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   37451篇
  免费   2527篇
  国内免费   2261篇
化学   19184篇
晶体学   277篇
力学   827篇
综合类   633篇
数学   7910篇
物理学   13408篇
  2023年   316篇
  2022年   483篇
  2021年   1292篇
  2020年   852篇
  2019年   899篇
  2018年   709篇
  2017年   712篇
  2016年   1007篇
  2015年   1055篇
  2014年   1341篇
  2013年   2348篇
  2012年   2030篇
  2011年   2263篇
  2010年   1970篇
  2009年   2442篇
  2008年   2421篇
  2007年   2634篇
  2006年   1929篇
  2005年   1215篇
  2004年   1124篇
  2003年   1093篇
  2002年   1135篇
  2001年   1037篇
  2000年   778篇
  1999年   618篇
  1998年   624篇
  1997年   428篇
  1996年   481篇
  1995年   419篇
  1994年   436篇
  1993年   477篇
  1992年   462篇
  1991年   312篇
  1990年   260篇
  1989年   222篇
  1988年   248篇
  1987年   206篇
  1986年   217篇
  1985年   329篇
  1984年   249篇
  1983年   144篇
  1982年   295篇
  1981年   478篇
  1980年   436篇
  1979年   475篇
  1978年   377篇
  1977年   281篇
  1976年   245篇
  1974年   79篇
  1973年   155篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
101.
This article deals with the various heat source responses in a transversely isotropic hollow cylinder under the purview of three-phase-lag (TPL) generalized thermoelasticity theory. In presence of magnetic field and due to the rotating behavior of the cylinder, the governing equations are redefined for generalized thermoelasticity with thermal time delay. In order to obtain the stress, displacement and temperature field, the field functions are expressed in terms of modified Bessel functions in Laplace transformed domain. When the outer radius of hollow cylinder tends to infinity, the corresponding results are discussed. Finally an appropriate Laplace transform inversion technique is adopted.  相似文献   
102.
We prove the existence of solutions to the nonlinear Schrödinger equation ε2(i?+A)2u+V(y)u?|u|p?1u=0 in R2 with a magnetic potential A=(A1,A2). Here V represents the electric potential, the index p is greater than 1. Along some sequence {εn} tending to zero we exhibit complex-value solutions that concentrate along some closed curves.  相似文献   
103.
104.
In this paper, the author gives the discrete criteria and J\o rgensen inequalities of subgroups for the special linear group on $\overline{\mathrm{F}}((t))$ in two and higher dimensions.  相似文献   
105.
106.
107.
108.
109.
Sodium/potassium-ion batteries (SIBs/PIBs) arouse intensive interest on account of the natural abundance of sodium/potassium resources, the competitive cost and appropriate redox potential. Nevertheless, the huge challenge for SIBs/PIBs lies in the scarcity of an anode material with high capacity and stable structure, which are capable of accommodating large-size ions during cycling. Furthermore, using sustainable natural biomass to fabricate electrodes for energy storage applications is a hot topic. Herein, an ultra-small few-layer nanostructured MoSe2 embedded on N, P co-doped bio-carbon is reported, which is synthesized by using chlorella as the adsorbent and precursor. As a consequence, the MoSe2/NP-C-2 composite represents exceedingly impressive electrochemical performance for both sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs). It displays a promising reversible capacity (523 mAh g−1 at 100 mA g−1 after 100 cycles) and impressive long-term cycling performance (192 mAh g−1 at 5 A g−1 even after 1000 cycles) in SIBs, which are some of the best properties of MoSe2-based anode materials for SIBs to date. To further probe the great potential applications, full SIBs pairing the MoSe2/NP-C-2 composite anode with a Na3V2(PO4)3 cathode also exhibits a satisfactory capacity of 215 mAh g−1 at 500 mA g−1 after 100 cycles. Moreover, it also delivers a decent reversible capacity of 131 mAh g−1 at 1 A g−1 even after 250 cycles for PIBs.  相似文献   
110.
Julian G. Sereni 《哲学杂志》2020,100(10):1211-1225
ABSTRACT

With the aim to improve the performance of classical paramagnetic salts for adiabatic refrigeration processes at the sub-Kelvin range, relevant thermodynamic parameters of some new Yb-based intermetallic compounds are analysed and compared. Two main applications are considered: (i) those requiring temperature fixed-points to be reached applying magnetic fields of moderate intensity for satellite applications, and (ii) those which can be used for controlled thermal drifts in laboratory applications. Different thermomagnetic trajectories of the entropy are identified depending on respective specific heat behaviours and the constraints imposed by the Nernst postulate at the sub-Kelvin range. Some simple relationships are proposed to compare the diverse magnetocaloric characteristics of different systems. This procedure allows to include the classical Cerium-Magnesium-Nitride (CMN) salt in that comparison.  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