全文获取类型
收费全文 | 44878篇 |
免费 | 4416篇 |
国内免费 | 2983篇 |
专业分类
电工技术 | 3129篇 |
综合类 | 5644篇 |
化学工业 | 3810篇 |
金属工艺 | 1580篇 |
机械仪表 | 2534篇 |
建筑科学 | 5395篇 |
矿业工程 | 2264篇 |
能源动力 | 1314篇 |
轻工业 | 2188篇 |
水利工程 | 1654篇 |
石油天然气 | 1292篇 |
武器工业 | 346篇 |
无线电 | 3187篇 |
一般工业技术 | 3297篇 |
冶金工业 | 1856篇 |
原子能技术 | 387篇 |
自动化技术 | 12400篇 |
出版年
2024年 | 127篇 |
2023年 | 405篇 |
2022年 | 802篇 |
2021年 | 917篇 |
2020年 | 1029篇 |
2019年 | 948篇 |
2018年 | 891篇 |
2017年 | 1159篇 |
2016年 | 1353篇 |
2015年 | 1590篇 |
2014年 | 2456篇 |
2013年 | 2427篇 |
2012年 | 3002篇 |
2011年 | 3504篇 |
2010年 | 2691篇 |
2009年 | 3058篇 |
2008年 | 2997篇 |
2007年 | 3512篇 |
2006年 | 3085篇 |
2005年 | 2720篇 |
2004年 | 2241篇 |
2003年 | 2040篇 |
2002年 | 1586篇 |
2001年 | 1372篇 |
2000年 | 1101篇 |
1999年 | 933篇 |
1998年 | 649篇 |
1997年 | 652篇 |
1996年 | 546篇 |
1995年 | 500篇 |
1994年 | 383篇 |
1993年 | 284篇 |
1992年 | 255篇 |
1991年 | 204篇 |
1990年 | 156篇 |
1989年 | 151篇 |
1988年 | 103篇 |
1987年 | 96篇 |
1986年 | 44篇 |
1985年 | 32篇 |
1984年 | 51篇 |
1983年 | 34篇 |
1982年 | 25篇 |
1981年 | 22篇 |
1980年 | 27篇 |
1979年 | 18篇 |
1977年 | 13篇 |
1975年 | 11篇 |
1963年 | 8篇 |
1961年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
1.
2.
3.
The Vehicle Routing Problem with Simultaneous Pickup and Delivery (VRPSPD) is an extension to the classical Vehicle Routing Problem (VRP), where customers may both receive and send goods simultaneously. The Vehicle Routing Problem with Mixed Pickup and Delivery (VRPMPD) differs from the VRPSPD in that the customers may have either pickup or delivery demand. However, the solution approaches proposed for the VRPSPD can be directly applied to the VRPMPD. In this study, an adaptive local search solution approach is developed for both the VRPSPD and the VRPMPD, which hybridizes a Simulated Annealing inspired algorithm with Variable Neighborhood Descent. The algorithm uses an adaptive threshold function that makes the algorithm self-tuning. The proposed approach is tested on well-known VRPSPD and VRPMPD benchmark instances derived from the literature. The computational results indicate that the proposed algorithm is effective in solving the problems in reasonable computation time. 相似文献
4.
This paper presents a model of shell and tube evaporator with micro-fin tubes using R1234yf and R134a. The model developed for this evaporator uses the ε-NTU method to predict the evaporating pressure, the refrigerant outlet enthalpy and the outlet temperature of the secondary fluid. The model accuracy is evaluated using different two-phase flow boiling correlations for micro-fin tubes and comparing predicted and experimental data. The experimental tests were carried out for a wide range of operating conditions using R134a and R1234yf as working fluids. The predicted parameter with maximum deviations, between the predicted and experimental data, is the evaporating pressure. The correlation of Akhavan– Behabadi et al. was used to predict flow boiling heat transfer, with an error on cooling capacity prediction below 5%. Simulations, carried out with this validated model, show that the overall heat transfer coefficient of R1234yf has a maximum decrease of 10% compared with R134a. 相似文献
5.
Load testing of applications is an important and costly activity for software provider companies. Classical solutions are very difficult to set up statically, and their cost is prohibitive in terms of both human and hardware resources. Virtualized cloud computing platforms provide new opportunities for stressing an application's scalability, by providing a large range of flexible and less expensive (pay‐per‐use model) computation units. On the basis of these advantages, load testing solutions could be provided on demand in the cloud. This paper describes a Benchmark‐as‐a‐Service solution that automatically scales the load injection platform and facilitates its setup according to load profiles. Our approach is based on: (i) virtualization of the benchmarking platform to create self‐scaling injectors; (ii) online calibration to characterize the injector's capacity and impact on the benched application; and (iii) a provisioning solution to appropriately scale the load injection platform ahead of time. We also report experiments on a benchmark illustrating the benefits of this system in terms of cost and resource reductions. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
6.
7.
8.
9.
10.
带隔板底水油藏油井临界产量计算公式 总被引:25,自引:9,他引:16
本给出了带隔板底水油藏油井的监界产量计算公式,它适用于所有带隔板底水油藏的油井。 相似文献