全文获取类型
收费全文 | 229013篇 |
免费 | 17955篇 |
国内免费 | 9154篇 |
专业分类
电工技术 | 12489篇 |
技术理论 | 24篇 |
综合类 | 14175篇 |
化学工业 | 38888篇 |
金属工艺 | 13168篇 |
机械仪表 | 14544篇 |
建筑科学 | 17587篇 |
矿业工程 | 7520篇 |
能源动力 | 6429篇 |
轻工业 | 13531篇 |
水利工程 | 3606篇 |
石油天然气 | 16720篇 |
武器工业 | 1652篇 |
无线电 | 25167篇 |
一般工业技术 | 27400篇 |
冶金工业 | 12818篇 |
原子能技术 | 2262篇 |
自动化技术 | 28142篇 |
出版年
2024年 | 995篇 |
2023年 | 3814篇 |
2022年 | 6500篇 |
2021年 | 9114篇 |
2020年 | 7104篇 |
2019年 | 6031篇 |
2018年 | 6746篇 |
2017年 | 7553篇 |
2016年 | 6773篇 |
2015年 | 8884篇 |
2014年 | 11268篇 |
2013年 | 13299篇 |
2012年 | 14242篇 |
2011年 | 15489篇 |
2010年 | 13453篇 |
2009年 | 12708篇 |
2008年 | 12395篇 |
2007年 | 11885篇 |
2006年 | 12374篇 |
2005年 | 10777篇 |
2004年 | 7278篇 |
2003年 | 6253篇 |
2002年 | 5472篇 |
2001年 | 4894篇 |
2000年 | 5445篇 |
1999年 | 6454篇 |
1998年 | 5447篇 |
1997年 | 4463篇 |
1996年 | 4197篇 |
1995年 | 3503篇 |
1994年 | 2819篇 |
1993年 | 1967篇 |
1992年 | 1537篇 |
1991年 | 1228篇 |
1990年 | 936篇 |
1989年 | 742篇 |
1988年 | 537篇 |
1987年 | 337篇 |
1986年 | 278篇 |
1985年 | 197篇 |
1984年 | 139篇 |
1983年 | 114篇 |
1982年 | 125篇 |
1981年 | 98篇 |
1980年 | 70篇 |
1979年 | 36篇 |
1978年 | 26篇 |
1977年 | 20篇 |
1976年 | 35篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
62.
分析了建立高可用性DHCP服务的迫切需求,根据DHCP服务体系结构,提出了DHCP服务的设计方法,并进行了周密的系统设计和系统部署,总结出了大型局域网部署DHCP服务的优化策略。 相似文献
63.
64.
AbstractBuilding thermal inertia and operation control strategies have impacted on the thermal performance of a radiant floor heating system. This study conducts a two-dimensional numerical analysis of an intermittently operated radiant floor heating system using the Re-Normalization Group model with Discrete Ordinates Radiation model. A detailed numerical simulation setups and various analyses are provided, including grid independency analysis, initial condition, time step sizes and external boundary conditions. Three different weekend day intermittent operation strategies are investigated. The results showed that Case 3 designed with pre-heating of 20?h has better performance compared to Case 1 designed with pre-heating of 8?h and Case 2 designed with pre-heating of 14?h. The average indoor air temperature differences of approximate 2.1, 1.6 and 1.2 K are observed for Case 1, Case 2 and Case 3, respectively, when comparing two-time slot at 8:00am on Friday morning and Monday morning. This significantly highlights the effect of thermal inertia and the potential of energy saving due to the utilization of intermittent operation. Therefore, the current study presents numerical simulation potential in evaluating the radiant floor heating effects on indoor thermal environment, taking into account building thermal inertia and transient external climatic conditions. 相似文献
65.
66.
67.
Han Yan Gu Yi Chen Lei Li Bing Liu Xiang Ming Chen 《International Journal of Applied Ceramic Technology》2020,17(2):790-796
SrLa[Ga1−x(R0.5Ti0.5)x]O4 (R = Mg, Zn) ceramics were prepared by a standard solid state sintering method. The single-phase ceramics with K2NiF4-type layered perovskite structure and I4/mmm space group were obtained, indicating that SrLa(R0.5Ti0.5) and SrLaGaO4 can form the unlimited solid solutions. With increasing x for R = Mg and Zn, εr increases monotonously, the Qf value first increases and then decreases, while τf increases from a negative to a positive value. The optimized microwave dielectric properties were obtained as following: εr = 23.3, Qf = 89 400 GHz, τf = −0.8 ppm/°C for SrLa[Ga0.6(Mg0.5Ti0.5)0.4]O4 and εr = 23.3, Qf = 76 200 GHz, τf = 0.2 ppm/°C for SrLa[Ga0.7(Zn0.5Ti0.5)0.3]O4, indicating that the present solid solution ceramics are the promising candidates as microwave resonator materials for the telecommunication applications. 相似文献
68.
Yao Dajie Liu Xiaofei Wu Jian 《International Journal of Control, Automation and Systems》2020,18(9):2251-2258
International Journal of Control, Automation and Systems - In this paper, the tracking problem for a class of uncertain nonlinearly parameterized systems with input delay based the adaptive... 相似文献
69.
To minimize the mass and increase the bearing failure load of composite doublelap bolted joints, a three-step optimization strategy including feasible region reduction,
optimization model decoupling and optimization was presented. In feasible region
reduction, the dimensions of the feasible design region were reduced by selecting dominant
design variables from numerous multilevel parameters by sensitivity analyses, and the
feasible regions of variables were reduced by influence mechanism analyses. In model
decoupling, the optimization model with a large number of variables was divided into
various sub-models with fewer variables by variance analysis. In the third step, the
optimization sub-models were solved one by one using a genetic algorithm, and the
modified characteristic curve method was adopted as the failure prediction method. Based
on the proposed optimization method, optimization of a double-lap single-bolt joint was
performed using the ANSYS® code. The results show that the bearing failure load increased
by 13.5% and that the mass decreased by 8.7% compared with those of the initial design of
the joint, which validated the effectiveness of the three-step optimization strategy. 相似文献