全文获取类型
收费全文 | 47848篇 |
免费 | 5883篇 |
国内免费 | 3248篇 |
专业分类
化学 | 5220篇 |
晶体学 | 276篇 |
力学 | 6101篇 |
综合类 | 593篇 |
数学 | 30627篇 |
物理学 | 14162篇 |
出版年
2024年 | 105篇 |
2023年 | 456篇 |
2022年 | 653篇 |
2021年 | 789篇 |
2020年 | 1362篇 |
2019年 | 1326篇 |
2018年 | 1243篇 |
2017年 | 1320篇 |
2016年 | 1482篇 |
2015年 | 1205篇 |
2014年 | 2172篇 |
2013年 | 4106篇 |
2012年 | 2301篇 |
2011年 | 2678篇 |
2010年 | 2521篇 |
2009年 | 2816篇 |
2008年 | 2992篇 |
2007年 | 3028篇 |
2006年 | 2668篇 |
2005年 | 2623篇 |
2004年 | 2242篇 |
2003年 | 2217篇 |
2002年 | 1998篇 |
2001年 | 1637篇 |
2000年 | 1569篇 |
1999年 | 1450篇 |
1998年 | 1277篇 |
1997年 | 1134篇 |
1996年 | 815篇 |
1995年 | 668篇 |
1994年 | 549篇 |
1993年 | 422篇 |
1992年 | 382篇 |
1991年 | 354篇 |
1990年 | 291篇 |
1989年 | 198篇 |
1988年 | 200篇 |
1987年 | 179篇 |
1986年 | 170篇 |
1985年 | 208篇 |
1984年 | 184篇 |
1983年 | 92篇 |
1982年 | 156篇 |
1981年 | 143篇 |
1980年 | 114篇 |
1979年 | 124篇 |
1978年 | 88篇 |
1977年 | 79篇 |
1976年 | 68篇 |
1974年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
In this paper we show that the Boltzmann weights of the three-dimensional Baxter-Bazhanov model give representations of the braid group if some suitable spectral limits are taken. In the trigonometric case we classify all possible spectral limits which produce braid group representations. Furthermore, we prove that for some of them we get cyclotomic invariants of links and for others we obtain tangle invariants generalizing the cyclotomic ones. 相似文献
82.
We consider an optimal growth (multi-sector) model with nonconvex technology. Using the Clarke results on generalized gradients, we prove that the value function has left and right derivatives with respect to the initial capital stock, without requiring supermodularity assumptions. 相似文献
83.
The purpose of this paper is to give the Reid ``Roundabout Theorem' for quadratic functionals with general boundary conditions.
In particular, we describe the so-called coupled point and regularity condition introduced in [16] in terms of Riccati equation
solutions.
Accepted 27 February 1996 相似文献
84.
1IntroductionThebrainofmankindhasmanycognitivefunctionssuchaslearning,asociationandoptimizationetc..Theneuronisthemostfoundam... 相似文献
85.
对一类变形的变分不等式:求,使得提出了一类投影收缩算法,并得到了该算法的收敛性及相关性质. 相似文献
86.
An analytic and numerical study of the behavior of the linear nonhomogeneous wave equation of the form ε2utt = Δu + tf with high wave speed (ε 1) is carried out. This study was initially motivated by meteorological observations which have indicated the presence of large spatial scale gravity waves in the neighborhood of a number of summer and winter storms, mainly from visible images of ripples in clouds in satellite photos. There is a question as to whether the presence of these waves is caused by the nearby storms. Since the linear wave equation is an approximation to the full system describing pressure waves in the atmosphere, yet is considerably more tractable, we have chosen to analyze the behavior of the linear nonhomogeneous wave equation with high wave speed. The analysis is shown to be valid in one, two, and three space dimensions. Partly because of the high wave speed, the solution is known to consist of behavior which changes on two different time scales, one rapid and one slow. Additionally, because of the presence of the nonhomogeneous forcing term tf, we show that there is a component of the solution which will vary only on a very large spatial scale. Since even the linearized wave equation can give rise to persistent large spatial scale waves under the right conditions, the implication is that certain storms could be responsible for the generation of large-scale waves. Numerical simulations in one and two dimensions confirm analytic results. 相似文献
87.
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
88.
Modified Stern-Volmer equation is obeyed by bovine serum albumin (BSA)-iodide system showing selective quenching of tryptophanyl
fluorescence of BSA. The fraction of accessible protein fluorescence is 0.56 and the effective Stern-Volmer constant is 290
M-1 at pH 7.4 in 0.005 M phosphate buffer at 25°C. Collisional quenching is operative both in the BSA -I−1 system and the model system, tryptophan-I−1. It is supported by the observed relationship between the ratio of quenching rate constants (k
q
) and diffusion coefficients and alsok
q
with bulk viscosity. 相似文献
89.
90.
Linear and nonlinear optical properties of racemic (±)2-(α-methylbenzylamino)-5-nitropyridine ((±)MBANP) single crystals have been comprehensively investigated and compared with those of the enantiomorph (–)2-(α-methylbenzylamino)-5-nitropyridine ((–)MBANP) crystals. (±)MBANP crystal exhibits very high chemical and physical stability, but relatively small nonlinear optical coefficients (d31 = 6.8 pm/V, d32 = 4.7 pm/V, d33 = 0.84 pm/V). A comparison between the nonlinear optical coefficients of (±)MBANP and (–)MBANP demonstrates the validity of the oriented-gas model in molecular crystals that neglects all the contributions from intermolecular interaction. 相似文献