全文获取类型
收费全文 | 1900篇 |
免费 | 123篇 |
国内免费 | 108篇 |
专业分类
电工技术 | 36篇 |
综合类 | 389篇 |
化学工业 | 98篇 |
金属工艺 | 105篇 |
机械仪表 | 97篇 |
建筑科学 | 164篇 |
矿业工程 | 51篇 |
能源动力 | 45篇 |
轻工业 | 115篇 |
水利工程 | 22篇 |
石油天然气 | 307篇 |
武器工业 | 2篇 |
无线电 | 31篇 |
一般工业技术 | 125篇 |
冶金工业 | 148篇 |
原子能技术 | 1篇 |
自动化技术 | 395篇 |
出版年
2024年 | 7篇 |
2023年 | 14篇 |
2022年 | 34篇 |
2021年 | 32篇 |
2020年 | 31篇 |
2019年 | 41篇 |
2018年 | 36篇 |
2017年 | 47篇 |
2016年 | 35篇 |
2015年 | 36篇 |
2014年 | 86篇 |
2013年 | 100篇 |
2012年 | 92篇 |
2011年 | 87篇 |
2010年 | 95篇 |
2009年 | 81篇 |
2008年 | 96篇 |
2007年 | 167篇 |
2006年 | 154篇 |
2005年 | 145篇 |
2004年 | 131篇 |
2003年 | 116篇 |
2002年 | 113篇 |
2001年 | 108篇 |
2000年 | 67篇 |
1999年 | 43篇 |
1998年 | 34篇 |
1997年 | 22篇 |
1996年 | 23篇 |
1995年 | 16篇 |
1994年 | 12篇 |
1993年 | 8篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1982年 | 2篇 |
排序方式: 共有2131条查询结果,搜索用时 15 毫秒
991.
基于GT400运动控制器的开放式体系结构的数控系统软硬件平台及其关键技术,研究陶瓷零件快速成型设备数控系统对于缩短陶瓷零件的制造周期以及提高企业的生产效率所具有的重要意义.阐述了陶瓷零件快速成型机的新工艺方法和特点,对新型陶瓷零件快速成型机机械系统及其控制要求作了详细分析,着重介绍了陶瓷零件快速成型机控制系统的硬件设计及自顶向下的软件设计.利用Visual C++6.0开发工具和GT系列运动控制器自带的DLL动态链接库开发了操作方便、运行稳定、加工精度高的开放式陶瓷快速成型装置数控系统.控制系统能够很好地满足系统开放性的要求及产品自动化生产的要求,提高了经济效益. 相似文献
992.
基于备件缺货率的多级库存优化研究 总被引:1,自引:0,他引:1
部队备件管理库存问题,是一个十分重要和复杂的问题。从供应链的角度出发对部队的备件库存管理进行了探讨和论述,分析了部队备件库存管理的特点。在此基础上,考虑到实际情况中部队仓库库址分散,通过分析备件在补货过程中发生的各种相关费用和备件缺货率,建立了以一个补货周期内供应链的补货总成本最小为优化目标的补货模型,并给出求解方法。 相似文献
993.
Phillip A. Cartwright 《时间序列分析杂志》1985,6(4):203-211
Abstract. Performance of the state dependent model developed by Priestley is evaluated relative to that of bilinear and standard linear models using two well-known time series. The results indicate the use of broader classes of time series models beyond the conventional ARMA class is likely to lead to significant reductions in forecasting error. However, there are difficult problems relating to the identification of the order of the model, estimation of the parameters, and determination of the correct nonlinear model. 相似文献
994.
A model is developed that simulates nationwide energy consumption of the residential sector by considering the diversity of household and building types. Since this model can simulate the energy consumption for each household and building category by dynamic energy use based on the schedule of the occupants’ activities and a heating and cooling load calculation model, various kinds of energy-saving policies can be evaluated with considerable accuracy. In addition, the average energy efficiency of major electric appliances used in the residential sector and the percentages of housing insulation levels of existing houses is predicted by the “stock transition model.” In this paper, energy consumption and CO2 emissions in the Japanese residential sector until 2025 are predicted. For example, as a business – as-usual (BAU) case, CO2 emissions will be reduced by 7% from the 1990 level. Also evaluated are mitigation measures such as the energy efficiency standard for home electric appliances, thermal insulation code, reduction of standby power, high-efficiency water heaters, energy-efficient behavior of occupants, and dissemination of photovoltaic panels. 相似文献
995.
The aim of this paper is to analyse the profitability of energy-efficient retrofit investments in the Swiss residential building sector from the house owner's perspective. Different energy price expectations, policy instruments such as subsidies, income tax deduction and a carbon tax, as well as potential future cost degression of energy efficiency measures were taken into account. The discounted cash flow method was used for the investment analysis of different retrofit packages applied to a model building scheduled for renovation, i.e. a single-family house constructed between 1948 and 1975. The results show that present Swiss policy instruments push investments for energy-efficient retrofitting to profitability. Cost degression has a minor significance for investment profitability. However, the most relevant factor for the investment analysis is the expected energy price. Expecting a future fuel oil price at the level of 2005, efficiency investments are close to profitability even without policy support. If higher energy prices were expected, energy-efficient retrofitting would be an attractive investment opportunity. 相似文献
996.
阐述了铁道机车车辆轮轨摩擦磨损的现状;研究了内燃机车车轮、闸瓦和钢轨的消耗数量及相应的维修费用;指出了采用适当的新技术之后,在节能降耗方面会产生显著的经济效益。 相似文献
997.
基于SVM(支持向量机)的SVDD(支持向量数据描述)分类算法存在计算复杂、分类准确率较低的缺陷, 针对股票数据非线性、高噪声的特点, 在传统的SVDD分类算法基础上, 模糊核超球快速分类算法(FCABFKH)通过合并法寻找超球集, 并依据最大隶属度原则构建分类器, 排除了离群点和超球集的重叠问题, 同时避免了复杂的二次规划, 具有分类速度快, 分类结果准确率高的特点。采用中国沪市上市公司数据验证该方法的有效性, 实验结果表明, 运用FCABFKH算法得到的组合回报率超过了市场基准。 相似文献
998.
针对腈纶原液变频系统,提出了基于多智能体的分布递阶控制模型,实现了原液生产过程自动化系统中控制一维护一管理的集成。系统地分析了各智能体的功能、实现方法及多智能体之间的协作关系。利用现场总线技术保证智能体之间稳定可靠通讯连接。该方法可靠性强,适应性好。很容易推广到其他复杂自动化系统中。 相似文献
999.
Xiaoping Wu Bernt Guldbrandtsen Ulrik Sander Nielsen Mogens Sandø Lund Goutam Sahana 《Journal of dairy science》2017,100(8):6356-6370
Identification of the genetic variants associated with calf survival in dairy cattle will aid in the elimination of harmful mutations from the cattle population and the reduction of calf and young stock mortality rates. We used de-regressed estimated breeding values for the young stock survival (YSS) index as response variables in a genome-wide association study with imputed whole-genome sequence variants. A total of 4,610 bulls with estimated breeding values were genotyped with the Illumina BovineSNP50 (Illumina, San Diego, CA) single nucleotide polymorphism (SNP) genotyping array. Genotypes were imputed to whole-genome sequence variants. After quality control, 15,419,550 SNP on 29 Bos taurus autosomes (BTA) were used for association analysis. A modified mixed-model association analysis was used for a genome scan, followed by a linear mixed-model analysis for selected genetic variants. We identified 498 SNP on BTA5 and BTA18 that were associated with the YSS index in Nordic Holstein. The SNP rs440345507 (Chr5:94721790) on BTA5 was the putative causal mutation affecting YSS. Two haplotype-based models were used to identify haplotypes with the largest detrimental effects on YSS index. For each association signal, 1 haplotype region with harmful effects and the lead associated SNP were identified. Detected haplotypes on BTA5 and BTA18 explained 1.16 and 1.20%, respectively, of genetic variance for the YSS index. We examined whether YSS quantitative trait loci (QTL) on BTA5 and BTA18 were associated with stillbirth. YSS QTL on BTA18 overlapped a QTL region for stillbirth, but most likely 2 different causal variants were responsible for these 2 QTL. Four component traits of the YSS index, defined by sex and age, were analyzed separately by the modified mixed-model approach. The same genomic regions were associated with both bull and heifer calf mortality. Several genes (EPS8, LOC100138951, and KLK family genes) contained a lead associated SNP or were included in haplotypes with large detrimental effects on YSS in Nordic Holstein cattle. 相似文献
1000.
研究了对配浆过程实施计算机控制的优化控制方案,力图做到不同工况下配比优化、控制到位,从而保证正常生产、稳定成浆质量、节约造纸原料并减小对后续工段的影响 相似文献