全文获取类型
收费全文 | 99059篇 |
免费 | 5422篇 |
国内免费 | 4630篇 |
专业分类
化学 | 56236篇 |
晶体学 | 1331篇 |
力学 | 5582篇 |
综合类 | 322篇 |
数学 | 11833篇 |
物理学 | 33807篇 |
出版年
2023年 | 749篇 |
2022年 | 1710篇 |
2021年 | 2094篇 |
2020年 | 2311篇 |
2019年 | 2506篇 |
2018年 | 2892篇 |
2017年 | 2823篇 |
2016年 | 3486篇 |
2015年 | 2409篇 |
2014年 | 3477篇 |
2013年 | 4920篇 |
2012年 | 5055篇 |
2011年 | 5356篇 |
2010年 | 4251篇 |
2009年 | 4256篇 |
2008年 | 4456篇 |
2007年 | 4173篇 |
2006年 | 3804篇 |
2005年 | 3375篇 |
2004年 | 3036篇 |
2003年 | 2711篇 |
2002年 | 2827篇 |
2001年 | 2547篇 |
2000年 | 1987篇 |
1999年 | 1601篇 |
1998年 | 1534篇 |
1997年 | 1329篇 |
1996年 | 1293篇 |
1995年 | 1077篇 |
1994年 | 1156篇 |
1993年 | 1095篇 |
1992年 | 1062篇 |
1991年 | 1124篇 |
1990年 | 1118篇 |
1989年 | 1039篇 |
1988年 | 917篇 |
1987年 | 914篇 |
1986年 | 881篇 |
1985年 | 921篇 |
1984年 | 915篇 |
1983年 | 822篇 |
1982年 | 800篇 |
1979年 | 801篇 |
1978年 | 812篇 |
1977年 | 806篇 |
1976年 | 919篇 |
1975年 | 812篇 |
1974年 | 844篇 |
1973年 | 847篇 |
1972年 | 752篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
Based on the theory of calculus of variation, some suffcient conditions are given for some Euler-Lagrangcequations to be equivalently represented by finite or even infinite many Hamiltonian canonical equations. Meanwhile,some further applications for equations such as the KdV equation, MKdV equation, the general linear Euler Lagrangeequation and the cylindric shell equations are given. 相似文献
192.
Yu. G. Abov A. D. Gul'ko F. S. Dzheparov S. V. Stepanov S. S. Trostin 《Physics of Atomic Nuclei》2002,65(11):1999-2008
The nuclear magnetic resonance in beta-active nuclei 8Li at the doubled Larmor frequency in LiF polycrystals is studied before and after treating these polycrystals with an external pressure. A quantitative approach is proposed that makes it possible to calculate the parameters of the resonance line-shape function versus the dislocation structure of crystallites. Data suggesting that the samples under investigation that were subjected to a treatment with an external pressure develop dislocations whose Burgers vectors are parallel are obtained. 相似文献
193.
194.
The maximum likely and optimal (Bayesian) algorithms for detecting an arbitrary-shaped signal observed against the background of Gaussian white noise and for measuring the duration are synthesized. Exact expressions for the characteristics of the maximum likely algorithms are found. The characteristics of the Bayesian algorithms are obtained using computer simulations. 相似文献
195.
Atomic-force microscopy was used to study the surface topography of SiGe structures grown by epitaxial deposition of Ge on profiled Si(111) substrates under electromigration conditions. Systems of highly ordered germanium nanosized islands with dimensions of 10–20 nm and a density of 6×1010 cm?2 were obtained. It is shown that the geometrical parameters of self-organizing nanoislands can be controlled by a proper choice of the growth and postgrowth annealing conditions for these structures. 相似文献
196.
V. A. Kulbachinskiĭ A. Yu. Kaminskiĭ P. M. Tarasov P. Lostak 《Physics of the Solid State》2006,48(5):833-840
The Fermi surface anisotropy of (Bi1?x Sbx)2Te3 single crystals (0.25 ≤ x ≤ 1) was studied by analyzing the angular dependence of the frequency of Shubnikov-de Haas oscillations and the effect of tin and silver doping on the thermoelectric power in these crystals in the temperature range 77 ≤ T ≤ 300 K. It was shown that silver doping of (Bi1?x Sbx)2Te3 mixed crystals produces acceptors, while silver in Bi2Te3 acts as a donor. Tin also exhibits acceptor properties. Both tin and silver doping of p-(Bi1?x Sbx)2Te3 mixed crystals decrease the thermoelectric power due to an increase in the hole concentration. 相似文献
197.
ZHANG Lin-bo LIU Xiao-hua JIANG Yuan GUO Ping SHA Li-jin LI Yu 《高等学校化学研究》2006,22(2):139-144
After establishing hemi-Parkinsonian rat models, the relationships between neuron death and the expression of several proteins, such as c-Fos, GFAP, GDNF, NF-κB and some cytokines were determined. Therapeutics experiments with notoginsenoside-Rg1 were carried out. The research results show that the expressions of GFAP, NF-Kκ and c-Fos will obviously increase in the lesion side of the striatum and the expression of GDNF will decrease, which implies that the signal transduction pathway may participate in the apoptosis in neurons. The levels of some cytokines such as TNF-α, IL-1β in the striatum of PD rat models increased compared to those of normal rats. The results of the therapeutics experiments show that notoginsenoside-Rg1 may repress the immune inflammation response and regulate the immune function through the neuro-immune molecular network. Therefore, notoginsenoside-Rg1 can be used as an effective drug for anti-oxidation and anti-inflammation, and can be used in the therapy of Parkinson's disease(PD). 相似文献
198.
V. P. Nekhoroshev Yu. P. Turov A. V. Nekhorosheva V. D. Ogorodnikov K. N. Gaevoi 《Russian Journal of Applied Chemistry》2006,79(5):833-840
The composition and structure of low-molecular-weight products of thermal oxidative degradation of atactic polypropylene were studied. 相似文献
199.
We describe a scheme of stochastic implementations of quantum teleportation and entanglement swapping in terms of neutral kaons. In this scheme, the kaon whose state is to be teleported collides with one of the two entangled kaons in an Einstein–Podolsky–Rosen state. Subsequent detection of the outgoing particles of the collision completes the two-qubit projection on Alice side. There appear novel features, which connects quantum information science with fundamental laws of particle physics. 相似文献
200.
In this paper, we study an evasion problem in systems described by equations of parabolic type. We consider four versions of constraints on the control parameters. 相似文献