全文获取类型
收费全文 | 87835篇 |
免费 | 9280篇 |
国内免费 | 5079篇 |
专业分类
电工技术 | 6886篇 |
技术理论 | 5篇 |
综合类 | 6566篇 |
化学工业 | 13230篇 |
金属工艺 | 4985篇 |
机械仪表 | 5663篇 |
建筑科学 | 7151篇 |
矿业工程 | 2876篇 |
能源动力 | 2648篇 |
轻工业 | 6256篇 |
水利工程 | 1936篇 |
石油天然气 | 4447篇 |
武器工业 | 1107篇 |
无线电 | 10766篇 |
一般工业技术 | 9193篇 |
冶金工业 | 4096篇 |
原子能技术 | 1171篇 |
自动化技术 | 13212篇 |
出版年
2024年 | 458篇 |
2023年 | 1521篇 |
2022年 | 3065篇 |
2021年 | 4269篇 |
2020年 | 3085篇 |
2019年 | 2472篇 |
2018年 | 2711篇 |
2017年 | 3089篇 |
2016年 | 2761篇 |
2015年 | 3951篇 |
2014年 | 4882篇 |
2013年 | 5843篇 |
2012年 | 6729篇 |
2011年 | 7062篇 |
2010年 | 6219篇 |
2009年 | 6051篇 |
2008年 | 5815篇 |
2007年 | 5222篇 |
2006年 | 5072篇 |
2005年 | 4319篇 |
2004年 | 2919篇 |
2003年 | 2142篇 |
2002年 | 2050篇 |
2001年 | 1646篇 |
2000年 | 1542篇 |
1999年 | 1422篇 |
1998年 | 1048篇 |
1997年 | 896篇 |
1996年 | 851篇 |
1995年 | 699篇 |
1994年 | 518篇 |
1993年 | 382篇 |
1992年 | 348篇 |
1991年 | 221篇 |
1990年 | 184篇 |
1989年 | 133篇 |
1988年 | 143篇 |
1987年 | 85篇 |
1986年 | 79篇 |
1985年 | 39篇 |
1984年 | 43篇 |
1983年 | 27篇 |
1982年 | 38篇 |
1981年 | 26篇 |
1980年 | 26篇 |
1979年 | 19篇 |
1978年 | 8篇 |
1976年 | 12篇 |
1959年 | 9篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
The short contact time dissolution of vitrinite and inertinite concentrates of an Australian bituminous coal was studied under isothermal conditions with tetralin as solvent. The reactivity of the two maceral types and the yields and nature of the products were determined for a range of reaction temperatures (400, 420 and 440 °C) and reaction times (2–20 min). The dissolution of vitrinite proceeded at a significantly greater rate than for inertinite and was associated with greater selectivity to soluble non-gaseous products. At very short reaction times (2 min), the vitrinite underwent solubilizing reactions to yield products of higher molecular weight and greater oxygen functionality than was the case for inertinite, for which changes in the chemical nature of the products were negligible over the range of conditions studied. At longer reaction times (5 min), the composition of the vitrinite-derived products was similar to that of the inertinite-derived products. 相似文献
142.
143.
Ching-Liang Su 《Journal of Intelligent and Robotic Systems》2006,45(1):1-14
This research uses the object extracting technique to extract the index, middle and ring fingers from the hand images. The algorithm developed in this research can find the precise locations of the different fingers' fingertips and the finger-to-finger-valleys. After finding the positions of the fingertips and finger-valleys, the index, middle and ring fingers can be extracted from the hand images by using morphological technique. The extracted index, middle and ring fingers contain many useful geometry features. One can use these features to do the person's identification. The orientations of the index, middle and ring fingers are found in this research. Image rotating, image shifting, and image interpolating techniques are used to align different persons' index, middle and ring fingers. Image subtraction is used to exam the difference of two index, middle and ring finger images. In this research so far only use the index, middle and the ring fingers as the features to identify different persons.
★This work was supported by National Science Council under grant NSC 93-2213-E-212-011. 相似文献
144.
�Ĵ������Ȼ�����������б�����Դ̽�� 总被引:11,自引:0,他引:11
本文应用天然气中甲烷、乙烷的碳同位素,甲烷的氢同位素,汞含量及天然气成分等指标,探讨了四川盆地天然气成因分类;并结合地质情况对气源层进行了探讨。 相似文献
145.
Yewang Su Baohua Ji Yonggang Huang Kehchih Hwang 《Journal of Materials Science》2007,42(21):8885-8893
Wet adhesion is widely adopted in biological adhesion systems in nature. Wet adhesion is studied in this paper with the focus
on the effect of different contact shapes (flat, concave, convex, and ring-like) on the adhesion force. The evolution of the
liquid bridge between a fiber tip and substrate during the detaching process shows two transition points. The first transition
from the radius-controlled to the contact-angle controlled process is critical to influence the strength and robustness of
adhesion. We show that a concave shape is more effective than a flat one, while a convex shape has no advantage. A ring-like
contact shape has advantages in a hydrophobic environment and on a rough surface. 相似文献
146.
Oxide films were deposited on different substrates by laser molecular beam epitaxy. Reflection high-energy electron diffraction was performed to in situ investigate the change of growth mode and the lattice relaxation during the growth. An asymmetrical phenomenon was found in the two kinds of strain states, compressive stress and tensile stress of heterostructures with different lattice mismatch. In the case of BaTiO3/SrTiO3 (2.2%), 2D layer-by-layer growth mode without lattice relaxation can be maintained for a longer period for BTO films on STO with compressive stress, comparing to STO films on BTO with tensile stress. When MgO films were deposited on SrTiO3 with a large mismatch of 7.8%, compressive stress leads to rapid lattice relaxation with a very thin wet layer, and 3D strained island were observed. As a comparison, SrTiO3 films on MgO with tensile stress were configured. No RHEED patterns can be observed duo to a large tensile stress. 相似文献
147.
面向企业信息化实现管理现代化 总被引:1,自引:0,他引:1
为适应社会信息化技术的发展,必须积极推行企业信息化,企业信息化引发管理革命,从而丰富了企业管理现代化的内容。本文论述了上述三方面的内部及演化关系,指出只有面向企业信息化,才能充分实现企业管理现代化。 相似文献
148.
文章介绍了几种缝纫设备输送动力装置的送布原理,认为应针对不同的面料特性及经制工艺要求,选用合适的设备输送系统。 相似文献
149.
烧结砖与墙体材料革新 总被引:4,自引:0,他引:4
1中国墙体材料的发展中国经济的快速发展拉动了建筑业及其相关的墙体材料的需求与生产,墙体材料获得了很大发展。1.1墙体材料品种越来越丰富,基本适应了建筑业的需求 相似文献
150.
光栅谐振子检测地震波的理论和方法研究 总被引:2,自引:0,他引:2
提出了一种新的检波理论和方法 ,它是一种实现检测地震波信号的地震勘探技术。采用光栅谐振子为敏感元件 ,将大地震动的机械信号转换成光调制信号—莫尔条纹 ,再用光电接收器件将其转换成数字化电信号输出。光栅谐振子检测地震波的装置能够直接将大地震动的机械信号转化为脉冲数字信号输出 ;并以记数的形式采样 ,避免了器件的精度不同对传感器输出的数据质量的影响 ,从而简化了组装工艺。文中阐述了该方法的工作原理、参数计算、测试方法和实验结果 相似文献