首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   808488篇
  免费   89172篇
  国内免费   975篇
  2018年   7819篇
  2017年   7305篇
  2016年   10556篇
  2015年   14586篇
  2014年   17048篇
  2013年   24030篇
  2012年   26961篇
  2011年   27302篇
  2010年   18527篇
  2009年   16843篇
  2008年   24035篇
  2007年   24584篇
  2006年   23156篇
  2005年   22312篇
  2004年   22171篇
  2003年   21285篇
  2002年   20478篇
  2001年   38371篇
  2000年   38592篇
  1999年   30518篇
  1998年   10439篇
  1997年   10857篇
  1996年   10214篇
  1995年   9851篇
  1994年   9592篇
  1993年   9352篇
  1992年   24790篇
  1991年   24043篇
  1990年   23425篇
  1989年   22805篇
  1988年   21156篇
  1987年   19745篇
  1986年   18310篇
  1985年   18134篇
  1984年   15045篇
  1983年   12544篇
  1982年   9518篇
  1981年   8487篇
  1980年   7941篇
  1979年   13479篇
  1978年   10486篇
  1977年   9426篇
  1976年   8526篇
  1975年   9494篇
  1974年   10120篇
  1973年   10020篇
  1972年   8950篇
  1971年   8161篇
  1970年   6967篇
  1969年   6732篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
24.
There is considerable need for accurate suicide risk assessment for clinical, screening, and research purposes. This study applied the tripartite affect-behavior-cognition theory, the suicidal barometer model, classical test theory, and item response theory (IRT), to develop a brief self-report measure of suicide risk that is theoretically-grounded, reliable and valid. An initial survey (n = 359) employed an iterative process to an item pool, resulting in the six-item Suicidal Affect-Behavior-Cognition Scale (SABCS). Three additional studies tested the SABCS and a highly endorsed comparison measure. Studies included two online surveys (Ns = 1007, and 713), and one prospective clinical survey (n = 72; Time 2, n = 54). Factor analyses demonstrated SABCS construct validity through unidimensionality. Internal reliability was high (α = .86-.93, split-half = .90-.94)). The scale was predictive of future suicidal behaviors and suicidality (r = .68, .73, respectively), showed convergent validity, and the SABCS-4 demonstrated clinically relevant sensitivity to change. IRT analyses revealed the SABCS captured more information than the comparison measure, and better defined participants at low, moderate, and high risk. The SABCS is the first suicide risk measure to demonstrate no differential item functioning by sex, age, or ethnicity. In all comparisons, the SABCS showed incremental improvements over a highly endorsed scale through stronger predictive ability, reliability, and other properties. The SABCS is in the public domain, with this publication, and is suitable for clinical evaluations, public screening, and research.  相似文献   
25.
26.
Botrytis allii andCollectotrichum dematium are onion pathogens which can infect in the field and cause decay in storage. Some phenolics can hinder development of these fungi, but the effect of cytokinins is not clear. Cytokinins (kinetin or 6-benzyladenine) or phenolics (caffeic or chlorogenic acids) were added to agar at concentrations of 0 to 10–3 M. Cultures were continuously irradiated with fluorescent light or maintained in the dark for 6 days. On unamended media, final mycelial elongation was 45 or 17.8 mm and sporulation was 28 or 10.6 × 104 spores/ml forBotrytis andColletotrichum, respectively. ForBotrytis, mycelial elongation was slightly (5%) but significantly increased and sporulation increased by 21% by incubation on phenolics as compared to cytokinins. Mycelial extension ofColletotrichum was not affected by amendment. Sporulation ofColletotrichum on kinetin was 16 to 28% greater than on the other amendments. As amendments concentration increased elongation of mycelia of both fungi decreased. Sporulation ofBotrytis increased by 60% as amendment concentration increased from 0 to 10–5 M and then decreased 25% at 10–3 M. As amendment concentration increased from 0 to 10–3 M, sporulation ofColletotrichum increased by 45%. Incubation in light increased mycelial extension 3 to 17% forBotrytis andColletotrichum respectively, and sporulation was increased approximately 78% for both fungi. These compounds do not appear to inhibit development of theseBotrytis orColletotrichum species in culture.  相似文献   
27.
28.
29.
Abstract: The glial fibrillary acidic protein (GFAP) content was investigated using immunoblotting techniques in the septum and hippocampus of the rat after bilateral lateral fimbria transection. Seven days after surgery GFAP content increased significantly both in the septum (140% of control) and hippocampus (120% in dorsal, the less denervated, and 145% in the most denervated ventral part), indicating the occurrence of reactive gliosis. The GM1 treatment caused statistically significant attenuation of GFAP increment in all hippocampal parts. In contrast, GM1 treatment has no influence on the increase of GFAP content in the septum. Results suggest a differential effect of GM1 on the two gliotic reactions formed as a consequence of the lesion at the level of the source of innervation (septum) and the target (hippocampus).  相似文献   
30.
Foreword     
  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号