全文获取类型
收费全文 | 8460篇 |
免费 | 1592篇 |
国内免费 | 2305篇 |
专业分类
化学 | 6459篇 |
晶体学 | 270篇 |
力学 | 579篇 |
综合类 | 249篇 |
数学 | 1162篇 |
物理学 | 3638篇 |
出版年
2024年 | 16篇 |
2023年 | 92篇 |
2022年 | 226篇 |
2021年 | 246篇 |
2020年 | 349篇 |
2019年 | 357篇 |
2018年 | 300篇 |
2017年 | 336篇 |
2016年 | 353篇 |
2015年 | 415篇 |
2014年 | 540篇 |
2013年 | 656篇 |
2012年 | 690篇 |
2011年 | 748篇 |
2010年 | 686篇 |
2009年 | 676篇 |
2008年 | 726篇 |
2007年 | 744篇 |
2006年 | 760篇 |
2005年 | 550篇 |
2004年 | 454篇 |
2003年 | 279篇 |
2002年 | 360篇 |
2001年 | 324篇 |
2000年 | 297篇 |
1999年 | 243篇 |
1998年 | 149篇 |
1997年 | 129篇 |
1996年 | 113篇 |
1995年 | 99篇 |
1994年 | 93篇 |
1993年 | 65篇 |
1992年 | 62篇 |
1991年 | 31篇 |
1990年 | 42篇 |
1989年 | 22篇 |
1988年 | 24篇 |
1987年 | 22篇 |
1986年 | 18篇 |
1985年 | 6篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1965年 | 1篇 |
1964年 | 4篇 |
1959年 | 3篇 |
1909年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 234 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.
设X是维数大于2的Banach空间,映射δ:B(X)→B(X)是2-局部Lie三重导子,则对所有A∈B(X)有δ(A)=[A,T]+φ(A),这里T∈B(X),φ是从B(X)到FI的齐次映射且满足对所有A,B∈B(X)有φ(A+B)=φ(A),其中B是交换子的和. 相似文献
3.
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
4.
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
5.
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
6.
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
7.
Nonlinear Dynamics - A robust fixed-time control framework is presented to stabilize flexible spacecraft’s attitude system with external disturbance, uncertain parameters of inertia, and... 相似文献
8.
9.
设γM(G)是连通图G=(V,E)的最大亏格,记EM^-(G)={e∈E(G)|G\e连通,且γM(G\e)=γM(G)}。若EM^-(G)≠0,则称G是γ(G)-可约的;否则称G是γM(G)-不可约的。本文证明了边的剖分不改变图的最大亏格可约性,点的扩张不改变上可嵌入图的最大亏格可约性;并给出了两类满足EM^-(G)=E(G)的非4-边连通图。 相似文献
10.
Polymethyl methacrylate (PMMA) is one of the most commonly used optical materials. However, the application of it in the area of optical communication is strongly limited by the intrinsic absorption loss of carbon-hydrogen stretching vibration. In this paper, we present a method to solve the problem by adopting the hollow-core fibers with cobweb cladding structure. The fibers use a single dielectric material and may solve the problem of structural support. Thus the feasibility of the “OmniGuide” fibers is improved, while a series of advantages of the “OmniGuide” hollow-core fiber are retained. It is promising that a fiber with low transmission loss, high bandwidth, large-core, and low costs can be designed and fabricated using PMMA. At the same time, a very broad range of the wavelengths (from visible to near infrared region, for instance, wavelengths at 0.65-1.12 μm, and even 1.30 μm, 1.54 μm and their neighbors) may be adopted for signal wavelength. 相似文献