全文获取类型
收费全文 | 155785篇 |
免费 | 2210篇 |
国内免费 | 655篇 |
专业分类
电工技术 | 3146篇 |
综合类 | 193篇 |
化学工业 | 24802篇 |
金属工艺 | 5840篇 |
机械仪表 | 5026篇 |
建筑科学 | 4755篇 |
矿业工程 | 396篇 |
能源动力 | 4045篇 |
轻工业 | 17665篇 |
水利工程 | 1183篇 |
石油天然气 | 630篇 |
武器工业 | 6篇 |
无线电 | 20764篇 |
一般工业技术 | 29560篇 |
冶金工业 | 24348篇 |
原子能技术 | 2366篇 |
自动化技术 | 13925篇 |
出版年
2019年 | 903篇 |
2018年 | 1172篇 |
2017年 | 1218篇 |
2016年 | 1375篇 |
2015年 | 1132篇 |
2014年 | 1929篇 |
2013年 | 6894篇 |
2012年 | 3375篇 |
2011年 | 4885篇 |
2010年 | 3796篇 |
2009年 | 4356篇 |
2008年 | 4859篇 |
2007年 | 5131篇 |
2006年 | 4526篇 |
2005年 | 4278篇 |
2004年 | 4131篇 |
2003年 | 4001篇 |
2002年 | 4035篇 |
2001年 | 4051篇 |
2000年 | 3831篇 |
1999年 | 3768篇 |
1998年 | 6743篇 |
1997年 | 5330篇 |
1996年 | 4559篇 |
1995年 | 3767篇 |
1994年 | 3410篇 |
1993年 | 3252篇 |
1992年 | 2834篇 |
1991年 | 2728篇 |
1990年 | 2664篇 |
1989年 | 2659篇 |
1988年 | 2492篇 |
1987年 | 2206篇 |
1986年 | 2149篇 |
1985年 | 2596篇 |
1984年 | 2368篇 |
1983年 | 2236篇 |
1982年 | 2104篇 |
1981年 | 2030篇 |
1980年 | 1891篇 |
1979年 | 1898篇 |
1978年 | 1799篇 |
1977年 | 2115篇 |
1976年 | 2599篇 |
1975年 | 1610篇 |
1974年 | 1449篇 |
1973年 | 1468篇 |
1972年 | 1204篇 |
1971年 | 1088篇 |
1970年 | 935篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
152.
Croon J.A. Rosmeulen M. Decoutere S. Sansen W. Maes H.E. 《Solid-State Circuits, IEEE Journal of》2002,37(8):1056-1064
In this paper, a physics-based mismatch model is presented. It is demonstrated on a 0.18-/spl mu/m technology that a simple mismatch model can still be used to characterize deep-submicron technologies. The accuracy of the model is examined and found to be within 20% in the strong inversion region. Bulk bias dependence is modeled in a physical way. To extract the mismatch parameters, a weighted fit is introduced. It is shown that the width and length dependence of the mismatch parameters is given by the Pelgrom model. 相似文献
153.
Steinwandt R. Geiselmann W. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2002,48(11):2990-2991
An attack on the public key cryptosystem Polly Cracker is described, that reveals the complete secret key σ ∈ Fq n by means of n (nonadaptively) chosen "fake" ciphertexts 相似文献
154.
Using AuGeNiCr multilayered metals as the wafer bonding medium, long-wavelength GaInAsP/InP vertical cavity surface emitting lasers employing Al-oxide/Si as the upper and lower distributed Bragg reflectors were fabricated on Si substrate with the bonding interface formed outside the vertical cavity surface emitting laser cavity. Laser emission at 1.545 μm was measured under pulsed operations near room temperature. The low-temperature metallic bonding process demonstrates a great potential in device fabrication 相似文献
155.
Wang J.R. Racette P. Tiesky M.E. Manning W. 《Geoscience and Remote Sensing, IEEE Transactions on》2002,40(6):1220-1229
The airborne Millimeter-wave Imaging Radiometer (MIR) measurements conducted over the Midwest region of the continental United States during January/February 1997 and over the Alaska-Arctic region during May 1998 are used to estimate column water vapor W<0.8 g/cm/sup 2/ under a clear sky. On board the same aircraft are two other instruments, the Cloud Lidar System (CLS) and MODerate-resolution Imaging Spectrometer (MODIS) Airborne Simulator (MAS), which provide cloud cover information and independent measurements of W, respectively. The MIR-estimated W values are compared and found to be in very good agreement with those measured by rawinsondes at near concurrence. A close correlation is found between the MIR-estimated W and that estimated from the MAS near-IR reflectance ratios. Water surface emissivities at several MIR frequencies are obtained in the process of the W retrieval from several flights over the Midwest lakes. These estimated emissivities compared favorably with values calculated for a calm water surface, which are based on a di-electric permittivity model and MAS-measured surface temperatures. The results from all comparisons strongly demonstrate the soundness of the technique for estimating W. 相似文献
156.
Development of a recurrent Sigma-Pi neural network rainfall forecasting system in Hong Kong 总被引:1,自引:1,他引:0
At the moment, weather forecasting is still an art — the experience and intuition of forecasters play a significant role in determining the quality of forecasting. This paper describes the development of a new approach to rainfall forecasting using neural networks. It deals with the extraction of information from radar images and an evaluation of past rain gauge records to provide shortterm rainfall forecasting. All of the meteorological data were provided by the Royal Observatory of Hong Kong (ROHK). Preprocessing procedures were essential for this neural network rainfall forecasting. The forecast of the rainfall was performed every half an hour so that a storm warning signal can be delivered to the public in advance. The network architecture is based on a recurrent Sigma-Pi network. The results are very promising, and this neural-based rainfall forecasting system is capable of providing a rain storm warning signal to the Hong Kong public one hour ahead. 相似文献
157.
Sun J. Gardner M.K. Liu J.W.S. 《IEEE transactions on pattern analysis and machine intelligence》1997,23(10):603-615
The workload of many real time systems can be characterized as a set of preemptable jobs with linear precedence constraints. Typically their execution times are only known to lie within a range of values. In addition, jobs share resources and access to the resources must be synchronized to ensure the integrity of the system. The paper is concerned with the schedulability of such jobs when scheduled on a priority driven basis. It describes three algorithms for computing upper bounds on the completion times of jobs that have arbitrary release times and priorities. The first two are simple but do not yield sufficiently tight bounds, while the last one yields the tightest bounds but has the greatest complexity 相似文献
158.
159.
Recent observations at operating plants and subsequent US NRC requirements have identified flow stratification in surge lines as a phenomenon that must be considered in the design basis of surge lines. To address these concerns, the stratified loading conditions were included in the design of YGN 3 and 4 surge line as a design basis transient and pipe temperature and displacement measurement were taken during YGN 3 pre-core hot functional testing to determine the degree of surge line flow stratification. The measured displacements and temperatures were extensively reviewed and evaluated in detail: (1) to verify the validity of the thermal hydraulic model used to predict the pipe top-to-bottom temperature differentials; (2) to analytically correlate measured surge line temperatures and displacements; and (3) to confirm the validity of the stratified flow analysis procedure. This paper shows that the stratified flow phenomenon is generic and therefore generic loadings can be developed and evaluated for the surge line analyses. 相似文献
160.
A study was undertaken to determine fertility in a group of females who as children had been operated on for appendicitis. The 134 women operated on for appendicitis were reviewed. Their ages ranged from 2-18 years at the time of appendectomy. Our data show that perforated appendicitis before puberty has little if any role in the etiology of tubal infertility. 相似文献