全文获取类型
收费全文 | 210116篇 |
免费 | 27179篇 |
国内免费 | 24986篇 |
专业分类
电工技术 | 20112篇 |
技术理论 | 10篇 |
综合类 | 16003篇 |
化学工业 | 42391篇 |
金属工艺 | 8740篇 |
机械仪表 | 12821篇 |
建筑科学 | 10947篇 |
矿业工程 | 3447篇 |
能源动力 | 6760篇 |
轻工业 | 15697篇 |
水利工程 | 4559篇 |
石油天然气 | 5525篇 |
武器工业 | 2150篇 |
无线电 | 29929篇 |
一般工业技术 | 22571篇 |
冶金工业 | 5579篇 |
原子能技术 | 3370篇 |
自动化技术 | 51670篇 |
出版年
2024年 | 894篇 |
2023年 | 3276篇 |
2022年 | 6313篇 |
2021年 | 7724篇 |
2020年 | 7324篇 |
2019年 | 6593篇 |
2018年 | 6137篇 |
2017年 | 8350篇 |
2016年 | 9232篇 |
2015年 | 10516篇 |
2014年 | 10803篇 |
2013年 | 14095篇 |
2012年 | 16139篇 |
2011年 | 18129篇 |
2010年 | 13097篇 |
2009年 | 12855篇 |
2008年 | 13995篇 |
2007年 | 15673篇 |
2006年 | 14881篇 |
2005年 | 12747篇 |
2004年 | 10728篇 |
2003年 | 8474篇 |
2002年 | 6496篇 |
2001年 | 4933篇 |
2000年 | 4127篇 |
1999年 | 3472篇 |
1998年 | 2848篇 |
1997年 | 2306篇 |
1996年 | 1836篇 |
1995年 | 1541篇 |
1994年 | 1359篇 |
1993年 | 1022篇 |
1992年 | 801篇 |
1991年 | 662篇 |
1990年 | 558篇 |
1989年 | 410篇 |
1988年 | 326篇 |
1987年 | 198篇 |
1986年 | 202篇 |
1985年 | 230篇 |
1984年 | 214篇 |
1983年 | 156篇 |
1982年 | 205篇 |
1981年 | 102篇 |
1980年 | 103篇 |
1979年 | 30篇 |
1978年 | 15篇 |
1977年 | 26篇 |
1976年 | 15篇 |
1959年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
941.
A rapid and easy analysis method for polymers is presented. The method involves sample preparation by SFE, separation of the extracted compounds by SFC and simultaneous quantitative detection by FID, as well as identification of unknowns by MS. The applications illustrate how structural research work and routine polymer analysis can be done with this time saving method. 相似文献
942.
943.
Because of its high–temperature chemical stability, SiC ceramic is a promising material for high-temperature device applications such as thermoelectric energy converters. However, the electrical conductivity of SiC ceramic is too low for it to be used as a thermoelectric energy converter at the cold junction. Therefore, we propose a SiC-Si functionally gradient material (FGM) in order to improve the electrical conductivity of the SiC ceramic at the cold junction. An SiC rod was fired in a temperature gradient furnace. One end of the SiC rod was maintained at 2473 K and the other end was maintained at 1973 K for 30 min. After firing, the porous SiC edge fired at 1973 K was dipped into molten Si in order to infiltrate molten Si into the porous SiC. The microstructure of the FGM is classified into three regions: the SiC-Si composite material; the porous SiC ceramic; and the densified SiC ceramic. The electrical conductivity, the Seebeck coefficient and the thermal conductivity for each region of SiC-Si FGM was measured at 300 K; a figure of merit was calculated. The figure of merit of the SiC-Si FGM at the cold junction, at room temperature, was 108 times higher than that of a nongradient SiC ceramic. 相似文献
944.
树脂热解炭制备碳化硅晶须 总被引:6,自引:1,他引:5
用自制的配合醛树脂热解和炭源,用SIO2超细汾作原,根据碳热还原原理,利用常规加热和微波加热两种方式,分别制备了直径在纳米级的SiC晶须,X射线衍射、透射电检测结果表明:制备工艺和条件对SiC晶须的性质有较大的影响。 相似文献
945.
946.
Isabelle Travers Alain Jacquet Adlaïde Brisset Claire Maite 《Journal of the science of food and agriculture》2002,82(9):983-989
Monitoring the hydrolysis or disappearance of starch by the starch iodine test is a simple procedure for determining the maturity of cider apples, but it does not indicate the exact amount of starch present. So far, studies of starch in apples have dealt exclusively with dessert apples. In this paper the relationship between the visual starch index, the dark‐coloured surface area and the real starch content was studied in two varieties of cider apple commonly used in Normandy (France). Starch determination in cider apples required adapting the protocol provided by the Boehringer enzymatic kit. The work led to proposing a simplified index with five scales instead of 10. This index gives the correspondences between the new and old scales as well as the probable starch contents for each new scale. © 2002 Society of Chemical Industry 相似文献
947.
从限额设计谈投资控制 总被引:5,自引:0,他引:5
文章根据设计阶段投资控制的现状及存在问题,提出只有在设计行业全面推行限额设计,深化设计阶段的投资控制工作,才能从根本上体现全过程投资控制的理念,提高投资控制效果,节约建设工程总投资。 相似文献
948.
In building energy simulation, an integrated modelling of airflow in the building needed. Therefore, in this paper two approaches are used for building energy simulation: zonal network for modelling of the building segments and Computational Fluid Dynamics (CFD) for modelling of the airflow. It is noted that a synchronize solution process is needed for the building and the CFD equation-sets. For this purpose an iterative procedure is used to corresponding solution of these equations. 相似文献
949.
Recently, Diabaté et al. [Diabaté, L., Blanc, Ph., Wald, L., 2004. Solar climate in Africa. Solar Energy 76, 733–744] created a map of solar radiation climate in Africa using clearness index for 62 sites. They established a solar climate class II located in Malawi and Madagascar. However, their analysis did not include any irradiation data from a site in Malawi. In this study, the solar radiation climate of Malawi has been studied using long-term global radiation data from a local site. The mean monthly (Ktm) and seasonal (Kts) daily clearness indices for the site were computed. It is observed that Ktm has two maxima in a year (Ktm = 0.58 in May and Ktm = 0.64 in September), in close conformity with findings of Diabaté et al. (2004). Other results are presented and discussed. 相似文献
950.
基于故障树与灰关联分析的鱼雷故障诊断 总被引:2,自引:0,他引:2
将灰色关联度与故障树联合运用于鱼雷故障诊断,为鱼雷的故障诊断提供了一种新途径。在鱼雷动力系统故障树诊断模式识别中,运用灰色系统理论中的灰关联分析,通过进行关联度计算及排序,对各种故障模式发生的可能性大小作出了判断,从而为处理故障的轻重缓急、控制故障的发生以及改进系统的可靠性提供了理论依据。实例诊断表明,这种方法是有效可行的,并且诊断结果可靠。 相似文献