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   58911篇
  免费   4706篇
  国内免费   156篇
耳鼻咽喉   532篇
儿科学   1552篇
妇产科学   1123篇
基础医学   7762篇
口腔科学   1072篇
临床医学   6590篇
内科学   11130篇
皮肤病学   824篇
神经病学   5031篇
特种医学   2301篇
外科学   9655篇
综合类   838篇
一般理论   58篇
预防医学   6120篇
眼科学   1360篇
药学   4241篇
  1篇
中国医学   61篇
肿瘤学   3522篇
  2023年   329篇
  2022年   460篇
  2021年   1184篇
  2020年   680篇
  2019年   1114篇
  2018年   1350篇
  2017年   990篇
  2016年   1062篇
  2015年   1286篇
  2014年   1855篇
  2013年   2607篇
  2012年   3981篇
  2011年   4084篇
  2010年   2183篇
  2009年   1963篇
  2008年   3556篇
  2007年   3821篇
  2006年   3718篇
  2005年   3631篇
  2004年   3395篇
  2003年   3204篇
  2002年   3007篇
  2001年   906篇
  2000年   861篇
  1999年   855篇
  1998年   675篇
  1997年   529篇
  1996年   505篇
  1995年   543篇
  1994年   453篇
  1993年   420篇
  1992年   565篇
  1991年   496篇
  1990年   519篇
  1989年   486篇
  1988年   447篇
  1987年   395篇
  1986年   394篇
  1985年   443篇
  1984年   394篇
  1983年   324篇
  1982年   268篇
  1981年   244篇
  1980年   224篇
  1979年   259篇
  1978年   247篇
  1976年   199篇
  1974年   224篇
  1973年   201篇
  1972年   203篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
Primary dystonia is a disorder of movement for which no consistent pathophysiology has been identified; in the absence of evidence to the contrary, it is assumed to be cognitively benign. We have studied a clinically heterogeneous group of 14 patients with primary dystonia on a battery of neuropsychological tests. Despite well-preserved speed of information processing, language, spatial, memory and general intellectual skills relative to normal controls, we have identified a constellation of attentional-executive cognitive deficits on the Cambridge Neuropsychological Test Automated Battery (CANTAB). Specifically, patients demonstrated significant difficulties negotiating the extra-dimensional set-shifting phase of the IED task. The implications of these findings for the pathophysiology of primary dystonia are discussed. This is, to the best of our knowledge, the first report of a significant cognitive deficit in patients with primary dystonia.  相似文献   
92.
Thiopurine methyltransferase (TPMT) catalyses the S-methylation of thiopurine drugs such as 6-mercaptopurine (6-MP). TPMT activity in the human red blood cell (RBC) is controlled by a common genetic polymorphism. Gene frequencies for this polymorphism are such that approximately one in 300 subjects is homozygous for the allele for low activity and lacks RBC TPMT activity, 11% of subjects are heterozygous and have intermediate levels of enzyme activity and 89% are homozygous for the allele for high activity. Our experiments were performed to determine whether the properties of TPMT in an important human drug metabolizing organ, the liver, were similar to those of RBC TPMT and to test the hypothesis that the genetic polymorphism which controls TPMT activity in the human RBC might also regulate the level of this enzyme activity in hepatic tissue. Human liver TPMT is a cytoplasmic enzyme and the Km values for 6-MP and S-adenosyl-L-methionine, cosubstrates for the reaction, were 580 microM and 2.7 microM, respectively. These properties, as well as the sensitivity of human liver TPMT to a panel of methyltransferase inhibitors, were similar to those of RBC TPMT. The enzyme activity was then measured in 119 surgical biopsy samples of hepatic tissue. Average hepatic TPMT activity was 13.6% higher in samples from male than in those from female patients. Frequency distribution histograms demonstrated the presence of a subgroup with intermediate enzyme activity that included 8.4% of samples. In addition, when TPMT activity was measured in both RBCs and hepatic tissue for 35 patients, those with inherited intermediate levels of RBC TPMT activity also had intermediate hepatic enzyme activity. Finally, ion exchange chromatography demonstrated the presence of two isozymes of TPMT in human hepatic tissue, but the isozymes did not appear to explain the molecular mechanism responsible for the genetic polymorphism. These results were compatible with the conclusion that the genetic polymorphism which controls TPMT activity in the RBC also controls levels of this important enzyme activity in a major human drug metabolizing organ, the liver.  相似文献   
93.
STUDY OBJECTIVE--The aim was to investigate the association between reproductive, contraceptive, and menstrual factors and risk of benign ovarian tumours. DESIGN AND SETTING--This was a case-control study carried out in six London Hospitals. An interviewer administered questionnaire was used. SUBJECTS--62 women with a benign epithelial ovarian neoplasm, 37 women with a functional ovarian cyst, and 20 women with a dermoid cyst presenting between 1983 and 1985, together with 132 controls, took part in the study. MAIN RESULTS--On average, women with a benign epithelial ovarian neoplasm were older than those with a functional ovarian cyst, who in turn were older than those with a dermoid cyst. Nulliparity and infertility were associated with an increased risk, and multiparity with a reduced risk, of benign epithelial ovarian neoplasms. Infertility and pelvic inflammatory disease were associated with increased risks of functional and dermoid cysts. Recent use of oral contraceptives was associated with a reduced risk of all three tumour types. CONCLUSIONS--The findings suggest that the aetiology of ovarian cysts and benign epithelial ovarian neoplasms may differ. The aetiology of benign and malignant epithelial ovarian neoplasms may be similar, however, since some risk factors are shared.  相似文献   
94.
两项新的研究显示,在心房颤动的药物治疗方面控制心率不仅与控制心律的疗效及操作相当,而且更加经济、安全。因而我们可以推测由于药物控制心率副作用较少,可能会降低心房颤动患者的住院率。  相似文献   
95.
The proteins present in 4% polyethylene glycol (PEG) precipitates of 10 normal sera and 60 samples from patients with rheumatic diseases were studied. A variety of immunochemical methods were used, including estimation of the percentages of total serum proteins precipitated by PEG, gel filtration analyses of the precipitates, and affinity chromatography with protein A and anti-immunoglobulin columns. Substantial amounts of protein were precipitated from normal sera. Many non-immunoglobulin proteins were precipitated from patients' sera, including fibronectin, haptoglobin, albumin, transferrin, and alpha 1-antitrypsin. Affinity chromatography with anti-immunoglobulin columns bound non-immunoglobulin proteins from PEG precipitates, but the protein A affinity column did not do so. The view that circulating antibody-antigen complexes alone are precipitated by 4% PEG is too simplistic; many non-immunoglobulin proteins are involved. They may either bind to immune complexes or be coprecipitated owing to non-specific protein aggregation.  相似文献   
96.
97.
Thirty C57BI mice were randomized into two groups. Group 1 served as controls while Group 2 was given 10% V/V ethanol with the drinking water. Whole blood- associated acetaldehyde (WBAA) was measured on capillary blood samples using a fluorigenic high performance chromatographic assay. WBAA peaked at Day 2. A stable mean plateau of 263 +/- 71 SD with a range of 160-400 nmoles/g hemoglobin WBAA was found in the group consuming ethanol compared with 122 +/- 17 SD and a range of 88-150 nmoles/g hemoglobin for controls (p less than 0.001). When ethanol was discontinued, levels of WBAA declined and became similar to those of controls by 9 days following cessation of ethanol. The quantitative difference between ethanol-consuming and control animals and also the rapid rise of whole blood-associated acetaldehyde and the relatively slow decline following cessation of ethanol intake indicate that such a test might be a useful monitor of drinking behavior.  相似文献   
98.
The hypothesis that the release of vasopressin-associated neurophysin (hNpI) or oxytocin-associated neurophysin (hNpII) is modified by a course of electroconvulsive therapy (ECT) was tested by the measurement of serum neurophysins before and after the first and last ECTs given to 17 unipolar depressed patients. Neither basal nor ECT-induced neurophysin release changed between the first and last ECTs. Data from the present study were combined with data from a previous published study to provide a sample of 29 unipolar depressed patients. In this extended sample, the release of hNpII after the first ECT was significantly correlated with improvement in symptoms of depression over a course of ECT as measured by the Hamilton Rating Scale for Depression and the Montgomery-Asberg Depression Rating Scale.  相似文献   
99.
100.
Abstract: The development of a teaching package for nurse educators on drug and alcohol problems is described and the contents of its 16 modules outlined.  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