全文获取类型
收费全文 | 3923篇 |
免费 | 306篇 |
国内免费 | 164篇 |
专业分类
化学 | 300篇 |
晶体学 | 12篇 |
力学 | 382篇 |
综合类 | 14篇 |
数学 | 2394篇 |
物理学 | 1291篇 |
出版年
2024年 | 14篇 |
2023年 | 31篇 |
2022年 | 49篇 |
2021年 | 60篇 |
2020年 | 115篇 |
2019年 | 128篇 |
2018年 | 172篇 |
2017年 | 121篇 |
2016年 | 90篇 |
2015年 | 126篇 |
2014年 | 241篇 |
2013年 | 372篇 |
2012年 | 200篇 |
2011年 | 234篇 |
2010年 | 189篇 |
2009年 | 278篇 |
2008年 | 277篇 |
2007年 | 238篇 |
2006年 | 175篇 |
2005年 | 131篇 |
2004年 | 119篇 |
2003年 | 123篇 |
2002年 | 124篇 |
2001年 | 102篇 |
2000年 | 130篇 |
1999年 | 100篇 |
1998年 | 63篇 |
1997年 | 55篇 |
1996年 | 42篇 |
1995年 | 33篇 |
1994年 | 28篇 |
1993年 | 26篇 |
1992年 | 22篇 |
1991年 | 27篇 |
1990年 | 12篇 |
1989年 | 14篇 |
1988年 | 11篇 |
1987年 | 20篇 |
1986年 | 10篇 |
1985年 | 13篇 |
1984年 | 12篇 |
1983年 | 3篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1979年 | 7篇 |
1977年 | 8篇 |
1976年 | 4篇 |
1973年 | 12篇 |
1971年 | 2篇 |
1969年 | 3篇 |
排序方式: 共有4393条查询结果,搜索用时 578 毫秒
91.
Martina Hofmanová 《随机分析与应用》2013,31(4):663-670
In the first part of this article a new method of proving existence of weak solutions to stochastic differential equations with continuous coefficients having at most linear growth was developed. In this second part, we show that the same method may be used even if the linear growth hypothesis is replaced with a suitable Lyapunov condition. 相似文献
92.
《Applied Mathematical Modelling》2014,38(9-10):2505-2521
This paper investigates the essential conditions to improve the accuracy of a resistance spot welding computational study of advanced zinc coated steel sheets using rounded tip electrode. An experimental analysis is performed to highlight the required considerations for a suitable simulation. A sequential Electrical-Thermal-Metallurgical and Mechanical (ETMM) finite element analysis with appropriate precautions of the contact conditions enables to accurately simulate the nugget development during the welding. A critical smooth evolution of the contact radius is required. A fine meshing with an interfacial mesh size of at least 0.05 × 10−3 m combined with a coupling time step of 0.0025 s between the electrical-thermal-metallurgical and the mechanical analysis allows a regular incrementation of the contact radius, without burdening the time computing. Accurate values of the contact resistance depending on the interfacial pressure and temperature are essential for a good simulation of the nugget size. The ETMM calculation is successfully extended to the simulation of the welding of a typical two sheets assembly. 相似文献
93.
Let denote a Hermite process of order and self-similarity parameter . This process is -self-similar, has stationary increments and exhibits long-range dependence. When , it corresponds to the fractional Brownian motion, whereas it is not Gaussian as soon as . In this paper, we deal with a Vasicek-type model driven by , of the form . Here, and are considered as unknown drift parameters. We provide estimators for and based on continuous-time observations. For all possible values of and , we prove strong consistency and we analyze the asymptotic fluctuations. 相似文献
94.
Suppose that is a one-dimensional Brownian motion with negative drift . It is possible to make sense of conditioning this process to be in the state 0 at an independent exponential random time and if we kill the conditioned process at the exponential time the resulting process is Markov. If we let the rate parameter of the random time go to 0, then the limit of the killed Markov process evolves like conditioned to hit 0, after which time it behaves as killed at the last time visits 0. Equivalently, the limit process has the dynamics of the killed “bang–bang” Brownian motion that evolves like Brownian motion with positive drift when it is negative, like Brownian motion with negative drift when it is positive, and is killed according to the local time spent at 0.An extension of this result holds in great generality for a Borel right process conditioned to be in some state at an exponential random time, at which time it is killed. Our proofs involve understanding the Campbell measures associated with local times, the use of excursion theory, and the development of a suitable analogue of the “bang–bang” construction for a general Markov process.As examples, we consider the special case when the transient Borel right process is a one-dimensional diffusion. Characterizing the limiting conditioned and killed process via its infinitesimal generator leads to an investigation of the -transforms of transient one-dimensional diffusion processes that goes beyond what is known and is of independent interest. 相似文献
95.
《Stochastic Processes and their Applications》2019,129(6):2086-2129
Many properties of Brownian motion on spaces with varying dimension (BMVD in abbreviation) have been explored in Chen and Lou (2018). In this paper, we study Brownian motion with drift on spaces with varying dimension (BMVD with drift in abbreviation). Such a process can be conveniently defined by a regular Dirichlet form that is not necessarily symmetric. Through the method of Duhamel’s principle, it is established in this paper that the transition density of BMVD with drift has the same type of two-sided Gaussian bounds as that for BMVD (without drift). As a corollary, we derive Green function estimate for BMVD with drift. 相似文献
96.
97.
This paper examines the cycling behavior of a deterministic and a stochastic version of the economic interpretation of the Lotka–Volterra model, the Goodwin model. We provide a characterization of orbits in the deterministic highly non-linear model. We then study a stochastic version, with Brownian noise introduced via a heterogeneous productivity factor. Existence conditions for a solution to the system are provided. We prove that the system produces cycles around a unique equilibrium point in finite time for general volatility levels, using stochastic Lyapunov techniques for recurrent domains. Numerical insights are provided. 相似文献
98.
99.
Ciprian A. Tudor Nakahiro Yoshida 《Stochastic Processes and their Applications》2019,129(9):3499-3526
We develop the asymptotic expansion theory for vector-valued sequences of random variables in terms of the convergence of the Stein–Malliavin matrix associated with the sequence . Our approach combines the classical Fourier approach and the recent Stein–Malliavin theory. We find the second order term of the asymptotic expansion of the density of and we illustrate our results by several examples. 相似文献
100.
In this article, we prove the existence and multiplicity of non-trivial solutions for an indefinite fractional elliptic equation with magnetic field and concave–convex nonlinearities. Our multiplicity results are based on studying the decomposition of the Nehari manifold. 相似文献