全文获取类型
收费全文 | 1648篇 |
免费 | 45篇 |
国内免费 | 13篇 |
专业分类
化学 | 1205篇 |
晶体学 | 7篇 |
力学 | 29篇 |
数学 | 269篇 |
物理学 | 196篇 |
出版年
2021年 | 15篇 |
2020年 | 21篇 |
2019年 | 8篇 |
2018年 | 16篇 |
2017年 | 23篇 |
2016年 | 29篇 |
2015年 | 35篇 |
2014年 | 33篇 |
2013年 | 59篇 |
2012年 | 96篇 |
2011年 | 118篇 |
2010年 | 47篇 |
2009年 | 39篇 |
2008年 | 101篇 |
2007年 | 82篇 |
2006年 | 98篇 |
2005年 | 104篇 |
2004年 | 84篇 |
2003年 | 73篇 |
2002年 | 71篇 |
2001年 | 16篇 |
2000年 | 17篇 |
1999年 | 25篇 |
1998年 | 26篇 |
1997年 | 18篇 |
1996年 | 24篇 |
1995年 | 19篇 |
1994年 | 26篇 |
1993年 | 21篇 |
1992年 | 14篇 |
1991年 | 12篇 |
1990年 | 13篇 |
1989年 | 11篇 |
1988年 | 12篇 |
1987年 | 12篇 |
1986年 | 10篇 |
1985年 | 24篇 |
1984年 | 24篇 |
1983年 | 15篇 |
1982年 | 19篇 |
1981年 | 28篇 |
1980年 | 21篇 |
1979年 | 24篇 |
1978年 | 13篇 |
1977年 | 14篇 |
1976年 | 19篇 |
1975年 | 13篇 |
1974年 | 8篇 |
1973年 | 7篇 |
1971年 | 6篇 |
排序方式: 共有1706条查询结果,搜索用时 0 毫秒
241.
Phenyl sulphenyl chloride is a γ-selective electrophile in its reaction with O-silylated dienolates. 相似文献
242.
Jon Aaronson 《Israel Journal of Mathematics》1981,38(3):182-188
We generalise W. Feller’s limit theorem for (independent) random variables with infinite moments. 相似文献
243.
Stepan Boitsov Jon Songstad Karl W. Trnroos 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(8):o528-o532
The molecular structures of the three title nitro‐substituted phenylacetonitriles, C8H6N2O2, at 123 K show that the molecules are linked together very differently. In the 2‐ and 4‐nitro compounds, there are both O?H and Ncyano?H interactions, whereas the crystal lattice of the 3‐nitro compound is essentially built up by O?H interactions. The O atoms seem to prefer the aromatic H atoms, while the cyano N atoms prefer the methylene H atoms. The phenyl–nitro torsion angles are ?19.83 (13), ?5.69 (12) and ?2.88 (12)°, while the phenyl–cyanomethyl torsion angles are ?62.27 (12), ?147.99 (9) and ?16.75 (14)° in the 2‐, 3‐ and 4‐NO2‐substituted compounds, respectively. 相似文献
244.
245.
246.
Jon R. Appel Jaime Buencamino Richard A. Houghten Clemencia Pinilla 《Molecular diversity》1996,2(1-2):29-34
Summary Extensive mapping studies for seven antigen-antibody interactions have been carried out using both individual analogs and peptide libraries. With competitive ELISA, these studies have revealed that monoclonal antibodies exhibit a broad range of specificities, from antibodies that recognize only conservative substitutions for 1–2 positions of the antigenic determinant, to antibodies that recognize sequences that are completely unrelated to the parent antigen with comparable affinities. Synthetic combinatorial libraries, containing millions of peptide sequences, permit a more systematic and rapid evaluation of the extent of multiple-binding specificities of monoclonal antibodies than individual analogs. The peptide libraries used here comprise mixtures of compounds having specifically defined positions and mixture positions. The same diversity of sequences in different formats, which differ by the numbers of positions singularly defined and different locations defined within the sequence, can be examined. Comparison of the screening results, selection criteria of the most active mixtures, and different approaches used for the deconvolution of active individual compounds are discussed. Synthetic combinatorial libraries greatly facilitate the understanding of antigen-antibody interactions at the amino acid level and will assist in the development of improved immunodiagnostics. 相似文献
247.
We compute the cross section for pp → ppπ+π? in the kinematical region for which two-pomeron exchange is important, assuming dominance of the pion-exchange pole. We include effects due to absorption, final-state interaction, and interference between the two contributing Feynman diagrams. These effects have been ignored in previous calculations. Consequently, our predicted cross section is smaller than previous predictions by a factor of ~ 3, and is consistent with experimental indications. We calculate the background cross section in the double pomeron exchange region, and find that it is sizable even at s ~ 3000 GeV2. We discuss the two-particle inclusive process pp → ppX. 相似文献
248.
Jon Barwise 《Israel Journal of Mathematics》1976,25(1-2):47-63
We show how to approximate a Henkin formula by first order formulas. This method of approximation is then applied to problems
of axiomatizing classes of structures.
Dedicated to the memory of Abraham Robinson.
The author is an Alfred P. Sloan Fellow. 相似文献
249.
250.
Carnitine and its O-acyl derivatives undergo two major pyrolytic reactions in the mass spectrometer. Firstly elimination of water from carnitine or acid from acylcarnitine takes place followed by intramolecular displacement and formation of crotonyl lactone and trimethylamine. Secondly intramolecular displacement occurs with formation of a substituted γ-lactone and trimethylamine. For the lower acid derivatives only the elimination pathway is important. For carnitine and higher derivatives both processes are important. The electron induced fragmentations of the major pyrolysis products are relatively simple. The most important pathways for the major components are discussed. The pyrolytic composition and mode of fragmentation are characteristic and can be used for identification purposes. 相似文献