全文获取类型
收费全文 | 25439篇 |
免费 | 3872篇 |
国内免费 | 2316篇 |
专业分类
电工技术 | 4404篇 |
综合类 | 3422篇 |
化学工业 | 1176篇 |
金属工艺 | 559篇 |
机械仪表 | 1777篇 |
建筑科学 | 1029篇 |
矿业工程 | 700篇 |
能源动力 | 686篇 |
轻工业 | 1293篇 |
水利工程 | 746篇 |
石油天然气 | 602篇 |
武器工业 | 371篇 |
无线电 | 2720篇 |
一般工业技术 | 1992篇 |
冶金工业 | 451篇 |
原子能技术 | 97篇 |
自动化技术 | 9602篇 |
出版年
2024年 | 63篇 |
2023年 | 348篇 |
2022年 | 750篇 |
2021年 | 890篇 |
2020年 | 911篇 |
2019年 | 874篇 |
2018年 | 816篇 |
2017年 | 1000篇 |
2016年 | 1170篇 |
2015年 | 1283篇 |
2014年 | 1687篇 |
2013年 | 1760篇 |
2012年 | 2191篇 |
2011年 | 2342篇 |
2010年 | 1823篇 |
2009年 | 1837篇 |
2008年 | 1881篇 |
2007年 | 2115篇 |
2006年 | 1713篇 |
2005年 | 1305篇 |
2004年 | 956篇 |
2003年 | 731篇 |
2002年 | 613篇 |
2001年 | 467篇 |
2000年 | 391篇 |
1999年 | 261篇 |
1998年 | 228篇 |
1997年 | 216篇 |
1996年 | 183篇 |
1995年 | 143篇 |
1994年 | 115篇 |
1993年 | 104篇 |
1992年 | 84篇 |
1991年 | 73篇 |
1990年 | 74篇 |
1989年 | 55篇 |
1988年 | 40篇 |
1987年 | 20篇 |
1986年 | 30篇 |
1985年 | 10篇 |
1984年 | 19篇 |
1983年 | 6篇 |
1982年 | 12篇 |
1981年 | 4篇 |
1980年 | 10篇 |
1979年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1966年 | 2篇 |
1961年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 50 毫秒
71.
介绍了赵庄煤矿主斜井长运距带式输送机系统的构成,通过变频器在输送系统上的应用实践,表明该变频驱动技术具有先进性。 相似文献
72.
基于均匀设计的边坡稳定性敏感性分析 总被引:5,自引:0,他引:5
在边坡敏感性分析中,试验方法的选择对试验次数和试验效果起决定作用。均匀设计能使试验点在试验范围内均匀分布,将此试验方法引入到边坡敏感性分析中,可以大大减少试验次数,获得较好的试验效果。以一均质土坡为例,选取容重、内摩擦角、黏聚力、坡角、地震加速度等5个因素来设计数值试验,对边坡进行了敏感性分析。结果表明,在常见的均质土坡或松散堆积体岩土质边坡中,黏聚力、坡角和内摩擦角为最敏感因素;在抗震设防烈度为7度以下的一般岩土体地区,土的重度和地震加速度为不敏感因素。该结论对边坡的综合治理、安全监测和灾害预报具有一定意义。 相似文献
73.
74.
Participants' usage of informational variables in learning visual relative-mass discrimination in collisions was tracked by means of PROBIT correlations. Four groups received feedback that was true or accorded with either of three nonspecificational cue variables. A majority in each group adopted the feedback, but several participants defied the false feedback. Unlike in previous research, the fit to data of the relative-mass invariant could not be bettered by post hoc linear combinations of the cues. Discriminability was lower in the use of the invariant. Analytic complexity was rejected as an explanation for discriminability differences. A "smart mechanism" for pickup of the relative-mass invariant was developed as an extension of G. Johansson's (1950/1994) vector model. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
75.
In this paper, we propose an approach that combines the unsupervised and supervised learning techniques for unconstrained
handwritten numeral recognition. This approach uses the Kohonen self-organizing neural network for data classification in
the first stage and the learning vector quantization (LVQ) model in the second stage to improve classification accuracy. The
combined architecture performs better than the Kohonen self-organizing map alone. In the proposed approach, the collection
of centroids at different phases of training plays a vital role in the performance of the recognition system. Four experiments
have been conducted and experimental results show that the collection of centroids in the middle of the training gives high
performance in terms of speed and accuracy. The systems developed also resolve the confusion between handwritten numerals. 相似文献
76.
以某工程钻爆参数为例,阐述了在地下工程掘进施工中,应用回归分析法建立钻爆参数的相关模型,并利用此模型帮助建立某断面钻爆方案. 相似文献
77.
研究了支撑矢量机的分类机理,并利用支撑矢量机对雷达目标一维像进行了识别.识别的结果表明了该方法的优越性,并显示它可以对残缺不全的样本进行识别. 相似文献
78.
79.
Modelling the rate of secondary succession after farmland abandonment in a Mediterranean mountain area 总被引:1,自引:0,他引:1
Secondary succession after farmland abandonment has become a common process in north Mediterranean countries, especially in mountain areas. In this paper, a methodology is tested which combines Markov chains and logistic multivariate regression to model secondary succession after farmland abandonment in environments where abiotic constraints play a major role, like mountain areas. In such landscapes, a decay in the succession rate with time is usually found, as the best locations are progressively occupied. This is frequently addressed using non-stationary Markov chains. Here, we test if the combination of logistic multivariate regression with Markov chains, however, allows for spatially distributed transitions probabilities based on abiotic factors and therefore, it is able to reproduce the preferential colonization of the most favourable locations. The model is tested in the Ijuez Valley in the Spanish Pyrenees, which underwent generalized land abandonment during the 1950s. Results confirm a substantial improvement in the prediction success of the Markov-logistic model when compared to the standard Markov chain approach. As a result, the decay in the succession rate can be successfully modelled. The specific results for our study area are discussed further in an ecological context. The methodology proposed is applicable to any landscape where vegetation dynamics are constrained by environmental factors. However, the inclusion of land use as an explanatory factor would be necessary in human-managed landscapes. 相似文献
80.
偏最小二乘回归的应变统计模型研究 总被引:1,自引:0,他引:1
在应变监控模型中,各因子之间存在着多重相关性,将会严重影响参数估计、扩大模型误差、破坏模型的稳健性,为了克服多重相关性对模型的干扰.引入了能辨别系统信息与噪声的偏最小二乘回归.研究分析表明,与普通的最小二乘回归相比,偏最小二乘回归模型具有很好的稳定性. 相似文献