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   1260篇
  免费   152篇
  国内免费   100篇
化学   1093篇
晶体学   14篇
力学   40篇
综合类   2篇
数学   97篇
物理学   266篇
  2024年   3篇
  2023年   18篇
  2022年   30篇
  2021年   33篇
  2020年   58篇
  2019年   52篇
  2018年   26篇
  2017年   17篇
  2016年   48篇
  2015年   53篇
  2014年   57篇
  2013年   85篇
  2012年   111篇
  2011年   120篇
  2010年   79篇
  2009年   56篇
  2008年   79篇
  2007年   51篇
  2006年   91篇
  2005年   65篇
  2004年   47篇
  2003年   50篇
  2002年   45篇
  2001年   28篇
  2000年   28篇
  1999年   34篇
  1998年   13篇
  1997年   14篇
  1996年   13篇
  1995年   16篇
  1994年   10篇
  1993年   8篇
  1992年   7篇
  1991年   20篇
  1990年   5篇
  1989年   5篇
  1987年   4篇
  1986年   5篇
  1985年   3篇
  1984年   3篇
  1983年   2篇
  1982年   2篇
  1979年   2篇
  1976年   1篇
  1975年   4篇
  1974年   2篇
  1973年   1篇
  1971年   1篇
  1970年   2篇
  1966年   2篇
排序方式: 共有1512条查询结果,搜索用时 13 毫秒
81.
CHARACTERIZATIONOFRADIATIONGRAFTCOPOLYMEROFINORGANICCOMPOUNDONTOALKENEZhangWanxi;CheJitai;YanMeilan(ChangchuninstituteofAppli...  相似文献   
82.
螯合型二甘醇钛酸酯的合成及其催化性能研究   总被引:3,自引:0,他引:3  
苏瑞兰  莫欣 《合成化学》1995,3(3):267-270
报导了两种新的螯合型二甘醇钛酸酯的合成方法,进行了IR和UV鉴定,并作为酯化反应催化剂催化合成了邻苯二甲酸二辛酯。研究了酯化反应转化率与反应时间、反应温度及催化剂用量的关系,探讨了催化剂结构与催化性能的关系。  相似文献   
83.
84.
85.
86.
在真空条件下完成了X2 (X=Cl、Br)与AgOCN间的气-固异相反应,利用紫外光电子能谱(PES)仪,探测与确定反应产物是XNCO (X=Cl、Br),并推断其可能为一过渡态反应,生成中间络合物,新键产生与旧键断裂同时进行.  相似文献   
87.
Molecular beam surface scattering and X-ray absorption spectroscopic experiments were employed to study the reaction of deuterium atoms with a pyrite, FeS(2) (100), surface and to investigate the electronic and geometric structures of the resulting Fe-S phases. Incident D atoms, produced by a radiofrequency plasma and expanded in an effusive beam, were directed at a pyrite surface held at various temperatures from ambient up to 200 °C. During exposure to the D-atom beam, D(2)S products were released with a thermal distribution of molecular speeds, indicating that the D atoms likely reacted in thermal equilibrium with the surface. The yield of D(2)S from the surface decreased approximately exponentially with exposure duration, suggesting that the surface accessible sulfur atoms were depleted, thus leaving an iron-rich surface. This conclusion is consistent with X-ray absorption measurements of the exposed surfaces, which indicated the formation of a layered structure, with elemental iron as the outermost layer on top of a formally Fe((I))-S phase as an intermediate layer and a formally Fe((II))-S(2) bulk pyrite layer at lower depths. The reduced Fe((I))-S phase is particularly remarkable because of its similarity to the catalytically active sites of small molecule metalloenzymes, such as FeFe-hydrogenases and MoFe-nitrogenases.  相似文献   
88.
This article describes the structure determination of five homoleptic d(10) metal-aryl/alkylacetylides [RC triple bond CM] (M=Cu, R=tBu 1, nPr 2, Ph 3; R=Ph, M=Ag 4; Au 5) by using X-ray single-crystal and powder diffraction. Complex 1.C6H6 reveals an unusual Cu20 catenane cluster structure that has various types of tBuC triple bond C-->Cu coordination modes. By using this single-crystal structure as a starting model for subsequent Rietveld refinement of X-ray powder diffraction data, the structure of the powder synthesized from CuI and tBuC triple bond CH was found to have the same structure as 1. Complex 2 has an extended sheet structure consisting of discrete zig-zag Cu4 subunits connected through bridging nPrC triple bond C groups. Complex 3 forms an infinite chain structure with extended Cu-Cu ladders (Cu-Cu=2.49(4)-2.83(2) A). The silver(I) congener 4 is iso-structural to 3 (average Ag-Ag distance 3.11 A), whereas the gold(I) analogue 5 forms a Au...Au honeycomb network with PhC triple bond C pillars (Au-Au=2.98(1)-3.26(1) A). Solid-state properties including photoluminescence, nu(C triple bond C) stretching frequencies and thermal stability of these polymeric systems are discussed in the context of the determined structures.  相似文献   
89.
IntroductionRecently ,considerableinteresthasbeendevotedtoassemblingnanoscalebuildingblockswithvariousinor ganicand/ororganiccompositionsintoultrathinmultilay eredfilmsbyversatileassemblingstrategiesasthesefilmscanoffergreatpotentialforapplicationssuch…  相似文献   
90.
The interaction between fullerene C60 and heparin was studied using a fullerene C60‐coated piezoelectric quartz crystal sensor. The irreversible response of the piezoelectric quartz crystal was found which could be attributed to the quite strong adsorption of heparin onto the C60 molecule. Immobilized fullerene C60‐Heparin was prepared and successfully applied as a good inhibitor for blood clotting. Like solvated heparin, both wet and dry C60‐heparin solid all demonstrated excellent ability of anticoagulation of blood. The blood clotting time with C60‐heparin solid was found to be > 7 days, while only 17.9 min required for blood clotting time in the absence of C60‐heparin solid. Furthermore, the C60‐heparin coated artificial PVC blood vessels were prepared by coating fullerene C60 onto the surface of artificial PVC blood vessels, followed by the adsorption of water solvated heparin onto the fullerene C60 molecule to form C60‐heparin coating. The blood clotting time of blood in artificial PVC blood vessels with C60‐heparin coating was found to be > 30 days, while only ≤ 30 min. of blood clotting time without the C60‐Heparin coating was observed. The C60‐heparin coated artificial PVC blood vessels can be expected to be employed in human body for the anticoagulation of blood.  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