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   354篇
  免费   28篇
  国内免费   23篇
儿科学   18篇
妇产科学   6篇
基础医学   39篇
口腔科学   9篇
临床医学   45篇
内科学   96篇
皮肤病学   30篇
神经病学   12篇
特种医学   70篇
外科学   10篇
综合类   17篇
预防医学   4篇
药学   30篇
肿瘤学   19篇
  2023年   2篇
  2021年   4篇
  2019年   6篇
  2018年   6篇
  2017年   3篇
  2016年   2篇
  2015年   11篇
  2014年   6篇
  2013年   12篇
  2012年   6篇
  2011年   4篇
  2010年   11篇
  2009年   17篇
  2008年   12篇
  2007年   21篇
  2006年   11篇
  2005年   9篇
  2004年   6篇
  2003年   10篇
  2002年   7篇
  2001年   6篇
  2000年   1篇
  1999年   7篇
  1998年   21篇
  1997年   16篇
  1996年   28篇
  1995年   11篇
  1994年   20篇
  1993年   9篇
  1992年   4篇
  1991年   6篇
  1990年   10篇
  1989年   7篇
  1988年   15篇
  1987年   10篇
  1986年   8篇
  1985年   11篇
  1984年   5篇
  1983年   5篇
  1982年   6篇
  1981年   8篇
  1980年   5篇
  1979年   1篇
  1978年   3篇
  1977年   4篇
  1976年   7篇
  1975年   5篇
排序方式: 共有405条查询结果,搜索用时 15 毫秒
61.
Powlis  WD; Brikman  I; Seshadri  SB; Bloch  P 《Radiology》1988,169(3):839-841
The quality of low-contrast portal radiographs for radiation therapy can be improved with electronic contrast enhancement. After the image is copied digitally with a laser scanner microdensitometer into 4,096 gray-scale levels (12 bits) and 1,686 X 2,048 pixels, a special software package permits linear, logarithmic, exponential, or sigmoid transformations of the optical density. The precise representation of the portal image can then be interactively adjusted to emphasize the desired anatomy. Clinical examples demonstrate the value of the digital enhancement approach.  相似文献   
62.
Some models of visual cortical development are based on the assumption that the tangential organization of V1 is not determined prior to visual experience. In these models, correlated binocular activity is a key element in the formation of visual cortical columns, and when the degree of interocular correlation is reduced the models predict an increase in column spacing. To examine this prediction we measured the spacing of columns, as defined by cytochrome oxidase (CO) blobs, in the visual cortex of monkeys whose binocular vision was either normal or disrupted by a strabismus. The spatial distribution of blobs was examined in seven normal and five strabismic macaques. Tangential sections through the upper layers of the visual cortex were stained to reveal the two-dimensional (2D) pattern of CO blobs. Each blob was localized and their center-to-center spacing, packing arrangement and density were calculated using 2D nearest-neighbor spatial analyses. The mean center-to-center spacing of blobs (590 microm for normally reared and 598 microm for strabismic macaques) and the mean density of blobs (3.67 blobs/mm2 for normally reared and 3.45 blobs/mm2 for strabismic macaques) were not significantly different. In addition, the 2D packing arrangement of the blobs was not affected by strabismus. While it is clear that neural activity plays a key role in the elaboration and refinement of ocular dominance cortical modules, we conclude that it does not determine the spatial period of the pattern of CO blobs. This suggests that aspects of the neural circuitry underlying the columnar architecture of the visual cortex are established prenatally and its fundamental periodicity is not modifiable by experience.   相似文献   
63.
Pancreas divisum: thin-section CT   总被引:1,自引:0,他引:1  
Twelve patients with known pancreas divisum underwent thin-section computed tomography (CT) to determine the capability of CT to depict this pancreatic anomaly. Focal pancreatic enlargement was present in five patients. Two distinct pancreatic moieties separated by a fat cleft were noted in three patients; a fourth patient had focal atrophy in the distribution of the dorsal pancreas. The two pancreatic moieties were identified at the same craniocaudal level in all four of these patients. The dorsal duct was depicted in all 12 patients, while the short ventral duct was seen in only five of the 12 patients. Failure of the ventral and dorsal pancreatic ducts to fuse was identified in all five patients in whom both ducts were seen. CT may not enable specific diagnosis of pancreas divisum in the majority of patients. If, however, distinct pancreatic moieties or unfused ductal systems are evident, the diagnosis may be confidently suggested.  相似文献   
64.
65.
Dessypris  EN; Redline  S; Harris  JW; Krantz  SB 《Blood》1985,65(4):789-794
The pathogenesis of diphenylhydantoin-induced pure red cell aplasia was investigated in the case of a 32-year-old man who developed pure red cell aplasia while he was under treatment with diphenylhydantoin. The patient's serum IgG purified from serum drawn at the time of diagnosis suppressed normal allogeneic marrow colony-forming (CFU-E) and burst- forming (BFU-E) and autologous blood BFU-E growth in vitro only in the presence of diphenylhydantoin. This IgG-diphenylhydantoin complex had no effect on CFU-GM growth in vitro. Normal IgG or patient's IgG purified from serum drawn after the remission of red cell aplasia had no effect on erythroid colony formation in vitro in the presence of diphenylhydantoin. The IgG-diphenylhydantoin complex exerted no direct cytotoxic effect on normal marrow erythroblasts, CFU-E, and BFU-E, nor did it interfere with the action of erythropoietin on marrow erythroblasts. These studies suggest that diphenylhydantoin-induced red cell aplasia is immunologically mediated through an IgG inhibitor, which requires the presence of the drug to suppress erythroid colony formation in vitro. This inhibitor seems to exert its effect on erythroid progenitors at or beyond the stage of differentiation of CFU- E, but not on erythroblasts.  相似文献   
66.
67.
68.
Abeln M  Pitassi A 《Home healthcare nurse》2012,30(3):161-9; quiz 169-71
The healthcare industry is changing, posing challenges to Medicare-certified home healthcare agencies (HHAs). With healthcare reform and the 2011 prospective payment system changes, including reduction in reimbursement to agencies, it is imperative to assess an organization's wound care program. HHAs must provide quality care at lower costs, using evidence-based medicine that may include nontraditional approaches to providing care.  相似文献   
69.
While numerous researches addressed the connection between physical exercise, changes in brain cortical activity and its relationship to psycho-physiological processes, most of these neuro-scientific studies were set up for healthy individuals. However, the benefits of exercise, such as well being, physical and cognitive health enhancements are also becoming increasingly important for intellectually disabled individuals.This study aimed to localize electroencephalographic activity changes in intellectually disabled individuals following a moderate running exercise for 30 min. An increase in cognitive performance and in mood was hypothesized to correlate with a decrease in fronto-temporal brain areas following exercise.Significant changes in cortical current density in frontal brain areas as well as decreases in perceived physical energy could be shown. Overall motivational states (including self-confidence and social acceptance) as well as positive mood increased significantly. However, no changes could be observed for the cognitive tasks following exercise.With respect to the data provided here there is reason to believe, that a self-selected pace running exercise, enhances self-esteem, coincided with cortical activity changes in fronto-temporal brain areas.  相似文献   
70.
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