全文获取类型
收费全文 | 22216篇 |
免费 | 1429篇 |
国内免费 | 1075篇 |
专业分类
电工技术 | 1414篇 |
技术理论 | 4篇 |
综合类 | 2231篇 |
化学工业 | 1276篇 |
金属工艺 | 1020篇 |
机械仪表 | 2492篇 |
建筑科学 | 1579篇 |
矿业工程 | 1173篇 |
能源动力 | 916篇 |
轻工业 | 673篇 |
水利工程 | 785篇 |
石油天然气 | 801篇 |
武器工业 | 412篇 |
无线电 | 1440篇 |
一般工业技术 | 1275篇 |
冶金工业 | 800篇 |
原子能技术 | 353篇 |
自动化技术 | 6076篇 |
出版年
2024年 | 34篇 |
2023年 | 134篇 |
2022年 | 341篇 |
2021年 | 428篇 |
2020年 | 455篇 |
2019年 | 351篇 |
2018年 | 324篇 |
2017年 | 429篇 |
2016年 | 524篇 |
2015年 | 604篇 |
2014年 | 1133篇 |
2013年 | 1155篇 |
2012年 | 1423篇 |
2011年 | 1686篇 |
2010年 | 1267篇 |
2009年 | 1243篇 |
2008年 | 1166篇 |
2007年 | 1574篇 |
2006年 | 1572篇 |
2005年 | 1459篇 |
2004年 | 1159篇 |
2003年 | 1071篇 |
2002年 | 923篇 |
2001年 | 671篇 |
2000年 | 565篇 |
1999年 | 577篇 |
1998年 | 428篇 |
1997年 | 360篇 |
1996年 | 310篇 |
1995年 | 289篇 |
1994年 | 210篇 |
1993年 | 162篇 |
1992年 | 128篇 |
1991年 | 93篇 |
1990年 | 95篇 |
1989年 | 72篇 |
1988年 | 71篇 |
1987年 | 33篇 |
1986年 | 23篇 |
1985年 | 25篇 |
1984年 | 30篇 |
1983年 | 14篇 |
1982年 | 21篇 |
1981年 | 15篇 |
1980年 | 9篇 |
1979年 | 13篇 |
1978年 | 15篇 |
1977年 | 9篇 |
1975年 | 4篇 |
1966年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(93):39639-39653
Metals that are exposed to high pressure hydrogen gas may undergo detrimental failure by embrittlement. Understanding the mechanisms and driving forces of hydrogen absorption on the surface of metals is crucial for avoiding hydrogen embrittlement. In this study, the effect of stress-enhanced gaseous hydrogen uptake in bulk metals is investigated in detail. For that purpose, a generalized form of Sievert's law is derived from thermodynamic potentials considering the effect of microstructural trapping sites and multiaxial stresses. This new equation is parametrized and verified using experimental data for carbon steels, which were charged under gaseous hydrogen atmosphere at pressures up to 1000 bar. The role of microstructural trapping sites on the parameter identification is critically discussed. Finally, the parametrized equation is applied to calculate the stress-enhanced hydrogen solubility of thin-walled pipelines and thick-walled pressure vessels during service. 相似文献
2.
针对煤矿井下高瓦斯软煤顺层长钻孔排渣困难、成孔率低、施工困难等问题,通过数值模拟实验研究了井下深部软煤体变形破坏特征,分析了顺层长钻孔孔周松软煤体变形特征及应力变化,以揭示顺层长钻孔孔周松软煤体变形产渣规律。研究表明:深部高瓦斯软煤顺层钻孔孔周煤体的应力平衡临界条件破坏后将发生大体积突然垮落;钻孔水平最大变形位移为1.22mm,垂直方向最大变形位移为10.7mm;径向孔周煤体垂向变形呈现逐渐减小趋势,且垂向变形明显大于钻孔水平变形。在水平方向上,钻孔孔周煤体应力分布呈现先增大再逐渐减小的变化规律,径向距离对水平应力分布的影响逐渐减小;随着径向距离的增加,钻孔孔周煤体应力分布逐渐降低,钻孔孔壁处煤体的应力出现最大值,且垂直方向处应力值最大。 相似文献
3.
4.
This paper investigates a renewable energy resource’s application to the Load–Frequency Control of interconnected power system. The Proportional-Integral (PI) controllers are replaced with Proportional-Integral Plus (PI+) controllers in a two area interconnected thermal power system without/with the fast acting energy storage devices and are designed based on Control Performance Standards (CPS) using conventional/Beta Wavelet Neural Network (BWNN) approaches. The energy storing devices Hydrogen generative Aqua Electroliser (HAE) with Fuel cell and Redox Flow Battery (RFB) are incorporated to the two area interconnected thermal power system to efficiently damp out the electromechanical oscillations in the power system because of their inherent efficient storage capacity in addition to the kinetic energy of the generator rotor, which can share the sudden changes in power requirements. The system was simulated and the frequency deviations in area 1 and area 2 and tie-line power deviations for 5% step- load disturbance in area 1 are obtained. The comparison of frequency deviations and tie-line power deviations of the two area interconnected thermal power system with HAE and RFB designed with BWNN controller reveals that the PI+ controller designed using BWNN approach is found to be superior than that of output response obtained using PI+ controller. Moreover the BWNN based PI+ controller exhibits a better transient and steady state response for the interconnected power system with Hydrogen generative Aqua Electroliser (AE) unit than that of the system with Redox Flow Battery (RFB) unit. 相似文献
5.
通过分析A公司在研发项目范围管理中所存在问题,提出研发项目范围管理的方法及其在C产品的应用实例,通过运用研发项目范围管理的工具和方法,改善产品开发流程,从而缩短新产品开发周期,提高响应市场的速度,并提高企业研发项目的管理能力。 相似文献
6.
7.
《Mechatronics》2021
Producing a stable and agile bionic eye for visual image acquisition in robotics is a challenging task. In this paper, we design a bionic eye with mirror-symmetric distribution and cross-connection of flexible ropes. This mechanism is based on oculomotor law and the physiological structure of the extraocular muscles (EOMs). Specifically, the basic structural parameters are determined by Listing’s law, and the unique connection of the flexible ropes can realize the functions of the recti and oblique muscles. Furthermore, to mimic the trochlea structure, a pulley mechanism is constructed to permit the free movement of the flexible ropes. Through simulation and physical experiments, it is demonstrated that the bionic eye mechanism can move with agility under the structural parameters. The experimental results indicate that the proposed bionic eye mechanism has a superior motion accuracy of 2.798 mm, which is 6.7% of the maximum motion distance, and the repeatable accuracy of the mechanism can up to 0.210 mm. 相似文献
8.
随着我国环境保护法规《大气污染防治法》的修订和《涂料征收消费税通知》的公布,探讨了其对船舶涂料企业的冲击及其应对措施。 相似文献
9.
刘家山排土场为民采排弃形成,已经出现大规模滑坡。为了保证上下游生产生活设施的安全,依据现场实际情况,结合现场调查,提出了削坡处理的方案。经过治理后,刘家山排土场平稳地渡过了雨季,目前处于稳定状态,达到了治理目的。 相似文献
10.
Adaptive decision making requires that contingencies between decision options and their relative assets be assessed accurately and quickly. The present research addresses the challenging notion that contingencies may be more visible from small than from large samples of observations. An algorithmic account for such a seemingly paradoxical effect is offered within a satisficing-choice framework. Accordingly, a choice is only made when the sample contingency describing the relative evaluation of the 2 options exceeds a critical threshold. Small samples, because of the high dispersion of their sampling distribution, facilitate above-threshold contingencies. Across a broad range of parameters, the resulting small-sample advantage in terms of hits is stronger than their disadvantage in false alarms. Computer simulations and experiments support the model predictions. The relative advantage of small samples is most apparent when information loss is low, when the threshold is high relative to the ecological contingency, and when the sampling process is self-truncated. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献