全文获取类型
收费全文 | 567835篇 |
免费 | 10763篇 |
国内免费 | 4326篇 |
专业分类
电工技术 | 12485篇 |
技术理论 | 1篇 |
综合类 | 4507篇 |
化学工业 | 85336篇 |
金属工艺 | 30641篇 |
机械仪表 | 22423篇 |
建筑科学 | 14341篇 |
矿业工程 | 6212篇 |
能源动力 | 11457篇 |
轻工业 | 37799篇 |
水利工程 | 8051篇 |
石油天然气 | 17646篇 |
武器工业 | 566篇 |
无线电 | 60642篇 |
一般工业技术 | 121579篇 |
冶金工业 | 78828篇 |
原子能技术 | 15742篇 |
自动化技术 | 54668篇 |
出版年
2022年 | 4547篇 |
2021年 | 6477篇 |
2020年 | 5001篇 |
2019年 | 5699篇 |
2018年 | 14452篇 |
2017年 | 15005篇 |
2016年 | 13594篇 |
2015年 | 7586篇 |
2014年 | 11522篇 |
2013年 | 23565篇 |
2012年 | 18294篇 |
2011年 | 25566篇 |
2010年 | 21897篇 |
2009年 | 22314篇 |
2008年 | 23208篇 |
2007年 | 23822篇 |
2006年 | 16364篇 |
2005年 | 16212篇 |
2004年 | 14481篇 |
2003年 | 13754篇 |
2002年 | 12556篇 |
2001年 | 11816篇 |
2000年 | 11403篇 |
1999年 | 10583篇 |
1998年 | 20751篇 |
1997年 | 15637篇 |
1996年 | 12233篇 |
1995年 | 9765篇 |
1994年 | 8867篇 |
1993年 | 8901篇 |
1992年 | 7404篇 |
1991年 | 7195篇 |
1990年 | 7110篇 |
1989年 | 6767篇 |
1988年 | 6494篇 |
1987年 | 6066篇 |
1986年 | 5907篇 |
1985年 | 6507篇 |
1984年 | 6241篇 |
1983年 | 5774篇 |
1982年 | 5470篇 |
1981年 | 5572篇 |
1980年 | 5425篇 |
1979年 | 5497篇 |
1978年 | 5559篇 |
1977年 | 5931篇 |
1976年 | 6985篇 |
1975年 | 5113篇 |
1974年 | 5154篇 |
1973年 | 5237篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
991.
Jun-Guo Lu Hill D.J. 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2008,55(6):586-590
Sampled-data feedback control for master-slave synchronization schemes that consist of identical chaotic Lur'e systems is studied. Sufficient conditions for global asymptotic synchronization of such chaotic Lur'e systems are obtained using the free-weighting matrix approach and expressed in terms of linear matrix inequalities (LMIs). With the help of the LMI solvers, the sampled-data feedback control law can easily be obtained to globally asymptotically synchronize Lur'e chaotic systems. The effectiveness of the proposed method is finally illustrated via numerical simulations of chaotic Chua's circuits. 相似文献
992.
H.J. Bolink E. Coronado D. Repetto M. Sessolo E.M. Barea J. Bisquert G. Garcia‐Belmonte J. Prochazka L. Kavan 《Advanced functional materials》2008,18(1):145-150
A new type of bottom‐emission electroluminescent device is described in which a metal oxide is used as the electron‐injecting contact. The preparation of such a device is simple. It consists of the deposition of a thin layer of a metal oxide on top of an indium tin oxide covered glass substrate, followed by the solution processing of the light‐emitting layer and subsequently the deposition of a high‐workfunction (air‐stable) metal anode. This architecture allows for a low‐cost electroluminescent device because no rigorous encapsulation is required. Electroluminescence with a high brightness reaching 5700 cd m–2 is observed at voltages as low as 8 V, demonstrating the potential of this new approach to organic light‐emitting diode (OLED) devices. Unfortunately the device efficiency is rather low because of the high current density flowing through the device. We show that the device only operates after the insertion of an additional hole‐injection layer in between the light‐emitting polymer (LEP) and the metal anode. A simple model that explains the experimental results and provides avenues for further optimization of these devices is described. It is based on the idea that the barrier for electron injection is lowered by the formation of a space–charge field over the metal‐oxide–LEP interface due to the build up of holes in the LEP layer close to this interface. 相似文献
993.
Xin Sun Qiang Lu Moroz V. Takeuchi H. Gebara G. Wetzel J. Shuji Ikeda Changhwan Shin Tsu-Jae King Liu 《Electron Device Letters, IEEE》2008,29(5):491-493
A tri-gate bulk MOSFET design utilizing a low-aspect-ratio channel is proposed to provide an evolutionary pathway for CMOS scaling to the end of the roadmap. 3-D device simulations indicate that this design offers the advantages of a multi-gate FET (reduced variability in performance and improved scalability) together with the advantages of a conventional planar MOSFET (low substrate cost and capability for dynamic threshold-voltage control). 相似文献
994.
We identify the time dependence of temperature of a surface of a long hollow thermosensitive cylinder and its thermal and
thermal stressed states according to the known temperature and strains on the other surface. The posed problem is reduced
to the inverse problem of thermoelasticity. By using the solution of the direct problem of thermoelasticity, we perform the
numerical verification of the proposed procedure of solution of the inverse problem.
__________
Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 43, No. 6, pp. 55–61, November–December, 2007. 相似文献
995.
J. H. Elder S. J. D. Prince Y. Hou M. Sizintsev E. Olevskiy 《International Journal of Computer Vision》2007,72(1):47-66
We address the problem of localizing and obtaining high-resolution footage of the people present in a scene. We propose a
biologically-inspired solution combining pre-attentive, low-resolution sensing for detection with shiftable, high-resolution,
attentive sensing for confirmation and further analysis.
The detection problem is made difficult by the unconstrained nature of realistic environments and human behaviour, and the
low resolution of pre-attentive sensing. Analysis of human peripheral vision suggests a solution based on integration of relatively
simple but complementary cues. We develop a Bayesian approach involving layered probabilistic modeling and spatial integration
using a flexible norm that maximizes the statistical power of both dense and sparse cues. We compare the statistical power
of several cues and demonstrate the advantage of cue integration. We evaluate the Bayesian cue integration method for human
detection on a labelled surveillance database and find that it outperforms several competing methods based on conjunctive
combinations of classifiers (e.g., Adaboost). We have developed a real-time version of our pre-attentive human activity sensor
that generates saccadic targets for an attentive foveated vision system. Output from high-resolution attentive detection algorithms
and gaze state parameters are fed back as statistical priors and combined with pre-attentive cues to determine saccadic behaviour.
The result is a closed-loop system that fixates faces over a 130 deg field of view, allowing high-resolution capture of facial
video over a large dynamic scene. 相似文献
996.
V. F. Ivanov A. A. Nekrasov K. V. Tcheberiako A. V. Vannikov A. S. Posed'ko S. I. Lishik Yu. V. Trofimov 《Journal of the Society for Information Display》2003,11(1):11-14
Abstract— An all solid‐state photoelectrochromic element (PECE) was developed on the basis of electrochromic layers of WO3 and polyaniline with a layer of polymer electrolyte placed on a base of polyamidosulfoacid, in which a thin‐film CdSxSe1?x photoresistor was used as an electronic key. The dependence of the sensitometric characteristics of the PECE on the applied voltage was studied. 相似文献
997.
998.
高分辨率合成孔径雷达图像舰船检测方法 总被引:7,自引:0,他引:7
寻找针对高分辨率SAR图像的舰船目标检测算法。利用KSW双阈值分割技术,其效果比传统检测方法好,有利于进一步的目标分类和识别。且必须根据SAR图像分辨率来选择舰船检测算法。 相似文献
999.
In classical model reference adaptive control, the goal is to design a controller to make the closed-loop system act like a prespecified reference model in the face of significant plant uncertainty. Typically, the controller consists of an identifier (or tuner) which is used to adjust the parameters of a linear time-invariant (LTI) compensator, and under suitable assumptions on the plant model uncertainty it is proven that asymptotic matching is achieved. However, the controller is typically highly nonlinear, and the closed loop system can exhibit undesirable behavior, such as large transients or a large control signal, especially if the initial parameter estimates are poor. Furthermore, its ability to tolerate time-varying parameters is typically limited. Here, we propose an alternative approach. Rather than estimating the plant or compensator parameters, instead we estimate what the control signal would be if the plant parameters and plant state were known and the "ideal LTI compensator" were applied. We end up with a linear periodic controller. Our assumptions are reasonably natural extensions of the classical ones to the time-varying setting; we allow rapid parameter variations, although we add a compactness requirement. We prove that we can obtain arbitrarily good tracking, explore the benefits and limitations of the approach, and provide a simulation study. 相似文献
1000.
Viktor G. Khizhnyak Vitalii I. Korol' Alexei D. Kostenko 《Powder Metallurgy and Metal Ceramics》2003,42(11-12):644-648
Wear resistance measurements have been made with U8A steel bearing protective coatings based on the carbides of titanium, vanadium, and chromium or iron borides, for various forms of wear. The carbide and boride coatings raise the wear resistance considerably (by factors of 6-30 in accordance with the type of wear). Measurements have been made on the microhardness, microbrittleness, and adhesion of the coating to the substrate, which are effective characteristics that quite fully reflect the effects of the microhardness and state of stress, structure, and defectiveness on the wear resistance. 相似文献