全文获取类型
收费全文 | 1914篇 |
免费 | 158篇 |
国内免费 | 80篇 |
专业分类
电工技术 | 91篇 |
综合类 | 198篇 |
化学工业 | 129篇 |
金属工艺 | 78篇 |
机械仪表 | 144篇 |
建筑科学 | 713篇 |
矿业工程 | 76篇 |
能源动力 | 27篇 |
轻工业 | 125篇 |
水利工程 | 200篇 |
石油天然气 | 16篇 |
武器工业 | 7篇 |
无线电 | 43篇 |
一般工业技术 | 226篇 |
冶金工业 | 22篇 |
原子能技术 | 1篇 |
自动化技术 | 56篇 |
出版年
2024年 | 2篇 |
2023年 | 6篇 |
2022年 | 36篇 |
2021年 | 42篇 |
2020年 | 40篇 |
2019年 | 32篇 |
2018年 | 28篇 |
2017年 | 63篇 |
2016年 | 57篇 |
2015年 | 66篇 |
2014年 | 127篇 |
2013年 | 89篇 |
2012年 | 143篇 |
2011年 | 165篇 |
2010年 | 154篇 |
2009年 | 153篇 |
2008年 | 144篇 |
2007年 | 175篇 |
2006年 | 134篇 |
2005年 | 124篇 |
2004年 | 78篇 |
2003年 | 63篇 |
2002年 | 53篇 |
2001年 | 33篇 |
2000年 | 34篇 |
1999年 | 25篇 |
1998年 | 23篇 |
1997年 | 9篇 |
1996年 | 12篇 |
1995年 | 11篇 |
1994年 | 12篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1979年 | 1篇 |
排序方式: 共有2152条查询结果,搜索用时 15 毫秒
1.
2.
R.F. Newsome A. Mostyn J.P. Wilson A. Alibhai N. Bollard L. Randall M.G.G. Chagunda C.J. Sturrock M. Keane M. Green J.N. Huxley C.S. Rutland 《Journal of dairy science》2021,104(5):6238-6252
The digital cushion is an essential part of maintaining a healthy foot, working to dissipate foot strike and body weight forces and lameness from claw horn disruption lesions. Despite the importance of the digital cushion, little is known about the basic anatomy, adipocyte morphology, and fatty acid composition in relation to age, limb position, and body condition score. In total, 60 claws (from 17 cows) were selected and collected from a herd, ensuring that body condition score data and computed micro-tomography were known for each animal. Digital cushion tissue underwent histological staining combined with stereology, systematic random sampling, and cell morphology analysis, in addition to lipid extraction followed by fatty acid analysis. The results describe digital cushion architecture and adipocyte sizes. Adipocyte size was similar across all 4 claws (distal left lateral and medial and distal right lateral and medial) and across the ages (aged 2–7 yr); however, animals with body condition score of 3.00 or more at slaughter had a significantly increased cell size in comparison to those with a score of less than 2.50. Of 37 fatty acid methyl esters identified, 5 differed between either the body condition score or different age groups. C10:0 capric acid, C14:0 myristic acid, C15:0 pentadecanoic acid, and C20:0 arachidic acid percentages were all lesser in lower body condition score cows, whereas C22:1n-9 erucic acid measurements were lesser in younger cows. Saturated fatty acid, monounsaturated fatty acid, and polyunsaturated fatty acid percentages were not altered in the different claws, ages, or body condition score groups. Triglyceride quantities did not differ for claw position or age but had decreased quantities in lower body condition score animals. Digital cushion anatomy, cellular morphology, and fatty acid composition have been described in general and also in animals with differing ages, body condition scores, and in the differing claws. Understanding fat deposition, mobilization, and composition are essential in not only understanding the roles that the digital cushion plays but also in preventing disorders and maintaining cattle health and welfare. 相似文献
3.
4.
Zhao Chen Xiaojing Zhang Yongpeng Ma Shilei Li Qi Pang Haoxu Wang Gaochao Sun 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2020,95(12):3252-3260
The appearance of heavy metals in wastewater brings a major burden to wastewater treatment plants, due to the high toxicity to microorganisms. Several commonly used heavy metals, including Zn(II), Cd(II), Hg(II), and Pb(II) were adopted to clear the individual and joint toxicity to the completely autotrophic nitrogen removal over nitrite (CANON) process in six sequencing batch reactors. The obtained results suggested that the nitrogen removal performances were transiently inhibited, but rapidly recovered. The restoration period under the stress of Hg(II) and Pb(II) was shorter than that under Zn(II), Cd(II), and the joint heavy metals. During the long-term exposure, Cd(II) in 1mg L−1 slightly inhibited the nitrogen removal, while Zn(II), Hg(II), Pb(II), and mixture showed a negligible impact on CANON process. The defense of extracellular polymeric substances (EPS), the good adaptability of functional bacteria, and the inducement of resistant genera by heavy metals all contributed to the robustness and stability of CANON process. Therefore, it is feasible to treat nitrogenous wastewater containing low heavy metals using CANON process. © 2020 Society of Chemical Industry 相似文献
5.
静载试验作为复合路基的一种重要检测手段而广泛应用,然而,在工程质量检测中,常出现检测结果与实际情况不符的情况,除人为操作因素外,垫层模拟过于简单是主要原因。借助引入弹性垫层,提出一种桩土复合路基静载试验改进方法。首先,基于数值模拟计算,建立复合路基桩土应力比n和桩土相对位移Δs、弹性垫层厚度h和弹性垫层模量E的函数关系;其次,通过模拟结果和路堤荷载结果对比,确定不同桩型复合路基静载试验中弹性垫层参数选择范围,最后,利用现场对比试验和实测结果,论证桩土复合路基静载试验改进方法的正确性和可靠性。 相似文献
6.
Sarunas Varnagiris Jolanta Doneliene Simona Tuckute Jurate Cesniene Darius Milcius 《Polymer-Plastics Technology and Engineering》2018,57(13):1296-1302
Conventional expanded polystyrene can absorb moisture, which significantly degrades its properties. In the present study, it was demonstrated that SiO2 can be deposited on polystyrene beads before pre-expansion and molding steps. Under the applied test conditions, expanded polystyrene with nanocrystalline SiO2 additives had approximately 10% lower moisture adsorption and an 8.4% better resistance to deformation. Expanded polystyrene analysis suggested that the observed improvements were caused by the hydrophobic nature of nanocrystalline SiO2 and, even more importantly, because SiO2 acted as an amalgamation catalyst and significantly increased adhesion between the expanded polystyrene beads during the expanded polystyrene molding process. 相似文献
7.
The common cushion layer used in the geomembrane face rockfill dam is made of granular materials such as gravel and non-fine concrete where bulge deformation or failure of geomembrane is very likely to occur in its surface holes. The curve intersection method based on the thin film theory is the common method used to analyze the bulge deformation of the geomembrane in the surface holes of cushion layer. However, it is inaccurate due to the neglection of horizontal (tangential) displacement of the geomembrane. Based on the FEM theory, a new method is proposed, which takes the horizontal (tangential) displacement of geomembrane into consideration, and is validated by the bulge tests on the geomembrane in a circular hole. The deformations and strains of the geomembrane in different shapes of holes are analyzed by this method, and different strain distributions and failure modes are obtained. The curve intersection method is also used to compare with the new method under the same condition. It is indicated that there is less difference in the deformation and average strain of the geomembrane when the water pressure is low. However, when the water pressure is relatively high, the influences of horizontal (tangential) displacement of the geomembrane on its strain should not be neglected. 相似文献
8.
《Ceramics International》2021,47(23):32710-32719
The formation of micro-cracks in Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode particles is an extremely important factor affecting the electrochemical characteristics after long-term cycling. Generally, cracks can be divided into intergranular crack and intracrystalline crack according to their positions. Coating has been confirmed as a highly effective strategy to relieve intergranular cracks. However, the intracrystalline cracks of primary-like particles have rarely been studied. In this work, ethoxy functional polysiloxane (EPS) was directly coated on the surface of original NCM811 by tetraethyl orthosilicate (TEOS) hydrolytic polycondensation method without any additives. Then, the microstructure, micromorphology, surface state and electrochemical properties were investigated in detail by XRD, SEM, TEM, CV and EIS. The results displayed that the micro-cracks of primary-like particles were effectively suppressed under appropriate EPS coating. Accordingly, excellent capacity retention of 95.6% (100 cycles, 1C) and rate performance (144.6 mA h/g, 5C) were obtained. These improved mechanical and electrochemical properties are considered to be related to the EPS stress buffer layer, suppressed oxygen vacancies, inhibited phase transition and reduced volume change. 相似文献
9.
本文对直接计算条形基础和短形基础换土垫层厚度的方法进行了探讨,建立力平衡方程直接计算,可不需试算就可直接算出换土垫层厚度。 相似文献
10.