全文获取类型
收费全文 | 60567篇 |
免费 | 4871篇 |
国内免费 | 2636篇 |
专业分类
电工技术 | 3199篇 |
技术理论 | 6篇 |
综合类 | 4081篇 |
化学工业 | 10056篇 |
金属工艺 | 3805篇 |
机械仪表 | 3794篇 |
建筑科学 | 4628篇 |
矿业工程 | 2165篇 |
能源动力 | 1943篇 |
轻工业 | 3467篇 |
水利工程 | 1048篇 |
石油天然气 | 4458篇 |
武器工业 | 457篇 |
无线电 | 6378篇 |
一般工业技术 | 7083篇 |
冶金工业 | 3273篇 |
原子能技术 | 714篇 |
自动化技术 | 7519篇 |
出版年
2024年 | 100篇 |
2023年 | 928篇 |
2022年 | 1367篇 |
2021年 | 2261篇 |
2020年 | 1778篇 |
2019年 | 1594篇 |
2018年 | 1794篇 |
2017年 | 1998篇 |
2016年 | 1787篇 |
2015年 | 2324篇 |
2014年 | 2974篇 |
2013年 | 3438篇 |
2012年 | 3646篇 |
2011年 | 3997篇 |
2010年 | 3667篇 |
2009年 | 3288篇 |
2008年 | 3254篇 |
2007年 | 3203篇 |
2006年 | 3187篇 |
2005年 | 2764篇 |
2004年 | 2037篇 |
2003年 | 2138篇 |
2002年 | 2478篇 |
2001年 | 2071篇 |
2000年 | 1579篇 |
1999年 | 1673篇 |
1998年 | 1226篇 |
1997年 | 1048篇 |
1996年 | 1091篇 |
1995年 | 835篇 |
1994年 | 626篇 |
1993年 | 464篇 |
1992年 | 359篇 |
1991年 | 271篇 |
1990年 | 203篇 |
1989年 | 164篇 |
1988年 | 151篇 |
1987年 | 86篇 |
1986年 | 69篇 |
1985年 | 37篇 |
1984年 | 30篇 |
1983年 | 23篇 |
1982年 | 23篇 |
1981年 | 13篇 |
1980年 | 20篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1974年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
21.
Mekrattanachai Pagasukon Zhu Lei Setthaya Naruemon Chindawong Chakkresit Song Wei Guo 《Catalysis Letters》2022,152(6):1639-1650
Catalysis Letters - The cobalt-based metal organic frameworks (Co-MOFs) catalyst has been prepared with using terephthalic acid and 4,4′-bipyridine as organic linkers by facile solvothermal... 相似文献
22.
24.
The process of cemented carbides manufacturing requires rapid and field elemental analytical techniques to control and evaluate the properties of products. Calibration-free laser-induced breakdown spectroscopy (CF-LIBS) is such a potential elemental analytical technique. In this work, a portable LIBS instrument combined with a CF method was developed for the analysis of cemented carbides. Three batches of cemented compact carbides without reference samples were analyzed. Qualitative and quantitative analysis of the samples were achieved by using the portable LIBS instrument combined with CF method. To validate the analysis results, X-ray fluorescence spectrometry (XRF) was used to analyze the samples as well. The results of CF-LIBS agreed well with the results of XRF, with relative errors between ?29.53 and 24.70%. The results demonstrated that the portable LIBS instrument combined with CF method was capable for direct and rapid analysis without any need of standard measurements. Notably, with the portable LIBS instrument combined with CF method, acceptable accuracy could be obtained, which is promising for practical field applications. 相似文献
25.
A comparative study on pyrolysis reactivity and gas release characteristics of biomass and coal using TG-MS analysis 总被引:1,自引:0,他引:1
Juntao Wei Xia Liu Qinghua Guo Xueli Chen 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2018,40(17):2063-2069
Pyrolysis reactivity and gas release characteristics of biomass and coals were comparatively investigated using TG-MS. In addition, chemical compositions and structures of tested samples were determined to correlate pyrolysis gas release characteristic. It was found that pyrolysis reactivity and gaseous product release were hardly varied with pyrolysis heating rate. Furthermore, pyrolysis rates of two biomass samples were greater than those of coals, which were mainly attributed to the chemical compositions and the gaseous product evolution process. The result also showed that gaseous product release during pyrolysis process was related to the presence of different functional groups in samples. 相似文献
26.
27.
Zhe Guo Qihua Zhu Shan Wu Changzheng Hu Laijun Liu Liang Fang 《Ceramics International》2018,44(7):7700-7708
Unfilled tungsten bronze ceramics with the nominal formula Ba4PrFe0.5Nb9.5O30 were synthesized via the standard solid-state sintering route, and the effects of oxygen vacancies on the dielectric and electrical properties were investigated in addition to the structure. Room-temperature X-ray diffraction showed that the N2-annealed sample had the largest cell volume. Low-temperature spectrum showed that N2 annealing rendered the dielectric constant and dielectric loss more frequency dispersive, whereas O2 annealing inhibited the frequency dispersion. The dc conductivity of all the samples originated from the electrons produced in the second ionization of oxygen vacancies and was most likely controlled by a mixed conduction mechanism of the electron and oxygen-vacancy ions. The N2-annealed sample has the highest dc conductivity owing to its high concentration of oxygen vacancies. The broadening of the Raman lines and the decrease of Raman intensity for the N2-annealed sample originated from a significant structural disorder. X-ray photoelectron spectra demonstrated that the increased oxygen vacancies caused by the change of valences of Fe and Pr ions contributed to the structural disorder. 相似文献
28.
针对在传统的客户流失预测数据预处理中,使用one-hot编码处理离散属性导致数据维度增加及数据过于稀疏的问题,提出了两种基于多层感知机的改进后的客户流失预测模型。其主要思想是分别使用堆叠自编码器和实体嵌入两种方法对多层感知机进行改进,通过将离散属性的高维编码数据向低维空间映射,有效地减少了one-hot编码产生的稀疏数据,增加了离散属性值之间的关联度。在对两份公开的数据集进行交叉验证后的实验结果表明,改进后的模型既有效地提高了预测的准确度,又维持了传统多层感知机模型在并行化计算方面的优势。 相似文献
29.
Neural Processing Letters - This paper discusses the global exponential stability for a class of hybrid non-autonomous neural networks (HNNNs) with Markovian switching, which includes the factors... 相似文献
30.
World Wide Web - To solve the problem that users’ retrieval intentions are seldom considered by personalized websites, we propose an improved incremental collaborative filtering (CF)-based... 相似文献