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   58899篇
  免费   775篇
  国内免费   302篇
化学   27370篇
晶体学   1026篇
力学   3199篇
综合类   8篇
数学   4652篇
物理学   23721篇
  2022年   536篇
  2021年   479篇
  2020年   446篇
  2019年   427篇
  2018年   571篇
  2017年   496篇
  2016年   891篇
  2015年   634篇
  2014年   988篇
  2013年   2496篇
  2012年   2331篇
  2011年   3012篇
  2010年   2124篇
  2009年   2174篇
  2008年   2750篇
  2007年   2587篇
  2006年   2452篇
  2005年   2174篇
  2004年   1983篇
  2003年   1754篇
  2002年   1648篇
  2001年   3005篇
  2000年   2148篇
  1999年   1554篇
  1998年   1080篇
  1997年   1057篇
  1996年   884篇
  1995年   783篇
  1994年   704篇
  1993年   623篇
  1992年   951篇
  1991年   946篇
  1990年   849篇
  1989年   747篇
  1988年   731篇
  1987年   795篇
  1986年   654篇
  1985年   882篇
  1984年   828篇
  1983年   568篇
  1982年   562篇
  1981年   534篇
  1980年   496篇
  1979年   620篇
  1978年   650篇
  1977年   660篇
  1976年   575篇
  1975年   481篇
  1974年   521篇
  1973年   450篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Meng  Y.  Cai  B.  Lan  Q.  Niu  F.  Zhang  X.  Yang  Y. 《Crystallography Reports》2022,67(2):224-228
Crystallography Reports - A di-nuclear uranyl complex with the formula of [(UO2)2(L)4(H2O)2]?4H2O (1) (HL = quinoline-6-carboxylic acid) was synthesized hydrothermally and characterized by...  相似文献   
992.
Crystallography Reports - Molecular dynamics simulations of horse heart cytochrome C were performed in an aqueous solution and in a 50 : 50 water–methanol mixture. Three independent 100-ns...  相似文献   
993.
Crystallography Reports - An Erratum to this paper has been published: https://doi.org/10.1134/S1063774521340034  相似文献   
994.
Films were obtained by coalescence of different types of latex particles; the purpose of this work was to get informations on the geometric arrangement (so called “morphology”) of the different phases and on the role of interfaces. Such informations are difficult to get by direct investigations (weak contrast in Transmission Electron Microscopy, poor information provided by X-ray measurements on amorphous polymers …) the analysis of experimental data obtained in high resolution mechanical spectrometry appears powerful: it is possible, for instance, to estimate the profile gradient of composition at the interface. Comparison is made between the morphology of the different phases in some films and the correspondent structure of particles.  相似文献   
995.
Growth processes, structure and properties of Fe, Co, FeCo deposited alumite films have been investigated. It is shown that the magnetic characteristics depends both on alumite film parameters and properties of deposited metal (alloy) particles.  相似文献   
996.
The mixed crystal (K1-xCsx)2ZnCl4 with x = 0, 0.001, 0.01, 0.1, and 0.2 with optical quality has been grown by the Czochralski method. Using the Atomic Absorption Spectroscopy (AAS) and Energy Dispersive Spectroscopy (EDS), we determined the amount of Cs ion included in the mixed crystal. By using of DTA and DSC, we observed the change of Tc and Ti. The thermal hysteresis in the dielectric constants show strong dependence on the thermal process and on the amount of impurity which are explained by the influence of the thermal process and impurity, respectively on the creation, annihilation, and growth of discommensuration (DC).  相似文献   
997.
Crystallography Reports - The review describes the application of small-angle scattering (SAS) of neutrons and complementary methods to study the structures of biomacromolecules. Here we cover SAS...  相似文献   
998.
The conformation of five aromatic molecules were calculated using the atom-atom potentials method. The deformations of valency angles were not considered, and the conformations of some molecules were determined solely by the minimum interaction energy between non-bounded pairs of atoms. In case of molecules having π-bonds, the geometry of the isolated molecule was determined by the balance between the π-electron and the non-bonded energies. A comparison is made between the structure of molecules in the crystal form and the structure of the free molecules determined by conformational analysis. For terphenyl molecule which has different structures in the different phases, a calculation of the structure of molecule in crystal from was done theoretically using lattice energy minimization. Good agreement was found between structures obtained theoretically and experimentally.  相似文献   
999.
Polypyrrole, formed in an organic solvent, shows higher density and better quality in electrical conductivity and mechanical strength than that formed in water. On electrochemical reduction in an aqueous system the laurylsulfate anion, used as dopant, sticks to the polymer. During reduction a cation moves into the polymer and on oxidation it leaves the polymer. The anion, however, leaves the polymer on reduction in an organic solvent system and cannot penetrate into the polymer on re-oxidation. The redox reaction in the aqueous system reveals a surface reaction process, while the reaction in the organic solvent system undergoes a diffusion-controlled process. This penomenon is consistant with the results of the ion concentration profile.  相似文献   
1000.
During liver fibrogenesis, there is an imbalance between regeneration and wound healing. The current treatment is the withdrawal of the causing agent; thus, investigation of new and effective treatments is important. Studies have highlighted the action of chondroitin sulfate (CS) in different cells; thus, our aim was to analyze its effect on an experimental model of bile duct ligation (BDL). Adult Wistar rats were subjected to BDL and treated with CS for 7, 14, 21, or 28 days intraperitoneally. We performed histomorphometric analyses on Picrosirius-stained liver sections. Cell death was analyzed according to caspase-3 and cathepsin B activity and using a TUNEL assay. Regeneration was evaluated using PCNA immunohistochemistry. BDL led to increased collagen content with corresponding decreased liver parenchyma. CS treatment reduced total collagen and increased parenchyma content after 21 and 28 days. The treatment also promoted changes in the hepatic collagen type III/I ratio. Furthermore, it was observed that CS treatment reduced caspase-3 activity and the percentage of TUNEL-positive cells after 14 days and cathepsin B activity only after 28 days. The regeneration increased after 14, 21, and 28 days of CS treatment. In conclusion, our study showed a promising hepatoprotective action of CS in fibrogenesis induced by BDL.  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