全文获取类型
收费全文 | 339245篇 |
免费 | 68634篇 |
国内免费 | 21042篇 |
专业分类
耳鼻咽喉 | 3523篇 |
儿科学 | 6501篇 |
妇产科学 | 3578篇 |
基础医学 | 47744篇 |
口腔科学 | 9336篇 |
临床医学 | 50599篇 |
内科学 | 60883篇 |
皮肤病学 | 9759篇 |
神经病学 | 27576篇 |
特种医学 | 11774篇 |
外国民族医学 | 198篇 |
外科学 | 38550篇 |
综合类 | 46221篇 |
现状与发展 | 75篇 |
一般理论 | 48篇 |
预防医学 | 20680篇 |
眼科学 | 9492篇 |
药学 | 34155篇 |
314篇 | |
中国医学 | 17439篇 |
肿瘤学 | 30476篇 |
出版年
2024年 | 1004篇 |
2023年 | 4578篇 |
2022年 | 11885篇 |
2021年 | 15797篇 |
2020年 | 15862篇 |
2019年 | 19752篇 |
2018年 | 19575篇 |
2017年 | 19824篇 |
2016年 | 19904篇 |
2015年 | 24004篇 |
2014年 | 26711篇 |
2013年 | 24794篇 |
2012年 | 23083篇 |
2011年 | 25840篇 |
2010年 | 22048篇 |
2009年 | 15424篇 |
2008年 | 15566篇 |
2007年 | 14444篇 |
2006年 | 14694篇 |
2005年 | 14667篇 |
2004年 | 9043篇 |
2003年 | 8506篇 |
2002年 | 7325篇 |
2001年 | 6662篇 |
2000年 | 7216篇 |
1999年 | 7484篇 |
1998年 | 4790篇 |
1997年 | 4794篇 |
1996年 | 3706篇 |
1995年 | 3549篇 |
1994年 | 2929篇 |
1993年 | 1974篇 |
1992年 | 2235篇 |
1991年 | 1857篇 |
1990年 | 1576篇 |
1989年 | 1341篇 |
1988年 | 1136篇 |
1987年 | 995篇 |
1986年 | 750篇 |
1985年 | 611篇 |
1984年 | 350篇 |
1983年 | 215篇 |
1982年 | 116篇 |
1981年 | 127篇 |
1980年 | 83篇 |
1979年 | 90篇 |
1977年 | 1篇 |
1972年 | 1篇 |
1965年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Yinlei
Wen Huaguang Zhang Hanguang Su He Ren 《Optimal control applications & methods.》2020,41(4):1233-1250
In this article, a model-free off-policy reinforcement learning algorithm is applied to address the optimal tracking problem based on multiplayer non-zero-sum games for discrete-time linear systems. In contrast to the traditional method and the policy iteration method for solving the optimal tracking problems, the proposed algorithm operates with the system data rather than the knowledge of the system dynamics. For performing the proposed algorithm, an auxiliary augmented system is constructed via assembling the original system and the reference trajectory while a discount factor is introduced into the performance indexes. It is analyzed that the solutions of the proposed algorithm converge to the Nash equilibrium and the result is not influenced by the probing noise. Two simulations are presented to verify the feasibility and effectiveness of the proposed algorithm. 相似文献
62.
63.
64.
65.
66.
67.
68.
Jinju Wang Shuzhen Chen Wenfeng Zhang Yanfang Chen Ji C. Bihl 《CNS Neuroscience & Therapeutics》2020,26(12):1255
AimsWe previously showed that the protective effects of endothelial progenitor cells (EPCs)‐released exosomes (EPC‐EXs) on endothelium in diabetes. However, whether EPC‐EXs are protective in diabetic ischemic stroke is unknown. Here, we investigated the effects of EPC‐EXs on diabetic stroke mice and tested whether miR‐126 enriched EPC‐EXs (EPC‐EXsmiR126) have enhanced efficacy.MethodsThe db/db mice subjected to ischemic stroke were intravenously administrated with EPC‐EXs 2 hours after ischemic stroke. The infarct volume, cerebral microvascular density (MVD), cerebral blood flow (CBF), neurological function, angiogenesis and neurogenesis, and levels of cleaved caspase‐3, miR‐126, and VEGFR2 were measured on day 2 and 14.ResultsWe found that (a) injected EPC‐EXs merged with brain endothelial cells, neurons, astrocytes, and microglia in the peri‐infarct area; (b) EPC‐EXsmiR126 were more effective than EPC‐EXs in decreasing infarct size and increasing CBF and MVD, and in promoting angiogenesis and neurogenesis as well as neurological functional recovery; (c) These effects were accompanied with downregulated cleaved caspase‐3 on day 2 and vascular endothelial growth factor receptor 2 (VEGFR2) upregulation till day 14.ConclusionOur results indicate that enrichment of miR126 enhanced the therapeutic efficacy of EPC‐EXs on diabetic ischemic stroke by attenuating acute injury and promoting neurological function recovery. 相似文献
69.
70.