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   5656篇
  免费   448篇
  国内免费   11篇
耳鼻咽喉   58篇
儿科学   250篇
妇产科学   170篇
基础医学   824篇
口腔科学   136篇
临床医学   585篇
内科学   1128篇
皮肤病学   114篇
神经病学   766篇
特种医学   480篇
外国民族医学   1篇
外科学   751篇
综合类   99篇
预防医学   311篇
眼科学   38篇
药学   185篇
中国医学   6篇
肿瘤学   213篇
  2021年   75篇
  2020年   40篇
  2019年   48篇
  2018年   72篇
  2017年   50篇
  2016年   61篇
  2015年   97篇
  2014年   137篇
  2013年   164篇
  2012年   225篇
  2011年   227篇
  2010年   142篇
  2009年   126篇
  2008年   252篇
  2007年   242篇
  2006年   206篇
  2005年   218篇
  2004年   211篇
  2003年   229篇
  2002年   199篇
  2001年   177篇
  2000年   191篇
  1999年   149篇
  1998年   128篇
  1997年   109篇
  1996年   103篇
  1995年   69篇
  1994年   66篇
  1993年   71篇
  1992年   103篇
  1991年   104篇
  1990年   104篇
  1989年   84篇
  1988年   120篇
  1987年   122篇
  1986年   117篇
  1985年   87篇
  1984年   84篇
  1983年   73篇
  1982年   65篇
  1981年   49篇
  1980年   46篇
  1979年   60篇
  1978年   64篇
  1977年   61篇
  1976年   55篇
  1974年   42篇
  1973年   47篇
  1972年   50篇
  1969年   43篇
排序方式: 共有6115条查询结果,搜索用时 0 毫秒
21.
A series of pyrimido[1,2-a]indoles were synthesized and studied for their hypoglycemic activity following oral administration at a standard dose of 100 mg/kg to fed rats. The effect of 10-alkoxyalkyl, 10-alkyl, 10-aryl, and 3,3-dialkyl substitution on the activity of 10-hydroxypyrimido[1,2-a]indoles was investigated. Relative potencies of a number of the most active compounds were defined by three-point dose-response studies. The most potent compounds were those with either 3,3-dimethyl substituents, compounds 21, 22, and 38, or 3,3-spirocyclohexane substituents, compounds 39 and 49. 10-Aminopyrimido[1,2-a]indoles were in general less active than the 10-hydroxy analogues, and potency was further decreased by derivatizing the 10-amino group. The most potent 10-amino derivatives were 57 and 58.  相似文献   
22.
Forty conventional radiographs with examples of mild interstitial infiltrates and subtle pneumothoraces and 40 normal studies of the chest were selected and digitized, with pixel sizes of 1.0, 0.5, 0.2, and 0.1 mm. Observer performance tests were carried out using receiver operating characteristic analysis. Conventional radiographs and digitized images were compared. The results indicate that, in such cases, diagnostic accuracy increases significantly as the pixel size is reduced, at least to the 0.1-mm level. We conclude that, for digital systems using screen-film or similar image receptors, use of a pixel size substantially larger than 0.1 mm may result in some loss of diagnostic accuracy.  相似文献   
23.
24.
CD44 is the principal cell surface receptor for hyaluronate. Variant forms of the receptor, produced by alternative splicing, have been found to be associated with tumor progression in a variety of cancers. Based on investigations at the RNA level, it has recently been proposed that expression of CD44 variant V2 was present in urothelial cancer but not in normal urothelium. Since a distinctive marker for urothelial cancer would be extremely useful, frozen sections of normal urothelium and urothelial cancer were examined for expression of standard CD44 and CD44V2. Frozen sections of specimens of 35 patients with transitional cell carcinoma of the bladder, 16 specimens of normal bladder and 5 ureters were examined. Immunohistochemical staining was performed using a polyclonal antibody to CD44V2 (PAB CD44V2), a monoclonal antibody to CD44V2 (MAB CD44V2) and a monoclonal antibody to CD44S (MAB CD44S). CD44V2 and CD44S were also measured in lysates of urine sediments from 21 patients by enzyme-linked immunoabsorbent assay (ELISA). All investigated transitional cell carcinomas expressed CD44V2. There was no differentiation between invasive and noninvasive carcinoma. CD44V2 was also expressed in normal urothelium. Standard CD44 was expressed by the transitional cell carcinoma, normal urothelium, musculature and interstitial tissue. The amount of CD44V2 and CD44S in lysates of urine sediments is not correlated to diagnosis. In contrast to investigations at the RNA level, CD44V2 on the protein level seems not to be a distinctive marker for urothelial cancer. Therefore, CD44V2 will not be a useful diagnostic marker for detection of transitional cell carcinoma.  相似文献   
25.
Twenty-nine patients with diffuse liver disease were examined by ultrasound, CT and MRI. MRI was performed using T1- and T2-weighted spin-echo sequences as well as fast gradient-echo-sequences. The paramagnetic contrast agent Gd-DTPA was applied intravenously (0.1 mmol/kg). in patients with hepatitis, MRI could be used in guiding liver biopsies as inflammatory changes were clearly delineated. CT and ultrasound were superior to MRI in the detection of focal or diffuse fatty degeneration. On the other hand MRI was more helpful in differentiating fatty changes and neoplasm. In liver cirrhosis, fibrotic changes were most clearly demonstrated by MRI. In patients suffering from hemochromatosis MRI offers advantages over CT and ultrasound in the diagnosis and follow up due to the paramagnetic properties of iron, resulting in a reduction in signal intensity. In patients with Wilson's disease a characteristic pattern of parenchymal changes was seen. Administration of Gd- DTPA contributes additional information about perfusion conditions in the liver parenchyma, however this information was not of diagnostic relevance in the cases we studied. Correspondence to: T.J. Vogl  相似文献   
26.
27.
28.
29.
Fulminant subacute sclerosing panencephalitis in association with pregnancy   总被引:1,自引:0,他引:1  
Subacute sclerosing panencephalitis developed during pregnancy in a 27-year-old woman and immediately after delivery in an 18-year-old woman. In both, disease took an acute and fulminant course culminating in a vegetative state within several weeks. It is suggested that the relative older age of disease presentation and the unusually rapid neurologic deterioration were partially due to immunologic and hormonal alterations of pregnancy.  相似文献   
30.
The Situational Competency Test (SCT) is an audiotaped, verbal role-play measure of coping responses to eight drinking and eight non-drinking situations. The present investigation evaluated the comparability of response scores to audiotaped versus written administrations of the SCT in two samples of alcohol clients. The written administration of the SCT yielded significantly shorter durations of response in both clinical samples, but there were no other significant differences between the administration methods on the other scoring dimensions. Correlations of the audiotaped and written summary scores revealed no consistently significant or meaningful associations. Given the differences in duration, the generally poor correlations between summary scores, and the loss of the latency measure in the written format, we recommend retention of the audiotaped administration for use in research.  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