全文获取类型
收费全文 | 50961篇 |
免费 | 7993篇 |
国内免费 | 6423篇 |
专业分类
化学 | 37296篇 |
晶体学 | 641篇 |
力学 | 2954篇 |
综合类 | 427篇 |
数学 | 5853篇 |
物理学 | 18206篇 |
出版年
2024年 | 115篇 |
2023年 | 1010篇 |
2022年 | 1554篇 |
2021年 | 1854篇 |
2020年 | 2064篇 |
2019年 | 2007篇 |
2018年 | 1719篇 |
2017年 | 1615篇 |
2016年 | 2262篇 |
2015年 | 2274篇 |
2014年 | 2817篇 |
2013年 | 3602篇 |
2012年 | 4405篇 |
2011年 | 4496篇 |
2010年 | 3189篇 |
2009年 | 2973篇 |
2008年 | 3230篇 |
2007年 | 2778篇 |
2006年 | 2664篇 |
2005年 | 2316篇 |
2004年 | 1953篇 |
2003年 | 1562篇 |
2002年 | 1523篇 |
2001年 | 1321篇 |
2000年 | 1086篇 |
1999年 | 1145篇 |
1998年 | 912篇 |
1997年 | 769篇 |
1996年 | 913篇 |
1995年 | 746篇 |
1994年 | 681篇 |
1993年 | 576篇 |
1992年 | 532篇 |
1991年 | 460篇 |
1990年 | 391篇 |
1989年 | 280篇 |
1988年 | 249篇 |
1987年 | 227篇 |
1986年 | 169篇 |
1985年 | 186篇 |
1984年 | 145篇 |
1983年 | 131篇 |
1982年 | 86篇 |
1981年 | 65篇 |
1980年 | 54篇 |
1979年 | 36篇 |
1978年 | 26篇 |
1976年 | 27篇 |
1975年 | 31篇 |
1974年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
142.
A simple model has been developed to describe the Zeeman patterns of far-infrared laser magnetic resonance spectra of the monobromomethyl radical CH2Br observed at 447.3 and 671.1μm. A satisfactory agreement between the experimental spectra of the radical and their simulation with this simple model has been achieved. This approach can be used to gain further information about the structure and the spectrum of this interesting radical. 相似文献
143.
144.
Several α-ketoalcohols of synthetic value were resolved using lipase as a catalyst. Lipoprotein lipase (LPL) provided the best rate of hydrolysis and kinetic differentiation. One of these optically pure α-ketoalcohol was converted to (5)-ibuprofen in good optical purity. The stereospecific inversion of (R)-alcohol to (S)-alcohol is described. 相似文献
146.
[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
147.
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
148.
用裂解气相色谱-质谱联用方法研究了橡胶产品中使用的增塑剂邻苯二甲酸二甲酯(DMP)在不同温度条件下的热裂解行为.对不同温度条件下裂解产物的分析表明,在初始阶段DMP的裂解产物主要为二氧化碳、苯、甲苯和苯甲酸甲酯.随着温度的升高苯甲酸甲酯进一步裂解成为分子质量更小的自由基,并发生稠环化反应形成更稳定的菲、蒽、间-联三苯、三亚苯等芳香族多环化合物.根据分析实验提供的裂解产物信息和有机物热裂解化学反应的原理对DMP的热裂解反应机理作了探讨,表明在废旧合成橡胶热裂解回收过程中,增塑剂DMP的高温裂解会产生多环芳烃污染物.应选择合适裂解工艺和裂解温度,以减少对环境的污染. 相似文献
149.
Observation of spontaneous pattern with six-fold symmetry in disk-shaped ZnO complex microstructures
L.W. Yang Y.J. Gao X.L. Wu Y.M. Yang G.S. Huang Z.Y. Zhang P.K. Chu 《Applied Physics A: Materials Science & Processing》2007,89(1):173-176
Using a simple vapor phase transport technique, we have fabricated unique complex disk-shaped ZnO microstructures comprising
a small disk coaxially grown on a large one and observed spatially perfect six-fold symmetric patterns. The observed results
can be explained based on the spontaneous nanoindentation (NI) effect under the geometric constraints and the explanation
can be extended to fathom the growth mechanism of other highly symmetrical ZnO nanostructures. Our results indicate that NI
not only can elucidate the mechanical properties of surfaces and thin films but also is an effective approach to fabricate
ordered nanostructures with high precision on the location of the building blocks.
PACS 81.16.Rf; 81.07.-b; 81.05.Dz 相似文献
150.
A fluoroionophore sensor, N-[4-(1-pyrene)butyroyl]-L-tryptophan (PLT), has been reported. It can distinguish lead ion from other 12 metal ions via forming a pyrene dimer and it exhibits a very high sensitivity (0.15 microM) in aqueous solution (Chem. Commun., 2006, 2702). When the indole moiety in PLT was changed to benzene, in forming a new fluoroionophore of N-[4-(1-pyrene)butyroyl]-L-phenylalanine (PLP), it could not form a pyrene dimer in response to Pb(2+) in water. The present study describes the spectroscopic clarification of the intrinsic differences of the binding model between PLP and PLT in binding with Pb(2+). The model shows identical chelating bidentate coordination between COO(-) and Pb(2+) both in PLP-Pb and PLT-Pb; however, there is no indication of the interaction between the phenyl ring and the metal ion or the hydrogen bonding between amide groups in PLP-Pb. These differences in the binding model between PLP-Pb and PLT-Pb illustrate that the indole ring in PLT appears to play a crucial role in the high selectivity and sensitivity of PLT to lead(II) ion. 相似文献