全文获取类型
收费全文 | 8497篇 |
免费 | 395篇 |
国内免费 | 192篇 |
专业分类
电工技术 | 114篇 |
综合类 | 647篇 |
化学工业 | 513篇 |
金属工艺 | 86篇 |
机械仪表 | 333篇 |
建筑科学 | 595篇 |
矿业工程 | 254篇 |
能源动力 | 258篇 |
轻工业 | 155篇 |
水利工程 | 2032篇 |
石油天然气 | 2050篇 |
武器工业 | 66篇 |
无线电 | 161篇 |
一般工业技术 | 274篇 |
冶金工业 | 132篇 |
原子能技术 | 75篇 |
自动化技术 | 1339篇 |
出版年
2024年 | 10篇 |
2023年 | 57篇 |
2022年 | 112篇 |
2021年 | 129篇 |
2020年 | 190篇 |
2019年 | 144篇 |
2018年 | 190篇 |
2017年 | 182篇 |
2016年 | 251篇 |
2015年 | 280篇 |
2014年 | 447篇 |
2013年 | 363篇 |
2012年 | 533篇 |
2011年 | 669篇 |
2010年 | 469篇 |
2009年 | 439篇 |
2008年 | 398篇 |
2007年 | 484篇 |
2006年 | 425篇 |
2005年 | 459篇 |
2004年 | 365篇 |
2003年 | 347篇 |
2002年 | 241篇 |
2001年 | 266篇 |
2000年 | 271篇 |
1999年 | 263篇 |
1998年 | 223篇 |
1997年 | 164篇 |
1996年 | 176篇 |
1995年 | 146篇 |
1994年 | 86篇 |
1993年 | 85篇 |
1992年 | 69篇 |
1991年 | 25篇 |
1990年 | 18篇 |
1989年 | 24篇 |
1988年 | 12篇 |
1987年 | 9篇 |
1986年 | 7篇 |
1985年 | 10篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 18篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有9084条查询结果,搜索用时 15 毫秒
1.
2.
4.
This study demonstrates the application of an improved Evolutionary optimization Algorithm (EA), titled Multi-Objective Complex Evolution Global Optimization Method with Principal Component Analysis and Crowding Distance Operator (MOSPD), for the hydropower reservoir operation of the Oroville–Thermalito Complex (OTC) – a crucial head-water resource for the California State Water Project (SWP). In the OTC's water-hydropower joint management study, the nonlinearity of hydropower generation and the reservoir's water elevation–storage relationship are explicitly formulated by polynomial function in order to closely match realistic situations and reduce linearization approximation errors. Comparison among different curve-fitting methods is conducted to understand the impact of the simplification of reservoir topography. In the optimization algorithm development, techniques of crowding distance and principal component analysis are implemented to improve the diversity and convergence of the optimal solutions towards and along the Pareto optimal set in the objective space. A comparative evaluation among the new algorithm MOSPD, the original Multi-Objective Complex Evolution Global Optimization Method (MOCOM), the Multi-Objective Differential Evolution method (MODE), the Multi-Objective Genetic Algorithm (MOGA), the Multi-Objective Simulated Annealing approach (MOSA), and the Multi-Objective Particle Swarm Optimization scheme (MOPSO) is conducted using the benchmark functions. The results show that best the MOSPD algorithm demonstrated the best and most consistent performance when compared with other algorithms on the test problems. The newly developed algorithm (MOSPD) is further applied to the OTC reservoir releasing problem during the snow melting season in 1998 (wet year), 2000 (normal year) and 2001 (dry year), in which the more spreading and converged non-dominated solutions of MOSPD provide decision makers with better operational alternatives for effectively and efficiently managing the OTC reservoirs in response to the different climates, especially drought, which has become more and more severe and frequent in California. 相似文献
5.
Clustering is a solution for classifying enormous data when there is not any early knowledge about classes. With emerging new concepts like cloud computing and big data and their vast applications in recent years, research works have been increased on unsupervised solutions like clustering algorithms to extract knowledge from this avalanche of data. Clustering time-series data has been used in diverse scientific areas to discover patterns which empower data analysts to extract valuable information from complex and massive datasets. In case of huge datasets, using supervised classification solutions is almost impossible, while clustering can solve this problem using un-supervised approaches. In this research work, the focus is on time-series data, which is one of the popular data types in clustering problems and is broadly used from gene expression data in biology to stock market analysis in finance. This review will expose four main components of time-series clustering and is aimed to represent an updated investigation on the trend of improvements in efficiency, quality and complexity of clustering time-series approaches during the last decade and enlighten new paths for future works. 相似文献
6.
7.
8.
通过大量野外工程地质勘察与测试工作,在此基础上给出了横泉水库供水发电洞的工程地质分析与评价,从而使该水库的施工有了充分的理论依据。 相似文献
9.
10.
应用试井方法,提出一套比较切合实际的小块气藏动态特征综合评价方法,推导出水驱气藏水侵量的计算公式,编制了天然气高压物性参数计算和气藏稳产年限预测等程序软件。 相似文献