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   5963篇
  免费   97篇
  国内免费   328篇
系统科学   76篇
丛书文集   171篇
教育与普及   49篇
理论与方法论   47篇
现状及发展   127篇
研究方法   1篇
综合类   5907篇
自然研究   10篇
  2024年   22篇
  2023年   16篇
  2022年   31篇
  2021年   36篇
  2020年   48篇
  2019年   55篇
  2018年   39篇
  2017年   64篇
  2016年   55篇
  2015年   130篇
  2014年   597篇
  2013年   422篇
  2012年   741篇
  2011年   607篇
  2010年   647篇
  2009年   450篇
  2008年   494篇
  2007年   127篇
  2006年   123篇
  2005年   139篇
  2004年   102篇
  2003年   129篇
  2002年   99篇
  2001年   68篇
  2000年   75篇
  1999年   51篇
  1998年   38篇
  1997年   50篇
  1996年   373篇
  1995年   258篇
  1994年   180篇
  1993年   24篇
  1992年   15篇
  1991年   12篇
  1990年   27篇
  1989年   20篇
  1988年   6篇
  1987年   8篇
  1986年   3篇
  1985年   3篇
  1984年   1篇
  1983年   2篇
  1982年   1篇
排序方式: 共有6388条查询结果,搜索用时 31 毫秒
171.
钟声的奥秘--《枫桥夜泊》新探   总被引:1,自引:0,他引:1  
对张继的《枫桥夜泊》,历史上有过很多种探讨。但这首诗的魅力究竟何在,而使它久传不衰呢?钟声所表达的禅机正是破解这个谜的关键所在。  相似文献   
172.
In many situations,we are interested in selection of important variables whichare adequate for prediction under a linear regression model.In this paper,a fast selectionprocedure is proposed and is proved to be strongly consistent.Also,the convergence rate ofmisjudgement probability is given.  相似文献   
173.
Summary The decrease of haemolymph phagocytic cells (SH) inPlanorbarius corneus after bacterial injection seems to be mediated by humoral factor(s) released into the haemolymph. SH show different adhesiveness in vitro in the presence of bacterial metabolic products.  相似文献   
174.
从分子热运动的微观角度阐述了物质的5种存在状态,提出了关于物质的状态教学改革的建议。  相似文献   
175.
A part of the revival of interest in Mach׳s principle since the early 1960s has involved work by physicists aimed at calculating various sorts of frame-dragging effects by matter shells surrounding an interior region, and arguing that under certain conditions or in certain limits (ideally, ones that can be viewed as plausibly similar to conditions in our cosmos) the frame dragging becomes “complete” (e.g. Lynden-Bell, Katz, & Bičák, 1995) . Such results can bolster the argument for the satisfaction of Mach׳s principle by certain classes of models of GR. Interestingly, the frame-dragging “effect” of (say) a rotational movement of cosmic matter around a central point is argued by these physicists to be instantaneous—not an effect propagating at the speed of light. Not all physicists regard this as unproblematic. But rather than exploring whether there is something unphysical about such instantaneous “action at a distance”, or a violation of the precepts of Special Relativity, I am interested in exploring whether these physicists׳ calculations should be thought of as showing local inertia (resistance to acceleration) to be an effect, with distant matter distributions being the cause. I will try to apply some leading philosophical accounts of causation to the physical models of frame dragging, to see whether they imply that the frame dragging is superluminal causation. I will then offer reflections on the difficulties of applying causal talk in physical theories.  相似文献   
176.
《Journal of Natural History》2012,46(12):1859-1863
Material previously identified as Piezodorus hybneri (Gmelin) from the Australasian region is here described as a new species, P. grossi sp. nov. The two species can be distinguished on the basis of the aedeagus in the male and spermathecal proximal duct in the female.  相似文献   
177.
《Journal of Natural History》2012,46(39-40):2567-2571
ABSTRACT

Biological invasions can have serious consequences for native communities. The Asian date mussel Arcuatula senhousia is an Asian species that has been accidentally introduced into coastal areas of North America, Oceania and the Mediterranean, with significant impact on local benthic communities. Here, we present the first record of this species in West Africa, after having found one live specimen in a mudflat off the island of Bubaque, in the Bijagós archipelago of Guinea-Bissau. Given the importance of the benthic communities for wintering shorebirds and local fisheries at this key West African wetland, and considering the invasive behaviour of Asian date mussels, we recommend further monitoring to confirm whether a self-maintaining population has settled in the area.  相似文献   
178.
A total of 36 syllid specimens preserved on permanent slides, which were collected and identified by G. Cognetti, and deposited at the Museum of the Stazione Zoologica “Anton Dohrn” in Naples, Italy, were re‐examined. Among the material, two new species of Autolytus, Autolytus antondohrni sp. nov. and A. cognettii sp. nov., were found and are described. Three new combinations are assigned: Autolytus mediterraneus (Cognetti, 1953), Exogone (Parexogone) meridionalis (Cognetti, ) and Syllis alternata Moore, 1908. Four lectotypes are designated for Autolytus convolutus Cognetti, 1953, A. mediterraneus (Cognetti, 1953), A. neapolitanus Cognetti, 1953 and Exogone (Parexogone) meridionalis (Cognetti, ). Proceraea scapularis (Claparède, ) is resurrected.  相似文献   
179.
依据《本草纲目》这一巨著,主要从植物名称训诂、植物分类学、植物形态描述及其生长环境等角度阐述李时珍对民族植物学的贡献。  相似文献   
180.
随着多媒体计算机的逐步增多,自然会出现一些故障,本文分析了常见故障并给出了解决办法  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