全文获取类型
收费全文 | 47877篇 |
免费 | 2082篇 |
国内免费 | 1531篇 |
专业分类
化学 | 25956篇 |
晶体学 | 784篇 |
力学 | 2459篇 |
综合类 | 97篇 |
数学 | 4975篇 |
物理学 | 17219篇 |
出版年
2022年 | 473篇 |
2021年 | 619篇 |
2020年 | 697篇 |
2019年 | 656篇 |
2018年 | 818篇 |
2017年 | 735篇 |
2016年 | 1144篇 |
2015年 | 828篇 |
2014年 | 1259篇 |
2013年 | 2364篇 |
2012年 | 2332篇 |
2011年 | 2773篇 |
2010年 | 1960篇 |
2009年 | 2022篇 |
2008年 | 2247篇 |
2007年 | 2201篇 |
2006年 | 2042篇 |
2005年 | 1787篇 |
2004年 | 1601篇 |
2003年 | 1363篇 |
2002年 | 1269篇 |
2001年 | 1651篇 |
2000年 | 1239篇 |
1999年 | 1106篇 |
1998年 | 929篇 |
1997年 | 839篇 |
1996年 | 767篇 |
1995年 | 692篇 |
1994年 | 679篇 |
1993年 | 548篇 |
1992年 | 610篇 |
1991年 | 597篇 |
1990年 | 593篇 |
1989年 | 503篇 |
1988年 | 524篇 |
1987年 | 512篇 |
1986年 | 456篇 |
1985年 | 510篇 |
1984年 | 518篇 |
1983年 | 376篇 |
1982年 | 420篇 |
1981年 | 402篇 |
1980年 | 338篇 |
1979年 | 409篇 |
1978年 | 389篇 |
1977年 | 400篇 |
1976年 | 397篇 |
1975年 | 346篇 |
1974年 | 318篇 |
1973年 | 343篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
42.
Z. Slanina 《Journal of Radioanalytical and Nuclear Chemistry》1987,111(1):43-49
A search for conditions leading to the highest possible difference between equilibrium association (clustering) degree in the H and D steam has been carried out and related optimal steam pressures evaluated. The difference decreases with increasing temperature but still is a few per cent at moderate temperatures. 相似文献
43.
Supposa that f(x) is a quasidifferentiable function, defined on S(?)R~n where S is an open set, with a -equivalent bounded quasidifferential subfam ily. Lenma I 相似文献
44.
A profit-maximizing supply chain network design model with demand choice flexibility 总被引:1,自引:0,他引:1
Zuo-Jun Max Shen 《Operations Research Letters》2006,34(6):673-682
We present a profit-maximizing supply chain design model in which a company has flexibility in determining which customers to serve. The company may lose a customer to competition if the price it charges is too high. We show the problem formulation and solution algorithm, and discuss computational results. 相似文献
45.
Wei Gengping~ Shen Jianhua~ 《高校应用数学学报(英文版)》2006,21(3):320-326
This paper studies the nonautonomous nonlinear system of difference equationsΔx(n)=A(n)x(n)+f(n,x(n)),n∈Z,(*) where x(n)∈R~N,A(n)=(a_(ij)(n))N×N is an N×N matrix,with a-(ij)∈C(R,R) for i,j= 1,2,3,...,N,and f=(f_1,f_2,...,f_N)~T∈C(R×R~N,R~N),satisfying A(t+ω)=A(t),f(t+ω,z)=f(t,z) for any t∈R,(t,z)∈R×R~N andωis a positive integer.Sufficient conditions for the existence ofω-periodic solutions to equations (*) are obtained. 相似文献
46.
In the study of the behaviors of barriers in an enclosed field, one should take into account such phenomena as sound energy reflection, absorption, scattering and diffraction. Therefore, the study is much more difficult than that in free field. In this paper, sound barriers are classified into four kinds according to their size, number and shape. Each kind of barriers is modelled by a corresponding method based on a computer program—SOFIS. The program combines the ray-tracing technique and statistical method. The impulse response and some acoustical parameters such as sound pressure level at different positions can be calculated by the program, no matter there are a certain kind of barriers in the field or the field is empty. The ray-tracing program and the algorithms for various barriers are validated by the comparison between measurement and prediction of the reverberation room and the anechoic room of the Northwestern Polytechnic University. 相似文献
47.
Exact closed-form solutions are exhibited for the Hopf equation for stationary incompressible 3D Navier-Stokes flow, for the cases of homogeneous forced flow (including a solution with depleted nonlinearity) and inhomogeneous flow with arbitrary boundary conditions. This provides an exact method for computing two- and higher-point moments, given the mean flow. 相似文献
48.
许多实验对用CsI(Tl)闪烁晶体作为探测器来寻找和探测暗物质的可行性进行了研究.本工作利用8MeV单能中子轰击CsI(Tl)晶体探测器来研究Cs核和I核的QuenchingFactor.在数据处理中,运用脉冲形状甄别(PSD)方法来分辨反冲核信号和本底信号.实验结果表明,在7keV到132keV的能区中,Quench ingFactor随着反冲核能量的减少而增加.在探测暗物质的实验中,这一性质对于CsI(Tl)晶体探测器获得较低的能量阈值是很有利的. 相似文献
49.
F. Chen L. Liu Z. Shen G.Q. Xu T.S.A. Hor 《Applied Physics A: Materials Science & Processing》2002,74(2):317-319
Free-standing and supported hydrogenated amorphous carbon films (a:C–H) were prepared upon pyrolysis of the polymer formed
by ethanolamine (EA) and citric acid (CA), under an ambient atmosphere at 300 °C. EA facilitates the formation of the macroscopic
films, while CA is essential for obtaining the a:C–H microstructure, which comprises a mixture of sp2 and sp3 carbon.
Received: 29 May 2001 / Accepted: 17 August 2001 / Published online: 20 December 2001 相似文献
50.
加肋圆柱壳在轴压作用下的屈曲和后屈曲 总被引:2,自引:2,他引:0
本文讨论完善和非完善的,纵向加肋和正交加肋圆柱壳在轴压作用下的屈曲和后屈曲性态.依据文[1]提供的圆柱薄壳屈曲的边界层理论及其分析方法,给出了加肋圆柱壳在轴压作用下的屈曲和后屈曲理论分析.本文同时讨论肋骨与壳板材料不同时对加肋圆柱壳屈曲和后屈曲性态的影响. 相似文献