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   602516篇
  免费   38815篇
  国内免费   1338篇
耳鼻咽喉   7911篇
儿科学   19539篇
妇产科学   15675篇
基础医学   96829篇
口腔科学   16544篇
临床医学   51541篇
内科学   113000篇
皮肤病学   13999篇
神经病学   44311篇
特种医学   21901篇
外国民族医学   83篇
外科学   89558篇
综合类   10098篇
一般理论   165篇
预防医学   44096篇
眼科学   13537篇
药学   47829篇
  3篇
中国医学   1510篇
肿瘤学   34540篇
  2019年   4924篇
  2018年   6801篇
  2017年   5069篇
  2016年   5591篇
  2015年   6245篇
  2014年   8375篇
  2013年   12951篇
  2012年   17373篇
  2011年   18957篇
  2010年   11363篇
  2009年   10447篇
  2008年   17816篇
  2007年   19024篇
  2006年   19079篇
  2005年   18289篇
  2004年   18314篇
  2003年   17508篇
  2002年   17402篇
  2001年   27396篇
  2000年   28394篇
  1999年   23275篇
  1998年   6471篇
  1997年   5527篇
  1996年   5789篇
  1995年   5361篇
  1994年   4947篇
  1992年   17368篇
  1991年   17929篇
  1990年   17797篇
  1989年   17129篇
  1988年   15805篇
  1987年   15535篇
  1986年   14707篇
  1985年   13954篇
  1984年   10346篇
  1983年   8908篇
  1982年   4989篇
  1979年   9958篇
  1978年   7252篇
  1977年   6125篇
  1976年   5925篇
  1975年   6807篇
  1974年   8104篇
  1973年   7570篇
  1972年   7360篇
  1971年   7060篇
  1970年   6503篇
  1969年   6235篇
  1968年   5879篇
  1967年   5302篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
91.
The authors suggest additional criteria evidencing inflammations in the gallbladder and colloid stability of the bile: bile acid absorption and cholesterol sedimentation coefficients. Derivation of these coefficients is based on biochemical examination of the bile with measurements of bile acid, cholesterol, and bilirubin concentrations in both portions. The results of examinations of 99 subjects evidence the diagnostic value and specificity of the characteristics, and availability of this method for clinical practice.  相似文献   
92.
The postnatal evolution of depolarizing after-potentials (DAPs) and after-hyperpolarizations (AHPs) was studied in rat CA1 hippocampal neurones (5-68 days of age) using in vitro slices. Results were pooled into 4 age groups: P5-9, P10-16, P17-24 and P26-68. In P5-9 cells, DAPs were seen as passive signals, with a time constant similar to the time constant of the membrane. The evolution of the DAP was characterized by a decrease in amplitude, an increase in duration and a change in contour. In P10-16 and P17-24 cells, the DAPs often had a plateau or a hump-like shape which increased the probability of firing and the occurrence of spike doublets. The firing pattern and bursting behaviour of P10-16 CA1 neurones differed from the pattern typical of the adult. P5-9 and P10-16 cells had post-burst AHPs with a smaller amplitude and a more prolonged early phase than at late stages of development.  相似文献   
93.
The concentrations of beta-endorphin and cholecystokinin were measured in fresh resting peripheral mononuclear cells obtained from rats and human subjects in basal conditions and after different pharmacological treatments. Both in the human and the rat, beta-endorphin concentrations in mononuclear cells, increased after treatment with serotoninergic agonists, decreased after dopaminergic or GABAergic drugs, while the respective antagonists exerted the opposite effect. In vitro, serotoninergic and GABAergic compounds confirmed their roles in the modulation of beta-endorphin in mononuclear cells. Cholecystokinin was never affected by the pharmacological treatments.  相似文献   
94.
BACKGROUND AND PURPOSE: The familial occurrence of intracranial aneurysms and cervical artery dissections has been described in different families and supports the hypothesis that a primary arteriopathy may play a role in the pathogenesis of these disorders. Although the basis for this arteriopathy is generally not believed to be similar among cases of intracranial aneurysms and cervical artery dissections, several similarities exist in the epidemiology of these disorders and a common underlying arterial abnormality may be suspected. SUMMARY OF REPORTS: The medical records of all 175 patients with spontaneous dissections of the cervical arteries who were seen at the Mayo Clinic between 1970 and 1989 were reviewed to identify families in which intracranial aneurysms and cervical dissections coexisted. Three families were identified in which intracranial aneurysms and cervical artery dissections were observed among siblings. These families are described in detail. CONCLUSIONS: The familial occurrence of intracranial aneurysms and cervical artery dissections within the same families provides support to the importance of a common underlying arteriopathy in the pathogenesis of both these disorders. The underlying vascular defect may, at least in some cases, be inherited.  相似文献   
95.
We studied two patients which showed a paralysis of the oculomotor nerve on one side and isolated paralysis of the superior rectus on the other side. On the side of oculomotor nerve paralysis, midbrain infarct extending from the paramedian tegmentum to crus cerebri was demonstrated in one case who showed no recovery, and a small lacuna in midbrain tegmentum in another one who showed complete recovery. On the side of isolated paralysis of the superior rectus, no lesion was demonstrated by CT and MRI, and no clinical signs of the involvement of fiber tracts or nuclei were evident in both cases. A unilateral lesion of oculomotor nerve nucleus caused a paralysis of the contralateral superior rectus.  相似文献   
96.
The involvement of excitatory amino acid (EAA) receptors in mediation of the toxic effects of cocaine was studied in male ICR mice. Cocaine HCl (90 mg/kg, IP) induced seizures in 95% and death within 24 h in 68% (n = 135) of the animals. There was a significant correlation (r = .54) between the time to onset of convulsions and the time to death in mice which died within 30 min of injection (n = 84). Pretreatment with selected EAA receptor antagonists 15 min prior to cocaine differentially blocked cocaine toxicity. Selective N-methyl-D-aspartic acid (NMDA) receptor antagonists (MK-801, dextrorphan, CPP) decreased both the incidence of seizures and mortality. A nonselective EAA antagonist, kynurenic acid, decreased lethality in doses which did not reduce convulsions. A similar action was observed following pretreatment with the selective kainic acid/AMPA receptor antagonist, GDEE. Antagonists at EAA receptors can provide significant protection against cocaine-induced toxicity. Moreover, the data provide evidence for the involvement of both NMDA and non-NMDA receptor subtypes in aspects of cocaine toxicity.  相似文献   
97.
Oncologic screenings of the populations in the areas with increased incidence of esophageal cancer have revealed Barrett's ulcer in 1 percent of the examinees. Endoscopic and cytologic characteristics of this condition are presented. Precancer changes--severe dysplasia--are most frequent in male Kazakhs (14.1 percent) aged 50 to 59 (14.7 percent). Subjects with Barrett's ulcer developing severe dysplasia, as evidenced by cytograms, should be included in the group of subjects at risk for carcinoma of the lower third of the esophagus and cardia.  相似文献   
98.
99.
100.
Rat brain hippocampal slices were incubated with or without the convulsant 4-aminopyridine (4-AP). From these slices a crude mitochondrial/synaptosomal membrane fraction was prepared and analyzed for endogenous protein phosphorylation. 4-AP (10(-5) M) stimulated the phosphorylation of a 50 kDa protein by 86%. The phosphorylation of this 50 kDa protein is Ca2+/calmodulin-dependent and we suggest that this protein is the lower molecular weight subunit of Ca2+/calmodulin-dependent protein kinase II (CaMK II).  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