全文获取类型
收费全文 | 215057篇 |
免费 | 2042篇 |
国内免费 | 476篇 |
专业分类
化学 | 113948篇 |
晶体学 | 3472篇 |
力学 | 10450篇 |
综合类 | 10篇 |
数学 | 23506篇 |
物理学 | 66189篇 |
出版年
2021年 | 2324篇 |
2020年 | 2310篇 |
2019年 | 2831篇 |
2018年 | 3922篇 |
2017年 | 3909篇 |
2016年 | 5274篇 |
2015年 | 2762篇 |
2014年 | 4743篇 |
2013年 | 9400篇 |
2012年 | 7713篇 |
2011年 | 8986篇 |
2010年 | 7068篇 |
2009年 | 7263篇 |
2008年 | 8458篇 |
2007年 | 8363篇 |
2006年 | 7344篇 |
2005年 | 6538篇 |
2004年 | 6125篇 |
2003年 | 5564篇 |
2002年 | 5528篇 |
2001年 | 5802篇 |
2000年 | 4323篇 |
1999年 | 3258篇 |
1998年 | 2817篇 |
1997年 | 2872篇 |
1996年 | 2676篇 |
1995年 | 2300篇 |
1994年 | 2409篇 |
1993年 | 2293篇 |
1992年 | 2593篇 |
1991年 | 2707篇 |
1990年 | 2596篇 |
1989年 | 2657篇 |
1988年 | 2557篇 |
1987年 | 2582篇 |
1986年 | 2440篇 |
1985年 | 3076篇 |
1984年 | 3137篇 |
1983年 | 2619篇 |
1982年 | 2592篇 |
1981年 | 2549篇 |
1980年 | 2355篇 |
1979年 | 2720篇 |
1978年 | 2685篇 |
1977年 | 2881篇 |
1976年 | 2876篇 |
1975年 | 2673篇 |
1974年 | 2608篇 |
1973年 | 2722篇 |
1972年 | 2088篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
181.
E. N. Yurchenko G. E. Kramareva N. G. Zubritskaya T. P. Gaidei 《Reaction Kinetics and Catalysis Letters》1995,55(2):425-432
In the Russian Scientific Center Applied Chemistry catalysts have been developed for the gas-phase fluorination of organics, including chlorine-containing substances, hydrogenation and reductive amination of organic substances, decomposition of liquid substances to gases, complete oxidation and reduction, suitable for environment at protection. 相似文献
182.
We investigate the replica symmetry breaking (RSB) in a neighborhood of the instability point of the replica-symmetric solution in the axial quadrupolar glass model. We show that the solution with the first-stage RSB is stable against the subsequent RSB. Although there is no reflection symmetry, the first-stage RSB solution continuously bifurcates from the replica-symmetric one. This implies that our model does not belong to either of the two classes into which spin glasses are usually divided. 相似文献
183.
A forecasting model is developed for the number of daily applications for loans at a financial services telephone call centre. The purpose of the forecasts and the associated prediction intervals is to provide effective staffing policies within the call centre. The model building process is constrained by the availability of only 2 years and 7 months of data. The distinctive feature of the data is that demand is driven in the main by advertising. The analysis given focuses on applications stimulated by press advertising. Unlike previous analyses of broadly similar data, where ARIMA models were used, a model with a dynamic level, multiplicative calendar effects and a multiplicative advertising response is developed and shown to be effective. 相似文献
184.
185.
186.
187.
Experimental and theoretical research into electric generators of singlet delta oxygen (SDO) for an oxygen-iodine laser made
at the Lebedev Physics Institute and TRINITI is discussed. Breakdown and current-voltage characteristics of self-sustained
electric discharge in SDO were studied both experimentally and theoretically, indicating that SDO and pure oxygen have quite
different electric features. The electric properties and spectroscopy of an e-beam sustained discharge (EBSD) in oxygen and oxygen gas mixtures were experimentally studied. A comprehensive numerical
model describing SDO kinetics in different kinds of discharge was developed. The pulsed EBSD in pure oxygen and its mixtures
with noble gases was shown to be very unstable and characterized by low input energy. When adding small amounts of carbon
monoxide or hydrogen, the electric stability of the EBSD increases, the specific input energy (SIE) per molecular component
being more than order of magnitude higher and coming to 6.5 kJ/(l atm(O2 + CO)) for the gas mixture O2: Ar: CO = 1: 1: 0.1. Theoretical calculations demonstrated that, for an SIE of 6.5 kJ/(l atm), the SDO yield may reach ∼20%,
exceeding its threshold value needed for oxygen-iodine laser operation at room temperature. The calibration of the optical
scheme for measuring the SDO absolute concentration and yield using the detection of luminescence of the SDO going from a
chemical SDO generator was performed. The measurement of the SDO yield demonstrated that it was ∼10.5% for an SIE of ∼3.0
kJ/(l atm(O2 + CO)), which is about 1.5 times less than the results of theoretical calculations for such an SIE. SDO production
in RF slab discharge ignited in oxygen gas mixtures was experimentally studied, experimental SDO yield being about 10%. The
choice of electrode material was demonstrated to be very important.
Original Text ? Astro, Ltd., 2006. 相似文献
188.
D. N. Zaporozhets 《Journal of Mathematical Sciences》2006,137(1):4525-4530
In this note, we find the distibution of the number of real zeros of a random polynomial. We also derive a formula for the
expected number of complex zeros lying in a given domain of the complex plane. Bibliography: 7 titles.
__________
Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 320, 2004, pp. 69–79. 相似文献
189.
The main result of the paper is a theorem, using which a new proof of Roth’s theorem is obtained, a new solvability criterion
for the matrix equation AX-YB = C is proved, a formula for a particular solution of the latter is derived, and the least of
the orders of square nonsingular matrices containing a given rectangular matrix as a submatrix is determined. Bibliography:
5 titles.
__________
Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 323, 2005, pp. 15–23. 相似文献
190.
I. N. Sergeev 《Journal of Mathematical Sciences》2006,135(1):2764-2793
The definition of the characteristic frequencies of zeroes and changes of sign for solutions is given. It is equal to the
upper medium (with respect to the time half-axis) of their number on the half-interval of length π. We also define the main frequencies for a linear homogeneous equation of order n. These main frequencies for an equation with constant coefficients coincide with the absolute values of the imaginary parts
of the roots of the corresponding characteristic polynomial. It is proved that for the second-order equation the main frequencies
are the same for all solutions and that they are stable with respect to uniformly small and infinitely small perturbations
of the coefficients. For the third-order equation they can be different, and for any of the main frequencies an example of
nonstability is given.
__________
Translated from Trudy Seminara imeni I. G. Petrovskogo, No. 25, pp. 249–294, 2005. 相似文献