全文获取类型
收费全文 | 186173篇 |
免费 | 15729篇 |
国内免费 | 11349篇 |
专业分类
电工技术 | 29574篇 |
技术理论 | 8篇 |
综合类 | 17678篇 |
化学工业 | 11212篇 |
金属工艺 | 6920篇 |
机械仪表 | 16122篇 |
建筑科学 | 16482篇 |
矿业工程 | 7211篇 |
能源动力 | 4902篇 |
轻工业 | 5988篇 |
水利工程 | 5673篇 |
石油天然气 | 5798篇 |
武器工业 | 2682篇 |
无线电 | 13518篇 |
一般工业技术 | 10248篇 |
冶金工业 | 8320篇 |
原子能技术 | 1315篇 |
自动化技术 | 49600篇 |
出版年
2024年 | 260篇 |
2023年 | 1999篇 |
2022年 | 3243篇 |
2021年 | 4129篇 |
2020年 | 4951篇 |
2019年 | 3847篇 |
2018年 | 3308篇 |
2017年 | 5064篇 |
2016年 | 5522篇 |
2015年 | 6243篇 |
2014年 | 12316篇 |
2013年 | 10695篇 |
2012年 | 13658篇 |
2011年 | 14826篇 |
2010年 | 11198篇 |
2009年 | 11488篇 |
2008年 | 11279篇 |
2007年 | 13945篇 |
2006年 | 12446篇 |
2005年 | 10862篇 |
2004年 | 9022篇 |
2003年 | 7984篇 |
2002年 | 6398篇 |
2001年 | 5257篇 |
2000年 | 4406篇 |
1999年 | 3562篇 |
1998年 | 2751篇 |
1997年 | 2370篇 |
1996年 | 1890篇 |
1995年 | 1645篇 |
1994年 | 1366篇 |
1993年 | 995篇 |
1992年 | 801篇 |
1991年 | 607篇 |
1990年 | 478篇 |
1989年 | 442篇 |
1988年 | 332篇 |
1987年 | 192篇 |
1986年 | 152篇 |
1985年 | 165篇 |
1984年 | 222篇 |
1983年 | 200篇 |
1982年 | 195篇 |
1981年 | 101篇 |
1980年 | 74篇 |
1979年 | 78篇 |
1978年 | 58篇 |
1977年 | 57篇 |
1959年 | 18篇 |
1955年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(85):36216-36231
The fuel cell/battery durability and hybrid system stability are major considerations for the power management of fuel cell hybrid electric bus (FCHEB) operating on complicated driving conditions. In this paper, a real time nonlinear adaptive control (NAC) with stability analyze is formulated for power management of FCHEB. Firstly, the mathematical model of hybrid power system is analyzed, which is established for control-oriented design. Furthermore, the NAC-based strategy with quadratic Lyapunov function is set up to guarantee the stability of closed-loop power system, and the power split between fuel cell and battery is controlled with the durability consideration. Finally, two real-time power management strategies, state machine control (SMC) and fuzzy logic control (FLC), are implemented to evaluate the performance of NAC-based strategy, and the simulation results suggest that the guaranteed stability of NAC-based strategy can efficiently prolong fuel cell/battery lifespan and provide better fuel consumption economy for FCHEB. 相似文献
2.
高面板坝的变形对面板的安全运行有着特别重要的影响,国内外已建的高面板坝工程中,因坝体变形大导致防渗面板挤压破损,坝体渗漏量大的实例较多,不得不降低水库水位进行修复处理,造成较大的经济损失乃至给大坝的长期运行留下安全隐患。通过发生挤压破损的实例分析,发现变形控制缺乏系统性是发生面板挤压破损的主要因素,为预防面板破损,系统提出了“控制坝体总变形,转化有害变形,适应纵向变形”的坝体变形控制方法,并在使用软硬岩混合料筑坝的董箐面板堆石坝中得到的应用,取得了良好效果,该工程运行至今达十余年,未见面板有挤压破损迹象,该方法对建设200 m以上乃至300 m级超高面板坝具有重要借鉴意义。 相似文献
3.
Muhammad Yazid Samatra Nor Qhairul Izzreen Mohd Noor Umi Hartina Mohamad Razali Jamilah Bakar Sharifudin Md. Shaarani 《Comprehensive Reviews in Food Science and Food Safety》2022,21(4):3153-3176
Gelatin is one of the most important multifunctional biopolymers and is widely used as an essential ingredient in food, pharmaceutical, and cosmetics. Porcine gelatin is regarded as the leading source of gelatin globally then followed by bovine gelatin. Porcine sources are favored over other sources since they are less expensive. However, porcine gelatin is religiously prohibited to be consumed by Muslims and the Jewish community. It is predicted that the global demand for gelatin will increase significantly in the future. Therefore, a sustainable source of gelatin with efficient production and free of disease transmission must be developed. The highest quality of Bovidae-based gelatin (BG) was acquired through alkaline pretreatment, which displayed excellent physicochemical and rheological properties. The utilization of mammalian- and plant-based enzyme significantly increased the gelatin yield. The emulsifying and foaming properties of BG also showed good stability when incorporated into food and pharmaceutical products. Manipulation of extraction conditions has enabled the development of custom-made gelatin with desired properties. This review highlighted the various modifications of extraction and processing methods to improve the physicochemical and functional properties of Bovidae-based gelatin. An in-depth analysis of the crucial stage of collagen breakdown is also discussed, which involved acid, alkaline, and enzyme pretreatment, respectively. In addition, the unique characteristics and primary qualities of BG including protein content, amphoteric property, gel strength, emulsifying and viscosity properties, and foaming ability were presented. Finally, the applications and prospects of BG as the preferred gelatin source globally were outlined. 相似文献
4.
《Ceramics International》2022,48(1):754-759
Thermal control coatings (TCCs) are an essential part of the thermal control systems in the spacecraft. Solar absorptance and emittance are the key performance parameters of TCCs. To develop an ultra-low solar absorption and stable inorganic TCCs for surface radiator, different TCCs were prepared by co-sintering ZnO and SiO2 nanoparticles to form Zn2SiO4/SiO2 pigment in this work, and the optical properties and radiation stability were systematically studied. It is found that the coating based on composite pigment has high reflectivity in the ultraviolet band and excellent optical performance possessing the low solar absorption of 0.06. In addition, the Zn2SiO4/SiO2 coating demonstrates the highest proton and electron radiation stability because that SiO2 between Zn2SiO4 particles acts as the relaxation center of the defects caused by radiation. 相似文献
5.
6.
随着社会的进步和发展,计算机网络通信技术已被应用到实际生活、生产的各个方面,对人们的生活、生产等产生了深刻的影响。为此,文章就计算机通信及网络远程控制技术在实际生活中的应用问题进行了探究,旨在借助先进科技促进社会实现更优质发展。 相似文献
7.
8.
《International Journal of Hydrogen Energy》2022,47(58):24569-24583
Hydrogen generation from renewable energy resources is considered as a suitable solution to solve the problems related to the energy sector and the reduction of greenhouse gases. The aim of this study is to provide an integrated framework for identifying suitable areas for the construction of wind farms to produce hydrogen. For this purpose, a combined method of Geographic Information System (GIS) and multi-criteria decision making (MCDM) has been used to locate the power plant in Yazd province. The GIS method in the present study consisted of two parts: constraints and criteria. The constraint section included areas that were unsuitable for the construction of wind farms to produce power and hydrogen. In the present study, various aspects such as physical, economic and environmental had been considered as constraints. In the criteria section, eight different criteria from technical aspects (including average wind speed, hydrogen production potential, land slope) and economic aspects (including distance to electricity grid, distance to urban areas, distance to road, distance to railway and distance to centers of High hydrogen consumption) had been investigated. The MCDM tool had been used to weigh the criteria and identify suitable areas. Analytic Hierarchy Process (AHP) technique was used for weighting the criteria. The results of AHP weighting method showed that economic criteria had the highest importance with a value of 0.681. The most significant sub-criterion was the distance to urban areas and the least significant sub-criterion was the distance to power transmission lines. The results of GIS-MCDM analysis had shown that the most proper areas were in the southern and central sectors of Yazd province. In addition, the feasibility of hydrogen production from wind energy had shown that this province had the capacity to generate hydrogen at the rate of 53.6–128.6 tons per year. 相似文献
9.
10.