全文获取类型
收费全文 | 215394篇 |
免费 | 25670篇 |
国内免费 | 25153篇 |
专业分类
电工技术 | 19527篇 |
技术理论 | 9篇 |
综合类 | 14483篇 |
化学工业 | 48779篇 |
金属工艺 | 8986篇 |
机械仪表 | 12683篇 |
建筑科学 | 9417篇 |
矿业工程 | 2442篇 |
能源动力 | 6435篇 |
轻工业 | 18334篇 |
水利工程 | 2706篇 |
石油天然气 | 5969篇 |
武器工业 | 2049篇 |
无线电 | 32595篇 |
一般工业技术 | 22316篇 |
冶金工业 | 4715篇 |
原子能技术 | 3174篇 |
自动化技术 | 51598篇 |
出版年
2024年 | 1129篇 |
2023年 | 3945篇 |
2022年 | 8252篇 |
2021年 | 9208篇 |
2020年 | 7655篇 |
2019年 | 6951篇 |
2018年 | 6521篇 |
2017年 | 8682篇 |
2016年 | 9491篇 |
2015年 | 10725篇 |
2014年 | 10729篇 |
2013年 | 14009篇 |
2012年 | 15929篇 |
2011年 | 17880篇 |
2010年 | 12855篇 |
2009年 | 12849篇 |
2008年 | 13983篇 |
2007年 | 15414篇 |
2006年 | 14617篇 |
2005年 | 12478篇 |
2004年 | 10507篇 |
2003年 | 8319篇 |
2002年 | 6426篇 |
2001年 | 4868篇 |
2000年 | 4061篇 |
1999年 | 3407篇 |
1998年 | 2808篇 |
1997年 | 2250篇 |
1996年 | 1798篇 |
1995年 | 1551篇 |
1994年 | 1333篇 |
1993年 | 1010篇 |
1992年 | 832篇 |
1991年 | 677篇 |
1990年 | 580篇 |
1989年 | 417篇 |
1988年 | 327篇 |
1987年 | 207篇 |
1986年 | 221篇 |
1985年 | 250篇 |
1984年 | 218篇 |
1983年 | 163篇 |
1982年 | 208篇 |
1981年 | 115篇 |
1980年 | 114篇 |
1979年 | 50篇 |
1978年 | 25篇 |
1977年 | 29篇 |
1976年 | 19篇 |
1975年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
For the first time, order-order and order-disorder transitions were detected and characterized in a model diblock copolymer of poly(butadiene-1,3) and poly(dimethylsiloxane) (PB-b-PDMS). This model PB-b-PDMS copolymer was synthesized by the sequential anionic polymerization (high vacuum techniques) of butadiene 1,3 (B) and hexamethylciclotrisiloxane (D3), and subsequently characterized by nuclear magnetic resonance (1H and 13C NMR), size exclusion chromatography (SEC), Fourier Transform infrared spectroscopy (FTIR), Small-Angle X-ray scattering (SAXS) and rheology. SAXS combined with rheological experiments shows that the order-order and order-disorder transitions are thermoreversible. This fact indicates that the copolymer has sufficient mobility at the timescale and at the temperatures of interest to reach their equilibrium morphologies. 相似文献
92.
The present study is an investigation on the behaviors of concrete-filled thin-walled steel tubular members subjected to combined loading, such as compression and torsion, bending and torsion, compression, bending and torsion. ABAQUS software is used in this paper for the finite element analysis (FEA). A comparison of results calculated using this modeling shows generally good agreement with test results. The FEA modeling is then used to investigate the influence of important parameters that determine the ultimate strength of the composite members under combined loading, such as compression and torsion, bending and torsion, compression, bending and torsion. The parametric studies provide information for the development of formulae for calculating the ultimate strength of the composite members subjected to combined loading. 相似文献
93.
Lean philosophy: implementation in a forging company 总被引:2,自引:2,他引:0
Ajit Kumar Sahoo N. K. Singh Ravi Shankar M. K. Tiwari 《The International Journal of Advanced Manufacturing Technology》2008,36(5-6):451-462
This research addresses the implementation of lean philosophy in a forging company with a focus on radial forging production
flow lines. Here, the prime motive is to evolve and test several strategies to eliminate waste on the shop floor. In this
research, a systematic approach is suggested for the implementation of lean principles. This paper describes an application
of value stream mapping (VSM). Consequently, the present and future states of value stream maps are constructed to improve
the production process by identifying waste and its sources. Furthermore, Taguchi’s method of design of experiments is pursued
here to minimize the forging defects produced due to imperfect operating conditions. A noticeable reduction in set-up time
and work-in-process (WIP) inventory level is substantiated. Finally, we conclude with a discussion of managerial implications
and the future scope of research. 相似文献
94.
Die Regelung über die Erlangung der Parteistellung übergangener Nachbarn durch Geltendmachung von Einwendungen bis l?ngstens
drei Monate nach dem angezeigten Baubeginn ist wegen der Anknüpfung an einen untauglichen Zeitpunkt verfassungswidrig. 相似文献
95.
Chris Harty 《Building Research & Information》2005,33(6):512-522
An alternative approach to understanding innovation is made using two intersecting ideas. The first is that successful innovation requires consideration of the social and organizational contexts in which it is located. The complex context of construction work is characterized by inter-organizational collaboration, a project-based approach and power distributed amongst collaborating organizations. The second is that innovations can be divided into two modes: 'bounded', where the implications of innovation are restricted within a single, coherent sphere of influence, and 'unbounded', where the effects of implementation spill over beyond this. Bounded innovations are adequately explained within the construction literature. However, less discussed are unbounded innovations, where many firms' collaboration is required for successful implementation, even though many innovations can be considered unbounded within construction's inter-organizational context. It is argued that unbounded innovations require an approach to understand and facilitate the interactions both within a range of actors and between the actors and technological artefacts. The insights from a sociology of technology approach can be applied to the multiplicity of negotiations and alignments that constitute the implementation of unbounded innovation. The utility of concepts from the sociology of technology, including 'system building' and 'heterogeneous engineering', is demonstrated by applying them to an empirical study of an unbounded innovation on a major construction project (the new terminal at Heathrow Airport, London, UK). This study suggests that 'system building' contains outcomes that are not only transformations of practices, processes and systems, but also the potential transformation of technologies themselves. 相似文献
96.
97.
单微乳液中制备Ag/TS-1及丙烯气相环氧化 总被引:2,自引:0,他引:2
采用N2H4还原含AgNO3的单微乳液制备了Ag/TS-1催化剂。TEM表征结果表明,Ag高度分散于TS-1之上。以H2、O2存在下的丙烯气相环氧化为探针反应,考察了Ag/TS-1的催化性能。结果表明,采用Ag/TS-1为催化剂,Ag的负载量为1%(质量分数,下同),823 K焙烧后,373 K下反应30 min时,丙烯转化率为1.69%,环氧丙烷(Propylene oxide,PO)选择性为93.2%。当Ag的负载量超过2%时,反应过程中生成大量的热,造成PO的选择性下降。采用Ag的负载量为8%的Ag/TS-1催化剂,消除热效应后,丙烯的转化率为2.46%.PO的选择性为79.2%。 相似文献
98.
波分复用系统将不同波长的光复用在一起进行传输,以满足对传输容量和传输距离的各种需求。介绍了一种开销监视与提取的设计方法,使用VSC8150提取承载在波分复用系统相应波长上SDH信号的开销。分析了VSC8150的工作原理,管脚和外部接口,以及与FPGA、单片机共同完成B1重新计算,开销提取,B1,J0提取。此外,还提出将帧丢失,帧失步等错误状态传送给单片机和网管的方法。本设计增强了波分复用系统网管管理参数,功能和灵活性,这会在系统维护时带来较大的方便。该设计已经成熟应用在实际的波分复用系统中。 相似文献
99.
R. A. Borzooei M. Bakhshi M. Mashinchi 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2008,12(8):739-749
In this paper, we study the lattice structure of some fuzzy algebraic systems such as (G-)fuzzy groups, some fuzzy ordered
algebras and fuzzy hyperstructures. We prove that under suitable conditions, these structures form a distributive or modular
lattice.
This research partially is supported by the “ Fuzzy Systems and its Applications Center of Excelence, Shahid Bahonar University
of Kerman, Iran”. 相似文献
100.
沸石孔结构对1-己烯异构化性能的影响 总被引:1,自引:0,他引:1
采用1-己烯为原料,对硅铝比相近、不同孔结构的沸石在脉冲微反装置上进行了评价试验,考察了FCC条件下沸石孔结构对烯烃异构化性能的影响。结果表明,大孔径的Y型沸石具有良好的异构化性能,异构化能力由强到弱的排列顺序为Y>β>ZRP>丝光沸石>镁碱沸石。 相似文献