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   46490篇
  免费   1292篇
  国内免费   12篇
化学   28189篇
晶体学   237篇
力学   760篇
综合类   1篇
数学   8755篇
物理学   9852篇
  2023年   334篇
  2022年   294篇
  2021年   465篇
  2020年   670篇
  2019年   606篇
  2018年   954篇
  2017年   869篇
  2016年   1687篇
  2015年   1393篇
  2014年   1342篇
  2013年   3037篇
  2012年   2874篇
  2011年   2685篇
  2010年   1794篇
  2009年   1499篇
  2008年   2364篇
  2007年   2145篇
  2006年   1913篇
  2005年   1975篇
  2004年   1711篇
  2003年   1419篇
  2002年   1228篇
  2001年   949篇
  2000年   950篇
  1999年   661篇
  1998年   510篇
  1997年   431篇
  1996年   577篇
  1995年   409篇
  1994年   484篇
  1993年   439篇
  1992年   468篇
  1991年   395篇
  1990年   444篇
  1989年   360篇
  1988年   367篇
  1987年   329篇
  1986年   320篇
  1985年   446篇
  1984年   412篇
  1983年   325篇
  1982年   325篇
  1981年   343篇
  1980年   278篇
  1979年   272篇
  1978年   272篇
  1977年   261篇
  1976年   277篇
  1974年   250篇
  1973年   263篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
We study condensation of trapped bosons in the limit when the number of particles tends to infinity. For the noninteracting gas we prove that there is no phase transition in any dimension, but in any dimension, at any temperature the system is 100% condensated into the one-particle ground state. In the case of an interacting gas we show that for a family of suitably scaled pair interactions, the Gross–Pitaevskii scaling included, a less-than-100% condensation into a single-particle eigenstate, which may depend on the interaction strength, persists at all temperatures.  相似文献   
102.
103.
104.
105.
Experiments in dc supplied corona discharge in natural gas + air mixture and in combustion exhaust of natural gas + air mixture were realized. The influence of discharge on CO, CO2, NO x and other minority components was studied using IR absorption spectrometry. Production of NCO radicals in gas and consequent formation of NCO containing surface layers on a plate electrode was detected. In natural gas + air mixture after about 1 min oxygen poor combustion exhaust was produced due to slow combustion by corona discharge. Occurrence of various pulses in discharge current was typical.  相似文献   
106.
The main purpose of this paper is to give a procedure to “mollify” the low-pass filters of a large number ofMinimally Supported Frequency (MSF) wavelets so that the smoother functions obtained in this way are also low-pass filters for an MRA. Hence, we are able to approximate (in the L 2 -norm) MSF wavelets by wavelets with any desired degree of smoothness on the Fourier transform side. Although the MSF wavelets we consider are bandlimited, this may not be true for their smooth approximations. This phenomena is related to the invariant cycles under the transformation x ↦2x (mod2π). We also give a characterization of all low-pass filters for MSF wavelets. Throughout the paper new and interesting examples of wavelets are described.  相似文献   
107.
In this paper, we deal with multicriteria matrix games. Different solution concepts have been proposed to cope with these games. Recently, the concept of Pareto-optimal security strategy which assures the property of security in the individual criteria against an opponent's deviation in strategy has been introduced. However, the idea of security behind this concept is based on expected values, so that this security might be violated by mixed strategies when replications are not allowed. To avoid this inconvenience, we propose in this paper a new concept of solution for these games: the G-goal security strategy, which includes as part of the solution the probability of obtaining prespecified values in the payoff functions. Thus, attitude toward risk together with payoff values are considered jointly in the solution analysis.  相似文献   
108.
It is shown that the non-trivial cocycles on simple Lie algebras may be used to introduce antisymmetric multibrackets which lead to higher-order Lie algebras, the definition of which is given. Their generalised Jacobi identities turn out to be satisfied by the antisymmetric tensors (or higher-order “structure constants”) which characterise the Lie algebra cocycles. This analysis allows us to present a classification of the higher-order simple Lie algebras as well as a constructive procedure for them. Our results are synthesised by the introduction of a single, complete BRST operator associated with each simple algebra. Received: 3 June 1996 / Accepted: 8 November 1996  相似文献   
109.
We present the first single-crystal study of Fe and Ni doped U(Co1-x T x )Al compounds in comparison to the parent compound, the itinerant 5f-electron metamagnet UCoAl. Magnetization and specific-heat data measured in the temperature range of (1.8-300) K and in fields up to 10 T are analyzed and discussed. Both compounds exhibit a strong uniaxial anisotropy with the dominating magnetic response along the c-axis of the hexagonal ZrNiAl-type structure. Ni substitution yields an increase of the critical field for metamagnetism; UCo0.95Fe0.05Al is ferromagnetic below 30 K. Temperature evolution of the entropy change between 0 and 10 T points to involvement of magnetic correlations or spin fluctuations in the paramagnetic compounds UCoAl and UCo0.95Ni0.05Al.  相似文献   
110.
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