全文获取类型
收费全文 | 21190篇 |
免费 | 2607篇 |
国内免费 | 1795篇 |
专业分类
电工技术 | 1966篇 |
技术理论 | 2篇 |
综合类 | 1526篇 |
化学工业 | 1414篇 |
金属工艺 | 515篇 |
机械仪表 | 1885篇 |
建筑科学 | 1515篇 |
矿业工程 | 710篇 |
能源动力 | 406篇 |
轻工业 | 816篇 |
水利工程 | 654篇 |
石油天然气 | 661篇 |
武器工业 | 124篇 |
无线电 | 2550篇 |
一般工业技术 | 1231篇 |
冶金工业 | 741篇 |
原子能技术 | 58篇 |
自动化技术 | 8818篇 |
出版年
2024年 | 94篇 |
2023年 | 276篇 |
2022年 | 559篇 |
2021年 | 555篇 |
2020年 | 638篇 |
2019年 | 557篇 |
2018年 | 564篇 |
2017年 | 665篇 |
2016年 | 744篇 |
2015年 | 891篇 |
2014年 | 1548篇 |
2013年 | 1449篇 |
2012年 | 1880篇 |
2011年 | 2011篇 |
2010年 | 1536篇 |
2009年 | 1457篇 |
2008年 | 1389篇 |
2007年 | 1514篇 |
2006年 | 1222篇 |
2005年 | 1059篇 |
2004年 | 840篇 |
2003年 | 721篇 |
2002年 | 641篇 |
2001年 | 494篇 |
2000年 | 388篇 |
1999年 | 363篇 |
1998年 | 269篇 |
1997年 | 263篇 |
1996年 | 239篇 |
1995年 | 151篇 |
1994年 | 116篇 |
1993年 | 94篇 |
1992年 | 60篇 |
1991年 | 46篇 |
1990年 | 30篇 |
1989年 | 39篇 |
1988年 | 23篇 |
1987年 | 13篇 |
1986年 | 12篇 |
1985年 | 23篇 |
1984年 | 13篇 |
1983年 | 14篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1979年 | 6篇 |
1965年 | 13篇 |
1963年 | 9篇 |
1955年 | 11篇 |
1954年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
In this paper, we investigate how adaptive operator selection techniques are able to efficiently manage the balance between exploration and exploitation in an evolutionary algorithm, when solving combinatorial optimization problems. We introduce new high level reactive search strategies based on a generic algorithm's controller that is able to schedule the basic variation operators of the evolutionary algorithm, according to the observed state of the search. Our experiments on SAT instances show that reactive search strategies improve the performance of the solving algorithm. 相似文献
2.
Klaus Reinhardt Hans Georg Breunig Aisada Uchugonova Karsten K?nig 《Journal of the Royal Society Interface》2015,12(110)
We explore the possibility of characterizing sperm cells without the need to stain them using spectral and fluorescence lifetime analyses after multi-photon excitation in an insect model. The autofluorescence emission spectrum of sperm of the common bedbug, Cimex lectularius, was consistent with the presence of flavins and NAD(P)H. The mean fluorescence lifetimes showed smaller variation in sperm extracted from the male (tau m, τm = 1.54–1.84 ns) than in that extracted from the female sperm storage organ (tau m, τm = 1.26–2.00 ns). The fluorescence lifetime histograms revealed four peaks. These peaks (0.18, 0.92, 2.50 and 3.80 ns) suggest the presence of NAD(P)H and flavins and show that sperm metabolism can be characterized using fluorescence lifetime imaging. The difference in fluorescence lifetime variation between the sexes is consistent with the notion that female animals alter the metabolism of sperm cells during storage. It is not consistent, however, with the idea that sperm metabolism represents a sexually selected character that provides females with information about the male genotype. 相似文献
3.
Data fitting with B-splines is a challenging problem in reverse engineering for CAD/CAM, virtual reality, data visualization, and many other fields. It is well-known that the fitting improves greatly if knots are considered as free variables. This leads, however, to a very difficult multimodal and multivariate continuous nonlinear optimization problem, the so-called knot adjustment problem. In this context, the present paper introduces an adapted elitist clonal selection algorithm for automatic knot adjustment of B-spline curves. Given a set of noisy data points, our method determines the number and location of knots automatically in order to obtain an extremely accurate fitting of data. In addition, our method minimizes the number of parameters required for this task. Our approach performs very well and in a fully automatic way even for the cases of underlying functions requiring identical multiple knots, such as functions with discontinuities and cusps. To evaluate its performance, it has been applied to three challenging test functions, and results have been compared with those from other alternative methods based on AIS and genetic algorithms. Our experimental results show that our proposal outperforms previous approaches in terms of accuracy and flexibility. Some other issues such as the parameter tuning, the complexity of the algorithm, and the CPU runtime are also discussed. 相似文献
4.
We investigate the problem of efficient wireless power transfer in wireless sensor networks. In our approach, special mobile entities (called the Mobile Chargers) traverse the network and wirelessly replenish the energy of sensor nodes. In contrast to most current approaches, we envision methods that are distributed and use limited network information. We propose four new protocols for efficient charging, addressing key issues which we identify, most notably (i) what are good coordination procedures for the Mobile Chargers and (ii) what are good trajectories for the Mobile Chargers. Two of our protocols (DC, DCLK) perform distributed, limited network knowledge coordination and charging, while two others (CC, CCGK) perform centralized, global network knowledge coordination and charging. As detailed simulations demonstrate, one of our distributed protocols outperforms a known state of the art method, while its performance gets quite close to the performance of the powerful centralized global knowledge method. 相似文献
5.
在分析单一MU(Most Uncertainty)采样缺陷的基础上,提出一种"全局最优搜寻"方法 GOS(Global Optimal Search),并结合MU共同完成查询选择。GOS+MU方法中,GOS着眼全局寻找目标,在应用环境能提供的训练样本数量有限、分类器受训不充分时,该方法选择的对象学习价值高,能快速推进分类器学习进程;MU则能够在GOS采样失效情形下,利用分类器当前训练成果,选择查询不确定性最强的样本补充训练集。通过对网络商品的用户评论进行分类仿真,并比较其他采样学习方法的效果,证明了GOS+MU方法在压缩学习成本、提高训练效率方面的有效性。 相似文献
6.
7.
宁东供水工程供水水泵共有卧式和立式离心泵2种方案可供选择,也是工程论证时争论的焦点,经综合比较及主机设备的国际招标,最终确定了奥地利安德里兹公司的卧式双吸中开式离心泵为宁东供水工程的供水水泵。 相似文献
8.
This study addresses the problem of choosing the most suitable probabilistic model selection criterion for unsupervised learning
of visual context of a dynamic scene using mixture models. A rectified Bayesian Information Criterion (BICr) and a Completed
Likelihood Akaike’s Information Criterion (CL-AIC) are formulated to estimate the optimal model order (complexity) for a given
visual scene. Both criteria are designed to overcome poor model selection by existing popular criteria when the data sample
size varies from small to large and the true mixture distribution kernel functions differ from the assumed ones. Extensive
experiments on learning visual context for dynamic scene modelling are carried out to demonstrate the effectiveness of BICr
and CL-AIC, compared to that of existing popular model selection criteria including BIC, AIC and Integrated Completed Likelihood
(ICL). Our study suggests that for learning visual context using a mixture model, BICr is the most appropriate criterion given
sparse data, while CL-AIC should be chosen given moderate or large data sample sizes. 相似文献
9.
从政策、城市与区域规划、环境、文化及其传承因素、基础设施等方面探析了高校新校区选址有关的主要影响因素,以满足高等学校大规模的扩建要求,促进高等教育的发展。 相似文献
10.
Chih-Ming Chen Hahn-Ming Lee Chia-Chen Tan 《Engineering Applications of Artificial Intelligence》2006,19(8):967-978
The explosion of on-line information has given rise to many manually constructed topic hierarchies (such as Yahoo!!). But with the current growth rate in the amount of information, manual classification in topic hierarchies results in an immense information bottleneck. Therefore, developing an automatic classifier is an urgent need. However, classifiers suffer from enormous dimensionality, since the dimensionality is determined by the number of distinct keywords in a document corpus. More seriously, most classifiers are either working slowly or they are constructed subjectively without any learning ability. In this paper, we address these problems with a fair feature-subset selection (FFSS) algorithm and an adaptive fuzzy learning network (AFLN) for classification. The FFSS algorithm is used to reduce the enormous dimensionality. It not only gives fair treatment to each category but also has ability to identify useful features, including both positive and negative features. On the other hand, the AFLN provides extremely fast learning ability to model the uncertain behavior for classification so as to correct the fuzzy matrix automatically. Experimental results show that both FFSS algorithm and the AFLN lead to a significant improvement in document classification, compared to alternative approaches. 相似文献