全文获取类型
收费全文 | 75492篇 |
免费 | 9607篇 |
国内免费 | 6036篇 |
专业分类
电工技术 | 8220篇 |
技术理论 | 1篇 |
综合类 | 6873篇 |
化学工业 | 9218篇 |
金属工艺 | 5110篇 |
机械仪表 | 5370篇 |
建筑科学 | 6073篇 |
矿业工程 | 2502篇 |
能源动力 | 1958篇 |
轻工业 | 8357篇 |
水利工程 | 2344篇 |
石油天然气 | 2473篇 |
武器工业 | 872篇 |
无线电 | 8824篇 |
一般工业技术 | 7013篇 |
冶金工业 | 2662篇 |
原子能技术 | 1235篇 |
自动化技术 | 12030篇 |
出版年
2024年 | 350篇 |
2023年 | 1390篇 |
2022年 | 3168篇 |
2021年 | 4235篇 |
2020年 | 3019篇 |
2019年 | 2087篇 |
2018年 | 2264篇 |
2017年 | 2448篇 |
2016年 | 2384篇 |
2015年 | 3651篇 |
2014年 | 4297篇 |
2013年 | 5303篇 |
2012年 | 6236篇 |
2011年 | 6419篇 |
2010年 | 5870篇 |
2009年 | 5716篇 |
2008年 | 5759篇 |
2007年 | 5559篇 |
2006年 | 4806篇 |
2005年 | 3799篇 |
2004年 | 2818篇 |
2003年 | 1987篇 |
2002年 | 1892篇 |
2001年 | 1757篇 |
2000年 | 1389篇 |
1999年 | 633篇 |
1998年 | 306篇 |
1997年 | 279篇 |
1996年 | 198篇 |
1995年 | 180篇 |
1994年 | 123篇 |
1993年 | 111篇 |
1992年 | 93篇 |
1991年 | 64篇 |
1990年 | 80篇 |
1989年 | 68篇 |
1988年 | 50篇 |
1987年 | 65篇 |
1986年 | 49篇 |
1985年 | 33篇 |
1984年 | 19篇 |
1983年 | 15篇 |
1982年 | 12篇 |
1981年 | 22篇 |
1980年 | 27篇 |
1979年 | 16篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1959年 | 22篇 |
1951年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
目的:解决当前饮料瓶盖检测系统功能单一、体积偏大、颜色识别率低的问题。方法:提出一种基于ARM处理器的小型饮料瓶盖颜色识别系统设计方案,通过仿真软件HyperLynx的LineSim工具设计四层PCB板,设置传输线参数并进行阻抗匹配仿真分析;利用编译软件Jupyter Notebook实现阈值设置、目标轮廓检测、目标框出等功能。结果:在强、弱光条件下,识别系统对红、绿、蓝3种颜色瓶盖的识别率达到92.7%。结论:与傅里叶描述子相比,该识别系统识别准确率和精度更高,同时系统也具有人脸识别功能,适用于各种智能应用场景。 相似文献
2.
Kai Liu Chenyang Zhou Jiaming Hu Song Zhang Qingqing Zhang Ce Sun Yusheng Shi Huajun Sun Changxia Yin Yuzhen Zhang Yu Fu 《Journal of the European Ceramic Society》2021,41(12):5909-5917
A digital light processing (DLP) technology has been developed for 3D printing lead-free barium titanate (BTO) piezoelectric ceramics. By comparing the curing and rheological properties of slurries with different photosensitive monomer, a high refractive index monomer acryloyl morpholine (ACMO) was chosen, and a design and preparation method of BTO slurry with high solid content, low viscosity and high curing ability was proposed. By further selecting the printing parameters, the single-layer exposure time was reduced and the forming efficiency has been greatly improved. Sintered specimens were obtained after a nitrogen-air double-step debinding and furnace sintering process, and the BTO ceramics fabricated with 80 wt% slurry shows the highest relative density (95.32 %) and piezoelectric constant (168.1 pC/N). Furthermore, complex-structured BTO ceramics were prepared, impregnated by epoxy resin and finally assembly made into hydrophones, which has significance for the future design and manufacture of piezoelectric ceramic-based composites that used in functional devices. 相似文献
3.
Tomohiro Toigawa Yasuhiro Tsubata Takeshi Kai Takuya Furuta Yuta Kumagai Tatsuro Matsumura 《溶剂提取与离子交换》2021,39(1):74-89
ABSTRACT Absorbed-dose estimation is essential for evaluation of the radiation tolerance of minor-actinide-separation processes. We propose a dose-evaluation method based on radiation permeability, with comparisons of heterogeneous structures seen in the solvent-extraction process, such as emulsions forming in the mixture of the organic and aqueous phases. A demonstration of radiation-energy-transfer simulation is performed with a focus on the minor-actinide-recovery process from high-level liquid waste with the aid of the Monte Carlo radiation-transport code PHITS. The simulation results indicate that the dose absorbed by the extraction solvent from alpha radiation depends upon the emulsion structure, and that from beta and gamma radiation depends upon the mixer-settler-apparatus size. Non-negligible contributions of well-permeable gamma rays were indicated in terms of the plant operation of the minor-actinide-separation process. 相似文献
4.
5.
6.
目的建立超高效液相色谱-串联质谱法同时测定糕点中6种常用合成甜味剂的分析方法。方法选用超纯水作为提取溶剂,涡旋和超声提取后,低温离心,取部分上清液加入正己烷除脂,Waters Atlantis■T3色谱柱、甲醇-5 mmol/L甲酸铵(含0.1%甲酸)作为流动相、亲水亲脂平衡型固相萃取柱HLB(hydrophile-lipophile balance)净化。结果6种甜味剂在质量浓度为10~200 ng/mL的曲线范围内呈良好线性关系,相关系数r均大于0.999,平均加标回收率在85.0%-98.2%之间,相对平均偏差(relative standard deviation,RSD)为1.3%~6.7%。结论该方法具有前处理简单、灵敏度高、检测速度快等优点,适合糖精钠、甜蜜素、三氯蔗糖、阿斯巴甜、阿力甜、纽甜的检测,但不适用于安赛蜜的检测。 相似文献
7.
8.
随着全球卫星导航系统(Global Navigation Satellite System,GNSS)技术的迅速发展,定位精度持续优化,其应用范围越来越广.为了突破单基站载波相位差分(Real Time Kinematic,RTK)技术带来的局限性,网络RTK技术应运而生.网络RTK技术使设备在基准站网络覆盖范围内实现精准定位,因此在各个传统行业中的应用越来越广泛.广播电视的信号发射环节非常重要,由于广电发射塔一般地处高山地区,维护维修不便.基于此,设计一种基于网络RTK定位技术的高精度发射塔状态监测方法,可以在保证广电信号安全优质播出方面发挥重要作用. 相似文献
9.
Wenlong Song Shoujun Wang Yang Lu Xuan Zhang Zixiang Xia Kai Sun Guangming Xin 《Ceramics International》2021,47(9):12631-12640
To enhance the tribological performance of Si3N4/TiC ceramics, MoS2/PTFE composite coatings were deposited on the ceramic substrate through spraying method. The micrographs and basic properties of the MoS2/PTFE coated samples were investigated. Dry sliding friction experiments against WC/Co ball were performed with the coated ceramics and traditional ones. These results showed that the composite coatings could significantly reduce the friction coefficient of ceramics, and protect the substrate from adhesion wear. The primary tribological mechanisms of the coated ceramics were abrasive wear, coating spalling and delamination, and the tribological property was transited from slight wear to serious wear with the increase of load because of the lower surface hardness and shear strength. The possible mechanisms for the effects of MoS2/PTFE composite coatings on the friction performance of ceramics were discussed. 相似文献
10.