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   47029篇
  免费   3373篇
  国内免费   194篇
耳鼻咽喉   375篇
儿科学   1511篇
妇产科学   1209篇
基础医学   6626篇
口腔科学   590篇
临床医学   5056篇
内科学   9816篇
皮肤病学   878篇
神经病学   5559篇
特种医学   1133篇
外科学   4181篇
综合类   382篇
一般理论   58篇
预防医学   5699篇
眼科学   687篇
药学   2987篇
中国医学   87篇
肿瘤学   3762篇
  2024年   59篇
  2023年   651篇
  2022年   1089篇
  2021年   2146篇
  2020年   1298篇
  2019年   1776篇
  2018年   2042篇
  2017年   1364篇
  2016年   1518篇
  2015年   1667篇
  2014年   2032篇
  2013年   2629篇
  2012年   4208篇
  2011年   4164篇
  2010年   2123篇
  2009年   1854篇
  2008年   2957篇
  2007年   2927篇
  2006年   2794篇
  2005年   2589篇
  2004年   2295篇
  2003年   2049篇
  2002年   1752篇
  2001年   201篇
  2000年   153篇
  1999年   217篇
  1998年   352篇
  1997年   264篇
  1996年   214篇
  1995年   175篇
  1994年   124篇
  1993年   117篇
  1992年   81篇
  1991年   76篇
  1990年   65篇
  1989年   73篇
  1988年   59篇
  1987年   43篇
  1986年   46篇
  1985年   40篇
  1984年   49篇
  1983年   44篇
  1982年   34篇
  1981年   41篇
  1980年   31篇
  1979年   18篇
  1978年   16篇
  1977年   20篇
  1975年   9篇
  1973年   8篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Mice homozygous for the lpr mutation have B and T cell defects and develop autoantibodies, suggesting that lpr plays a role in their genesis. The lpr defect has been identified as a mutation in the apoptosis-associated Fas receptor (FasR) gene. To begin to define the role of FasR in B cells, we have surveyed FasR expression on B-lineage cells from early progenitors in the bone marrow through their maturation in the periphery. Contrary to some reports, we found that FasR is expressed on B cells at all stages of their development and is highest on germinal center B cells. FasR is not expressed on lpr/lpr-derived cells. These data are consistent with the idea that lpr/lpr mice have an intrinsic B cell defect that may be manifested in developing as well as peripheral B cells. An unexpected finding is that B-1 (CD5) B cells do not constitutively express FasR: FasR becomes detectable on B-1 B cells only after activation.  相似文献   
22.
Abstract: Breast conservation surgery is an effective and safe treatment for many breast carcinomas. It may be possible to further limit the extent of resection (or expand the indication for breast conservation) by the application of preoperative chemotherapy and radiotherapy. We explored the feasibility of this in a pilot study.
Seventy-three patients (mean age 48, 63% premenopausal) with confirmed breast cancer, less than 2.5 cm, received chemotherapy (Group A) or chemotherapy plus radiotherapy (Group B) prior to limited resection (tumorectomy). Axillary dissection was always performed. Results: In 6/31 (19%) Group A and 17/42 (40%) Group B patients the tumor was not palpable after preoperative treatment, with complete pathological remission in 1 and 3 cases respectively. Histologic grading, mitosis, cellular alteration, and cellularity evaluations indicated a consistently greater therapeutic effect with chemoradiotherapy than with chemotherapy alone.
In conclusion, radiotherapy appears useful in the preoperative treatment of breast cancer and its use in association with various drug combinations should be further explored.  相似文献   
23.
24.
For the past 10 years the alfa-hydroxyacids and the bovine collagen injection have been used for peeling and the correction of multiple skin diseases. Until now, such progressive achievement has occurred in separate parallels just like the indications that have been held distinct. However, the studies carried out in order to clarify the mechanical action of the two substances have shown a common and fundamental denominator: the stimulation of synthesis of the new collagen in the patient's skin. On the basis of these results and the existence of common clinical indications of the use of glycolic acid and collagen, the authors have worked out a protocol involving a combined and contemporary application in progressive steps. They developed the rationales of such protocol and analyzed the results of its application on a number of carefully selected patients for a clinical comparison and on a sample of rats for a histological comparison. They have concluded that the contemporary use of glycolic acid and bovine collagen is a simple and safe method whose synergy action leads to more intense and long-lasting effects than the ones observed in the isolated application of the two substances. The authors have also obtained interesting and significant histological results.  相似文献   
25.
26.
27.
28.
Before meaningful conclusions can be drawn from clinical measures of cerebral blood perfusion, the precision of the measurement must be determined and set in the context of inter- and intrasubject sources of variability. This work establishes the reproducibility of perfusion measurements using the noninvasive MRI technique of continuous arterial spin labeling (CASL). Perfusion was measured in 34 healthy normal subjects. Intersubject variability was assessed, and age and gender contributions were estimated. Intersubject variation was found to be large, with up to 100% perfusion difference for subjects of the same age and gender. Repeated measurements in one subject showed that perfusion remains remarkably stable in the short term when compared with intersubject variation and the large capacity for perfusion change in the brain. A significant decrease in the ratio of gray-matter to white-matter perfusion was found with increasing age (0.79% per year (P < 0.0005)). This appears to be due mainly to a reduction in gray-matter perfusion, which was found to decrease by 0.45% per year (P = 0.04). Regional analysis suggested that the gray-matter age-related changes were predominantly localized in the frontal cortex. Whole-brain perfusion was 13% higher (P = 0.02) in females compared to males.  相似文献   
29.
Sphingolipid metabolites in neural signalling and function   总被引:8,自引:0,他引:8  
Sphingolipid metabolites, such as ceramide, sphingosine, sphingosine-1-phosphate (S1P) and complex sphingolipids (gangliosides), are recognized as molecules capable of regulating a variety of cellular processes. The role of sphingolipid metabolites has been studied mainly in non-neuronal tissues. These studies have underscored their importance as signals transducers, involved in control of proliferation, survival, differentiation and apoptosis. In this review, we will focus on studies performed over the last years in the nervous system, discussing the recent developments and the current perspectives in sphingolipid metabolism and functions.  相似文献   
30.
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