全文获取类型
收费全文 | 37795篇 |
免费 | 2788篇 |
国内免费 | 3278篇 |
专业分类
化学 | 2295篇 |
晶体学 | 30篇 |
力学 | 1750篇 |
综合类 | 507篇 |
数学 | 13751篇 |
物理学 | 6104篇 |
综合类 | 19424篇 |
出版年
2024年 | 59篇 |
2023年 | 239篇 |
2022年 | 441篇 |
2021年 | 509篇 |
2020年 | 574篇 |
2019年 | 605篇 |
2018年 | 605篇 |
2017年 | 767篇 |
2016年 | 885篇 |
2015年 | 858篇 |
2014年 | 1678篇 |
2013年 | 1844篇 |
2012年 | 1860篇 |
2011年 | 2268篇 |
2010年 | 1874篇 |
2009年 | 2399篇 |
2008年 | 2297篇 |
2007年 | 2849篇 |
2006年 | 2564篇 |
2005年 | 2298篇 |
2004年 | 2032篇 |
2003年 | 1801篇 |
2002年 | 1558篇 |
2001年 | 1462篇 |
2000年 | 1274篇 |
1999年 | 1068篇 |
1998年 | 1011篇 |
1997年 | 910篇 |
1996年 | 755篇 |
1995年 | 640篇 |
1994年 | 604篇 |
1993年 | 480篇 |
1992年 | 463篇 |
1991年 | 410篇 |
1990年 | 394篇 |
1989年 | 329篇 |
1988年 | 273篇 |
1987年 | 214篇 |
1986年 | 132篇 |
1985年 | 90篇 |
1984年 | 71篇 |
1983年 | 46篇 |
1982年 | 63篇 |
1981年 | 60篇 |
1980年 | 40篇 |
1979年 | 34篇 |
1978年 | 31篇 |
1977年 | 26篇 |
1976年 | 31篇 |
1973年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
We investigate analytical properties of a measure geometric Laplacian which is given as the second derivative w.r.t. two atomless finite Borel measures μ and ν with compact supports supp μ ? supp ν on the real line. This class of operators includes a generalization of the well‐known Sturm‐Liouville operator as well as of the measure geometric Laplacian given by . We obtain for this differential operator under both Dirichlet and Neumann boundary conditions similar properties as known in the classical Lebesgue case for the euclidean Laplacian like Gauß‐Green‐formula, inversion formula, compactness of the resolvent and its kernel representation w.r.t. the corresponding Green function. Finally we prove nuclearity of the resolvent and give two representations of its trace. 相似文献
132.
Andreas Fischer 《Mathematical Programming》1997,76(3):513-532
The paper deals with complementarity problems CP(F), where the underlying functionF is assumed to be locally Lipschitzian. Based on a special equivalent reformulation of CP(F) as a system of equationsφ(x)=0 or as the problem of minimizing the merit functionΘ=1/2∥Φ∥
2
2
, we extend results which hold for sufficiently smooth functionsF to the nonsmooth case.
In particular, ifF is monotone in a neighbourhood ofx, it is proved that 0 εδθ(x) is necessary and sufficient forx to be a solution of CP(F). Moreover, for monotone functionsF, a simple derivative-free algorithm that reducesΘ is shown to possess global convergence properties. Finally, the local behaviour of a generalized Newton method is analyzed.
To this end, the result by Mifflin that the composition of semismooth functions is again semismooth is extended top-order semismooth functions. Under a suitable regularity condition and ifF isp-order semismooth the generalized Newton method is shown to be locally well defined and superlinearly convergent with the
order of 1+p. 相似文献
133.
《科学通报(英文版)》1994,39(14):1155-1155
134.
In this paper,the concept of the infinitesimal realization factor is extended to the parameter-dependent performance functions in closed queueing networks. Then the concepts of realization matrix (its elements are called realization factors) and performance potential are introduced,and the relations between infinitesimal realization factors and these two quantities are discussed. This provides a united framework for both IPA and non IPA approaches. Finally,another physical meaning of the service rate is given. 相似文献
135.
Fluorescence line narrowing (FLN) spectroscopy was used to study the role of the polypeptide chain in influencing the spectrum of Zn-substituted cytochrome c (Zn cyt c) and metal-free cyt c (porphyrin cyt c). For both derivatives the spectra show characteristics of relaxed fluorescence from an inhomogeneously broadened sample. Zero phonon lines and phonon wings can be clearly distinguished, and vibrational frequencies of the ground and excited states were identified. The inhomogeneous distribution width for porphyrin cyt c is slightly wider than that of Zn cyt c and a second population of molecules was apparent in the porphyrin cyt c. The phonon coupling was greater for Zn cyt c than for porphyrin cyt c, which may be due to the extra coupling to the polypeptide chain by metal ligation.This work has been done in partial fulfillment of the requirements for the Doctor of Philosophy degree. 相似文献
136.
137.
A. Gerasimov 《Journal of statistical physics》1993,70(3-4):939-948
The analysis is carried out of the response of the center of gravity (dipole moment) of the distribution of noninteracting thermalized nonlinear oscillators to a sinusoidal driving force. Heat bath coupling is modeled by damping and noise. The driving is weak, but the frequency is resonant, so that there is a nonlinear resonance in the phase space. The response has a linear part that can be obtained from the perturbation analysis and a small nonlinear correction that is specific for the resonant structure. 相似文献
138.
139.
李扬国 《汕头大学学报(自然科学版)》1992,7(1):9-16
在已获得的中能区反质子与核的中心势的光学势基础上,把光学势扩大到包含自旋轨道耦合势.在反质子能量为179.8,294.8和508MeV各情况下,分别计算和分析与~(12)C靶核的微分截面(dσ)/(dΩ),极化度P(θ)和自旋转动函数Q(θ).在与极化度的实验比较中,得到中能区普遍形式的反质子光学势. 相似文献
140.