全文获取类型
收费全文 | 6495篇 |
免费 | 1368篇 |
国内免费 | 2063篇 |
专业分类
化学 | 3195篇 |
晶体学 | 107篇 |
力学 | 779篇 |
综合类 | 171篇 |
数学 | 2612篇 |
物理学 | 3062篇 |
出版年
2024年 | 64篇 |
2023年 | 222篇 |
2022年 | 230篇 |
2021年 | 260篇 |
2020年 | 199篇 |
2019年 | 178篇 |
2018年 | 140篇 |
2017年 | 209篇 |
2016年 | 209篇 |
2015年 | 300篇 |
2014年 | 547篇 |
2013年 | 412篇 |
2012年 | 454篇 |
2011年 | 508篇 |
2010年 | 472篇 |
2009年 | 498篇 |
2008年 | 595篇 |
2007年 | 467篇 |
2006年 | 486篇 |
2005年 | 481篇 |
2004年 | 431篇 |
2003年 | 378篇 |
2002年 | 293篇 |
2001年 | 293篇 |
2000年 | 221篇 |
1999年 | 188篇 |
1998年 | 208篇 |
1997年 | 193篇 |
1996年 | 156篇 |
1995年 | 124篇 |
1994年 | 103篇 |
1993年 | 88篇 |
1992年 | 68篇 |
1991年 | 79篇 |
1990年 | 74篇 |
1989年 | 44篇 |
1988年 | 18篇 |
1987年 | 11篇 |
1986年 | 8篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1959年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有9926条查询结果,搜索用时 31 毫秒
971.
1841年,D elaunay获得如下定理:如果在一平面上沿定直线滚动一条二次圆锥直线,然后将其焦点的轨迹绕定直线旋转,则所得到的曲面具有常数平均曲率,反之,所有旋转常数平均曲率曲面(除球面外)都有如此构造.本文将以上的D elaunay定理推广到Lorentz-M inkow sk i空间Rn1 1中类空的Sm型旋转W超曲面. 相似文献
972.
以1,2,3,4-四氢异喹啉为原料,先依次与二碳酸二叔丁酯、亚氯酸钠反应得到N-Boc-1,2,3,4-四氢-1-异喹啉酮,再和芳基格氏试剂反应得到分子内不对称还原胺化反应的底物,最后以ax-Josiphos为手性配体,[Ir(COD)Cl]2为金属前体,在Ti(OiPr)4和40%HBr溶液组成的催化体系中合成了8个手性1-芳基四氢异喹啉类化合物,其结构经1H NMR和13C NMR表征。该路线提供了一种以廉价1,2,3,4-四氢异喹啉为原料高效合成手性1-芳基四氢异喹啉类衍生物的新方法,为索利那新等药物的合成提供了新路径。
相似文献
973.
报道了加州大学尔湾分校的管志斌教授,以及德国康茨坦茨大学Stefan Mecking教授课题组在中性不对称环番配位的烯烃聚合催化剂方面的研究进展。
相似文献
974.
It is shown that certain multi-component Ermakov systems admit Lewis-Ray-Reid invariants. This extends the result to the two-component Ermakov system. 相似文献
975.
Two types of Mei adiabatic invariants induced by perturbation of Mei symmetry for nonholonomic controllable mechanical systems are reported. Criterion and restriction equations determining Mei symmetry after being disturbed of the system are established. Form and existence condition of Mei adiabatic invariants are obtained. 相似文献
976.
In this paper, we calculate the branching ratios and the direct CP-violating asymmetries for decays B^0 → a0^0(980)π^0, a0^+ (980)π^-, a0^-(980)π^+ and B^- → a0^0 (980)π^-, a0^- (980)π^0 by employing the perturbative QCD (pQCD) factorization approach at the leading order. We found that (a) the pQCD predictions for the branching ratios are around (0.4-2.8) × 10^-6, consistent with currently available experimental upper limits; (b) the CP asymmetries of B^0→ a0^0(980)π^0 and B^- → a0^- (980)π^0 decays can be large, about (70-80)% for α= 100°. 相似文献
977.
B. Meadows 《中国物理 C》2010,34(6):780-787
Studies in which BABAR data have shown evidence for mixing in the neutral charm meson system are presented. A new measurement of the lifetime difference parameter ycp = (1.16±0.22±0.18)% is described. Results are also presented from a systematic study of DK and D*K invariant mass distributions from a 470 fb^-1 sample of asymmetric e^+e^- interactions recorded by the BABAR detector at the PEP-Ⅱ storage rings. A new charmed-strange meson has been observed with mass [3044 ± 8stat (-5^+30 )syst] MeV/c^2 and width [239± 35stat (-42^+46)syst]MeV/c^2. 相似文献
978.
Y. Miyachi 《中国物理 C》2010,34(9):1494-1497
The HERMES measured azimuthal amplitudes of cross sections and their transverse target single spin asymmetries for hadron productions in semi-inclusive deep inelastic scattering.From the extracted amplitudes,novel parton distribution functions can be studied.The recent results related to Sivers and Boer-Mulders distribution functions are discussed. 相似文献
979.
Generation of Broadband High Harmonics through Linear Mode Conversion in Inhomogeneous Plasmas
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The generation of high order harmonics from an inhomogeneous ovderdense plasma target irradiated by an ultrashort intense laser pulse is studied by numerical simulation. During such interaction, ultrafast electron bunches are generated and excite electron plasma oscillations as they pass through the overdense target. These plasma oscillations will emit high-frequency electromagnetic emission by linear mode conversion. Instead of the integer harmonies generation, the emission appears with a broadband and even continuous spectrum corresponding to the electron plasma frequency range of the inhomogeneous plasma density. 相似文献
980.
By using a semi-empirical Lennard-Jones embedded-atom-method potential, we study the influence of many-body forces and atomic size mismatch on the wetting behavior of nano droplets on a solid surface. With molecular dynamics simulations, we find that the contact angle decreases with increasing many-body forces. The increase of atomic size mismatch between solid and liquid results in the decrease of contact angles. Our calculation also shows that the interface structure is strongly affected by the interaction between liquid and solid as well as the atomic size mismatch. For weak solid-liquid interaction, the interface layer of the droplet nearest to the solid exhibits a typical simple liquid structure regardless of the size mismatch. For strong solid-liquid interaction, evident ordering in the interface layer is observed for well matched cases. 相似文献