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   48325篇
  免费   1353篇
  国内免费   340篇
化学   26750篇
晶体学   523篇
力学   1690篇
综合类   28篇
数学   9939篇
物理学   11088篇
  2023年   713篇
  2022年   993篇
  2021年   1611篇
  2020年   1951篇
  2019年   1303篇
  2018年   1683篇
  2017年   1958篇
  2016年   1859篇
  2015年   1918篇
  2014年   2536篇
  2013年   3456篇
  2012年   2603篇
  2011年   2528篇
  2010年   2392篇
  2009年   2213篇
  2008年   1881篇
  2007年   2109篇
  2006年   2195篇
  2005年   1671篇
  2004年   1254篇
  2003年   1217篇
  2002年   1138篇
  2001年   1475篇
  2000年   876篇
  1999年   1225篇
  1998年   753篇
  1997年   491篇
  1996年   243篇
  1995年   186篇
  1994年   185篇
  1993年   178篇
  1992年   334篇
  1991年   271篇
  1990年   303篇
  1989年   149篇
  1988年   128篇
  1987年   136篇
  1986年   141篇
  1985年   237篇
  1984年   230篇
  1983年   78篇
  1982年   146篇
  1981年   121篇
  1980年   127篇
  1979年   111篇
  1978年   136篇
  1977年   80篇
  1976年   95篇
  1974年   82篇
  1973年   98篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
32.
Computational modeling of the optical characteristics of organic molecules with potential for thermally activated delayed fluorescence (TADF) may assist markedly the development of more efficient emitting materials for organic light-emitting diodes. Recent theoretical studies in this area employ mostly methods from density functional theory (DFT). In order to obtain accurate predictions within this approach, the choice of a proper functional is crucial. In the current study, we focus on testing the performance of a set of DFT functionals for estimation of the excitation and emission energy and the excited singlet-triplet energy gap of three newly synthesized compounds with capacity for TADF. The emitters are designed specifically to enable charge transfer by π-electron conjugation, at the same time possessing high-energy excited triplet states. The functionals chosen for testing are from various groups ranging from gradient-corrected through global hybrids to range-separated ones. The results show that the monitored optical properties are especially sensitive to how the long-range part of the exchange energy is treated within the functional. The accurate functional should also be able to provide well balanced distribution of the π-electrons among the molecular fragments. Global hybrids with moderate (less than 0.4) share of exact exchange (B3LYP, PBE0) and the meta-GGA HSE06 are outlined as the best performing methods for the systems under study. They can predict all important optical parameters correctly, both qualitatively and quantitatively.  相似文献   
33.
Journal of Radioanalytical and Nuclear Chemistry - Responses of the hand-held gamma monitors available for the ambient dose equivalent rate measurements in the Federation of Bosnia and Herzegovina...  相似文献   
34.
Crystallography Reports - The crystal structure and crystallochemical features of a Fe-deficient zirconium-rich analog of eudialyte from the Lovozero alkaline massif (Kola peninsula) have been...  相似文献   
35.
36.
In this paper, we studied commercially available precipitated rice husk silica (RHS) with conventional precipitated silica, which has nearly the same surface area, and replaced part of the carbon black with RHS and conventional silica in a basic tread formulation. All formulations were mixed with the same amount of filler during the study. Silica was used at 15, 30 and 50 phr loading, and part of the carbon black was replaced by silica. Compound curing characteristics, physical properties, rebound resilience, heat generation, abrasion loss, dynamic properties and morphology were analyzed. The results indicated that RHS demonstrated compound properties comparable to those of conventional silica. As part of the carbon black was replaced with conventional silica, a slower cure rate, higher rebound resilience, lower heat generation, lower abrasion loss, and lower tan delta were observed with no significant change in physical properties, but some changes in physical properties were observed using one way ANOVA analysis. We found the same trend when replacing part of the carbon black with RHS, such as a slower cure rate, higher rebound resilience, lower heat generation, lower abrasion loss, and lower tan delta with no significant change in physical properties, but some changes in physical properties were observed using one way ANOVA. This sustainable material could be used to replace conventional silica in tire compounding, as well as to replace a portion of carbon black with RHS for improved heat build-up, rolling resistance, and abrasion loss.  相似文献   
37.
The European Physical Journal B - This paper reports on the dynamical analysis, field programmable gate array (FPGA) implementation of autonomous Josephson junction (JJ) jerk oscillator with cosine...  相似文献   
38.
39.
Central European Journal of Operations Research - Digital competences are among the most important competences in modern society, with the education system playing a key role in the acquisition of...  相似文献   
40.
In this paper,we first construct compact embeddedλ-hypersurfaces with the topology of torus which are calledλ-torus in Euclidean spaces?n^+1.Then,we give many compact immersedλ-hypersurfaces in Euclidean spaces?n^+1.  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