全文获取类型
收费全文 | 138544篇 |
免费 | 16472篇 |
国内免费 | 11723篇 |
专业分类
电工技术 | 12956篇 |
技术理论 | 2篇 |
综合类 | 14173篇 |
化学工业 | 16858篇 |
金属工艺 | 9415篇 |
机械仪表 | 9653篇 |
建筑科学 | 10131篇 |
矿业工程 | 5252篇 |
能源动力 | 3694篇 |
轻工业 | 13980篇 |
水利工程 | 4827篇 |
石油天然气 | 5218篇 |
武器工业 | 2099篇 |
无线电 | 16345篇 |
一般工业技术 | 12181篇 |
冶金工业 | 5572篇 |
原子能技术 | 2326篇 |
自动化技术 | 22057篇 |
出版年
2024年 | 846篇 |
2023年 | 2294篇 |
2022年 | 5307篇 |
2021年 | 7002篇 |
2020年 | 4955篇 |
2019年 | 3647篇 |
2018年 | 3971篇 |
2017年 | 4531篇 |
2016年 | 4102篇 |
2015年 | 6409篇 |
2014年 | 7930篇 |
2013年 | 9439篇 |
2012年 | 11576篇 |
2011年 | 12155篇 |
2010年 | 11451篇 |
2009年 | 10894篇 |
2008年 | 10723篇 |
2007年 | 10689篇 |
2006年 | 9394篇 |
2005年 | 7546篇 |
2004年 | 5555篇 |
2003年 | 3627篇 |
2002年 | 3458篇 |
2001年 | 2939篇 |
2000年 | 2310篇 |
1999年 | 1126篇 |
1998年 | 542篇 |
1997年 | 421篇 |
1996年 | 348篇 |
1995年 | 299篇 |
1994年 | 229篇 |
1993年 | 175篇 |
1992年 | 135篇 |
1991年 | 103篇 |
1990年 | 93篇 |
1989年 | 86篇 |
1988年 | 47篇 |
1987年 | 40篇 |
1986年 | 36篇 |
1985年 | 24篇 |
1984年 | 24篇 |
1983年 | 17篇 |
1982年 | 11篇 |
1981年 | 21篇 |
1980年 | 38篇 |
1979年 | 27篇 |
1977年 | 21篇 |
1976年 | 42篇 |
1959年 | 22篇 |
1951年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
The dye-sensitized TiO2 complex films were prepared by the dye coat onto TiO2 surfaces,and the sensitizing mechanism and adsorption properties of the dye-sensitized TiO2 complex films were inverstigated.The influence of the application conditions of dye adsorbed on TiO2 films on the amount of dye adsorption was discussed.Experimental results show that the concentration,the temperature of dye solutions and the dipping time of TiO2 films in the dye solutions have a significant influence on the amount of dye adsorption.Cell test indicates that the conversion efficiency of light to electricity increases with the amount of dye adsorption. 相似文献
43.
介绍了高可靠电镀Ni/Au工艺在PTFE微波印制电路上的应用,并分析了氨基磺酸盐镀软镍和亚硫酸盐镀软金工艺的影响因素及提高Ni/Au镀层之间附着力的措施。通过实验及应用证明了与直接镀金工艺相比,在软基材PTFE敷铜箔板上镀Ni/Au工艺能大大提高微波电路的可焊性,高温稳定性和长期可靠性,并且用其所制作的微波器件的高频性能也优于直接镀金工业。 相似文献
44.
HU Kasper G Haroske U Geissler W Meyer KD Kunze 《Canadian Metallurgical Quarterly》1997,19(6):482-488
OBJECTIVE: For approximately 15 years, malignancy-associated changes (MACs) have been consistently found by means of high-resolution cytometry in different tissues, especially in visually normal appearing cervical cells. Their biologic nature is not yet fully understood. The aim of this investigation was to assess the expression of MACs in cervical smears and to evaluate their prognostic relevance. STUDY DESIGN: This study was performed on normal intermediate cells obtained from 53 cytologically positive and 78 cytologically negative cervical smears. From a second sample, 31 cases showing negative cytology were selected for a prospective longitudinal study. Densitometric and texture features were generated, and MACs were described on the basis of multivariate discriminant analysis. RESULTS: Discrimination between positive and negative cases was possible, with a correct classification rate of approximately 80%. After a mean period of 29.5 months, we noted no statistically significant increase in the incidence of cervical intraepithelial neoplasia in the group of healthy but MAC-positive women as compared to those who were MAC negative. CONCLUSION: MACs were constantly expressed in the epithelium of the cervix. Although their prognostic relevance remains unclear, MACs play an important role in the effort to automate cervical cytology. 相似文献
45.
Capacity has always been a major concern in wireless networks. This letter studies the impact of mobility on the overall system capacity in wireless cellular networks. In this letter, we present a simple system model which we developed to capture the inherent relationships among system capacity, new call blocking probability, handoff dropping probability, call terminating probability, and bandwidth utilization rate. We investigate the complex relationship between mobility and capacity‐related parameters. Through simulation, we demonstrate that mobility has a significant impact on capacity and is reversely proportional to the bandwidth reserved for handoff traffic. 相似文献
46.
47.
48.
空调系统应用于普通房间可能引起空调病 ,应用于医院时此问题将更为突出 ,本文对此类建筑在空调系统设计中应重视的有关问题进行了初步探讨 相似文献
49.
50.