全文获取类型
收费全文 | 5847篇 |
免费 | 398篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 94篇 |
综合类 | 2篇 |
化学工业 | 1436篇 |
金属工艺 | 106篇 |
机械仪表 | 132篇 |
建筑科学 | 141篇 |
矿业工程 | 7篇 |
能源动力 | 253篇 |
轻工业 | 824篇 |
水利工程 | 43篇 |
石油天然气 | 21篇 |
无线电 | 488篇 |
一般工业技术 | 955篇 |
冶金工业 | 514篇 |
原子能技术 | 36篇 |
自动化技术 | 1204篇 |
出版年
2024年 | 10篇 |
2023年 | 77篇 |
2022年 | 194篇 |
2021年 | 228篇 |
2020年 | 166篇 |
2019年 | 172篇 |
2018年 | 204篇 |
2017年 | 200篇 |
2016年 | 238篇 |
2015年 | 164篇 |
2014年 | 258篇 |
2013年 | 406篇 |
2012年 | 344篇 |
2011年 | 435篇 |
2010年 | 303篇 |
2009年 | 295篇 |
2008年 | 282篇 |
2007年 | 259篇 |
2006年 | 199篇 |
2005年 | 187篇 |
2004年 | 139篇 |
2003年 | 129篇 |
2002年 | 128篇 |
2001年 | 83篇 |
2000年 | 87篇 |
1999年 | 82篇 |
1998年 | 194篇 |
1997年 | 133篇 |
1996年 | 102篇 |
1995年 | 65篇 |
1994年 | 47篇 |
1993年 | 54篇 |
1992年 | 34篇 |
1991年 | 39篇 |
1990年 | 25篇 |
1989年 | 23篇 |
1988年 | 25篇 |
1987年 | 14篇 |
1986年 | 22篇 |
1985年 | 20篇 |
1984年 | 26篇 |
1983年 | 27篇 |
1982年 | 21篇 |
1981年 | 12篇 |
1980年 | 14篇 |
1979年 | 13篇 |
1977年 | 11篇 |
1976年 | 21篇 |
1975年 | 10篇 |
1973年 | 11篇 |
排序方式: 共有6256条查询结果,搜索用时 15 毫秒
11.
This paper looks at the concepts of entities, identities, identifiers and credentials, their definitions, and how they combine
to authenticate an identity to an account, or function, within a service. Credentials can be divided into several different
types on the basis of their use, origin and characteristics. In particular, types such as composite, dynamic and derived credentials
will be considered, and their applicability within an identity management system. Each credential must be managed through
its entire life cycle from initial registration, general use and suspension, to deletion. The notion of public (i.e. freely
distributable) and private (i.e. known only to you) aspects of a credential is explored. The bindings, by trusted third parties,
of identifiers and public credentials into permits and instruments of proof is explained along with the convenience, but greater
exposure, of local information. Several scenarios are analysed in terms of how different types of credentials are employed
during the authentication process. 相似文献
12.
O Bernard B Chachuat A Hélias B Le Dantec B Sialve J-P Steyer L Lardon P Neveu S Lambert J Gallop M Dixon P Ratini A Quintabà S Frattesi J M Lema E Roca G Ruiz J Rodriguez A Franco P Vanrolleghem U Zaher D J W De Pauw K De Neve K Lievens D Dochaine O Schoefs H Fibrianto R Farina V Alcaraz Gonzalez V Gonzalez Alvarez P Lemaire J A Martinez F Esandi O Duclaud J F Lavigne 《Water science and technology》2005,52(1-2):457-464
The TELEMAC project brings new methodologies from the Information and Science Technologies field to the world of water treatment. TELEMAC offers an advanced remote management system which adapts to most of the anaerobic wastewater treatment plants that do not benefit from a local expert in wastewater treatment. The TELEMAC system takes advantage of new sensors to better monitor the process dynamics and to run automatic controllers that stabilise the treatment plant, meet the depollution requirements and provide a biogas quality suitable for cogeneration. If the automatic system detects a failure which cannot be solved automatically or locally by a technician, then an expert from the TELEMAC Control Centre is contacted via the internet and manages the problem. 相似文献
13.
Penedo Frank J.; Dahn Jason R.; Gonzalez Jeffrey S.; Molton Ivan; Carver Charles S.; Antoni Michael H.; Roos Bernard A.; Schneiderman Neil 《Canadian Metallurgical Quarterly》2003,22(2):220
This study evaluated relations among optimism, perceived stress management skills (PSMS), and positive mood in 46 men who had surgical treatment for localized prostate cancer. The authors found that optimism, PSMS, and positive mood scores were positively correlated. Positive mood was unrelated to demographic and disease-related control variables. In a hierarchical regression model controlling for PSMS, the relationship between optimism and positive mood became nonsignificant, whereas PSMS remained a correlate of positive mood. Results suggest that the relationship between optimism and positive mood may be mediated by belief in being able to use stress management techniques effectively. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
14.
Maria Chiara Dalconi Giuseppe Cruciani Alberto Alberti Paolo Ciambelli 《Catalysis Today》2005,110(3-4):345-350
High-silica zeolites exchanged with transition metal ions (TMIs) are the subject of great interest for their unusual catalytic activity and selectivity. Structural information like coordination and accessibility of TMIs in zeolites are important factors for understanding their catalytic activity. Siting of TMIs in zeolites is typically obtained by spectroscopic (EXAFS, EPR, UV–vis and IR) and computational methods, as in the case of Co-ferrierite. However, some controversy exists in the literature concerning the model for incorporation of bare Co ions in ferrierite. We show here that the results of our synchrotron X-ray powder diffraction studies on Co- and Ni-exchanged ferrierite (Si/Al = 8.5) are in a good agreement with the model of Co siting based on an indirect spectroscopic approach and help to validate this model. By direct structural evidences, a possible explanation for the larger catalytic activity of Co sites in the main channels of ferrierite can be inferred. A combination of data from in situ XRD continuous monitoring of the Co ion migration during calcination and crystal-chemical considerations allows to device a strategy for the design of optimised co-cations containing Co-ferrierite catalysts. 相似文献
15.
Miguel Palomino Narciso Martí-Oliet Alberto Verdejo 《Electronic Notes in Theoretical Computer Science》2005,124(1):3
This paper is an introduction to rule-based programming in Maude. We illustrate in particular the use of operator attributes to structure the state of a system, and the difference between equations and rules. We use well-known mathematical games and puzzles for our examples illustrating the expressive power of Maude. 相似文献
16.
Determination of peroxide value by conventional difference and difference-derivative spectrophotometry 总被引:1,自引:0,他引:1
Alberto Lezerovich 《Journal of the American Oil Chemists' Society》1985,62(10):1495-1500
The spectrophotometric behavior of the system iodide-iodine-iodate-oxygen was studied, and a simple iodometric method to determine
peroxide value by conventional, difference or difference-derivative spectrophotometry was developed. The procedures are carried
out inside standard photometric cells containing iodide solution to which the sample is added. Absorbance or its first derivative
with respect to wavelength is measured to determine iodine concentration by means of calibration curves. No special care to
avoid iodide oxidation by atmospheric oxygen is necessary.
The method is applicable even to lipids that give emulsions with water, such as phosphatides, and precise results are obtained
even at low peroxide values.
The use of a digital spectrophotometer with data processing and programming facilities allowed development of an interactive
program for automatic operation, which is outlined. 相似文献
17.
18.
Gonzalez A. Valero-Garcia M. Diaz de Cerio L. 《Parallel and Distributed Systems, IEEE Transactions on》1995,6(8):803-814
Many parallel algorithms use hypercubes as the communication topology among their processes. When such algorithms are executed on hypercube multicomputers the communication cost is kept minimum since processes can be allocated to processors in such a way that only communication between neighbor processors is required. However, the scalability of hypercube multicomputers is constrained by the fact that the interconnection cost-per-node increases with the total number of nodes. From scalability point of view, meshes and toruses are more interesting classes of interconnection topologies. This paper focuses on the execution of algorithms with hypercube communication topology on multicomputers with mesh or torus interconnection topologies. The proposed approach is based on looking at different embeddings of hypercube graphs onto mesh or torus graphs. The paper concentrates on toruses since an already known embedding, which is called standard embedding, is optimal for meshes. In this paper, an embedding of hypercubes onto toruses of any given dimension is proposed. This novel embedding is called xor embedding. The paper presents a set of performance figures for both the standard and the xor embeddings and shows that the latter outperforms the former for any torus. In addition, it is proven that for a one-dimensional torus (a ring) the xor embedding is optimal in the sense that it minimizes the execution time of a class of parallel algorithms with hypercube topology. This class of algorithms is frequently found in real applications, such as FFT and some class of sorting algorithms 相似文献
19.
Hydrocarbon exploration risk evaluation through uncertainty and sensitivity analyses techniques 总被引:1,自引:0,他引:1
Paolo Ruffo Livia Bazzana Alberto Consonni Anna Corradi Andrea Saltelli Stefano Tarantola 《Reliability Engineering & System Safety》2006,91(10-11):1155-1162
The evaluation of the exploration risk in the oil industry is a fundamental component of the decision process related to the exploratory phase. In this paper the two basic components of the exploratory risk: trap geometry and trapped hydrocarbon quantities (fluid), are compounded in a single coherent uncertainty and sensitivity approach. The results clarify that the model geometry influences each Petroleum System Modeling step and that the geometric uncertainty is correlated with the fluid uncertainty. The geometric uncertainty evaluation makes use of geostatistical techniques that produce a number of possible realizations of the trap geometry, all compatible with available data. The evaluation of the fluid uncertainty, through a Monte Carlo methodology, allows us to compute the possible quantities of oil and gas, generated in a basin and migrated from the hydrocarbon source location to each single trap. The final result is the probability distribution of oil and gas for each trap in the basin, together with other useful indicators like: the hydrocarbon filling probability map, the closure probability map, the drainage area probability map, the spilling paths probabilities, the trap-filling scenarios. 相似文献
20.
Jos M. Moreno Maria A. Aramendía Alberto Marinas Jos M. Marinas Francisco J. Urbano 《Applied catalysis. B, Environmental》2005,59(3-4):275-283
The liquid-phase hydrodechlorination of 3-chloropyridine and chlorobenzene has been studied over alkali-modified zirconia-supported palladium catalysts. The modification of the ZrO2 with alkali metal carbonates improves the catalytic activity of the final palladium catalyst. Therefore, the larger the ionic radii (Li+ < Na+ < K+), the greater the catalytic activity (TOF) of the palladium catalyst. For 3-chloropyridine, hydrodechlorination proceeds without catalyst deactivation. This is explained as the result of the interaction of reaction products (pyridine and HCl) forming pyridinium chloride, thus avoiding the detrimental effect of HCl on the palladium particles. Catalytic hydrodechlorination of chlorobenzene over Pd catalysts exhibits an initial catalytic activity (TOF) much lower than that of 3-chloropyridine and the Pd catalysts deactivate as the reaction proceeds. Finally, chlorobenzene hydrodehalogenation has also been carried out in the presence of an equimolecular amount of pyridine resulting in a decrease in the initial reaction rate on the one hand, but also in an increase in final conversion on the other. 相似文献