全文获取类型
收费全文 | 13296篇 |
免费 | 762篇 |
国内免费 | 580篇 |
专业分类
化学 | 8977篇 |
晶体学 | 190篇 |
力学 | 258篇 |
综合类 | 2篇 |
数学 | 262篇 |
物理学 | 4949篇 |
出版年
2024年 | 41篇 |
2023年 | 474篇 |
2022年 | 285篇 |
2021年 | 264篇 |
2020年 | 506篇 |
2019年 | 319篇 |
2018年 | 342篇 |
2017年 | 378篇 |
2016年 | 608篇 |
2015年 | 541篇 |
2014年 | 605篇 |
2013年 | 656篇 |
2012年 | 698篇 |
2011年 | 433篇 |
2010年 | 533篇 |
2009年 | 531篇 |
2008年 | 330篇 |
2007年 | 471篇 |
2006年 | 649篇 |
2005年 | 412篇 |
2004年 | 277篇 |
2003年 | 327篇 |
2002年 | 307篇 |
2001年 | 462篇 |
2000年 | 211篇 |
1999年 | 381篇 |
1998年 | 227篇 |
1997年 | 147篇 |
1996年 | 106篇 |
1995年 | 89篇 |
1994年 | 81篇 |
1993年 | 78篇 |
1992年 | 84篇 |
1991年 | 58篇 |
1990年 | 66篇 |
1989年 | 89篇 |
1988年 | 383篇 |
1987年 | 804篇 |
1986年 | 810篇 |
1985年 | 118篇 |
1984年 | 47篇 |
1983年 | 27篇 |
1982年 | 42篇 |
1981年 | 78篇 |
1980年 | 45篇 |
1979年 | 49篇 |
1978年 | 60篇 |
1977年 | 40篇 |
1976年 | 64篇 |
1973年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 510 毫秒
21.
22.
《Solid State Ionics》2006,177(26-32):2467-2471
AgI nanoparticles were prepared by solution-based routes using water-soluble anionic or cationic polyelectrolytes as capping agents. Depending on the polyelectrolytes, AgI nanoparticles with well-defined morphology, size, and phase compositions were obtained: the use of poly(sodium 4-styrenesulfonate) (PSS) resulted in AgI nano-rods of β-AgI in wurtzite structure (2H); with poly(acrylic acid sodium salt) (PAS) truncated-tetrahedron shaped γ-AgI nanoparticles (nanotetrahedra) in zinc-blende structure (3C) were obtained; by employing poly(diallyldimethylammonium chloride) (PDADMAC) plate-like AgI nanoparticles (nano-plates) consisting of unusual polytype phases of AgI (7H and 9R) were formed. Macroscopically unstable γ-AgI and 7H and 9R phases could be stabilized in the form of nanocrystalline powders. They transform reversibly into the high temperature α-AgI phase and exhibit unusually high ionic conductivity and substantially smaller transformation enthalpy values compared to the macroscopic β-AgI. 相似文献
23.
24.
25.
26.
Pure and Ce4+ doped anatase and rutile TiO2 were prepared by hydrothermal methods and characterized by XRD, TEM, UV-vis diffusion spectroscopy, and XPS measurements. The photocatalytic reactivity of the catalysts was evaluated by the photodegradation of Rhodamine B (RB) under ultraviolet irradiation. The photocatalytic efficiency of the rutile sample doped with an appropriate amount of Ce4+ was enhanced while all Ce4+ doped anatase samples showed a much lower activity than pure anatase. The reasons were discussed 相似文献
27.
《Polyhedron》2007,26(9-11):1849-1858
Three compounds composed of phenazine and copper chloride have been prepared and studied by infrared spectroscopy, X-ray diffraction, and variable temperature magnetization. The compounds synthesized and studied are: Cu(phenazine)Cl2 (1), (phenazinium)2CuCl4 · H2O (2), and [Cu(phenazine)Cl2 · H2O]2 (3). Compounds 1 and 2 are described as antiferromagnetic Heisenberg chains with exchange constants ∣J∣/kB = 33.8 K and 8.6 K, respectively. 相似文献
28.
《ournal of non Newtonian Fluid Mechanics》2007,141(2-3):148-166
This work deals with the development of a numerical method for simulating viscoelastic axisymmetric free surface flow of an Oldroyd B fluid. A novel formulation is developed for the computation of the non-Newtonian extra-stress components on rigid boundaries and on the symmetry axis. The full free surface stress conditions are employed. The resulting governing equations are solved by finite differences on a Marker-and-cell (MAC) type grid. Validation is provided by simulating a pipe flow problem. The classical die-swell problem is solved and swelling ratios are provided. The height of the splash caused by a falling liquid drop for various Reynolds and Weissenberg numbers is then studied, and the height of the splash is shown to diminish with increasing viscoelasticity. 相似文献
29.
《Journal of Electrostatics》2006,64(10):647-654
Ellipsoidal functions and ellipsoidal co-ordinates, naturally adapted to the treatment of potential problems involving ellipsoidal boundaries, are due to a relatively complicated mathematical appearance avoided in the majority of textbooks on electromagnetism, leading to an unjustified ignorance of the whole system. The paper at hand is devoted to showing that the system is worthwhile using and investigating. By first recollecting the key results of the co-ordinate system and the related potential functions, including the indispensable orthogonality result and the reciprocal distance formula, basic potential problems of electrostatics are reviewed. Closed-form expressions are thereupon derived for the induced charge and its centroid in the case of a point charge influencing a grounded ellipsoid. An image source interpretation, generalising the image solution for a sphere, follows easily from these expressions, as well as an approximate expression for the mutual capacitance between two ellipsoids or a parallel disk capacitor. An expression is also given for the total polarisation induced in a dielectric ellipsoid by the influence of a point dipole. 相似文献
30.