全文获取类型
收费全文 | 24813篇 |
免费 | 3451篇 |
国内免费 | 2480篇 |
学科分类
工业技术 | 30744篇 |
出版年
2024年 | 92篇 |
2023年 | 521篇 |
2022年 | 836篇 |
2021年 | 1008篇 |
2020年 | 1026篇 |
2019年 | 836篇 |
2018年 | 753篇 |
2017年 | 1015篇 |
2016年 | 1091篇 |
2015年 | 1283篇 |
2014年 | 1969篇 |
2013年 | 1791篇 |
2012年 | 2026篇 |
2011年 | 2070篇 |
2010年 | 1644篇 |
2009年 | 1664篇 |
2008年 | 1677篇 |
2007年 | 1699篇 |
2006年 | 1544篇 |
2005年 | 1258篇 |
2004年 | 1014篇 |
2003年 | 840篇 |
2002年 | 678篇 |
2001年 | 559篇 |
2000年 | 459篇 |
1999年 | 266篇 |
1998年 | 202篇 |
1997年 | 159篇 |
1996年 | 126篇 |
1995年 | 123篇 |
1994年 | 94篇 |
1993年 | 70篇 |
1992年 | 56篇 |
1991年 | 45篇 |
1990年 | 34篇 |
1989年 | 39篇 |
1988年 | 23篇 |
1987年 | 15篇 |
1986年 | 14篇 |
1985年 | 11篇 |
1984年 | 9篇 |
1983年 | 13篇 |
1982年 | 18篇 |
1981年 | 13篇 |
1980年 | 12篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1975年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
互联网通讯采取标准化模式主要以TCP/IP协议为载体,通讯的优越特性体现在同时具备便捷性与开放性,为办公提供很大的便利,但基于网络系统也会入侵病毒、也会给信息数据与办公体系安全性造成威胁,直接影响企业综合稳定发展。据此,为保障办公工作的顺利开展,本文对计算机网络办公自动化及安全策略进行详细分析。 相似文献
2.
Against the background of smart manufacturing and Industry 4.0, how to achieve real-time scheduling has become a problem to be solved. In this regard, automatic design for shop scheduling based on hyper-heuristics has been widely studied, and a number of reviews and scheduling algorithms have been presented. Few studies, however, have specifically discussed the technical points involved in algorithm development. This study, therefore, constructs a general framework for automatic design for shop scheduling strategies based on hyper-heuristics, and various state-of-the-art technical points in the development process are summarized. First, we summarize the existing types of shop scheduling strategies and classify them using a new classification method. Second, we summarize an automatic design algorithm for shop scheduling. Then, we investigate surrogate-assisted methods that are popular in the current algorithm field. Finally, current problems and challenges are discussed, and potential directions for future research are proposed. 相似文献
3.
4.
伴随着我国社会经济的稳固发展,人们的生活质量逐渐有了明显改善,而在生态问题趋于严重使人们的环境保护意识显著提高的过程中,森林抚育对于森林生态系统的作用和价值愈发凸显。对此,文章针对森林抚育,从提高森林利用率、维持森林动植物生态平衡、增加可利用水资源等多个方面就其对森林生态系统的影响进行了分析,旨在给予相关森林保护工作者可行的帮助,并以此促进我国森林开发工作的可持续发展。 相似文献
5.
6.
为了更加准确地检测出图像中的显著性目标,提出了多先验融合的显著性目标检测算法。针对传统中心先验对偏离图像中心的显著性目标会出现检测失效的情况,提出在多颜色空间下求显著性目标的最小凸包交集来确定目标的大致位置,以凸包区域中心计算中心先验。同时通过融合策略将凸包区域中心先验、颜色对比先验和背景先验融合并集成到特征矩阵中。最后通过低秩矩阵恢复模型生成结果显著图。在公开数据集MSRA1000和ESSCD上的仿真实验结果表明,MPLRR能够得到清晰高亮的显著性目标视觉效果图,同时F,AUC,MAE等评价指标也比现有的许多方法有明显提升。 相似文献
7.
8.
9.
《International Journal of Hydrogen Energy》2020,45(38):19720-19732
The need to reduce PEMFC systems cost as well as to increase their durability is crucial for their integration in various applications and especially for transport applications. A new simplified architecture of the anode circuit called Alternating Fuel Feeding (AFF) offers to reduce the development costs. Requiring a new stack concept, it combines the simplicity of Dead-End Anode (DEA) with the operation advantages of the hydrogen recirculation. The three architectures (DEA, recirculation and AFF) are compared in terms of performance on a 5-kW test bench in automotive conditions, through a sensitivity analysis. A gain of 17% on the system efficiency is observed when switching from DEA to AFF. Moreover, similar performances are obtained both for AFF and for recirculation after an accurate optimization of the AFF tuning parameters. Based on DoE data, a gain of 25% on the weight of the anodic line has been identified compared to pulsed ejector architecture and 43% with the classic recirculation architecture with blower only (Miraï). 相似文献
10.
In this article we illustrate a methodology for building cross-language search engine. A synergistic approach between thesaurus-based approach and corpus-based approach is proposed. First, a bilingual ontology thesaurus is designed with respect to two languages: English and Spanish, where a simple bilingual listing of terms, phrases, concepts, and subconcepts is built. Second, term vector translation is used – a statistical multilingual text retrieval techniques that maps statistical information about term use between languages (Ontology co-learning). These techniques map sets of t f id f term weights from one language to another. We also applied a query translation method to retrieve multilingual documents with an expansion technique for phrasal translation. Finally, we present our findings. 相似文献