全文获取类型
收费全文 | 226096篇 |
免费 | 22670篇 |
国内免费 | 14650篇 |
专业分类
电工技术 | 17717篇 |
技术理论 | 7篇 |
综合类 | 20549篇 |
化学工业 | 33288篇 |
金属工艺 | 14264篇 |
机械仪表 | 15375篇 |
建筑科学 | 17531篇 |
矿业工程 | 8222篇 |
能源动力 | 6383篇 |
轻工业 | 20052篇 |
水利工程 | 5572篇 |
石油天然气 | 10962篇 |
武器工业 | 2409篇 |
无线电 | 24415篇 |
一般工业技术 | 23074篇 |
冶金工业 | 9282篇 |
原子能技术 | 3149篇 |
自动化技术 | 31165篇 |
出版年
2024年 | 829篇 |
2023年 | 3640篇 |
2022年 | 7493篇 |
2021年 | 10308篇 |
2020年 | 7537篇 |
2019年 | 5705篇 |
2018年 | 6116篇 |
2017年 | 7087篇 |
2016年 | 6204篇 |
2015年 | 9588篇 |
2014年 | 11666篇 |
2013年 | 14134篇 |
2012年 | 16621篇 |
2011年 | 17631篇 |
2010年 | 16064篇 |
2009年 | 15637篇 |
2008年 | 15507篇 |
2007年 | 15023篇 |
2006年 | 13967篇 |
2005年 | 11760篇 |
2004年 | 8256篇 |
2003年 | 6394篇 |
2002年 | 5921篇 |
2001年 | 5403篇 |
2000年 | 5053篇 |
1999年 | 3853篇 |
1998年 | 2903篇 |
1997年 | 2422篇 |
1996年 | 2189篇 |
1995年 | 1913篇 |
1994年 | 1521篇 |
1993年 | 1119篇 |
1992年 | 914篇 |
1991年 | 713篇 |
1990年 | 536篇 |
1989年 | 484篇 |
1988年 | 377篇 |
1987年 | 246篇 |
1986年 | 167篇 |
1985年 | 98篇 |
1984年 | 63篇 |
1983年 | 56篇 |
1982年 | 66篇 |
1981年 | 61篇 |
1980年 | 65篇 |
1979年 | 27篇 |
1978年 | 3篇 |
1965年 | 4篇 |
1959年 | 35篇 |
1951年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
61.
62.
Rectangular section control technology(RSCT)was introduced to achieve high-precision profile control during silicon steel rolling.The RSCT principle and method were designed,and the whole RSCT control strategy was developed.Specifically,RSCT included roll contour design,rolling technology optimization,and control strategy development,aiming at both hot strip mills(HSMs)and cold strip mills(CSMs).Firstly,through the high-performance variable crown(HVC)work roll optimization design in the upper-stream stands and the limited shifting technology for schedule-free rolling in the downstream stands of HSMs,a hot strip with a stable crown and limited wedge,local spot,and single wave was obtained,which was suitable for cold rolling.Secondly,an approximately rectangular section was obtained by edge varying contact(EVC)work roll contour design,edge-drop setting control,and closed loop control in the upper-stream stands of CSMs.Moreover,complex-mode flatness control was realized by coordinating multiple shape-control methods in the downstream stands of CSMs.In addition,the RSCT approach was applied in several silicon-steel production plants,where an outstanding performance and remarkable economic benefits were observed. 相似文献
63.
Sergey Bombin Mitchell LeFebvre Jennifer Sherwood Yaolin Xu Yuping Bao Katrina M. Ramonell 《International journal of molecular sciences》2015,16(10):24174-24193
Increasing use of iron oxide nanoparticles in medicine and environmental remediation has led to concerns regarding exposure of these nanoparticles to the public. However, limited studies are available to evaluate their effects on the environment, in particular on plants and food crops. Here, we investigated the effects of positive (PC) and negative (NC) charged iron oxide (Fe2O3) nanoparticles (IONPs) on the physiology and reproductive capacity of Arabidopsis thaliana at concentrations of 3 and 25 mg/L. The 3 mg/L treated plants did not show evident effects on seeding and root length. However, the 25 mg/L treatment resulted in reduced seedling (positive-20% and negative-3.6%) and root (positive-48% and negative-negligible) length. Interestingly, treatment with polyethylenimine (PEI; IONP-PC coating) also resulted in reduced root length (39%) but no change was observed with polyacrylic acid (PAA; IONP-NC coating) treatment alone. However, treatment with IONPs at 3 mg/L did lead to an almost 5% increase in aborted pollen, a 2%–6% reduction in pollen viability and up to an 11% reduction in seed yield depending on the number of treatments. Interestingly, the treated plants did not show any observable phenotypic changes in overall size or general plant structure, indicating that environmental nanoparticle contamination could go dangerously unnoticed. 相似文献
64.
Lü Qing Xu Bin Yu Yang Zhan Wei Zhao Yu Zheng Jun Ji Jian 《Bulletin of Engineering Geology and the Environment》2021,80(8):6513-6525
Bulletin of Engineering Geology and the Environment - Many uncertainties exist in pile-stabilized slopes which make their design substantially complicated. In this paper, a first-order reliability... 相似文献
65.
66.
王虔虔在上任中建材(合肥)粉体科技装备有限公司(简称粉体公司)总经理之前,和分管部门的所有同事坐在同一间大办公室内。之所以和大家在同一个空间内工作,王虔虔是想更进一步拉近彼此之间的距离,以身作则潜移默化,传承公司文化,建立相互信任的团队。2012年,粉体公司决定向"提供系统解决方案的综合服务商"转变。 相似文献
67.
Lu Xu Baijun Liu Mingyao Zhang Yang Bai Jinming Zhang Jiayin Song 《Polymer Engineering and Science》2020,60(6):1194-1201
A series of methacrylate-acrylonitrile-butadiene-styrene (MABS) resins was prepared using bulk polymerization. The polarity of the continuous phase and the compatibility of two phases were changed by adjusting the methyl methacrylate (MMA) content, choosing values that were close to styrene-butadiene rubber solubility value. The possibility of controlling the microstructure of the MABS resin by changing the polarity of the components and the compatibility of two phases was assessed. The dynamic mechanical analysis shows that the compatibility of two phases varies with the MMA content. The morphological analysis shows that increasing MMA contents results in a gradual decrease in the sub-inclusion structure with a network skeleton of rubber particles, and that all the particles become solid rubber when the MMA content reaches 75%. The sub-inclusion structure reappears but does not have a network skeleton when the MMA content is 90%. The impact strength and morphological analysis indicate that the solid rubber particles and the sub-inclusion structure with a network skeleton provide excellent toughness, while the sub-inclusion structure without a network skeleton does not. In contrast, the transmittance of the ABS resin first increased and then decreased with increasing MMA content. 相似文献
68.
ABSTRACT This study investigates the effects of strain, strain rates, and forming directions (RD-rolling direction, TD-transverse direction, and ND-normal direction) on adiabatic shear, via dynamic impact compression tests using the Split Hopkinson Pressure Bar (SHPB) apparatus. A modified Johnson-Cook (J-C) constitutive model is proposed, which used to analyse the influence of the constitutive parameters on the sensitivity of adiabatic shear, employing a finite element software. The different sensitivities of adiabatic shear under different directions are explained by combining microscopic analysis and results from mechanical responses. The results show that the sensitivity of adiabatic shear can be related to the time of stress collapse in the following trend: ND?>?TD?>?RD; the sensitivities of these constitutive parameters on adiabatic shear are calculated and compared. 相似文献
69.
孙振 《水电自动化与大坝监测》2015,(2):75-79
本文首先分析国内典型的AVC的一般配置、控制策略和控制原理,针对巨型水电站孤岛试验期间的AVC控制的复杂工况进行阐述,对出现的AVC电压波动的情况进行分析,并对采用的解决方案进行介绍,为今后类似电站的孤岛运行期间的AVC电压控制提供一些参考建议。 相似文献
70.
陕南山地烟田不同植烟年限土壤养分的变化 总被引:1,自引:0,他引:1
为给陕南山地烟草生产布局及有针对性的施肥措施提供依据,分析了陕南山地烟田不同植烟年限(0~15年)与土壤养分含量的关系。结果表明:随着植烟年限延长,有机质线性下降,全氮和速效钾显著上升,有效磷先上升后下降;氯、有效铁、有效锰、有效硼和有效铜无显著变化或变化很小,有效锌则在第1年急剧下降,之后保持稳定,10年后再次显著下降。认为陕南山地烟区烟叶生产中应适当增加有机肥的施用而合理控制氮肥、磷肥和钾肥的施用,并要注意锌肥的补充。 相似文献