全文获取类型
收费全文 | 65295篇 |
免费 | 4458篇 |
国内免费 | 4192篇 |
专业分类
化学 | 21320篇 |
晶体学 | 484篇 |
力学 | 7249篇 |
综合类 | 639篇 |
数学 | 21126篇 |
物理学 | 23127篇 |
出版年
2024年 | 84篇 |
2023年 | 600篇 |
2022年 | 1034篇 |
2021年 | 1228篇 |
2020年 | 1452篇 |
2019年 | 1477篇 |
2018年 | 1341篇 |
2017年 | 1535篇 |
2016年 | 1746篇 |
2015年 | 1416篇 |
2014年 | 2376篇 |
2013年 | 4513篇 |
2012年 | 2677篇 |
2011年 | 3118篇 |
2010年 | 2549篇 |
2009年 | 3821篇 |
2008年 | 4097篇 |
2007年 | 4500篇 |
2006年 | 3696篇 |
2005年 | 3007篇 |
2004年 | 2580篇 |
2003年 | 2788篇 |
2002年 | 3096篇 |
2001年 | 2387篇 |
2000年 | 2307篇 |
1999年 | 1977篇 |
1998年 | 1931篇 |
1997年 | 1225篇 |
1996年 | 1122篇 |
1995年 | 953篇 |
1994年 | 993篇 |
1993年 | 727篇 |
1992年 | 824篇 |
1991年 | 553篇 |
1990年 | 527篇 |
1989年 | 394篇 |
1988年 | 334篇 |
1987年 | 330篇 |
1986年 | 313篇 |
1985年 | 293篇 |
1984年 | 314篇 |
1983年 | 194篇 |
1982年 | 260篇 |
1981年 | 243篇 |
1980年 | 184篇 |
1979年 | 201篇 |
1978年 | 165篇 |
1977年 | 152篇 |
1976年 | 95篇 |
1973年 | 66篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
31.
Recent Progress in the $L_p$ Theory for Elliptic and Parabolic Equations with Discontinuous Coefficients 下载免费PDF全文
Hongjie Dong 《分析论及其应用》2020,36(2):161-199
In this paper, we review some results over the last 10-15 years on elliptic and parabolic equations with discontinuous coefficients. We begin with an approach given by N. V. Krylov to parabolic equations in the whole space with $\rm{VMO}_x$ coefficients. We then discuss some subsequent development including elliptic and parabolic equations with coefficients which are allowed to be merely measurable in one or two space directions, weighted $L_p$estimates with Muckenhoupt ($A_p$) weights, non-local elliptic and parabolic equations, as well as fully nonlinear elliptic and parabolic equations. 相似文献
32.
33.
Jerry Ray Dias 《Molecular physics》2020,118(12)
Cycloparaphenylene ([r]CPP) and cyclacene ([r]CA) series are models for short carbon nanotubes. It is shown that armchair edges in model cycloparaphenylenes possess greater aromaticity and cyclic conjugation than do zigzag edges in model cyclacenes. According to Aihara’s bond resonance energy (BRE) and Bosanac and Gutman energy effect (ef) measurements, cycloparaphenylenes are twice as aromatic as cyclacenes. The general solution of all eigenvalues of all members of the cycloparaphenylene series is given. The origin of the recurrence of some eigenvalues are determined. 相似文献
34.
35.
Gas-phase 21Ne nuclear magnetic resonance spectra were measured at the natural abundance of 21Ne isotope for samples consisting of pressurized neon up to 60 bar at room temperature and applying the magnetic field of the strength B0 = 11.7574 T. It showed that the nuclear magnetic resonance frequency is linearly dependent on the density of gaseous neon. The resonance frequency was extrapolated to the zero-density point, and it permitted the determination of the 21Ne nuclear magnetic moment, μ(21Ne) = 0.6617774(10) μN. The present value of μ(21Ne) is not influenced by the bulk magnetic susceptibility of neon and interactions between neon atoms; therefore, it is more precise and reliable than the previous result obtained for μ(21Ne). 相似文献
36.
37.
Galia Pozina Elizaveta I. Girshova Konstantin M. Morozov Konstantin A. Ivanov Anton Yu. Egorov Mikhail A. Kaliteevski 《Annalen der Physik》2019,531(6)
Enhancement of spontaneous emission in a resonant Bragg quantum well (QW) structure with 60 periods of triple InAs monolayers embedded in a GaAs matrix is studied experimentally and theoretically. From measurements of the time‐resolved photoluminescence, besides the QW exciton at 1.47 eV, a specific super‐radiant (SR) emission demonstrating nonlinear properties is found. The SR mode shows a near‐quadratic dependence of intensity on excitation power, while its energy position follows the Bragg condition. It is revealed that the SR mode shows a peculiar non‐monotonic dependence of intensity on direction, with a maximum observed at approximately 40°. The enhancement in the SR emission at a specific direction is correlated well with suggested theoretical consideration of the modal Purcell factor for periodic quantum well structures. 相似文献
38.
《Annales de l'Institut Henri Poincaré (C) Analyse Non Linéaire》2020,37(2):417-456
We study the energy-critical nonlinear wave equation in the presence of an inverse-square potential in dimensions three and four. In the defocussing case, we prove that arbitrary initial data in the energy space lead to global solutions that scatter. In the focusing case, we prove scattering below the ground state threshold. 相似文献
39.
Activated carbon production from almond shells using phosphoric acid activation agent was achieved by applying both conventional heating and microwave heating in succession. The morphology and surface properties of activated carbon were studied using thermogravimetric and differential gravimetric analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy, and Brunauer–Emmett–Teller analysis. A surface area of 1128 m2/g was achieved by optimizing the microwave power (500?W), microwave application time (15?minutes), conventional heating time (45?minutes), conventional heating temperature (500?°C), and the phosphoric acid:sample ratio (0.7:1). An adsorption capacity of methylene blue of 148?mg/g and an iodine value of 791?mg/g was obtained for the prepared activated carbon. 相似文献
40.
In this paper, we consider a viscoelastic wave equation of variable coefficients in the presence of past history with nonlinear damping and delay in the internal feedback and dynamic boundary conditions. Under suitable assumptions, we establish an explicit and general decay rate result without imposing restrictive assumption on the behavior of the relaxation function at infinity by Riemannian geometry method and Lyapunov functional method. 相似文献