全文获取类型
收费全文 | 22277篇 |
免费 | 3948篇 |
国内免费 | 6194篇 |
专业分类
化学 | 17863篇 |
晶体学 | 683篇 |
力学 | 1157篇 |
综合类 | 541篇 |
数学 | 3063篇 |
物理学 | 9112篇 |
出版年
2024年 | 47篇 |
2023年 | 272篇 |
2022年 | 755篇 |
2021年 | 782篇 |
2020年 | 794篇 |
2019年 | 857篇 |
2018年 | 744篇 |
2017年 | 953篇 |
2016年 | 911篇 |
2015年 | 1152篇 |
2014年 | 1420篇 |
2013年 | 1933篇 |
2012年 | 1933篇 |
2011年 | 2081篇 |
2010年 | 1786篇 |
2009年 | 1743篇 |
2008年 | 1970篇 |
2007年 | 1824篇 |
2006年 | 1677篇 |
2005年 | 1432篇 |
2004年 | 1131篇 |
2003年 | 917篇 |
2002年 | 857篇 |
2001年 | 850篇 |
2000年 | 807篇 |
1999年 | 514篇 |
1998年 | 308篇 |
1997年 | 233篇 |
1996年 | 228篇 |
1995年 | 200篇 |
1994年 | 171篇 |
1993年 | 163篇 |
1992年 | 126篇 |
1991年 | 124篇 |
1990年 | 115篇 |
1989年 | 94篇 |
1988年 | 85篇 |
1987年 | 58篇 |
1986年 | 57篇 |
1985年 | 55篇 |
1984年 | 55篇 |
1983年 | 54篇 |
1982年 | 38篇 |
1981年 | 22篇 |
1980年 | 26篇 |
1979年 | 16篇 |
1978年 | 9篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1974年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Ying Zhang Gang Hu Shigang Chen H.A. Cerdeira 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(3):381-384
A method of controlling global stochasticity in Hamiltonian systems by applying nonlinear perturbation is proposed. With the
well-known standard map we demonstrate that this control method can convert global stochasticity into regular motion in a
wide chaotic region for arbitrary initial condition, in which the control signal remains very weak after a few kicks. The
system in which chaos has been controlled approximates to the original Hamiltonian system, and this approach appears robust
against small external noise. The mechanism underlying this high control efficiency is intuitively explained.
Received 15 January 2002 Published online 6 June 2002 相似文献
63.
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
64.
65.
Jiaqiang Wang Hua Fang Ying Li Junjie Li Zhiying Yan 《Journal of molecular catalysis. A, Chemical》2006,250(1-2):75-79
Cobalt-doped mesoporous titania with a crystalline framework synthesized by surfactant templating method presented highly selective (99%) and reasonable conversion rate (49%) of catalytic oxidation of para-chlorotoluene to para-chlorobenzaldehyde in acetic acid using aqueous hydrogen peroxide as oxidant for the first time. Recycling of the catalyst indicates that the catalyst can be used a number of times without losing its activity to a greater extent. By contrast, cobalt-doped mesoporous titania without a crystalline structure and cobalt doped the commercial titania, Degussa P25 prepared by impregnation method with the similar concentration of cobalt were found inactive. The effects of catalyst concentration, reaction time, reaction temperature, and solvents on the performance of the catalyst were also investigated. 相似文献
66.
It is shown that the configuration of phase coding for quantum key distribution with single photon can also be used for continuous variable quantum key distribution. Therefore the robust long-distance high-speed quantum key distribution can be achieved with current technology. 相似文献
67.
基于傅立叶变换轮廓术的物面相位提取 总被引:1,自引:0,他引:1
采用傅立叶变换轮廓术,针对基频提取的关键技术采用逐行傅立叶变换,准确提取基频信息的方法恢复相位信息.在此基础上,以未畸变条纹为基准,得出被测物体的真实位相值.该方法只需一幅条纹图,节约了测量时间.实验证明可实现无接触面型的自动传感. 相似文献
68.
设(X,d)是一个可分的度量空间,Cu(X,d)是由全体一致连续函数所组成的C(X,d)的子空间,T是定义在X上的一致Lipschitz映射,那么对f∈Cu(X),1/n n∑k=1 Uk If在Cu(X)上收敛.从这个基本结果出发,利用Cu(X,d)的共扼空间的表示定理,得到了相空间的Yosida型遍历分解;利用空间的嵌入技术证明了非一致Lipschitz映射的大数法则. 相似文献
69.
简要叙述了稠密等离子体聚焦装置作为中子发生器的工作原理,对影响稠密等离子体聚焦装置放电出中子产额及其稳定性的一些因素和改进措施进行了简单讨论.通过使用不同电极形状的场畸变开关很好地提高了焦点装置的运行,使装置输出中子的起伏得到明显的改善.通过对腔内电极的清洁,在不更换气体的条件下,聚焦装置放电出中子产额稳定.The principle of dense plasma focus(DPF) as neutron generator has been investigated in this paper. We have stated briefly some factors that mainly influnce the DPF s neutron yield and some methods improving the stability of neutron yields on the dense plasma focus. It is showed that the fluctuation of DPF output neutron becomes smaller by using different types of field-distortion elements. Over 100 consecutive shots without purging the test gas the neutron yields has no obvious change. 相似文献
70.
This study presents a compact optical configuration that can generate a multiplex dot-matrix hologram with complex interlaced images for anti-counterfeiting applications on valuable paper. Varying the orientation of the interference plane can enable the multiplex hologram to be recorded without changing the interference angle of two laser beams. With its simple asymmetric optical setup, a multiplex hologram with many interlaced images can be efficiently fabricated, increasing the cost of imitation. Experimental details of the asymmetric optical setup are also described. 相似文献