全文获取类型
收费全文 | 15443篇 |
免费 | 715篇 |
国内免费 | 145篇 |
专业分类
化学 | 10086篇 |
晶体学 | 51篇 |
力学 | 328篇 |
综合类 | 1篇 |
数学 | 2926篇 |
物理学 | 2911篇 |
出版年
2023年 | 141篇 |
2022年 | 290篇 |
2021年 | 347篇 |
2020年 | 419篇 |
2019年 | 496篇 |
2018年 | 379篇 |
2017年 | 291篇 |
2016年 | 597篇 |
2015年 | 564篇 |
2014年 | 551篇 |
2013年 | 917篇 |
2012年 | 1081篇 |
2011年 | 1279篇 |
2010年 | 678篇 |
2009年 | 563篇 |
2008年 | 914篇 |
2007年 | 831篇 |
2006年 | 841篇 |
2005年 | 773篇 |
2004年 | 607篇 |
2003年 | 471篇 |
2002年 | 437篇 |
2001年 | 240篇 |
2000年 | 172篇 |
1999年 | 183篇 |
1998年 | 155篇 |
1997年 | 167篇 |
1996年 | 167篇 |
1995年 | 144篇 |
1994年 | 114篇 |
1993年 | 105篇 |
1992年 | 86篇 |
1991年 | 78篇 |
1990年 | 64篇 |
1989年 | 40篇 |
1988年 | 44篇 |
1987年 | 47篇 |
1986年 | 44篇 |
1985年 | 69篇 |
1984年 | 58篇 |
1983年 | 35篇 |
1982年 | 59篇 |
1981年 | 51篇 |
1980年 | 44篇 |
1979年 | 40篇 |
1978年 | 46篇 |
1977年 | 41篇 |
1976年 | 47篇 |
1974年 | 34篇 |
1973年 | 29篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
22.
Alexander N Shivanyuk Dmitry M Rudkevich David N Reinhoudt 《Tetrahedron letters》1996,37(52):9341-9344
An assembly of cation receptor 1 and anion receptor 2 via the hydrogen bonding melamine-barbiturate structural motif complexes sodium thiocyanate, sodium iodide, and sodium azide in apolar solvents. 相似文献
23.
Dextran-modified iron oxide nanoparticles 总被引:1,自引:0,他引:1
Dextran-modified iron oxide nanoparticles were prepared by precipitation of Fe(Ⅱ) and Fe(Ⅲ) salts with ammonium hydroxide by two methods. Iron oxide was precipitated either in the presence of dextran solution, or the dextran solution was added after precipitation. In the second method, the iron oxide particle size and size distribution could be controlled depending on the concentration of dextran in the solution. The nanoparticles were characterized by size-exclusion chromatography, transmission electron microscopy and dynamic light scattering. Optimal conditions for preparation of stable iron oxide colloid particles were determined, The dextran/iron oxide ratio 0-0,16 used in precipitation of iron salts can be recommended for synthesis of nanoparticles suitable for biomedical applications, as the colloid does not contain excess dextran and does not coagulate. 相似文献
24.
The classical (first integral) methods of studying restrictions on the possible motion of gravitationally interacting bodies are reviewed. The simple and flexible inequality method is extended to a similar approach to the relationship between possible forbidden motion and (asymptotic) symmetries in the relativistic few-body problem. This extended method is used to reproduce the standard results of bounded motion for a test particle in a Schwarzschild geometry. The existence of bounded motion is shown for the general relativistic few-body problem and the difficulties in determining such bounded motion is analysed. The use of this approach to obtaining a relativistic alternative to the classical Roche lobe analysis in contact binaries is discussed. 相似文献
25.
26.
27.
In this work a new reference wave method for solving parabolic-type equations is proposed. The performance of the method is demonstrated by applying it to the equation governing the propagation of the two-frequency mutual coherence function in a random medium. An analytic solution is presented for arbitrary correlation properties of the medium. It is shown that when approximating the transverse structure function of the medium by a quadratic form, the solution reduces to the exact result derived previously. Extensions to more general types of media are considered. 相似文献
28.
Alexey Yurasov Alexander Granovsky Sergey Tarapov Jean-Pierre Clerc 《Journal of magnetism and magnetic materials》2006
The transmission of millimeter-range electromagnetic waves (30–50 GHz) through a magnetic nanocomposite thin film exhibiting tunnel magnetoresistance (TMR) is calculated. The relative change of transmission coefficient in an applied magnetic field due to the magnetorefractive effect is approximately linear with TMR and strongly depends on nanocomposite resistivity and film thickness. The obtained results are in a good agreement with experiment. 相似文献
29.
G.N Hile Alexander Stanoyevitch 《Journal of Mathematical Analysis and Applications》2004,295(2):595-610
We generalize the heat polynomials for the heat equation to more general partial differential equations, of higher order with respect to both the time variable and the space variables. Whereas the heat equation requires only one family of polynomials, for an equation of the ?th order with respect to time we introduce ? families of polynomials. These families correspond to the ? initial conditions specified by the Cauchy problem. 相似文献
30.
We prove that, in Euclidean space, any nonnegatively curved, compact, smoothly immersed hypersurface lies outside the convex hull of its boundary, provided the boundary satisfies certain required conditions. This gives a convex hull property, dual to the classical one for surfaces with nonpositive curvature. A version of this result in the nonsmooth category is obtained as well. We show that our boundary conditions determine the topology of the surface up to at most two choices. The proof is based on uniform estimates for radii of convexity of these surfaces under a clipping procedure, a noncollapsing convergence theorem, and a gluing procedure. 相似文献