全文获取类型
收费全文 | 1739篇 |
免费 | 126篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 27篇 |
综合类 | 9篇 |
化学工业 | 574篇 |
金属工艺 | 27篇 |
机械仪表 | 24篇 |
建筑科学 | 133篇 |
矿业工程 | 24篇 |
能源动力 | 44篇 |
轻工业 | 156篇 |
水利工程 | 7篇 |
石油天然气 | 12篇 |
无线电 | 125篇 |
一般工业技术 | 351篇 |
冶金工业 | 90篇 |
原子能技术 | 7篇 |
自动化技术 | 268篇 |
出版年
2023年 | 14篇 |
2022年 | 19篇 |
2021年 | 49篇 |
2020年 | 44篇 |
2019年 | 44篇 |
2018年 | 32篇 |
2017年 | 37篇 |
2016年 | 74篇 |
2015年 | 73篇 |
2014年 | 98篇 |
2013年 | 104篇 |
2012年 | 87篇 |
2011年 | 101篇 |
2010年 | 65篇 |
2009年 | 95篇 |
2008年 | 74篇 |
2007年 | 74篇 |
2006年 | 65篇 |
2005年 | 70篇 |
2004年 | 49篇 |
2003年 | 50篇 |
2002年 | 39篇 |
2001年 | 23篇 |
2000年 | 23篇 |
1999年 | 28篇 |
1998年 | 31篇 |
1997年 | 24篇 |
1996年 | 24篇 |
1995年 | 23篇 |
1994年 | 26篇 |
1993年 | 27篇 |
1992年 | 23篇 |
1991年 | 23篇 |
1990年 | 19篇 |
1989年 | 18篇 |
1988年 | 11篇 |
1987年 | 9篇 |
1986年 | 18篇 |
1985年 | 13篇 |
1984年 | 10篇 |
1983年 | 19篇 |
1982年 | 7篇 |
1981年 | 14篇 |
1980年 | 16篇 |
1979年 | 11篇 |
1978年 | 15篇 |
1977年 | 8篇 |
1976年 | 9篇 |
1974年 | 7篇 |
1973年 | 6篇 |
排序方式: 共有1878条查询结果,搜索用时 15 毫秒
41.
From concepts to consistent object specifications: Translation of a domain-oriented feature framework into practice 下载免费PDF全文
HaraldE.Otto 《计算机科学技术学报》2001,16(3):0-0
A steady increase in consumer demands,and severe constraints from both a somewhat damaged environment and newly installed government policies,require today‘s product design and development to be faster and more efficient than ever before,yet utilizing even fewer resources.New holistic approaches,such at total product life cycle modeling which embraces all aspercts of a product‘s life cycle,are current attempts to solve these problems,Within the field of product design and modeling,feature technology has proved to be one very promising solution component.Owing to the tremendous increase in information technology,to transfer from low level data processing towards knowledge modeling and information processing is about to bring a change in almost every computerized application.From this viewpoint,current problems of both feature frameworks and feature systems are analyzed in respect to static and dynamic consistency breakdowns.The analysis ranges from early stager of designing(feature)concepts to final system implementation and application.For the first tie,an integrated view is given on approaches,solutions and practical experience,with feature concepts and structures,providing both a feature framework and its implementation with sufficient system architecture and computational power to master a fair number of known consistency breakdowns,while providing for robust contexts for feature semantics and integrated models.Within today;s heavy use of information technology these are pre-requisites if the full potential of feature technology is to be successfully translated into practice. 相似文献
42.
Rudolf Treleano Hans-Dieter Belitz Harald Jugel und Herbert Wieser 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1978,167(5):320-323
Zusammenfassung 1-Aminocycloalkan-l-carbonsäuren mit Ringgrößen von 4–11 (ohne 10) wurden synthetisiert und auf ihre Geschmackseigenschaften untersucht. Süßer Geschmack tritt vom 4-Ring bis zum 8-Ring auf, beim 6-Ring ist der Schwellenwert minimal (c
Ssü=1–3 mmol/l). Bitter sind die Verbindungen vom 5-Ring bis zum 9-Ring, das Minimum des Schwellenwertes liegt beim 8-Ring (c
sbi=2–5 mmol/l). Die größeren Ringe sind bis zu Konzentrationen von 20 mmol/l ohne Geschmack. Beim 6-Ring löscht eine 2-Methylgruppe jeden Geschmackseindruck, während die 3- und 4-Methylverbindungen süß und bitter sind. Die 4-Äthylverbindung ist bitter aber nicht süß, die 4-tert.-Butylverbindung ist ohne Geschmack. 1-Aminonorbornan-1-carbonsäure ist süß (c
Ssü 50 mmol/l) und bitter (c
sbi=5–7mmo1/1), wobei der Schwellenwert für bitter fast eine Zehnerpotenz kleiner ist. tert.-Leucin ist ohne Geschmack. Die Ergebnisse werden im Zusammenhang mit früheren Untersuchungen an offenkettigen Aminosäuren diskutiert und in Modelle über sterische Voraussetzungen für Geschmack eingeordnet.
Relationsships between structure and taste in amino acids with cyclic side chains
Summary 1-Aminocycloalkane-1-carboxylic acids with ring sizes of 4–11 (excluding 10) were synthesized and tested for their taste properties. The compounds with 4- to 8-membered rings are sweet, with threshold values going through a minimum for the 6-membered ring (c tsw = l-3 mM/l). The compounds with 5- to 9-membered rings are bitter. Here the threshold value reaches a minimum for the 8-membered ring (c tbi=2–5 mM/l). The larger rings are without taste up to concentrations of 20 mmol/l. With the 6-membered ring a 2-methyl group abolishes any taste impression, whereas the 3- and 4-methyl compounds are sweet and bitter. The 4-ethyl compound is bitter but not sweet, the 4-tert.-butyl compound has no taste. 1-Aminonorbornane-l-carboxylic acid is sweet (c tsw 50mM/l) and bitter (c tbi= 5–7 mM/l), withc tbi being significantly smaller thanc tsw. tert-Leucine is without taste. The results are discussed in relation to previous investigations into steric prerequisites for taste in the amino acid series.相似文献
43.
Michael Würsch Giacomo Ghezzi Matthias Hert Gerald Reif Harald C. Gall 《Computing》2012,94(11):857-885
The Semantic Web provides a standardized, well-established framework to define and work with ontologies. It is especially apt for machine processing. However, researchers in the field of software evolution have not really taken advantage of that so far. In this paper, we address the potential of representing software evolution knowledge with ontologies and Semantic Web technology, such as Linked Data and automated reasoning. We present Seon, a pyramid of ontologies for software evolution, which describes stakeholders, their activities, artifacts they create, and the relations among all of them. We show the use of evolution-specific ontologies for establishing a shared taxonomy of software analysis services, for defining extensible meta-models, for explicitly describing relationships among artifacts, and for linking data such as code structures, issues (change requests), bugs, and basically any changes made to a system over time. For validation, we discuss three different approaches, which are backed by Seon and enable semantically enriched software evolution analysis. These techniques have been fully implemented as tools and cover software analysis with web services, a natural language query interface for developers, and large-scale software visualization. 相似文献
44.
45.
Minna Karstunen Harald Krenn Simon J. Wheeler Mirva Koskinen Rachid Zentar 《Canadian Metallurgical Quarterly》2005,5(2):87-97
This paper investigates the influence of anisotropy and destructuration on the behavior of a test embankment on soft clay. The test embankment at Murro, Finland, was commissioned in 1993 by the Finnish Road Administration and has been monitored for over 10?years. The construction and consolidation of Murro test embankment is analyzed with finite element method using three different constitutive models to represent the soft soil. The results are compared with field observations. The constitutive models used include two recently proposed constitutive models, namely S-CLAY1 that accounts for initial and plastic strain induced anisotropy and its extension, called S-CLAY1S. The S-CLAY1S model accounts, additionally, for interparticle bonding and degradation of bonds. For comparison, the test embankment is also analyzed using the isotropic Modified Cam Clay model. The simulations demonstrate that for this type of problem, it is important to account for the anisotropy, whereas destructuration appears to have less influence on predicted deformations. However, only a model incorporating destructuration can explain the decrease in undrained shear strength during consolidation that was measured in field. 相似文献
46.
We present a new solver for coupled nonlinear elliptic partial differential equations (PDEs). The solver is based on pseudo-spectral collocation with domain decomposition and can handle one- to three-dimensional problems. It has three distinct features. First, the combined problem of solving the PDE, satisfying the boundary conditions, and matching between different subdomains is cast into one set of equations readily accessible to standard linear and nonlinear solvers. Second, touching as well as overlapping subdomains are supported; both rectangular blocks with Chebyshev basis functions as well as spherical shells with an expansion in spherical harmonics are implemented. Third, the code is very flexible: The domain decomposition as well as the distribution of collocation points in each domain can be chosen at run time, and the solver is easily adaptable to new PDEs. The code has been used to solve the equations of the initial value problem of general relativity and should be useful in many other problems. We compare the new method to finite difference codes and find it superior in both runtime and accuracy, at least for the smooth problems considered here. 相似文献
47.
Jií Bittner Michael Wimmer Harald Piringer Werner Purgathofer 《Computer Graphics Forum》2004,23(3):615-624
48.
A method for solvent screening and searching for additives in the field of physical absorption processes is presented. A model based on the concept of virtual components and on the concept of a simplified abstract flow sheet is created. An estimation procedure for thermodynamically consistent property sets for the virtual component is developed. The model is implemented into MATLAB®. Its application is demonstrated in two studies including a study for a solvent additive. Potential candidates can be characterized and ranges for properties of the solvent or additive are found by means of the model. Conclusions obtained from the model support the screening process by a reduction of the number of further investigated components. 相似文献
49.
50.
Harald Mischak 《Proteomics. Clinical applications》2012,6(9-10):437-442
Clinical proteomics is defined as application of proteome analysis aiming at improving the current clinical situation. As such, the success of clinical proteomics should be assessed based on the clinical impact following implementation of the findings. While we have experienced significant technological advancements in mass spectrometry in the last years, based on the above measure, this has not at all resulted in similar advancements in clinical proteomics. Although a large number of proteomic biomarkers have been described, most of them were not subsequently validated, and certainly have had no impact in clinical decision making as yet. Under the current conditions, it appears likely that the situation will not change significantly: we will be flooded by reports on biomarkers, but not see any implementation. In this article, some key issues in proteomic biomarker research are pinpointed, based on the experience with CE‐MS, likely also holding true for biomarkers resulting from other analysis domains. 相似文献