全文获取类型
收费全文 | 3337篇 |
免费 | 223篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 25篇 |
综合类 | 4篇 |
化学工业 | 657篇 |
金属工艺 | 62篇 |
机械仪表 | 85篇 |
建筑科学 | 148篇 |
矿业工程 | 11篇 |
能源动力 | 81篇 |
轻工业 | 444篇 |
水利工程 | 31篇 |
石油天然气 | 5篇 |
无线电 | 290篇 |
一般工业技术 | 687篇 |
冶金工业 | 386篇 |
原子能技术 | 8篇 |
自动化技术 | 641篇 |
出版年
2024年 | 7篇 |
2023年 | 48篇 |
2022年 | 37篇 |
2021年 | 106篇 |
2020年 | 83篇 |
2019年 | 79篇 |
2018年 | 148篇 |
2017年 | 167篇 |
2016年 | 171篇 |
2015年 | 116篇 |
2014年 | 152篇 |
2013年 | 314篇 |
2012年 | 256篇 |
2011年 | 207篇 |
2010年 | 196篇 |
2009年 | 175篇 |
2008年 | 161篇 |
2007年 | 133篇 |
2006年 | 101篇 |
2005年 | 96篇 |
2004年 | 67篇 |
2003年 | 73篇 |
2002年 | 75篇 |
2001年 | 34篇 |
2000年 | 25篇 |
1999年 | 32篇 |
1998年 | 86篇 |
1997年 | 68篇 |
1996年 | 36篇 |
1995年 | 36篇 |
1994年 | 32篇 |
1993年 | 26篇 |
1992年 | 13篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 7篇 |
1988年 | 15篇 |
1987年 | 12篇 |
1986年 | 15篇 |
1985年 | 13篇 |
1984年 | 9篇 |
1983年 | 9篇 |
1982年 | 12篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1976年 | 12篇 |
1974年 | 6篇 |
1973年 | 8篇 |
排序方式: 共有3565条查询结果,搜索用时 15 毫秒
31.
This article addresses the output feedback control for discrete‐time Markov jump linear systems. With fully known transition probability, sufficient conditions for an internal model based controller design are obtained. For the case where the transition probabilities are uncertain and belong to a convex polytope with known vertices, we provide a sufficient LMI condition that guarantees the norm of the closed‐loop system is below a prescribed level. That condition can be improved through an iterative procedure. Additionally, we are able to deal with the case of cluster availability of the Markov mode, provided that some system matrices do not vary within a given cluster, an assumption that is suitable to deal with packet dropout models for networked control systems. A numerical example shows the applicability of the design and compares it with previous results. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
32.
Jesús M. Hermida Santiago Meliá Andrés Montoyo Jaime Gómez 《Information Systems Frontiers》2013,15(3):411-431
Business Intelligence (BI) applications have been gradually ported to the Web in search of a global platform for the consumption and publication of data and services. On the Internet, apart from techniques for data/knowledge management, BI Web applications need interfaces with a high level of interoperability (similar to the traditional desktop interfaces) for the visualisation of data/knowledge. In some cases, this has been provided by Rich Internet Applications (RIA). The development of these BI RIAs is a process traditionally performed manually and, given the complexity of the final application, it is a process which might be prone to errors. The application of model-driven engineering techniques can reduce the cost of development and maintenance (in terms of time and resources) of these applications, as they demonstrated by other types of Web applications. In the light of these issues, the paper introduces the Sm4RIA-B methodology, i.e., a model-driven methodology for the development of RIA as BI Web applications. In order to overcome the limitations of RIA regarding knowledge management from the Web, this paper also presents a new RIA platform for BI, called RI@BI, which extends the functionalities of traditional RIAs by means of Semantic Web technologies and B2B techniques. Finally, we evaluate the whole approach on a case study—the development of a social network site for an enterprise project manager. 相似文献
33.
Lu??s Antunes Armando Matos Alexandre Pinto Andr?? Souto Andreia Teixeira 《Theory of Computing Systems》2013,52(1):162-178
We prove several results relating injective one-way functions, time-bounded conditional Kolmogorov complexity, and time-bounded conditional entropy. First we establish a connection between injective, strong and weak one-way functions and the expected value of the polynomial time-bounded Kolmogorov complexity, denoted here by?E(K t (x|f(x))). These results are in both directions. More precisely, conditions on?E(K t (x|f(x))) that imply that?f is a weak one-way function, and properties of?E(K t (x|f(x))) that are implied by the fact that?f is a strong one-way function. In particular, we prove a separation result: based on the concept of time-bounded Kolmogorov complexity, we find an interval in which every function?f is a necessarily weak but not a strong one-way function. Then we propose an individual approach to injective one-way functions based on Kolmogorov complexity, defining Kolmogorov one-way functions and prove some relationships between the new proposal and the classical definition of one-way functions, showing that a Kolmogorov one-way function is also a deterministic one-way function. A relationship between Kolmogorov one-way functions and the conjecture of polynomial time symmetry of information is also proved. Finally, we relate?E(K t (x|f(x))) and two forms of time-bounded entropy, the unpredictable entropy?H unp, in which ??one-wayness?? of a function can be easily expressed, and the Yao+ entropy, a measure based on compression/decompression schema in which only the decompressor is restricted to be time-bounded. 相似文献
34.
Ana Carolina Lorena André C. P. L. F. de Carvalho João M. P. Gama 《Artificial Intelligence Review》2008,30(1-4):19-37
Several real problems involve the classification of data into categories or classes. Given a data set containing data whose classes are known, Machine Learning algorithms can be employed for the induction of a classifier able to predict the class of new data from the same domain, performing the desired discrimination. Some learning techniques are originally conceived for the solution of problems with only two classes, also named binary classification problems. However, many problems require the discrimination of examples into more than two categories or classes. This paper presents a survey on the main strategies for the generalization of binary classifiers to problems with more than two classes, known as multiclass classification problems. The focus is on strategies that decompose the original multiclass problem into multiple binary subtasks, whose outputs are combined to obtain the final prediction. 相似文献
35.
Sylvain Tourancheau Kjell Brunnström Börje Andrén Patrick Le Callet 《Journal of the Society for Information Display》2009,17(3):239-249
Abstract— The primary goal of this study was to find a measurement method for motion blur which is easy to carry out and gives results that can be reproduced from one lab to another. This method should be able to also take into account methods for reduction of motion blur such as backlight flashing. Two methods have been compared. The first method uses a high‐speed camera that permits us to directly picture the blurred‐edge profile. The second one exploits the mathematical analysis of the motion‐blur formation to construct the blurred‐edge profile from the temporal step response. Measurement results and method proposals are given and discussed. 相似文献
36.
Guilherme T. de Assis Alberto H. F. Laender Marcos André Gonçalves Altigran S. da Silva 《World Wide Web》2009,12(3):285-319
Focused crawlers have as their main goal to crawl Web pages that are relevant to a specific topic or user interest, playing
an important role for a great variety of applications. In general, they work by trying to find and crawl all kinds of pages
deemed as related to an implicitly declared topic. However, users are often not simply interested in any document about a
topic, but instead they may want only documents of a given type or genre on that topic to be retrieved. In this article, we
describe an approach to focused crawling that exploits not only content-related information but also genre information present
in Web pages to guide the crawling process. This approach has been designed to address situations in which the specific topic
of interest can be expressed by specifying two sets of terms, the first describing genre aspects of the desired pages and
the second related to the subject or content of these pages, thus requiring no training or any kind of preprocessing. The
effectiveness, efficiency and scalability of the proposed approach are demonstrated by a set of experiments involving the
crawling of pages related to syllabi of computer science courses, job offers in the computer science field and sale offers
of computer equipments. These experiments show that focused crawlers constructed according to our genre-aware approach achieve
levels of F1 superior to 88%, requiring the analysis of no more than 65% of the visited pages in order to find 90% of the
relevant pages. In addition, we experimentally analyze the impact of term selection on our approach and evaluate a proposed
strategy for semi-automatic generation of such terms. This analysis shows that a small set of terms selected by an expert
or a set of terms specified by a typical user familiar with the topic is usually enough to produce good results and that such
a semi-automatic strategy is very effective in supporting the task of selecting the sets of terms required to guide a crawling
process. 相似文献
37.
Scherer HU Wang J Toes RE van der Woude D Koeleman CA de Boer AR Huizinga TW Deelder AM Wuhrer M 《Proteomics. Clinical applications》2009,3(1):106-115
In several autoimmune disorders, including rheumatoid arthritis (RA), autoantibodies are thought to be the driving force of pathogenicity. Glycosylation of the Fc-part of human Igs is known to modulate biological activity. Hitherto, glycosylation of human IgG-Fc has been analyzed predominantly at the level of total serum IgG, revealing reduced galactosylation in RA. Given the pathogenic relevance of autoantibodies in RA, we wished, in the present study, to address the question whether distinct Fc-glycosylation features are observable at the level of antigen-specific IgG subpopulations. For this purpose, we have developed a method for the microscale purification and Fc-glycosylation analysis of anti-citrullinated peptide antibodies (ACPA). ACPA represent a group of autoantibodies that occur with unique specificity in RA patients. Their presence is associated with increased inflammatory disease activity and rapid joint destruction. Results indicate that ACPA of the IgG1 subclass vary considerably from total serum IgG1 with respect to Fc-galactosylation, with galactosylation being higher on ACPA than on serum IgG1 for some patients, while other patients show higher galactosylation on serum IgG1 than on ACPA. Using this method, studies can be performed on the biological and clinical relevance of ACPA glycosylation within RA patient cohorts. 相似文献
38.
Zinn-Justin Sophie; Pillet Laurence; Ducancel Frdric; Thomas Aline; Smith Jeremy C.; Boulain Jean-Claude; Mnez Andr 《Protein engineering, design & selection : PEDS》1994,7(7):917-923
Structural features associated with the ability of a monoclonalantibody (mAb) to discriminate between protein variants areidentified and engineered. The variants are the curaremimetictoxin from Naja nigricollis and erabutoxin a or b from Laticaudasemifasciata which differ from each other by 16 substitutionsand one insertion. The neutralizing mAb M1 recognizes with highaffinity a topographical epitope on the surface of toxin , butfails to recognize the erabutoxins although they possess mostof the residues forming the presumed epitope. Examinations ofthe toxin and erabutoxin 3-D structures and molecular dynamicssimulations reveal several differences between the variants.In particular, the region involving the ß-turn 1724is organized differently. Analysis of the differences foundin this region suggests that the insertion (or deletion) atposition 18 of the variant amino add sequences is particularlyimportant in determining the differential cross-reactivity.To test this proposal, residue 18 was deleted in one erabutoxinusing sitedirected mutagenesis, and the biological propertiesof the resulting mutant were examined. We found that full antigenicitywas restored in the previously unrecognized variant. The implicationsof this finding are discussed. 相似文献
39.
The Genetic Heterogeneity among Different Mouse Strains Impacts the Lung Injury Potential of Multiwalled Carbon Nanotubes 下载免费PDF全文
Xiang Wang Yu‐Pei Liao Donatello Telesca Chong Hyun Chang Tian Xia André E. Nel 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(33)
Genetic variation constitutes an important variable impacting the susceptibility to inhalable toxic substances and air pollutants, as reflected by epidemiological studies in humans and differences among animal strains. While multiwalled carbon nanotubes (MWCNTs) are capable of causing lung fibrosis in rodents, it is unclear to what extent the genetic variation in different mouse strains influence the outcome. Four inbred mouse strains, including C57Bl/6, Balb/c, NOD/ShiLtJ, and A/J, to test the pro‐fibrogenic effects of a library of MWCNTs in vitro and in vivo are chosen. Ex vivo analysis of IL‐1β production in bone marrow‐derived macrophages (BMDMs) as molecular initiating event (MIE) is performed. The order of cytokine production (Balb/c > A/J > C57Bl/6 > NOD/ShiLtJ) in BMDMs is also duplicated during assessment of IL‐1β production in the bronchoalveolar lavage fluid of the same mouse strains 40 h after oropharyngeal instillation of a representative MWCNT. Animal test after 21 d also confirms a similar hierarchy in TGF‐β1 production and collagen deposition in the lung. Statistical analysis confirms a correlation between IL‐1β production in BMDM and the lung fibrosis. All considered, these data demonstrate that genetic background indeed plays a major role in determining the pro‐fibrogenic response to MWCNTs in the lung. 相似文献
40.
George André Tonini Luís Augusto Martins Ruotolo 《Clean Technologies and Environmental Policy》2017,19(2):403-415
Heavy metal removal from industrial wastewaters has been intensively studied, since it is well known that they can cause severe problems to human health and aquatic life, even at very low concentrations. In this work, it was demonstrated that electrodeposition in fluidized bed electrode (FBE) can be efficiently employed to remove metal ions from solution, avoid contamination, and recover the metal. Copper electrodeposition from diluted solutions was efficiently performed using a membraneless FBE. The average current efficiency (ACE), average energy consumption (AEC), and space–time yield (AY) was optimized taking into account the operational and process variables. It was noted that for all response variables studied, the raise of supporting electrolyte concentration (C s) contributed to improvements in the process. The operational conditions current (I) and bed expansion (E) determined the values of CE, Y, and EC under activated control, but the initial copper concentration (C 0) determined how long the electrodeposition process will work under activated or mass transfer control, thus affecting the average values of CE, Y, and EC. Considering C 0 of 500 mg L?1, copper can be optimally recovered with ACE >60 %, AY >38 kg h?1 m?3, and AEC <4.0 kWh kg?1 by applying the lowest I and the highest levels of E and C s. It was concluded that the electrochemical technology using a membraneless FBE reactor is economically competitive and be applied for the treatment of wastewaters contaminated with copper or other metals. 相似文献