全文获取类型
收费全文 | 106700篇 |
免费 | 7459篇 |
国内免费 | 3218篇 |
专业分类
电工技术 | 4576篇 |
技术理论 | 4篇 |
综合类 | 4380篇 |
化学工业 | 19595篇 |
金属工艺 | 5428篇 |
机械仪表 | 7044篇 |
建筑科学 | 5612篇 |
矿业工程 | 1337篇 |
能源动力 | 3677篇 |
轻工业 | 7929篇 |
水利工程 | 1455篇 |
石油天然气 | 2728篇 |
武器工业 | 486篇 |
无线电 | 14927篇 |
一般工业技术 | 17586篇 |
冶金工业 | 6257篇 |
原子能技术 | 1384篇 |
自动化技术 | 12972篇 |
出版年
2024年 | 283篇 |
2023年 | 1375篇 |
2022年 | 2477篇 |
2021年 | 3698篇 |
2020年 | 2680篇 |
2019年 | 2567篇 |
2018年 | 2918篇 |
2017年 | 3089篇 |
2016年 | 3427篇 |
2015年 | 3603篇 |
2014年 | 4885篇 |
2013年 | 6411篇 |
2012年 | 6898篇 |
2011年 | 7922篇 |
2010年 | 6491篇 |
2009年 | 6324篇 |
2008年 | 6199篇 |
2007年 | 5375篇 |
2006年 | 5225篇 |
2005年 | 4494篇 |
2004年 | 3598篇 |
2003年 | 3454篇 |
2002年 | 3552篇 |
2001年 | 2981篇 |
2000年 | 2488篇 |
1999年 | 2211篇 |
1998年 | 2600篇 |
1997年 | 1852篇 |
1996年 | 1595篇 |
1995年 | 1244篇 |
1994年 | 1045篇 |
1993年 | 850篇 |
1992年 | 614篇 |
1991年 | 537篇 |
1990年 | 449篇 |
1989年 | 387篇 |
1988年 | 333篇 |
1987年 | 244篇 |
1986年 | 177篇 |
1985年 | 152篇 |
1984年 | 121篇 |
1983年 | 77篇 |
1982年 | 62篇 |
1981年 | 60篇 |
1980年 | 46篇 |
1979年 | 39篇 |
1978年 | 31篇 |
1977年 | 38篇 |
1976年 | 69篇 |
1975年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
121.
报道了鄂尔多斯盆地低压低渗气藏水平使用的事生物降解钻(完)井液ASS-1的组成和性能.其组分包括粒度适宜的碳酸钙粉(暂堵剂和加重剂),改性淀粉(可变形暂堵剂和降滤失剂),优质生物聚的(提黏切剂),pH调节剂,无荧光润滑剂DRH(加量1%)及防腐剂等,给出了基础配方.该钻(完)井液对岩心的伤害率约为5%(4种其他体系钻(完)井液的伤害率在21.9%~96.6%);经高压气体反向驱排后,伤害后岩心渗透率恢复率可由88%提高到92%;在≤110℃热滚16 h后黏度损失率<50%;经过4次热滚(91℃×16 h),每次热滚后作适当维护处理,均可使变坏的性能恢复到要求值.该钻(完)井液用于水平段长800 m、地温83℃的DP35-1井和两分支水平段长各1500 m、地温91℃的CB1-1中,根据技术要求采用适当技术措施,在钻进中特别是CB1-1井长达4个月的钻进中,API滤失量<5 mL,密度1.04~1.07 g/cm3,漏斗黏度41~53 s,塑性黏度10~15 mPa·s,屈服值6~18 Pa,两口井均顺利完钻且可裸眼完井.图5表4参2. 相似文献
122.
This paper explains the manufacturing process of a composite train carbody with a sandwich composite structure for bodyshell and a stainless steel structure for the under frame. In addition, the structural behavior and safety of the composite carbody of the Korean tilting train was investigated by the static load tests. From the test results, the stiffness of the composite carbody met the specified design. In the aspect of strength, the maximum stress of the composite bodyshell was of 12.2% of strength of CF1263 carbon/epoxy. 相似文献
123.
Sweetman Kim 《中国电子商情》2008,(12)
汽车负载突降保护的重要性
今天,汽车中并联在供电线路上的许多电子控制器和设备与三、四十年前生产的汽车有了很大的不同。那时汽车中的唯一的电子设备就是汽车收音机。 相似文献
124.
Do Hoon Kim Umme Farva Woo Sik Jung Eui Jung Kim Chinho Park 《Korean Journal of Chemical Engineering》2008,25(5):1184-1189
This paper reports an alternative method for the growth of GaN epitaxial layer on (0001) Al2O3 substrate by hot-wall vapor phase epitaxy technique. Tris (N,N-dimethyldithiocarbamato)-gallium (III), Ga(mDTC)3 was introduced as a precursor material for the seed layer formation in the growth of GaN. Optimal growth conditions with
seed layers formed by the Ga(mDTC)3 concentration of 0.047 mol/L were identified: Growth temperature was found to be 850 °C, and optimal distance between the
reactant outlet and substrate was determined to be 12.5 cm. Characterization results showed that this growth method produce
high-crystallinity GaN epitaxial layers at a relatively lower growth temperature compared to the existing growth techniques
and simplify the growth process. 相似文献
125.
GeoFilter: Geometric Selection of Mesh Filter Parameters 总被引:1,自引:0,他引:1
126.
127.
128.
许进 《西安电子科技大学学报(自然科学版)》1994,(3)
文中解决了2-重自补图的计数问题,获得了具有p个顶点的2-重自补图的数目是其中Z(A)表示置换群A的圈指标,S ̄(2)_p表示p次对称群的对群. 相似文献
129.
The purpose of this study was to analyze the symbolization of colors as cultural codes, based on costume colors. In order to study the significance of colors in cultural changes, we carried out a quantitative analysis and interpreted it from the perspective of cultural semiotics. The range of this study was focused on Korean costume colors, over diverse diachronic stages of Korean culture. For this study 1535 color samples were collected, measured with a spectrophotometer, and analyzed quantitatively according their diachronic stages of origin. As a result, red, blue, and yellow were found to be the most frequently used colors during the Chosun Dynasty, a period based on Confucianism. These colors acted as cultural codes with cultural significance. During the Modern times pink, light blue, and black increased in frequency and represented the reception of western culture, the changing sex role of women in society, and utilitarianism. In these days, neutral colors and grayish tones of all colors are the most significant colors of high frequency. The use of such colors is closely related to industrialization, mechanization, functionalism, and the changes of women's sex roles in the societies. They are used as cultural codes, especially to emphasize a rational and masculine image rather than a feminine image. © 2006 Wiley Periodicals, Inc. Col Res Appl, 32, 71–79, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20290 相似文献
130.
There are two main causes of inaccuracies in estimating image flows using gradient based techniques. One is the erroneous measurement of gradients in brightness and the other is the blurring of motion boundaries which is caused by the smoothness constraint. In the Letter, the gradient measurement error of conventional methods is analysed and a new technique based on this analysis proposed.<> 相似文献