全文获取类型
收费全文 | 164089篇 |
免费 | 11495篇 |
国内免费 | 5935篇 |
专业分类
电工技术 | 7719篇 |
技术理论 | 7篇 |
综合类 | 14463篇 |
化学工业 | 18920篇 |
金属工艺 | 10019篇 |
机械仪表 | 15886篇 |
建筑科学 | 34210篇 |
矿业工程 | 4790篇 |
能源动力 | 3840篇 |
轻工业 | 6637篇 |
水利工程 | 4137篇 |
石油天然气 | 5164篇 |
武器工业 | 2049篇 |
无线电 | 8991篇 |
一般工业技术 | 21971篇 |
冶金工业 | 4284篇 |
原子能技术 | 780篇 |
自动化技术 | 17652篇 |
出版年
2024年 | 468篇 |
2023年 | 1742篇 |
2022年 | 2961篇 |
2021年 | 3938篇 |
2020年 | 4164篇 |
2019年 | 3339篇 |
2018年 | 3232篇 |
2017年 | 4180篇 |
2016年 | 4688篇 |
2015年 | 4892篇 |
2014年 | 11048篇 |
2013年 | 9080篇 |
2012年 | 11615篇 |
2011年 | 12362篇 |
2010年 | 10359篇 |
2009年 | 10775篇 |
2008年 | 9424篇 |
2007年 | 11722篇 |
2006年 | 10102篇 |
2005年 | 8779篇 |
2004年 | 7048篇 |
2003年 | 6626篇 |
2002年 | 5336篇 |
2001年 | 4561篇 |
2000年 | 3772篇 |
1999年 | 2972篇 |
1998年 | 2427篇 |
1997年 | 2044篇 |
1996年 | 1713篇 |
1995年 | 1371篇 |
1994年 | 1098篇 |
1993年 | 833篇 |
1992年 | 606篇 |
1991年 | 509篇 |
1990年 | 310篇 |
1989年 | 285篇 |
1988年 | 224篇 |
1987年 | 161篇 |
1986年 | 86篇 |
1985年 | 107篇 |
1984年 | 135篇 |
1983年 | 86篇 |
1982年 | 104篇 |
1981年 | 32篇 |
1980年 | 52篇 |
1979年 | 35篇 |
1978年 | 13篇 |
1977年 | 13篇 |
1959年 | 11篇 |
1951年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
991.
Domenico Ferrari 《Multimedia Systems》1998,6(3):179-185
The research done by the Tenet Group in multimedia networking has reached a point where it may be useful to reflect on the
significance of its results for the current debate on how integrated-services internetworks should be designed. Such reflections
constitute the main subject of this paper. The principles of the work and the conclusions reached so far by the Tenet researchers
are discussed in the light of the conflict between the two major technologies being proposed to build future information infrastructures:
namely, the Internet and the ATM technologies. The Tenet approach suggests one feasible way for resolving the conflict to
the advantage of all the users of those infrastructures. This paper discusses various fundamental aspects of integrated-services
network design: the choice of the service model, the type of charging policy to be adopted, and the selection of a suitable
architecture. 相似文献
992.
随着交换技术的飞速发展,程控交换软件的规模越来越大,改动也越来越频繁,如何使代码对数据的改动具有相对的稳定性成为程控软件设计的一个首要问题。本文以CCS7(7号公共信道信令)为例,从对象模型、动态模型、功能模型3个方面阐述了OO(面向对象)方法在CCS7软件设计中的应用。这一方法,也可应用于程控软件的设计。 相似文献
993.
Interfaces play an important role in determining the mechanical properties of composite materials. The interfaces established between a titanium-alloy matrix (Ti-6Al-4V) and uncoated and TiB2/C-coated SiC fibres are analysed by scanning electron microscopy, transmission electron microscopy and X-ray techniques. Emphasis is placed upon the interfacial morphology and microstructure, identification of reaction products, and the stability of the coating layer. Complex multi-reaction layers are observed frequently in the interfacial zones. Previous, often contradictory, reports about the interlayers are reviewed. Experimental observation demonstrates that the type and distribution of interlayers vary in a given system, due to prolonged treatment of the samples at temperature. The formation and distribution of the interlayers are discussed further, with respect to these and previous findings. Methods of reducing interfacial reactivity are discussed. 相似文献
994.
Optimal and Suboptimal Quadriphase Sequences Derived from Maximal Length Sequences over Z
_{{\bf 4}}
P. Udaya M.U. Siddiqi 《Applicable Algebra in Engineering, Communication and Computing》1998,9(2):161-191
The paper presents families of quadriphase sequences derived from maximal length sequences over having good correlation properties. These are: (i) families of quadriphase sequences of period from maximal length sequences over ; each family consisting of sequences, (ii) families of quadriphase sequences of period from interleaved maximal length sequences over ; each family consisting of sequences. Such sequences are of interest in quadriphase modulated code division multiple access communication systems,
where it is desirable to have large sets of sequences that possess low value of , the maximum magnitude of the periodic crosscorrelation and out of phase auto-correlation values. The sequences over are viewed as trace functions of appropriately chosen unit elements of Galois extension rings of . Quadriphase sequences are then obtained from sequences, by a quadriphase mapping, , from to roots of unity, given by, ; where and . Periodic correlation properties (correlation values and their distribution) of the quadriphase sequences are obtained by
using an Abelian association scheme on the elements of the corresponding Galois extension ring of . The majority of the families of sequences derived are optimal with respect to the Welch lower bound on ; the rest being suboptimal with bounded by , where is the period\newpage of the sequences. However nearly half of the sequences in these families are balanced.
Received July 18, 1995; revised version November 29, 1996 相似文献
995.
The complexity of current engineering design demands the collaboration of specialists. Collaboration involves both communication between and coordination among members of a design team. Currently, design collaboration is carried out through the use of schedules, specifications and drawings which only capture the end results of the design process. They fail to record important design information such as the reasoning behind design decisions. In this paper, we describe a tool CADS, that supports collaboration in engineering design. CADS is based on an extension to the Axiomatic Design methodology which not only captures the design elements but also the rationale used to conceive them. CADS serves as a shared database of design information with facilities that support communication and coordination in engineering design.Currently at the Media Laboratory, MIT. 相似文献
996.
D. Scida Z. Aboura M.L. Benzeggagh E. Bocherens 《Composites Science and Technology》1998,57(12):2733-1740
A micromechanical model called MESOTEX is presented for prediction of the elastic behaviour of composites reinforced with non-hybrid weave (plain weave, satin weave and twill weave) and hybrid weave (hybrid plain weave and hybrid twill weave) fabrics. By using the classical thin laminate theory applied to each woven structure, this analytical model takes into account the strand undulations in the two directions and also integrates the geometrical and mechanical parameters of each constituent (resin, fill and warp strands). A representative volume is chosen for each woven composite and the fibre architecture is described by several functions. To determine the effectiveness of this analysis, the elastic properties predicted for each woven composite are compared with experimental results and results extracted from the literature. This correlation shows excellent agreement between measured and predicted values, with a very low calculation cost (CPU time of less than 0·01 s). 相似文献
997.
Experimental studies have been performed on ceramic matrix composite (CMC) I-sections, which typify joint designs for CMC components. Axial loads and moments have been applied to activate delamination mechanisms. The maximum load bearing capacity has large variability, governed by the severity of manufacturing flaws located in the transition region of the I-section. This variability leads to an unsatisfactory design situation. Delaminations that form from these flaws arrest and behave in a stable manner, subject to a remanent load bearing capacity. This remanent capacity has minimal variability. Hence, design based on the remanent load would be robust. An expression for this design criterion is presented. 相似文献
998.
张丹凤 《数码设计:surface》2012,(6):126-127
本文从产品设计在情感化产品中的造型语言入手,从本能情感、行为情感和反思情感三方面具体阐述了情感化的造型语言在现代产品设计中的体现形式,旨在让人们对于产品的造型语言有更加深入清晰的认识,更好的实现工业产品的人性化设计。 相似文献
999.
两栖装甲装备故障诊断智能检测系统设计 总被引:3,自引:0,他引:3
针对目前两栖装甲装备故障检测时间长、检测效率低的缺点,研究设计了一种两栖装甲装备故障诊断智能检测系统。系统充分利用现代最新发展的大规模集成电路技术和数字处理技术,对多发、易发故障部位的故障信号进行采样、检测及处理,从而快速确定故障部位,便于及时排除故障。 相似文献
1000.
韩艳 《数码设计:surface》2012,(9):111-113
文章试图还原西方社会在1900~1939年这一特殊阶段的历史真实,分析当时的服装设计与现代艺术的相互关系及其所反映的文化内涵,提出服装设计师在设计实践中,应关注社会思潮、艺术等方方面面,从时代的艺术中获得灵感,最大可能地发挥想象力及创造力。 相似文献