全文获取类型
收费全文 | 145079篇 |
免费 | 18006篇 |
国内免费 | 9301篇 |
专业分类
电工技术 | 8861篇 |
技术理论 | 16篇 |
综合类 | 14749篇 |
化学工业 | 19686篇 |
金属工艺 | 3847篇 |
机械仪表 | 6761篇 |
建筑科学 | 11455篇 |
矿业工程 | 4556篇 |
能源动力 | 3456篇 |
轻工业 | 11784篇 |
水利工程 | 3862篇 |
石油天然气 | 3980篇 |
武器工业 | 1949篇 |
无线电 | 14904篇 |
一般工业技术 | 12384篇 |
冶金工业 | 7624篇 |
原子能技术 | 1035篇 |
自动化技术 | 41477篇 |
出版年
2024年 | 259篇 |
2023年 | 2011篇 |
2022年 | 4073篇 |
2021年 | 6122篇 |
2020年 | 4714篇 |
2019年 | 4281篇 |
2018年 | 4397篇 |
2017年 | 5460篇 |
2016年 | 7111篇 |
2015年 | 7904篇 |
2014年 | 10556篇 |
2013年 | 10619篇 |
2012年 | 10436篇 |
2011年 | 9930篇 |
2010年 | 7953篇 |
2009年 | 8307篇 |
2008年 | 8146篇 |
2007年 | 9971篇 |
2006年 | 9325篇 |
2005年 | 8086篇 |
2004年 | 6314篇 |
2003年 | 5718篇 |
2002年 | 4158篇 |
2001年 | 3180篇 |
2000年 | 2314篇 |
1999年 | 1884篇 |
1998年 | 1321篇 |
1997年 | 1126篇 |
1996年 | 960篇 |
1995年 | 841篇 |
1994年 | 805篇 |
1993年 | 589篇 |
1992年 | 434篇 |
1991年 | 379篇 |
1990年 | 324篇 |
1989年 | 285篇 |
1988年 | 211篇 |
1987年 | 144篇 |
1986年 | 129篇 |
1985年 | 131篇 |
1984年 | 149篇 |
1983年 | 121篇 |
1982年 | 96篇 |
1981年 | 65篇 |
1980年 | 82篇 |
1964年 | 88篇 |
1962年 | 87篇 |
1961年 | 62篇 |
1959年 | 64篇 |
1955年 | 71篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
本文建立了PC结构施工全过程的BIM模型及有限元分析模型,对施工过程进行数值模拟与动态、静态监测,对装配式结构进行了结构性能评价,为结构可视化施工监测提供了技术支持。 相似文献
62.
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
63.
64.
臭氧氧化-循环喷淋法处理钨钼选矿废水 总被引:4,自引:0,他引:4
采用臭氧氧化-循环喷淋法去除钨钼选矿废水中COD,研究了pH值、臭氧流量、循环频率对COD去除效果的影响。结果表明: 废水COD去除率随pH值、臭氧流量、循环频率增大而增加,在pH值为10、臭氧流量3.0 L/min、循环频率4.0次/min条件下,氧化120 min后废水COD含量由131 mg/L降至11.5 mg/L,COD去除率达91.2%,满足《污水综合排放标准》(GB 8978-1996)一级标准。与O2、NaClO处理废水COD的对比试验结果表明,循环喷淋法结合O3表现出较好的COD去除效果。 相似文献
65.
针对采取小批量间歇性批次生产方式、工艺介质腐蚀性强、危险性大的小型特种精细化工生产工艺研究试验过程自动化、信息化程度不高,导致工艺研究试验中获取数据较少、过程机理研究不够透彻、人工操作多、安全风险高、研究试验消耗大及效率不高等问题,综述了期待通过智能控制、在线分析、模拟仿真和虚拟制造、工况监测及预测性维护以及信息管理和生产调度等关键技术的研究和应用,提高小型特种精细化工生产工艺过程的自动化和信息化程度,实现小型特种精细化工生产工艺过程的数字化、虚拟化和智能化,降低生产安全风险和试验消耗,提高小型特种精细化工生产工艺研究试验的成功率和效率,达到小型特种精细化工生产工艺过程的数字化设计和精准生产的目标。 相似文献
66.
文章首先总结了电力企业信息管理系统的现状,提出了多源信息管理系统融合集成的邦联、子集和完全融合3种方式,分析了3种方式的优缺点,以建设企业"互联网搜索"型数字引擎为目标,提出了融合基于本体的图数据库建模,多维关联与路径因果分析,和人机共生互动可视化决策于一体的企业信息管理系统技术发展趋势;在系统分析目前正在快速发展的图数据库技术与传统关系数据库之间的本质区别基础上,总结原创的电力图计算平台技术的特点;在此基础上讨论"电网一张图"在建设能源互联网时空信息管理平台数据关联索引图中的核心作用,提出了支持能源互联网建设的"电网一张图"时空信息管理系统的技术架构与特点,最后总结"电网一张图"时空信息管理系统在提高电网安全运行水平、提升客户服务水平、增强清洁能源消纳水平、改善经营绩效水平、以及为综合能源服务和建设能源生态等提供数据服务方面的广阔应用场景。 相似文献
67.
Learning Association Rules and Tracking the Changing Concepts on Webpages: An Effective Pornographic Websites Filtering Approach 下载免费PDF全文
Jyh-Jian Sheu 《电子科技学刊:英文版》2018,16(1):24-36
We applied the decision tree algorithm to learn association rules between webpage’s category (pornographic or normal) and the critical features. Based on these rules, we proposed an efficient method of filtering pornographic webpages with the following major advantages: 1) a weighted window-based technique was proposed to estimate for the condition of concept drift for the keywords found recently in pornographic webpages; 2) checking only contexts of webpages without scanning pictures; 3) an incremental learning mechanism was designed to incrementally update the pornographic keyword database. 相似文献
68.
Araliya Mosleh Kheirollah Sepahvand Humberto Varum José Jara Mehran S. Razzaghi Steffen Marburg 《Structure and Infrastructure Engineering》2018,14(10):1324-1338
This paper focuses on the stochastic response of concrete bridges considering uncertainty in bearing and abutment stiffness. A multi-span simply supported bridge with concrete girders is selected. A 3D-dimensional model is prepared, and nonlinear response history analyses are performed. For the numerical dynamic simulation, the non-sampling stochastic method based on generalized polynomial chaos (gPC) expansion is utilised. The uncertain parameters include the vertical and shear stiffness of bearings and the lateral stiffness of abutments are presented by the truncated gPC expansions. Furthermore, the system response such as base shear, acceleration, velocity and displacement in different columns is presented by gPC expansion with unknown deterministic coefficients. The stochastic Galerkin projection is employed to calculate a set of deterministic equations. A non-intrusive solution, as a set of collocation points, determines the unknown gPC coefficients of the system response and the results are compared with Monte Carlo simulations. The key advantage of spectral discretization is the combination of the mentioned method with the spatial discretization, e.g. finite element model. This study also emphasises the accuracy in results and time efficiency of the proposed non-sampling method for uncertainty quantification of stochastic systems comparing to sampling procedure (e.g. Monte Carlo simulation). 相似文献
69.
《Advanced Powder Technology》2020,31(11):4552-4562
Magnetic nanoferrites (MFe2O4, M = Co, Ni) were successfully synthesised through microwave-hydrothermal route, characterised and used for adsorption of Eriochrome Black T (EBT) and Bromophenol Blue (BRB) dyes from their aqueous solution. The powder XRD patterns confirmed the formation of cubic spinel structure for both the ferrites. Under identical conditions, the adsorption efficiency of CoFe2O4 was found relatively higher than the corresponding NiFe2O4. Further characterisations revealed that CoFe2O4 sample was nearly spherical in size (8–9 nm) with narrow size distribution. The sample showed superparamagnetic behaviour with saturation magnetization (Ms) value (66.4 emu/g). BET surface area calculated for the synthesized cobalt ferrite as 70.9 m2/g. Batch adsorption experiments as a function of initial dye concentration, pH, contact time and adsorbent dose showed the adsorption of dyes depends on pH. Equilibrium adsorption data were well explained by both Langmuir and Freundlich isotherm models. The maximum monolayer adsorption capacities (Qo) were found to be 82.6 and 25.6 mg/g for EBT and BRB dyes, respectively. Kinetics of the adsorption was best described by pseudo-second-order model. Various thermodynamic parameters such as ΔG, ΔH and ΔS derived from adsorption data over the temperature range 20–50 °C, accounted for a favourable, spontaneous, endothermic physisorption process. The materials showed potential for repeated use without significant decrease in adsorption capacity after proper regeneration. 相似文献
70.