全文获取类型
收费全文 | 3187篇 |
免费 | 31篇 |
专业分类
电工技术 | 20篇 |
综合类 | 52篇 |
化学工业 | 243篇 |
金属工艺 | 24篇 |
机械仪表 | 53篇 |
建筑科学 | 78篇 |
矿业工程 | 3篇 |
能源动力 | 34篇 |
轻工业 | 157篇 |
水利工程 | 22篇 |
石油天然气 | 14篇 |
无线电 | 141篇 |
一般工业技术 | 232篇 |
冶金工业 | 1991篇 |
原子能技术 | 7篇 |
自动化技术 | 147篇 |
出版年
2022年 | 8篇 |
2021年 | 21篇 |
2020年 | 13篇 |
2019年 | 18篇 |
2018年 | 24篇 |
2017年 | 15篇 |
2016年 | 26篇 |
2015年 | 30篇 |
2014年 | 46篇 |
2013年 | 61篇 |
2012年 | 57篇 |
2011年 | 82篇 |
2010年 | 59篇 |
2009年 | 48篇 |
2008年 | 67篇 |
2007年 | 62篇 |
2006年 | 48篇 |
2005年 | 51篇 |
2004年 | 44篇 |
2003年 | 34篇 |
2002年 | 32篇 |
2001年 | 33篇 |
2000年 | 31篇 |
1999年 | 86篇 |
1998年 | 549篇 |
1997年 | 336篇 |
1996年 | 222篇 |
1995年 | 156篇 |
1994年 | 132篇 |
1993年 | 144篇 |
1992年 | 45篇 |
1991年 | 48篇 |
1990年 | 53篇 |
1989年 | 51篇 |
1988年 | 36篇 |
1987年 | 39篇 |
1986年 | 35篇 |
1985年 | 30篇 |
1984年 | 14篇 |
1983年 | 15篇 |
1982年 | 21篇 |
1981年 | 18篇 |
1980年 | 21篇 |
1979年 | 9篇 |
1978年 | 10篇 |
1977年 | 48篇 |
1976年 | 110篇 |
1974年 | 9篇 |
1973年 | 8篇 |
1971年 | 8篇 |
排序方式: 共有3218条查询结果,搜索用时 0 毫秒
1.
2.
M. J. O’Sullivan C. G. Walker M. L. O’Sullivan T. D. Thompson A. B. Philpott 《Telecommunication Systems》2006,33(4):353-376
The problem of designing fibre-optic networks for local-access telecommunications generates (at least) three non-trivial subproblems.
In the first of these subproblems one must determine how many fibre-optic cables (fibres) are required at either end of a
street. In the next subproblem a minimum-cost network must be designed to support the fibres. The network must also provide
distinct paths from either end of the street to the central exchange(s). Finally, the fibre-optic cables must be placed in
protective covers. These covers are available in a number of different sizes, allowing some flexibility when covering each
section of the network. In this paper we describe a dynamic programming (DP) formulation for finding a minimum-cost (protective)
covering for the network (the third of the subproblems). This problem is a generalised set covering problem with side constraints
and is further complicated by the introduction of fixed and variable welding costs. The DP formulation selects covers along
each arc (in the network), but cannot exactly model the fixed costs and so does not guarantee optimality. We also describe
an integer programming (IP) formulation for assessing the quality of the DP solutions. The cost of the networks constructed
by the IP model is less than those designed using the DP model, but the saving is not significant for the problems examined
(less than 0.1%). This indicates that the DP model will generally give very good solutions. Furthermore, as the problem dimensions
grow, DP gives significantly better solution times than IP. 相似文献
3.
4.
N Sobel V Prabhakaran JE Desmond GH Glover EV Sullivan JD Gabrieli 《Canadian Metallurgical Quarterly》1997,78(1-2):115-123
A method for generating olfactory stimuli for humans within a functional magnetic resonance imaging (fMRI) experimental design is described. The system incorporates a nasal-mask in which the change from odorant to no-odorant conditions occurs in less than 500 ms and is not accompanied by visual, auditory, tactile, or thermal cues. The mask provides an ordorant-free environment following prolonged ordorant presence. Specific imaging parameters that are conducive to the study of the human olfactory system are described. In a pilot study performed using these methods, the specific patterns of activation observed converged with published experimental and clinical findings. 相似文献
5.
6.
7.
A. J. Hugo D. M. Jakelski G. Stanitsas G. R. Sullivan R. R. Hudgins P. L. Silveston 《加拿大化工杂志》1986,64(2):349-351
In the approach to a cycle-invariant state in the forced feed concentration cycling of the CO oxidation over a NiO catalyst, a very long transient has been observed lasting 80 ks or more. This transient appears to be associated only with CO pretreatment of the catalyst and is not a general phenomenon. The slow convergence to the cycle-invariant state reported in certain modelling calculations in the literature appears to have a different cause. 相似文献
8.
Video Compression - From Concepts to the H.264/AVC Standard 总被引:10,自引:0,他引:10
Sullivan G.J. Wiegand T. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2005,93(1):18-31
Over the last one and a half decades, digital video compression technologies have become an integral part of the way we create, communicate, and consume visual information. In this paper, techniques for video compression are reviewed, starting from basic concepts. The rate-distortion performance of modern video compression schemes is the result of an interaction between motion representation techniques, intra-picture prediction techniques, waveform coding of differences, and waveform coding of various refreshed regions. The paper starts with an explanation of the basic concepts of video codec design and then explains how these various features have been integrated into international standards, up to and including the most recent such standard, known as H.264/AVC. 相似文献
9.
Comments on the article "A house divided? The psychology of red and blue America" by D. C. Seyle and M. L. Newman (see record 2006-11202-001). Seyle and Newman concluded that the red and blue metaphor is inaccurate and proposed a purple America strategy to better convey that the majority of people do not align themselves with political extremes. There is interdisciplinary agreement on this. Although not cited by Seyle and Newman, the findings by Professor Fiorina of Stanford University were reported by the APA Monitor on Psychology in its coverage of the 2005 APA State Leadership Conference (Murray Law, 2005). In contrast to their social psychological analysis, Seyle and Newman were incorrect in concluding that "[a]s psychologists, we are not in a position to change either the elements of the American political system that may spur this conflict or even the decisions made by pundits, politicians, and reporters about the terms they choose to use in political discussion" (p. 579). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
10.
Recently published studies indicate a potential clinical application of PET in head and neck tumors. In the preoperative staging phase, PET enables confirmation of regional lymph node extension and guides nodal neck dissection or systemic treatment. In this phase, a high negative predictive value, near 100%, could make it possible to avoid many negative neck dissections. This is a reliable technique for confirming or excluding the presence of recurrent/residual tumor and for obtaining an early evaluation of chemotherapeutic and radiotherapeutic response. PET imaging in many cases makes it possible to locate and guide histological study of tumors with an unknown primary. PET imaging for these indications is a perfect complementary method for clinical exploration and better than other imaging techniques. 相似文献