全文获取类型
收费全文 | 21163篇 |
免费 | 2229篇 |
国内免费 | 1274篇 |
专业分类
电工技术 | 2638篇 |
综合类 | 2816篇 |
化学工业 | 2445篇 |
金属工艺 | 337篇 |
机械仪表 | 1126篇 |
建筑科学 | 741篇 |
矿业工程 | 292篇 |
能源动力 | 562篇 |
轻工业 | 693篇 |
水利工程 | 482篇 |
石油天然气 | 538篇 |
武器工业 | 197篇 |
无线电 | 2083篇 |
一般工业技术 | 2369篇 |
冶金工业 | 608篇 |
原子能技术 | 187篇 |
自动化技术 | 6552篇 |
出版年
2024年 | 80篇 |
2023年 | 253篇 |
2022年 | 359篇 |
2021年 | 512篇 |
2020年 | 553篇 |
2019年 | 547篇 |
2018年 | 594篇 |
2017年 | 684篇 |
2016年 | 790篇 |
2015年 | 815篇 |
2014年 | 1153篇 |
2013年 | 1349篇 |
2012年 | 1630篇 |
2011年 | 1721篇 |
2010年 | 1173篇 |
2009年 | 1308篇 |
2008年 | 1242篇 |
2007年 | 1321篇 |
2006年 | 1259篇 |
2005年 | 1000篇 |
2004年 | 821篇 |
2003年 | 812篇 |
2002年 | 683篇 |
2001年 | 539篇 |
2000年 | 496篇 |
1999年 | 401篇 |
1998年 | 396篇 |
1997年 | 320篇 |
1996年 | 322篇 |
1995年 | 241篇 |
1994年 | 218篇 |
1993年 | 156篇 |
1992年 | 140篇 |
1991年 | 122篇 |
1990年 | 113篇 |
1989年 | 99篇 |
1988年 | 84篇 |
1987年 | 59篇 |
1986年 | 35篇 |
1985年 | 40篇 |
1984年 | 34篇 |
1983年 | 22篇 |
1982年 | 35篇 |
1981年 | 24篇 |
1980年 | 14篇 |
1979年 | 9篇 |
1978年 | 11篇 |
1977年 | 17篇 |
1964年 | 10篇 |
1963年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 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.
文章介绍了一种新型的短波跳频通信技术——差分跳频,分析了差分跳频技术区别于常规跳频技术的主要特点。针对按序列检测的信号接收方法,对差分跳频通信系统在AWGN信道下的性能进行了理论分析,同时做出相应的计算机仿真,证实了差分跳频通信技术和按序列检测方法的结合,使通信系统在AWGN信道下的性能得到了比较显著的提升。 相似文献
3.
The mechanical properties of a medium molecular weight polyethylene (MMW‐PE) and an ultrahigh molecular weight PE (UHMW‐PE) binary mixture with different weight fractions crystallized from the melt at 0.1 and 450 MPa were studied. The tensile modulus, yield stress, and strain were obtained as a function of the weight fractions in the PE mixtures at 25 and 85°C. The tensile modulus in the sample crystallized at 0.1 MPa decreased from 1.5 GPa of pure MMW‐PE to about 0.4 GPa of pure UHMW‐PE with the UHMW‐PE content but it did not decrease with the UHMW‐PE in the sample crystallized at 450 MPa in testing at 25°C. A decreasing rate of the storage modulus E′ of UHMW‐PE in a dynamic measurement for the sample crystallized at 0.1 MPa with the temperature is larger than that of the sample crystallized at 450 MPa. These experimental facts are interpreted in relation to the molecular motion and crystallinity of the sample. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1962–1968, 2003 相似文献
4.
In this paper, the moving least-squares differential quadrature (MLSDQ) method is employed for free vibration of thick antisymmetric laminates based on the first-order shear deformation theory. The generalized displacements of the laminates are independently approximated with the centered moving least-squares (MLS) technique within each domain of influence. The MLS nodal shape functions and their partial derivatives are computed quickly through back-substitutions after only one LU decomposition. Subsequently, the weighting coefficients in the MLSDQ discretization are determined with the nodal partial derivatives of the MLS shape functions. The MLSDQ method combines the merits of both the differential quadrature and meshless methods which can be conveniently applied to complex domains and irregular discretizations without loss of implementation efficiency and numerical accuracy. The natural frequencies of the laminates with various edge conditions, ply angles, and shapes are calculated and compared with the existing solutions to study the numerical accuracy and stability of the MLSDQ method. Effects of support size, order of completeness of basis functions, and node irregularity on the numerical accuracy are investigated in detail. 相似文献
5.
A stochastic model for local disturbances, particularly for a temporal harmonic with random modulations in amplitude and/or phase, is proposed in this paper. Results for the second moment responses of a linear single-degree-of-freedom system to this type of stochastic loading demonstrate a significant change in response characteristics due to a small uncertainty. A local phenomenon may last much longer and resonance may be smeared to a broad range. Integrated with wavelet transform, the proposed approach may be used to model a random process with non-stationary frequency content. Especially, it can be effectively used for Monte Carlo simulation to generate large size of samples that have similar characteristics in time and frequency domains as a pre-selected mother sample has. The technique has a great potential for the case where uncertainty study is warranted but the available samples are limited. 相似文献
6.
7.
The scale along the coordinate axes in the equations of motion hitherto used for an H-maser (in relative units) is shown to depend on Q as the quality factor for an H-maser. This hinders both analysis of the operation of the H-maser and optimization of its parameters. The modified equations of motion proposed here do not have that shortcoming. We determine the atomic flux into the bulb that gives the H-maser the best metrological characteristics. 相似文献
8.
随着电容测量技术的迅速发展,电容传感器在非电量测量和自动检测中得到广泛应用,但它在使用过程中也存在一些问题,针对在使用电容传感器过程中存在的几个问题,从电容传感器的原理和工作过程两个方面进行了讨论,并提出行之有效的处理方法。 相似文献
9.
10.
We propose a general modeling framework to evaluate the performance of cache consistency algorithms. In addition to the usual hit rate, we introduce the hit* rate as a consistency measure, which captures the fraction of non-stale downloads from the cache. We apply these ideas to the analysis of the fixed TTL consistency algorithm in the presence of network delays. The hit and hit* rates are evaluated when requests and updates are modeled by renewal processes. Classical results on the renewal function lead to various bounds. 相似文献