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   146996篇
  免费   2706篇
  国内免费   505篇
化学   66514篇
晶体学   1129篇
力学   8005篇
综合类   2篇
数学   43405篇
物理学   31152篇
  2023年   408篇
  2022年   423篇
  2021年   819篇
  2020年   1041篇
  2019年   892篇
  2018年   11503篇
  2017年   11103篇
  2016年   7986篇
  2015年   2540篇
  2014年   2189篇
  2013年   4329篇
  2012年   7256篇
  2011年   14065篇
  2010年   7734篇
  2009年   7862篇
  2008年   10003篇
  2007年   12115篇
  2006年   3521篇
  2005年   4281篇
  2004年   3999篇
  2003年   4011篇
  2002年   2890篇
  2001年   1737篇
  2000年   1643篇
  1999年   1153篇
  1998年   998篇
  1997年   970篇
  1996年   1182篇
  1995年   928篇
  1994年   949篇
  1993年   967篇
  1992年   826篇
  1991年   696篇
  1990年   711篇
  1989年   625篇
  1988年   606篇
  1987年   592篇
  1986年   557篇
  1985年   788篇
  1984年   786篇
  1983年   657篇
  1982年   692篇
  1981年   701篇
  1980年   648篇
  1979年   560篇
  1978年   600篇
  1977年   559篇
  1976年   509篇
  1975年   470篇
  1973年   447篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Journal of Analytical Chemistry - The present development involved a flow injection strategy using a mini-column of multiwalled carbon nanotubes and fluorescent detection (λex of 283 nm,...  相似文献   
2.
Meccanica - In this work we study, from the numerical point of view, a one-dimensional thermoelastic problem where the thermal law is of type III. Quasi-static microvoids are also assumed within...  相似文献   
3.
Central European Journal of Operations Research - Sustainability practice within supply chains remains in an early development phase. Enterprises still need tools that support the integration of...  相似文献   
4.
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   
5.
6.
In a 2:2 reaction with silver(I) chloride or bromide, 1,5-bis(1-phospholano)pentane ( 1a ) afforded frame-like macrocyclic structures, with intra- ( 2 , Cl) or intermolecular ( 3 , Br) halido bridges. In contrast, 1,7-bis(1-phospholano)heptane ( 1b ) formed coordination polymers 4a (Cl) and 4b (Br) with bridging bis-phospholane and halido ligands. A unique paddle wheel-type metallacryptand structure 5 was obtained from 1a and silver(I) bromide in a 2:3 reaction (M:L). All complexes were fully characterized by NMR, IR spectroscopy, mass spectrometry, and X-ray crystallography.  相似文献   
7.
To achieve efficient proton pumping in the light-driven proton pump bacteriorhodopsin (bR), the protein must be tightly coupled to the retinal to rapidly convert retinal isomerization into protein structural rearrangements. Methyl group dynamics of bR embedded in lipid nanodiscs were determined in the dark-adapted state, and were found to be mostly well ordered at the cytosolic side. Methyl groups in the M145A mutant of bR, which displays only 10 % residual proton pumping activity, are less well ordered, suggesting a link between side-chain dynamics on the cytosolic side of the bR cavity and proton pumping activity. In addition, slow conformational exchange, attributed to low frequency motions of aromatic rings, was indirectly observed for residues on the extracellular side of the bR cavity. This may be related to reorganization of the water network. These observations provide a detailed picture of previously undescribed equilibrium dynamics on different time scales for ground-state bR.  相似文献   
8.
In the paper, the authors establish several integral representations for the generating functions of the large and little Schröder numbers and for the large and little Schröder numbers.  相似文献   
9.
10.
Mesoscopic modeling at the pore scale offers great promise in exploring the underlying structure transport performance of flow through porous media. The present work studies the fluid flow subjected to capillarity-induced resonance in porous media characterized by different porous structure and wettability. The effects of porosity and wettability on the displacement behavior of the fluid flow through porous media are discussed. The results are presented in the form of temporal evolution of percentage saturation and displacement of the fluid front through porous media. The present study reveals that the vibration in the form of acoustic excitation could be significant in the mobilization of fluid through the porous media. The dependence of displacement of the fluid on physicochemical parameters like wettability of the surface, frequency along with the porosity is analyzed. It was observed that the mean displacement of the fluid is more in the case of invading fluid with wetting phase where the driving force strength is not so dominant.  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