全文获取类型
收费全文 | 10183篇 |
免费 | 1715篇 |
国内免费 | 1173篇 |
专业分类
化学 | 7304篇 |
晶体学 | 121篇 |
力学 | 566篇 |
综合类 | 38篇 |
数学 | 1294篇 |
物理学 | 3748篇 |
出版年
2024年 | 18篇 |
2023年 | 256篇 |
2022年 | 332篇 |
2021年 | 398篇 |
2020年 | 483篇 |
2019年 | 423篇 |
2018年 | 394篇 |
2017年 | 399篇 |
2016年 | 529篇 |
2015年 | 501篇 |
2014年 | 598篇 |
2013年 | 742篇 |
2012年 | 931篇 |
2011年 | 990篇 |
2010年 | 625篇 |
2009年 | 669篇 |
2008年 | 658篇 |
2007年 | 599篇 |
2006年 | 555篇 |
2005年 | 460篇 |
2004年 | 311篇 |
2003年 | 284篇 |
2002年 | 257篇 |
2001年 | 194篇 |
2000年 | 166篇 |
1999年 | 188篇 |
1998年 | 161篇 |
1997年 | 140篇 |
1996年 | 143篇 |
1995年 | 106篇 |
1994年 | 98篇 |
1993年 | 78篇 |
1992年 | 84篇 |
1991年 | 69篇 |
1990年 | 53篇 |
1989年 | 39篇 |
1988年 | 27篇 |
1987年 | 25篇 |
1986年 | 15篇 |
1985年 | 16篇 |
1984年 | 7篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1977年 | 3篇 |
1973年 | 2篇 |
1957年 | 3篇 |
1929年 | 2篇 |
1926年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Chunhong Wang Qi Cui Zhixin Zhang Prof. Zhu-Jun Yao Dr. Shaozhong Wang Prof. Zhi-Xiang Yu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(42):9821-9826
1,3-Azaprotio transfer of propargylic α-ketocarboxylate oximes, a new type of alkynyl oximes featuring an ester tether, has been explored by taking advantage of gold catalysis. The incorporation of an oxygen atom to the chain of alkynyl oximes led to the formation of two different oxa-cyclic nitrones. It was found that internal alkynyl oximes with an E-configuration deliver five-membered nitrones, whereas terminal alkynyl oximes with an E-configuration afford six-membered nitrones. DFT calculations on four possible pathways supported a stepwise formation of C−N and C−H bonds, in which a 1,3-acyloxy-migration competes with the 1,3-azaprotio-transfer, especially in the case of internal alkynyl oximes. The relative nucleophilic properties of oxygen in the carbonyl group and the nitrogen in the oxime, the electronic effects of alkynes, and the influence of the ring system have been investigated computationally. 相似文献
12.
It is believed that there are more fundamental gauge symmetries beyond those described by the Standard Model of particle physics. The scales of these new gauge symmetries are usually too high to be reachable by particle colliders. Considering that the phase transition (PT) relating to the spontaneous breaking of new gauge symmetries to the electroweak symmetry might be strongly first order, we propose considering the stochastic gravitational waves (GW) arising from this phase transition as an indirect way of detecting these new fundamental gauge symmetries. As an illustration, we explore the possibility of detecting the stochastic GW generated from the PT of \begin{document}$ {\bf{B}}-{\bf{L}}$\end{document} ![]()
![]()
in the space-based interferometer detectors. Our study demonstrates that the GW energy spectrum is reachable by the LISA, Tianqin, Taiji, BBO, and DECIGO experiments only for the case where the spontaneous breaking of \begin{document}$ {\bf{B}}-{\bf{L}}$\end{document} ![]()
![]()
is triggered by at least two electroweak singlet scalars. 相似文献
13.
A new method for controlling the quantum coherence of atom laser by applying input light with strong strength is presented
within the framework of quantum dynamical theory. Unlike the case of rotating wave approximation(RWA), we show that the non-classical
properties, such as sub-Poisson distribution and quadrature squeezed effect, can appear in the output atom laser beam with
time. By choosing suitable initial RF phase, a steady and brighter output of squeezed coherent atom laser is also available. 相似文献
14.
15.
16.
17.
18.
Shangbin Cui 《Journal of Fourier Analysis and Applications》2005,11(4):441-457
In this article we establish pointwise estimates for a class of oscillatory integrals
related to the fundamental solution of the dispersive equation ∂t u − iP (Dx)u = 0, where P(Dx)
is a differential operator whose symbol P(ξ) is a real polynomial in one variable. Then we use
such pointwise estimates to establish Lp–Lq estimates for the solution of this equation. 相似文献
19.
We derive the Friedmann-like equations in braneworld cosmology by imposing the first law of thermodynamics and Bekenstein's area-entropy formula on the apparent horizon of a Friedmann–Robertson–Walker universe in both Randall–Sundrum II gravity and Dvali–Gabadadze–Porrati gravity models. Israel's boundary condition plays an important role in our calculations in both cases, besides the first law of thermodynamics and Bekenstein's area-entropy formula. The results indicate that thermodynamics on the brane world knows the behaviors of gravity. 相似文献
20.
Mid-infrared generation based on a periodically poled LiNbO3 optical parametric oscillator
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We report a nanosecond Nd:YVO_4-pumped optical parametric oscillator (OPO) based on periodically poled LiNbO_3 (PPLN). Tuning is achieved in this experiment by varying the temperature and period of the PPLN. The design of double-pass singly resonant oscillator (DSRO) and confocal cavity enables the OPO threshold to be lowered considerably, resulting in a simple, compact, all-solid-state configuration with the mid-infrared idler powers of up to 466mW at 3.41μm. 相似文献