全文获取类型
收费全文 | 114828篇 |
免费 | 3788篇 |
国内免费 | 2362篇 |
专业分类
化学 | 50173篇 |
晶体学 | 1194篇 |
力学 | 8095篇 |
综合类 | 97篇 |
数学 | 35139篇 |
物理学 | 26280篇 |
出版年
2024年 | 69篇 |
2023年 | 417篇 |
2022年 | 930篇 |
2021年 | 1112篇 |
2020年 | 1075篇 |
2019年 | 1062篇 |
2018年 | 11147篇 |
2017年 | 10860篇 |
2016年 | 7350篇 |
2015年 | 2105篇 |
2014年 | 1953篇 |
2013年 | 2879篇 |
2012年 | 6754篇 |
2011年 | 13480篇 |
2010年 | 7641篇 |
2009年 | 7879篇 |
2008年 | 9064篇 |
2007年 | 10927篇 |
2006年 | 2464篇 |
2005年 | 3216篇 |
2004年 | 3158篇 |
2003年 | 3364篇 |
2002年 | 2388篇 |
2001年 | 1167篇 |
2000年 | 1053篇 |
1999年 | 781篇 |
1998年 | 641篇 |
1997年 | 559篇 |
1996年 | 659篇 |
1995年 | 462篇 |
1994年 | 416篇 |
1993年 | 400篇 |
1992年 | 311篇 |
1991年 | 290篇 |
1990年 | 243篇 |
1989年 | 218篇 |
1988年 | 164篇 |
1987年 | 159篇 |
1986年 | 141篇 |
1985年 | 154篇 |
1984年 | 114篇 |
1983年 | 95篇 |
1982年 | 118篇 |
1981年 | 113篇 |
1980年 | 87篇 |
1979年 | 93篇 |
1978年 | 81篇 |
1976年 | 57篇 |
1975年 | 54篇 |
1973年 | 64篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
42.
43.
Geometriae Dedicata - We show that an Anosov map has a geodesic axis on the curve graph of the torus. The direct corollary of our result is the stable translation length of an Anosov map on the... 相似文献
44.
45.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films
were investigated using a number of techniques. A high saturation magnetic induction up to B
s
= 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed,
which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of
the composition.
The text was submitted by the authors in English. 相似文献
46.
Dong Zheng Fu-Quan Wang Yuan-Guang Li Liang-Hong Guo Jing Cheng 《Analytica chimica acta》2004,508(2):225-231
Optimized combination of chemical agents was selected for sensitive electrochemical detection of dissolved ruthenium tris-(2,2′-bipyridine) (Ru-bipy). The detection was based on the chemical amplification mechanism, in which the anodic current of a redox-active analyte was amplified by a sacrificial electron donor in solution. On indium-doped tin oxide (ITO) electrodes, electrochemical reaction of the analyte was reversible, but that of the electron donor was greatly suppressed. Several transition metal complexes, such as ferrocene and tris-(2,2′-bipyridine) complexes of osmium, iron and ruthenium, were evaluated as model analyte. A correlation between the amplified current and the standard potential of the complex was observed, and Ru-bipy generated the largest current. A variety of organic bases, acids and zwitterions were assessed as potential electron donor. Sodium oxalate was found to produce the largest amplification factor. With Ru-bipy as the model analyte and oxalate as the electron donor, the analyte concentration curve was linear up to 50 μM, with a lower detection limit of approximately 50 nM. Preliminary work was presented in which a Ru-bipy derivative was attached to bovine serum albumin and detected electrochemically. Although the combination of Ru-bipy, oxalate and ITO electrode has been used before for electrochemiluminescent detection of Ru-bipy and oxalate, as well as electrochemical detection of oxalate, its utility in amplified voltammetric detection of Ru-bipy as a potential electrochemical label has not been reported previously. 相似文献
47.
48.
The barotropic compressible Navier–Stokes equations in an unbounded domain are studied. We prove the unique existence of the solution (u, p) of the system (1.1) in the Sobolev spaceHk + 3 × Hk + 2provided that the derivatives of the data of the problem are sufficiently small, wherek ≥ 0 is any integer. The proof follows from an analysis of the linearized problem, the solvability of the continuity equation, and the Schauder fixed point theory. Similar smoothness results are obtained for a linearized form of (1.1). 相似文献
49.
Uhm H.S. Lee P.H. Kim Y.I. Kim J.H. Chang H.Y. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1995,23(4):628-635
A theory is developed for the density profile of low temperature plasmas confined by applied magnetic field and an experiment of the electron-cyclotron-resonance (ECR) plasma is conducted to compare the theoretical prediction and experimental measurements. Due to a large electron mobility along the magnetic field, electrons move quickly out of the system, leaving ions behind and building a space charge potential, which leads to the ambipolar diffusion of ions. In a steady-state condition, the plasma generation by ionization of neutral molecules is in balance with plasma loss due to the diffusion, leading to the electron temperature equation, which is expressed in terms of the plasma size, chamber pressure, and the ionization energy and cross section of neutrals. The power balance condition leads to the plasma density equation, which is also expressed in terms of the electron temperature, the input microwave power and the chamber pressure. It is shown that the plasma density increases, reaches its peak and decreases, as the chamber pressure increases from a small value (0.1 mTorr). These simple expressions of electron temperature and density provide a scaling law of ECR plasma in terms of system parameters. After carrying out an experimental observation, it is concluded that the theoretical predictions of the electron temperature and plasma density agree remarkably well with experimental data 相似文献
50.