全文获取类型
收费全文 | 112497篇 |
免费 | 11705篇 |
国内免费 | 5810篇 |
专业分类
电工技术 | 13566篇 |
技术理论 | 5篇 |
综合类 | 7950篇 |
化学工业 | 18290篇 |
金属工艺 | 3241篇 |
机械仪表 | 4253篇 |
建筑科学 | 12245篇 |
矿业工程 | 7229篇 |
能源动力 | 7554篇 |
轻工业 | 6074篇 |
水利工程 | 2072篇 |
石油天然气 | 20203篇 |
武器工业 | 743篇 |
无线电 | 5228篇 |
一般工业技术 | 7105篇 |
冶金工业 | 5167篇 |
原子能技术 | 1535篇 |
自动化技术 | 7552篇 |
出版年
2024年 | 455篇 |
2023年 | 1558篇 |
2022年 | 3059篇 |
2021年 | 3937篇 |
2020年 | 4279篇 |
2019年 | 3584篇 |
2018年 | 3301篇 |
2017年 | 3689篇 |
2016年 | 4326篇 |
2015年 | 4355篇 |
2014年 | 7146篇 |
2013年 | 7221篇 |
2012年 | 8448篇 |
2011年 | 8751篇 |
2010年 | 6126篇 |
2009年 | 6332篇 |
2008年 | 5606篇 |
2007年 | 6705篇 |
2006年 | 6714篇 |
2005年 | 5503篇 |
2004年 | 4767篇 |
2003年 | 4125篇 |
2002年 | 3489篇 |
2001年 | 3014篇 |
2000年 | 2628篇 |
1999年 | 2110篇 |
1998年 | 1665篇 |
1997年 | 1360篇 |
1996年 | 1082篇 |
1995年 | 940篇 |
1994年 | 837篇 |
1993年 | 578篇 |
1992年 | 467篇 |
1991年 | 389篇 |
1990年 | 331篇 |
1989年 | 294篇 |
1988年 | 160篇 |
1987年 | 118篇 |
1986年 | 100篇 |
1985年 | 88篇 |
1984年 | 70篇 |
1983年 | 47篇 |
1982年 | 47篇 |
1981年 | 68篇 |
1980年 | 50篇 |
1979年 | 14篇 |
1977年 | 9篇 |
1976年 | 7篇 |
1959年 | 10篇 |
1951年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
采用X射线衍射分析技术,研究了脉冲化学镀非晶态Ni-P合金的原子分布和函数,得出其短程有序原子集团的尺度为0.754nm,约为熔体激冷法获得的非晶态Ni-P合金短程有序畴的1/2。并利用脉冲化学沉积非晶态合金的微机制择这一结果进行了解释。 相似文献
42.
聚碳硅烷的分子量分布与可纺性研究 总被引:6,自引:1,他引:5
阐述了聚碳烷的合成及其分子量分布,讨论了高低分子含量对聚碳硅烷熔点及可纺性的影响,而且提出了分子量分布的控制标准与方法。 相似文献
43.
含聚二甲基硅氧烷的聚醚聚氨酯膜透气性及表面性质研究 总被引:2,自引:0,他引:2
以聚二甲基硅氧烷(PDMS)/聚四氢呋喃(PTMO)为软段,4,4'-二环己基甲烷二异氰酸酯(HMDI)为硬段(丁二醇BD为扩链剂)制成的多相嵌段共聚物作为基质材料,进行了气体(O2和N2)透过性试验,同时对膜材料进行了ESCA表面分析。结果表明,共聚物膜的透气性能取决于材料中连续相组分,随着软段中PDMS含量的改变而变化。当PDMS含量较高时,共聚物膜显示出PDMS均聚物的特性,具有较高的气体秀 相似文献
44.
In order to cumpare the peformance of different supply diffuers of ventilation air, the airflow passern, temperature stratifiation and contaminant dispersion in a furnitured office ventilated by three kinds of air diffuer were numerically investigated. The air diffuers studied in this paper are a quarter-cylinder displacement diffuer on the floor and mixing diffuers (linear and vortex diffuers) on the ceiling. The heat sources in the of-fice are considered to be 50% convective and 50% radiative. The k-? two-equatwn model of turbulence is employed to predict the turbulent diffusion. The results show that the displacement diffuser provides a rather uniform flow field with low velocify in most areas, and the vertical temperature difference from floor to ceiling is as high as 6 K. With the linear diffuser, the air velociry is high, and the temperature is uniform both horizontally and vertically. The air velocity generated by the vortex diffuser is moderate. The distributions of the temperature and the contaminant are rather uniform. 相似文献
45.
The causes of lightning outage are subdivided into direct lightning strokes and induced lightning strokes, which are identified by the characteristics of the lightning overvoltage. In the past, lightning protection devices were directed mainly toward the latter, and attention has been focused on the installation of lightning protection devices, ground wires, and reinforcement of insulators. However, lightning outages continue to occur. Thus it is extremely important to clarify the fault characteristics of lightning surges and to study the effectiveness of various lightning protection devices by considering both direct lightning stroke and induced lightning stroke in order to prevent lightning outage in the future. In this research, the electromagnetic transients program (EMTP) has been applied to the direct lightning stroke, and the induced lightning outage analysis program for multiple conductor systems has been applied to the induced lightning stroke to study the effectiveness of lightning protection devices provided by combination of various lightning protection devices. The most effective lightning protection schemes are analyzed and evaluated based on verification tests on the full scale models as well as economic considerations. 相似文献
46.
Motoharu Fujigaki In Hong Yang Yoshiharu Morimoto Eung Kyo Han 《NDT & E International》1996,29(4):197-203
There is no good method to measure the shape and the strain distributions of a structure changing with time. We have previously proposed the Fourier transform grid method (FTGM) to measure the three-dimensional shape and surface strain distributions of stationary objects by analysing the two-dimensional grating images recorded with two cameras. In the stereoscopic method, it is very important to determine the accurate geometric parameters of the camera system. In this paper, the positions and the directions of cameras are accurately determined using the FTGM applied to images of a reference object on which a two-dimensional grating is drawn. Applications for analysing shape and strain distributions of vibrating rubber plates and a moving human skin are shown. 相似文献
47.
48.
This paper highlights the possibility of inverse gas chromatography for the surface characterization of common fillers (CaCO3, talc, SiO2,) for paints and coatings. Divided solids are described, on the one hand, by the dispersive component of their surface energy and, on the other, by a specific parameter indicating their acid-base interaction potential. The role of the surface morphology at a molecular level is also examined. It is demonstrated that steric effects play an important role in the adsorption of probes on lamellar solids like talc. The consequences of surface treatments as well as examples of practical applications are also reported. 相似文献
49.
50.
清代皇家园林规划设计控制的量化研究——以圆明三园、清漪园为例 总被引:1,自引:0,他引:1
本文通过量化分析探索了清代皇家园林规划设计的控制规律及相关理论。 相似文献