全文获取类型
收费全文 | 101185篇 |
免费 | 10748篇 |
国内免费 | 6300篇 |
专业分类
电工技术 | 7653篇 |
技术理论 | 1篇 |
综合类 | 8282篇 |
化学工业 | 15035篇 |
金属工艺 | 6237篇 |
机械仪表 | 7081篇 |
建筑科学 | 8370篇 |
矿业工程 | 3397篇 |
能源动力 | 2670篇 |
轻工业 | 7539篇 |
水利工程 | 2328篇 |
石油天然气 | 4771篇 |
武器工业 | 1236篇 |
无线电 | 12036篇 |
一般工业技术 | 10717篇 |
冶金工业 | 4045篇 |
原子能技术 | 1325篇 |
自动化技术 | 15510篇 |
出版年
2024年 | 494篇 |
2023年 | 1450篇 |
2022年 | 3185篇 |
2021年 | 4336篇 |
2020年 | 3189篇 |
2019年 | 2552篇 |
2018年 | 2787篇 |
2017年 | 3200篇 |
2016年 | 2951篇 |
2015年 | 4407篇 |
2014年 | 5366篇 |
2013年 | 6466篇 |
2012年 | 7507篇 |
2011年 | 7891篇 |
2010年 | 7353篇 |
2009年 | 7370篇 |
2008年 | 7140篇 |
2007年 | 6985篇 |
2006年 | 6288篇 |
2005年 | 5372篇 |
2004年 | 3692篇 |
2003年 | 2934篇 |
2002年 | 2772篇 |
2001年 | 2489篇 |
2000年 | 2022篇 |
1999年 | 1766篇 |
1998年 | 1127篇 |
1997年 | 1001篇 |
1996年 | 860篇 |
1995年 | 705篇 |
1994年 | 578篇 |
1993年 | 427篇 |
1992年 | 331篇 |
1991年 | 268篇 |
1990年 | 219篇 |
1989年 | 196篇 |
1988年 | 143篇 |
1987年 | 91篇 |
1986年 | 87篇 |
1985年 | 36篇 |
1984年 | 39篇 |
1983年 | 21篇 |
1982年 | 27篇 |
1981年 | 17篇 |
1980年 | 27篇 |
1979年 | 10篇 |
1978年 | 8篇 |
1976年 | 7篇 |
1959年 | 8篇 |
1951年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 19 毫秒
51.
Qiang Xia Tao Feng Xiaowei Lou Ying Wang Yangying Sun Daodong Pan Jinxuan Cao 《International Journal of Food Science & Technology》2020,55(2):669-680
As a decisive attribute, flavour could be influenced by HP treatments through multiple physical and chemical pathways within the high pressure (HP)-assisted meat curing process. This investigation aimed to identify the major pathway influencing volatile flavour patterns of two representative vinasse-cured duck (VCD) products with HP treatments (150–300 MPa/15 min), including wet and dry types, by employing headspace fingerprinting as an untargeted approach. Results suggested that HP treatments greatly lowered moisture contents and increased Warner-Bratzler shear force and thiobarbituric acid reactive substances of the cured samples. According to multivariate models, the volatile flavour patterns of the HP-processed VCD could be clearly separated from the unprocessed samples, but the VCD pressurised at different intensities represented similar volatile fingerprinting, which was validated by e-nose analysis. The discriminant analysis (OPLS-DA) model outlined vinasse-derived ethanol, acetic acid, 3-methyl-1-butanol, 2-methyl-1-butanol, phenethyl alcohol and 2-methyl-3-octanone as the major discriminant aromas across the unpressurised and pressurised samples. 相似文献
52.
53.
The hippocampus is crucial in learning, memory and emotion processing, and is involved in the development of different neurological and neuropsychological disorders. Several epigenetic factors, including DNA methylation, histone modifications and non-coding RNAs, have been shown to regulate the development and function of the hippocampus, and the alteration of epigenetic regulation may play important roles in the development of neurocognitive and neurodegenerative diseases. This review summarizes the epigenetic modifications of various cell types and processes within the hippocampus and their resulting effects on cognition, memory and overall hippocampal function. In addition, the effects of exposure to radiation that may induce a myriad of epigenetic changes in the hippocampus are reviewed. By assessing and evaluating the current literature, we hope to prompt a more thorough understanding of the molecular mechanisms that underlie radiation-induced epigenetic changes, an area which can be further explored. 相似文献
54.
以新型褶式滤筒为研究对象,选取滤筒褶数N_2、褶夹角θ、褶高h、过滤风速v为影响因子,除尘器压力损失为响应值,基于响应曲面法分析影响因子对压力损失的影响,建立滤筒除尘器压力损失的预测模型并得到滤筒褶皱结构最优参数。以滤筒内径D、筒体高度D_1为标准尺寸,依据相关国家标准设计滤筒筒体部分;以锥体高度D_2、锥体上圆直径D_3为系列尺寸,利用尺寸变化法设计锥体部分;通过Access软件建立滤筒产品数据库。结果表明:当θ=5.2°,N_2=50,v=0.01 m/s,h=0.035 m时,除尘器压力损失最低;当D_1=1 000 mm,D=320 mm时,D_2和D_3最佳值分别为600,130 mm,故采用D_2/D_1=0.6,D_3/D=0.4的比值设计相应滤筒锥体系列。 相似文献
55.
通过对CSFB语音方案原理的分析,结合业务模型及网络安全等方面的考虑,提出了一种支持4G CSFB的MSC改造规模预测方法,为端局后续建设提供了参考. 相似文献
56.
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
57.
该文针对当前矿井炮掘巷道大断面掘进普遍存在掘进施工较慢的实际,结合公司实际情况,有针对性地提出了解决的办法。 相似文献
58.
59.
Tian Xiaoying Peng Hui Luo Xuguang Nie Shiyuan Zhou Feng Peng Xiaoyan 《International Journal of Control, Automation and Systems》2020,18(4):897-910
International Journal of Control, Automation and Systems - There is a class of typical nonlinear industrial process, which can be characterized by a first-order inertia plus pure delay model in an... 相似文献
60.
Xu Zhi-Zheng Jiang Feng Zhong Chong-Quan Gou Yong-Jie Teng Hong-Fei 《Structural and Multidisciplinary Optimization》2020,61(1):207-223
Structural and Multidisciplinary Optimization - The overall layout optimization design of an orbital propellant depot involves the optimization of shape, size, and positions of propellant tanks in... 相似文献