全文获取类型
收费全文 | 249475篇 |
免费 | 22917篇 |
国内免费 | 11176篇 |
专业分类
电工技术 | 20705篇 |
技术理论 | 32篇 |
综合类 | 25196篇 |
化学工业 | 29786篇 |
金属工艺 | 10061篇 |
机械仪表 | 13217篇 |
建筑科学 | 34097篇 |
矿业工程 | 13763篇 |
能源动力 | 10015篇 |
轻工业 | 17259篇 |
水利工程 | 12336篇 |
石油天然气 | 12824篇 |
武器工业 | 3421篇 |
无线电 | 16753篇 |
一般工业技术 | 19081篇 |
冶金工业 | 12658篇 |
原子能技术 | 1914篇 |
自动化技术 | 30450篇 |
出版年
2024年 | 1129篇 |
2023年 | 3341篇 |
2022年 | 6251篇 |
2021年 | 8142篇 |
2020年 | 8223篇 |
2019年 | 6132篇 |
2018年 | 5816篇 |
2017年 | 7215篇 |
2016年 | 8804篇 |
2015年 | 9443篇 |
2014年 | 17146篇 |
2013年 | 15347篇 |
2012年 | 18130篇 |
2011年 | 19851篇 |
2010年 | 14597篇 |
2009年 | 14950篇 |
2008年 | 13694篇 |
2007年 | 16754篇 |
2006年 | 15194篇 |
2005年 | 13233篇 |
2004年 | 11008篇 |
2003年 | 9473篇 |
2002年 | 7687篇 |
2001年 | 6381篇 |
2000年 | 5369篇 |
1999年 | 4199篇 |
1998年 | 2975篇 |
1997年 | 2574篇 |
1996年 | 2107篇 |
1995年 | 1770篇 |
1994年 | 1477篇 |
1993年 | 1046篇 |
1992年 | 854篇 |
1991年 | 600篇 |
1990年 | 514篇 |
1989年 | 480篇 |
1988年 | 279篇 |
1987年 | 214篇 |
1986年 | 177篇 |
1985年 | 205篇 |
1984年 | 150篇 |
1983年 | 133篇 |
1982年 | 74篇 |
1981年 | 80篇 |
1980年 | 90篇 |
1979年 | 39篇 |
1978年 | 21篇 |
1977年 | 24篇 |
1964年 | 16篇 |
1959年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
《Food Control》2015
The aim of the study was to investigate annual and regional differences in the level of aflatoxin B1 (AFB1) in grains and dairy cattle feed. Maize (n = 972), wheat (n = 201), barley (n = 147), oat (n = 136), grain mixtures (n = 168), and dairy cattle feed (n = 325) were sampled from 2009 to 2013 on different farms and in different farm factories situated in four Croatian regions. The samples were analysed for AFB1 using the validated ELISA immunoassay. AFB1 was determined in 16.4% of all investigated samples, among which maize was proven to be the most contaminated, with 21.7% of the samples recovered during 2013 harbouring AFB1 in concentrations over the permissible ones. Levels higher than permitted were observed in 17.9% and 12.3% of grain mixtures and dairy cattle feed, respectively, whereas concentrations of AFB1 determined in other crops throughout the investigated period met the stipulated requirements. The results revealed the AFB1 occurrence to be significantly (p < 0.05) dependent on the cultivation region, with the highest levels generally found in maize harvested in 2013 and consequently in grain mixtures and cattle feed that can most likely be associated with climatic conditions as the most critical factor for mould formation, and thus also AFB1 production. 相似文献
52.
为检查工程质量,查找输水系统可能存在的问题并消除隐患,保障电站安全运行,福建仙游抽水蓄能电站在投产发电前,要对输水发电系统进行充水试验与放空排水试验,在试验过程中监测输水系统的应力、应变与渗漏水情况。本文以尾水系统为例,介绍了试验所应具备的工程条件、工作程序及技术要求、试验成果分析和存在问题处理等。试验表明,仙游抽水蓄能电站尾水系统设计合理,施工质量优良,结构可靠,可供同类工程参考与借鉴。 相似文献
53.
氢工质在新能源与动力、航天推进、化工材料等领域有着广泛应用。通过开展高温氢工质热力学与输运性质研究,建立了原子态氢、分子态氢、热解平衡态氢的热物理性质计算模型,开发了热物性计算程序Prop_H_H2,适用范围为温度100~3 500 K、压力104~5×107 Pa 。验证表明,Prop_H_H2在适用范围内计算氢工质的物性参数合理可靠,在温度200~3 000 K、压力104~107 Pa范围内,程序预测值更加准确,相对偏差在±5%左右。本研究可为氢工质相关的航天推进、应用物理学、能源动力等行业的科研和应用提供支持借鉴。 相似文献
54.
55.
Reliability based criteria are quite popular for optimal sensor network design. We present a modified definition of system reliability for sensor network design for two applications: reliable estimation of variables in a steady state linear flow process, and reliable fault detection and diagnosis for any process. Unlike the weakest-link based definition of system reliability in the literature, the proposed definition considers the entire system and is consistent with the reliability concept used in classical reliability literature. For each application, dual approaches for defining system reliability are proposed, and their analogy with the reliability problem in the classical reliability literature is established. Using examples and stochastic simulations, the advantage of using the proposed system reliability in contrast to the existing definition is illustrated. Part II of this series of articles presents methods for efficient generation of the system reliability function and its use in optimization-based approaches for designing optimal sensor networks. 相似文献
56.
Fault detection and isolation in water distribution networks is an active topic due to the nonlinearities of flow propagation and recent increases in data availability due to sensor deployment. Here, we propose an efficient two-step data driven alternative: first, we perform sensor placement taking the network topology into account; second, we use incoming sensor data to build a network model through online dictionary learning. Online learning is fast and allows tackling large networks as it processes small batches of signals at a time. This brings the benefit of continuous integration of new data into the existing network model, either in the beginning for training or in production when new data samples are gathered. The proposed algorithms show good performance in our simulations on both small and large-scale networks. 相似文献
57.
文章通过对黑龙江省高效节水现状,存在问题的分析,结合黑龙江省高效节水发展的支撑能力,阐述黑龙江省节水增粮目标、任务及总体布局,为黑龙江省2012—2015年节水增粮实施提供依据。 相似文献
58.
Robert Brooke Manrico Fabretto Samuel Pering Eliza Switalska Lachlan Reeks Drew Evans Peter Murphy 《应用聚合物科学杂志》2015,132(26)
A study using three different pairs of electrochromic polymers (ECPs) synthesized onto plaques by means of a modified vapor phase polymerization (VPP) technique is presented. Restriction of the respective polymerization times, allowed both faster and slower polymerizing monomers to be controlled, and produced blended plaques with visually diffuse interfaces. The ECPs within the blended plaques retain their individual electrochromic behavior and when encapsulated into an electrochromic device, show outstanding optical switching performance with little degradation evident over 10,000 cycles, coupled with a switching time of the order of 1 second. Blends also allow multiple diffuse color changes within an electrochromic device, due to the difference in oxidation potentials of the individual ECPs, making them candidates for adaptive camouflage use. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42158. 相似文献
59.
60.
Controllability and observability of multi-agent systems with heterogeneous and switching topologies
ABSTRACTThis paper focuses on controllability and observability of multi-agent systems with heterogeneous and switching topologies, where the first- and the second-order information interaction topologies are different and switching. First, based on the controllable state set, a controllability criterion is obtained in terms of the controllability matrix corresponding to the switching sequence. Next, by virtue of the subspace sequence, two necessary and sufficient algebraic conditions are established for controllability in terms of the system matrices corresponding to all the possible topologies. Furthermore, controllability is considered from the graphic perspective. It is proved that the system is controllable if the union graph of all the possible topologies is controllable. With respect to observability, two sufficient and necessary conditions are derived by taking advantage of the system matrices and the corresponding invariant subspace, respectively. Finally, some simulation examples are worked out to illustrate the theoretical results. 相似文献