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   323985篇
  免费   22356篇
  国内免费   1676篇
化学   205284篇
晶体学   3679篇
力学   13229篇
综合类   66篇
数学   42023篇
物理学   83736篇
  2023年   5036篇
  2021年   4322篇
  2020年   6818篇
  2019年   4517篇
  2018年   6395篇
  2017年   4944篇
  2016年   10758篇
  2015年   9150篇
  2014年   9774篇
  2013年   16354篇
  2012年   15135篇
  2011年   14233篇
  2010年   12591篇
  2009年   11922篇
  2008年   11900篇
  2007年   11597篇
  2006年   10442篇
  2005年   13141篇
  2004年   11641篇
  2003年   9112篇
  2002年   7267篇
  2001年   7670篇
  2000年   5750篇
  1999年   4233篇
  1998年   3517篇
  1997年   3512篇
  1996年   3595篇
  1995年   3248篇
  1994年   3301篇
  1993年   3262篇
  1992年   3553篇
  1991年   3431篇
  1990年   3201篇
  1989年   3082篇
  1988年   3030篇
  1987年   2951篇
  1985年   3868篇
  1984年   3916篇
  1983年   3286篇
  1982年   3569篇
  1981年   3361篇
  1980年   3170篇
  1979年   3370篇
  1978年   3564篇
  1977年   3692篇
  1976年   3802篇
  1975年   3576篇
  1974年   3677篇
  1973年   3551篇
  1972年   2901篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
11.
Aqueous self-assembly of short peptides has attracted growing attention for the construction of supramolecular materials for various bioapplications. Herein, we describe how the thermolysin-assisted biocatalytic construction of a dipeptide hydrazide from an N-protected amino acid and an amino acid hydrazide leads to the formation of thermally stable supramolecular hydrogels. In addition, we demonstrate the post-assembly modification of the supramolecular architectures constructed in situ tethering hydrazide groups as a chemical handle by means of fluorescence imaging.  相似文献   
12.
Journal of Optimization Theory and Applications - We consider a distributionally robust formulation of stochastic optimization problems arising in statistical learning, where robustness is with...  相似文献   
13.
Russian Journal of General Chemistry - The review article traces the main trends of the synthetic approach to the solution of the problem of overcoming the resistance of pathogenic bacterial...  相似文献   
14.
The designs of efficient and inexpensive Pt-based catalysts for methanol oxidation reaction (MOR) are essential to boost the commercialization of direct methanol fuel cells. Here, the highly catalytic performance PtFe alloys supported on multiwalled carbon nanotubes (MWCNTs) decorating nitrogen-doped carbon (NC) have been successfully prepared via co-engineering of the surface composition and electronic structure. The Pt1Fe3@NC/MWCNTs catalyst with moderate Fe3+ feeding content (0.86 mA/mgPt) exhibits 2.26-fold enhancement in MOR mass activity compared to pristine Pt/C catalyst (0.38 mA/mgPt). Furthermore, the CO oxidation initial potential of Pt1Fe3@NC/MWCNTs catalyst is lower relative to Pt/C catalyst (0.71 V and 0.80 V). Benefited from the optimal surface compositions, the anti-corrosion ability of MWCNT, strong electron interaction between PtFe alloys and MWCNTs and the N-doped carbon (NC) layer, the Pt1Fe3@NC/MWCNTs catalyst presents an improved MOR performance and anti-CO poisoning ability. This study would open up new perspective for designing efficient electrocatalysts for the DMFCs field.  相似文献   
15.
In the periodic table the position of each atom follows the ‘aufbau’ principle of the individual electron shells. The resulting intrinsic periodicity of atomic properties determines the overall behavior of atoms in two-dimensional (2D) bonding and structure formation. Insight into the type and strength of bonding is the key in the discovery of innovative 2D materials. The primary features of 2D bonding and the ensuing monolayer structures of the main-group II–VI elements result from the number of valence electrons and the change of atom size, which determine the type of hybridization. The results reveal the tight connection between strength of bonding and bond length in 2D networks. The predictive power of the periodic table reveals general rules of bonding, the bonding-structure relationship, and allows an assessment of published data of 2D materials.  相似文献   
16.
The recognition of boron compounds is well developed as boronic acids but untapped as organotrifluoroborate anions (R−BF3). We are exploring the development of these and other designer anions as anion-recognition motifs by considering them as substituted versions of the parent inorganic ion. To this end, we demonstrate strong and reliable binding of organic trifluoroborates, R−BF3, by cyanostar macrocycles that are size-complementary to the inorganic BF4 progenitors. We find that recognition is modulated by the substituent's sterics and that the affinities are retained using the common K+ salts of R−BF3 anions.  相似文献   
17.
Physics of Atomic Nuclei - In this paper, the analysis of the relation between the multiplication factor of neutrons of the multiplying system measured in critical experiments and the system...  相似文献   
18.
Set-Valued and Variational Analysis - In a Hilbert framework ℌ, we study the convergence properties of a Newton-like inertial dynamical system governed by a general maximally monotone...  相似文献   
19.
Crystallography Reports - The crystal and molecular structures of Cl–C6H4–O–C16H33 (I) have been studied, and its differential scanning calorimetry (DSC) study is performed....  相似文献   
20.
David Hull     
Journal of Optimization Theory and Applications -  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