全文获取类型
收费全文 | 5548篇 |
免费 | 1093篇 |
国内免费 | 564篇 |
专业分类
化学 | 1374篇 |
晶体学 | 129篇 |
力学 | 406篇 |
综合类 | 67篇 |
数学 | 2016篇 |
物理学 | 3213篇 |
出版年
2024年 | 10篇 |
2023年 | 77篇 |
2022年 | 114篇 |
2021年 | 147篇 |
2020年 | 167篇 |
2019年 | 177篇 |
2018年 | 205篇 |
2017年 | 237篇 |
2016年 | 255篇 |
2015年 | 177篇 |
2014年 | 327篇 |
2013年 | 559篇 |
2012年 | 324篇 |
2011年 | 346篇 |
2010年 | 306篇 |
2009年 | 347篇 |
2008年 | 381篇 |
2007年 | 354篇 |
2006年 | 322篇 |
2005年 | 309篇 |
2004年 | 281篇 |
2003年 | 249篇 |
2002年 | 227篇 |
2001年 | 185篇 |
2000年 | 171篇 |
1999年 | 143篇 |
1998年 | 135篇 |
1997年 | 109篇 |
1996年 | 102篇 |
1995年 | 79篇 |
1994年 | 67篇 |
1993年 | 43篇 |
1992年 | 42篇 |
1991年 | 25篇 |
1990年 | 27篇 |
1989年 | 35篇 |
1988年 | 26篇 |
1987年 | 16篇 |
1986年 | 17篇 |
1985年 | 14篇 |
1984年 | 13篇 |
1983年 | 5篇 |
1982年 | 16篇 |
1981年 | 11篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 4篇 |
排序方式: 共有7205条查询结果,搜索用时 15 毫秒
11.
研制了一种适用于平行板传输连接的平面火花隙三电极开关,开关正负电极为半圆形状,触发电极为细条状。将之替代立体式(半球形电极)火花隙三电极开关并应用于爆炸箔起爆装置中,装置回路参数将得以优化。实验测试了空气间隙为4.12, 3.14和2.2 mm的平面火花隙三电极开关的性能。结果表明,在开关间隙间距一定的情况下,随着电压的升高,开关间隙的放电时延和分散时间呈指数降低,开关电感小于15 nH;对于不同范围内的应用电压,使用不同间隙间距的开关,其分散时间不大于10 ns。该开关应用于较低充电电压(小于10 kV)的脉冲功率装置中,与立体式火花隙三电极开关相比,回路电感降低了约50 nH,放电周期缩短近1/3,峰值电流增加约1/3。 相似文献
12.
Daniel B. Szyld 《Numerical Algorithms》2006,42(3-4):309-323
Given an oblique projector P on a Hilbert space, i.e., an operator satisfying P
2=P, which is neither null nor the identity, it holds that ||P|| = ||I –P||. This useful equality, while not widely-known, has been proven repeatedly in the literature. Many published proofs are reviewed, and simpler ones are presented. 相似文献
13.
A. V. Semykin I. A. Kazarinov E. A. Khomskaya 《Russian Journal of Electrochemistry》2006,42(6):643-648
The hydrogen ionization process is studied experimentally on an industrial sintered nickel oxide electrode in models of sealed nickel-metal hydride batteries. It is shown that the hydrogen ionization rates that are reached during overcharge by high current densities in conditions of forced gas delivery into the electrode pores (up to 40 mA cm?2) exceed the self-discharge rate of a nickel-hydrogen battery by two orders of magnitude. Up to 70% of hydrogen delivered into the compact assembly block undergoes ionization during forced charge of models of sealed nickel-metal hydride batteries with a closed hydrogen cycle. Two independent methods (potentiostatic and manometric) are used to determine the relationship between rates of hydrogen ionization with the degree of the electrode filling with gas and perform estimation of the process intensity at a unit reaction surface. It is established that, in conditions of forced gas delivery, practically all the hydrogen oxidation current is generated at the surface of the nickel oxide electrode beneath thin films of an electrolyte solution at the rate of 4–5 mA cm?2. It is shown that the hydrogen oxidation rate on a nickel oxide electrode filled in part by gas is independent of the electrode potential, probably because of a tangible contribution made by diffusion limitations to the overall hampering of the process. 相似文献
14.
Yu. V. Brezhnev 《Theoretical and Mathematical Physics》2002,133(3):1657-1662
We construct Dubrovin equations and trace formulas for finite-band operators with trigonal curves and present some examples. 相似文献
15.
本文对任意正整数n界定了矩阵方程X A*X-nA=I的正定解的特征值的范围,给出了它的极大正定解一个充分条件. 相似文献
16.
17.
18.
用经验赝势方法计算了体ZnSe以及ZnSe/GaAs单异质结系统中ZnSe外延层г、X、L等特殊对称点导带底能量随压力的变化。结果表明,同Si、Ge、GaAs等半导体材料不同,ZnSe的X点导带底具有正的压力系数,但比г点的压力系数小,这是ZnSe材料以及ZnSe基异质结构材料发生直接禁带向间接禁带的转变时所需转变压力较大的根本原因。研究了ZnSe/GaAs异质结构中晶格失配造成的应变对外延层г、X、L对称点压力系数的影响,表明这种晶格失配造成的应变可以极大地减小ZnSe外延层材料由直接禁带向间接禁带的转变压力。 相似文献
19.
20.
During the course of our investigation of the electron transfer properties of some redox species through highly hydrophobic
long chain alkanethiol molecules on gold in aqueous and non-aqueous solvents, we obtained some intriguing results such as
unusually low interfacial capacitance, very high values of impedance and film resistance, all of which pointed to the possible
existence of a nanometer size interfacial gap between the hydrophobic monolayer and aqueous electrolyte. We explain this phenomenon
by a model for the alkanethiol monolayer—aqueous electrolyte interface, in which the extremely hydrophobic alkanethiol film
repels water molecules adjacent to it and in the process creates a shield between the monolayer film and water. This effectively
increases the overall thickness of the dielectric layer that is manifested as an abnormally low value of interfacial capacitance.
This behaviour is very much akin to the ‘drying transition’ proposed by Lum, Chandler and Weeks in their theory of length
scale dependent hydrophobicity. For small hydrophobic units consisting of apolar solutes, the water molecules can reorganize
around them without sacrificing their hydrogen bonds. Since for an extended hydrophobic unit, the existence of hydrogen bonded
water structure close to it is geometrically unfavourable, there is a net depletion of water molecules in the vicinity leading
to the possible creation of a hydrophobic interfacial gap. 相似文献