全文获取类型
收费全文 | 902篇 |
免费 | 72篇 |
国内免费 | 22篇 |
专业分类
耳鼻咽喉 | 2篇 |
儿科学 | 102篇 |
妇产科学 | 9篇 |
基础医学 | 109篇 |
口腔科学 | 16篇 |
临床医学 | 118篇 |
内科学 | 182篇 |
皮肤病学 | 15篇 |
神经病学 | 115篇 |
特种医学 | 128篇 |
外科学 | 56篇 |
综合类 | 10篇 |
预防医学 | 64篇 |
眼科学 | 3篇 |
药学 | 51篇 |
肿瘤学 | 16篇 |
出版年
2021年 | 6篇 |
2019年 | 9篇 |
2018年 | 7篇 |
2017年 | 11篇 |
2016年 | 6篇 |
2015年 | 12篇 |
2014年 | 14篇 |
2013年 | 30篇 |
2012年 | 16篇 |
2011年 | 33篇 |
2010年 | 36篇 |
2009年 | 22篇 |
2008年 | 27篇 |
2007年 | 35篇 |
2006年 | 19篇 |
2005年 | 33篇 |
2004年 | 21篇 |
2003年 | 18篇 |
2002年 | 13篇 |
2001年 | 28篇 |
2000年 | 27篇 |
1999年 | 27篇 |
1998年 | 46篇 |
1997年 | 51篇 |
1996年 | 42篇 |
1995年 | 21篇 |
1994年 | 26篇 |
1993年 | 21篇 |
1992年 | 35篇 |
1991年 | 28篇 |
1990年 | 29篇 |
1989年 | 16篇 |
1988年 | 38篇 |
1987年 | 19篇 |
1986年 | 22篇 |
1985年 | 15篇 |
1984年 | 15篇 |
1983年 | 16篇 |
1982年 | 17篇 |
1981年 | 13篇 |
1980年 | 13篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1969年 | 3篇 |
1967年 | 5篇 |
排序方式: 共有996条查询结果,搜索用时 15 毫秒
1.
M A Warner K H Neill J V Nadler B J Crain 《Journal of cerebral blood flow and metabolism》1991,11(4):600-610
This study compared the ability of three N-methyl-D-aspartate (NMDA) receptor antagonists to prevent neuronal degeneration in an animal model of global cerebral ischemia. The model employed is characterized by damage to the striatum, hippocampus, and neocortex. Antagonists were administered to gerbils either before or after a 5-min bilateral carotid occlusion. The intraischemic rectal temperature was either maintained at 36-37 degrees C or allowed to fall passively to 28-32 degrees C. Antagonists and doses tested were 1 and 10 mg/kg of MK-801 (pre- or postischemia), 30 mg/kg of CGS 19755 preischemia, four 25 mg/kg doses of CGS 19755 administered between 0.5 and 6.5 h postischemia, and 40 mg/kg of MDL 27,266 (pre- or postischemia). All three NMDA receptor antagonists exhibited some degree of neuroprotective activity when the carotid occlusion was performed under normothermic conditions. Most of the treatments with antagonist markedly reduced striatal damage. CA1 hippocampal and neocortical pyramidal cells were spared by only three of the treatments, however, and the extent of neuroprotection varied widely from case to case. Toxic doses of antagonist were required to protect CA1 pyramidal cells from ischemic damage. Ischemic damage to hippocampal areas CA2-CA3a and CA4 appeared to be resistant to all of these treatments. Most CA1 pyramidal cells that were protected from degeneration by an NMDA receptor antagonist were histologically abnormal. The neuroprotective effects of MK-801 and intraischemic hypothermia appeared to be additive. MK-801 (10 mg/kg) consistently reduced the postischemic brain temperature, but only the magnitude of hypothermia produced soon after reperfusion correlated with its neuroprotective action. These results suggest that NMDA receptor antagonists are relatively poor neuroprotective agents against a moderately severe ischemic insult. 相似文献
2.
G. Wu S. F. Fan Z.-H. Lu R. W. Ledeen S. M. Crain 《Journal of neuroscience research》1995,42(4):493-503
Prolongation of the action potential duration of dorsal root ganglion (DRG) neurons by low (nM) concentrations of opioids occurs through activation of excitatory opioid receptors that are positively coupled via Gs regulatory protein to adenylate cyclase. Previous results suggested GM1 ganglioside to have an essential role in regulating this excitatory response, but not the inhibitory (APD-shortening) response to higher (μM) opioid concentrations. Furthermore, it was proposed that synthesis of GM1 is upregulated by prolonged activation of excitatory opioid receptor functions. To explore this possibility we have utilized cultures of hybrid F11 cells to carry out closely correlated electrophysiological and biochemical analyses of the effects of chronic opioid treatment on a homogeneous population of clonal cells which express many functions characteristic of DRG neurons. We show that chronic opioid exposure of F11 cells does, in fact, result in elevated levels of GM1 as well as cyclic adenosine monophosphate (AMP), concomitant with the onset of opioid excitatory supersensitivity as manifested by naloxone-evoked decreases in voltage-dependent membrane K+ currents. Such elevation of GM1 would be expected to enhance the efficacy of excitatory opioid receptor activation of the Gs/adenylate cyclase/cyclic AMP system, thereby providing a positive feedback mechanism that may account for the remarkable supersensitivity of chronic opioid-treated neurons to the excitatory effects of opioid agonists as well as antagonists. These in vitro findings may provide novel insights into the mechanisms underlying naloxone-precipitated withdrawal syndromes and opioid-induced hyperalgesia after chronic opiatf addiction in vivo. © 1995 Wiley-Liss, Inc. 相似文献
3.
Factors influencing women to undergo screening mammography 总被引:2,自引:0,他引:2
4.
Braffman BH; Coleman BG; Ramchandani P; Arger PH; Nodine CF; Dinsmore BJ; Louie A; Betsch SE 《Radiology》1994,190(3):797
5.
6.
7.
Rupture of the distal biceps tendon: evaluation with MR imaging 总被引:2,自引:0,他引:2
8.
Effects of cardiopulmonary bypass on pulmonary leukostasis and complement activation 总被引:2,自引:0,他引:2
R J Howard C Crain D A Franzini C I Hood T E Hugli 《Archives of surgery (Chicago, Ill. : 1960)》1988,123(12):1496-1501
We measured white blood cell counts and complement component (C3a, C4a, and C5a) and prostacyclin levels, and studied lung biopsy specimens, in 16 patients undergoing cardiopulmonary bypass and compared them with four patients undergoing other pulmonary procedures. Bypass caused no significant elevation in peripheral venous white blood cell counts. Higher counts were present in the right atrium compared with the left atrium. Patients who underwent bypass had elevated complement component and prostacyclin concentrations before operation and these levels increased further during operation. Trapping of polymorphonuclear leukocytes occurred in pulmonary alveolar capillaries and venules after bypass. We conclude that bypass activates complement components primarily of the alternative pathway and leads to increased blood prostacyclin levels. These changes are accompanied by polymorphonuclear leukocyte accumulation in the lungs and may be important in initiation of the adult respiratory distress syndrome in these patients. 相似文献
9.
10.
Holliday junctions in FLP recombination: resolution by step-arrest mutants of FLP protein. 总被引:16,自引:1,他引:15 下载免费PDF全文
M Jayaram K L Crain R L Parsons R M Harshey 《Proceedings of the National Academy of Sciences of the United States of America》1988,85(21):7902-7906
The FLP "recombinase" of the 2-micron circle yeast plasmid can resolve synthetic FLP site-Holliday junctions. Mutants of the FLP protein that are blocked in recombination but are normal in substrate cleavage can also mediate resolution. The products of resolution by these mutants are almost exclusively nicked molecules with a protein-bound 3' end. There is no significant asymmetry in strand cleavage (top versus bottom) by the mutants in linear or in circular FLP substrates; nor is there a bias in resolution (toward parentals or toward recombinants) of Holliday junctions (corresponding to top- or to bottom-strand exchange) by wild-type FLP. During normal FLP recombination, a small amount of the expected Holliday intermediate can be detected. 相似文献