全文获取类型
收费全文 | 13867篇 |
免费 | 1277篇 |
国内免费 | 611篇 |
专业分类
电工技术 | 800篇 |
技术理论 | 1篇 |
综合类 | 1050篇 |
化学工业 | 2329篇 |
金属工艺 | 843篇 |
机械仪表 | 822篇 |
建筑科学 | 1150篇 |
矿业工程 | 414篇 |
能源动力 | 548篇 |
轻工业 | 867篇 |
水利工程 | 267篇 |
石油天然气 | 721篇 |
武器工业 | 116篇 |
无线电 | 1557篇 |
一般工业技术 | 1708篇 |
冶金工业 | 621篇 |
原子能技术 | 151篇 |
自动化技术 | 1790篇 |
出版年
2024年 | 59篇 |
2023年 | 280篇 |
2022年 | 437篇 |
2021年 | 574篇 |
2020年 | 489篇 |
2019年 | 375篇 |
2018年 | 418篇 |
2017年 | 443篇 |
2016年 | 443篇 |
2015年 | 548篇 |
2014年 | 663篇 |
2013年 | 763篇 |
2012年 | 863篇 |
2011年 | 882篇 |
2010年 | 771篇 |
2009年 | 737篇 |
2008年 | 671篇 |
2007年 | 615篇 |
2006年 | 614篇 |
2005年 | 528篇 |
2004年 | 432篇 |
2003年 | 526篇 |
2002年 | 635篇 |
2001年 | 552篇 |
2000年 | 434篇 |
1999年 | 363篇 |
1998年 | 277篇 |
1997年 | 264篇 |
1996年 | 237篇 |
1995年 | 178篇 |
1994年 | 147篇 |
1993年 | 116篇 |
1992年 | 85篇 |
1991年 | 74篇 |
1990年 | 62篇 |
1989年 | 36篇 |
1988年 | 48篇 |
1987年 | 26篇 |
1986年 | 20篇 |
1985年 | 22篇 |
1984年 | 8篇 |
1983年 | 8篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1974年 | 1篇 |
1961年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
We consider quantile regression models and investigate the induced smoothing method for obtaining the covariance matrix of the regression parameter estimates. We show that the difference between the smoothed and unsmoothed estimating functions in quantile regression is negligible. The detailed and simple computational algorithms for calculating the asymptotic covariance are provided. Intensive simulation studies indicate that the proposed method performs very well. We also illustrate the algorithm by analyzing the rainfall-runoff data from Murray Upland, Australia. 相似文献
992.
Huifeng Jiang Xuedong Chen Zhichao Fan Jie Dong Heng Jiang Shouxiang Lu 《Materials Science and Engineering: A》2009,500(1-2):98-103
Stress controlled creep-fatigue tests were carried out for hot rolled and dynamic strain aging pre-treated 316L stainless steel different loading levels at 550 °C. For both pre-treatment state materials, dynamic strain aging was found to manifest itself macroscopically as displacement or mean strain abrupt jumps during cyclic deformation. Comparing with hot rolled material, by DSA pre-treatment, the creep-fatigue cyclic strain amplitude is decreased, the cycle at the 1st abrupt displacement jump is postponed and the material creep-fatigue life is effectively prolonged. Moreover, it is found that, the material creep-fatigue life monotonically increases with pre-deformation strain, no matter the maximum pre-deformation stress is larger than the maximum creep-fatigue applied stress or not. 相似文献
993.
Dandan Lu Qilin Cao Xiaomin Li Xiuju Cao Fang Luo Wenjing Shao 《Hydrometallurgy》2009,95(1-2):145-152
A series of orange peel cellulose biosorbents has been specifically prepared by different chemical modifications to understand the mechanism of copper adsorption from chloride solutions. The different biosorbents and raw orange peels were characterized using elemental analysis and Fourier transform infrared spectroscopy (FTIR). The acidic and basic sites and pH of zero charge were also determined. The influences of pH, contact time, initial copper concentration and solid/liquid ratio on copper removal were examined. The maximum adsorption capacity of copper was 1.22 mol/kg, using orange peel esterified by 0.6 mol/L citric acid at 80 °C after 0.1 mol/L NaOH saponification. A comparison of different isotherm models revealed that the combination of Langmuir and Freundlich (L–F) isotherm model fitted the experimental data best. Results indicate that the chemically modified orange peel cellulose can provide an efficient and cost-effective technology for eliminating copper from aqueous solution. 相似文献
994.
陈绍 《现代制造技术与装备》2009,(2)
采用ADAMS/Hydraulics仿真平台对某型车辆阀控转向液压系统进行建模与仿真,通过对仿真步长及仿真时间的设置和调整,精确地观察仿真曲线变化规律,对油缸运行速度、系统压力及阻尼等进行了分析和优化. 相似文献
995.
Traditionally, process planning and scheduling for parts were carried out in a sequential way, where scheduling was done after process plans had been generated. Considering the fact that the two functions are usually complementary, it is necessary to integrate them more tightly so that performance of a manufacturing system can be improved greatly. In this paper, a new integration model and a modified genetic algorithm-based approach have been developed to facilitate the integration and optimization of the two functions. In the model, process planning and scheduling functions are carried out simultaneously. In order to improve the optimized performance of the modified genetic algorithm-based approach, more efficient genetic representations and operator schemes have been developed. Experimental studies have been conducted and the comparisons have been made between this approach and others to indicate the superiority and adaptability of this method. The experimental results show that the proposed approach is a promising and very effective method for the integration of process planning and scheduling. 相似文献
996.
建筑施工企业为在建筑市场占据更多份额 ,必需从质量、成本、工期等各方面提高自身竞争能力 ,而企业资源规划理念和网络科技、电子商务的结合 ,提供了一条在施工过程过程中动态地对企业和力、设备、资金、技术、信息等各个方面 (统称为资源 )作出合理配置、储存、调拨及运用 ,从而最大限度地降低成本、提高效率的有效途径。简要介绍了其相应软件开发的主要目标和基本内容。 相似文献
997.
数据挖掘技术在CRM中的应用 总被引:1,自引:0,他引:1
利用数据挖掘可以帮助完成日益繁重的潜在客户群的划分,从而实现对获取新客户成本的有效管理,可以明显提高营销活动的响应率,改善营销活动的回报率。在分析数据挖掘应用于客户关系管理的必要性和应用方式的基础上,对面向数据挖掘的通信企业客户关系管理系统和数据挖掘在其中的具体应用进行了研究。 相似文献
998.
999.
1000.
unit-gain compensation ceil and pseudo-ESR (equivalent serial resistor of load capacitor) power stage have been realized by this controllable resistor.Their advantages and limitations are discussed and verified by simulation results. 相似文献