全文获取类型
收费全文 | 964篇 |
免费 | 75篇 |
国内免费 | 17篇 |
专业分类
儿科学 | 42篇 |
妇产科学 | 38篇 |
基础医学 | 148篇 |
口腔科学 | 15篇 |
临床医学 | 83篇 |
内科学 | 236篇 |
皮肤病学 | 22篇 |
神经病学 | 42篇 |
特种医学 | 135篇 |
外科学 | 77篇 |
综合类 | 46篇 |
预防医学 | 36篇 |
眼科学 | 15篇 |
药学 | 33篇 |
中国医学 | 3篇 |
肿瘤学 | 85篇 |
出版年
2021年 | 10篇 |
2019年 | 5篇 |
2018年 | 10篇 |
2017年 | 6篇 |
2016年 | 9篇 |
2015年 | 8篇 |
2014年 | 14篇 |
2013年 | 23篇 |
2012年 | 19篇 |
2011年 | 33篇 |
2010年 | 23篇 |
2009年 | 30篇 |
2008年 | 20篇 |
2007年 | 36篇 |
2006年 | 34篇 |
2005年 | 37篇 |
2004年 | 26篇 |
2003年 | 28篇 |
2002年 | 23篇 |
2001年 | 22篇 |
2000年 | 22篇 |
1999年 | 19篇 |
1998年 | 37篇 |
1997年 | 47篇 |
1996年 | 56篇 |
1995年 | 30篇 |
1994年 | 27篇 |
1993年 | 31篇 |
1992年 | 24篇 |
1991年 | 17篇 |
1990年 | 20篇 |
1989年 | 29篇 |
1988年 | 25篇 |
1987年 | 25篇 |
1986年 | 26篇 |
1985年 | 16篇 |
1984年 | 13篇 |
1983年 | 17篇 |
1982年 | 17篇 |
1981年 | 12篇 |
1980年 | 13篇 |
1979年 | 14篇 |
1978年 | 16篇 |
1977年 | 12篇 |
1976年 | 13篇 |
1975年 | 9篇 |
1974年 | 8篇 |
1973年 | 7篇 |
1972年 | 5篇 |
1968年 | 6篇 |
排序方式: 共有1056条查询结果,搜索用时 14 毫秒
1.
2.
Abstract: It has been hypothesized that pineal structure and function might differ between temperate zone and tropical species of mammals because of lower amplitudes of seasonal change in photoperiod and, in some areas, less seasonal climatic variation. Anoura geoffroyi produce a single offspring in November or December of each year on the Caribbean island of Trinidad, at 10°N latitude in the deep tropics. Previous work has shown that this population lacks reproductive responses to photoperiod, and must be enforcing seasonal breeding using a non-photoperiodic cue. Anoura geoffroyi have a minute, thin, and rod-like pineal gland. Throughout much of its length, the pineal courses irregularly within the ventrolateral wall of the great cerebral vein. This intimate relationship may have functional implications. Despite having a very small pineal gland, this species produced a nocturnal rise in serum melatonin. Serum melatonin levels in most individuals were below or near undetectable levels during the light period and rose to a peak averaging 100 pg/ml in the last third of the dark period. Our results indicate that, although the pineal gland of A. geoffroyi is extremely small, serum melatonin levels are comparable to those of other mammals. 相似文献
3.
4.
5.
6.
7.
Low-artifact intravascular devices: MR imaging evaluation 总被引:2,自引:0,他引:2
Teitelbaum GP; Ortega HV; Vinitski S; Stern H; Tsuruda JS; Mitchell DG; Rifkin MD; Bradley WG Jr 《Radiology》1988,168(3):713-719
Flow-phantom magnetic resonance (MR) imaging, with use of both spin-echo (SE) and gradient-echo (GRE) techniques at 1.5 T, was performed on the percutaneous Greenfield (beta-III titanium alloy [TMA wire]), Amplatz (MP32-N alloy), and Simon nitinol filters and TMA wire facsimiles of the bird's nest, Gunther, new retrievable, and Amplatz vena caval filters. SE imaging allowed detection of thrombi as small as 5 X 5 mm trapped within the percutaneous Greenfield, Simon nitinol, and TMA-wire facsimile filters; with the MP32-N Amplatz filter, a larger volume of thrombus (10 X 20-mm clots) was necessary for clot detection. GRE imaging allowed detection of intraluminal tilting of the percutaneous Greenfield and facsimile Amplatz (TMA-wire) filters. GRE imaging was useful for demonstrating postfilter turbulence due to clots, which was greatest for the Amplatz filter. Imaging of facsimile vascular devices made of tantalum or TMA wire did not cause the severe "black-hole" MR artifacts typical of the stainless-steel devices. SE and GRE imaging were very useful for determining caval patency in two patients with previously placed Mobin-Uddin filters. Noninvasive MR evaluation of blood vessels in the presence of a variety of low-artifact intravascular devices appears feasible. 相似文献
8.
9.
Variability of skin temperature in the waking monkey 总被引:3,自引:0,他引:3
10.
CD40 ligand-CD40 interactions are important in the development of experimental autoimmune encephalomyelitis (EAE), but it is unclear whether this interaction is critical for de novo recruitment of T cells, entry of T cells into the central nervous system (CNS), or effector function of T cells in vivo. In this report we define the role of CD40 in a model of progressive EAE that does not depend on epitope spread or recruitment of new myelin-specific T cells into the CNS. Results show that CD40 is not required for trans-migration of activated T cells through the endothelial blood-brain barrier, and in its absence T cells will both enter the CNS and induce disease. However, interaction with CD40 is critical for optimal activation and encephalitogenicity of cloned Th1 cells. In its presence, Th1 cells enter the CNS earlier and induce more severe disease. Inclusion of IL-12 during activation of Th1 cells in the absence of CD40 can override the otherwise suboptimal level of encephalitogenicity observed. The implication of these findings for therapeutic use of agents designed to block this pathway is discussed. 相似文献