全文获取类型
收费全文 | 8773篇 |
免费 | 731篇 |
国内免费 | 290篇 |
专业分类
电工技术 | 375篇 |
综合类 | 353篇 |
化学工业 | 1607篇 |
金属工艺 | 417篇 |
机械仪表 | 619篇 |
建筑科学 | 748篇 |
矿业工程 | 242篇 |
能源动力 | 239篇 |
轻工业 | 632篇 |
水利工程 | 105篇 |
石油天然气 | 543篇 |
武器工业 | 60篇 |
无线电 | 1051篇 |
一般工业技术 | 1297篇 |
冶金工业 | 442篇 |
原子能技术 | 100篇 |
自动化技术 | 964篇 |
出版年
2024年 | 34篇 |
2023年 | 172篇 |
2022年 | 269篇 |
2021年 | 360篇 |
2020年 | 287篇 |
2019年 | 255篇 |
2018年 | 273篇 |
2017年 | 335篇 |
2016年 | 305篇 |
2015年 | 316篇 |
2014年 | 476篇 |
2013年 | 540篇 |
2012年 | 547篇 |
2011年 | 667篇 |
2010年 | 532篇 |
2009年 | 511篇 |
2008年 | 500篇 |
2007年 | 424篇 |
2006年 | 417篇 |
2005年 | 359篇 |
2004年 | 256篇 |
2003年 | 225篇 |
2002年 | 185篇 |
2001年 | 175篇 |
2000年 | 162篇 |
1999年 | 254篇 |
1998年 | 180篇 |
1997年 | 175篇 |
1996年 | 123篇 |
1995年 | 99篇 |
1994年 | 84篇 |
1993年 | 58篇 |
1992年 | 40篇 |
1991年 | 43篇 |
1990年 | 28篇 |
1989年 | 25篇 |
1988年 | 18篇 |
1987年 | 21篇 |
1986年 | 12篇 |
1985年 | 7篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1977年 | 2篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1972年 | 2篇 |
1968年 | 2篇 |
排序方式: 共有9794条查询结果,搜索用时 15 毫秒
91.
通过沥青磺化过程的主反应和副反应,进一步讨论了磺化工艺的原理,磺化试剂的选择,溶剂的组成,带水速度,溶剂的回收方式等各种因素对产品质量的影响。 相似文献
92.
Summary A new route for the preparation of soluble fullerenated polymer through the reaction of carbanion intermediates of polymers with fullerenes, particularly C60, is demonstrated. Confirmation of the covalent attachment of C60 to the polystyrene backbone is by a variety of techniques such as UV-Vis, FT-IR, TGA, SEM and 13C NMR etc. The product, which has a visibly brownish yellow cast when compared with the unreacted polymer, is soluble in some common organic solvents. The thermal stability of pure polystyrene is enhanced by C60-chemical modification, and no bonds within the carbon sphere are broken. 相似文献
93.
94.
A simple semi-empirical analysis method for predicting the group effect of pile group under dragload embedded in clay was
described assuming an effective influence area around various locations of pile group. Various pile and soil parameters such
as the array of pile group, spacing of the piles (S), embedment length to diameter ratio of piles (L/D) and the soil properties such as density (γ), angle of internal friction (φ) and pile-soil interface friction coefficient (μ) were considered in the analysis. Model test for dragload of pile group on viscosity soil layer under surface load consolidation
conditions was studied. The variations of dragload of pile, resistance of pile tip and the layered settlement of soil with
consolidation time were measured. In order to perform comparative analysis, single pile was tested in the same conditions.
The predicted group effect values of pile group under dragload were then compared with model test results carried out as a
part of the present investigation and also with the values reported in literatures. The predicted values were found to be
in good agreement with the measured values, validating the developed analysis method. The model test results show that negative
skin friction of pile shaft will reach 80%–90% of its maximum value, when pile-soil relative displacement reaches 2 mm.
Foundation item: Project(50679015) supported by the National Natural Science Foundation of China 相似文献
95.
Effects of a strong polyelectrolyte on the rheological properties of concentrated cementitious suspensions 总被引:1,自引:0,他引:1
Strong polyelectrolytes, referred to as superplasticizers, are known to improve the initial fluidity of concentrated cement suspensions. To quantify how the polyelectrolytes affect the fluidity, we have studied the effect of a strong anionic polyelectrolyte, melamine formaldehyde sulfonate (MFS), on the zeta potential of cement particles and on the steady-shear and low-amplitude rheological properties of cement suspensions. Adsorption of low concentrations of MFS onto the cement particles leads to an inversion in the sign of the surface potential, causing the electrostatically flocculated particles to become electrostatically dispersed and giving rise to a corresponding decrease in the steady-shear viscosity and storage modulus. At an intermediate MFS concentration, the steady-shear viscosity and the storage modulus each display a minimum. This concentration corresponds to that at which the zeta potential becomes constant. Larger concentrations of MFS result in an increase in the viscosity and storage modulus, which is attributed to depletion flocculation. These results thus relate the interaction between particles to the suspension fluidity through the analysis on the surface potential of particles and microstructure of suspension. 相似文献
96.
基于VB和AutoCAD的纸盒辅助设计系统 总被引:1,自引:0,他引:1
在总结现有盒型特点并对其进行科学分类的基础上,结合Visual Basic语言与AutoCAD各自优势,开发具有盒型结构的参数化设计、材料使用率与消耗量、数据存储采集等功能的包装纸盒设计系统,达到提高绘图效率,简化开发过程,实现优化设计的目的。 相似文献
97.
98.
声目标分类识别是声源识别领域的核心问题,然而,在应用深层神经网络进行声目标分类识别时,从少量样本中学习(样本复杂度较低)是一个具有挑战性的问题;针对此问题,提出了一种基于深度学习的小样本声目标识别方法,该方法将手工设计特征和对数梅尔声谱特征结合到一起,扩充了深度学习模型的可利用特征量,提高了声信号识别效率和精度;在实验验证中,该方法在测试集上实现了87.6%的识别精度;更进一步地,用较少量的训练样本对该方法和其它几种主流的深度学习模型的性能进行了比较验证,结果表明,该方法只需要更少量的数据即可实现同样的识别精度,在声源探测领域具有一定应用价值。 相似文献
99.
Kim Jeongeun Kim Sukwha Kim Seongheui Lee Euehun Heo Yoonjeong Hwang Cheol-Yong Choi Yun-Young Kong Hyoun-Joong Ryu Hyeongju Lee Hyeongsuk 《Intelligent Service Robotics》2021,14(5):729-739
Intelligent Service Robotics - This study aims to analyze the concept of companion robots for older adults from the perspective of nursing. This study employed a concept analysis. The literature... 相似文献
100.
彭丽萍 《武汉理工大学学报(材料科学英文版)》2017,32(4):866-870
Indium doped Zn O films were grown on quartz glass substrates by radio frequency magnetron sputtering from powder targets. Indium content in the targets varied from 1at% to 9at%. In doping on the structure, optical and electrical properties of Zn O thin films were studied. X-ray diffraction shows that all the films are hexagonal wurtzite with c-axis perpendicular to the substrates. There is a positive strain in the films and it increases with indium content. All the films show a high transmittance of 86% in the visible light region. Undoped Zn O thin film exhibits a high transmittance in the near infrared region. The transmittance of indium doped Zn O thin films decreases sharply in the near infrared region, and a cut-off wavelength can be found. The lowest resistivity of 4.3×10~(-4) Ω·cm and the highest carrier concentration of 1.86×10~(21) cm~(-3) can be obtained from Zn O thin films with an indium content of 5at% in the target. 相似文献