全文获取类型
收费全文 | 5537篇 |
免费 | 418篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 66篇 |
综合类 | 7篇 |
化学工业 | 1598篇 |
金属工艺 | 65篇 |
机械仪表 | 111篇 |
建筑科学 | 217篇 |
矿业工程 | 10篇 |
能源动力 | 219篇 |
轻工业 | 716篇 |
水利工程 | 45篇 |
石油天然气 | 7篇 |
无线电 | 390篇 |
一般工业技术 | 1050篇 |
冶金工业 | 462篇 |
原子能技术 | 31篇 |
自动化技术 | 966篇 |
出版年
2024年 | 12篇 |
2023年 | 81篇 |
2022年 | 241篇 |
2021年 | 408篇 |
2020年 | 188篇 |
2019年 | 190篇 |
2018年 | 222篇 |
2017年 | 196篇 |
2016年 | 269篇 |
2015年 | 198篇 |
2014年 | 294篇 |
2013年 | 370篇 |
2012年 | 363篇 |
2011年 | 471篇 |
2010年 | 308篇 |
2009年 | 261篇 |
2008年 | 312篇 |
2007年 | 246篇 |
2006年 | 171篇 |
2005年 | 155篇 |
2004年 | 138篇 |
2003年 | 127篇 |
2002年 | 90篇 |
2001年 | 64篇 |
2000年 | 54篇 |
1999年 | 55篇 |
1998年 | 65篇 |
1997年 | 50篇 |
1996年 | 50篇 |
1995年 | 31篇 |
1994年 | 35篇 |
1993年 | 35篇 |
1992年 | 28篇 |
1991年 | 22篇 |
1990年 | 16篇 |
1989年 | 16篇 |
1988年 | 13篇 |
1987年 | 18篇 |
1986年 | 10篇 |
1985年 | 13篇 |
1984年 | 15篇 |
1983年 | 13篇 |
1982年 | 14篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 10篇 |
1977年 | 2篇 |
1967年 | 2篇 |
1954年 | 1篇 |
1948年 | 1篇 |
排序方式: 共有5960条查询结果,搜索用时 265 毫秒
101.
Background
Engineers are often expected to span organizational, cultural, stakeholder, geographic, temporal, and other boundaries. Yet, few studies on boundary spanning have appeared in the engineering education literature, suggesting the need for improved theoretical and conceptual foundations to guide empirical studies of boundary spanning in engineering.Purpose
To develop a more comprehensive understanding of boundary spanning, this study addresses five research questions: (a) What types of boundaries have been identified as topics of interest? (b) How are boundary spanners and boundary spanning defined? (c) What types of activities and behaviors comprise or have been linked to boundary spanning? (d) What individual competencies and characteristics have been proposed or studied as important for boundary spanning? and (e) What boundary spanning themes are most prominent in studies of engineers and other technical professionals?Scope/Method
Using a qualitative systematic review process, we identified and analyzed 72 scholarly papers from multiple disciplines. Multiple reviewers coded each paper using a hybrid deductive‐inductive content analysis process to identify key themes related to boundary spanning.Conclusions
The analysis resulted in a framework consisting of six boundary types, three types of roles and definitions, and five types of activities. Discussion of boundary spanning competencies was limited in the collected works, and only seven papers exclusively focused on engineers. We conclude by proposing boundary spanning as an important meta‐attribute for engineers and a promising lens for investigating engineering practice. We also relate our findings to the engineering education literature and suggest directions for future research. 相似文献102.
Giordano Maria C. Longhi Stefano Barelli Matteo Mazzanti Andrea Buatier de Mongeot Francesco Della Valle Giuseppe 《Nano Research》2018,11(7):3943-3956
Nano Research - The engineering of self-organized plasmonic metasurfaces is demonstrated using a maskless technique with defocused ion-beam sputtering and kinetically controlled deposition. The... 相似文献
103.
104.
We first show that ground term-rewriting systems can be completed in a polynomial number of rewriting steps, if the appropriate data structure for terms is used. We then apply this result to study the lengths of critical pair proofs in non-ground systems, and obtain bounds on the lengths of critical pair proofs in the non-ground case. We show how these bounds depend on the types of inference steps that are allowed in the proofs. 相似文献
105.
Murtas C Bruschi M Carnevali ML Petretto A Corradini E Prunotto M Candiano G degl'Innocenti ML Ghiggeri GM Allegri L 《Proteomics. Clinical applications》2011,5(1-2):90-97
Renal auto-immune diseases represent a major source of morbidity in humans. For many years the knowledge on mechanisms of auto-immunity involving the kidney has been uniquely based on animal models. However, these findings often could not be readily translated to humans owing to notably difference in antigen expression by human podocytes. One example is Heymann nephritis (HN), the experimental model of human membranous glomerulonephritis (MGN), which is obtained in rats by injecting antibodies against megalin, a protein that is not present in human glomeruli. Human studies could not be done in the past since sequencing required too much material exceeding what obtainable from tissue biopsies in vivo. Research is now on the way to identify auto-antigens and isolate specific auto-antibodies in humans. New technology developments based on tissue microdissection and proteomical analysis have facilitated the recent discoveries, allowing direct analysis of human tissue in vivo. Major advances on the pathogenesis of MGN, the prototype for the formation and glomerular deposition of auto-antibodies, are now in progress. Two independent groups have, in fact, demonstrated the existence of specific IgG(4) against phospholipase A2 receptor, aldose reductase and Mn-superoxide dismutase in glomerular eluates and in plasma of a prominent part of patients with MGN, suggesting a major role of these proteins as auto-antigens in human MGN. This review will focalize these aspects outlining the contribution of proteomics in most recent developments. 相似文献
106.
Philip E. Dennison Andrea R. Brunelle Vachel A. Carter 《Remote sensing of environment》2010,114(11):2431-2435
Continuing, severe outbreaks of mountain pine beetle (Dendroctonus ponderosae) across western North America have resulted in widespread mortality of lodgepole pine (Pinus contorta). Multiple studies have used high spatial resolution satellite data to map areas of beetle kill; these studies have largely focused on mapping red canopy cover associated with recent tree mortality and have not examined mapping gray canopy cover that occurs after red needles have dropped. The work presented here examines the use of newly available GeoEye-1 data for mapping both red and gray canopy area in southeastern Wyoming lodgepole pine forest. A 0.5 m spatial resolution, pan-sharpened GeoEye-1 image was used to classify areas of green, red, and gray canopy cover. Reference data were collected at twelve 500 m2 field plots. Shadow-normalized green, red, and gray canopy area from classified GeoEye-1 data closely agreed with field-estimated green, red, and gray canopy area. Mean absolute error in canopy cover for the twelve sample plots was 8.3% for the green class, 5.4% for the red class, and 7.2% for the gray class. When all twelve plots were aggregated, remotely sensed estimates of green, red, and gray cover were within 1.7% of the field-estimated cover. Our results demonstrate that high spatial resolution spaceborne multispectral data are a promising tool for mapping canopy mortality caused by mountain pine beetle outbreaks. 相似文献
107.
108.
The introduction of Internet and Information and communication Technologies (ICT) in offices is a global phenomenon that transformed
white-collar worker job demands. Although there are several studies of e-skills and mental workload for central countries,
there is a lack of similar studies for the Latin American context. An online snowball sampled (n = 352) survey was developed and validated by the authors (internal consistency = 0.7). We characterized ICT worker profiles
from e-skills and these dimensions: attitudes toward, resources usage and technology dependency. Mental Strain was assessed with raw task load index (RTLX) and correlated with the proposed profiles by means of paired
T-tests and Mann–Whitney Tests. The sample was characterized by 7.2% of non visual display terminal users and 92.8% of visual
display terminal, ICT skilled users. Of the latter, 30.7% were ICT practitioners, 30.4% were ICT Users and 27.2% were E-Business
Users. Non VDT users’ mental strain was statistically meaningful smaller than VDT–ICT skilled users’ mental workload. No statistical
differences were found in RTLX results when comparing ICT skilled user profiles. Non VDT users can be identified from ICT
skilled Users by their lower ITC Dependency and minor use of ICT resources. There were no differences in those dimensions
among ICT skilled Profiles. Attitude toward these technologies was a distinct factor for ICT Users in relation to ICT Practitioners
and ITC Business Users. The application of this tool in peripheral and central countries would allow a complete ergonomical
characterization of white-collar workers within the Information Society. 相似文献
109.
Franco Cicirelli Angelo Furfaro Andrea Giordano Libero Nigro 《Simulation Modelling Practice and Theory》2011,19(1):283-300
RePast is a popular agent toolkit with proven capabilities to fulfil the modelling challenges of large multi-agent systems (MASs). The toolkit, though, is normally used on a standalone workstation and therefore its practical use can be constrained (in space and time) by the limited available computing resources. This paper proposes an original approach – HLA_ACTOR_REPAST – aimed to distributing RePast models for high-performance simulation of complex scalable models. Novel in HLA_ACTOR_REPAST is an exploitation of a lean actor infrastructure implemented in Java. Actors bring to RePast agents such features as migration, location-transparent naming, efficient communications, and a control-centric framework. Actors can be orchestrated by an in-the-large custom control structure which is in charge of ensuring the necessary message causality constraints. Distribution and time management concerns depend on the IEEE standard HLA middleware. The paper first discusses details of the software engineering process underlying the development of HLA_ACTOR_REPAST. The mapping techniques, assisted by Java text annotations and aspect-oriented programming, try to minimize “code intrusions” in the original model and favour model transparency. The paper then furnishes some experimental data which witness the good performance results achieved by applying HLA_ACTOR_REPAST to a distributed version of a classic MAS benchmark model. 相似文献
110.
Combinatorial testing is as an effective testing technique to reveal failures in a given system, based on input combinations
coverage and combinatorial optimization. Combinatorial testing of strength
t (t ≥ 2) requires that each t-wise tuple of values of the different system input parameters is covered by at least one test case. Combinatorial test suite generation
algorithms aim at producing a test suite covering all the required tuples in a small (possibly minimal) number of test cases,
in order to reduce the cost of testing. The most used combinatorial technique is the pairwise testing (t = 2) which requires coverage of all pairs of input values. Constrained combinatorial testing takes also into account constraints
over the system parameters, for instance forbidden tuples of inputs, modeling invalid or not realizable input values combinations. In this paper a new approach to combinatorial
testing, tightly integrated with formal logic, is presented. In this approach, test predicates are used to formalize combinatorial
testing as a logical problem, and an external formal logic tool is applied to solve it. Constraints over the input domain
are expressed as logical predicates too, and effectively handled by the same tool. Moreover, inclusion or exclusion of select
tuples is supported, allowing the user to customize the test suite layout. The proposed approach is supported by a prototype
tool implementation and results of experimental assessment are also presented. 相似文献