全文获取类型
收费全文 | 7584篇 |
免费 | 1853篇 |
国内免费 | 628篇 |
专业分类
化学 | 1494篇 |
晶体学 | 128篇 |
力学 | 1235篇 |
综合类 | 83篇 |
数学 | 1355篇 |
物理学 | 5770篇 |
出版年
2024年 | 15篇 |
2023年 | 56篇 |
2022年 | 105篇 |
2021年 | 93篇 |
2020年 | 184篇 |
2019年 | 166篇 |
2018年 | 152篇 |
2017年 | 211篇 |
2016年 | 233篇 |
2015年 | 201篇 |
2014年 | 444篇 |
2013年 | 523篇 |
2012年 | 430篇 |
2011年 | 583篇 |
2010年 | 478篇 |
2009年 | 584篇 |
2008年 | 592篇 |
2007年 | 576篇 |
2006年 | 575篇 |
2005年 | 465篇 |
2004年 | 444篇 |
2003年 | 391篇 |
2002年 | 348篇 |
2001年 | 318篇 |
2000年 | 276篇 |
1999年 | 222篇 |
1998年 | 175篇 |
1997年 | 181篇 |
1996年 | 126篇 |
1995年 | 132篇 |
1994年 | 95篇 |
1993年 | 93篇 |
1992年 | 91篇 |
1991年 | 70篇 |
1990年 | 59篇 |
1989年 | 50篇 |
1988年 | 40篇 |
1987年 | 41篇 |
1986年 | 30篇 |
1985年 | 26篇 |
1984年 | 30篇 |
1983年 | 13篇 |
1982年 | 23篇 |
1981年 | 19篇 |
1980年 | 18篇 |
1979年 | 22篇 |
1978年 | 9篇 |
1977年 | 14篇 |
1976年 | 10篇 |
1974年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
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
2.
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
3.
4.
Summary This paper is concerned with the problem of developing numerical integration algorithms for differential equations that, when
viewed as equations in some Euclidean space, naturally evolve on some embedded submanifold. It is desired to construct algorithms
whose iterates also evolve on the same manifold. These algorithms can therefore be viewed as integrating ordinary differential
equations on manifolds. The basic method “decouples” the computation of flows on the submanifold from the numerical integration
process. It is shown that two classes of single-step and multistep algorithms can be posed and analyzed theoretically, using
the concept of “freezing” the coefficients of differential operators obtained from the defining vector field. Explicit third-order
algorithms are derived, with additional equations augmenting those of their classical counterparts, obtained from “obstructions”
defined by nonvanishing Lie brackets. 相似文献
5.
针对VO2薄膜在微测辐射热计上的应用,采用射频反应溅射法,在室温下制备氧化钒薄膜;研究了氧分压对薄膜沉积速率、电学性质及成分的影响.通过调节氧分压,先获得成分接近VO2的非晶化薄膜,再在400℃空气中氧化退火,便可制得高电阻温度系数,低电阻率的VO2薄膜,电阻温度系数约为-4%/℃,薄膜方块电阻为R□为100—300kΩ;薄膜在室温下沉积,400℃下退火的制备方法与微机电加工(micro electromechanic
关键词:
二氧化钒
电阻温度系数
氧分压
射频反应溅射法 相似文献
6.
利用室温下压电调制反射光(PzR)谱技术系统测量了N掺杂浓度为0.0%—3%的分子束外延生长GaNxAs1-x薄膜,并对图谱中所观察的光学跃迁进行了指认.在GaN0.005As0.995和GaN0.01As0.99薄膜的PzR谱中观察到此前只在椭圆偏振谱中才看到的N掺杂相关能态E1+Δ1+ΔN.当N掺杂浓度达到
关键词:
压电调制反射光谱(PzR)
xAs1-x薄膜')" href="#">GaNxAs1-x薄膜
分子束外延(MBE) 相似文献
7.
The excitation of eigen surface waves by tubular electron beams in cylindrical discharge devices is studied. The influence of the wave‐field azimuthal structure on the excitation efficiency and nonlinear stage of the plasmabeam instability is investigated both numerically and analytically. Analytical expressions for the saturation amplitude and excitation efficiency of the wave under study are derived. They are found to agree well with results obtained by numerical modelling of the plasma‐beam interaction presented in this paper. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
8.
Ari Sihvola 《Optik》2006,117(7):317-320
A geometric visualization is presented for the Brewster angle for a plane wave reflecting from an interface. The surface is assumed to be isotropic but it is allowed to display both dielectric and magnetic susceptibility, and hence the Brewster (polarizing) angle can attain any value between 0 and 90°, and can exist for both parallel and perpendicular polarizations. The geometric construction (a tetrahedron) is spanned by the basic material parameters of the surface. The Brewster angle appears in one of the faces of the tetrahedron. 相似文献
9.
The revival of the nondiffracting vortex beam after its interaction with the 2D on axis obstacle is examined. We show that the phase topology and the spatial distribution of the orbital angular momentum of the beam transmitted through the obstacle regenerate to the initial form during further free propagation. We verify that the healing effect appears even if the interaction is accompanied by the exchange of the orbital angular momentum. 相似文献
10.
建立了一个四组分一维混合模型,对电子束注入大气产生大尺度等离子体的过程进行了数值模拟.结果表明了能量为140keV、流强为50mA/cm2的注入电子束,可以产生线度为0.5m,密度为1012cm-3量级的大气环境下等离子体.电子束所伴随的空间电荷效应由于等离子体的产生会很快消失,不影响后续的等离子体产生过程.电子束注入流强主要影响产生等离子体的密度,而电子束能量则同时影响其空间线度和密度.
关键词:
电子束
碰撞
电离 相似文献