全文获取类型
收费全文 | 1454篇 |
免费 | 9篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 19篇 |
综合类 | 2篇 |
化学工业 | 228篇 |
金属工艺 | 25篇 |
机械仪表 | 39篇 |
建筑科学 | 59篇 |
矿业工程 | 10篇 |
能源动力 | 30篇 |
轻工业 | 130篇 |
水利工程 | 9篇 |
石油天然气 | 6篇 |
无线电 | 125篇 |
一般工业技术 | 209篇 |
冶金工业 | 402篇 |
原子能技术 | 10篇 |
自动化技术 | 162篇 |
出版年
2022年 | 9篇 |
2021年 | 13篇 |
2019年 | 12篇 |
2018年 | 13篇 |
2016年 | 14篇 |
2015年 | 9篇 |
2014年 | 20篇 |
2013年 | 46篇 |
2012年 | 30篇 |
2011年 | 43篇 |
2010年 | 29篇 |
2009年 | 29篇 |
2008年 | 41篇 |
2007年 | 49篇 |
2006年 | 26篇 |
2005年 | 36篇 |
2004年 | 26篇 |
2003年 | 34篇 |
2002年 | 25篇 |
2001年 | 24篇 |
2000年 | 29篇 |
1999年 | 33篇 |
1998年 | 136篇 |
1997年 | 95篇 |
1996年 | 45篇 |
1995年 | 39篇 |
1994年 | 36篇 |
1993年 | 36篇 |
1992年 | 19篇 |
1991年 | 17篇 |
1990年 | 12篇 |
1989年 | 12篇 |
1988年 | 18篇 |
1987年 | 16篇 |
1986年 | 13篇 |
1985年 | 33篇 |
1984年 | 17篇 |
1983年 | 15篇 |
1982年 | 18篇 |
1981年 | 14篇 |
1980年 | 16篇 |
1979年 | 18篇 |
1978年 | 25篇 |
1977年 | 26篇 |
1976年 | 37篇 |
1975年 | 15篇 |
1974年 | 18篇 |
1973年 | 13篇 |
1972年 | 15篇 |
1944年 | 9篇 |
排序方式: 共有1465条查询结果,搜索用时 15 毫秒
41.
W. D. Goodhue K. Rauschenbach C. A. Wang J. P. Donnelly R. J. Bailey G. D. Johnson 《Journal of Electronic Materials》1990,19(5):463-469
Chlorine ion-beam-assisted etching (IBAE) has been used to micromachine laser facets and deflecting mirrors for monolithic
two-dimensional GaAs/AIGaAs laser arrays. Three laser cavity/deflector designs have been successfully implemented. The first
utilizes a parabolic deflecting mirror to directly focus the laser radiation; the second consists of a folded cavity with
a vertical facet, a top surface facet, and an internal 45° reflector; and the third has a folded cavity with an internal Al0.2Ga0.8As/Al0.8Ga0.2As dielectric mirror stack and a top surface facet formed in a single etch step with two internal 45° reflectors. The parabolic
deflecting mirrors are currently modeled forf- 0.8 collection efficiency, making the first design attractive in incoherent arrays for high-power applications such as pumping
Nd:YAG lasers. The other two structures are of interest for incoherent or coherent arrays used in high- and medium-power applications,
since the top surface facets can easily be antireflection coated. The design with a dielectric mirror stack is particularly
simple to fabricate. 相似文献
42.
This paper presents an integrative application of several numerical analytical techniques and associated analysis tools for design optimization and damage prediction in electronics packages and microsystems. This design-for-reliability approach is based on four different types of numerical techniques that allow (1) high-fidelity modelling, (2) reduced order modelling, (3) numerical optimization and (4) uncertainty analysis. The capabilities and the characteristics of the methods that underpin these four types of modelling and analysis tools are firstly investigated. The integration of the methods and tools is then examined and a methodology for coupling the tools in an optimization process is proposed. This numerical methodology involves the following steps: (1) Define sampling points for the design of interest by design of experiments (DOE) and calculate the design response at each DOE point using high-fidelity analysis; (2) construct reduced order models (ROM) for fast analysis using the obtained response values at the DOE points; (3) Undertake deterministic optimization in the defined design space by ROM; and (4) Probabilistic optimization by including variation and uncertainty of the design in the optimization task. This approach is suitable to address design-for-reliability requirements at early design stages in a wide range of application areas. The application of this approach is demonstrated in a case for minimizing the thermal fatigue damage of flip-chip solder interconnects. Design modifications show that this approach can provide improved reliability of the package and in the same time satisfy a number of design requirements. 相似文献
43.
Dhinsa K. Bailey C. Pericleous K. 《Components and Packaging Technologies, IEEE Transactions on》2005,28(4):686-699
Heat is extracted away from an electronic package by convection, conduction, and/or radiation. The amount of heat extracted by forced convection using air is highly dependent on the characteristics of the airflow around the package which includes its velocity and direction. Turbulence in the air is also important and is required to be modeled accurately in thermal design codes that use computational fluid dynamics (CFD). During air cooling the flow can be classified as laminar, transitional, or turbulent. In electronics systems, the flow around the packages is usually in the transition region, which lies between laminar and turbulent flow. This requires a low-Reynolds number numerical model to fully capture the impact of turbulence on the fluid flow calculations. This paper provides comparisons between a number of turbulence models with experimental data. These models included the distance from the nearest wall and the local velocity (LVEL), Wolfshtein, Norris and Reynolds, k-/spl epsiv/, k-/spl omega/, shear-stress transport (SST), and k/spl epsiv//kl models. Results show that in terms of the fluid flow calculations most of the models capture the difficult wake recirculation region behind the package reasonably well, although for packages whose heights cause a high degree of recirculation behind the package the SST model appears to struggle. The paper also demonstrates the sensitivity of the models to changes in the mesh density; this study is aimed specifically at thermal design engineers as mesh independent simulations are rarely conducted in an industrial environment. 相似文献
44.
In the reliability theme a central activity is to investigate, characterize and understand the contributory wear-out and overstress mechanisms to meet through-life reliability targets. For power modules, it is critical to understand the response of typical wear-out mechanisms, for example wire-bond lifting and solder degradation, to in-service environmental and load-induced thermal cycling. This paper presents the use of a reduced-order thermal model coupled with physics-of-failure-based life models to quantify the wear-out rates and life consumption for the dominant failure mechanisms under prospective in-service and qualification test conditions. When applied in the design of accelerated life and qualification tests it can be used to design tests that separate the failure mechanisms (e.g. wire-bond and substrate-solder) and provide predictions of conditions that yield a minimum elapsed test time. The combined approach provides a useful tool for reliability assessment and estimation of remaining useful life which can be used at the design stage or in-service. An example case study shows that it is possible to determine the actual power cycling frequency for which failure occurs in the shortest elapsed time. The results demonstrate that bond-wire degradation is the dominant failure mechanism for all power cycling conditions whereas substrate-solder failure dominates for externally applied (ambient or passive) thermal cycling. 相似文献
45.
A Recursive Algorithm for Computing Exact Reliability Measures 总被引:1,自引:0,他引:1
An algorithm is presented to find source-to-K-terminal reliability in a directed graph with independent arc failures. The algorithm is based on a discrete-time Markov chain with two absorbing states. The Markov chain has an upper triangular transition probability matrix, thus the probability of absorption in a state can be found by back-substitution. We show: 1) The source-to-K-terminal reliability is the probability of absorption in a particular absorbing state; 2) The time until absorption can be used as an alternative reliability measure; and 3) The algorithm can be used to find a third reliability measure called the degree of connectedness. 相似文献
46.
P. Kerkoc R. T. Bailey F. R. Cruickshank D. Pugh J. N. Sherwood 《Journal of Modern Optics》2013,60(5):903-912
Abstract Pulsed laser induced surface damage experiments were made on the cleaved (001) face of (—)2-(α-methylbenzylamino)-5-nitropyridine (MBANP) crystals using a pulse length of 25 ns FWHM. The highest single pulse damage threshold value was 24·2 J cm?2 at a wavelength of 1064 nm for light polarized along the crystallographic a axis, whereas the lowest was 1·8 J cm?2 at 532 nm for light polarized along the crystallographic b axis. The extent of the mechanical distortion of the (001) crystal plane consequent upon the absorption of a 25 ns FWHM, 10 J cm?2 pulse from a Nd:YAG laser operating at the wavelength 1064 nm has been measured by a non-destructive and non-invasive technique. 相似文献
47.
Jens Georg Kaufmann Marc P. Y. Desmulliez Yingtao Tian Dennis Price Mike Hughes Nadia Strusevich Chris Bailey Changqing Liu David Hutt 《Microsystem Technologies》2009,15(8):1245-1254
In this paper we propose an agitation method based on megasonic acoustic streaming to overcome the limitations in plating
rate and uniformity of the metal deposits during the electroplating process. Megasonic agitation at a frequency of 1 MHz allows
the reduction of the thickness of the Nernst diffusion layer to less than 600 nm. Two applications that demonstrate the benefits
of megasonic acoustic streaming are presented: the formation of uniform ultra-fine pitch flip-chip bumps and the metallisation
of high aspect ratio microvias. For the latter application, a multi-physics based numerical simulation is implemented to describe
the hydrodynamics introduced by the acoustic waves as they travel inside the deep microvias. 相似文献
48.
V.Sh. Shagapov N.S. Khabeev S.S. Bailey 《International Journal of Heat and Mass Transfer》2004,47(4):843-851
Processes, occurring during exploration of gas-oil wells in frozen rock are simulated. A system of differential equations, describing hydro and thermal dynamics of an ascending two-phase flow of a hydrocarbon system in a vertical channel taking into account phase transitions and structure of a flow is developed. Kinetics of paraffin deposits on internal walls of an elevating column of a well are considered. The effect of the heat exchange of a well within frozen rock is developed using differential equations that describe the evolution of the radius of thermal influence of the well and the radius of the melting zone. We conclude with numerical research of some preventive ways of dealing with paraffin deposits. 相似文献
49.
Kong Bailey Supanc̆ic̆ James Ramanan Deva Fowlkes Charless C. 《International Journal of Computer Vision》2019,127(11-12):1738-1750
International Journal of Computer Vision - We investigate the problem of automatically determining what type of shoe left an impression found at a crime scene. This recognition problem is made... 相似文献
50.