全文获取类型
收费全文 | 38976篇 |
免费 | 4655篇 |
国内免费 | 2631篇 |
专业分类
电工技术 | 5561篇 |
技术理论 | 6篇 |
综合类 | 3182篇 |
化学工业 | 2013篇 |
金属工艺 | 315篇 |
机械仪表 | 1565篇 |
建筑科学 | 4982篇 |
矿业工程 | 2497篇 |
能源动力 | 1311篇 |
轻工业 | 4030篇 |
水利工程 | 2595篇 |
石油天然气 | 1335篇 |
武器工业 | 448篇 |
无线电 | 2942篇 |
一般工业技术 | 2554篇 |
冶金工业 | 889篇 |
原子能技术 | 1012篇 |
自动化技术 | 9025篇 |
出版年
2024年 | 109篇 |
2023年 | 604篇 |
2022年 | 1201篇 |
2021年 | 1503篇 |
2020年 | 1544篇 |
2019年 | 1173篇 |
2018年 | 1132篇 |
2017年 | 1391篇 |
2016年 | 1581篇 |
2015年 | 1726篇 |
2014年 | 3298篇 |
2013年 | 2686篇 |
2012年 | 3462篇 |
2011年 | 3084篇 |
2010年 | 2431篇 |
2009年 | 2340篇 |
2008年 | 2337篇 |
2007年 | 2697篇 |
2006年 | 2250篇 |
2005年 | 1968篇 |
2004年 | 1606篇 |
2003年 | 1379篇 |
2002年 | 1067篇 |
2001年 | 808篇 |
2000年 | 608篇 |
1999年 | 480篇 |
1998年 | 347篇 |
1997年 | 280篇 |
1996年 | 216篇 |
1995年 | 213篇 |
1994年 | 169篇 |
1993年 | 131篇 |
1992年 | 89篇 |
1991年 | 65篇 |
1990年 | 43篇 |
1989年 | 43篇 |
1988年 | 45篇 |
1987年 | 18篇 |
1986年 | 18篇 |
1985年 | 25篇 |
1984年 | 17篇 |
1983年 | 17篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 10篇 |
1979年 | 9篇 |
1978年 | 7篇 |
1973年 | 3篇 |
1959年 | 7篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
The perpetual energy production of a wind farm could be accomplished (under proper weather conditions) if no failures occurred. But even the best possible design, manufacturing, and maintenance of a system cannot eliminate the failure possibility. In order to understand and minimize the system failures, the most crucial components of the wind turbines, which are prone to failures, should be identified. Moreover, it is essential to determine and classify the criticality of the system failures according to the impact of these failure events on wind turbine safety. The present study is processing the failure data from a wind farm and uses the Fault Tree Analysis as a baseline for applying the Design Structure Matrix technique to reveal the failure and risk interactions between wind turbine subsystems. Based on the analysis performed and by introducing new importance measures, the “readiness to fail” of a subsystem in conjunction with the “failure riskiness” can determine the “failure criticality.” The value of the failure criticality can define the frame within which interventions could be done. The arising interventions could be applied either to the whole system or could be focused in specified pairs of wind turbine subsystems. In conclusion, the method analyzed in the present research can be effectively applied by the wind turbine manufacturers and the wind farm operators as an operation framework, which can lead to a limited (as possible) design‐out maintenance cost, failures' minimization, and safety maximization for the whole wind turbine system. 相似文献
32.
Maria Grazia Basanisi Gianfranco La Bella Gaia Nobili Rosa Coppola Annita Maria Damato Maria Assunta Cafiero Giovanna La Salandra 《International Journal of Food Science & Technology》2020,55(3):1145-1150
The authenticity and traceability of meat products are issues of primary importance to ensure food safety. Unfortunately, food adulteration (e.g. the addition of inexpensive cuts to minced meat products) and mislabelling (e.g. the inclusion of meat from species other than those declared) happens frequently worldwide. The aim of this study was to apply a droplet digital PCR assay for the detection and quantification (copies μL−1) of the beef, pork, horse, sheep, chicken and turkey in meat products. The analysis conducted on commercial meat showed the presence of traces of DNA from other animal species than those declared. We show that the method is highly sensitive, specific and accurate (accuracy = 100%). This method could be adopted by competent food safety authorities to verify compliance with the labelling of meat products and to ensure quality and safety throughout the meat supply chain, from primary production to consumption. 相似文献
33.
为了保障浓香菜籽油的产品质量安全,采用HACCP体系对浓香菜籽油生产全过程进行生物、物理、化学的危害分析,确定关键控制点,制定预防措施,并对生产环节进行有效监控,制定纠偏措施,做好记录管理,为浓香菜籽油的安全生产提供借鉴。 相似文献
34.
为了使城市湖泊尽可能滞蓄雨洪、发挥景观功能、打造良好的居民"亲水空间",以枝江市金湖为例,根据金湖主要泄洪渠道的实际情况,利用Mike 21模型模拟计算汛限水位值,按照景观水位确定大、小洪水工况下合理的水位。在此基础上,提出传统的静态景观水位与改进的动态景观水位两种方案。结果表明:以50年一遇、30年一遇为代表的大洪水工况下合理景观水位为40.7 m,以20年一遇、10年一遇为代表的小洪水工况合理景观水位为41.3 m;静态方案采用50年一遇洪水计算结果为标准执行,将40.7 m作为金湖固定的景观水位;动态方案水位可在41.3~40.7 m之间波动;金湖适宜采用动态景观水位运行方案,水位可在40.7~41.3 m之间波动;根据短期预报及历史监测资料分析后合理调度,将41.3 m作为金湖常水位,确定预测洪水大小后调整水位迎战洪水。据此,可在充分利用水资源的同时有效协调景观高水位需求与防洪之间的矛盾。 相似文献
35.
The scheduling problems under distributed production or flexible assembly settings have achieved increasing attention in recent years. This paper considers scheduling the integration of these two environments and proposes an original distributed flowshop scheduling problem with flexible assembly and set-up time. Distributed production stage is deployed several homogeneous flowshop factories that process the jobs to be assembled into final products in the flexible assembly stage. The objective is to find a schedule, including a production subschedule for jobs and an assembly subschedule for products, to minimise the makespan. Such a scheduling problem involves four successive decisions: assigning jobs to production factories, sequencing jobs at every factory, designating an assembly machine for each product and sequencing products on each assembly machine. The computational model is first established, and then a constructive heuristic (TPHS) and two hybrid metaheuristics (HVNS and HPSO) are proposed. Numerical experiments have been carried out and results validate the algorithmic feasibility and effectiveness. TPHS can obtain reasonable solutions in a shorter time, while metaheuristics can report better solutions using more yet acceptable time. HPSO is statistically comparable yet less robust compared with HVNS for small-scale instances. For the large-scale case, HPSO outperforms HVNS on both effectiveness and robustness. 相似文献
36.
Jinghu Hu David M. Christopher Xuefang Li 《International Journal of Hydrogen Energy》2018,43(29):13649-13658
Various reduced-order models have been developed to quickly model high pressure underexpanded jets. One example is the two-layer partitioning model which was developed to model underexpanded jets, but it has not been evaluated for high pressure jets with obstacles in the jet flow region. This research describes an improved two-layer partitioning model based on the Abel-Noble equation of state that is applied here to model horizontal jet flows impacting a vertical obstacle with validations against high pressure gas experiments, full CFD simulations and a revised notional nozzle model based on the Abel-Noble equation of state. The improved two-layer partitioning model accurately predicts the gas concentrations on the obstacle for a 15 MPa underexpanded jet while consuming much less computational resources and time compared with the full CFD simulation. 相似文献
37.
在流程工业生产中,移动物料计量信息的传输普遍采用电台和无线模块。接收电台周围环境严重影响计量信息的传输效果,尤其是钢结构厂房、电磁干扰区内,数据传输过程中的丢包率、误码率相当严重。本文提出一种多节点分布式传输方法,根据各个生产作业区环境条件设置相应的WIFI节点数,实现对作业区的无线信号覆盖。网络覆盖区内无线模块、PDA终端(PDA)、终端查询设备通过节点工作频段和阵列天线自适应调节,实现数据传输最佳化。铜熔炼生产现场测试表明,此种传输方法可以有效消除周围环境的电磁干扰,数据丢包率低于0.1%。 相似文献
38.
39.
40.
This paper proposes a method for the coordinated control of power factor by means of a multiagent approach. The proposed multiagent system consists of two types of agent: single feeder agent (F_AG) and bus agent (B_AG). In the proposed system, an F_AG plays as an important role, which decides the power factors of all distributed generators by executing the load flow calculations repeatedly. The voltage control strategies are implemented as the class definition of Java into the system. In order to verify the performance of the proposed method, it has been applied to a typical distribution model system. The simulation results show that the system is able to control very violent fluctuation of the demands and the photovoltaic (PV) generations. 相似文献