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   723400篇
  免费   5606篇
  国内免费   2175篇
化学   358547篇
晶体学   9853篇
力学   37629篇
综合类   21篇
数学   115317篇
物理学   209814篇
  2021年   5741篇
  2020年   6336篇
  2019年   7109篇
  2018年   19168篇
  2017年   19018篇
  2016年   18985篇
  2015年   8160篇
  2014年   12478篇
  2013年   28946篇
  2012年   25318篇
  2011年   35675篇
  2010年   24547篇
  2009年   24737篇
  2008年   30919篇
  2007年   32709篇
  2006年   23020篇
  2005年   21681篇
  2004年   20197篇
  2003年   18853篇
  2002年   17844篇
  2001年   18039篇
  2000年   14211篇
  1999年   10873篇
  1998年   9466篇
  1997年   9356篇
  1996年   8830篇
  1995年   7815篇
  1994年   7777篇
  1993年   7621篇
  1992年   8044篇
  1991年   8538篇
  1990年   8175篇
  1989年   8071篇
  1988年   7898篇
  1987年   7666篇
  1986年   7394篇
  1985年   9490篇
  1984年   9920篇
  1983年   8235篇
  1982年   8720篇
  1981年   8141篇
  1980年   7747篇
  1979年   8299篇
  1978年   8711篇
  1977年   8564篇
  1976年   8506篇
  1975年   8086篇
  1974年   7967篇
  1973年   8329篇
  1972年   5976篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
The paper is devoted to the research of large deviation probabilities in the approximation by compound Poisson law.  相似文献   
972.
Experimental data obtained by studying the effect of internal waves with known space-time parameters on the propagation of a 240-Hz tone signal and on the space-time interference structure of the sound field generated by a noiselike sound source are presented.  相似文献   
973.
The effect of the lattice deformation on the electronic spectra of TlGaS2, TlGaSe2, and TlInS2 layered semiconductor crystals is analyzed. It is shown that changes in the band gap of these semiconductors due to thermal expansion and a change in the composition under hydrostatic or uniaxial pressure can be described within a unified model of the deformation potential. The main feature of this model is the inclusion of deformation potentials with different signs, which is characteristic of other semiconductors with a layered structure. An analysis of the lattice deformation of the studied semiconductors in terms of the proposed model of the deformation potential has revealed that, in the immediate vicinity of the phase transitions, the crystal lattice under pressure undergo an unusual deformation.  相似文献   
974.
In this paper, the upper and lower δ-continuous multifunctions in fuzzy setting have been presented as a strong form and an application of fuzzy continuous multifunctions. Certain characterizations and several properties of these fuzzy multifunctions along with their mutual relationships are obtained. Attempts are also made to correlate this new class with the corresponding known types of fuzzy multifunctions. Also, applicability of the above new concepts to superstrings and space time could be probably possible in the near future.  相似文献   
975.
Supply chain management literature calls for coordination between the different members of the chain. Materials should be moved from one supplier to the next according to a just-in-time schedule. In this paper, we show that for many supply chain configurations, complete synchronization will result in some members of the chain being ‘losers’ in terms of cost. We develop an algorithm for optimal synchronization of supply chains and provide some guidelines for incentive alignment along the supply chain. In developing the model, we use the economic delivery and scheduling problem model and analyze supply chains dealing with single and multiple components. For single-component supply chains, we derive a closed-form expression for the optimal synchronized cycle time. For multi-component supply chains, we develop an algorithm for finding the optimal synchronized cycle time. We test the performance of the algorithm and show that it provides optimal solutions for a wide range of problems. We illustrate the models with numerical examples.  相似文献   
976.
N. Elgun  E. A. Davis 《Journal of Non》2003,330(1-3):226-233
Hydrogenated amorphous GaP films have been prepared by reactive rf sputtering. Infrared spectroscopy, optical transmission and reflection, photothermal deflection spectroscopy and dc conductivity have been studied to investigate the local bonding configurations, the optical absorption edges and the temperature dependence of the conductivity as a function of hydrogen content. The results are discussed and compared with the effects of hydrogenation on amorphous Si.  相似文献   
977.
Russian Physics Journal -  相似文献   
978.
Based on an analysis of experimental results and published data, the main elementary steps of the anionic coordination polymerization of butadiene rubber on a cobalt-containing catalyst in the presence of ethylene were found, and a mathematical model of the periodic process at an optimum water content was developed. The molecular-weight characteristics of the process depending on ethylene concentration were studied with the use of this model.  相似文献   
979.
Conditions under which various kinds of carbon nanoparticles are obtained by thermal oxidative conversion of methane in chlorine in the temperature range 20-500°C were studied. The influence exerted by conditions of synthesis of nanodispersed carbon on the properties of its samples was analyzed.  相似文献   
980.
In this paper we show the existence of a solution, on any time intervals, in suitable Sobolev spaces for the 2D compressible Euler equation in the exterior domain, when the Mach number is sufficiently small. We shall extend results obtained in [8] in the case of an infinity velocity different from zero.
Sunto In questo lavoro proviamo l'esistenza di una soluzione, su ogni intervallo temporale, in opportuni spazi di Sobolev per le equazioni di Eulero 2D comprimibili in un dominio esterno, quando il numero di Mach è sufficientemente piccolo. Estenderemo i risultati ottenuti in [8] al caso di velocità all'infinito diversa da zero.
  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