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   136729篇
  免费   11367篇
  国内免费   8444篇
化学   67426篇
晶体学   1709篇
力学   10010篇
综合类   552篇
数学   38043篇
物理学   38800篇
  2024年   213篇
  2023年   1129篇
  2022年   2055篇
  2021年   2202篇
  2020年   2429篇
  2019年   2533篇
  2018年   12105篇
  2017年   11847篇
  2016年   8706篇
  2015年   3772篇
  2014年   3962篇
  2013年   4960篇
  2012年   9269篇
  2011年   15880篇
  2010年   9541篇
  2009年   9853篇
  2008年   10829篇
  2007年   12343篇
  2006年   3904篇
  2005年   4312篇
  2004年   3870篇
  2003年   3812篇
  2002年   2937篇
  2001年   1799篇
  2000年   1584篇
  1999年   1394篇
  1998年   1129篇
  1997年   990篇
  1996年   1049篇
  1995年   854篇
  1994年   684篇
  1993年   600篇
  1992年   487篇
  1991年   459篇
  1990年   370篇
  1989年   314篇
  1988年   234篇
  1987年   195篇
  1986年   223篇
  1985年   175篇
  1984年   117篇
  1983年   118篇
  1982年   96篇
  1981年   86篇
  1980年   68篇
  1979年   64篇
  1978年   43篇
  1914年   45篇
  1909年   41篇
  1908年   40篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Although tremendous efforts have been devoted to understanding the origin of boosted charge storage on heteroatom-doped carbons, none of the present studies has shown a whole landscape. Herein, by both experimental evidence and theoretical simulation, it is demonstrated that heteroatom doping not only results in a broadened operating voltage, but also successfully promotes the specific capacitance in aqueous supercapacitors. In particular, the electrolyte cations adsorbed on heteroatom-doped carbon can effectively inhibit hydrogen evolution reaction, a key step of water decomposition during the charging process, which broadens the voltage window of aqueous electrolytes even beyond the thermodynamic limit of water (1.23 V). Furthermore, the reduced adsorption energy of heteroatom-doped carbon consequently leads to more stored cations on the heteroatom-doped carbon surface, thus yielding a boosted charge storage performance.  相似文献   
62.
63.
64.
65.
66.
The stable phase equilibria of quaternary systems LiBr-NaBr-MgBr2-H2O and LiBr-KBr-MgBr2-H2O at 298.15 K were studied by both experimental measurement(isothermal solution saturation method) and theoretical prediction(Pitzer model). The solubilities of the saturated solution have been determined experimentally and two stable phase diagrams and relevant water diagrams of the two quaternary systems were obtained. Results show that quaternary system LiBr-NaBr-MgBr2-H2O is hydrate II type as NaBr and NaBr·2H2O coexistence. Its phase diagram consists of only one invariant point, four univariant curves, and five crystallization fields. The quaternary system LiBr-KBr-MgBr2-H2O is a complex type as the double salt KBr·MgBr2·6H2O formed. In addition to this double salt, the three single salts LiBr·2H2O, KBr and MgBr2·6H2O also crystallize. In this paper, the solubilities of phase equilibria in above quaternary systems were also calculated by the Pitzer's electrolyte solution model. All the needed parameters can be obtained from the literature or be fitted by experimental data. On the Basis of the experimental and calculated results, the phase diagram of the quaternary system was plotted for comparison. It shows that the calculation results are consistent with the experimental ones.  相似文献   
67.
We give the form of the output function in Ginsburg’s machine in which the input and output dictionaries are abelian groups and the transition function is of a special form.  相似文献   
68.
Shi  D.  Feng  J.  Wang  J.  Zhao  W.  Li  X. 《Kinetics and Catalysis》2020,61(5):750-757
Kinetics and Catalysis - A series of Cu-SSZ-13@CeO2 catalysts with surface modification with CeO2 was prepared by the modified self-resemble method based on the one-pot synthesized Cu-SSZ-13...  相似文献   
69.
70.
Four kinds of red phosphorescent organic light-emitting devices were fabricated and compared to investigate the effect of interfacial layers for hole transport and electron injection. 1 nm-thick LiF in the device A and C and 1 nm-thick Cs2CO3 in the device B and D were deposited as an electron injection layer between the anode and the electron transport layer, and 5 nm-thick layer of dipyrazion[2,3-f:2′,2′-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile[HATCN] was inserted as a hole transport interfacial layer between the hole injection layer and the hole transport layer only in the device C and D. Under a luminance of 1000 cd/m2, the power efficiencies were 7.6 lm/W and 8.5 lm/W in the device A and B, and 8.6 lm/W and 13.4 lm/W in the device C and D. The quantum efficiency of the device D was 15.8% under 1000 cd/m2 which was somewhat lower than those of the device A and C, but a little higher than that of the device B. The luminance of the device D was much higher than those of the other devices at a given votage. The luminance of the device D at 7 V was 23,710 cd/m2, which was 13.0, 3.4, and 4.0 times higher than those of the device A, B, and C at the same voltage, respectively.  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