全文获取类型
收费全文 | 20835篇 |
免费 | 1881篇 |
国内免费 | 1342篇 |
专业分类
电工技术 | 1636篇 |
技术理论 | 1篇 |
综合类 | 2451篇 |
化学工业 | 735篇 |
金属工艺 | 468篇 |
机械仪表 | 1274篇 |
建筑科学 | 613篇 |
矿业工程 | 304篇 |
能源动力 | 443篇 |
轻工业 | 175篇 |
水利工程 | 411篇 |
石油天然气 | 230篇 |
武器工业 | 153篇 |
无线电 | 1769篇 |
一般工业技术 | 1606篇 |
冶金工业 | 333篇 |
原子能技术 | 53篇 |
自动化技术 | 11403篇 |
出版年
2024年 | 34篇 |
2023年 | 165篇 |
2022年 | 263篇 |
2021年 | 334篇 |
2020年 | 441篇 |
2019年 | 502篇 |
2018年 | 420篇 |
2017年 | 611篇 |
2016年 | 662篇 |
2015年 | 728篇 |
2014年 | 1114篇 |
2013年 | 1591篇 |
2012年 | 1230篇 |
2011年 | 1396篇 |
2010年 | 1055篇 |
2009年 | 1234篇 |
2008年 | 1315篇 |
2007年 | 1407篇 |
2006年 | 1223篇 |
2005年 | 1068篇 |
2004年 | 925篇 |
2003年 | 823篇 |
2002年 | 729篇 |
2001年 | 613篇 |
2000年 | 516篇 |
1999年 | 458篇 |
1998年 | 368篇 |
1997年 | 352篇 |
1996年 | 326篇 |
1995年 | 291篇 |
1994年 | 294篇 |
1993年 | 218篇 |
1992年 | 208篇 |
1991年 | 168篇 |
1990年 | 123篇 |
1989年 | 111篇 |
1988年 | 102篇 |
1987年 | 59篇 |
1986年 | 56篇 |
1985年 | 57篇 |
1984年 | 74篇 |
1983年 | 55篇 |
1982年 | 62篇 |
1981年 | 43篇 |
1980年 | 48篇 |
1979年 | 57篇 |
1978年 | 21篇 |
1977年 | 27篇 |
1976年 | 26篇 |
1975年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
This study proposes a multiperiod mixed integer linear programming model for the management of a single municipal solid waste (MSW) treatment plant with sustainability as the objective. Discrete and continuous variables define the capacity selections for diverse MSW technologies, and the operation of the MSW network, respectively. The economic target is considered to maximize the net present value. The environmental impact is the minimization of a normalized environmental objective function (NEOF). The social target is the maximization of jobs. An interesting feature about the research work is the requirement of biodrying technologies for MSW moisture content control. Due to the conflicted nature among the sustainability components, a multiobjective optimization (MO) is carried out to find the Pareto optimal solutions. The MO results show that the Pareto optimal solutions vary around profit range of $4.9–8.5 billion, NEOF impact range of 3.2–3.6 units, and social benefit range of 2700–4828 jobs. 相似文献
23.
Ching‐Ter Chang 《International Transactions in Operational Research》2021,28(1):493-511
Interval goal programming (IGP) with a marginal penalty function (PF) was first proposed by Charnes and Collomb in 1972, and further improved by Kvanli and other researchers. Recently, Lu and Chen proposed an efficient logarithmic method to formulate IGP with an S‐shaped PF. However, their method requires adding many binary variables when the problem size becomes large, which increases the computational burden in the solution process. This study proposes an efficient approach for the S‐shaped PF. The arbitrary PF frequently appears in the fields of business and industry. However, none of the previous approaches have addressed arbitrary PFs without adding binary variables. The proposed approach can be easily extended to formulate an arbitrary PF in which binary variables are no longer required, regardless of the number of break points. The proposed method can improve the efficiency of IGP for solving large size management and decision problems in considering PFs. In order to demonstrate the correctness, usefulness of the proposed model, illustrative examples are provided. 相似文献
24.
25.
26.
《岩石力学与岩土工程学报(英文版)》2022,14(5):1421-1432
Prediction of mode I fracture toughness (KIC) of rock is of significant importance in rock engineering analyses. In this study, linear multiple regression (LMR) and gene expression programming (GEP) methods were used to provide a reliable relationship to determine mode I fracture toughness of rock. The presented model was developed based on 60 datasets taken from the previous literature. To predict fracture parameters, three mechanical parameters of rock mass including uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), and elastic modulus (E) have been selected as the input parameters. A cluster of data was collected and divided into two random groups of training and testing datasets. Then, different statistical linear and artificial intelligence based nonlinear analyses were conducted on the training data to provide a reliable prediction model of KIC. These two predictive methods were then evaluated based on the testing data. To evaluate the efficiency of the proposed models for predicting the mode I fracture toughness of rock, various statistical indices including coefficient of determination (R2), root mean square error (RMSE), and mean absolute error (MAE) were utilized herein. In the case of testing datasets, the values of R2, RMSE, and MAE for the GEP model were 0.87, 0.188, and 0.156, respectively, while they were 0.74, 0.473, and 0.223, respectively, for the LMR model. The results indicated that the selected GEP model delivered superior performance with a higher R2 value and lower errors. 相似文献
27.
28.
29.
Yujia Wang Tong Wang Xuebo Yang Jiae Yang 《International Journal of Adaptive Control and Signal Processing》2021,35(7):1388-1403
In this article, a decentralized optimal tracking control strategy is proposed for a class of nonlinear systems with tracking error constraints by utilizing adaptive dynamic programming (ADP). It should be noted that ADP technology cannot be directly used to solve decentralized optimal tracking problem of large-scale interconnected nonlinear system with nonzero equilibrium points, since that an infinite domain performance index function may result in an unsolvable solution. In addition, by introducing a smooth function, the constrained tracking error is transformed into an unconstrained one. Then, the error dynamics and a new infinite domain performance index function are designed, such that ADP technology can be used. Following the designed performance index function, the tracking error can be ensured within a small neighborhood of zero. Finally, the feasibility and the effectiveness of the proposed decentralized optimal control scheme are verified through two simulation examples. 相似文献
30.
Yumin Qiu Hongquan Chen Zhaohan Sheng Shuping Cheng 《International Journal of Project Management》2019,37(3):425-443
A significant research gap exists in our understanding of how to govern institutional complexity in megaproject organizations. In this paper, we conduct a case study of the Hong Kong-Zhuhai-Macao Bridge project in order to elaborate on whence institutional complexity emerges and how institutional complexity affects project outcomes and shapes actors' behaviors. We find that institutional complexity stems from both external (macro-level) environments and internal actors (micro-level environments), and consists of regulatory, political, and social complexity and cultural, evolutionary, and relational complexity, respectively. In addition, we find that institutional complexity from the macro environments will result in constraint conflicts in megaproject organizations, whereas the different practices and identities of the project's various micro-actors will create organizational conflicts. We also find that actors within the megaproject organizations choose different responses when faced with different types of institutional complexity. Our approach offers conceptual refinements and a new sensitizing framework for guiding studies of how, in practice, to govern institutional complexity of megaproject organizations. 相似文献