全文获取类型
收费全文 | 41946篇 |
免费 | 5575篇 |
国内免费 | 3496篇 |
专业分类
化学 | 23202篇 |
晶体学 | 610篇 |
力学 | 2298篇 |
综合类 | 752篇 |
数学 | 7244篇 |
物理学 | 16911篇 |
出版年
2024年 | 40篇 |
2023年 | 343篇 |
2022年 | 698篇 |
2021年 | 1027篇 |
2020年 | 1143篇 |
2019年 | 1114篇 |
2018年 | 1059篇 |
2017年 | 1450篇 |
2016年 | 1735篇 |
2015年 | 1579篇 |
2014年 | 2029篇 |
2013年 | 3557篇 |
2012年 | 2432篇 |
2011年 | 2546篇 |
2010年 | 2319篇 |
2009年 | 2623篇 |
2008年 | 2646篇 |
2007年 | 2623篇 |
2006年 | 2458篇 |
2005年 | 2134篇 |
2004年 | 2001篇 |
2003年 | 1701篇 |
2002年 | 1678篇 |
2001年 | 1232篇 |
2000年 | 1173篇 |
1999年 | 1048篇 |
1998年 | 894篇 |
1997年 | 752篇 |
1996年 | 623篇 |
1995年 | 663篇 |
1994年 | 489篇 |
1993年 | 438篇 |
1992年 | 420篇 |
1991年 | 290篇 |
1990年 | 281篇 |
1989年 | 234篇 |
1988年 | 235篇 |
1987年 | 191篇 |
1986年 | 155篇 |
1985年 | 161篇 |
1984年 | 144篇 |
1983年 | 78篇 |
1982年 | 138篇 |
1981年 | 80篇 |
1980年 | 66篇 |
1979年 | 103篇 |
1978年 | 45篇 |
1977年 | 35篇 |
1976年 | 24篇 |
1973年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
81.
在不同激光脉宽下的高次谐波 总被引:3,自引:2,他引:1
用数值计算方法计算了不同强激光脉冲宽度下高次谐波的产生.我们发现对于激光场强度不高,不能有效电离初态的激光场,长脉冲宽度可以更有效产生高次谐波;而对于高场强的激光场,由于它能够在几个光学周期之内把原子的初态全部电离,所以短脉冲的激光场能够更有效产生高次谐波. 相似文献
82.
83.
介绍了13~18世纪物理学史和科技史上曾名噪一时的第一类永动机的设计方案的破灭.第一类永动机幻梦破灭的历史引起了人们的反思与启示,有力地促进了19世纪中叶能量转化和守恒定律的确立. 相似文献
84.
E. A. Bailov N. Temirgaliev 《Computational Mathematics and Mathematical Physics》2006,46(9):1515-1525
Sharp estimates (in the power scale) are obtained for the discretization error in the solutions to Poisson’s equation whose right-hand side belongs to a Korobov class. Compared to the well-known Korobov estimate, the order is almost doubled and has an ultimate value in the power scale. 相似文献
85.
Monte Carlo simulation within the grand canonical ensemble, the histogram reweighting technique, and finite size scaling analysis are used to explore the phase behaviour of heteronuclear dimers, composed of A and B type atoms, on a square lattice. We have found that for the models with attractive BB and AB nearest-neighbour energy, uBB=uAB=−1, and for non-repulsive energy between AA nearest-neighbour sites, uAA<0, the system belongs to the universality class of the two-dimensional Ising model. However, when uAA>0, the system exhibits a non-universal critical behaviour. We have evaluated the dependences of the critical point characteristics on the value of uAA. 相似文献
86.
87.
A Modified Quasi-Newton Method for Structured Optimization with Partial Information on the Hessian 总被引:2,自引:0,他引:2
This paper develops a modified quasi-Newton method for structured unconstrained optimization with partial information on the
Hessian, based on a better approximation to the Hessian in current search direction. The new approximation is decided by both
function values and gradients at the last two iterations unlike the original one which only uses the gradients at the last
two iterations. The modified method owns local and superlinear convergence. Numerical experiments show that the proposed method
is encouraging comparing with the methods proposed in [4] for structured unconstrained optimization
Presented at the 6th International Conference on Optimization: Techniques and Applications, Ballarat, Australia, December
9–11, 2004 相似文献
88.
89.
M. Brando N. Büttgen V. Fritsch J. Hemberger H. Kaps H.-A. Krug von Nidda M. Nicklas K. Pucher W. Trinkl A. Loidl E.W. Scheidt M. Klemm S. Horn 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(3):289-298
We present susceptibility, microwave resistivity, NMR and heat-capacity results for Li1-xZnx(V1-yTiy)2O4 with 0 ?
x
? 0.3 and 0 ?
y
? 0.3. For all doping levels the susceptibility curves can be fitted with a Curie-Weiss law. The paramagnetic Curie-Weiss temperatures
remain negative with an average value close to that of the pure compound Θ≈ - 36 K. Spin-glass anomalies are observed in the susceptibility, heat-capacity and NMR measurements for both type of dopants.
From the temperature dependence of the spin-lattice relaxation rate we found critical-dynamic behavior in the Zn doped compounds
at the freezing temperatures. For the Ti-doped samples two successive freezing transitions into disordered low-temperature
states can be detected. The temperature dependence of the heat capacity for Zn-doped compounds does not resemble that of canonical
spin glasses and only a small fraction of the total vanadium entropy is frozen at the spin-glass transitions. For pure LiV2O4 the spin-glass transition is completely suppressed. The temperature dependence of the heat capacity for LiV2O4 can be described using a nuclear Schottky contribution and the non-Fermi liquid model, appropriate for a system close to
a spin-glass quantum critical point. Finally an (
x
/
y
,
T
)-phase diagram for the low-doping regime is presented.
Received 16 March 2001 and Received in final form 30 October 2001 相似文献
90.