全文获取类型
收费全文 | 26745篇 |
免费 | 5865篇 |
国内免费 | 3345篇 |
专业分类
化学 | 8818篇 |
晶体学 | 326篇 |
力学 | 2224篇 |
综合类 | 296篇 |
数学 | 3497篇 |
物理学 | 20794篇 |
出版年
2024年 | 48篇 |
2023年 | 275篇 |
2022年 | 574篇 |
2021年 | 697篇 |
2020年 | 825篇 |
2019年 | 616篇 |
2018年 | 662篇 |
2017年 | 828篇 |
2016年 | 1008篇 |
2015年 | 993篇 |
2014年 | 1449篇 |
2013年 | 2450篇 |
2012年 | 1633篇 |
2011年 | 1961篇 |
2010年 | 1721篇 |
2009年 | 1893篇 |
2008年 | 1931篇 |
2007年 | 1882篇 |
2006年 | 1785篇 |
2005年 | 1631篇 |
2004年 | 1412篇 |
2003年 | 1325篇 |
2002年 | 1233篇 |
2001年 | 959篇 |
2000年 | 937篇 |
1999年 | 811篇 |
1998年 | 720篇 |
1997年 | 572篇 |
1996年 | 500篇 |
1995年 | 365篇 |
1994年 | 355篇 |
1993年 | 295篇 |
1992年 | 264篇 |
1991年 | 213篇 |
1990年 | 158篇 |
1989年 | 184篇 |
1988年 | 113篇 |
1987年 | 105篇 |
1986年 | 90篇 |
1985年 | 101篇 |
1984年 | 63篇 |
1983年 | 37篇 |
1982年 | 69篇 |
1981年 | 41篇 |
1980年 | 31篇 |
1979年 | 30篇 |
1978年 | 19篇 |
1977年 | 19篇 |
1976年 | 17篇 |
1973年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
92.
93.
有效二能级原子与压缩相干光场相互作用过程中场熵的特性 总被引:4,自引:3,他引:1
本文研究了包括Stark效应时,双光子Jaynes-Cummings模型与单模压缩相干光场发生相互作用过程中场熵的特性,讨论了Stark移动参数、光场参数对场墒演化的影响. 相似文献
94.
95.
Changes in thin zinc-sulfide films under the action of the γ-radiation of Co60 are studied by investigating electroluminescence spectra of terbium embedded in these films as a luminescent probe. It is
shown that changes in the relation of the intensities of bands, a decrease in their halfwidth and the background component,
and simplification of the spectrum are observed in a short-wave region of the Tb radiation spectrum that corresponds to5D3→7Fj transitions. The same modification of the radiation spectrum is characteristic of ZnS films whose crystalline structure is
ordered in the course of thermal annealing at a temperature of 350°C. Based on the analysis of the data obtained it is inferred
that irradiating the ZnS films with small radiation doses of 104–105 rad leads to the ordering of their crystalline structure due to the elimination of one of the types of structural defects.
Institute of Physics of Semiconductors, National Academy of Sciences of Ukraine, 45, Nauka Ave., Kiev-28, 252650. Translated
from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 3, pp. 338–341, May–June, 1997. 相似文献
96.
A. P. Prishivalko 《Journal of Applied Spectroscopy》1997,64(1):94-100
A method for finding the optimum sizes of pigment particles, their volume concentration, and the paint coating thickness that
provide the covering power and the required coloristic characteristics of reflected light for the minimum flow rate of pigments
is based on using a four-flow approximation of the solution to the equation of radiation transfer in dispersion media and
is extended to coatings of complex composition. The capabilities of the method are demonstrated by examples of coatings of
mixtures of hematite and rutile particles in a binder with n=1.5 for variations of the modal size and the half-width of the
size distribution of the pigment particles.
B. I. Stepanov Institute of Physics, Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated
from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 90–96, January–February, 1997. 相似文献
97.
A highly sensitive method for infrared radiation detection based on thermal resonance in an active bolometer is set forth. An active bolometer is a self-oscillating system consisting of an IR-sensitive cell in a feedback circuit of an adjustable proportional controller. The analysis of an active bolometer autonomous (dark) dynamics reveals that with a generalized gain factor A variation the system evolves from relaxation type towards oscillating and self-oscillating type. When A=Ac, where Ac is a critical value of the generalized gain factor A, the steady state loses stability through self-excited thermal oscillations. The resonance in a system weakly perturbed by IR radiation modulated at self-oscillation frequency q0[1+exp(iωct)] is considered. It is shown that in a small precritical vicinity =(A−Ac)/Ac of the gain factor the amplitude of forced thermal oscillations is proportional to q0/Ac. The D* calculation reveals that the detection power of a passive (A=0) bolometer increases with feedback introduction by a factor of 1/||. The detection powers of feasible versions of an active bolometer are compared. 相似文献
98.
与q形变玻色算符逆算符相关的相干态及其量子统计性质 总被引:1,自引:1,他引:0
讨论了q形变玻色算符的广义逆算符作用于q-相干态所得到的两类量子态的数学及量子统计性质。结果表明,q-相干态的光子激发态不存在压缩但呈现反聚束效应,而q-相干态的光子湮灭态却存在压缩但不呈现反聚束效应。 相似文献
99.
具有奇异值分解性质的代数 总被引:4,自引:0,他引:4
设F为一个域,R为一个带有对合的F-代数,如果R上每一个矩阵都有奇异值分解(简称SVD),则称R为一个有SVD性质的F-代数.本文指出:R为一个有SVD性质的F-代数的充要条件是:R同构于R~+,或R~+上二次扩域,或R~+上四元数体((-1,-1)/R~+),其中R~+为R的对称元集合,并且R~+为一个Galois序闭域. 相似文献
100.
A new scheme for controlling photodissociation through preparation of a variationally optimized linear superposition of field free vibrational eigenstates is applied for selective control of IBr and HI dissociation. The dependence of photodissociation on various field parameters and initial conditions is examined to investigate the mechanistic basis of selective control. The parametric equations of motion approach for determining vibrational dynamics as a function of field parameters without having to solve the time dependent Schrödinger equation explicitly for each field parameter separately is outlined and its use to identify field characteristics which will provide the requisite population mix represented by the optimal linear superposition of vibrational states is advocated. 相似文献