全文获取类型
收费全文 | 49661篇 |
免费 | 5144篇 |
国内免费 | 3572篇 |
专业分类
电工技术 | 3656篇 |
技术理论 | 8篇 |
综合类 | 6712篇 |
化学工业 | 4156篇 |
金属工艺 | 1596篇 |
机械仪表 | 2890篇 |
建筑科学 | 4235篇 |
矿业工程 | 2067篇 |
能源动力 | 2108篇 |
轻工业 | 1693篇 |
水利工程 | 1494篇 |
石油天然气 | 1714篇 |
武器工业 | 707篇 |
无线电 | 4241篇 |
一般工业技术 | 5895篇 |
冶金工业 | 2909篇 |
原子能技术 | 412篇 |
自动化技术 | 11884篇 |
出版年
2024年 | 209篇 |
2023年 | 839篇 |
2022年 | 1146篇 |
2021年 | 1363篇 |
2020年 | 1611篇 |
2019年 | 1481篇 |
2018年 | 1520篇 |
2017年 | 1708篇 |
2016年 | 1866篇 |
2015年 | 1822篇 |
2014年 | 2798篇 |
2013年 | 3528篇 |
2012年 | 3214篇 |
2011年 | 3590篇 |
2010年 | 2718篇 |
2009年 | 2986篇 |
2008年 | 2949篇 |
2007年 | 3161篇 |
2006年 | 3027篇 |
2005年 | 2635篇 |
2004年 | 2128篇 |
2003年 | 1779篇 |
2002年 | 1594篇 |
2001年 | 1219篇 |
2000年 | 1058篇 |
1999年 | 944篇 |
1998年 | 724篇 |
1997年 | 678篇 |
1996年 | 576篇 |
1995年 | 549篇 |
1994年 | 448篇 |
1993年 | 374篇 |
1992年 | 340篇 |
1991年 | 246篇 |
1990年 | 214篇 |
1989年 | 206篇 |
1988年 | 159篇 |
1987年 | 88篇 |
1986年 | 111篇 |
1985年 | 84篇 |
1984年 | 87篇 |
1983年 | 61篇 |
1982年 | 74篇 |
1981年 | 59篇 |
1980年 | 41篇 |
1979年 | 44篇 |
1978年 | 40篇 |
1977年 | 31篇 |
1964年 | 26篇 |
1955年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
1.
Hashim A.
Hashim 《国际强度与非线性控制杂志
》2020,30(10):3848-3870
》2020,30(10):3848-3870
This paper introduces two novel nonlinear stochastic attitude estimators developed on the Special Orthogonal Group with the tracking error of the normalized Euclidean distance meeting predefined transient and steady‐state characteristics. The tracking error is confined to initially start within a predetermined large set such that the transient performance is guaranteed to obey dynamically reducing boundaries and decrease smoothly and asymptotically to the origin in probability from almost any initial condition. The proposed estimators produce accurate attitude estimates with remarkable convergence properties using measurements obtained from low‐cost inertial measurement units. The estimators proposed in continuous form are complemented by their discrete versions for the implementation purposes. The simulation results illustrate the effectiveness and robustness of the proposed estimators against uncertain measurements and large initialization error, whether in continuous or discrete form. 相似文献
2.
Based on the current spin density functional theory, a theoretical model of three vertically aligned semiconductor quantum dots is proposed and numerically studied. This quantum dot molecule (QDM) model is treated with realistic hard-wall confinement potential and external magnetic field in three-dimensional setting. Using the effective-mass approximation with band nonparabolicity, the many-body Hamiltonian results in a cubic eigenvalue problem from a finite difference discretization. A self-consistent algorithm for solving the Schrödinger-Poisson system by using the Jacobi-Davidson method and GMRES is given to illustrate the Kohn-Sham orbitals and energies of six electrons in the molecule with some magnetic fields. It is shown that the six electrons residing in the central dot at zero magnetic field can be changed to such that each dot contains two electrons with some feasible magnetic field. The Förster-Dexter resonant energy transfer may therefore be generated by two individual QDMs. This may motivate a new paradigm of Fermionic qubits for quantum computing in solid-state systems. 相似文献
3.
讨论了在VMI管理思想下对具有随机需求特性的多客户库存分配问题 ,重点论述了有效近似算法的设计过程 ,最后基于一组模拟数据给出了一个算例。 相似文献
4.
5.
论文提出利用用户提供的个性化信息来随机产生关联大素数,保证了素数选取的随机化、个性化,提高了RSA算法的安全性。 相似文献
6.
7.
The effects of parameter uncertainty on optimal policy have been a matter of interest for academics, and even for some policymakers,
for a long time. Two lines of literature have developed analytical results on this matter. The first line uses static models
and the second dynamic models. In this dynamic line most of the results are confined to models with a single state and a single
control variable.
In this paper we want to encourage the analysis of more general dynamic cases. To do so, the results in the dynamic line are
extended from one-state and one-control finite horizon models to models with a pair of control variables. We then discuss
some of the hurdles which must be surmounted for the results to be made more general and suggests some lines for further research.
JEL classification: C61; E61 相似文献
8.
基于模式理论光栅椭偏参数反演的数值模拟 总被引:5,自引:2,他引:3
将一种广泛用于求解系统优化问题的方法——正单纯形法,求解光栅的椭偏方程。首先,利用求解光栅的傅立叶模式理论对TE和TM波的复反射系数进行求解。然后计算出其相应的椭偏参数(△,Ψ),并在该值的基础上加入不同偏差的随机高斯噪声,将加入噪声后的值(△m,Ψm)作为模拟测量值。最后使用优化算法进行反演。通过对几种常用面形光栅椭偏参数的数值模拟,一方面表明傅立叶模式理论计算光栅的椭偏参数不仅精度高。而且速度快;另一方面表明利用正单纯形法得到的光栅参数值很接近于正演时假设的参数值,从而从理论上证明了利用椭偏法测量光栅各种光学参数的可行性。 相似文献
9.
This paper proposes an original method for obtaining analytical approximations of the invariant probability density function of multi-dimensional Hamiltonian dissipative dynamic systems under Gaussian white noise excitations, with linear non-conservative parts and nonlinear conservative parts. The method is based on an exact result and a heuristic argument. Its pertinence is attested by numerical tests. 相似文献
10.
An analysis is made of the characteristic features and problems of the optimal processing of the results of measurements in the case of a random observation function utilizing a nonlinear Kalman filter. A method is proposed for increasing the convergence domain of the filter with additional processing of measurements in the frequency domain. 相似文献