全文获取类型
收费全文 | 1910篇 |
免费 | 94篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 24篇 |
综合类 | 2篇 |
化学工业 | 463篇 |
金属工艺 | 53篇 |
机械仪表 | 37篇 |
建筑科学 | 55篇 |
矿业工程 | 9篇 |
能源动力 | 59篇 |
轻工业 | 167篇 |
水利工程 | 10篇 |
石油天然气 | 2篇 |
无线电 | 138篇 |
一般工业技术 | 354篇 |
冶金工业 | 291篇 |
原子能技术 | 17篇 |
自动化技术 | 326篇 |
出版年
2023年 | 13篇 |
2022年 | 13篇 |
2021年 | 33篇 |
2020年 | 28篇 |
2019年 | 43篇 |
2018年 | 61篇 |
2017年 | 61篇 |
2016年 | 64篇 |
2015年 | 57篇 |
2014年 | 72篇 |
2013年 | 126篇 |
2012年 | 102篇 |
2011年 | 143篇 |
2010年 | 101篇 |
2009年 | 111篇 |
2008年 | 108篇 |
2007年 | 82篇 |
2006年 | 55篇 |
2005年 | 69篇 |
2004年 | 42篇 |
2003年 | 50篇 |
2002年 | 41篇 |
2001年 | 23篇 |
2000年 | 31篇 |
1999年 | 23篇 |
1998年 | 62篇 |
1997年 | 45篇 |
1996年 | 60篇 |
1995年 | 18篇 |
1994年 | 27篇 |
1993年 | 32篇 |
1992年 | 14篇 |
1991年 | 9篇 |
1990年 | 10篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 13篇 |
1986年 | 10篇 |
1985年 | 8篇 |
1984年 | 11篇 |
1983年 | 5篇 |
1982年 | 20篇 |
1981年 | 9篇 |
1979年 | 10篇 |
1978年 | 4篇 |
1977年 | 16篇 |
1976年 | 25篇 |
1975年 | 6篇 |
1974年 | 5篇 |
1973年 | 8篇 |
排序方式: 共有2007条查询结果,搜索用时 922 毫秒
61.
This paper provides a bridge between the classical tiling theory and the complex-neighborhood self-assembling situations that exist in practice.The neighborhood of a position in the plane is the set of coordinates which are considered adjacent to it. This includes classical neighborhoods of size four, as well as arbitrarily complex neighborhoods. A generalized tile system consists of a set of tiles, a neighborhood, and a relation which dictates which are the “admissible” neighboring tiles of a given tile. Thus, in correctly formed assemblies, tiles are assigned positions of the plane in accordance with this relation.We prove that any validly tiled path defined in a given but arbitrary neighborhood (a zipper) can be simulated by a simple “ribbon” of microtiles. A ribbon is a special kind of polyomino, consisting of a non-self-crossing sequence of tiles on the plane, in which successive tiles stick along their adjacent edge.Finally, we extend this construction to the case of traditional tilings, proving that we can simulate arbitrary-neighborhood tilings by simple-neighborhood tilings, while preserving some of their essential properties. 相似文献
62.
Wilfried M. Post Mirjam A. A. Huis in ’t Veld Sylvia A. A. van den Boogaard 《Personal and Ubiquitous Computing》2008,12(3):223-235
Many attempts are underway for developing meeting support tools, but less attention is paid to the evaluation of meetingware.
This article describes the development and testing of an instrument for evaluating meeting tools. First, we specified the
object of evaluation—meetings—by means of a set of input, process, and outcome factors. Then, we designed the process of evaluation,
consisting of, first, the generation of meeting behavior in the form of a controlled series of meetings within the context
of a project and, second, the measurement of the identified meeting factors. To measure these factors, a rating scale, questionnaires,
and information flow analysis were used. Next, the instrument was tested, and the factors for successful meetings were determined
in 13 projects in which four participants had to meet four times. The evaluation instrument proved to be a reliable and useful
aid for the development and improvement of meeting tools. 相似文献
63.
T.?LimEmail author J.?M.?Ritchie R.?G.?Dewar J.?R.?Corney P.?Wilkinson M.?Calis M.?Desmulliez J.-J.?Fang 《Virtual Reality》2007,11(4):241-252
Current computer-aided assembly systems provide engineers with a variety of spatial snapping and alignment techniques for
interactively defining the positions and attachments of components. With the advent of haptics and its integration into virtual
assembly systems, users now have the potential advantage of tactile information. This paper reports research that aims to
quantify how the provision of haptic feedback in an assembly system can affect user performance. To investigate human–computer
interaction processes in assembly modeling, performance of a peg-in-hole manipulation was studied to determine the extent to which haptics and stereovision may impact on task completion time. The
results support two important conclusions: first, it is apparent that small (i.e. visually insignificant) assembly features
(e.g. chamfers) affect the overall task completion at times only when haptic feedback is provided; and second, that the difference
is approximately similar to the values reported for equivalent real world peg-in-hole assembly tasks. 相似文献
64.
Mechanical damping (tan ) and stress relaxation on pine veneer samples under stepwise humidity changes were investigated. The loss factor shows a transient peak every time the relative humidity (RH) of the surrounding atmosphere is changed. The effect appears to be associated with the diffusion of water molecules into or out of the material, the peaks being observed both when the sample is humidified (5%–85% RH) or subjected to drying. The results are supplemented by stress relaxation data obtained on similar specimens. Also in this case a higher relaxation rate is observed when the RH level around the sample is changed, the total stress decrease after several cycles being significantly larger than the corresponding value observed after the same period at the higher RH level. 相似文献
65.
66.
In this study an agricultural residue, sesame stalk, was evaluated for the removal of Ni(II) and Zn(II) metal ions from aqueous solutions. Biosorption studies were carried out at different pH, biosorbent dosage, initial metal ion concentrations, contact time, and solution temperature to determine the optimum conditions. The experimental data were modeled by Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Temkin isotherm models. Langmuir model resulted in the best fit of the biosorption data. The pseudo-first-order and pseudo-second-order kinetic models were used to describe the kinetic data and to evaluate rate constants. The best correlation was provided by the second-order kinetic model. The thermodynamic parameters such as ΔG°, ΔH° and ΔS° were calculated for predicting the nature of adsorption. The experimental results showed that sesame stalk can be used as an effective and low-cost biosorbent precursor for the removal of heavy metal ions from aqueous solutions. 相似文献
67.
The Parity Path problem is to decide if a given graph contains both an induced path of odd length and an induced path of even length between two specified vertices. In the related problems Odd Induced Path and Even Induced Path, the goal is to determine whether an induced path of odd, respectively even, length between two specified vertices exists. Although all three problems are NP-complete in general, we show that they can be solved in $\mathcal{O}(n^{5})$ time for the class of claw-free graphs. Two vertices s and t form an even pair in G if every induced path from s to t in G has even length. Our results imply that the problem of deciding if two specified vertices of a claw-free graph form an even pair, as well as the problem of deciding if a given claw-free graph has an even pair, can be solved in $\mathcal{O}(n^{5})$ time and $\mathcal{O}(n^{7})$ time, respectively. We also show that we can decide in $\mathcal{O}(n^{7})$ time whether a claw-free graph has an induced cycle of given parity through a specified vertex. Finally, we show that a shortest induced path of given parity between two specified vertices of a claw-free perfect graph can be found in $\mathcal {O}(n^{7})$ time. 相似文献
68.
Côté JN 《Ergonomics》2012,55(2):173-182
The objective of this paper is to critically review recent literature on physical and functional sex/gender (s/g) differences, with focus on physical determinants associated with neck/shoulder musculoskeletal injuries. It is well known that there are s/g differences in anthropometrical and functional body characteristics (e.g. size and strength). However, s/g differences may be wrongly attributed if data analysis does not include appropriate corrections (e.g. by strength for endurance). Recent literature on motor control shows that there may indeed be s/g differences in muscle coordination and movement strategies during upper limb tasks that are not currently explained by methodological inadequacies. Moreover, recent studies have shown differences between men and women in sensory hypersensitivity characteristics associated with neck/shoulder injuries. Taken together, the literature points to the importance of accounting for possible s/g differences at all levels of the biopsychosocial system in order to better understand sex- and gender-specific issues relevant to workplace health. PRACTITIONER SUMMARY: This article critically reviews recent literature and a conceptual model highlighting s/g differences in physical and functional characteristics related to neck/shoulder musculoskeletal disorders (NSMSD). Findings have implications on understanding how personal factors may affect NSMSD risk. With better understanding, practitioners can make more appropriate decisions to prevent work-related NSMSD. 相似文献
69.
Stern Emily R.; Horvitz Jon C.; C?té Lucien J.; Mangels Jennifer A. 《Canadian Metallurgical Quarterly》2005,19(1):54
The authors explored the effect of Parkinson's disease (PD) on the generation and maintenance of response readiness in a simple reaction time task. They compared performance of idiopathic PD patients without dementia, age-matched controls, and younger controls over short (1-, 3-, and 6-s) and long (12- and 18-s) foreperiod intervals. After each trial, the authors probed memory for visual information that also had to be maintained during the trial interval. Patients and controls did not differ overall in their ability to maintain readiness over long delays. However, within the PD group only, errors in maintaining visual information were correlated with difficulty in maintaining readiness, suggesting that systems impaired in PD may facilitate the maintenance of processing in both motor and cognitive domains. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
70.
Harri Tuomisto Petra Lundstrm Ritva Korhonen Jzsef Elter Milan Hladký Jozef Tomek Ludovít Fagula 《Nuclear Engineering and Design》2003,221(1-3):181
There are twelve operating VVER-440/213 reactors in the Czech Republic, Hungary and Slovakia. The plant owners have carried out extensive safety enhancement programmes, which have included measures to improve prevention, mitigation and control of design basis accidents. Recently, there have been a number of projects to study the Severe Accident Management aspects of these plants. The plant owners have also initiated Plant Life Management programmes. The objective of the VERSAFE Concerted Action is to create a network of the VVER-440/213 plant owners and operators, which aims at definition of the further research needs of severe accidents and plant ageing from the utilities’ viewpoint. The starting point is to formulate a general approach to severe accident management and plant life management and then proceed to define the needs for the additional information expected from the safety research. The role of national research institutes and organisations of the partner countries is of crucial importance in performing such research and, thus, creating and maintaining the expertise on the national level. The successful completion of the project will assist in establishing well-defined research projects that are oriented to the needs of the end-users and provide information that can be used to facilitate and support the negotiations of the EU applicant countries operating VVER-440 reactors. 相似文献