全文获取类型
收费全文 | 757574篇 |
免费 | 34587篇 |
国内免费 | 16627篇 |
专业分类
电工技术 | 28338篇 |
技术理论 | 45篇 |
综合类 | 25618篇 |
化学工业 | 119751篇 |
金属工艺 | 34252篇 |
机械仪表 | 34078篇 |
建筑科学 | 38792篇 |
矿业工程 | 12375篇 |
能源动力 | 20592篇 |
轻工业 | 67104篇 |
水利工程 | 9965篇 |
石油天然气 | 24864篇 |
武器工业 | 2807篇 |
无线电 | 92587篇 |
一般工业技术 | 113347篇 |
冶金工业 | 92142篇 |
原子能技术 | 9117篇 |
自动化技术 | 83014篇 |
出版年
2023年 | 5845篇 |
2022年 | 10265篇 |
2021年 | 16077篇 |
2020年 | 11837篇 |
2019年 | 10601篇 |
2018年 | 13308篇 |
2017年 | 14522篇 |
2016年 | 13823篇 |
2015年 | 16948篇 |
2014年 | 22810篇 |
2013年 | 39556篇 |
2012年 | 32512篇 |
2011年 | 39423篇 |
2010年 | 33167篇 |
2009年 | 33546篇 |
2008年 | 34102篇 |
2007年 | 33555篇 |
2006年 | 32472篇 |
2005年 | 29316篇 |
2004年 | 23252篇 |
2003年 | 21724篇 |
2002年 | 20629篇 |
2001年 | 19738篇 |
2000年 | 18841篇 |
1999年 | 19906篇 |
1998年 | 30835篇 |
1997年 | 23419篇 |
1996年 | 19476篇 |
1995年 | 15607篇 |
1994年 | 13502篇 |
1993年 | 11860篇 |
1992年 | 9102篇 |
1991年 | 8290篇 |
1990年 | 7575篇 |
1989年 | 7049篇 |
1988年 | 6629篇 |
1987年 | 5356篇 |
1986年 | 5209篇 |
1985年 | 6199篇 |
1984年 | 5774篇 |
1983年 | 4960篇 |
1982年 | 4615篇 |
1981年 | 4511篇 |
1980年 | 4295篇 |
1979年 | 4116篇 |
1978年 | 3784篇 |
1977年 | 4565篇 |
1976年 | 6118篇 |
1975年 | 3120篇 |
1974年 | 3016篇 |
排序方式: 共有10000条查询结果,搜索用时 406 毫秒
181.
Muntasir Hashim Farnoosh Farhad David Smyth‐Boyle Robert Akid Xiang Zhang Philip J. Withers 《工业材料与腐蚀》2019,70(11):2009-2019
The environmental performance of 316L grade stainless steel, in the form of tensile specimens containing a single corrosion pit with various aspect ratios, under cyclic loading in aerated chloride solutions is investigated in this study. Results from environmental tests were compared and contrasted with those obtained using finite element analysis (FEA). Fractography of the failed specimens obtained from experiments revealed that fatigue crack initiation took place at the base of the shallow pit. The crack initiation shifted towards the shoulder and the mouth of the pit for pits of increasing depth. This process is well predicted by FEA, as the strain contour maps show that strain is the highest around the centric strip of the pit. However, for shallow pits, local strain is uniformly distributed around that strip but begins to concentrate more towards the shoulder and the mouth region for increasingly deep pits. 相似文献
182.
183.
184.
185.
186.
187.
Combination of heat treatment and chitosan coating to improve postharvest quality of wolfberry (Lycium barbarum)
下载免费PDF全文
![点击此处可从《International Journal of Food Science & Technology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Zhaojun Ban Wenwen Wei Xiangzheng Yang Jianhua Feng Junfeng Guan Li Li 《International Journal of Food Science & Technology》2015,50(4):1019-1025
The synergistic application of hot water dip at 42 °C for 30 min and 1% chitosan coating on differentiation in postharvest quality traits, microstructure as well as microbiological evolution of wolfberry fruits was investigated. Fresh wolfberry fruits were stored at 2 ± 0.5 °C and 90% relative humidity (RH) for 28 days. Results indicated the combination of prestorage heat treatment and chitosan coating maintained higher levels of ascorbic acid, total phenolic contents and antioxidant capacity as well as lower decay, compared with untreated wolfberry fruits. The possible mechanism was that the heat treatment almost sealed open stomata to limit the sites of pathogen penetration into fruits independently, followed by the biofilm formed by chitosan which controlled secondary infections as well as slowed changes in fruit respiration and metabolic activity in wolfberries. The synergistically treated fruit also exhibited a higher acceptability obtained by sensory analysis after cold storage. In this sense, the integrated application of heat treatment and chitosan coating could be regarded as an effective strategy to extend storage life and maintain the postharvest quality of wolfberry fruits. 相似文献
188.
Thermally conductive polymers offer new possibilities for the heat dissipation in electric and electronic components, for example, by a three‐dimensional shaping of the heat sinks. To face safety regulations, improved fire performance of those components is required. In contrast to unfilled polymers, those materials exhibit an entirely different thermal behavior. To investigate the flammability, a phosphorus flame retardant was incorporated into thermally conductive composites of polyamide 6 and hexagonal boron nitride. The flame retardant decreased the thermal conductivity only slightly. However, the burning behavior changed significantly, due to a different heat propagation, which was investigated using a thermographic camera. An optimum content of hexagonal boron nitride for a sufficient thermal conductivity and fire performance was found between 20 and 30 vol%. The improvement of the fire performance was due to a faster heat release out of the pyrolysis zone and an earlier decomposition of the flame retardant. For higher contents of hexagonal boron nitride, the heat was spread faster within the part, promoting an earlier ignition and increasing the decomposition rate of the flame retardant. 相似文献
189.
Wenli Yao Huajun Zhang Shengwen Zhong Jiwen Li Lingshun Wang 《Journal of Electroceramics》2019,43(1):84-91
Li2ZrO3-modified LiNi0.5Mn0.5O2 materials with improved electrochemical performance were directly synthesized by a simple mechanical milling route with ZrO2, Li2CO3 and Ni0.5Mn0.5(OH)2 precursors... 相似文献
190.
与传统比例-积分-微分(PID)控制方法相比,滑模控制(SMC)方法可以比较容易地将不确定性纳入控制器设计中,从而增强系统的鲁棒性。探索了SMC技术在运载器主动段姿态控制中的工程应用,首先通过分析基于趋近律的SMC系统,提出了降低不连续切换项系数的需求,然后研究了基于干扰上界的SMC方法。三通道小偏差仿真结果验证了两种方法的控制效果,表明第2种控制器的鲁棒性更好,稳态误差小,同时发动机喷管摆角需求较小。 相似文献