全文获取类型
收费全文 | 11368篇 |
免费 | 1940篇 |
国内免费 | 1729篇 |
专业分类
化学 | 8436篇 |
晶体学 | 193篇 |
力学 | 667篇 |
综合类 | 125篇 |
数学 | 1326篇 |
物理学 | 4290篇 |
出版年
2024年 | 26篇 |
2023年 | 184篇 |
2022年 | 329篇 |
2021年 | 370篇 |
2020年 | 447篇 |
2019年 | 495篇 |
2018年 | 390篇 |
2017年 | 365篇 |
2016年 | 516篇 |
2015年 | 564篇 |
2014年 | 668篇 |
2013年 | 806篇 |
2012年 | 979篇 |
2011年 | 1054篇 |
2010年 | 723篇 |
2009年 | 688篇 |
2008年 | 767篇 |
2007年 | 727篇 |
2006年 | 690篇 |
2005年 | 577篇 |
2004年 | 469篇 |
2003年 | 370篇 |
2002年 | 359篇 |
2001年 | 324篇 |
2000年 | 271篇 |
1999年 | 317篇 |
1998年 | 240篇 |
1997年 | 212篇 |
1996年 | 196篇 |
1995年 | 168篇 |
1994年 | 155篇 |
1993年 | 106篇 |
1992年 | 99篇 |
1991年 | 99篇 |
1990年 | 71篇 |
1989年 | 40篇 |
1988年 | 39篇 |
1987年 | 37篇 |
1986年 | 22篇 |
1985年 | 20篇 |
1984年 | 14篇 |
1983年 | 24篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1971年 | 1篇 |
1959年 | 1篇 |
1909年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Zhang Bing Yang Jie-qin Liu Ying Hu Bin Yang Yang Zhao Li Lu Qiang 《Cellulose (London, England)》2022,29(12):6565-6578
Cellulose - Heating is essential in various biomass pre-treatments and thermal conversion processes. It is of practical significance to study the characteristics of cellulose-lignin and... 相似文献
2.
Zeng Qing-Wei Wen Zhuo-Yu Fu Jun-Feng Zhou Nan-Run 《International Journal of Theoretical Physics》2021,60(9):3306-3333
International Journal of Theoretical Physics - A new quantum watermark algorithm is presented by combining maximum pixel difference partitioning with the least significant bit substitution... 相似文献
3.
We consider concentrated vorticities for the Euler equation on a smooth domain in the form of supported on well-separated vortical domains , , of small diameters . A conformal mapping framework is set up to study this free boundary problem with being part of unknowns. For any given vorticities and small , through a perturbation approach, we obtain such piecewise constant steady vortex patches as well as piecewise smooth Lipschitz steady vorticities, both concentrated near non-degenerate critical configurations of the Kirchhoff–Routh Hamiltonian function. When vortex patch evolution is considered as the boundary dynamics of , through an invariant subspace decomposition, it is also proved that the spectral/linear stability of such steady vortex patches is largely determined by that of the 2N-dimensional linearized point vortex dynamics, while the motion is highly oscillatory in the 2N-codim directions corresponding to the vortical domain shapes. 相似文献
4.
Cavitation erosion is caused in solids exposed to strong pressure waves developing in an adjacent fluid field. The knowledge of the transient distribution of stresses in the solid is important to understand the cause of damaging by comparisons with breaking points of the material. The modeling of this problem requires the coupling of the models for the fluid and the solid. For this purpose, we use a strategy based on the solution of coupled Riemann problems that has been originally developed for the coupling of 2 fluids. This concept is exemplified for the coupling of a linear elastic structure with an ideal gas. The coupling procedure relies on the solution of a nonlinear equation. Existence and uniqueness of the solution is proven. The coupling conditions are validated by means of quasi‐1D problems for which an explicit solution can be determined. For a more realistic scenario, a 2D application is considered where in a compressible single fluid, a hot gas bubble at low pressure collapses in a cold gas at high pressure near an adjacent structure. 相似文献
5.
We investigate terahertz radiation(T-rays) from a pentacene organic diode at room temperature. The quantum chemistry calculation for frequency-related Huang–Rhys factor of pentacene is also carried out. The results demonstrate that the T-rays can come from a bending vibration of pentacene skeleton after the energy of pentacene exciton transferring to the vibrational excited state via electron–phonon coupling. Frequency and natural bond orbital analytics of pentacene and its derivatives are performed in order to explain the result and develop new materials to get higher emission. This work provides a new way to produce T-rays with a simple device at room temperature. 相似文献
6.
7.
We report a spatially modulated polarimetry scheme by using a zero-order vortex half-wave retarder(ZVHR)and a spatial Fourier analysis method.A ZVHR is employed to analyze the input polarized light and convert it into a vectorial optical field,and an analyzer is set after the ZVHR to form an hourglass intensity pattern due to the spatial polarization modulation.Then,the input light’s Stokes parameters can be calculated by spatial Fourier analysis of the hourglass pattern with a single shot.The working principle of the polarimeter has been analyzed by the Stokes-Mueller formalism,and some quantitative measuring experiments of different polarization states have been demonstrated.The experimental results indicate that the proposed polarimeter is accurate,robust,and simple to use. 相似文献
8.
Acta Mathematica Sinica, English Series - We are interested in the existence and asymptotic behavior for the least energy solutions of the following fractional eigenvalue problem $$\left({\rm{P}}... 相似文献
9.
Chen Fenge Li Bing Peng Xingchun 《Methodology and Computing in Applied Probability》2022,24(2):635-659
Methodology and Computing in Applied Probability - This paper is devoted to the study of an optimal investment and risk control problem for an insurer. The risky asset process and the insurance... 相似文献
10.
Ding Q. Yao M. Wu Sh. Zeng M. Xue N. Wu D. Xu J. 《Journal of Applied Spectroscopy》2022,89(4):712-718
Journal of Applied Spectroscopy - Based on partial least squares (PLS) analysis, the effects of different smoothing points and different preprocessing methods on the accuracy and precision of the... 相似文献