and anxiolytic (alpidem) drugs notable for the minor incidence of side-effects. To further characterize the molecular mechanism involved in the action of these drugs, we studied their effects in comparison with those of diazepam on the spontaneous electrical activity of substantia nigra pars reticulata (SNR) neurons. These cells have been shown to be extremely sensitive to various positive and negative modulators of GABAergic transmission. All three drugs consistently produced a dose-dependent (0.03-8.0 mg/kg i.v.) inhibition of the firing of SNR cells when administered as a single bolus. However, zolpidem was more potent and efficacious than diazepam or alpidem. The ID50s were 0.076, 0.492 and 0.821 mg/kg, respectively. When the drugs were injected in exponentially (ratio 2) increasing doses up to 8.0 mg/kg, the rank order for tachyphylaxis was zolpidem much greater than diazepam greater than alpidem. Since the effects of the drugs were abolished and prevented by a small dose (0.5 mg/kg i.v.) of flumazenil (Ro 15-1788), it is likely that the effects were mediated through activation of benzodiazepine receptors. The results indicate that the hypnotic, zolpidem, has a more potent inhibitory action on SNR cell activity than the anxiolytics, alpidem and diazepam.  相似文献   
60.
The effects of FUT-187 (6-amidino-2-naphthyl 4-[(4,5-dihydro-1H-imidazol-2-yl)amino]benzoate dimethanesulfonate, CAS 103926-82-5), a novel synthetic protease inhibitor, were examined in experimental rat and canine models of pancreatitis. 1. FUT-187 significantly increased the survival of rats with trypsin- and phospholipase A2-induced pancreatitis in a dose-dependent manner (10-100 mg/kg, p.o.). 2. FUT-187 decreased plasma enzymatic activity reflecting the degree of pancreatitis in rats with ethionine-induced pancreatitis, and showed a tendency to ameliorate histopathological changes in the pancreas (10-100 mg/kg p.o.). 3. FUT-187 (10 mg/kg) produced an obvious improvement of various biochemical parameters of pancreatitis and also reduced histopathological changes in the pancreas in animals with experimental pancreatitis produced by the closed duodenal loop method. In addition, FUT-187 significantly increased the survival of dogs when given by direct administration into the lumen of the closed duodenal loop. The therapeutic effects of FUT-187 in experimental pancreatitis were nearly equal in most instances to those of camostat mesilate. Thus, FUT-187 would appear to be an effective new agent for the treatment of pancreatitis.  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