全文获取类型
收费全文 | 68914篇 |
免费 | 6053篇 |
国内免费 | 3111篇 |
专业分类
电工技术 | 4056篇 |
技术理论 | 4篇 |
综合类 | 4336篇 |
化学工业 | 11682篇 |
金属工艺 | 3718篇 |
机械仪表 | 4580篇 |
建筑科学 | 4726篇 |
矿业工程 | 1322篇 |
能源动力 | 2097篇 |
轻工业 | 4991篇 |
水利工程 | 1221篇 |
石油天然气 | 2665篇 |
武器工业 | 484篇 |
无线电 | 9382篇 |
一般工业技术 | 9646篇 |
冶金工业 | 3181篇 |
原子能技术 | 909篇 |
自动化技术 | 9078篇 |
出版年
2024年 | 246篇 |
2023年 | 990篇 |
2022年 | 1839篇 |
2021年 | 2638篇 |
2020年 | 1924篇 |
2019年 | 1715篇 |
2018年 | 1860篇 |
2017年 | 2093篇 |
2016年 | 2144篇 |
2015年 | 2694篇 |
2014年 | 3314篇 |
2013年 | 4225篇 |
2012年 | 4444篇 |
2011年 | 4985篇 |
2010年 | 4391篇 |
2009年 | 4084篇 |
2008年 | 4069篇 |
2007年 | 3710篇 |
2006年 | 3632篇 |
2005年 | 3163篇 |
2004年 | 2383篇 |
2003年 | 2242篇 |
2002年 | 2544篇 |
2001年 | 2120篇 |
2000年 | 1727篇 |
1999年 | 1523篇 |
1998年 | 1400篇 |
1997年 | 1109篇 |
1996年 | 971篇 |
1995年 | 813篇 |
1994年 | 707篇 |
1993年 | 536篇 |
1992年 | 371篇 |
1991年 | 325篇 |
1990年 | 231篇 |
1989年 | 192篇 |
1988年 | 174篇 |
1987年 | 106篇 |
1986年 | 78篇 |
1985年 | 61篇 |
1984年 | 48篇 |
1983年 | 36篇 |
1982年 | 36篇 |
1981年 | 40篇 |
1980年 | 32篇 |
1979年 | 18篇 |
1977年 | 15篇 |
1976年 | 20篇 |
1975年 | 13篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
Neural Machine Translation (NMT) is an end-to-end learning approach for
automated translation, overcoming the weaknesses of conventional phrase-based translation
systems. Although NMT based systems have gained their popularity in commercial
translation applications, there is still plenty of room for improvement. Being the most
popular search algorithm in NMT, beam search is vital to the translation result. However,
traditional beam search can produce duplicate or missing translation due to its target
sequence selection strategy. Aiming to alleviate this problem, this paper proposed neural
machine translation improvements based on a novel beam search evaluation function. And
we use reinforcement learning to train a translation evaluation system to select better
candidate words for generating translations. In the experiments, we conducted extensive
experiments to evaluate our methods. CASIA corpus and the 1,000,000 pairs of bilingual
corpora of NiuTrans are used in our experiments. The experiment results prove that the
proposed methods can effectively improve the English to Chinese translation quality. 相似文献
44.
Jeong Ha-Ram Cho Hye-Seung Cho Youn-Sup Kim Dae-Ok 《Food science and biotechnology》2020,29(12):1763-1770
Food Science and Biotechnology - Hardy kiwifruits (Actinidia arguta) contain various bioactive compounds such as vitamin C and phenolics and can withstand cold temperatures. Changes in soluble... 相似文献
45.
Seung Han Ryu Seil Kim Young-Tae Kwon Young Ki Park Sung-Oong Kang Hong-Baek Cho Yong-Ho Choa 《应用聚合物科学杂志》2020,137(8):48390
Here, we report a facile approach to electrostatically couple the surface charges of graphite nanoplate (GNP) fillers and poly(methyl methacrylate) (PMMA) polymer particles using ethylene maleic anhydride (EMA) copolymer as an electrostatic coupling agent. Our strategy involved switching the intrinsic repulsive electrostatic interactions between the directly exfoliated GNPs fillers and the PMMA particles to attractive electrostatic surface interactions for preparing core(PMMA)-shell (GNP) precursor in order to optimizing 3-dimensionally dispersed polymer nanocomposite. As a result, the electrical conductivity of the composites dramatically increased by a factor of 16.7 in the EMA-coupled GNP/PMMA composites compared with that of the EMA-free GNP/PMMA composites. In addition, the percolation threshold was also notably reduced from 0.32 to 0.159 vol% after electrostatic coupling of the GNPs fillers and PMMA particles. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48390. 相似文献
46.
Yu Zhang Xiaofei Dai Haonan Jin Chaoxin Man Yujun Jiang 《Journal of dairy science》2021,104(4):4023-4032
This study aimed to predict the optimal carbon source for higher production of exopolysaccharides (EPS) by Lactobacillus paracasei TD 062, and to evaluate the effect of this carbon source on the production and monosaccharide composition of EPS. We evaluated the EPS production capacity of 20 strains of L. paracasei under the same conditions. We further investigated L. paracasei TD 062, which showed the highest EPS-producing activity (0.609 g/L), by examining the associated biosynthesis pathways for EPS. Genomics revealed that fructose, mannose, trehalose, glucose, galactose, and lactose were carbon sources that L. paracasei TD 062 could use to produce EPS. We identified an EPS synthesis gene cluster that could participate in transport, export, and sugar chain synthesis, and generate 6 sugar nucleotides. Experimental results showed that the sugar content of the EPS produced using fermentation with the optimized carbon source (fructose, mannose, trehalose, glucose, galactose, and lactose) increased by 115%. Furthermore, use of the optimized carbon source changed the monosaccharide content of the associated EPS. The results of enzyme activity measurements showed significant increases in the activity of 2 key enzymes involved in the glycoside synthesis pathway. Our study revealed that optimizing the carbon source provided for fermentation not only increased the production of EPS, but also affected the composition of the monosaccharides by increasing enzyme activity in the underlying synthesis pathways, suggesting an important role for carbon source in the production of EPS by L. paracasei TD 062. 相似文献
47.
Qiang Wang Lei Shen Tong Xue Gao Cheng Cheng Zhi Huang Hong Jin Fan Yuan Ping Feng 《Advanced functional materials》2021,31(2):2002187
The {100} facet of single-crystalline TiO2(B) is an ideal platform for inserting Li ions, but it is hard to be obtained due to its high surface energy. Here, the single-crystalline TiO2(B) nanobelts from H2Ti3O7 with nearly 70% {100} facets exposed are synthesized, which significantly enhances Li-storage capacity. The first-principle calculations demonstrate an ab in-plane 2D diffusion through the exposed {100} facets. As a consequence, the nanobelts can significantly accommodate Li ions in LiTiO2 formula with specific capacity up to 335 mAh g−1, which is in good agreement with the electrochemical characterizations. Coating with conductive and protective poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), the cut-off discharge voltage is as low as 0.5 V, leading to a capacity of 160.7 mAh g−1 after 1500 cycles with a retention rate of 66% at 1C. This work provides a practical strategy to increase the Li-ion capacity and cycle stability by tailoring the crystal orientation and nanostructures. 相似文献
48.
Natural Computing - The fiber stretching process plays the key role in the process of fiber production and its effects is measured by the stretching ratio. The stretching ratio is determined by the... 相似文献
49.
50.
二氧化碳制冷技术和提升氨制冷安全体系是绿色制冷的重要支撑,北京冬奥会大量采用绿色制冷技术,不仅推动国内制冷行业可持续发展,而且将对2030年碳达峰和2060年碳中和产生深远影响. 相似文献