全文获取类型
收费全文 | 145300篇 |
免费 | 24438篇 |
国内免费 | 7218篇 |
专业分类
电工技术 | 9543篇 |
技术理论 | 5篇 |
综合类 | 9600篇 |
化学工业 | 31920篇 |
金属工艺 | 6386篇 |
机械仪表 | 7644篇 |
建筑科学 | 10793篇 |
矿业工程 | 3444篇 |
能源动力 | 4013篇 |
轻工业 | 16943篇 |
水利工程 | 3061篇 |
石油天然气 | 4679篇 |
武器工业 | 1220篇 |
无线电 | 19096篇 |
一般工业技术 | 21580篇 |
冶金工业 | 4630篇 |
原子能技术 | 1310篇 |
自动化技术 | 21089篇 |
出版年
2024年 | 697篇 |
2023年 | 2229篇 |
2022年 | 4338篇 |
2021年 | 5923篇 |
2020年 | 5512篇 |
2019年 | 6287篇 |
2018年 | 6369篇 |
2017年 | 7059篇 |
2016年 | 7066篇 |
2015年 | 8722篇 |
2014年 | 9833篇 |
2013年 | 11474篇 |
2012年 | 10495篇 |
2011年 | 10598篇 |
2010年 | 9979篇 |
2009年 | 9504篇 |
2008年 | 8977篇 |
2007年 | 8302篇 |
2006年 | 7574篇 |
2005年 | 6006篇 |
2004年 | 5027篇 |
2003年 | 4812篇 |
2002年 | 5349篇 |
2001年 | 4512篇 |
2000年 | 3274篇 |
1999年 | 2069篇 |
1998年 | 972篇 |
1997年 | 834篇 |
1996年 | 664篇 |
1995年 | 554篇 |
1994年 | 437篇 |
1993年 | 320篇 |
1992年 | 269篇 |
1991年 | 204篇 |
1990年 | 154篇 |
1989年 | 114篇 |
1988年 | 105篇 |
1987年 | 62篇 |
1986年 | 64篇 |
1985年 | 20篇 |
1984年 | 18篇 |
1983年 | 12篇 |
1982年 | 27篇 |
1981年 | 19篇 |
1980年 | 52篇 |
1979年 | 21篇 |
1978年 | 9篇 |
1977年 | 4篇 |
1959年 | 6篇 |
1951年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
81.
J. Weise Dr.‐Ing. O. Yezerska M. Busse M. Haesche V. Zanetti‐Bueckmann M. Schmitt 《Materialwissenschaft und Werkstofftechnik》2007,38(11):901-906
Micro‐porous syntactic foams were produced by means of integration of glass bubbles into aluminium and zinc matrices. Preforms of glass bubbles were pressure infiltrated with the alloys AlSi9Cu9 ans ZnAl4Cu using squeeze casting. The preforms were sintered thermically without the use of bonding agents. Using the combination of different sintering steps syntactic foams with locally different densities could be produced. The mechanical properties of the foams were tested indicating a high compression strength of the foams and a very good compression energy absorption. Furthermore, corrosion behaviour and behaviour at higher temperatures were investigated. 相似文献
82.
We define the very rich language of composed conditionals on a three‐valued logic and use this language as the communication tool between man and machine. Communication takes place for three reasons: knowledge acquisition, query, and response. Learning, thinking, and answering questions are of a pure information theoretical nature. The pivot of this knowledge processing concept is the amount of information (bit) we receive if a conditional becomes true. We follow an axiomatic approach to information theory rather than the classical probabilistic approach of Shannon; information comes first, and then comes probability. In the light of this philosophy, query and response experience new interpretations. Both, acquisition and response are realized by maximizing entropy and minimizing relative entropy, respectively. The iterative solution of these mathematical optimization problems gives new insights into the adaptation of prior knowledge to new information. Our expert system shell SPIRIT supports this kind of knowledge processing, which will be established by suitable examples. © 2003 Wiley Periodicals, Inc. 相似文献
83.
Wood has long traditions as a building material, and is often used in construction elements, and as interior and exterior surfaces in the Nordic countries. In most applications, there are reaction to fire requirements to products used as surfaces, e.g. in escape routes and larger public spaces. Most wood products will therefore have to be treated with fire retardant (FR) agents to fulfil the strict requirements to properties connected to heat release and flame spread. Unfortunately, FR agents usually also increase the smoke production, as they cause a more incomplete combustion of the wood. The wood product manufacturers seek to find the optimal amount of FR additives where both heat release and smoke production in the classifying test are within the requirements given in the building regulations. This paper describes models for prediction of the European reaction to fire classes of wood products. The models are based on multivariate statistical analysis, and use test results from the cone calorimeter test as input. The presented models are, with very good precision, able to predict which Euroclass and additional smoke class a wood based product would obtain if it were to be tested in the single burning item test. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
84.
创业家与企业家的相关内涵思辨 总被引:2,自引:0,他引:2
学术界和实践界对entrepreneur和entrepreneurship的内涵界定不清晰,缺少概念基础,从而限制了《创业学》的发展。分析了创业与创新的本质;区别了活跃在企业创立和成长阶段、致力于创造生产函数的创业家和扮演“权威”、致力于改变函数自变量的企业家;界定了在不同语境中创业家与企业家的含义。最后,强调了需要根据上下文来判断它们的内涵。 相似文献
85.
86.
本文在[1]的基础上,详尽地得到了Boussinesq方程和KdV方程的孤立波解,并对波高和波形进行了细致的分析。为了更好地比较,本文还给出了高阶摄动的孤立波解。 相似文献
87.
重大技术装备的制造水平是一个国家综合实力的直接体现,因此从上个世纪八十年代初开始,历届国务院领导人均兼任国家重大技术装备领导小组组长,通过推进重大技术装备的发展,促进 相似文献
88.
89.
90.
Designing circuits with partial scan 总被引:1,自引:0,他引:1
Agrawal V.D. Kwang-Ting Cheng Johnson D.D. Sheng Lin T. 《Design & Test of Computers, IEEE》1988,5(2):8-15
In this scan design methodology, only selected faults are targeted for detection. These faults are those not detected by the designer's functional vectors. The test generator decides exactly which flip-flops should be scanned using one of two methods. In the first method, all possible tests are generated for each target fault, and the set of tests requiring the fewest flip-flops is selected. In the second method, only one test is generated for each fault, and the use of flip-flops is avoided as much as possible during test generation. Examples of actual VLSI circuits show a savings of at least a 40% in full-scan overhead 相似文献