全文获取类型
收费全文 | 158450篇 |
免费 | 11083篇 |
国内免费 | 623篇 |
专业分类
耳鼻咽喉 | 1769篇 |
儿科学 | 3905篇 |
妇产科学 | 2616篇 |
基础医学 | 20938篇 |
口腔科学 | 3389篇 |
临床医学 | 15552篇 |
内科学 | 33625篇 |
皮肤病学 | 3241篇 |
神经病学 | 14605篇 |
特种医学 | 6964篇 |
外国民族医学 | 14篇 |
外科学 | 25221篇 |
综合类 | 1958篇 |
一般理论 | 109篇 |
预防医学 | 11808篇 |
眼科学 | 3306篇 |
药学 | 10139篇 |
中国医学 | 239篇 |
肿瘤学 | 10758篇 |
出版年
2023年 | 885篇 |
2022年 | 1486篇 |
2021年 | 3375篇 |
2020年 | 2079篇 |
2019年 | 3118篇 |
2018年 | 3592篇 |
2017年 | 2799篇 |
2016年 | 3136篇 |
2015年 | 3585篇 |
2014年 | 5091篇 |
2013年 | 6849篇 |
2012年 | 10335篇 |
2011年 | 11003篇 |
2010年 | 6308篇 |
2009年 | 6013篇 |
2008年 | 9745篇 |
2007年 | 10188篇 |
2006年 | 10094篇 |
2005年 | 10142篇 |
2004年 | 9307篇 |
2003年 | 8617篇 |
2002年 | 8267篇 |
2001年 | 2149篇 |
2000年 | 1840篇 |
1999年 | 2126篇 |
1998年 | 1925篇 |
1997年 | 1551篇 |
1996年 | 1333篇 |
1995年 | 1251篇 |
1994年 | 1125篇 |
1993年 | 1015篇 |
1992年 | 1291篇 |
1991年 | 1189篇 |
1990年 | 1033篇 |
1989年 | 973篇 |
1988年 | 911篇 |
1987年 | 884篇 |
1986年 | 885篇 |
1985年 | 866篇 |
1984年 | 924篇 |
1983年 | 795篇 |
1982年 | 960篇 |
1981年 | 861篇 |
1980年 | 728篇 |
1979年 | 654篇 |
1978年 | 646篇 |
1977年 | 533篇 |
1976年 | 514篇 |
1974年 | 511篇 |
1973年 | 449篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Thomas W. McDade Alexander V. Georgiev Christopher W. Kuzawa 《Evolution, Medicine, and Public Health》2016,2016(1):1-16
Immune defenses provide resistance against infectious disease that is critical to survival. But immune defenses are costly, and limited resources allocated to immunity are not available for other physiological or developmental processes. We propose a framework for explaining variation in patterns of investment in two important subsystems of anti-pathogen defense: innate (non-specific) and acquired (specific) immunity. The developmental costs of acquired immunity are high, but the costs of maintenance and activation are relatively low. Innate immunity imposes lower upfront developmental costs, but higher operating costs. Innate defenses are mobilized quickly and are effective against novel pathogens. Acquired responses are less effective against novel exposures, but more effective against secondary exposures due to immunological memory. Based on their distinct profiles of costs and effectiveness, we propose that the balance of investment in innate versus acquired immunity is variable, and that this balance is optimized in response to local ecological conditions early in development. Nutritional abundance, high pathogen exposure and low signals of extrinsic mortality risk during sensitive periods of immune development should all favor relatively higher levels of investment in acquired immunity. Undernutrition, low pathogen exposure, and high mortality risk should favor innate immune defenses. The hypothesis provides a framework for organizing prior empirical research on the impact of developmental environments on innate and acquired immunity, and suggests promising directions for future research in human ecological immunology. 相似文献
42.
Frédéric Janvier Deborah Delaune Thomas Poyot Eric Valade Audrey Mérens Pierre E. Rollin Vincent Foissaud 《Emerging infectious diseases》2016,22(2):292-294
We evaluated RNA stability of Ebola virus in EDTA blood and urine samples collected from infected patients and stored in West Africa’s environmental conditions. In blood, RNA was stable for at least 18 days when initial cycle threshold values were <30, but in urine, RNA degradation occurred more quickly. 相似文献
43.
44.
The specific role of postsynaptic activity for the generation of a functional magnetic resonance imaging (fMRI) response was determined by a simultaneous measurement of generated field excitatory postsynaptic potentials (fEPSPs) and blood oxygen level-dependent (BOLD) response in the rat hippocampal CA1 region during electrical stimulation of the contralateral CA3 region. The stimulation electrode was placed either in the left CA3a/b or CA3c, causing the preferentially basal or apical dendrites of the pyramidal cells in the right CA1 to be activated. Consecutive stimulations with low-intensity stimulation trains (i.e., 16 pulses for 8 seconds) resulted in clear postsynaptic responses of CA1 pyramidal cells, but in no significant BOLD responses. In contrast, consecutive high-intensity stimulation trains resulted in stronger postsynaptic responses that came along with minor (during stimulation of the left CA3a/b) or substantial (during stimulation of the left CA3c) spiking activity of the CA1 pyramidal cells, and resulted in the generation of significant BOLD responses in the left and right hippocampus. Correlating the electrophysiologic parameters of CA1 pyramidal cell activity (fEPSP and spiking activity) with the resultant BOLD response revealed no positive correlation. Consequently, postsynaptic activity of pyramidal cells, the most abundant neurons in the CA1, is not directly linked to the measured BOLD response. 相似文献
45.
46.
47.
48.
49.
50.
Daniel J. Snyder Thomas R. Kroshus Aakash Keswani Evan B. Garden Karl M. Koenig Kevin J. Bozic David S. Jevsevar Jashvant Poeran Calin S. Moucha 《The Journal of arthroplasty》2019,34(4):613-618