全文获取类型
收费全文 | 36561篇 |
免费 | 3192篇 |
国内免费 | 1741篇 |
专业分类
电工技术 | 3031篇 |
技术理论 | 12篇 |
综合类 | 3264篇 |
化学工业 | 1952篇 |
金属工艺 | 578篇 |
机械仪表 | 1232篇 |
建筑科学 | 10095篇 |
矿业工程 | 1256篇 |
能源动力 | 698篇 |
轻工业 | 917篇 |
水利工程 | 4369篇 |
石油天然气 | 1227篇 |
武器工业 | 148篇 |
无线电 | 2329篇 |
一般工业技术 | 1509篇 |
冶金工业 | 1166篇 |
原子能技术 | 121篇 |
自动化技术 | 7590篇 |
出版年
2024年 | 43篇 |
2023年 | 284篇 |
2022年 | 677篇 |
2021年 | 751篇 |
2020年 | 816篇 |
2019年 | 648篇 |
2018年 | 672篇 |
2017年 | 782篇 |
2016年 | 1060篇 |
2015年 | 1272篇 |
2014年 | 3234篇 |
2013年 | 2248篇 |
2012年 | 2987篇 |
2011年 | 3200篇 |
2010年 | 2702篇 |
2009年 | 2787篇 |
2008年 | 2534篇 |
2007年 | 2956篇 |
2006年 | 2298篇 |
2005年 | 1891篇 |
2004年 | 1591篇 |
2003年 | 1385篇 |
2002年 | 1086篇 |
2001年 | 829篇 |
2000年 | 591篇 |
1999年 | 438篇 |
1998年 | 306篇 |
1997年 | 259篇 |
1996年 | 241篇 |
1995年 | 176篇 |
1994年 | 140篇 |
1993年 | 108篇 |
1992年 | 59篇 |
1991年 | 46篇 |
1990年 | 34篇 |
1989年 | 43篇 |
1988年 | 31篇 |
1987年 | 21篇 |
1986年 | 17篇 |
1985年 | 39篇 |
1984年 | 27篇 |
1983年 | 41篇 |
1982年 | 14篇 |
1981年 | 11篇 |
1980年 | 9篇 |
1979年 | 8篇 |
1965年 | 13篇 |
1963年 | 9篇 |
1958年 | 6篇 |
1955年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
经济新常态下,我国建筑行业得到快速发展。对于建筑工程来说,为节约成本,在"限额设计"思想指导下,必须开展精细化管理,从而提高项目投资的控制能力。然而,在项目建设过程中对于"限额设计"措施的利用水平并不高,不利于企业的可持续发展。因此,本文在分析"限额设计"措施的基础上,提出对建设项目投资的控制对策,希望能够对相关施工管理人员提供借鉴。 相似文献
12.
Kelly Yujie Wang Yuan Wen Tsz Leung Yip Meifeng Luo 《International Transactions in Operational Research》2020,27(5):2658-2682
As nonrecourse project finance (rather than financing on a sovereign basis) is becoming more prevalent worldwide, financing institutions have to collaborate more closely with firms to optimize capacity‐investment and financing decisions. Under this background, this paper presents a stylized Stackelberg games model, taking into account the firm's capacity investment as well as the bank's interest rate and funding ratio decisions. Consortium structures between bank and firm are formalized into five modes based on industry practice, namely, the integrated consortium, pure shareholder funding, bank as leader, full coordination, and bank as follower. The optimality and equilibrium of each of the five modes are analytically derived, and their existence and uniqueness are demonstrated. Valuable economic insights are obtained through both modeling analysis and numerical experiments, with the main findings including the following: (i) a lack of bank financing leads to insufficient capacity investment and poor consortium performance; (ii) interest rate and funding ratio play important but different roles in the bank's risk management; (iii) the bank's proactivity in leading and coordinating the consortium is critical for the two parties’ overall performance; and (iv) if the bank is the follower, the firm's capacity decision is irrelevant to the bank's loan contract, and the consortium cannot be coordinated to the first‐best level of performance. 相似文献
13.
Secondary risk in project risk management refers to the risk that arises as a direct result of implementing a risk response action (RRA). It is important for project managers (PMs) to consider the effects caused by the secondary risks in the process of RRA selection. The purpose of this paper is to propose an optimization method to address the problem of selecting risk response actions (RRAs) with consideration of secondary risk which is seldom considered in the existing studies. The optimization model aims to minimize the total risk costs with time constraint being placed on the project makespan. By solving the model, an optimal set of RRAs along with the earliest start time for each activity can both be obtained. The results show that secondary risk plays an important role in the process of RRA selection. Project managers should allocate more budget for responding the project risk when the secondary risk is considered, and consider all factors relating to both time and cost so as to select appropriate RRAs to mitigate primary risk and secondary risk. 相似文献
14.
15.
ABSTRACTFeature selection is an important task to improve the classifier’s accuracy and to decrease the problem size. A number of methodologies have been presented for feature selection problems using metaheuristic algorithms. In this paper, an improved self-adaptive inertia weight particle swarm optimisation with local search and combined with C4.5 classifiers for feature selection algorithm is proposed. In this proposed algorithm, the gradient base local search with its capacity of helping to explore the feature space and an improved self-adaptive inertia weight particle swarm optimisation with its ability to converge a best global solution in the search space. Experimental results have verified that the SIW-APSO-LS performed well compared with other state of art feature selection techniques on a suit of 16 standard data sets. 相似文献
16.
17.
王鹏翃 《中国水能及电气化》2020,(4):37-40
在地下隧洞施工输水整个环节中,施工环境复杂多变。由于地质岩体结构应力、地下水以及岩体力学构造等各方面的不确定、不稳定因素的影响极大,如果仅依靠传统经验来进行管理,已经不符合现代化管理的最基本要求,也无法达到标准化管理。文章首先阐述了地下输水隧洞围岩稳定监测系统设计的目的,然后对设计输水隧洞围岩稳定监测系统进行了分析,以便及时正确掌控地下输水的隧洞围岩发展状态,保证隧洞施工的顺利完成。 相似文献
18.
水利工程的特殊性,决定了其在安全管理构建中更加注重全过程管理机制的构建,以及危险源下的精准安全管控。在传统安全管理模式之下,水利工程安全管理盲点多、效率低,不利于全过程安全管理的高效实施。文章立足水利工程的危险辨识,分析了水利工程危险源全过程安全管理中的问题,并在此基础之上,从强化危险源精准辨识、构建危险源动态管理机制、优化危险源评价工作、加快危险源信息库建设等方面,具体论述了危险源下水利工程全过程安全管理措施。 相似文献
19.
To improve the convertibility of reconfigurable manufacturing system (RMS), the concept of delayed reconfigurable manufacturing system (D-RMS) was proposed. RMS and D-RMS are both constructed around part family. However, D-RMS may suffer from ultra-long system problem with unacceptable idle machines using generic RMS part families. Besides, considering the complex basic system structure of D-RMS, machine selection of D-RMS should be addressed, including dedicated machine, flexible machine, and reconfigurable machine. Therefore, a system design method for D-RMS based on part family grouping and machine selection is proposed. Firstly, a part family grouping method is proposed for D-RMS that groups the parts with more former common operations into the same part family. The concept of longest relative position common operation subsequence (LPCS) is proposed. The similarity coefficient among the parts is calculated based on LPCS. The reciprocal value of the operation position of LPCS is adopted as the characteristic value. The average linkage clustering (ALC) algorithm is used to cluster the parts. Secondly, a machine selection method is proposed to complete the system design of D-RMS, including machine selection rules and the dividing point decision model. Finally, a case study is given to implement and verify the proposed system design method for D-RMS. The results show that the proposed system design method is effective, which can group parts with more former common operations into the same part family and select appropriate machine types. 相似文献
20.