全文获取类型
收费全文 | 131499篇 |
免费 | 23404篇 |
国内免费 | 14048篇 |
专业分类
化学 | 90921篇 |
晶体学 | 1444篇 |
力学 | 8370篇 |
综合类 | 804篇 |
数学 | 15475篇 |
物理学 | 51937篇 |
出版年
2024年 | 331篇 |
2023年 | 2715篇 |
2022年 | 3801篇 |
2021年 | 4613篇 |
2020年 | 5506篇 |
2019年 | 5144篇 |
2018年 | 4625篇 |
2017年 | 4172篇 |
2016年 | 6475篇 |
2015年 | 6082篇 |
2014年 | 7558篇 |
2013年 | 9794篇 |
2012年 | 11896篇 |
2011年 | 12426篇 |
2010年 | 8257篇 |
2009年 | 7936篇 |
2008年 | 8659篇 |
2007年 | 7620篇 |
2006年 | 7068篇 |
2005年 | 5792篇 |
2004年 | 4431篇 |
2003年 | 3503篇 |
2002年 | 3332篇 |
2001年 | 2793篇 |
2000年 | 2423篇 |
1999年 | 2811篇 |
1998年 | 2340篇 |
1997年 | 2309篇 |
1996年 | 2287篇 |
1995年 | 1989篇 |
1994年 | 1711篇 |
1993年 | 1486篇 |
1992年 | 1273篇 |
1991年 | 1151篇 |
1990年 | 952篇 |
1989年 | 747篇 |
1988年 | 555篇 |
1987年 | 461篇 |
1986年 | 488篇 |
1985年 | 393篇 |
1984年 | 253篇 |
1983年 | 194篇 |
1982年 | 167篇 |
1981年 | 106篇 |
1980年 | 76篇 |
1979年 | 24篇 |
1976年 | 17篇 |
1975年 | 16篇 |
1973年 | 16篇 |
1957年 | 42篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
981.
In this Letter, structural properties of liquid Ni20Al80 have been studied through molecular dynamics (MD) simulations, and results agree well with X-ray experiments. The prepeak in the structure factor manifests the existence of medium-range structural order (MRSO) in liquid Ni20Al80. Analyses in MRSO reveal the dominance of ideal icosahedra and defective icosahedra which, furthermore, form clusters and share common atoms. 相似文献
982.
983.
984.
The goal of this paper is to compute the shape Hessian for a generalized Oseen problem with nonhomogeneous Dirichlet boundary
condition by the velocity method. The incompressibility will be treated by penalty approach. The structure of the shape gradient
and shape Hessian with respect to the shape of the variable domain for a given cost functional are established by an application
of the Lagrangian method with function space embedding technique.
This work was supported by the National Natural Science Fund of China (No. 10371096) for ZM Gao and YC Ma. 相似文献
985.
This paper studies the pullback asymptotic behavior of solutions for a non-autonomous incompressible non-Newtonian fluid in two-dimensional (2D) bounded domains. We first prove the existence of pullback attractors AV in space V (has H2-regularity, see notation in Section 2) and AH in space H (has L2-regularity) for the cocycle corresponding to the solutions of the fluid. Then we verify the regularity of the pullback attractors by showing AV=AH, which implies the pullback asymptotic smoothing effect of the fluid in the sense that the solutions become eventually more regular than the initial data. 相似文献
986.
M K Parida Nita Sinha B Adhikary B Allanach A Alok K S Babu B Brahmachari D Choudhury E J Chun P K Das A Ghosal D Hitlin W S Hou S Kumar H N Li E Ma S K Majee G Majumdar B Mishra G Mohanty S Nandi H Pas M K Parida S D Rindani J P Saha N Sahu Y Sakai S Sen C Sharma C D Sharma S Shalgar N N Singh S Uma Sankar N Sinha R Sinha F Simonetto R Srikanth R Vaidya 《Pramana》2006,67(5):849-860
This is the report of flavor physics and model building working group at WHEPP-9. While activites in flavor physics have been
mainly focused on B-physics, those in model building have been primarily devoted to neutrino physics. We present summary of working group discussions
carried out during the workshop in the above fields, and also briefly review the progress made in some projects subsequently. 相似文献
987.
An enantioselective Michael addition of malonate to nitroalkenes is efficiently catalyzed by low loading demethylquinine salts in water; the yield range from 49% to 93% and the ee up to 90%. 相似文献
988.
Li Zhang James A. Bain Jian-Gang Zhu Leon Abelmann Takahiro Onoue 《Journal of magnetism and magnetic materials》2006
A method of heat-assisted magnetic recording (HAMR) potentially suitable for probe-based storage systems is characterized. In this work, field emission current from a scanning tunneling microscope (STM) tip is used as the heating source. Pulse voltages of 2–7 V were applied to a CoNi/Pt multilayered film fabricated on either bare silicon or oxidized silicon substrates. Different types of Ir/Pt and W STM tips were used in the experiment. The results show that thermally recorded magnetic marks are formed with a nearly uniform mark size of 170 nm on the film fabricated on bare silicon substrate when the pulse voltage is above a threshold voltage. The mark size becomes 260 nm when they are written on the identical film fabricated on an oxidized silicon substrate. The threshold voltage depends on the material work function of the tip, with W having a threshold voltage about 1 V lower than Pt. A synthesized model, which contains the calculation of the emission current, the simulation of heat transfer during heating, and the study of magnetic domain formation, was introduced to explain experimental results. The simulation agrees well with the experiments. 相似文献
989.
第Ⅰ种强度不对称三态叠加多模叠加态光场N次方Y压缩—第一正交相位分量的压缩情况 总被引:2,自引:0,他引:2
根据量子力学中的线性叠加原理,构造了由三个强度不等的多模相干态光场|{Zj(A)}>q、|{Zj(B)}>q和|{Zj(C)}>q的线性叠加所组成的第Ⅰ种强度不对称三态叠加多模叠加态光场|ψl(ABC)>q.利用多模压缩态理论,研究了态|ψl(ABC)>q的第一正交方分量(即磁场分量)的广义非线性等幂次N次方Y压缩特性.结果发现:①在上述各多模相干态光场中各模的强度和各模的初始相位各不相等的情况下,态|ψl(ABC)>q的第一正交分量-磁场分量在一定的条件下,总可呈现出周期性变化的、任意等幂次的N次方Y压缩效应;②当上述各多模相干态光场的强度和各模的初始相位相等时,态|ψl(ABC)>q的磁场分量的N次方Y压缩现象消失,态|ψl(ABC)>q可恒处于等幂次N-Y最小测不准态. 相似文献
990.
本文利用^1HNMR,UV-Vis方法,研究了t-BuNO二聚体在有机溶剂及水溶液中的裂解反应产物,分析了其反应的动力学,提出了在非极性的有机相中t-BuNO二聚体为均裂反应,而在极性的水相中为均裂和异裂同时进行的竞争反应。 相似文献