全文获取类型
收费全文 | 11874篇 |
免费 | 2400篇 |
国内免费 | 2022篇 |
专业分类
化学 | 8678篇 |
晶体学 | 210篇 |
力学 | 747篇 |
综合类 | 150篇 |
数学 | 1332篇 |
物理学 | 5179篇 |
出版年
2024年 | 29篇 |
2023年 | 227篇 |
2022年 | 301篇 |
2021年 | 419篇 |
2020年 | 578篇 |
2019年 | 543篇 |
2018年 | 496篇 |
2017年 | 456篇 |
2016年 | 651篇 |
2015年 | 645篇 |
2014年 | 760篇 |
2013年 | 952篇 |
2012年 | 1243篇 |
2011年 | 1224篇 |
2010年 | 907篇 |
2009年 | 886篇 |
2008年 | 980篇 |
2007年 | 828篇 |
2006年 | 687篇 |
2005年 | 572篇 |
2004年 | 447篇 |
2003年 | 350篇 |
2002年 | 350篇 |
2001年 | 297篇 |
2000年 | 242篇 |
1999年 | 210篇 |
1998年 | 144篇 |
1997年 | 118篇 |
1996年 | 114篇 |
1995年 | 87篇 |
1994年 | 93篇 |
1993年 | 65篇 |
1992年 | 67篇 |
1991年 | 58篇 |
1990年 | 58篇 |
1989年 | 40篇 |
1988年 | 31篇 |
1987年 | 17篇 |
1986年 | 21篇 |
1985年 | 25篇 |
1984年 | 20篇 |
1983年 | 15篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1979年 | 3篇 |
1977年 | 2篇 |
1974年 | 4篇 |
1972年 | 2篇 |
1966年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
SONG Wei QIN Tao 《理论物理通讯》2008,49(6):1515-1518
We present a feasible scheme to implement the 1→2 optimal cloning of arbitrary single particle atomic state into two photonic states, which is important for applications in long distance quantum communication. Our scheme also realizes the tele-NOT gate of one atom to the distant atom trapped in another cavity. The scheme is based on the adiabatic passage and the polarization measurement. It is robust against a number of practical noises such as the violation of the Lamb Dicke condition, spontaneous emission, and detection inefficiency. 相似文献
972.
We establish the existence of infinitely many polynomial progressions in the primes; more precisely, given any integer-valued polynomials P
1, …, P
k
∈ Z[m] in one unknown m with P
1(0) = … = P
k
(0) = 0, and given any ε > 0, we show that there are infinitely many integers x and m, with
1 \leqslant m \leqslant xe1 \leqslant m \leqslant x^\varepsilon, such that x + P
1(m), …, x + P
k
(m) are simultaneously prime. The arguments are based on those in [18], which treated the linear case P
j
= (j − 1)m and ε = 1; the main new features are a localization of the shift parameters (and the attendant Gowers norm objects) to both coarse
and fine scales, the use of PET induction to linearize the polynomial averaging, and some elementary estimates for the number
of points over finite fields in certain algebraic varieties. 相似文献
973.
合成并表征了3个Schiff碱配体及由其桥联的3个双核钌配合物,并通过核磁共振谱、红外光谱、质谱及元素分析等测试手段对配体及化合物进行了表征.电化学测试结果表明,在3个双核配合物中存在着分子内的金属-金属间相互作用,且连接两个金属的桥配体是影响金属间相互作用强弱的关键因素. 相似文献
974.
Three copolymers (bearing metal ion coordinated sites) P1 , P2 and P3 were synthesized and their recognition behavior on predetermined peptide sequences was studied by isothermal titration calorimetry. 相似文献
975.
976.
发射方向调制信号的多波束调制技术 总被引:1,自引:0,他引:1
为了使单天线接收机通过接收解调信号能实现通信和方向测量功能,提出了一种多波束调制的概念.它利用双波束或多波束的空间特性来实现数字调制和方向调制.设计了一个六元线天线发射阵列,将中间的四元天线两两成对激励,形成双波束,用双波束调制实现数字通信和方向粗测,然后对大间距的二元天线用不同的相差激励,形成有错位的多波束,用多波束调制实现数字通信和方向精测.仿真结果表明这种多波束调制实现了在调制信号设计层面上的数字通信与测向的深度综合. 相似文献
977.
Large-deviation probabilities for maxima of sums of subexponential random variables with application to finite-time ruin probabilities 总被引:1,自引:0,他引:1
Tao Jiang 《中国科学A辑(英文版)》2008,51(7):1257-1265
We establish an asymptotic relation for the large-deviation probabilities of the maxima of sums of subexponential random variables centered by multiples of order statistics of i.i.d.standard uniform random variables.This extends a corresponding result of Korshunov.As an application,we generalize a result of Tang,the uniform asymptotic estimate for the finite-time ruin probability,to the whole strongly subexponential class. 相似文献
978.
979.
980.
Tao Zhang Hongliang Fan Jianguang Zhou Qinhan Jin 《Journal of polymer science. Part A, Polymer chemistry》2009,47(12):3056-3065
This article reports the synthesis, optical properties, and pH responses of a water‐soluble poly(phenylene ethynylene) with pendant carboxylate groups. This conjugated polyelectrolyte, PPE‐OBS, was prepared via a facile synthetic route, using 1,4‐di(ethyl 4‐oxy‐butyrate)‐2,5‐diiodo‐benzene as polymeric monomer and followed by the alkali induced saponification. PPE‐OBS absorbs strongly in the blue region and emits a moderately intense fluorescence. However, it subjects to unstable emission in neutral aqueous media, which is believed to arise because the polymer tends to become more hydrophobic via protonation and to form much heavier aggregates (clusters). Subsequent studies on the interaction and stabilization of PPE‐OBS with various surfactants indicate that its fluorescence stability can be largely improved in the presence of a small amount of surfactant. More interestingly, even at low pH, the surfactant‐stabilized polyelectrolyte with its pendant groups being ? COOH rather than ? COO? remains water‐soluble and emits efficiently, which is expected of great significance for the covalent linkage to bio‐molecules. In addition, the sensitive pH response in emission spectrum of PPE‐OBS/surfactant complex over a relatively wide range suggests surely a potential access to the fluorescent sensing of pH variation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3056–3065, 2009 相似文献