全文获取类型
收费全文 | 29629篇 |
免费 | 4572篇 |
国内免费 | 4520篇 |
专业分类
化学 | 23158篇 |
晶体学 | 528篇 |
力学 | 1590篇 |
综合类 | 330篇 |
数学 | 2851篇 |
物理学 | 10264篇 |
出版年
2024年 | 89篇 |
2023年 | 543篇 |
2022年 | 1036篇 |
2021年 | 1115篇 |
2020年 | 1181篇 |
2019年 | 1239篇 |
2018年 | 1013篇 |
2017年 | 1013篇 |
2016年 | 1411篇 |
2015年 | 1423篇 |
2014年 | 1711篇 |
2013年 | 2234篇 |
2012年 | 2580篇 |
2011年 | 2624篇 |
2010年 | 1991篇 |
2009年 | 1759篇 |
2008年 | 1935篇 |
2007年 | 1625篇 |
2006年 | 1636篇 |
2005年 | 1530篇 |
2004年 | 1258篇 |
2003年 | 1086篇 |
2002年 | 1187篇 |
2001年 | 918篇 |
2000年 | 728篇 |
1999年 | 615篇 |
1998年 | 435篇 |
1997年 | 352篇 |
1996年 | 372篇 |
1995年 | 321篇 |
1994年 | 282篇 |
1993年 | 257篇 |
1992年 | 220篇 |
1991年 | 205篇 |
1990年 | 163篇 |
1989年 | 130篇 |
1988年 | 107篇 |
1987年 | 73篇 |
1986年 | 80篇 |
1985年 | 78篇 |
1984年 | 40篇 |
1983年 | 39篇 |
1982年 | 22篇 |
1981年 | 21篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1971年 | 3篇 |
1959年 | 3篇 |
1957年 | 7篇 |
1936年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
YAN Xiaomin ZHAO Lin SHAO Jianhui TAN Xin SONG Zhengxiao School of Chemical Engineering Technology Tianjin University Tianjin China Slichem Liquid Material Co. Ltd. Shijiazhuang China 《Chinese Journal of Reactive Polymers》2004,(Z1)
1. INTRODUCTION Methionine, namely 2-amido-4-thiomethyl butyric acid with a structure of CH3SCH2CH2CHCOOH, is one of the essential amino acids and has two natural enantionmers, D and L-methionine. The mixture of L- and D-isomers can be used as analeptics or nutritive additives to maintain the equilibrium of amino acids of feed [1,2]. L-methionine can release active methyl and accelerate the synthesis of choline, which further speeds up the conversion of the lipid accumulated in liv… 相似文献
12.
Baker‘s yeast mediated reduction of optically active diketone is described. The two keto groups are efficiently differentiated and the ee value of the recovered material is considerably raised. It affords highly optically active key intermediates efficiently for the synthesis of natural polyhydroxylated agarofuran products. 相似文献
13.
14.
16.
[1]M.Alford,K.Rajagopal,and F.Wilczek,Phys.Lett.B 422 (1998) 247; Nucl.Phys.B 537 (1999) 443.
[2]M.Gyulassy and L.McLerran,arXiv:nucl-th/0405013;E.V.Shuryak,arXiv:hep-ph/0405066.
[3]K.Rajagopal and F.Wilczek,hep-ph/0011333.
[4]M.Alford,Chris Kouvaris,and K.Rajagopal,hepph/0406137.
[5]Y.Nambu and G.Jona-Lasinio,Phys.Rev.122 (1961)345.
[6]R.T.Cahill and C.D.Roberts,Phys.Rev.D 32 (1985)2419.
[7]R.T.Cahill and Susan M.Ganner,hep-ph/9812491.
[8]A.W.Steiner,S.Reddy,and M.Prakash,Phys.Rev.D 66 (2002) 094007.
[9]P.Amore,M.C.Birse,J.A.McGovern,and N.R.Walet,Phys.Rev.D 65 (2002) 074005.
[10]M.Alford and K.Rajagopal,JHEP 0206 (2002) 031.
[11]Xiao-Fu Li,Yu-Xin Liu,Hong-Shi Zong,and En-GuangZhao,Phys.Rev.C 58 (1998) 1195.
[12]H.Reinhardt,Phys.Lett.B 244 (1990) 2.
[13]Steven Weinberg,The Quantum Theory of Fields,Vol.2,Cambridge University Press,Cambridge (1996) p.348. 相似文献
17.
Based on the effective-field theory with self-spin correlations and the differential operator technique,physical properties of the spin-2 system with biaxial crystal field on the simple cubic, body-centered cubic, as well as faced-centered lattice have been studied. The influences of the external longitudinal magnetic field on the magnetization,internal energy, specific heat, and susceptibility have been discussed in detail. The phenomenon that the magnetization in the ground state shows quantum effects produced by the biaxial transverse crystal field has been found. 相似文献
18.
Sang Kyu Lee Min Ju Cho Jung‐Il Jin Dong Hoon Choi 《Journal of polymer science. Part A, Polymer chemistry》2007,45(3):531-542
New photocrosslinkable maleimide copolymers have been synthesized by the attachment of a tricyanopyrrolidene‐based chromophore. The 2‐(3‐cyano‐4‐(2‐{4‐[hexyl‐(6‐hydroxy‐hexyl)‐amino]‐phenyl}‐vinyl)‐5‐oxo‐1‐{4‐[4‐(3‐oxo‐3‐phenyl‐propenyl)‐ phenoxy]‐butyl}‐1,5‐dihydro‐pyrrol‐2‐ylidene)‐malononitrile chromophore exhibits nonlinear optical activity and contains a chalcone moiety that is sensitive to UV light (λ = 330–360 nm) for crosslink formation. The maleimide monomers have also been functionalized with chalcone moieties. The resultant copolymers exhibit great processability, and one of them shows a maximum electrooptic coefficient of 90 pm/V at 1300 nm. We could control the thermal stability of the electrooptic coefficient with the newly synthesized photoreactive copolymers successfully. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 531–542, 2007 相似文献
19.
Tao Jin Feng-Xian Jiang Xiao-Li Li Fang Wang Xiao-Hua Shen Rui-Qiang Zhang Hai-Shun Wu 《Applied Surface Science》2006,253(5):2708-2712
CoPt/Ag and [C/CoPt]n/Ag thin films have been prepared onto the glass substrates by magnetron sputtering. We investigated the evolution of texture and magnetic properties of CoPt/Ag and [C/CoPt]n/Ag films. The results show that C-doping plays an important role in improving (0 0 1) texture, improving the order parameter S, reducing the intergrain interactions, and making the magnetization reversal mechanism more close to Stoner-Wolfarth rotational mechanism. The growth mechanism of (0 0 1) texture also seems to be related strongly to the films thickness. Our results show that the highly (0 0 1)-oriented films with ordered fct phase have a significant potential for the perpendicular media of extremely high-density recording. 相似文献
20.