全文获取类型
收费全文 | 7811篇 |
免费 | 179篇 |
国内免费 | 44篇 |
专业分类
化学 | 5096篇 |
晶体学 | 142篇 |
力学 | 169篇 |
数学 | 1187篇 |
物理学 | 1440篇 |
出版年
2022年 | 44篇 |
2021年 | 54篇 |
2020年 | 56篇 |
2019年 | 88篇 |
2018年 | 63篇 |
2017年 | 59篇 |
2016年 | 153篇 |
2015年 | 154篇 |
2014年 | 145篇 |
2013年 | 371篇 |
2012年 | 336篇 |
2011年 | 403篇 |
2010年 | 187篇 |
2009年 | 198篇 |
2008年 | 361篇 |
2007年 | 392篇 |
2006年 | 326篇 |
2005年 | 363篇 |
2004年 | 325篇 |
2003年 | 315篇 |
2002年 | 305篇 |
2001年 | 142篇 |
2000年 | 126篇 |
1999年 | 118篇 |
1998年 | 91篇 |
1997年 | 121篇 |
1996年 | 131篇 |
1995年 | 122篇 |
1994年 | 123篇 |
1993年 | 95篇 |
1992年 | 78篇 |
1991年 | 94篇 |
1990年 | 85篇 |
1989年 | 80篇 |
1988年 | 113篇 |
1987年 | 100篇 |
1986年 | 69篇 |
1985年 | 119篇 |
1984年 | 128篇 |
1983年 | 97篇 |
1982年 | 114篇 |
1981年 | 135篇 |
1980年 | 121篇 |
1979年 | 103篇 |
1978年 | 101篇 |
1977年 | 87篇 |
1976年 | 88篇 |
1975年 | 82篇 |
1974年 | 66篇 |
1973年 | 55篇 |
排序方式: 共有8034条查询结果,搜索用时 15 毫秒
101.
K. Nomura H. Reuther E. Richter Y. Ujihira 《Journal of Radioanalytical and Nuclear Chemistry》1995,190(2):299-313
Changes in the magnetic structure of Fe–Si–Al films due to Al and N ion implantation were studied by57Fe Conversion Electron Mössbauer Spectrometry (CEMS). The peaks of the magnetic sextets due to the crystalline films became broader by implantation with 5×1016 Al/cm2, suggesting the formation of amorphous phases. In the CEM spectrum of one sample with large grains implanted with 1×1017 Al/cm2 a crystalline -Fe phase appeared. N implantation with the same dose did not amorphize the sample but the components with high magnetic hyperfine fields were enhanced. 相似文献
102.
Katritzky AR Xu YJ Vakulenko AV Wilcox AL Bley KR 《The Journal of organic chemistry》2003,68(23):9100-9104
Molecules were prepared with substituted nitrobenzyl groups covalently bonded to N-(4-hydroxy-3-methoxybenzyl)acetamide (2) by ether or carbonate linkages. These compounds decomposed under irradiation at 363 nm. Those with carbonate linkages decomposed at slower rates than those with ether linkages. Molecules with dimethoxy-substituted benzyl groups decomposed more slowly than monomethoxy-substituted benzyl groups due to the electronic characteristics of the benzylic carbon. 相似文献
103.
N-(α-Benzotriazolylalkyl)arylacetamides, readily available from an arylacetamide, an aldehyde and benzotriazole, undergo intramolecular cyclization under acidic conditions to give 1-aryl-1,4-dihydro-3(2H)-isoquinolinones in good to excellent yields. Similarly, 2-(benzotriazol-1-yl)-2-(o-hydroxyphenyl)ethanols, obtained by lithiation of 2-(benzotriazol-1-ylmethyl)phenols followed by quenching with aldehydes or ketones, eliminate a molecule of water and a molecule of benzotriazole yielding 2-substituted and 2,3-disubstituted benzofurans. 相似文献
104.
Cadmium salts give an intense cadmium atomic emission in the MECA cavity in a hydrogen-nitrogen-air flame. When a carbon or stainless steel cavity is used, 10–120 ng of cadmium in 5-μl samples can be determined. In the presence of sulphuric acid, anionic interferences are removed. Of the cations, only Fe(III), Cr(III), Mg and Sn(II) interfere seriously. 相似文献
105.
106.
107.
We make a high-precision Monte Carlo study of two- and three-dimensional self-avoiding walks (SAWs) of length up to 80,000 steps, using the pivot algorithm and the Karp-Luby algorithm. We study the critical exponentsv and 2
4 – as well as several universal amplitude ratios; in particular, we make an extremely sensitive test of the hyperscaling relationdv = 2
4 –. In two dimensions, we confirm the predicted exponentv=3/4 and the hyperscaling relation; we estimate the universal ratios <R
g
2
>/<R
e
2
>=0.14026±0.00007, <R
m
2
>/<R
e
2
>=0.43961±0.00034, and *=0.66296±0.00043 (68% confidence limits). In three dimensions, we estimatev=0.5877±0.0006 with a correctionto-scaling exponent
1=0.56±0.03 (subjective 68% confidence limits). This value forv agrees excellently with the field-theoretic renormalization-group prediction, but there is some discrepancy for
1. Earlier Monte Carlo estimates ofv, which were 0.592, are now seen to be biased by corrections to scaling. We estimate the universal ratios <R
g
2
>/<R
e
2
>=0.1599±0.0002 and *=0.2471±0.0003; since *>0, hyperscaling holds. The approach to * is from above, contrary to the prediction of the two-parameter renormalization-group theory. We critically reexamine this theory, and explain where the error lies. In an appendix, we prove rigorously (modulo some standard scaling assumptions) the hyperscaling relationdv = 2
4 – for two-dimensional SAWs. 相似文献
108.
109.
110.