全文获取类型
收费全文 | 2601篇 |
免费 | 126篇 |
国内免费 | 21篇 |
专业分类
电工技术 | 39篇 |
综合类 | 18篇 |
化学工业 | 683篇 |
金属工艺 | 57篇 |
机械仪表 | 47篇 |
建筑科学 | 81篇 |
矿业工程 | 7篇 |
能源动力 | 74篇 |
轻工业 | 328篇 |
水利工程 | 28篇 |
石油天然气 | 27篇 |
武器工业 | 2篇 |
无线电 | 253篇 |
一般工业技术 | 307篇 |
冶金工业 | 494篇 |
原子能技术 | 18篇 |
自动化技术 | 285篇 |
出版年
2023年 | 15篇 |
2022年 | 82篇 |
2021年 | 110篇 |
2020年 | 62篇 |
2019年 | 46篇 |
2018年 | 66篇 |
2017年 | 62篇 |
2016年 | 57篇 |
2015年 | 68篇 |
2014年 | 80篇 |
2013年 | 135篇 |
2012年 | 104篇 |
2011年 | 132篇 |
2010年 | 98篇 |
2009年 | 127篇 |
2008年 | 105篇 |
2007年 | 127篇 |
2006年 | 91篇 |
2005年 | 74篇 |
2004年 | 69篇 |
2003年 | 84篇 |
2002年 | 75篇 |
2001年 | 52篇 |
2000年 | 41篇 |
1999年 | 32篇 |
1998年 | 172篇 |
1997年 | 108篇 |
1996年 | 101篇 |
1995年 | 58篇 |
1994年 | 42篇 |
1993年 | 49篇 |
1992年 | 18篇 |
1991年 | 17篇 |
1990年 | 15篇 |
1989年 | 13篇 |
1988年 | 8篇 |
1987年 | 14篇 |
1986年 | 13篇 |
1985年 | 13篇 |
1984年 | 6篇 |
1983年 | 9篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 11篇 |
1978年 | 7篇 |
1977年 | 12篇 |
1976年 | 22篇 |
1973年 | 3篇 |
1971年 | 7篇 |
排序方式: 共有2748条查询结果,搜索用时 22 毫秒
51.
Sequential learning is the discipline of machine learning that deals with dependent data such that neighboring labels exhibit some kind of relationship. The paper main contribution is two-fold: first, we generalize the stacked sequential learning, highlighting the key role of neighboring interactions modeling. Second, we propose an effective and efficient way of capturing and exploiting sequential correlations that takes into account long-range interactions. We tested the method on two tasks: text lines classification and image pixel classification. Results on these tasks clearly show that our approach outperforms the standard stacked sequential learning as well as state-of-the-art conditional random fields. 相似文献
52.
Relevance feedback has recently emerged as a solution to the problem of improving the retrieval performance of an image retrieval
system based on low-level information such as color, texture and shape features. Most of the relevance feedback approaches
limit the utilization of the user’s feedback to a single search session, performing a short-term learning. In this paper we
present a novel approach for short and long term learning, based on the definition of an adaptive similarity metric and of
a high level representation of the images. For short-term learning, the relevant and non-relevant information given by the
user during the feedback process is employed to create a positive and a negative subspace of the feature space. For long-term
learning, the feedback history of all the users is exploited to create and update a representation of the images which is
adopted for improving retrieval performance and progressively reducing the semantic gap between low-level features and high-level
semantic concepts. The experimental results prove that the proposed method outperforms many other state of art methods in
the short-term learning, and demonstrate the efficacy of the representation adopted for the long-term learning.
相似文献
Annalisa FrancoEmail: |
53.
基于实体模型的三维真实感流动模拟软件的研究与开发 总被引:6,自引:0,他引:6
注射成型的流动模拟在预测复杂薄壁型腔的流动行为方面已经比较准确。现行的数值方法主要采用基于中性层的有限元/有限差分/控制体积法,但中性层模型的引入使得模拟软件在应用中具有极大的局限性。本文采用实体模型取代中性层模型,开发了三维真实感流动模拟软件。最后,应用实例证明此模型能够处理由流行CAD系统生成的复杂型腔模型。 相似文献
54.
Justin Trumpickas Amanda Smith Melissa M. Robillard Jake K.L. La Rose 《Journal of Great Lakes research》2012
Nearshore small fish species represent a large proportion of fish biodiversity in Lake Simcoe, a large inland lake in southern Ontario, Canada. Over the past 30 years, Lake Simcoe has experienced several changes to its aquatic habitat, benthic invertebrate communities and predatory fish populations. This study compared samples of the nearshore small fish community in three geographic areas of Lake Simcoe. Fish community data were grouped into two time periods: a contemporary period (2007–2009) and a historical period (1982–1995). The fish community was compared across time periods for each area to assess if observed ecological changes had an impact on the small fish community. Species richness significantly declined between time periods in two areas (Cook's Bay and the southeast shoreline), the number of individuals captured declined between time periods in one area of the lake (Kempenfelt Bay) and Simpson's diversity index declined between time periods in one area of the lake (southeast shoreline). There were no significant differences in the Shannon–Weiner evenness index between time periods in any of the study areas. Additional analyses of intra- and inter-annual variation in fish sampling results generally supported the findings that shifts in the fish community occurred between time periods. Overall, this study suggests that the nearshore small fish biodiversity of Lake Simcoe has shifted over time but these shifts are not clearly related to recent increases in water clarity, macrophyte growth and nearshore benthic invertebrate densities. 相似文献
55.
56.
Roberto da Costa Quinino Linda Lee Ho Anderson Laécio Galindo Trindade 《The International Journal of Advanced Manufacturing Technology》2014,72(1-4):101-106
This paper presents an approach for improving the control limits of $ \overline{X} $ control charts when the parameters of the process are estimated and the control chart is in operation. In these conditions, the observed average run length (ARL) may be very different from the planned ARL since the parameter estimates may have a larger error. To minimize this problem, the data collected in effective control (phase 2) will be used to re-estimate the parameters with a precision greater than that obtained in phase 1. Thus, we defined a minimum sample size of observations of phase 2, which is constituted of a mixture of two normal distributions that should be used to re-estimate the process parameters. The proposal is illustrated with numerical example. 相似文献
57.
Methodology for the reliability evaluation of a passive system and its integration into a Probabilistic Safety Assessment 总被引:2,自引:0,他引:2
Michel Marqus J.F. Pignatel P. Saignes F. DAuria L. Burgazzi C. Müller R. Bolado-Lavin C. Kirchsteiger V. La Lumia I. Ivanov 《Nuclear Engineering and Design》2005,235(24):1864-2631
A methodology has been developed to evaluate the reliability of passive systems characterised by a moving fluid and whose operation is based on thermal–hydraulic (T-H) principles. The methodology includes:
- • identification and quantification of the sources of uncertainties and determination of the important variables;
- • propagation of the uncertainties through T-H models and assessment of T-H passive system unreliability;
- • introduction of passive system unreliability in the accident sequence analysis.
58.
59.
基于遗传算法的分布式异构数据库的查询优化 总被引:2,自引:1,他引:2
对于分布武异构数据库,查询优化问题是其核心问题。本文用基于位、值结构树型编码的遗传算法对分布武异构数据库进行查询优化,取得了很好的效果。 相似文献
60.
Fatigue of bituminous mixtures 总被引:1,自引:0,他引:1
H. Di Benedetto C. de La Roche H. Baaj A. Pronk R. Lundström 《Materials and Structures》2004,37(3):202-216
This paper presents an interlaboratory test campaign organized by the RILEM 182-PEB Technical Committee. In the campaign,
11 different test methods, comprising uniaxial tension/compression, 2-, 3- and 4-point bending and indirecttension tests,
were utilized in order to investigate fatigue characteristics of a dense graded asphalt concrete mixture. The testing conditions
specified were sinusoidal excitation at 10Hz and 10°C using controlled strain and stress modes. In total, more than 150 fatigue
tests were carried out during the investigation. The fatigue test results were analyzed using both classical as well as continuum
damage mechanics approaches. The fatigue test results obtained using the classical fatigue approach are considerably influenced
by test type and mode of loading (controlled stress or strain) used. Consequently, this approach has limited use in realistic
fatigue characterization of bituminous materials and pavement structures. In contrast to the classical approach, models founded
on continuum damage theory may serve to isolate intrinsic fatigue characteristics from the influence of so-called biased effects,
which are largely caused by the accelerated laboratory testing. The continuum damage models investigated may constitute steps,
towards a rational mechanistic fatigue characterization model, which are important for effective future pavement design. 相似文献