全文获取类型
收费全文 | 375032篇 |
免费 | 41283篇 |
国内免费 | 27857篇 |
专业分类
电工技术 | 31656篇 |
技术理论 | 7篇 |
综合类 | 35702篇 |
化学工业 | 50595篇 |
金属工艺 | 24851篇 |
机械仪表 | 26513篇 |
建筑科学 | 29891篇 |
矿业工程 | 12723篇 |
能源动力 | 10168篇 |
轻工业 | 38017篇 |
水利工程 | 11642篇 |
石油天然气 | 14825篇 |
武器工业 | 4565篇 |
无线电 | 40616篇 |
一般工业技术 | 35937篇 |
冶金工业 | 14621篇 |
原子能技术 | 5948篇 |
自动化技术 | 55895篇 |
出版年
2024年 | 1901篇 |
2023年 | 5944篇 |
2022年 | 13337篇 |
2021年 | 17457篇 |
2020年 | 12691篇 |
2019年 | 9372篇 |
2018年 | 9799篇 |
2017年 | 11204篇 |
2016年 | 10149篇 |
2015年 | 15547篇 |
2014年 | 19614篇 |
2013年 | 23610篇 |
2012年 | 28641篇 |
2011年 | 30141篇 |
2010年 | 28317篇 |
2009年 | 27331篇 |
2008年 | 27780篇 |
2007年 | 27167篇 |
2006年 | 24735篇 |
2005年 | 20438篇 |
2004年 | 15178篇 |
2003年 | 11337篇 |
2002年 | 11106篇 |
2001年 | 10073篇 |
2000年 | 8228篇 |
1999年 | 5089篇 |
1998年 | 3163篇 |
1997年 | 2650篇 |
1996年 | 2352篇 |
1995年 | 2039篇 |
1994年 | 1630篇 |
1993年 | 1241篇 |
1992年 | 1034篇 |
1991年 | 810篇 |
1990年 | 616篇 |
1989年 | 580篇 |
1988年 | 449篇 |
1987年 | 313篇 |
1986年 | 227篇 |
1985年 | 146篇 |
1984年 | 103篇 |
1983年 | 91篇 |
1982年 | 88篇 |
1981年 | 80篇 |
1980年 | 121篇 |
1979年 | 63篇 |
1978年 | 11篇 |
1965年 | 18篇 |
1959年 | 54篇 |
1951年 | 49篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
For the purpose of developing biodegradable magnesium alloys with suitable properties for biomedical applications, Mg–Zn–Ca–Cu metallic glasses were prepared by copper mold injection methods. In the present work, the effect of Cu doping on mechanical properties, corrosion behavior, and glass-forming ability of Mg66Zn30Ca4 alloy was studied. The experimental findings demonstrated that the incorporation of Cu decreases the corrosion resistance of alloys, but increases the microhardness and degradation rate slightly. However, the addition of a trace amount of Cu can make the samples have antibacterial properties. Therefore, Mg–Zn–Ca–Cu has great advantages in clinical implantation and is the potential implant material. 相似文献
32.
针对伊拉克米桑油田盐膏层巨厚、钻井液密度窗口窄、存在高压盐水层,储层段漏塌同层导致复杂时效高等问题,通过对比分析国内外盐膏层和窄压力窗口地层钻井技术,总结了米桑油田钻井面临的主要技术难点,从井身结构优化、钻井提速和复杂预防等方面入手,研究形成了适合米桑油田的钻井关键技术,并进行了现场试验应用,取得了显著的效果.伊拉克米桑油田钻井关键技术对该地区钻井技术方案设计和钻井提速提效具有较强的借鉴和指导作用. 相似文献
33.
Bing Huang Meng Wang Guodong Xu Lin Hu Lin Chen Yijie Gu 《Ceramics International》2021,47(6):7700-7710
In this study, La was doped into the lithium layer of Li-rich cathode material and formed a layered-spinel hetero-structure. The morphology, crystal structure, element valence and kinetics of lithium ion migration were studied by field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The La doped lithium-rich cathode material exhibited similar initial discharge capacity of 262.8 mAh g?1 at 0.1 C compared with the undoped material, but the discharge capacity retention rate can be obviously improved to 90% after 50 cycles at 1.0 C. Besides that, much better rate capability and Li+ diffusion coefficient were observed. The results revealed that La doping not only stabilized the material structure and reduced the Li/Ni mixing degree, but also induced the generation of spinel phase to provide three-dimensional diffusion channels for lithium ion migration. Moreover, the porous structure of the doped samples also contributed to the remarkable excellent electrochemical performance. All of these factors combined to significantly improve the electrochemical performance of the material. 相似文献
34.
为研究铁塔公司发布的最新《低成本铁塔标准图集V1.0》的共享改造能力,文章选取了单斜撑三管塔0.65 kN/m2基本风压下的系列塔图,从各塔段的主管应力比和塔顶位移角两个角度,考虑新增天线设备、馈线、爬梯荷载,以及天线设备之间的相互遮挡,利用有限元软件SAP2000对每种塔型进行了常规设计分析和改造增载后的研究分析.由分析结果可知,每种塔型均有可共享改造能力,且随着塔身高度的增加,共享改造的能力逐渐降低. 相似文献
35.
36.
电力杆塔地脚螺栓是杆塔基础的重要组成部分,起着稳固杆塔的作用.随着电力基建的大规模开展,电力杆塔数量也日渐增加,而绝大多数电力杆塔均运行在复杂的野外环境之中,容易导致各类的腐蚀问题.地脚螺栓也因此经常处于各种恶劣环境中,引起的腐蚀问题将严重影响杆塔的安全使用.本文在分析电力杆塔地脚螺栓防腐处理现状的基础上,对地脚螺栓常见的腐蚀原因进行研究,并探讨了几种防腐处理措施,对实际防腐工作有一定指导意义. 相似文献
37.
38.
以欧美标准中的单包容与全包容低温储罐中的钢制储罐抗震设计方法为分析对象,从抗震设防水准与目标、抗震设计反应谱以及抗震设计准则如地震作用调整系数、阻尼比、载荷组合、抗震许用应力、抗倾覆与滑移、晃动波高等方面进行分析对比,为欧美低温储罐抗震设计方法的工程应用提供参考。为实现抗震设防目标以及与该国(区域)建筑抗震以及荷载标准体系协调,欧美低温储罐抗震各设计准则均存在一定的差异,工程设计时应合理应用以避免安全隐患。 相似文献
39.
Yajing Qi Yuying Yang Alkassoumi Hassane Hamadou Qiuyun Shen Bin Xu 《International Journal of Food Science & Technology》2022,57(4):2104-2112
Wheat bran is rich in functional ingredients, but the high level of lipase limits its applications. Tempering–preservation treatment (at 70–90 °C with moisture of 20%–40% for 1–4 h) was exploited for stabilising wheat bran and its effect on polyphenols was investigated. The results showed that more lipase was inactivated at higher tempering moisture, temperature and longer time. The optimum condition for inactivation of wheat bran lipase was 30% moisture and 90 °C for 4 h. The inactivation rate reached 93.8% with a residual enzyme activity of 0.264 U g−1. Under the optimum condition, the sum of free phenolic acids rose from 25.4 to 55.8 µg g−1. As for bound phenolic acids, there was a slight increase of hydroxybenzoic acid derivatives but a slight decrease of hydroxycinnamic acid derivatives. The total contents of phenolic acids before and after stabilisation were not significantly different. This study showed the possibility of using tempering–preservation as an efficient method for inactivation of wheat bran lipase while maintaining its phenolic compounds, which could be used in the production of whole wheat flour. 相似文献
40.
Yu-Xuan Li Ping Li Yu-Zhe Wu Zhen-Liang Xu Ming-Ling Huang 《Ceramics International》2021,47(2):2180-2186
A novel TiO2 thin film was prepared on the ceramic hollow fiber by the sol-gel method using poly(vinylpyrrolidone) (PVP) and polyvinyl alcohol (PVA) as additives. SEM images verified the formation of TiO2 layer with various thickness using different composition of titania sols. The effect of the PVP and PVA contents on the TiO2 sol properties, the separation and the antifouling performance of the ultrafiltration membranes were investigated thoroughly. When the contents of PVP and PVA were 1.0 wt% and 0.8 wt%, respectively, the resultant membrane showed a thickness of 0.55 μm with a pure water flux of 255 L m?2 h?1. In addition, the adherent foulant bovine serum albumin was applied to evaluate the antifouling performance. During the three fouling-recovery cycles, the flux recovery ratio and the flux decay ratio maintained about 99% and 30%. The BSA flux and rejection were still 169 L m?2 h?1 and 96.9% after the cycles, indicating a superior antifouling property. 相似文献