全文获取类型
收费全文 | 198118篇 |
免费 | 10148篇 |
国内免费 | 4944篇 |
专业分类
电工技术 | 6995篇 |
技术理论 | 11篇 |
综合类 | 9043篇 |
化学工业 | 31023篇 |
金属工艺 | 10910篇 |
机械仪表 | 9941篇 |
建筑科学 | 11166篇 |
矿业工程 | 3743篇 |
能源动力 | 4304篇 |
轻工业 | 10799篇 |
水利工程 | 3121篇 |
石油天然气 | 6830篇 |
武器工业 | 734篇 |
无线电 | 23554篇 |
一般工业技术 | 30625篇 |
冶金工业 | 8687篇 |
原子能技术 | 1559篇 |
自动化技术 | 40165篇 |
出版年
2024年 | 485篇 |
2023年 | 1923篇 |
2022年 | 3195篇 |
2021年 | 4348篇 |
2020年 | 3340篇 |
2019年 | 2779篇 |
2018年 | 17101篇 |
2017年 | 16541篇 |
2016年 | 12750篇 |
2015年 | 4734篇 |
2014年 | 5475篇 |
2013年 | 6821篇 |
2012年 | 10012篇 |
2011年 | 16845篇 |
2010年 | 14693篇 |
2009年 | 11888篇 |
2008年 | 13070篇 |
2007年 | 13616篇 |
2006年 | 6405篇 |
2005年 | 6792篇 |
2004年 | 4923篇 |
2003年 | 4480篇 |
2002年 | 3461篇 |
2001年 | 2943篇 |
2000年 | 3137篇 |
1999年 | 3515篇 |
1998年 | 3021篇 |
1997年 | 2631篇 |
1996年 | 2371篇 |
1995年 | 1956篇 |
1994年 | 1583篇 |
1993年 | 1242篇 |
1992年 | 986篇 |
1991年 | 766篇 |
1990年 | 605篇 |
1989年 | 506篇 |
1988年 | 402篇 |
1987年 | 294篇 |
1986年 | 209篇 |
1985年 | 178篇 |
1984年 | 108篇 |
1983年 | 81篇 |
1982年 | 87篇 |
1981年 | 58篇 |
1980年 | 50篇 |
1968年 | 49篇 |
1966年 | 48篇 |
1965年 | 50篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Statistical machine translation systems are usually trained on large amounts of bilingual text (used to learn a translation
model), and also large amounts of monolingual text in the target language (used to train a language model). In this article
we explore the use of semi-supervised model adaptation methods for the effective use of monolingual data from the source language
in order to improve translation quality. We propose several algorithms with this aim, and present the strengths and weaknesses
of each one. We present detailed experimental evaluations on the French–English EuroParl data set and on data from the NIST
Chinese–English large-data track. We show a significant improvement in translation quality on both tasks. 相似文献
992.
993.
Barrier options are financial derivative contracts that are activated or deactivated according to the crossing of specified
barriers by an underlying asset price. Exact models for pricing barrier options assume continuous monitoring of the underlying
dynamics, usually a stock price. Barrier options in traded markets, however, nearly always assume less frequent observation,
e.g. daily or weekly. These situations require approximate solutions to the pricing problem. We present a new approach to
pricing such discretely monitored barrier options that may be applied in many realistic situations. In particular, we study
daily monitored up-and-out call options of the European type with a single underlying stock. The approach is based on numerical
approximation of the transition probability density associated with the stochastic differential equation describing the stock
price dynamics, and provides accurate results in less than one second whenever a contract expires in a year or less. The flexibility
of the method permits more complex underlying dynamics than the Black and Scholes paradigm, and its relative simplicity renders
it quite easy to implement. 相似文献
994.
Gillian Allard 《AI & Society》2003,17(1):12-24
The power of some new entrants to the music industry derives from their position as brokers in computer-mediated environments.
Brokers act instrumentally to exploit their position within a network which, in turn, depends on their ability to build and
sustain links (and, in computer-mediated environments, hyperlinks). Bricolage in computer-mediated entrepreneurship refers
to the intuitive manipulation of resources in order to achieve (perhaps tacit) goals. Without careful stewardship of the new
intellectual wealth thus created, bricolage may profit neither the individual nor the wider community.
Accepted 14 March 2002 相似文献
995.
燃料变化对气体燃烧器燃烧性能影响的数值模拟研究 总被引:1,自引:0,他引:1
该文以John Zink公司一种瓦斯燃烧器为几何原型,对燃烧器和稳焰旋流器附近三维复杂形状未作任何简化,生成了包括燃烧器和炉膛的结构化网格,换用甲烷、乙烷、丙烷和丁烷四种不同的气体燃料,用标准的k-ε湍流模型、k-ε-g湍流扩散燃烧模型和蒙特卡洛辐射换热模型对燃烧器内的流动及燃烧状况进行了全尺寸数值模拟,预报了燃烧器内流场和温度场,考察燃料变化对炉内温度场的影响规律及燃气射流特性参数(Re·D1)对火焰长度的影响,对进一步优化设计燃烧器、提高加热炉热效率有很好的指导意义。 相似文献
996.
Guillaume Bernard-Granger Christian Guizard Ahmed Addad 《Journal of Materials Science》2007,42(15):6316-6324
Sintering in air of an ultra pure α-alumina powder has been investigated. Isothermal experiments have been conducted on green
samples shaped by slip casting. The grain growth and densification kinetics have been established. The “relative density/grain
size” trajectory, called “sintering path”, has been drawn. Hypotheses concerning the mechanisms controlling grain growth and
densification have been formulated. For the first time, it is shown that grain growth and densification kinetics exhibit two
distinct regimes, where an initial point defect formation step plays a key role. When point defects have been generated, the
diffusion of the associated Al3+ cations controls grain growth and densification. 相似文献
997.
Data collection, both automatic and manual, lies at the heart of all empirical studies. The quality of data collected from
software informs decisions on maintenance, testing and wider issues such as the need for system re-engineering. While of the
two types stated, automatic data collection is preferable, there are numerous occasions when manual data collection is unavoidable.
Yet, very little evidence exists to assess the error-proneness of the latter. Herein, we investigate the extent to which manual
data collection for Java software compared with its automatic counterpart for the same data. We investigate three hypotheses
relating to the difference between automated and manual data collection. Five Java systems were used to support our investigation.
Results showed that, as expected, manual data collection was error-prone, but nowhere near the extent we had initially envisaged.
Key indicators of mistakes in manual data collection were found to be poor developer coding style, poor adherence to sound
OO coding principles, and the existence of relatively large classes in some systems. Some interesting results were found relating
to the collection of public class features and the types of error made during manual data collection. The study thus offers
an insight into some of the typical problems associated with collecting data manually; more significantly, it highlights the
problems that poorly written systems have on the quality of visually extracted data. 相似文献
998.
Colin Fyfe 《Data mining and knowledge discovery》2007,14(2):207-224
We review a new form of self-organizing map which is based on a nonlinear projection of latent points into data space, identical
to that performed in the Generative Topographic Mapping (GTM) [Bishop et al. (1997) Neurl Comput 10(1): 215–234]. But whereas
the GTM is an extension of a mixture of experts, our new model is an extension of a product of experts [Hinton (2000) Technical
report GCNU TR 2000-004, Gatsby Computational Neuroscience Unit, University College, London]. We show visualisation results
on some real data sets and compare with the GTM. We then introduce a second mapping based on harmonic averages and show that
it too creates a topographic mapping of the data. We compare these mappings on real and artificial data sets.
Responsible editor: Soumen Chakrabarti. 相似文献
999.
1000.
Environment as a first class abstraction in multiagent systems 总被引:2,自引:1,他引:1
The current practice in multiagent systems typically associates the environment with resources that are external to agents and their communication infrastructure. Advanced uses of the environment include infrastructures for indirect coordination, such as digital pheromones, or support for governed interaction in electronic institutions. Yet, in general, the notion of environment is not well defined. Functionalities of the environment are often dealt with implicitly or in an ad hoc manner. This is not only poor engineering practice, it also hinders engineers to exploit the full potential of the environment in multiagent systems. In this paper, we put forward the environment as an explicit part of multiagent systems.We give a definition stating that the environment in a multiagent system is a first-class abstraction with dual roles: (1) the environment provides the surrounding conditions for agents to exist, which implies that the environment is an essential part of every multiagent system, and (2) the environment provides an exploitable design abstraction for building multiagent system applications. We discuss the responsibilities of such an environment in multiagent systems and we present a reference model for the environment that can serve as a basis for environment engineering. To illustrate the power of the environment as a design abstraction, we show how the environment is successfully exploited in a real world application. Considering the environment as a first-class abstraction in multiagent systems opens up new horizons for research and development in multiagent systems. 相似文献