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   131806篇
  免费   24798篇
  国内免费   12767篇
化学   106635篇
晶体学   1413篇
力学   6223篇
综合类   666篇
数学   14397篇
物理学   40037篇
  2024年   246篇
  2023年   2001篇
  2022年   3593篇
  2021年   3692篇
  2020年   5014篇
  2019年   5965篇
  2018年   4369篇
  2017年   3759篇
  2016年   7690篇
  2015年   7675篇
  2014年   8740篇
  2013年   10983篇
  2012年   11587篇
  2011年   11301篇
  2010年   9029篇
  2009年   8786篇
  2008年   8622篇
  2007年   7442篇
  2006年   6776篇
  2005年   5989篇
  2004年   4826篇
  2003年   4028篇
  2002年   4468篇
  2001年   3429篇
  2000年   3135篇
  1999年   2380篇
  1998年   1770篇
  1997年   1594篇
  1996年   1580篇
  1995年   1384篇
  1994年   1255篇
  1993年   1026篇
  1992年   922篇
  1991年   800篇
  1990年   666篇
  1989年   517篇
  1988年   391篇
  1987年   346篇
  1986年   347篇
  1985年   283篇
  1984年   201篇
  1983年   163篇
  1982年   139篇
  1981年   87篇
  1980年   68篇
  1979年   29篇
  1978年   31篇
  1977年   41篇
  1976年   33篇
  1975年   27篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
The title compound, [HgCl2(C10H8N2)]n, features two‐dimensional [HgCl2(4,4′‐bipy)]n neutral networks (4,4′‐bipy is 4,4′‐bipyridine), based on an octahedral Hg atom coordinated by four μ2‐Cl atoms and two μ2‐4,4′‐bipy ligands in trans positions, yielding a HgCl4N2 octahedron. The structure has mmm symmetry about the Hg atoms, with most of the atoms on at least one mirror plane, but the unsubstituted C atoms of the 4,4′‐bipy rings are disordered across a mirror plane. Photoluminescent investigations reveal that the title compound displays a strong emission in the green region, which probably originates from a ligand‐to‐ligand charge‐transfer transition.  相似文献   
994.
In the title complex, [Mn(SO4)(C3H7NO)(H2O)2]n, each MnII ion has a distorted octahedral geometry formed by three O atoms of three different sulfate groups, one O atom of a dimethylformamide ligand and two water molecules. The sulfate groups act as tridentate bridging ligands connecting the MnII ions into a two‐dimensional layer structure which can be regraded as a 4.82 network.  相似文献   
995.
996.
隆正文  刘波  李子平 《物理学报》2004,53(7):2094-2099
对约束系统量子化中Dirac方法和 Faddeev-Jackiw方法进行了讨论,并对它们的运动方程、正则量子化的等价性进行证明.找出了两种方法中约束的对应关系. 关键词: Faddeev-Jackiw方法 Dirac方法 约束系统 正则量子化  相似文献   
997.
Two series of size‐fractionated combusted residues, a bag‐house ash and a scrubber residue, from a municipal solid waste incinerator (MSWI) were prepared and extracted by means of sequential chemical extraction (SCE) procedures proposed by Tessier. Concentrations of water‐soluble phase, exchangeable phase, carbonated phase, Fe/Mn oxide phase, organic matter phase, and residual phase bound amphoteric metals (Pb and Zn) were obtained, and have been compared with those of single batch extraction of toxic characteristic leaching procedure (TCLP). In each size fraction of baghouse ash or scrubber residue, lead or zinc shows a common phenomena that the TCLP value is always lower than the content of the water‐soluble fraction. For lead, baghouse ash has a significant size‐dependent distribution on the water‐soluble phase to perform a size‐dependent test of lead in the TCLP test. The zinc TCLP data having less size dependence might be due to that neither the baghouse ash nor the scrubber residue has a size‐dependent distribution on the water‐soluble zinc phase.  相似文献   
998.
Water-soluble fullerenes not only have a number of important applications in biological chemistry1, but also form ordered aggregate structures that can be utilized in materials science2. There are reports that some water-soluble fullerene derivatives can form ordered structures in water, such as vesicle, nanorod and nanoparticle2-5. However, relatively few reports on the aggregation process have been reported. Knowledge of factors that affect the cluster formation in solution is of consider…  相似文献   
999.
X-ray absorption spectra of plasmas   总被引:1,自引:0,他引:1  
In this paper we present a theoretical method to calculate the absorption spectra of hot dense plasmas. Based on our fully relativistic treatment incorporated with the quantum defect theory to handle the huge number of transition arrays from many configurations with high principal quantum number, we can calculate the absorption spectra for any element or multi-element plasmas with little computational efforts. We calculate the absorption spectra of C10H1605 plasmas, which are in good agreement with the experimental spectra. We can then provide diagnostic analysis for plasmas in relevant inertial confinement fusion (lCF) experiments; namely not only to determine plasmas' temperatures and densities, but also to provide the population densities of various ionic stages. Our theoretical method verified by "benchmark experiments" will be a basic tool to provide "precise" opacity data for the ICF research.``  相似文献   
1000.
Supported in part by NSF grant No. DMS-9003999  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