全文获取类型
收费全文 | 8032篇 |
免费 | 1265篇 |
国内免费 | 911篇 |
专业分类
化学 | 5825篇 |
晶体学 | 76篇 |
力学 | 516篇 |
综合类 | 65篇 |
数学 | 945篇 |
物理学 | 2781篇 |
出版年
2024年 | 30篇 |
2023年 | 163篇 |
2022年 | 202篇 |
2021年 | 297篇 |
2020年 | 335篇 |
2019年 | 325篇 |
2018年 | 278篇 |
2017年 | 256篇 |
2016年 | 427篇 |
2015年 | 361篇 |
2014年 | 452篇 |
2013年 | 618篇 |
2012年 | 727篇 |
2011年 | 741篇 |
2010年 | 495篇 |
2009年 | 457篇 |
2008年 | 481篇 |
2007年 | 414篇 |
2006年 | 389篇 |
2005年 | 344篇 |
2004年 | 300篇 |
2003年 | 255篇 |
2002年 | 234篇 |
2001年 | 199篇 |
2000年 | 178篇 |
1999年 | 179篇 |
1998年 | 147篇 |
1997年 | 128篇 |
1996年 | 128篇 |
1995年 | 100篇 |
1994年 | 88篇 |
1993年 | 74篇 |
1992年 | 64篇 |
1991年 | 53篇 |
1990年 | 58篇 |
1989年 | 39篇 |
1988年 | 21篇 |
1987年 | 18篇 |
1986年 | 24篇 |
1985年 | 28篇 |
1984年 | 25篇 |
1983年 | 18篇 |
1982年 | 11篇 |
1981年 | 13篇 |
1977年 | 3篇 |
1973年 | 3篇 |
1971年 | 2篇 |
1957年 | 2篇 |
1944年 | 4篇 |
1942年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
961.
Jin Bai Kin 《数学研究及应用》1991,11(2):203-206
We construct real valued functions from infinite sequences. We also consider some properties of such functions and null sequences. 相似文献
962.
963.
Wang J Ma T Zhang Z Zhang X Jiang Y Zhang G Zhao G Zhao H Zhang P 《Ultrasonics sonochemistry》2007,14(2):246-252
The transition crystal TiO(2) sonocatalyst was prepared utilizing the method of ultrasonic irradiation in hydrogen peroxide solution. The sonocatalytic activity of the transition crystal TiO(2) powder was validated through the degradation of methyl orange in aqueous solution by ultrasonic irradiation. The results show that the sonocatalytic activity of the transition crystal TiO(2) powder is obviously higher than that of pure rutile and anatase TiO(2) powders as well as mixed rutile and anatase TiO(2) powders according to the proportion of corresponding transition crystal TiO(2) catalyst. The degradation ratio of methyl orange in the presence of the transition crystal TiO(2) catalyst surpasses 75% within 80 min ultrasonic irradiation, while the degradation ratios are 55.93%, 51.68% and 40.88%, respectively, for rutile, mixed and anatase TiO(2) powders. 相似文献
964.
Zhi-Qing Zhang Zhi-Lin Guan Yan-Chao Zhao Zi-Yu Zhang Zhi-Jie Sun Na Wang Xiao-Dong Ren 《中国物理C(英文版)》2023,47(1):013103-013103-9
We study the \begin{document}$ B_{c,u,d}\to X(3872)P $\end{document} ![]()
![]()
decays in the perturbative QCD (PQCD) approach, involving the puzzling resonance \begin{document}$ X(3872) $\end{document} ![]()
![]()
, where P represents a light pseudoscalar meson (K or π). Assuming \begin{document}$ X(3872) $\end{document} ![]()
![]()
to be a \begin{document}$ 1^{++} $\end{document} ![]()
![]()
charmonium state, we obtain the following results. (a) The branching ratios of the \begin{document}$ B^+_c\to X(3872)\pi^+ $\end{document} ![]()
![]()
and \begin{document}$ B^+_c\to X(3872) K^+ $\end{document} ![]()
![]()
decays are consistent with the results predicted by the covariant light-front approach within errors; however, they are larger than those given by the generalized factorization approach. (b) The branching ratio of the \begin{document}$ B^+\to X(3872)K^+ $\end{document} ![]()
![]()
decay is predicted as \begin{document}$ (3.8^{+1.1}_{-1.0})\times10^{-4} $\end{document} ![]()
![]()
, which is smaller than the previous PQCD calculation result but still slightly larger than the upper limits set by Belle and BaBar. Hence, we suggest that the\begin{document}$ B^{0,+}\to X(3872)K^{0,+} $\end{document} ![]()
![]()
decays should be precisely measured by the LHCb and Belle II experiments to help probe the inner structure of \begin{document}$ X(3872) $\end{document} ![]()
![]()
. (c) Compared with the \begin{document}$ B_{u,d}\to X(3872)K $\end{document} ![]()
![]()
decays, the \begin{document}$ B_{u,d}\to X(3872)\pi $\end{document} ![]()
![]()
decays have significantly smaller branching ratios, which drop to values as low as \begin{document}$ 10^{-6} $\end{document} ![]()
![]()
. (d) The direct CP violations of these considered decays are small (\begin{document}$ 10^{-3}\sim 10^{-2} $\end{document} ![]()
![]()
) because the penguin contributions are loop suppressed compared to the tree contributions. The mixing-induced CP violation of the \begin{document}$ B\to X(3872)K^0_S $\end{document} ![]()
![]()
decay is highly consistent with the current world average value \begin{document}$ \sin2\beta=(69.9\pm1.7)$\end{document} ![]()
![]()
%. Experimentally testing the results for the branching ratios and CP violations, including the implicit \begin{document}$S U(3)$\end{document} ![]()
![]()
and isospin symmetries of these decays, helps probe the nature of \begin{document}$ X(3872) $\end{document} ![]()
![]()
. 相似文献
965.
A model for dependent default with hyperbolic attenuation effect and valuation of credit default swap 总被引:1,自引:0,他引:1
A hyperbolic function is introduced to reflect the attenuation effect of one firm's default to its partner.If two firms are competitors(copartners),the default inten- sity of one firm will decrease(increase)abruptly when the other firm defaults.As time goes on,the impact will decrease gradually until extinct.In this model,the joint distri- bution and marginal distributions of default times are derived by employing the change of measure,and the fair swap premium of a credit default swap(CDS)can be valued. 相似文献
966.
圆形重力式网箱锚碇系统的受力研究 总被引:6,自引:0,他引:6
依据Stokes二阶波浪理论和莫里森(Morison)方法,对圆形重力式网箱的浮架结构分别与工程上常用的两种锚碇系统(折线形与直线形)相结合情况下,锚碇系统的受力进行了数值计算及相应的物理模型试验。结果表明相同波况下折线形锚碇系统承受张力较小,在相同波浪周期条件下,波高越大锚碇点受力越大;相同波高下,锚碇点最大受力随周期变化不显著。将计算结果与模型试验对比,结果显示计算数值与试验数据较接近,表明了此计算方法的可行性,为进一步模拟浮架结构的运动变形打下基础。 相似文献
967.
968.
969.
介绍了高速旋转构件应力,应变测量的新方法───红外遥测法,叙述了该法的基本工作原理、仪器结构方框图及其主要参数,并且提供了测试实例。 相似文献
970.
Ming Lu Shu Bai Kun Yang Yan Sun 《中国颗粒学报》2007,5(1):180-185
Non-porous magnetic polymer microspheres with a core-shell structure were prepared by a novel micro-suspension polymerization technique. A stable iron oxide ferrofluid was used to supply the magnetic core, and the polymeric shell was made of glycidyl methacrylate (GMA monomer) and ethylene dimethacrylate (cross-linker). In the preparation, polyvinyl alcohol was used as the stabilizer, and a lauryl alcohol mixture as the dispersant. The influence of various conditions such as aqueous phase volume, GMA and initiator amounts, reaction time and stirring speed on the character of the microspheres was investigated. The magnetic microspheres were then characterized briefly. The results indicate that the microspheres with active epoxy groups had a narrow size distribution range from 1 to 10 μm with a volume-weighted mean diameter of 4.5 μm. The saturation magnetization reached 19.9 emu/g with little coercivity and remanence. 相似文献