全文获取类型
收费全文 | 5017篇 |
免费 | 307篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 38篇 |
综合类 | 2篇 |
化学工业 | 1446篇 |
金属工艺 | 52篇 |
机械仪表 | 85篇 |
建筑科学 | 183篇 |
矿业工程 | 8篇 |
能源动力 | 177篇 |
轻工业 | 1056篇 |
水利工程 | 49篇 |
石油天然气 | 11篇 |
无线电 | 259篇 |
一般工业技术 | 778篇 |
冶金工业 | 106篇 |
原子能技术 | 21篇 |
自动化技术 | 1061篇 |
出版年
2024年 | 7篇 |
2023年 | 64篇 |
2022年 | 194篇 |
2021年 | 289篇 |
2020年 | 168篇 |
2019年 | 200篇 |
2018年 | 215篇 |
2017年 | 191篇 |
2016年 | 214篇 |
2015年 | 163篇 |
2014年 | 256篇 |
2013年 | 414篇 |
2012年 | 368篇 |
2011年 | 426篇 |
2010年 | 292篇 |
2009年 | 261篇 |
2008年 | 244篇 |
2007年 | 238篇 |
2006年 | 156篇 |
2005年 | 152篇 |
2004年 | 136篇 |
2003年 | 108篇 |
2002年 | 93篇 |
2001年 | 49篇 |
2000年 | 48篇 |
1999年 | 51篇 |
1998年 | 60篇 |
1997年 | 45篇 |
1996年 | 30篇 |
1995年 | 24篇 |
1994年 | 21篇 |
1993年 | 18篇 |
1992年 | 18篇 |
1991年 | 20篇 |
1990年 | 14篇 |
1989年 | 13篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1973年 | 2篇 |
排序方式: 共有5332条查询结果,搜索用时 15 毫秒
81.
Mauthe Andreas Garcia Francisco Hutchison David Yeadon Nicholas 《Multimedia Tools and Applications》2001,13(3):285-306
Multimedia group applications often operate in an environment where the various participants are located on systems and communication links with different capabilities. Mechanisms are required that ensure full-quality media for high-performance workstations but lower-quality media for playout at low-end systems. QoS filters have been proposed as a way to adapt QoS to the user specified level by changing the structure of a media stream in a well defined way. Resource reservation and QoS filter instantiation should be closely integrated since both represent one particular aspect of the provision of individualistic QoS for heterogeneous users in multipeer communications. The Internet reservation protocol RSVP is receiver oriented and allows each receiver to specify its resource requirements. However, no actual mechanisms are defined that adapt the data stream to the receiver specified QoS requirements.In this paper we present an enhanced version of RSVP (called RSVP++) that integrates resource reservation and QoS filter control. In order to achieve this integration we extend the RSVP functional model and define a new QoS service class. RSVP++ can coexist with common RSVP systems, thus, openness and interoperability of the system are ensured. 相似文献
82.
Juan Francisco Gómez-Lopera José Martínez-Aroza Aureliano M. Robles-Pérez Ramón Román-Roldán 《Journal of Mathematical Imaging and Vision》2000,13(1):35-56
This work constitutes a theoretical study of the edge-detection method by means of the Jensen-Shannon divergence, as proposed by the authors. The overall aim is to establish formally the suitability of the procedure of edge detection in digital images, as a step prior to segmentation. In specific, an analysis is made not only of the properties of the divergence used, but also of the method's sensitivity to the spatial variation, as well as the detection-error risk associated with the operating conditions due to the randomness of the spatial configuration of the pixels. Although the paper deals with the procedure based on the Jensen-Shannon divergence, some problems are also related to other methods based on local detection with a sliding window, and part of the study is focused to noisy and textured images. 相似文献
83.
Azzurra Ragone Tommaso Di Noia Eugenio Di Sciascio Francesco M. Donini 《Autonomous Agents and Multi-Agent Systems》2008,16(3):249-270
We present a novel logic-based framework to automate multi-issue bilateral negotiation in e-commerce settings. The approach
exploits logic as communication language among agents, and optimization techniques in order to find Pareto-efficient agreements.
We introduce , a propositional logic extended with concrete domains, which allows one to model relations among issues (both numerical and
non-numerical ones) via logical entailment, differently from well-known approaches that describe issues as uncorrelated. Through
it is possible to represent buyer’s request, seller’s supply and their respective preferences as formulas endowed with a
formal semantics, e.g., “if I spend more than 30000 € for a sedan then I want more than a two-years warranty and a GPS system included”. We mix logic and utility theory in order to express preferences in a qualitative and quantitative way. We illustrate the
theoretical framework, the logical language, the one-shot negotiation protocol we adopt, and show we are able to compute Pareto-efficient
outcomes, using a mediator to solve an optimization problem. We prove the computational adequacy of our method by studying
the complexity of the problem of finding Pareto-efficient solutions in our setting. 相似文献
84.
Formal translations constitute a suitable framework for dealing with many problems in pattern recognition and computational linguistics. The application of formal transducers to these areas requires a stochastic extension for dealing with noisy, distorted patterns with high variability. In this paper, some estimation criteria are proposed and developed for the parameter estimation of regular syntax-directed translation schemata. These criteria are: maximum likelihood estimation, minimum conditional entropy estimation and conditional maximum likelihood estimation. The last two criteria were proposed in order to deal with situations when training data is sparse. These criteria take into account the possibility of ambiguity in the translations: i.e., there can be different output strings for a single input string. In this case, the final goal of the stochastic framework is to find the highest probability translation of a given input string. These criteria were tested on a translation task which has a high degree of ambiguity. 相似文献
85.
Fernández-Miyakawa ME Dorr R Fernández LE Uzal FA Ibarra C 《Computer methods and programs in biomedicine》2007,85(2):95-100
This paper describes the development of a simple system for measurement of net water movement through biological membrane barriers. The system is based on the detection of a water meniscus inside a polyethylene tube, which reflects the water movement inside one hemichamber of a modified Ussing chamber containing a membrane barrier. The detection device consists of a commercial computer-controlled flat bed scanner and specifically developed software. This system allows one to perform a relatively high number of individual experiments per physical unit. It is a flexible and affordable device, which allows comparatively more information per unit to be obtained than previously described methods. 相似文献
86.
Strong encryption is an urgent need for e-commerce development, as it allows the privacy and secure transactions of the financial data. International regulations must allow the spreading of e-commerce and the associated encryption products, in order to establish a secure e-commerce environment that customers can trust and allowing an international deployment of e-commerce solutions without restrictions. 相似文献
87.
Just how insoluble are monoterpenes? 总被引:16,自引:0,他引:16
Jeffrey D. Weidenhamer Francisco A. Macias Nikolaus H. Fischer G. Bruce Williamson 《Journal of chemical ecology》1993,19(8):1799-1807
Prior generalizations about the ecological roles of monoterpenes may be misleading if based on the presumed insolubility of monoterpenes in water. We determined the aqueous solubility of 31 biologically active monoterpenes by gas chromatography. While hydrocarbons were of low solubility (< 35 ppm), oxygenated monoterpenes exhibited solubilities one or two orders of magnitude higher, with ranges of 155–6990 ppm for ketones and of 183–1360 ppm for alcohols. Many monoterpenes are phytotoxic in concentrations under 100 ppm, well below the saturated aqueous concentrations of oxygenated monoterpenes. Therefore, even dilute, unsaturated solutions of monoterpenes, occurring naturally in plant tissues and soil solutions, may act as potent biological inhibitors. 相似文献
88.
ABSTRACT Mexico is a large developing country, much of which is arid and semiarid. With a population of more than 81 million, Mexico is confronted with growing water scarcity and serious pollution of much of its surface water The National Water Commission (Comision Nacional del Agua—CNA) has embarked on a major program of modernization of water management. The water quality program, now consisting of 564 surface water stations (plus 239 groundwater stations), has no strategic design, has major data gaps, is not representative of important areas, is often unreliable, does not contain data for many current issues such as organic contaminants, and suffers from out-of-date or lack of facilities. Because the existing network is not representative of the range of issues for which data are needed, network redesign began from first principles rather than as an optimization of the existing network. The new program is built around client needs, and uses four components—a primary network of some 200 stations that are designed to characterize important water bodies over the long term; a flexible secondary network that focuses on effluent regulatory issues; surveys and special studies for river basin planning and issue-specijic purposes; and a mobile emergency capability. Modernization of the water quality program also includes parallel activities focusing on training, institutional, and legal issues. 相似文献
89.
90.
A multi-objective evolutionary algorithm for an effective tuning of?fuzzy logic controllers in?heating, ventilating and air conditioning systems 总被引:5,自引:5,他引:0
This paper focuses on the use of multi-objective evolutionary algorithms to develop smartly tuned fuzzy logic controllers
dedicated to the control of heating, ventilating and air conditioning systems, energy performance, stability and indoor comfort
requirements. This problem presents some specific restrictions that make it very particular and complex because of the large
time requirements needed to consider multiple criteria (which enlarge the solution search space) and the long computation
time models required in each evaluation. 相似文献