全文获取类型
收费全文 | 276313篇 |
免费 | 22728篇 |
国内免费 | 14591篇 |
专业分类
电工技术 | 17080篇 |
技术理论 | 51篇 |
综合类 | 38091篇 |
化学工业 | 28973篇 |
金属工艺 | 13355篇 |
机械仪表 | 15739篇 |
建筑科学 | 41104篇 |
矿业工程 | 16094篇 |
能源动力 | 8195篇 |
轻工业 | 14107篇 |
水利工程 | 15317篇 |
石油天然气 | 11428篇 |
武器工业 | 2665篇 |
无线电 | 17175篇 |
一般工业技术 | 20842篇 |
冶金工业 | 16401篇 |
原子能技术 | 2707篇 |
自动化技术 | 34308篇 |
出版年
2024年 | 395篇 |
2023年 | 2602篇 |
2022年 | 4805篇 |
2021年 | 6193篇 |
2020年 | 6505篇 |
2019年 | 5446篇 |
2018年 | 5165篇 |
2017年 | 6242篇 |
2016年 | 7576篇 |
2015年 | 8499篇 |
2014年 | 15493篇 |
2013年 | 14199篇 |
2012年 | 18539篇 |
2011年 | 19885篇 |
2010年 | 15670篇 |
2009年 | 16342篇 |
2008年 | 15275篇 |
2007年 | 19987篇 |
2006年 | 18903篇 |
2005年 | 16444篇 |
2004年 | 14062篇 |
2003年 | 12707篇 |
2002年 | 10443篇 |
2001年 | 8796篇 |
2000年 | 7395篇 |
1999年 | 6019篇 |
1998年 | 4513篇 |
1997年 | 3952篇 |
1996年 | 3672篇 |
1995年 | 3167篇 |
1994年 | 2834篇 |
1993年 | 2104篇 |
1992年 | 1861篇 |
1991年 | 1386篇 |
1990年 | 1247篇 |
1989年 | 1078篇 |
1988年 | 863篇 |
1987年 | 575篇 |
1986年 | 432篇 |
1985年 | 364篇 |
1984年 | 340篇 |
1983年 | 248篇 |
1982年 | 230篇 |
1981年 | 168篇 |
1980年 | 138篇 |
1979年 | 120篇 |
1978年 | 62篇 |
1977年 | 72篇 |
1976年 | 56篇 |
1975年 | 57篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
《International Journal of Hydrogen Energy》2022,47(7):4328-4345
This paper proposes a parameter adjustable dynamic mass and energy balance simulation model for an industrial alkaline water electrolyzer plant that enables cost and energy efficiency optimization by means of system dimensioning and control. Thus, the simulation model is based on mathematical models and white box coding, and it uses a practicable number of fixed parameters. Zero-dimensional energy and mass balances of each unit operation of a 3 MW, and 16 bar plant process were solved in MATLAB functions connected via a Simulink environment. Verification of the model was accomplished using an analogous industrial plant of the same power and pressure range having the same operational systems design. The electrochemical, mass flow and thermal behavior of the simulation and the industrial plant were compared to ascertain the accuracy of the model and to enable modification and detailed representation of real case scenarios so that the model is suitable for use in future plant optimization studies. The thermal model dynamically predicted the real case with 98.7 % accuracy. Shunt currents were the main contributor to relative low Faraday efficiency of 86 % at nominal load and steady-state operation and heat loss to ambient from stack was only 2.6 % of the total power loss. 相似文献
22.
23.
为解决传统预浸水法存在的浸水时间长、浸水处理范围难以确定等不足,基于土体中水分运移规律,依据可靠度理论、极限状态设计方法及复合 Poisson 过程原理,提出一种消除黄土湿陷性的处理浸水方法——预钻孔浸水法。给出了利用预钻孔浸水法对自重湿陷性黄土地基进行浸水时,水平向及竖直向浸水影响范围的确定模型;在此基础上结合达西定律给出了浸水孔设计参数如孔深、孔间距及浸水孔个数的确定方法。结合铜川某工程,设计进行了现场预钻孔浸水试验,对该方法的合理性进行了验证,并通过现场钻探、现场勘探、室内湿陷性试验等方法对该方法的处理效果进行了评价。该浸水方法具有浸水时间短、浸水影响范围可根据浸水孔布设进行控制等优点,且浸水处理效果良好,完全符合施工要求。 相似文献
24.
以禹州市梁北矿为研究区,利用2018年11月—2020年6月间35景5 m×20 m分辨率Sentinel-1A数据,采用InSAR技术,利用SBAS(短基线集InSAR)雷达干涉测量方法对梁北矿进行地面沉降信息提取解译,并通过实地调查成果认为,采用InSAR技术适合在矿区开展地表变形监测。 相似文献
25.
26.
27.
This article proposes an active balancer, which features bidirectional charge shuttling and adaptive equalization current control, to fast counterbalance the state of charge (SOC) of cells in a lithium-ion battery (LIB) string. The power circuit consists of certain bidirectional buck-boost converters to transfer energy among the different cells back and forth. Owing to the characterization of the open-circuit voltage (OCV) vs SOC in LIB being relatively smooth near the SOC middle range, the SOC-inspected balance strategy can achieve more precise and efficient equilibrium than the voltage-based control. Accordingly, a compensated OCV-based SOC estimation is put forward to take into account the discrepancy of SOC estimation. Besides, the varied-duty-cycle (VDC) and curve-fitting modulation (CFM) methods are devised herein to tackle the problems of slow equalization rate and low balance efficacy, which arise from the diminution in balancing current as the SOC difference between the cells decreases in the later duration of equalization especially. The proposed strategies have taken the battery nonlinear characteristic and circuit parameter nonideality into account and can adaptively modulate the duty cycle with the SOC difference to keep balancing current constant throughout the balancing cycle. Simulated and experimental results are given to demonstrate the feasibility and effectiveness of the same prototype constructed. Compared with the fixed duty cycle and the VDC methods, the proposed CFM has the best balancing efficiency of 81.4%, and the balance time is shortened by 27.1% and 18.6%, respectively. 相似文献
28.
29.
中国考古出土的蚕业实物及蚕的艺术形象比较丰富,蚕的艺术形象如蚕纹、陶蚕蛹、牙雕蚕、玉石蚕、铜蚕、金蚕等,可统称为"蚕的模拟形态"。对蚕的模拟形态的功用,已有的诸多解释都有待完善。研究表明,蚕的模拟形态或艺术形象表达的功用或为饰品,或为装饰图案,或有待进一步考究。但无论哪种功用,用"蚕"这一形象都蕴含了特有的用意。通过对中国古代生命观的考察,文章认为蚕的艺术形象折射出相应的中国古代哲学生命观,即中国古人追求的死而复生、生生不息、羽化成仙、长乐无极等观念。 相似文献
30.
Referring to the total surface existing in wheat dough, gluten–starch interfaces are a major component. However, their impact on dough rheology is largely unclear. Common viewpoints, based on starch surface modifications or reconstitution experiments, failed to show unambiguous relations of interface characteristics and dough rheology. Observing hybrid artificial dough systems with defined particle surface functionalization gives a new perspective. Since surface functionalization standardizes particle–polymer interfaces, the impact on rheology becomes clearly transferable and thus, contributes to a better understanding of gluten–starch interfaces. Based on this perspective, the effect of particle/starch surface functionality is discussed in relation to the rheological properties of natural wheat dough and modified gluten–starch systems. A competitive relation of starch and gluten for intermolecular interactions with the network-forming polymer becomes apparent during network development by adsorption phenomena. This gluten–starch adhesiveness delays the beginning of non-linearity under large deformations, thus contributing to a high deformability of dough. Consequently, starch surface functionality affects the mechanical properties, starting from network formation and ending with the thermal fixation of structure. 相似文献