全文获取类型
收费全文 | 19785篇 |
免费 | 2695篇 |
国内免费 | 1886篇 |
专业分类
电工技术 | 3036篇 |
技术理论 | 3篇 |
综合类 | 2366篇 |
化学工业 | 2621篇 |
金属工艺 | 736篇 |
机械仪表 | 985篇 |
建筑科学 | 1110篇 |
矿业工程 | 533篇 |
能源动力 | 665篇 |
轻工业 | 658篇 |
水利工程 | 352篇 |
石油天然气 | 590篇 |
武器工业 | 241篇 |
无线电 | 2448篇 |
一般工业技术 | 2257篇 |
冶金工业 | 703篇 |
原子能技术 | 299篇 |
自动化技术 | 4763篇 |
出版年
2024年 | 140篇 |
2023年 | 360篇 |
2022年 | 486篇 |
2021年 | 602篇 |
2020年 | 779篇 |
2019年 | 771篇 |
2018年 | 648篇 |
2017年 | 785篇 |
2016年 | 837篇 |
2015年 | 820篇 |
2014年 | 1140篇 |
2013年 | 1295篇 |
2012年 | 1224篇 |
2011年 | 1342篇 |
2010年 | 996篇 |
2009年 | 986篇 |
2008年 | 1090篇 |
2007年 | 1184篇 |
2006年 | 1198篇 |
2005年 | 1015篇 |
2004年 | 906篇 |
2003年 | 784篇 |
2002年 | 745篇 |
2001年 | 624篇 |
2000年 | 552篇 |
1999年 | 521篇 |
1998年 | 355篇 |
1997年 | 352篇 |
1996年 | 303篇 |
1995年 | 261篇 |
1994年 | 247篇 |
1993年 | 222篇 |
1992年 | 164篇 |
1991年 | 114篇 |
1990年 | 109篇 |
1989年 | 67篇 |
1988年 | 66篇 |
1987年 | 35篇 |
1986年 | 34篇 |
1985年 | 20篇 |
1984年 | 31篇 |
1983年 | 25篇 |
1982年 | 24篇 |
1981年 | 13篇 |
1980年 | 12篇 |
1979年 | 17篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1960年 | 5篇 |
1959年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
This paper is concerned with the state estimation problem for the complex networked systems with randomly occurring nonlinearities and randomly missing measurements. The nonlinearities are included to describe the phenomena of nonlinear disturbances which exist in the network and may occur in a probabilistic way. Considering the fact that probabilistic data missing may occur in the process of information transmission, we introduce the randomly data missing into the sensor measurements. The aim of this paper is to design a state estimator to estimate the true states of the considered complex network through the available output measurements. By using a Lyapunov functional and some stochastic analysis techniques, sufficient criteria are obtained in the form of linear matrix inequalities under which the estimation error dynamics is globally asymptotically stable in the mean square. Furthermore, the state estimator gain is also obtained. Finally, a numerical example is employed to illustrate the effectiveness of the proposed state estimation conditions. 相似文献
122.
Shu Liang Cheng Peng Zeng Liao Yong Wang 《International journal of systems science》2014,45(10):2203-2212
Approximations for general fractional order dynamic systems are of much theoretical and practical interest. In this paper, a new approximate method for fractional order integrator is proposed. The poles of the approximate model are unrelated to the order of integrator. This feature shows benefits on extending the algorithm to the systems containing various fractional orders. Then a unified approximate method is derived for general fractional order linear or nonlinear dynamic systems via combining the proposed new method with the distributed frequency model approach. Numerical examples are given to show the wide applicability of our method and to illustrate the acceptable accuracy for approximations as well. 相似文献
123.
In this article, we consider a receding horizon control of discrete-time state-dependent jump linear systems, a particular kind of stochastic switching systems, subject to possibly unbounded random disturbances and probabilistic state constraints. Due to the nature of the dynamical system and the constraints, we consider a one-step receding horizon. Using inverse cumulative distribution function, we convert the probabilistic state constraints to deterministic constraints, and obtain a tractable deterministic receding horizon control problem. We consider the receding horizon control law to have a linear state-feedback and an admissible offset term. We ensure mean square boundedness of the state variable via solving linear matrix inequalities off-line, and solve the receding horizon control problem on-line with control offset terms. We illustrate the overall approach applied on a macroeconomic system. 相似文献
124.
本文应用三种不同晶形的溴碘化银乳剂(立方体、八面体和T-颗粒)和八种硫碳菁染料(大部分为内铵盐结构染料)进行了染料的聚集态的研究。试验结果表明,染料的J-聚集态的形成主要取决于染料的结构,其次依赖于卤化银的晶形。三种不同结构的表面活性剂对染料聚集态的形成均有影响,其中两性的表面活性剂最强,阴离子的表面活性剂次之,中性的表面活性剂最弱。二种中位甲基取代的硫碳菁染料的聚集态受表面活性剂影响最为明显,形成较强的J-态,而对其它六种染料的聚集态影响较小,J-聚集态稍有增强。 相似文献
125.
In order to supplement the literature data on VLE, isobaric bubble temperature data were collected for the binary systems phenol-i-amyl alcohol and phenol-n-amyl alcohol over the entire composition range by indirect method using a standard Swietoslawski type ebulliometer. The measurements were made at three sub-atmospheric pressures. The experimental t-x data were correlated with both equation of state method and gamma-phi methods. In the former approach, the Soave equation of state is used, whereas in the latter case Wilson, NRTL and UNIQUAC equations are used. 相似文献
126.
Selection of strategies that help reduce riverine inputs requires numerical models that accurately quantify hydrologic processes. While numerous models exist, information on how to evaluate and select the most robust models is limited. Toward this end, we developed a comprehensive approach that helps evaluate watershed models in their ability to simulate flow regimes critical to downstream ecosystem services. We demonstrated the method using the Soil and Water Assessment Tool (SWAT), the Hydrological Simulation Program–FORTRAN (HSPF) model, and Distributed Large Basin Runoff Model (DLBRM) applied to the Maumee River Basin (USA). The approach helped in identifying that each model simulated flows within acceptable ranges. However, each was limited in its ability to simulate flows triggered by extreme weather events, owing to algorithms not being optimized for such events and mismatched physiographic watershed conditions. Ultimately, we found HSPF to best predict river flow, whereas SWAT offered the most flexibility for evaluating agricultural management practices. 相似文献
127.
The clay is treated with a reducing agent and an acid so as to obtain a clay containing various metal components with a variable‐valence state. Then, the clay is coprecipitated with natural rubber (NR) latex to prepare a vulcanized NR/clay composite. The degradation process of the NR/clay composite under hot air condition was studied dynamically by using a Fourier transform infrared spectrometer attaching an in situ sample cell and was also investigated using the TGA method. The test result obtained from the infrared spectrometry indicated that under low decomposition temperature, the decomposition products of the test samples mainly are ethylene, low molecular olefinic hydrocarbon, and carbonyl compounds. As the decomposition temperature rises, the low molecular olefinic hydrocarbon content decreases, the olefine with longer chain is formed, and a lot of alkane decomposition products are formed at the same time. When the content of the metal components with a variable‐valence state in clay such as Cu, Mn, Co, and Fe increases, the oxidation products containing the carbonyl group, the olefinic hydrocarbon, and CO2 in the decomposition product of the test sample also increase. The TGA result clearly shows a shoulder peak that appears by the side of the main peak on the DTG curve of NR/clay composite. With the increase in the content of metal components with variable‐valence state in clay, the initial degradation temperature of the test sample (T0), the degradation peak temperature (Tp1), and the final degradation temperature (Tf1) in first‐stage reaction, as well as the degradation peak temperature (Tp2) and the last final degradation temperature (Tf) in second‐stage reaction of all the test samples more or less shift to the direction of low temperature; besides, the activation energy (E) of the reaction of the test samples more or less decreases. This means that the metal components with variable‐valence state promote the oxidative degradation of the clay–rubber masterbatch. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3809–3815, 2006 相似文献
128.
本文采用MH-81′状态方程和与密度无关的局部组成型混合法则,从二元汽-液平衡数据得到的二元相互作用参数,预测了部分液氮洗过程中的二元体系的混合焓,结果满意。采用三对角矩阵方法,对两种不同工况的液氮洗涤塔进行了模拟,计算结果与设计值和实测值符合较好。 相似文献
129.
M. F. Gogulya M. N. Makhov M. A. Brazhnikov A. Yu. Dolgoborodov 《Combustion, Explosion, and Shock Waves》2006,42(4):480-485
The effect of the addition of Al on the detonation velocity of bis(2,2,2-trinitroethyl) nitramine (BTNEN) was studied experimentally.
It is shown that the dependence of the detonation velocity of BTNEN on the initial density is nearly linear, and a 75/25 BTNEN/Al
mixture is characterized by an increase in the slope of the dependence with increasing density. The addition of Al decreases
the detonation velocity of BTNEN. The density range characterized by a maximum decrease in the detonation velocity is determined.
A comparison of experimental detonation velocities of BTNEN/Al mixtures with literature data obtained by calculations taking
into account a possible change in the phase state of Al2O3 showed that the thermodynamic model used in the calculations needs to be improved.
__________
Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 4, pp. 125–130, July–August, 2006. 相似文献
130.
This paper investigates the cubature Kalman filtering (CKF) for nonlinear dynamic systems. This third‐degree rule based filter employs a spherical‐radial cubature rule to numerically compute the integrals encountered in nonlinear filtering problems, thereby removing the requirements of explicitly computing the Jacobians. The cubature rule, however, requires computing the intractable integrals over a high‐dimensional spherical region for multidimensional applications. Moreover, the cubature formula that has been used to construct the spherical cubature formula has some demerits, most notably its inconvenient properties in computation and low estimation accuracy. Aimed at these issues, a general class of CKFs that uses only cubature rules is derived in this paper. It can be shown that the conventional CKF is a special case of the proposed algorithm. The paper also includes higher‐degree CKFs, especially two representative types of the fifth‐degree CKFs. Performance of the proposed algorithms is demonstrated via two target tracking problems. The experimental results, presented herein, illustrate the superior performance of higher‐degree CKFs to conventional nonlinear filters. 相似文献