全文获取类型
收费全文 | 11714篇 |
免费 | 918篇 |
国内免费 | 538篇 |
专业分类
电工技术 | 701篇 |
技术理论 | 1篇 |
综合类 | 750篇 |
化学工业 | 1961篇 |
金属工艺 | 554篇 |
机械仪表 | 760篇 |
建筑科学 | 769篇 |
矿业工程 | 431篇 |
能源动力 | 309篇 |
轻工业 | 709篇 |
水利工程 | 195篇 |
石油天然气 | 863篇 |
武器工业 | 93篇 |
无线电 | 1274篇 |
一般工业技术 | 1424篇 |
冶金工业 | 636篇 |
原子能技术 | 131篇 |
自动化技术 | 1609篇 |
出版年
2024年 | 60篇 |
2023年 | 218篇 |
2022年 | 357篇 |
2021年 | 495篇 |
2020年 | 400篇 |
2019年 | 369篇 |
2018年 | 365篇 |
2017年 | 372篇 |
2016年 | 344篇 |
2015年 | 463篇 |
2014年 | 562篇 |
2013年 | 649篇 |
2012年 | 783篇 |
2011年 | 761篇 |
2010年 | 692篇 |
2009年 | 682篇 |
2008年 | 627篇 |
2007年 | 617篇 |
2006年 | 673篇 |
2005年 | 528篇 |
2004年 | 379篇 |
2003年 | 308篇 |
2002年 | 303篇 |
2001年 | 262篇 |
2000年 | 270篇 |
1999年 | 299篇 |
1998年 | 245篇 |
1997年 | 216篇 |
1996年 | 191篇 |
1995年 | 167篇 |
1994年 | 134篇 |
1993年 | 84篇 |
1992年 | 74篇 |
1991年 | 57篇 |
1990年 | 52篇 |
1989年 | 34篇 |
1988年 | 21篇 |
1987年 | 17篇 |
1986年 | 18篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 8篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1959年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
952.
城市交通态势推演和评估技术是城市交通治理的核心量化分析技术.随着城市交通治理综合化、精细化和智能化要求的提高,传统依托小样本数据调查与分析,建立集计经验模型进行多方案比选评估的方法和技术,已难以适应新时期城市交通治理要求.本项目历时十余年,在国家自然科学基金等国家级、省部级课题支持下,突破了基于多源大数据的个体出行活动链全过程全方式融合感知、城市交通演化态势可靠推演与敏捷预测、城市交通精细化治理综合评估等关键技术,建立了面向城市交通精细化治理的个体出行活动链模型和大规模路网实时在线推演模型,构建了大数据综合评估体系,支撑了城市交通精细化治理科学量化分析与评估.项目应用超过1000个项目,推广至成都、重庆、苏州、湛江、南昌、长春、兰州等100多座城市,影响了全国约2亿人的交通出行. 相似文献
953.
根据洱海现有游船的特点和数量,基于游船产生的含油废水、固体废弃物、生活污水,分析了游船旅游活动对洱海环境的影响及其特点,并在此基础上提出了洱海游船污染防治措施。 相似文献
954.
Hang Lin Wei Zhang Ze-Xi Dong Ting Gu Nian-Guang Li Zhi-Hao Shi Jun Kai Cheng Qu Guan-Xiong Shang Yu-Ping Tang Fang Fang He-Min Li Jian-Ping Yang Jin-Ao Duan 《International journal of molecular sciences》2015,16(4):7587-7594
Scutellarin (1) has been used for the treatment of angina pectoris, cerebral infarction and coronary heart disease with a large market share in China. Pharmacokinetic studies on scutellarin showed that scutellarin (1) is readily converted into its metabolites in vivo. In this paper, a new and practical synthetic method for the synthesis of 6-O-methyl-scutellarein (3) (one metabolite of scutellarin in vivo) is reported. The benzyl bromide was firstly used to selectively replace the acetyl group at C-7 in 7, and was then used to protect the hydroxy groups at C-4'' in 10, 6-O-methyl-scutellarein (3) is obtained in high yield through these methods. 相似文献
955.
Dongdong Wang Wuxia Zhang Tingting Wang Na Li Haibo Mu Jiwen Zhang Jinyou Duan 《International journal of molecular sciences》2015,16(8):17668-17681
In this study, 2-(N-pyrrolidine-alkyl) tanshinones bearing pyrrolidine groups were synthesized and the antibacterial mechanism was explored. These derivatives selectively elicited antibacterial activity against Gram-positive bacteria. Moreover, their antibacterial activities were time-, concentration-dependent and persistent. It appeared that Fenton-mediated hydroxyl radicals were involved, and the disruption of cell membranes was observed. This study indicates that 2-(N-pyrrolidine-alkyl) tanshinones might be potential candidates as antibacterial agents. 相似文献
956.
Huishan Zhang Shoubing Zhang Huashan Zhao Jingqiao Qiao Shuang Liu Zhili Deng Xiaohua Lei Lina Ning Yujing Cao Yong Zhao Enkui Duan 《International journal of molecular sciences》2015,16(8):17779-17797
Hair follicle stem cells (HFSCs) possess fascinating self-renewal capacity and multipotency, which play important roles in mammalian hair growth and skin wound repair. Although HFSCs from other mammalian species have been obtained, the characteristics of ovine HFSCs, as well as the methods to isolate them have not been well addressed. Here, we report an efficient strategy to obtain multipotent ovine HFSCs. Through microdissection and organ culture, we obtained keratinocytes that grew from the bulge area of vibrissa hair follicles, and even abundant keratinocytes were harvested from a single hair follicle. These bulge-derived keratinocytes are highly positive for Krt15, Krt14, Tp63, Krt19 and Itga6; in addition to their strong proliferation abilities in vitro, these keratinocytes formed new epidermis, hair follicles and sebaceous glands in skin reconstitution experiments, showing that these are HFSCs from the bulge outer root sheath. Taken together, we developed an efficient in vitro system to enrich ovine HFSCs, providing enough HFSCs for the investigations about the ovine hair cycle, aiming to promote wool production in the future. 相似文献
957.
958.
Zitian Chen Prof. Haifeng Duan Shuo Qiao Wenxiong Zhou Haiwei Qiu Li Kang Prof. X. Sunney Xie Prof. Yanyi Huang 《Chembiochem : a European journal of chemical biology》2015,16(8):1153-1157
Fluorogenic sequencing is a sequencing‐by‐synthesis technology that combines the advantages of pyrosequencing and fluorescence detection. With native duplex DNA as the major product, we employ polymerase to incorporate the complement‐ arily matched terminal phosphate‐labeled fluorogenic nucleotides into the DNA template and release halogen‐fluorescein as the reporter. This red‐emitting fluorophore successfully avoids spectral overlap with the autofluorescence background of the flow chip. We fully characterized the enzymatic reaction kinetics of the new substrates, and performed a 35‐base sequencing experiment with 60 reaction cycles. Our achievement expands the substrate repertoire for fluorogenic sequencing, and extends the spectral range to obtain better signal‐to‐background performance. 相似文献
959.
高强钢筋高强混凝土双连梁剪力墙抗震性能试验研究 总被引:1,自引:0,他引:1
高强钢筋、高强混凝土剪力墙结构中使用双连梁可以有效改善结构受力性能,解决设计中经常遇到的诸如连梁超筋、截面受剪承载力不足等问题。基于此,设计并制作了2个3层1/4缩尺的高强钢筋高强混凝土双肢剪力墙试件,其中一个试件的连梁采用单连梁形式,另一个试件的连梁采用双连梁形式。在相同的试验条件下,对比研究二者在低周反复荷载作用下的承载力、滞回特性、延性、耗能能力,分析双连梁结构形式在高强钢筋高强混凝土双肢剪力墙中的性能及作用。试验结果表明:具有相同配筋率的分缝双连梁双肢剪力墙结构与小跨高比单连梁双肢剪力墙结构相比,承载力降低了20%~30%,延性增加了约30%,耗能能力增加了约20%,在弹性阶段刚度降低约30%。从最终的破坏形态来看,单连梁剪力墙试件连梁出现了明显的剪切斜裂缝,箍筋全部屈服,最终发生剪切破坏;双连梁剪力墙试件只在连梁端部出现了弯曲裂缝未出现斜裂缝,箍筋自始至终未屈服,最终发生弯曲破坏。双连梁剪力墙结构能有效降低连梁内力,提高其延性。 相似文献