全文获取类型
收费全文 | 105660篇 |
免费 | 12752篇 |
国内免费 | 8931篇 |
专业分类
电工技术 | 9421篇 |
综合类 | 11429篇 |
化学工业 | 12768篇 |
金属工艺 | 7398篇 |
机械仪表 | 7076篇 |
建筑科学 | 7289篇 |
矿业工程 | 3799篇 |
能源动力 | 2518篇 |
轻工业 | 12560篇 |
水利工程 | 3916篇 |
石油天然气 | 3276篇 |
武器工业 | 1492篇 |
无线电 | 11712篇 |
一般工业技术 | 9240篇 |
冶金工业 | 4423篇 |
原子能技术 | 1795篇 |
自动化技术 | 17231篇 |
出版年
2024年 | 665篇 |
2023年 | 1769篇 |
2022年 | 4213篇 |
2021年 | 5245篇 |
2020年 | 3770篇 |
2019年 | 2791篇 |
2018年 | 2965篇 |
2017年 | 3466篇 |
2016年 | 3068篇 |
2015年 | 4830篇 |
2014年 | 5918篇 |
2013年 | 7145篇 |
2012年 | 8698篇 |
2011年 | 9334篇 |
2010年 | 8763篇 |
2009年 | 8341篇 |
2008年 | 8346篇 |
2007年 | 8292篇 |
2006年 | 7233篇 |
2005年 | 5906篇 |
2004年 | 4337篇 |
2003年 | 2740篇 |
2002年 | 2545篇 |
2001年 | 2272篇 |
2000年 | 1834篇 |
1999年 | 801篇 |
1998年 | 348篇 |
1997年 | 260篇 |
1996年 | 200篇 |
1995年 | 155篇 |
1994年 | 140篇 |
1993年 | 141篇 |
1992年 | 102篇 |
1991年 | 71篇 |
1990年 | 79篇 |
1989年 | 71篇 |
1988年 | 45篇 |
1987年 | 47篇 |
1986年 | 42篇 |
1985年 | 28篇 |
1984年 | 33篇 |
1983年 | 26篇 |
1982年 | 17篇 |
1981年 | 21篇 |
1980年 | 44篇 |
1979年 | 29篇 |
1977年 | 22篇 |
1976年 | 31篇 |
1959年 | 17篇 |
1951年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
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
102.
Dan C. DeBorde William W. Woessner Bruce Lauerman Patrick Ball 《Water research》1998,32(12):3781-3785
At the present time, somatic and male-specific coliphage and human enterovirus groups are being considered as indicators of possible pathogenic human enteric virus contamination from fecal contamination. A primary attribute for any indicator of fecal contamination is its prevalence at the source and in associated ground water. It must be consistently found in the source material at concentrations that are measurable with available techniques. Over a period of ten months, male-specific and somatic coliphage ranged from 7000 to 4,000,000 PFU/L in the effluent from a multi-user septic-tank. Unlike the values determined for septic-tank effluent, coliphage concentrations measured in ground water over this same period only varied by five-fold. Coliphage concentration in ground water under the down-gradient edge of the drainfield contained 1000 PFU/L. This concentration decreased at −1 log10/5 m during 17.4 m of ground-water transport. From these data, coliphage concentrations in septic-tank effluent seem sufficient to allow their use as indicators of fecal contamination in ground water. 相似文献
103.
介绍汽车加油站在防火设计与消防管理方面需注意的问题,主要包括站址选择、总平面布置、油罐设置、管线布置、卸油方式等方面,同时对加油站的日常操作与防火消防管理提出了要求。 相似文献
104.
Since electronic switching systems usually require very strict reliability requirements as well as good performance objectives, we need to jointly analyse the performance and reliability of switching systems. In this paper, we compare conventional time–space–time switches with single space switches with those with multiple separated space switches, from the viewpoints of reliability and performance. We consider time–space–time switching networks which consist of N incoming time switches, i.e. one NxN space switch, two (N/2)x(N/2) space switches, and four (N/4)x(N/4) space switches. We introduce a Markov reliability model to study the effect of failures and analyse the reliability and performance of three different types of switching networks in terms of average blocking probability and the mean time to unreliable operation, as we vary the offered traffic. As a result, T–S–T switching networks with multiple separated space switches exhibit better performance and reliability than those with single space switches. 相似文献
105.
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
106.
基于空间矩的灰度边缘亚像元度量精度分析 总被引:7,自引:0,他引:7
灰度图像中边缘定位受采样密度限制,亚像元精度度量方法在需要高精度的应用中受到重视,要想知识到底需要多高的分辨率才能达到定精度指标,就有必要分析特征定位方法的最坏情况的精度,文中用分析和实验的方法给出了基于空间矩的边缘定位方法,对于边缘点,边缘直线以及直边缘区域的最坏情况定位精度分析。分析和讨论的结果不但可以用来确定已知形状位置估计的最大误差,而且还可用于对准的形状几何参数,以获得较高的精度。 相似文献
107.
108.
109.
钢纤维混凝土在南钢大道工程中的应用 总被引:1,自引:0,他引:1
钢纤维混凝土是一种性能优良的新型复合材料,与普通混凝土相比,其抗拉、抗弯、抗裂及耐磨、耐冲击、耐疲劳等性能都有显著提高,它不仅可使路面厚度减薄,工程缝间距加大,改善路面的使用性能,延长路面使用寿命,而且还可节省工程造价,缩短施工工期。文中结合南钢大道路面工程实际,主要介绍了钢纤维混凝土的施工及质量控制要点。 相似文献
110.