全文获取类型
收费全文 | 423篇 |
免费 | 40篇 |
国内免费 | 24篇 |
专业分类
儿科学 | 18篇 |
妇产科学 | 6篇 |
基础医学 | 37篇 |
口腔科学 | 9篇 |
临床医学 | 62篇 |
内科学 | 106篇 |
皮肤病学 | 30篇 |
神经病学 | 13篇 |
特种医学 | 71篇 |
外科学 | 49篇 |
综合类 | 23篇 |
预防医学 | 13篇 |
药学 | 30篇 |
肿瘤学 | 20篇 |
出版年
2023年 | 2篇 |
2021年 | 5篇 |
2020年 | 1篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 8篇 |
2016年 | 6篇 |
2015年 | 15篇 |
2014年 | 13篇 |
2013年 | 17篇 |
2012年 | 10篇 |
2011年 | 11篇 |
2010年 | 17篇 |
2009年 | 22篇 |
2008年 | 15篇 |
2007年 | 30篇 |
2006年 | 14篇 |
2005年 | 14篇 |
2004年 | 12篇 |
2003年 | 14篇 |
2002年 | 8篇 |
2001年 | 7篇 |
2000年 | 5篇 |
1999年 | 9篇 |
1998年 | 22篇 |
1997年 | 16篇 |
1996年 | 29篇 |
1995年 | 8篇 |
1994年 | 18篇 |
1993年 | 8篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 11篇 |
1989年 | 7篇 |
1988年 | 14篇 |
1987年 | 11篇 |
1986年 | 10篇 |
1985年 | 11篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1975年 | 3篇 |
排序方式: 共有487条查询结果,搜索用时 0 毫秒
61.
62.
63.
The angiographic appearance of intrarenal leiomyoma 总被引:1,自引:0,他引:1
64.
65.
66.
67.
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
68.
Spacing of cytochrome oxidase blobs in visual cortex of normal and strabismic monkeys 总被引:3,自引:3,他引:0
Murphy KM; Jones DG; Fenstemaker SB; Pegado VD; Kiorpes L; Movshon JA 《Cerebral cortex (New York, N.Y. : 1991)》1998,8(3):237-244
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
69.
Pancreas divisum: thin-section CT 总被引:1,自引:0,他引:1
Zeman RK; McVay LV; Silverman PM; Cattau EL; Benjamin SB; Fleischer DF; Garra BS; Jaffe MH 《Radiology》1988,169(2):395-398
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
70.