全文获取类型
收费全文 | 149117篇 |
免费 | 20110篇 |
国内免费 | 9596篇 |
专业分类
电工技术 | 54353篇 |
技术理论 | 5篇 |
综合类 | 13020篇 |
化学工业 | 7591篇 |
金属工艺 | 3893篇 |
机械仪表 | 9626篇 |
建筑科学 | 5625篇 |
矿业工程 | 3992篇 |
能源动力 | 10652篇 |
轻工业 | 4688篇 |
水利工程 | 4002篇 |
石油天然气 | 3326篇 |
武器工业 | 1399篇 |
无线电 | 16986篇 |
一般工业技术 | 8170篇 |
冶金工业 | 3502篇 |
原子能技术 | 2374篇 |
自动化技术 | 25619篇 |
出版年
2024年 | 985篇 |
2023年 | 2605篇 |
2022年 | 4697篇 |
2021年 | 5203篇 |
2020年 | 5899篇 |
2019年 | 4889篇 |
2018年 | 4412篇 |
2017年 | 5884篇 |
2016年 | 6378篇 |
2015年 | 7147篇 |
2014年 | 11221篇 |
2013年 | 9803篇 |
2012年 | 12455篇 |
2011年 | 13102篇 |
2010年 | 9345篇 |
2009年 | 9584篇 |
2008年 | 9083篇 |
2007年 | 10452篇 |
2006年 | 9061篇 |
2005年 | 7243篇 |
2004年 | 5894篇 |
2003年 | 4716篇 |
2002年 | 3741篇 |
2001年 | 3175篇 |
2000年 | 2637篇 |
1999年 | 1858篇 |
1998年 | 1391篇 |
1997年 | 1133篇 |
1996年 | 1016篇 |
1995年 | 814篇 |
1994年 | 706篇 |
1993年 | 461篇 |
1992年 | 401篇 |
1991年 | 280篇 |
1990年 | 234篇 |
1989年 | 201篇 |
1988年 | 135篇 |
1987年 | 80篇 |
1986年 | 61篇 |
1985年 | 50篇 |
1984年 | 74篇 |
1983年 | 66篇 |
1982年 | 68篇 |
1981年 | 31篇 |
1980年 | 26篇 |
1979年 | 25篇 |
1978年 | 19篇 |
1977年 | 12篇 |
1959年 | 16篇 |
1951年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
ABSTRACTSocial licence to operate (SLO) is a term that is finding increasing acceptance in a number of industries. Like all new terms, its precise meaning and implications are still being investigated. Using data from previous studies, this paper offers an analysis of the SLO of two case studies with each study being viewed separately through the grid of a distinct theoretical framework. Case study 1 looks at the development of differential social licence negotiated in the Hamlet of Cambridge Bay, Nunavut, as a result of an impact and benefit agreement negotiated between Tahera Diamond Corp. and the Kitikmeot Inuit Organisation in 2004. The study demonstrates that general acceptance of resource development can be uneven and reflect an unequal distribution of decision-making power. In case study 2, stakeholders of a failed mineral development project were queried across time about the specifics of the proposed mine development and were queried about resource development across different levels of consciousness. Perhaps, SLO is variable across different levels of consciousness. The paper concludes with observations about the variable nature of SLO acceptance across populations and across levels of consciousness within individuals. Perhaps, the concept of SLO is, in fact, complex, difficult to define and measure and, at this point, of limited utility as a measure of resource development acceptance. 相似文献
62.
Central force optimization (CFO) is an efficient and powerful population-based intelligence algorithm for optimization problems. CFO is deterministic in nature, unlike the most widely used metaheuristics. CFO, however, is not completely free from the problems of premature convergence. One way to overcome local optimality is to utilize the multi-start strategy. By combining the respective advantages of CFO and the multi-start strategy, a multi-start central force optimization (MCFO) algorithm is proposed in this paper. The performance of the MCFO approach is evaluated on a comprehensive set of benchmark functions. The experimental results demonstrate that MCFO not only saves the computational cost, but also performs better than some state-of-the-art CFO algorithms. MCFO is also compared with representative evolutionary algorithms. The results show that MCFO is highly competitive, achieving promising performance. 相似文献
63.
《Microelectronics Journal》2015,46(11):1012-1019
This paper presents a voltage reference generator architecture and two different realizations of it that have been fabricated within a standard 0.18 μm CMOS technology. The architecture takes the advantage of utilizing a sampled-data amplifier (SDA) to optimize the power consumption. The circuits achieve output voltages on the order of 190 mV with temperature coefficients of 43 ppm/°C and 52.5 ppm/°C over the temperature range of 0 to 120°C without any trimming with a 0.8 V single supply. The power consumptions of the circuits are less then 500 nW while occupying an area of 0.2 mm2 and 0.08 mm2, respectively. 相似文献
64.
This paper addresses the multi-objective optimization problem arising in the operation of heat integrated batch plants, where makespan and utility consumption are the two conflicting objectives. A new continuous-time MILP formulation with general precedence variables is proposed to simultaneously handle decisions related to timing, product sequencing, heat exchanger matches (selected from a two-stage superstructure) and their heat loads. It features a complex set of timing constraints to synchronize heating and cooling tasks, derived from Generalized Disjunctive Programming. Through the solution of an industrial case study from a vegetable oil refinery, we show that major savings in utilities can be achieved while generating the set of Pareto optimal solutions through the ɛ-constraint method. 相似文献
65.
通过计算机模拟金属配合物与核酸作用机理,对其理论模型能量计算和结构优化。在不同的化学环境条件下得到不同的实验模拟结果,对真实的化学反应过程有重要的指导意义和参考意义。通过Gaussian03,Gauss View等软件的结合应用,分别应用于优化计算和理论建模,熟悉了对化学软件操作应用。 相似文献
66.
67.
68.
《The Electricity Journal》2020,33(5):106763
While wind and solar generation has increased dramatically over the past decade, there has been a much larger increase in gas generation (eia, 2019). This is driven in part by low gas prices but also in part by how electricity markets are organized. The intermittent nature of wind and solar generation increases the need for more flexible and reliable generation; a role gas plants fill well. However, current market structures and rules unfairly tip the balance in their favor compared to energy storage systems. They have created market barriers restrictive enough to prevent market participation of a technology key to a 100 % renewable grid: supercapacitors. Adjusting markets to remove the market barriers to supercapacitor and other energy storage systems will allow for increased renewable penetration while simultaneously improving grid performance and reducing costs. 相似文献
69.
近年来,我国传统暴力犯罪与成年人犯罪呈下降态势,但是,犯罪案由层出不穷。为有效提升公安实践工作中犯罪预测能力,打击各类违法犯罪事件,本文针对犯罪数据,提出一种新型犯罪预测模型。利用密度聚类分析方法将犯罪数据分类,然后进行数据降维提取关键属性生成特征数据,继而对特征数据进行加权优化并采用机器学习的方式对特征数据进行学习,从而预测犯罪案由。实验结果表明,与传统方法相比,本文方法具有更好的预测效果,为公安实践工作中类似案件的侦破和预防,提供新的路径支撑。 相似文献
70.