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   17129篇
  免费   1565篇
  国内免费   18篇
耳鼻咽喉   152篇
儿科学   630篇
妇产科学   578篇
基础医学   2320篇
口腔科学   363篇
临床医学   1825篇
内科学   2927篇
皮肤病学   218篇
神经病学   1810篇
特种医学   877篇
外科学   2114篇
综合类   334篇
一般理论   21篇
预防医学   1890篇
眼科学   333篇
药学   1369篇
中国医学   19篇
肿瘤学   932篇
  2021年   235篇
  2020年   187篇
  2019年   220篇
  2018年   279篇
  2017年   238篇
  2016年   235篇
  2015年   280篇
  2014年   375篇
  2013年   532篇
  2012年   767篇
  2011年   787篇
  2010年   477篇
  2009年   384篇
  2008年   715篇
  2007年   728篇
  2006年   694篇
  2005年   660篇
  2004年   593篇
  2003年   628篇
  2002年   567篇
  2001年   546篇
  2000年   546篇
  1999年   495篇
  1998年   207篇
  1997年   181篇
  1996年   157篇
  1995年   151篇
  1994年   136篇
  1992年   390篇
  1991年   411篇
  1990年   409篇
  1989年   363篇
  1988年   388篇
  1987年   396篇
  1986年   321篇
  1985年   346篇
  1984年   264篇
  1983年   223篇
  1982年   142篇
  1979年   252篇
  1978年   194篇
  1977年   142篇
  1976年   167篇
  1974年   178篇
  1973年   170篇
  1972年   151篇
  1971年   139篇
  1970年   135篇
  1969年   169篇
  1968年   146篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
The aim of this study was to explore undergraduate and postgraduate dental students' understanding of a good learning experience by using 'reflection on learning' as described by Schon. Four groups of Year 4 BDS students and one group of postgraduate students in dental public health took part in a series of focus group discussions. The responses were grouped into four broad themes (a) active, practical and positive learning; (b) interactive/together learning; (c) personal learning; (d) theory into practice. Six educational models of good learning proposed by the students are described.  相似文献   
62.
E E Reynoso  A Keating  M A Baker 《Cancer》1987,59(11):1963-1965
A 22-year-old woman presented with acute lymphoblastic leukemia (ALL) during pregnancy. She had been successfully treated for ALL at the age of 3 years and had received maintenance treatment for 11 years. Complete remission of 3 years or more is an important factor for long-term survival and potential cure. Relapses may occur in the first 5 years after maintenance is discontinued. Later relapses are distinctly unusual. We have found six more cases of ALL occurring long after the initial remission in the English literature. It is unclear whether late relapse represents true relapse or a second leukemia. Life-long follow-up of children with ALL may be necessary.  相似文献   
63.
Glycinebetaine has previously been shown to be effective at reducing leakage from liposomes which are frozen then thawed. This study involved the preparation of a series of N-modified betaines and the comparison of their cryoprotective activities with those of glycine, sarcosine, N,N-dimethylglycine and glycinebetaine. All the compounds investigated, with the exception of (dimethyloctylammonio)acetate, reduced the degree of leakage, after freezing and thawing, with additive concentrations up to 0.6 M. Reducing the degree of N-terminal methylation of glycinebetaine appeared to increase the leakage from liposomes at additive concentrations between 0.2 and 0.6 M. (Dimethylethylammonio)acetate, (dimethylisopropylammonio)acetate and (N,N,N',N'-tetramethylethylenediammonio)-N,N'-diacetate appeared to be no more effective than glycinebetaine, whereas improved protection was afforded by (triethylammonio)acetate and (diethylmethylammonio)acetate at most concentrations. This study demonstrates that the cryoprotective activity of glycinebetaine may be improved with modifications to the N-terminal.  相似文献   
64.
This paper uses survival analysis to examine three large-scale, multi-site, randomized, controlled programs that attempted to prevent or delay second births to teenagers. Statistically significant differences in the hypothesized direction were found between the intervention and the control groups in the Elmira and Memphis Home Visitation sites. No statistically significant differences in the hypothesized direction were found in the Teen Parent Welfare Demonstration overall or in any of its three sites or in all New Chance sites combined. Delaying second pregnancies among teenagers requires intensive efforts. Survival analysis is a more accurate and useful way of presenting program results than simple analysis of the proportion of women with a second birth.  相似文献   
65.
Active surveillance for invasive meningococcal disease was conducted during 1986 and 1987 in six areas of the United States with a total population of approximately 34 million persons. The incidence of meningococcal disease was 1.3:10(5). The highest incidence of disease among the surveillance areas was in Los Angeles County (1.65:10(5). Neisseria meningitidis serogroups B and C caused about equal amounts of disease, which reflects a recent increase in the incidence of group C disease. Group C caused more than half of the cases of meningococcal disease in Los Angeles and Tennessee but less than one-third of the cases in Missouri and Oklahoma. Multilocus enzyme electrophoresis demonstrated that a group of closely related isolates of N. meningitidis was prevalent in Los Angeles during the surveillance period and was associated with an increased incidence of meningococcal disease there.  相似文献   
66.
Summary: We have been involved in developing a health-related quality-of-life model for use as an outcome measure in epilepsy. As part of the further development of this model, we have developed a measure of life fulfilment. This scale is based on methods previously described by Krupinski in 1980. The value of Krupinski's approach is the opportunity for patients to weight the numerous aspects of their quality of life and assess the discrepancy between their actual and desired circumstances. The life fulfilment scale has been shown to be reliable (α= 0.7) and valid. The scale is currently being applied to several clinical studies in epilepsy. We believe that the scale provides a valuable contribution to our health-related quality-of-life model.  相似文献   
67.
Morphological comparison of sperm in raw ejaculates and swim-ups showed that the swim-up process does not simply increase the proportion of 'normal' sperm. Rather, sperm of specific morphologies have characteristic grades of upward motility.  相似文献   
68.
69.
70.
A 36-year-old male with a history of immature teratoma and embryonal carcinoma of the testis was admitted to the hospital for abdominal pain and fever. A CT scan revealed a large right abdominal mass. The patient's serum alpha-fetoprotein (AFP) was 46.8 ng/ml (reference < 25 ng/ml). Fine-needle aspiration (FNA) of the mass revealed malignant glandular cells. Chemotherapy was instituted, followed by resection of the large abdominal mass. The tumor was grossly encapsulated, consisting of large areas of necrotic, hemorrhagic tissue surrounded by smaller, multiloculated cysts. Microscopically, the tumor had a villoglandular pattern and variably stratified tall columnar cells. A prominent feature of the columnar cells was supranuclear and subnuclear vacuolization. Intracytoplasmic PAS-positive, diastase-resistant hyaline globules were occasionally present. AFP by immunoperoxidase was prominent within the tumor. This recurrence of the previously diagnosed testicular teratoma with embryonal carcinoma represents a yolk sac tumor with components strongly resembling endometrioid carcinoma, a variant only recently described in eight cases of ovarian origin (Clement et al.: Am J Surg Pathol 1987; 11(10):767-778). We believe this is the first reported case of an endometrioid-like variant of testicular yolk sac tumor and also the first report of the FNA cytology findings in this variant.  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