全文获取类型
收费全文 | 488篇 |
免费 | 7篇 |
国内免费 | 11篇 |
专业分类
化学 | 329篇 |
晶体学 | 1篇 |
力学 | 32篇 |
综合类 | 13篇 |
数学 | 43篇 |
物理学 | 88篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 10篇 |
2021年 | 19篇 |
2020年 | 16篇 |
2019年 | 13篇 |
2018年 | 17篇 |
2017年 | 9篇 |
2016年 | 18篇 |
2015年 | 14篇 |
2014年 | 16篇 |
2013年 | 41篇 |
2012年 | 38篇 |
2011年 | 33篇 |
2010年 | 22篇 |
2009年 | 19篇 |
2008年 | 23篇 |
2007年 | 33篇 |
2006年 | 20篇 |
2005年 | 21篇 |
2004年 | 6篇 |
2003年 | 18篇 |
2002年 | 28篇 |
2001年 | 6篇 |
2000年 | 1篇 |
1999年 | 7篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 1篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1979年 | 3篇 |
1977年 | 2篇 |
1973年 | 1篇 |
1970年 | 2篇 |
1968年 | 2篇 |
1961年 | 1篇 |
1960年 | 1篇 |
1959年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有506条查询结果,搜索用时 328 毫秒
411.
T. Ravishankar K. Chinnakali N. Arumugam P. C. Srinivasan Anwar Usman Hoong‐Kun Fun 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(3):o137-o140
In the title compound, C24H20Br2N2O4S, the indole ring system is planar and the S atom has a distorted tetrahedral configuration. The sulfonyl‐bound phenyl ring is orthogonal to the indole ring system and the conformation of the phenylsulfonyl substituent with respect to the indole moiety is influenced by intramolecular C—H⃛O hydrogen bonds involving the two sulfonyl O atoms. The mean plane through the acetylamido group makes a dihedral angle of 57.0 (1)° with the phenyl ring of the benzyl moiety. In the crystal, glide‐related molecules are linked together by N—H⃛O hydrogen bonds and C—H⃛π interactions to form molecular chains, which extend through the crystal. Inversion‐related chains are interlinked by C—H⃛π interactions to form molecular layers parallel to the bc plane. These layers are interconnected through π–π interactions involving the five‐ and six‐membered rings of the indole moiety. 相似文献
412.
Anwar Usman Hoong‐Kun Fun Suchada Chantrapromma Hai‐Liang Zhu Xian‐Jiang Wang 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(3):m97-m99
In the ternary title compound, catena‐poly[[silver(I)‐μ‐ethylenediamine‐κ2N:N′] 3‐nitrobenzoate monohydrate], {[Ag(C2H8N2)](C7H4NO4)·H2O}n, the Ag atom is bicoordinated in a linear configuration by two different N atoms from two symmetry‐related ethylenediamine ligands, thus giving linear polymeric chains with an [–Ag—N—C—C—N–]n backbone running parallel to the a axis. In the crystal packing, these linear chains are interconnected by N—H⃛O and O—H⃛O hydrogen bonds to form layers parallel to the ab plane. 相似文献
413.
S. Kannan Anwar Usman Hoong‐Kun Fun 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(5):o268-o270
The title compound, meso‐C13H12O2S2, is in an anti conformation, with R and S configurations around the S atoms. The two O atoms are trans to each other, and the same applies for the two benzene rings. The phenylsulfinyl groups are nearly orthogonal to the central dithiomethane group, and the orientation of the two phenyl rings are determined by the interactions in which they are involved. The packing is built from molecular columns stabilized by weak C—H⋯O interactions. 相似文献
414.
塔里木马鹿(Cervus elaphus yarkandensis)且末种群栖息地动态变化分析 总被引:1,自引:0,他引:1
本文采用地理信息系统(GIS)分析方法对1972—2001年车尔臣河中下流域马鹿(Cervus elaphus yarkandensis)栖息地变化进行了研究.结果表明:车尔臣河流域马鹿栖息地从1972-2001年呈现下降趋势,1972年的栖息地总面积为2063.585km^2,其中适宜栖息地有869.894km^2,1990年的栖息地总面积为1916.298km^2,其中适宜栖息地有466.848km^2,2001年的栖息地总面积为1758.485km^2,其中适宜栖息地有222.786km^2,车尔臣河中下流域马鹿现正遭受栖息地质量退缩和适宜栖息地面积不断减少的双重影响. 相似文献
415.
Tariq Hussain Ahmed Anwar Muhammad Malik Abdullah Ali Hafiz Muhammad 《Journal of Thermal Analysis and Calorimetry》2021,145(5):2487-2502
Journal of Thermal Analysis and Calorimetry - Thermal management of microelectronics is a challenging task in modern high heat generating devices. In this work, thermal performance of... 相似文献
416.
Mosleh Mahmoud A. El-Hakim Elham H. Ahmed Anwar Z. El-Ghany Mohamed S. Abd El-Didamony Akram M. 《Journal of Radioanalytical and Nuclear Chemistry》2020,323(2):909-919
Journal of Radioanalytical and Nuclear Chemistry - Impregnation of tri-n-octylamine (TOA) into Siplite LX-16 resin, by two commonly used methods namely; wet and dry impregnation method, was studied... 相似文献
417.
This study aims to use molecular dynamics (MD) simulations of Kremer–Grest (KG) chains to inform future developments of models of entangled polymer dynamics. We perform nonequilibrium MD simulations, under shear flow, for well‐entangled KG chains. We study chains of 512 and 1000 KG beads, corresponding to 8 and 15 entanglements, respectively. We compute the linear rheological properties from equilibrium simulations of the stress autocorrelation and obtain from these data the tube model parameters. Under nonlinear shear flow, we compute the shear viscosity, the first and second normal stress differences, and chain contour length. For chains of 512 monomers, we obtain agreement with the results of Cao and Likhtman (ACS Macro. Lett. 2015, 4, 1376). We also compare our nonlinear results with the Graham, Likhtman and Milner‐McLeish (GLaMM) model. We identify some systematic disagreement that becomes larger for the longer chains. We made a comparison of the transient shear stress maximum from our simulations, two nonlinear models and experiments on a wide range of melts and solutions, including polystyrene (PS), polybutadiene, and styrene–butadiene rubber. This comparison establishes that the PS melt data show markedly different behavior to all other melts and solutions and KG simulations reproduce the PS data more closely than either the GLaMM or Xie and Schweizer models. We discuss the performance of these models against the data and simulations. Finally, by imposing a rapid reversing flow, we produce a method to extract the recoverable strain from MD simulations, valid for sufficiently entangled monodisperse polymers. We explore how the resulting data can probe the melt state just before the reversing flow. © 2019 The Authors. Journal of Polymer Science Part B: Polymer Physics published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1692–1704 相似文献
418.
Nessreen S. Abdelhamid Maimana A. Magdy Basma H. Anwar Nehal F. Farid 《Biomedical chromatography : BMC》2022,36(5):e5343
Recently, prednisolone has been used in treating many medical conditions, such as autoimmune diseases and cancer. It is also prescribed to mitigate the respiratory complications caused by COVID-19 infection. It can cause some health complications, such as GIT ulcers, so it should be co-administered with proton-pump inhibitors, such as esomeprazole, to prevent the risk of ulcers. This work aims to develop an ecofriendly and sensitive TLC method for simultaneous determination of esomeprazole and prednisolone in their binary mixtures and spiked human plasma. Separation was performed using a mixture of ethyl acetate, methanol, and ammonia (9.5:0.5:0.1, v/v/v) as an eluting system with UV scanning at 245 nm. Dapoxetine was used as an internal standard to correct the variation during sampling. The resulting Rf values for plasma, esomeprazole, prednisolone, and dapoxetine were 0.03, 0.51, 0.72 and 0.85, respectively. Four greenness assessment tools—national environmental method index, eco-scale assessments, analytical greenness metric approach (AGREE), and green analytical procedure index (GAPI)—were used to evaluate the greenness characteristics of the proposed method to the environment, and the results were acceptable and satisfactory. Validation parameters were checked according to the US FDA guidelines to achieve the international requirements for bioanalytical method validation, and the results were within the accepted ranges. 相似文献
419.
新疆北部干旱地区鼠类群落空间结构差异的比较研究 总被引:1,自引:0,他引:1
本文我们根据前人的研究并结合自己的调查,对新疆北部干旱地区鼠类群落空间结构差异进行了比较分析.结果表明,准噶尔盆地不同地区鼠类群落可划分为:高山草甸型、山地草原型、原生荒漠型、农田林地型和城市型等.一般高山草甸型以根田鼠为主;山地草原型以草原兔尾鼠、小林姬鼠、灰仓鼠为主;原生荒漠大沙鼠、子午沙鼠为主,梭梭荒漠型以大沙鼠,子午沙鼠为主,柽柳荒漠型以红尾沙鼠为主,跞石荒漠型以五趾跳鼠为主,荒漠草原型以五趾跳鼠、根田鼠为主,农田林地型以根田鼠、小家鼠、小林姬鼠、灰仓鼠为主;城市型以褐家鼠、小家鼠、灰仓鼠为主.同时发现,由于人类开垦经营,当地鼠类群落出现了由原始类型向人工环境的演变.褐家鼠是外来种,它已在不少地区占优势地位,成为当地主要的害鼠. 相似文献
420.