全文获取类型
收费全文 | 148876篇 |
免费 | 14627篇 |
国内免费 | 9121篇 |
专业分类
电工技术 | 10920篇 |
技术理论 | 2篇 |
综合类 | 12103篇 |
化学工业 | 20970篇 |
金属工艺 | 8868篇 |
机械仪表 | 9418篇 |
建筑科学 | 11504篇 |
矿业工程 | 4393篇 |
能源动力 | 4206篇 |
轻工业 | 13936篇 |
水利工程 | 3809篇 |
石油天然气 | 5875篇 |
武器工业 | 1604篇 |
无线电 | 18237篇 |
一般工业技术 | 16339篇 |
冶金工业 | 6664篇 |
原子能技术 | 2041篇 |
自动化技术 | 21735篇 |
出版年
2024年 | 744篇 |
2023年 | 2344篇 |
2022年 | 4987篇 |
2021年 | 6499篇 |
2020年 | 4637篇 |
2019年 | 3571篇 |
2018年 | 3918篇 |
2017年 | 4606篇 |
2016年 | 4055篇 |
2015年 | 5987篇 |
2014年 | 7604篇 |
2013年 | 9370篇 |
2012年 | 10998篇 |
2011年 | 11656篇 |
2010年 | 10664篇 |
2009年 | 10318篇 |
2008年 | 10449篇 |
2007年 | 9903篇 |
2006年 | 9169篇 |
2005年 | 7618篇 |
2004年 | 5318篇 |
2003年 | 3920篇 |
2002年 | 3898篇 |
2001年 | 3462篇 |
2000年 | 3120篇 |
1999年 | 2345篇 |
1998年 | 1937篇 |
1997年 | 1659篇 |
1996年 | 1467篇 |
1995年 | 1229篇 |
1994年 | 956篇 |
1993年 | 804篇 |
1992年 | 646篇 |
1991年 | 507篇 |
1990年 | 425篇 |
1989年 | 331篇 |
1988年 | 274篇 |
1987年 | 198篇 |
1986年 | 172篇 |
1985年 | 144篇 |
1984年 | 111篇 |
1983年 | 86篇 |
1982年 | 75篇 |
1981年 | 65篇 |
1980年 | 74篇 |
1979年 | 50篇 |
1978年 | 32篇 |
1977年 | 32篇 |
1976年 | 54篇 |
1973年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
We have studied lamp configuration design for rapid thermal processing (RTP) systems. We considered a configuration consisting of four concentric circular lamp zones, three of them above the wafer and one circumventing the wafer. We propose a method to determine the geometric parameters, the width, height and radius, of the lamp zones so that the configuration designed has the capacity to achieve a uniform temperature on the wafer. The method is based on a necessary and sufficient condition for uniform temperature tracking and analytic expressions of the view factors. A design example is given in which a least square open-loop control law yields good temperature uniformity 相似文献
12.
A technique for SiO2 formation by liquid-phase deposition (LPD) at nearly room temperature for low-temperature processed (LTP) polysilicon thin-film transistor (poly-Si TFT) was developed. LPD SiO2 film with a lower P-etch rate shows a dense structure. LPD SiO2 also exhibits good electrical characteristics. LTP poly-Si thin-film transistors (TFTs) with LPD SiO 2 as the gate insulator have been fabricated and investigated. Their characteristics indicate performance adequate for their use as pixel transistors in liquid crystal displays (LCDs) 相似文献
13.
Shyh-Jier Huang Jeu-Min Lin 《Power Systems, IEEE Transactions on》2002,17(4):1022-1029
In this paper, a gap-statistic-algorithm (GSA)-based data-mining technique is applied to enhance the data debugging in power system operations. In the proposed approach, the GSA technique is embedded into a neural network frame in anticipation of improving the detection capability of bad data. Thanks to the clustering capability exhibited by GSA in which the number of clusters can be optimally determined, the proposed approach becomes highly effective to localize the group of abnormal data. This proposed approach has been tested through the data collected from different scenarios made on an IEEE 30-bus system and 118-bus systems. Test results reveal the feasibility of the method for the data diagnosis applications. 相似文献
14.
Tzu-Ming Liu Yin-Chieh Huang Gia-Wei Chern Kung-Hsuan Lin Yu-Chueh Hung Chih-Jie Lee Chi-Kuang Sun 《Quantum Electronics, IEEE Journal of》2002,38(11):1529-1535
We present a method to obtain complete information of femtosecond pulses. By measuring triple-optical autocorrelation directly with third-harmonic generation, without spectral information, a temporal pulse shape can be obtained by analytical calculation without direction-of-time ambiguity. Combining the resulting optical pulse shape with its corresponding optical spectrum, the exact phase and color variations in time can all be recovered with a Gerchberg-Saxton algorithm through an iterative calculation with an O(n) complexity. 相似文献
15.
Chai-Chin Lin Chih-Ming Chen Jenn-Hwan Tarng Hsueh-Ming Hang Hsiao-Cheng Yu 《Broadcasting, IEEE Transactions on》2002,48(1):38-43
Field tests of the transmission performance of the ATSC DTV system have been conducted in Taiwan. The test results as well as comparisons against the NTSC system performance are reported and analyzed. From the measured results the reception characteristics of the DTV can be deduced and can provide guidelines for television stations to design the transmission system, schedule equipment deployment, plan service coverage areas, and improve the reception quality of the digital signal 相似文献
16.
The Uniform Covering by Probabilistic Rejection (UCPR) algorithm was used, in conjunction with the Soil and Water Assessment Tool (SWAT) model, to identify P loads from point source and nonpoint source polluters in the upper Etowah River basin (UERB) in Georgia. The key findings of the research are as follows. The mean absolute error was preferred over the root mean square error as a search criterion for the UCPR algorithm when water quality observations are scarce. The undocumented P load from point sources in the UERB was consistently estimated as about 43 kg/d by the proposed method; but the method was not able to identify the broiler litter application rate to the poultry/beef operation pastures. Point sources (both documented and undocumented), poultry/beef operation pastures, and forests are the three major contributors of P. During 1992-1996, on average they accounted for 36.4, 31.7, and 17.2% of P load from the UERB, respectively. 相似文献
17.
本文分析了锌基合金模具制造及使用过程中容易出现热裂、翘曲、收缩的问题,并提出了解决这些问题的措施。 相似文献
18.
GPRS无线DDN系统与应用 总被引:7,自引:1,他引:6
介绍基于GPRS网络无线DDN系统的构成、组网以及在电力系统的应用,同时对传输包长度、效率、时延等参数进行分析。 相似文献
19.
Enhancement of underfill capillary flow in flip-chip packaging by means of the inertia effect 总被引:1,自引:0,他引:1
Chao-Ming Lin 《Advanced Packaging, IEEE Transactions on》2004,27(3):533-539
This paper describes how the use of inertia forces induced by the rotation of a working disk may be adopted to increase the fill rate of the flip-chip packaging process and thereby reduce the process cycle time. It is shown how the driving forces resulting from the inertia effect are determined by the Weber number. The constant and varying contact angle models are compared under a specified set of process conditions. The calculated flow behavior results indicate that the relationship between the contact angle, the average fluid velocity, the liquid-air interface position, and the filling time depends upon the Weber number. The constant and varying contact angle models are utilized in the analysis of a new processing method referred to as rotation-enhanced underfill packaging (REUP). The inertia effect induced by the angular motion of the working disk is shown to enhance the flow of the underfill encapsulant and to reduce the time of the underfill process. The present results confirm that the rotation of the working disk leads to an increased underfill capillary flow rate, which is beneficial in reducing the production cycle time of the flip-chip packaging process. 相似文献
20.
Lianshan Yan Yeh C. Yang G. Lin L. Chen Z. Shi Y.Q. Willner A.E. Yao X.S. 《Lightwave Technology, Journal of》2003,21(7):1676-1684
We demonstrate the first programmable group-delay module based on polarization switching. With a unique binary tuning mechanism, the device can generate any differential group delay value from -45 to +45 ps with a resolution of 1.40 ps, or any true-time-delay value from 0 to 45 ps with a resolution of 0.7 ps. The delay varying speeds for both applications are under 1 ms and can be as fast as 0.1 ms. We evaluate both the dynamic and static performances of the device while paying special attention to its dynamic figures of merit for polarization-mode dispersion emulation and compensation applications. Our experiment shows that the device exhibits a negligible transient-effect induced power penalty (<0.2 dB) in a 10-Gb/s nonreturn-to-zero system. 相似文献