全文获取类型
收费全文 | 2284篇 |
免费 | 76篇 |
国内免费 | 3篇 |
专业分类
化学 | 1567篇 |
晶体学 | 15篇 |
力学 | 27篇 |
数学 | 233篇 |
物理学 | 521篇 |
出版年
2022年 | 28篇 |
2021年 | 41篇 |
2020年 | 35篇 |
2019年 | 36篇 |
2018年 | 18篇 |
2017年 | 26篇 |
2016年 | 46篇 |
2015年 | 64篇 |
2014年 | 63篇 |
2013年 | 78篇 |
2012年 | 96篇 |
2011年 | 94篇 |
2010年 | 86篇 |
2009年 | 51篇 |
2008年 | 94篇 |
2007年 | 83篇 |
2006年 | 85篇 |
2005年 | 77篇 |
2004年 | 103篇 |
2003年 | 83篇 |
2002年 | 78篇 |
2001年 | 68篇 |
2000年 | 53篇 |
1999年 | 33篇 |
1998年 | 37篇 |
1997年 | 31篇 |
1996年 | 32篇 |
1995年 | 29篇 |
1994年 | 34篇 |
1993年 | 43篇 |
1992年 | 37篇 |
1991年 | 23篇 |
1990年 | 18篇 |
1989年 | 20篇 |
1988年 | 23篇 |
1987年 | 33篇 |
1986年 | 25篇 |
1985年 | 28篇 |
1984年 | 20篇 |
1983年 | 22篇 |
1982年 | 26篇 |
1981年 | 21篇 |
1978年 | 25篇 |
1977年 | 21篇 |
1976年 | 18篇 |
1975年 | 20篇 |
1974年 | 22篇 |
1973年 | 17篇 |
1972年 | 17篇 |
1970年 | 15篇 |
排序方式: 共有2363条查询结果,搜索用时 225 毫秒
41.
Frkanec L Jokić M Makarević J Wolsperger K Zinić M 《Journal of the American Chemical Society》2002,124(33):9716-9717
The photoinduced gelation system based on 1 (non-gelling) to 2 (gelling) molecular photoisomerization in water results by microspheres (1) to gel fibers (2) transformation at the supramolecular level. 相似文献
42.
This paper reports on studies on the reaction of InCl with SnCl2 to form ternary halides. The reaction route is investigated by x‐ray investigations at different temperatures. Depending on the modification of InCl as educt and on the temperature conditions the reaction follows different pathways which may include intermediate redox reactions of the type In+ + Sn2+ → In3+ + Sn0. 相似文献
43.
A series of enantiomerically pure 8-oxabicyclo[3.2.1]oct-6-en-3-ones functionalized in the unsaturated two-carbon bridge has been prepared by the title reaction. Carbocation reactivity has been fined-tuned at -95 degrees C and adjusted to diene nucleophilicity. Conventional electrophilic substitution of 3-silylated and 3-stannylated furan is suppressed in favor of the rapid 4 + 3 cycloaddition mode. In the case of cycloadduct 13A, stereoselectivity (17:1) is perfectly matched to regioselectivity (17:1). High stereoselection as well as unprecedented regioselection and chemoselection is attributed to the low-temperature cycloaddition protocol and the design of chiral auxiliary and tether. 相似文献
44.
45.
Pentacarbonyl-rhenate and -manganate react with the cationic complexes [cpMo(CO)2(diene)]+, [cpMo(CO)2(cyclopentadiene]+, [cpMo(CO)2(cyclohexadiene)]+, [cpMo(CO)2(trimethylenemethane]+, [(OC)3Mo(η7-C7H7)]+, [cp(OC)-(Ph3P)Mo(alkyne)]+ to give the corresponding heteronuclear hydrocarbon-bridged complexes. 相似文献
46.
Transition Metal Complexes with Anions of 1-substituted Tetrazolinones and -thiones and of 1,3-Thiazolin-2-thione The preparation of a series of anionic and phosphine containing complexes with the ambivalent anions of 1-R-tetrazolin-5-ones and -5-thiones, and of 1,3-thiazolin-2-thione is reported. According to the i.r. and 1H n.m.r. spectra the S-heterocycles are bonded through the exocyclic sulfur atom to the metal; in the oxotetrazolinate compounds coordination occurs via the N2 or N4 ring atoms. The copper and silver complexes [(Ph3P)MX]2 (X = anionic heterocycle) have been found to be dimeric. 相似文献
47.
The cover picture shows a model of the "progenitor-TADDOLs" in front of a panorama of the Fünffingersstocks and the Wenden Glacier in the Titlisgebiet (Switzerland). The model is flanked by a stylized view of the general mechanistic model for the preferred stereochemical pathway of the Ti-TADDOLate-catalyzed reaction of chelating substrates (left) and a blackboard (right) showing formulae of compounds that can be prepared with high enantioselectivity by nucleophilic addition in the presence of titanium TADDOLates. From TADDOL, introduced in 1982, a genuine auxiliary system for the "introduction of chirality" (not only by reaction) has been developed, which, in the final sprint against the competition has a good chance of securing a place on the winning podium. The photograph of the mountain landscape was taken by Dr. J. Frackenpohl, the cover picture was generated by one of the authors (A.H.) of the comprehensive review of TADDOLs in this issue (p. 92 ff.) with the help of the program Povray. Supporting information for this article is available on the WWW under http://www.angewandte.com or from the author. 相似文献
48.
Urathamakul T Beck JL Sheil MM Aldrich-Wright JR Ralph SF 《Dalton transactions (Cambridge, England : 2003)》2004,(17):2683-2690
Electrospray ionisation mass spectrometry was used to investigate reactions between six ruthenium compounds and three different non self-complementary duplex oligonucleotides containing 16 base pairs. Each of the compounds studied formed non-covalent complexes containing between one and five ruthenium molecules bound to DNA. Competition experiments involving duplex 16mers and pairs of ruthenium compounds were used to determine the order of relative binding affinities of the metal compounds. Other competition experiments involving ruthenium compounds, and the organic DNA binding agents daunomycin and distamycin, provided information about the sites and modes of DNA binding of the ruthenium compounds. 相似文献
49.
Journal of Optimization Theory and Applications - Coordinate descent algorithms are popular in machine learning and large-scale data analysis problems due to their low computational cost iterative... 相似文献
50.