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   678篇
  免费   32篇
  国内免费   39篇
耳鼻咽喉   1篇
儿科学   29篇
妇产科学   7篇
基础医学   62篇
口腔科学   18篇
临床医学   79篇
内科学   178篇
皮肤病学   6篇
神经病学   40篇
特种医学   166篇
外科学   49篇
综合类   16篇
预防医学   12篇
眼科学   6篇
药学   55篇
肿瘤学   25篇
  2022年   2篇
  2021年   4篇
  2020年   2篇
  2019年   4篇
  2018年   10篇
  2017年   7篇
  2016年   6篇
  2015年   12篇
  2014年   16篇
  2013年   11篇
  2012年   13篇
  2011年   11篇
  2010年   17篇
  2009年   29篇
  2008年   10篇
  2007年   32篇
  2006年   18篇
  2005年   14篇
  2004年   13篇
  2003年   12篇
  2002年   11篇
  2001年   8篇
  2000年   9篇
  1999年   12篇
  1998年   51篇
  1997年   45篇
  1996年   38篇
  1995年   29篇
  1994年   23篇
  1993年   33篇
  1992年   8篇
  1991年   13篇
  1990年   9篇
  1989年   26篇
  1988年   19篇
  1987年   22篇
  1986年   12篇
  1985年   19篇
  1984年   14篇
  1983年   15篇
  1982年   14篇
  1981年   16篇
  1980年   19篇
  1979年   2篇
  1978年   8篇
  1977年   7篇
  1976年   8篇
  1975年   4篇
  1973年   2篇
  1967年   2篇
排序方式: 共有749条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Normal and diseased isolated lungs: high-resolution CT   总被引:8,自引:0,他引:8  
  相似文献   
5.
6.
Shiota  Y; Wilson  JG; Harjes  K; Zanjani  ED; Tavassoli  M 《Blood》1993,82(5):1436-1444
The adhesion of hematopoietic progenitor cells to bone marrow stromal cells is critical to hematopoiesis and involves multiple effector molecules. Stromal cell molecules that participate in this interaction were sought by analyzing the detergent-soluble membrane proteins of GBI/6 stromal cells that could be adsorbed by intact FDCP-1 progenitor cells. A single-chain protein from GBI/6 cells having an apparent molecular weight of 37 Kd was selectively adsorbed by FDCP-1 cells. This protein, designated p37, could be surface-radiolabeled and thus appeared to be exposed on the cell membrane. An apparently identical 37- Kd protein was expressed by three stromal cell lines, by Swiss 3T3 fibroblastic cells, and by FDCP-1 and FDCP-2 progenitor cells. p37 was selectively adsorbed from membrane lysates by a variety of murine hematopoietic cells, including erythrocytes, but not by human erythrocytes. Binding of p37 to cells was calcium-dependent, and was not affected by inhibitors of the hematopoietic homing receptor or the cell-binding or heparin-binding functions of fibronectin. It is proposed that p37 may be a novel adhesive molecule expressed on the surface of a variety of hematopoietic cells that could participate in both homotypic and heterotypic interactions of stromal and progenitor cells.  相似文献   
7.
BACKGROUND: Because of the shortage of heart donors in the United States, efforts are necessary to maximize the yield of donor screening. The purpose of this study was to quantify the effects of left ventricular (LV) systolic dysfunction on heart donor use. METHODS: Using the California Transplant Donor Network database, the records of all potential organ donors screened between January 1997 and June 1998 were reviewed. After excluding subjects for whom family consent could not be obtained and subjects <13 or >or=60 years old, a study group of 223 potential heart donors was analyzed. The number of hearts not used because of LV dysfunction, coronary artery disease (CAD), valvular disease, and LV hypertrophy were quantified. A logistic regression model was developed to quantify the independent effect of LV dysfunction on donor use rates after adjustment for age, weight, and cause of death. RESULTS: Ninety-nine (44%) of the 223 potential donor hearts were not transplanted. Thirty-six of these hearts were not transplanted because of cardiac causes, primarily LV dysfunction (26 cases) and CAD (8 cases). The multivariable analysis showed that after adjusting for other donor variables, ejection fraction was the most significant predictor of non-use, with an odds ratio of 1.48 per 5-point decrease in ejection fraction. CONCLUSIONS: Left ventricular dysfunction is an important cause of failure to transplant adult donor hearts. Efforts to improve the yield of heart donor screening should focus on prevention or reversal of LV dysfunction.  相似文献   
8.
9.
10.
In a human in-vitro fertilization (IVF) programme, the effect of co- culture of embryos with human fibroblasts was evaluated with respect to pregnancy rate and embryo development. Patients were included in the study after giving informed written consent. The IVF treatments were randomly assigned by stratification of both age (<36 versus > or =36 years) and previous IVF attempts (yes versus no). After fertilization was established, the zygotes were transferred to a 4-well dish with or without fibroblasts and cultured for 2 days. On the third day after ovum pick-up (OPU), cell number and quality [5 (good) to 1 (poor)] of the embryos were scored and a maximum of three embryos was transferred. Supernumerary embryos of good quality were cryopreserved. The design of this study was a group sequential trial with the objective of detecting differences between pregnancy rates following IVF with conventional incubation or incubation in co-culture with fibroblasts. This design included one evaluation at half-way data collection. In the study, 148 patients had an OPU, of whom 77 were allocated to the co-culture group. There was no statistically significant difference in pregnancy rate, cell number and embryo quality between the two groups. The ongoing pregnancy rate per embryo transfer was 27% in co-culture and 30% in the conventional culture group. The implantation rates per transferred embryo were 17 and 18% respectively. Using a multivariate logistic regression model for the probability of ongoing pregnancies, the odds ratio of co-culture, adjusted for age and previous IVF attempts, was not statistically significant. In conclusion, co-culture with human fibroblasts does not contribute to an improvement of embryo quality nor to a higher pregnancy rate after IVF in an unselected group of patients.   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