全文获取类型
收费全文 | 32679篇 |
免费 | 2500篇 |
国内免费 | 1285篇 |
专业分类
电工技术 | 1741篇 |
技术理论 | 1篇 |
综合类 | 1971篇 |
化学工业 | 5648篇 |
金属工艺 | 1622篇 |
机械仪表 | 2135篇 |
建筑科学 | 2576篇 |
矿业工程 | 1017篇 |
能源动力 | 852篇 |
轻工业 | 2029篇 |
水利工程 | 552篇 |
石油天然气 | 2116篇 |
武器工业 | 217篇 |
无线电 | 3840篇 |
一般工业技术 | 3972篇 |
冶金工业 | 1621篇 |
原子能技术 | 384篇 |
自动化技术 | 4170篇 |
出版年
2024年 | 174篇 |
2023年 | 590篇 |
2022年 | 896篇 |
2021年 | 1281篇 |
2020年 | 943篇 |
2019年 | 859篇 |
2018年 | 933篇 |
2017年 | 1004篇 |
2016年 | 881篇 |
2015年 | 1166篇 |
2014年 | 1559篇 |
2013年 | 1848篇 |
2012年 | 1979篇 |
2011年 | 2071篇 |
2010年 | 1810篇 |
2009年 | 1775篇 |
2008年 | 1622篇 |
2007年 | 1653篇 |
2006年 | 1797篇 |
2005年 | 1610篇 |
2004年 | 1028篇 |
2003年 | 943篇 |
2002年 | 902篇 |
2001年 | 783篇 |
2000年 | 904篇 |
1999年 | 959篇 |
1998年 | 794篇 |
1997年 | 699篇 |
1996年 | 672篇 |
1995年 | 534篇 |
1994年 | 444篇 |
1993年 | 328篇 |
1992年 | 261篇 |
1991年 | 204篇 |
1990年 | 151篇 |
1989年 | 121篇 |
1988年 | 97篇 |
1987年 | 50篇 |
1986年 | 35篇 |
1985年 | 28篇 |
1984年 | 17篇 |
1983年 | 17篇 |
1982年 | 22篇 |
1981年 | 13篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
基于双链式存储的可靠通信网合并 总被引:2,自引:0,他引:2
本文介绍图的双链式存储结构在可靠通讯网合并算法中的应用. 相似文献
82.
本文从建筑结构中构件裂缝的概念和表征出发,面向图形对象建立裂缝仿真模型,并 从计算机图形学的角度,运用粘贴技术来处理裂缝图形。为了使裂缝更逼真,在知识 推理的基础上,本文运用了随机处理技术。 相似文献
83.
More and more universities and colleges are providing online courses not only for on-campus students but also for off-campus students. Tutors have to consider the differences between on- and off-campus students in order to improve effective instruction. Comparisons are made in this paper between on- and off-campus performances in online learning from four areas: learning time, path of browsing courseware, intercommunication and adaptability towards online learning. The last two areas are emphasized. Multiple approaches were adopted to collect data, which include questionnaires, posted documents, online logs, interviews and observations. This study shows that the rush time of online learning, paths of browsing courseware and favourite intercommunication means of on- and off-campus students are similar. But there are also some differences between these two groups such as competence of self-learning, enthusiasm of interpersonal exchange, dependence on tutors, feeling of learning stress, etc. 相似文献
84.
Synthesis of Single-Crystalline Silicon Nitride Nanobelts Via Catalyst-Assisted Pyrolysis of a Polysilazane 总被引:1,自引:0,他引:1
Weiyou Yang Zhipeng Xie Hezhuo Miao Ligong Zhang Hang Ji Linan An 《Journal of the American Ceramic Society》2005,88(2):466-469
Recently, one-dimensional nanostructures have attracted extensive attention since they are potentially important for both applications and fundamental research. In this paper, we report the synthesis of ultra-long single crystal Si3 N4 nanobelts via catalyst-assisted pyrolysis of polymeric precursors. The obtained products contain both α- and β-Si3 N4 nanobelts, which are 50–100 nm in thickness, 400–1000 nm in width, and a few hundreds of micrometers to several millimeters in length. Different from previous techniques for synthesizing one-dimensional structures, the current nanobelts are synthesized through confined crystallization of an amorphous phase. A solid–liquid–gas–solid reaction/crystallization growth mechanism is proposed. The formation of nanobelts instead of nanowires is attributed to the anisotropy growth at an earlier stage. 相似文献
85.
86.
In breast cancer research, it is of great interest to identify genomic markers associated with prognosis. Multiple gene profiling studies have been conducted for such a purpose. Genomic markers identified from the analysis of single datasets often do not have satisfactory reproducibility. Among the multiple possible reasons, the most important one is the small sample sizes of individual studies. A cost-effective solution is to pool data from multiple comparable studies and conduct integrative analysis. In this study, we collect four breast cancer prognosis studies with gene expression measurements. We describe the relationship between prognosis and gene expressions using the accelerated failure time (AFT) models. We adopt a 2-norm group bridge penalization approach for marker identification. This integrative analysis approach can effectively identify markers with consistent effects across multiple datasets and naturally accommodate the heterogeneity among studies. Statistical and simulation studies demonstrate satisfactory performance of this approach. Breast cancer prognosis markers identified using this approach have sound biological implications and satisfactory prediction performance. 相似文献
87.
88.
Experimental Research on the Dynamic Energy Absorbing Capacity of the Honeycomb Paperboard Filled with Polyurethane 总被引:1,自引:0,他引:1
A kind of composite buffering material was made by filling the voids of honeycomb paperboard with polyurethane. Drop tests were performed to evaluate the dynamic energy absorption capacity of the material. Based on the tests results, the mechanical behaviors of the material under low velocity dynamic impact conditions were analyzed. It was shown that the absorbed energy of the composite material varies inversely with the void diameter. The absorbed energy of the composite material is 1 - 2 times than that of honeycomb paperboard and polyurethane. The energy absorption efficiency of the composite material is better than those of honeycomb paperboard and polyurethane. 相似文献
89.
数字化电气信息采集为数字化变电站乃至智能电网信息化提供直接支撑.针对电子式互感器和合并单元的特点,给出数字化电气信息采集系统的功能模块.从互感器结构、数字传输、数据验证、采样频率和系统配置方面,分析数字化电气信息采集对继电保护可靠性的影响,着重说明了数据同步对差动保护的影响.指出由于存在电子式互感器的稳定性以及网络通讯可依赖性问题,目前数字化变电站继电保护系统在很大程度上仍沿用传统保护的设计思路,有待进行深入研究和突破. 相似文献
90.
众所周知,微生物,如藻类、细菌、霉菌(真菌和酵母)以及病毒可在物品的表面寄生和存活,尤其是当死角、粗糙的表面或微缝中有残存的营养物质时,微生物…在聚合物表面的生长可导致褪色、污渍、臭味、生物膜、交叉感染并最终降低机械强度,降低产品使用寿命。汽巴可为解决上述的问 相似文献