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   23061篇
  免费   4142篇
  国内免费   3714篇
化学   17570篇
晶体学   408篇
力学   1388篇
综合类   246篇
数学   2402篇
物理学   8903篇
  2024年   49篇
  2023年   526篇
  2022年   695篇
  2021年   955篇
  2020年   1041篇
  2019年   1121篇
  2018年   911篇
  2017年   870篇
  2016年   1195篇
  2015年   1190篇
  2014年   1422篇
  2013年   1748篇
  2012年   2069篇
  2011年   2067篇
  2010年   1649篇
  2009年   1509篇
  2008年   1520篇
  2007年   1292篇
  2006年   1322篇
  2005年   1198篇
  2004年   897篇
  2003年   760篇
  2002年   793篇
  2001年   682篇
  2000年   513篇
  1999年   447篇
  1998年   328篇
  1997年   299篇
  1996年   301篇
  1995年   243篇
  1994年   228篇
  1993年   182篇
  1992年   143篇
  1991年   148篇
  1990年   115篇
  1989年   98篇
  1988年   73篇
  1987年   47篇
  1986年   65篇
  1985年   48篇
  1984年   25篇
  1983年   25篇
  1982年   16篇
  1981年   8篇
  1980年   11篇
  1975年   7篇
  1972年   7篇
  1965年   6篇
  1964年   5篇
  1959年   4篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
A two‐dimensional (2D) carbon nanofilm with uniform artificial nanopores is an ideal material to ultimately suppress the fuel permeation in the proton exchange membrane fuel cells. Graphdiyne has great mechanical strength, high dimensional stability, and controllable nanopores, and has good prospects to play this crucial role. It is found that graphdiyne nanofilm with amino groups and natural nanopores can be easily prepared with high integrity. The aminated graphdiyne has good compatibility with the Nafion matrix owing to the acid–base interaction between them. The excellent comprehensive properties of graphdiyne in selectivity, dimensional stability, and integrity effectively improve the power performance and stability of fuel cells at wide temperature. Our results can be developed into a universal method that can easily realize the selective separation of ions and small molecules, and open a new way for the emerging applications in green energy.  相似文献   
962.
Dong  Zhengcheng  Tian  Meng  Tang  Ruoli  Li  Xin  Lai  Jingang 《Nonlinear dynamics》2020,100(3):2287-2298
Nonlinear Dynamics - It is an effective way to improve network robustness by adding connectivity links. Although some addition strategies have been proposed, the addition cost in spatial networks...  相似文献   
963.
In recent years, nanomaterial-based drug delivery carriers have become some of the most attractive to be studied. The purpose of this study is to investigate the interaction of C60 fullerene, carbon nanotube and graphene having porphyrin-like FeN4 clusters with a non-steroidal anti-inflammatory drug (ibuprofen) by means of the density functional theory. Results showed that the graphene with FeN4 clusters could remarkably increase the tendency of graphene for adsorption of ibuprofen drug. Also, our ultraviolet–visible results show that the electronic spectra of the complexes exhibit a blue shift toward lower wavelengths (higher energies). It was found that Ibp/FeN4-graphene had high chemical reactivity, which was important for binding of the drug onto the target site. In order to go further and gain insight into the binding features of considered systems with ibuprofen drug, the Atoms in Molecules analysis was performed. Our results determine the electrostatic features of the Ibp/FeN4-graphene bonding. Consequently, the results demonstrated that the FeN4-graphene could be used as potential carriers for the delivery of ibuprofen drug.  相似文献   
964.
965.
966.
Preface     
<正>Biophysical chemistry is a relatively new branch of physical chemistry.Wikipedia-the free encyclopedia describes it with the following sentences(http://en.wikipedia.org/wiki/Biophysical_chemistry,cited on November 2,2014):"Biophysical chemistry is a physical science that uses the concepts of physics and physical chemistry for the study of  相似文献   
967.
Journal of Thermal Analysis and Calorimetry - Ettringite is an important cement hydration product and has a significant effect on cement performance. H-ettringite (synthesized by hydration...  相似文献   
968.
Water-soluble triplet sensitizer with permethyl-β-cyclodextrin(PMCD) grafting on a Schiff-base Pt(Ⅱ)complex(Pt-2),in which PMCD unit serves as a host for binding the acceptors and the Schiff-base Pt(Ⅱ)complex serves as a triplet sensitizer,was synthesized to investigate the effect of supramolecular complexation and assembly on the triplet-triplet annihilation upconversion emission in water.9,10-Diphenylanthracence(DPA) carboxylate(A-1) and its dimer(A-2) in which two DPA carboxylate were covalently linked with an alkyl chain were synthesized as triplet acceptors which also play a role of guest molecules for PMCD.A-1 and A-2 showed high affinity with PMCD,and A-2 can readily aggregate in water and form micron sized assemblies due to the hydrophobic effect and π-π stacking of anthracene core in A-2.The efficiency of TTA-UC was demonstrated to be enhanced by a synergistic effect of host-guest complexation of Pt-2 with A-2 and the self-aggregation of the acceptor A-2,which facilitated the energy transfer and energy fusion among donor and acceptor.  相似文献   
969.
The very recent advances in chiral phosphoric acids (CPAs) catalyzed asymmetric reactions are discussed.  相似文献   
970.
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