全文获取类型
收费全文 | 35019篇 |
免费 | 3453篇 |
国内免费 | 2003篇 |
专业分类
电工技术 | 6101篇 |
综合类 | 3617篇 |
化学工业 | 3169篇 |
金属工艺 | 1191篇 |
机械仪表 | 1382篇 |
建筑科学 | 7544篇 |
矿业工程 | 1233篇 |
能源动力 | 1415篇 |
轻工业 | 2459篇 |
水利工程 | 3032篇 |
石油天然气 | 1210篇 |
武器工业 | 135篇 |
无线电 | 2157篇 |
一般工业技术 | 2466篇 |
冶金工业 | 1299篇 |
原子能技术 | 689篇 |
自动化技术 | 1376篇 |
出版年
2024年 | 133篇 |
2023年 | 424篇 |
2022年 | 899篇 |
2021年 | 1030篇 |
2020年 | 1129篇 |
2019年 | 1005篇 |
2018年 | 965篇 |
2017年 | 1176篇 |
2016年 | 1222篇 |
2015年 | 1360篇 |
2014年 | 2206篇 |
2013年 | 1977篇 |
2012年 | 2618篇 |
2011年 | 2796篇 |
2010年 | 2029篇 |
2009年 | 2178篇 |
2008年 | 2164篇 |
2007年 | 2542篇 |
2006年 | 2252篇 |
2005年 | 1840篇 |
2004年 | 1520篇 |
2003年 | 1255篇 |
2002年 | 1047篇 |
2001年 | 921篇 |
2000年 | 758篇 |
1999年 | 598篇 |
1998年 | 498篇 |
1997年 | 427篇 |
1996年 | 314篇 |
1995年 | 268篇 |
1994年 | 213篇 |
1993年 | 144篇 |
1992年 | 125篇 |
1991年 | 87篇 |
1990年 | 57篇 |
1989年 | 64篇 |
1988年 | 38篇 |
1987年 | 31篇 |
1986年 | 24篇 |
1985年 | 32篇 |
1984年 | 22篇 |
1983年 | 15篇 |
1982年 | 16篇 |
1981年 | 11篇 |
1980年 | 23篇 |
1979年 | 7篇 |
1977年 | 2篇 |
1955年 | 1篇 |
1954年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
991.
992.
This work continued our general research program on obtaining metallic cerium by electrodeposition from NaCeF4 dis-solved in different molten fluorides. The structure of NaCeF4 (cubic or hexagonal depe... 相似文献
993.
要实现矿区的持续发展,需定量地知道矿区资源承载力未来将发生怎样的变化,以保证其资源消耗在承载力允许范围内。矿区是一个开放复杂巨系统,且常缺乏资源情况的历史数据。系统动力学不需要历史数据就能揭示开放复杂巨系统的运行规律;情景分析法通过定量地设定未来多种可能的发展情景,能解决使用系统动力学模型进行预测时,控制变量难以定量的问题。以马钢南山矿区为例,证实系统动力学与情景分析法的结合定量预测矿区资源承载力的可行性,并阐述如何利用该方法进行资源承载力的预测。 相似文献
994.
介绍了流光放电氨法脱硫技术的原理、工艺流程、特点及在某燃煤电厂烟气脱硫工程中的应用。运行结果非常成功,脱硫率达到96.0%~99.9%,副产品硫酸铵作为化肥外销。由于在脱硫后增设了电除雾器,解决了尾气氨逃逸、气溶胶烟羽、酸雾超标问题。 相似文献
995.
随器补偿是新生事物,优点很多,但要推行起来,一些技术问题还难以解决,主要是安装位置的选择、补偿容量的确定、以及随器补偿电容器保护问题。文章结合当前城乡电网具体情况,针对这些难点问题进行探讨,提出了解决这些难点的意见。 相似文献
996.
制冷剂的替代是当今国内外制冷空调界关注的热点问题.一年多来,国外在不饱和氟化烯烃(HFO)及其混合制冷剂的应用开发上获得了可喜成果.为使我国更多业内人士及时了解相关进展与成果,以笔记摘录的形式介绍了国外在HFO及其混合制冷剂的状态方程、特性参数、传输特性、系统性能等方面的研究成果以及一些产品研发成果. 相似文献
997.
The esterification of cellulose hydroxyl groups with natural carboxylic acids in mild conditions represents an adequate pathway in obtaining cellulose derivatives with different useful properties. In this article, authors report the synthesis of new mixed ester of cellulose and cellulose acetate nicotinate (CAN) , in a homogenous medium using DMF as solvent, cellulose acetate (CA) as starting cellulosic material, and nicotinic acid as an esterification agent in the presence of p-toluenesulfonyl chloride and pyridine. FTIR and NMR techniques were used to prove the binding of nicotinoyl group at free hydroxyl groups of CA. The obtained CAN was electrospun by electrospinning technique to obtain adsorbent ultrafine fibers, evidenced by SEM images, with high specific surface area. Monolayer Langmuir and empirical Leundrich isotherms were used to assess the adsorption capacity for rhodamine B dye of electrospun CAN in comparison with that of electrospun CA used as starting material. Langmuir isotherm led to a better assessment of experimental data suggesting that the adsorption is mainly determined by hydrogen bonds formed between carboxylic OH hydrogen bonding donor and pyridine N hydrogen bonding acceptor. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47772. 相似文献
998.
Mohammed Alomair Stelios Georgiou Stella Stylianou 《Quality and Reliability Engineering International》2021,37(1):90-107
Since their introduction by Box and Hunter, resolution criteria have been widely used when comparing regular fractional factorials designs. In this article, we investigate how a generalized resolution criterion can be used to assess some recently developed three-level screening designs, such as definitive screening designs (DSDs) and screening designs from weighing matrices. The aim of this paper is to capture the projection properties of those three-level screening designs, complementing the work of Deng and Tang, who used generalized resolution and minimum aberration criteria for ranking different two-level designs, particularly Plackett-Burman and other nonregular factorial designs. An advantage of generalized resolution, extended here to work on three-level designs, is that it offers a useful criterion for ranking three-level screening designs, whereas the Deng and Tang resolution is used mainly for the assessment of two-level designs. In addition, we applied a projection estimation capacity (PEC) criterion to select three-level screening designs with desirable properties. Practical examples and the best projections of the designs are presented in tables. 相似文献
999.
1000.
Hongwei Shang Yaqin Li Yanghuan Zhang Dongliang Zhao Yan Qi Xiaoyi Xu 《International Journal of Hydrogen Energy》2021,46(34):17840-17852
In order to improve the hydrogen storage performances of TiFe-based alloys, a new type of TiFe0.8-mNi0.2Com (m = 0, 0.03, 0.05 and 0.1) alloys were prepared through vacuum medium-frequency induction melting. XPS results showed that the composition of surface oxide film contains TiO2, FeO and NiO for the cobalt-free alloy, and it also includes CoO and Co3O4 besides the above oxides for the cobalt-containing alloys. The activation temperature is 523, 403, 383 and 373 K for the TiFe0.8-mNi0.2Com (m = 0, 0.03, 0.05 and 0.1) alloys, respectively. The changes of the composition and microstructure of the surface oxide film are the root causes of the reduction of the activation temperature. XRD and SEM analyses showed that all the alloys are composed of the majority phase of TiFe phase and non-hydrogenated phase of Ti2Fe phase. Adding appropriate amount of cobalt is beneficial to inhibiting the generation of Ti2Fe phase and increasing the cell volume of TiFe phase. The hydrogenation capacity is proportional to the content of TiFe phase, which is 1.11, 1.48, 1.54 and 1.29 wt% for the TiFe0.8-mNi0.2Com (m = 0, 0.03, 0.05 and 0.1) alloys at 313 K, respectively. The hydrogenation plateau performance also is improved correspondingly. 相似文献