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   2537篇
  免费   308篇
  国内免费   5篇
耳鼻咽喉   41篇
儿科学   79篇
妇产科学   87篇
基础医学   373篇
口腔科学   46篇
临床医学   318篇
内科学   384篇
皮肤病学   55篇
神经病学   151篇
特种医学   61篇
外科学   501篇
综合类   37篇
预防医学   306篇
眼科学   27篇
药学   200篇
中国医学   2篇
肿瘤学   182篇
  2023年   38篇
  2022年   36篇
  2021年   136篇
  2020年   79篇
  2019年   94篇
  2018年   109篇
  2017年   89篇
  2016年   83篇
  2015年   97篇
  2014年   123篇
  2013年   136篇
  2012年   191篇
  2011年   173篇
  2010年   82篇
  2009年   68篇
  2008年   110篇
  2007年   100篇
  2006年   84篇
  2005年   77篇
  2004年   67篇
  2003年   67篇
  2002年   77篇
  2001年   57篇
  2000年   52篇
  1999年   44篇
  1998年   20篇
  1997年   16篇
  1996年   18篇
  1995年   16篇
  1994年   11篇
  1993年   19篇
  1992年   39篇
  1991年   29篇
  1990年   37篇
  1989年   46篇
  1988年   28篇
  1987年   26篇
  1986年   21篇
  1985年   26篇
  1984年   26篇
  1983年   17篇
  1982年   12篇
  1979年   10篇
  1978年   10篇
  1977年   17篇
  1976年   10篇
  1975年   11篇
  1974年   13篇
  1973年   14篇
  1972年   13篇
排序方式: 共有2850条查询结果,搜索用时 46 毫秒
1.
2.
In the upper limb, diffuse cavernous haemangiomas occur infrequently but their treatment is often unsatisfactory and the result of surgical excision disappointing. Four cases of these diffuse haemangiomas are described and their management discussed.  相似文献   
3.
PURPOSE: To evaluate qualitative wall motion assessment vs. quantitative wall thickening for the assessment of subtle changes in myocardial systolic function using cine MRI. METHODS: Cine MR images were obtained in 5 canines with a significant coronary artery stenosis and in 2 controls on a 1.5T scanner. Qualitative results were obtained using a numerical scoring system; quantitative analysis was performed using a semi-automatic segmentation program. The techniques were matched and compared using Spearman correlations. RESULTS: All correlations in the experimental group revealed significant but weak to moderate relationships between the qualitative and quantitative results (e.g., at-risk tissue rho = 0.363, p < 0.0001; remote tissue rho = 0.275, p = 0.0002), with each identifying changes in regional function that ensued following creation of the stenosis. Intra-observer variability was reasonable in both methods when repeat analysis on a subset of the data was performed, with both techniques showing a significant correlation between the repeated measurements (quantitative - rho = 0.52, p < 0.0001; qualitative - rho = 0.54, p < 0.0001). CONCLUSION: Both methods were able to detect very limited wall motion abnormalities present in the canines with significant stenosis and either method gives comparable results.  相似文献   
4.
Abstract. During the 1997 Congress on Gerontology the issue of advocacy was prominently raised in numerous sessions. The delegates affirmed the Declaration of Adelaide, an important statement which called attention to the policy implications of scientific findings. The Declaration set research, practice and education agendas and urged increased resources for gerontological research and programs affecting the well-being of older persons and their families. The wisdom of “linking what we know and can do with what we hope for and desire,” as the theologian Jurgen Moltman has written, requires a systematic effort on the part of gerontologists to influence public policy, standards and professional practice. In short, gerontologists must become advocates. To be effective advocates they must raise awareness of critical issues, form coalitions with those who share the goal of a better world, and exchange information and best practices if the elders of society today - and those who will be the elders of tomorrow - are to benefit from science translated into sound policies and effective practices. Gerontologists must take their scientific findings - and questions - to the forums where policies are discussed and standards and practices developed.  相似文献   
5.
6.
Xylocandin is a complex of novel peptides with potent antifungal activity that is produced by Pseudomonas cepacia ATCC 39277. The complex was isolated from the fermentation broth by extraction with butanol-methanol, 9:1, followed by collection of the precipitate formed upon concentration of the solvent extract. Purification was effected by chromatography on reversed phase and size exclusion gels followed by TLC on silica gel. These techniques afforded eight components: A1, A2, B1, B2, C1, C2, D1 and D2. A mixture of the two closely related components, xylocandins A1 and A2, displayed potent anticandidal and antidermatophytic activities in vitro. The activity was diminished by the presence of serum or vaginal washings. No antibacterial activity was demonstrable.  相似文献   
7.
8.
Patients often cite lack of retention and poor aesthetics as reasons for not wearing their partial dentures. Traditional metal alloy clasps have been shown to exert forces on abutment teeth that exceed those capable of producing tooth movement. In addition, metal display on anterior teeth is often unacceptable. The technopolymer materials are purported to have superior flexibility and exert less force than the metals. This study compared the flexibility and forces produced by technopolymer clasps with those exerted by cobalt-chromium and titanium clasps. The results showed that the technopolymer clasps were up to ten times as flexible as the metal clasps, and they returned to their pretest dimensions after being stretched. In addition, they exerted forces on the abutment teeth that fall within the range of those considered safe for use. This coupled with their pleasing aesthetics makes them suitable for use on periodontally compromised teeth, those with deep undercuts and on anterior teeth.  相似文献   
9.
The etiology of idiopathic scoliosis remains unknown. The condition results in a characteristic deformity of the spine and surrounding tissues. Both Types I and II collagen are important constituents of the affected tissues, and thus defective collagens are reasonable candidates for the primary abnormality in adolescent idiopathic scoliosis (AIS). Direct analyses of the amount and solubility of collagen have revealed differences between normal individuals and those with AIS. However, these changes may be secondary to the mechanical effects of the spinal deformity. Segregation analysis was done of genetic markers linked to the structural genes encoding Types I and II collagen to test these candidate loci in four pedigrees with dominantly inherited AIS. In one pedigree, markers linked to both of the Type I collagen loci (COL1A1 and COL1A2) were found to be inherited independently of the abnormal phenotype. Two pedigrees were discordant at one of the Type I loci. The condition also segregated independently of the locus for Type II collagen (COL2A1) in three pedigrees. This is evidence against idiopathic scoliosis generally being caused by mutations in the Types I and II collagen genes.  相似文献   
10.
M Sykes  V S Abraham 《Transplantation》1992,53(5):1063-1070
We have recently demonstrated that high-dose IL-2, when begun on the day of bone marrow transplantation, has a potent protective effect against graft-vs.-host disease mortality, especially when coadministered with T cell-depleted syngeneic bone marrow cells. Because several groups of investigators have demonstrated that lymphokine-activated killer cells can mediate GVHD protection, we hypothesized that the mechanism of protection by IL-2 administration might involve the in vivo activation of natural killer and/or LAK cells. In order to test this hypothesis, we evaluated the effect of IL-2 administration on the number of NK1+ cells and on NK-mediated cytotoxic activity in recipients of GVHD-producing inocula. Furthermore, we evaluated the effects on IL-2-induced GVHD protection of depleting NK cells and LAK precursor cells in vivo with mAb against NK1.1 or antiserum against asialo GM1. The results demonstrate that: (1) The number of NK1+ cells is not increased in spleens of IL-2-treated compared with control recipients of GVHD-producing inocula; (2) NK activity is not increased in IL-2-treated compared with control recipients of GVHD-producing inocula during or immediately following the period of IL-2 administration; (3) depletion of NK cells and LAK precursors from the donor and host influenced the time course of GVHD-related mortality in a complex fashion; and (4) IL-2-induced GVHD protection is largely independent of the activity of an NK or LAK cell population of donor or host origin. IL-2-induced GVHD protection therefore reflects primarily the activity of non-LAK protective cell populations, or it may be a direct inhibitory effect on responding donor cell populations as they encounter host antigen.  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