全文获取类型
收费全文 | 124000篇 |
免费 | 9376篇 |
国内免费 | 7754篇 |
专业分类
化学 | 44346篇 |
晶体学 | 1983篇 |
力学 | 6860篇 |
综合类 | 1085篇 |
数学 | 36077篇 |
物理学 | 50779篇 |
出版年
2023年 | 551篇 |
2022年 | 1320篇 |
2021年 | 1869篇 |
2020年 | 1566篇 |
2019年 | 1914篇 |
2018年 | 1713篇 |
2017年 | 1500篇 |
2016年 | 1607篇 |
2015年 | 1608篇 |
2014年 | 2746篇 |
2013年 | 4970篇 |
2012年 | 3020篇 |
2011年 | 3925篇 |
2010年 | 4281篇 |
2009年 | 9333篇 |
2008年 | 10387篇 |
2007年 | 8930篇 |
2006年 | 7781篇 |
2005年 | 5566篇 |
2004年 | 5303篇 |
2003年 | 5316篇 |
2002年 | 8317篇 |
2001年 | 4924篇 |
2000年 | 4501篇 |
1999年 | 4199篇 |
1998年 | 3606篇 |
1997年 | 2728篇 |
1996年 | 2467篇 |
1995年 | 2776篇 |
1994年 | 2717篇 |
1993年 | 2188篇 |
1992年 | 1725篇 |
1991年 | 1250篇 |
1990年 | 1060篇 |
1989年 | 920篇 |
1988年 | 864篇 |
1987年 | 636篇 |
1986年 | 434篇 |
1985年 | 1283篇 |
1984年 | 901篇 |
1983年 | 671篇 |
1982年 | 959篇 |
1981年 | 1109篇 |
1980年 | 996篇 |
1979年 | 888篇 |
1978年 | 792篇 |
1977年 | 669篇 |
1976年 | 647篇 |
1974年 | 419篇 |
1973年 | 565篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
《Annales de l'Institut Henri Poincaré (C) Analyse Non Linéaire》2021,38(5):1337-1371
In this paper we consider minimizers of the functional where is a bounded open set and where are the first k eigenvalues on Ω of an operator in divergence form with Dirichlet boundary condition and with Hölder continuous coefficients. We prove that the optimal sets have finite perimeter and that their free boundary is composed of a regular part, which is locally the graph of a -regular function, and a singular part, which is empty if , discrete if and of Hausdorff dimension at most if , for some . 相似文献
2.
3.
4.
Dr. Joaquim Torra Dr. Felipe Viela Dr. Diego Megías Dr. Begoña Sot Prof. Cristina Flors 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(19):e202200026
CRANAD-2 is a fluorogenic curcumin derivative used for near-infrared detection and imaging in vivo of amyloid aggregates, which are involved in neurodegenerative diseases. We explore the performance of CRANAD-2 in two super-resolution imaging techniques, namely stimulated emission depletion (STED) and single-molecule localization microscopy (SMLM), with markedly different fluorophore requirements. By conveniently adapting the concentration of CRANAD-2, which transiently binds to amyloid fibrils, we show that it performs well in both techniques, achieving a resolution in the range of 45–55 nm. Correlation of SMLM with atomic force microscopy (AFM) validates the resolution of fine features in the reconstructed super-resolved image. The good performance and versatility of CRANAD-2 provides a powerful tool for near-infrared nanoscopic imaging of amyloids in vitro and in vivo. 相似文献
5.
6.
In this work, a vanillin complex is immobilized onto MCM-41 and characterized by FT-IR, X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, thermogravimetric analysis, and BET techniques. This supported Schiff base complex was found to be an efficient and recoverable catalyst for the chemoselective oxidation of sulfides into sulfoxides and thiols into their corresponding disulfides (using hydrogen peroxide as a green oxidant) and also a suitable catalyst for the preparation of 2,3-dihydroquinazolin-4(1H)-one derivatives in water at 90°C. Using this protocol, we show that a variety of disulfides, sulfoxides, and 2,3-dihydroquinazolin-4(1H)-one derivatives can be synthesized in green conditions. The catalyst can be recovered and recycled for further reactions without appreciable loss of catalytic performance. 相似文献
7.
8.
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
9.
Florence Drui Emmanuel Franck Philippe Helluy Laurent Navoret 《Comptes Rendus Mecanique》2019,347(3):259-269
The over-relaxation approach is an alternative to the Jin–Xin relaxation method in order to apply the equilibrium source term in a more precise way. This is also a key ingredient of the lattice Boltzmann method for achieving second-order accuracy. In this work, we provide an analysis of the over-relaxation kinetic scheme. We compute its equivalent equation, which is particularly useful for devising stable boundary conditions for the hidden kinetic variables. 相似文献
10.
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