全文获取类型
收费全文 | 5628篇 |
免费 | 156篇 |
国内免费 | 35篇 |
专业分类
化学 | 4030篇 |
晶体学 | 61篇 |
力学 | 154篇 |
数学 | 713篇 |
物理学 | 861篇 |
出版年
2022年 | 33篇 |
2021年 | 51篇 |
2020年 | 63篇 |
2019年 | 65篇 |
2018年 | 46篇 |
2017年 | 46篇 |
2016年 | 125篇 |
2015年 | 88篇 |
2014年 | 115篇 |
2013年 | 250篇 |
2012年 | 309篇 |
2011年 | 355篇 |
2010年 | 208篇 |
2009年 | 158篇 |
2008年 | 311篇 |
2007年 | 332篇 |
2006年 | 357篇 |
2005年 | 301篇 |
2004年 | 265篇 |
2003年 | 252篇 |
2002年 | 239篇 |
2001年 | 78篇 |
2000年 | 66篇 |
1999年 | 42篇 |
1998年 | 54篇 |
1997年 | 63篇 |
1996年 | 90篇 |
1995年 | 51篇 |
1994年 | 50篇 |
1993年 | 58篇 |
1992年 | 36篇 |
1991年 | 48篇 |
1990年 | 52篇 |
1989年 | 41篇 |
1988年 | 50篇 |
1987年 | 33篇 |
1986年 | 36篇 |
1985年 | 79篇 |
1984年 | 79篇 |
1983年 | 40篇 |
1982年 | 86篇 |
1981年 | 73篇 |
1980年 | 71篇 |
1979年 | 58篇 |
1978年 | 61篇 |
1977年 | 51篇 |
1976年 | 48篇 |
1975年 | 43篇 |
1974年 | 42篇 |
1973年 | 48篇 |
排序方式: 共有5819条查询结果,搜索用时 15 毫秒
981.
Mark Niemeyer Philip P. Power 《Angewandte Chemie (International ed. in English)》1998,37(9):1277-1279
A “one-legged thallium” is observed in the arylthallium(I ) compound 2,6-Trip2C6H3Tl (Trip=2,4,6-iPr3C6H2), which was synthesized from the corresponding organolithium compound and thallium chloride. X-ray structure analysis reveals that 2,6-Trip2C6H3Tl is monomeric in the solid state and contains a singly coordinated thallium atom (see space-filling model on the right). 相似文献
982.
983.
Jane S. Murray Fakher Abu-Awwad Peter Politzer Leslie C. Wilson Allan S. Troupin Ryan E. Wall 《International journal of quantum chemistry》1998,70(6):1137-1143
The computed molecular surface electrostatic potentials of a group of anticonvulsants of various chemical types were investigated with the objective of identifying common features that may be related to their activities. The calculations were carried out with the density functional B3P86/6-31G* procedure, using HF/STO-3G*-optimized geometries. Analysis of several statistically based properties of the surface potentials indicates that the negative regions are of primary importance and that an optimum intermediate level of local polarity, or internal charge separation, is required. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 70: 1137–1143, 1998 相似文献
984.
985.
Philip J. Cox Marcel Jaspars Yashodharan Kumarasamy Lutfun Nahar Satyajit D. Sarker Mohammad Shoeb 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(9):o520-o522
The crystal structure of 9‐(3‐methylbut‐2‐enyloxy)‐7H‐furo[3,2‐g]chromen‐7‐one–4‐methoxy‐9‐(3‐methylbut‐2‐enyloxy)‐7H‐furo[3,2‐g]chromen‐7‐one (0.926/0.074), 0.926C16H14O4·0.074C17H16O5, is characterized by two independent imperatorin molecules in the asymmetric unit, which exhibit different side‐chain conformations. A small amount of phellopterin overlaps with one of the two imperatorin molecules. The supramolecular structure is supported by C—H...O, C—H...π and π–π interactions. 相似文献
986.
Philip J. Cox 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(9):o533-o536
The crystal structures of the title compounds (both C7H7ClO) are characterized by two independent molecules in each of the asymmetric units and feature O—H...O, C—H...π and π–π interactions. In addition, intermolecular C—H...Cl and intramolecular O—H...Cl interactions are present in 2‐chloro‐5‐methylphenol. For each crystal, the non‐covalent interactions emphasize the different spatial environments for the two independent molecules. 相似文献
987.
Philip J. Cox Stephen M. MacManus 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(10):o603-o604
Molecules of the title compound, C13H9ClO2, contain an intramolecular O—H...O hydrogen bond, and the two aromatic rings are inclined at 57.02 (3)° with respect to one another. The crystal structure is supported by C—H...O, C—H...π and π–π interactions. 相似文献
988.
Philip A. W. Dean Donald C. Craig Marcia L. Scudder Ian G. Dance 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(11):m484-m486
The reported crystal structures of Ph4P+·I− and Ph4As+·I− have been re‐examined. An apparent instance of substitutional dimorphism could not be reproduced and, contrary to an earlier report, tetraphenylarsonium iodide, [As(C6H5)4]I or Ph4As+·I−, was found to be isostructural with the phosphorus compound. The cation and anion are both located on symmetry sites. The crystal packing involves linear chains of cations in fourfold phenyl embraces. 相似文献
989.
990.