全文获取类型
收费全文 | 11180篇 |
免费 | 1122篇 |
国内免费 | 770篇 |
专业分类
电工技术 | 702篇 |
技术理论 | 1篇 |
综合类 | 890篇 |
化学工业 | 1784篇 |
金属工艺 | 707篇 |
机械仪表 | 742篇 |
建筑科学 | 1050篇 |
矿业工程 | 286篇 |
能源动力 | 380篇 |
轻工业 | 451篇 |
水利工程 | 517篇 |
石油天然气 | 1083篇 |
武器工业 | 59篇 |
无线电 | 723篇 |
一般工业技术 | 1301篇 |
冶金工业 | 753篇 |
原子能技术 | 50篇 |
自动化技术 | 1593篇 |
出版年
2024年 | 42篇 |
2023年 | 124篇 |
2022年 | 230篇 |
2021年 | 286篇 |
2020年 | 328篇 |
2019年 | 344篇 |
2018年 | 276篇 |
2017年 | 391篇 |
2016年 | 439篇 |
2015年 | 426篇 |
2014年 | 692篇 |
2013年 | 605篇 |
2012年 | 762篇 |
2011年 | 851篇 |
2010年 | 548篇 |
2009年 | 723篇 |
2008年 | 592篇 |
2007年 | 772篇 |
2006年 | 750篇 |
2005年 | 537篇 |
2004年 | 492篇 |
2003年 | 465篇 |
2002年 | 407篇 |
2001年 | 342篇 |
2000年 | 296篇 |
1999年 | 262篇 |
1998年 | 205篇 |
1997年 | 156篇 |
1996年 | 119篇 |
1995年 | 115篇 |
1994年 | 82篇 |
1993年 | 54篇 |
1992年 | 45篇 |
1991年 | 33篇 |
1990年 | 34篇 |
1989年 | 28篇 |
1988年 | 13篇 |
1987年 | 12篇 |
1986年 | 12篇 |
1985年 | 12篇 |
1984年 | 12篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1979年 | 15篇 |
1978年 | 8篇 |
1964年 | 12篇 |
1958年 | 7篇 |
1957年 | 11篇 |
1956年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
为保证大型弹簧钢片在热处理过程中,不发生开裂和翘起度超差,重新制订了热处理工艺。通过增加高温回火、降低淬火温度、加快冷却速度等手段,获得了最好的效果。 相似文献
62.
在化学清洗实践中 ,除垢钝化一步法具有经济、废液处理容易等优点。在实验研究的基础上 ,本文对一步法的清洗原理及应用时的一般情况进行了介绍 相似文献
63.
聚合物类阻垢缓蚀剂是工业循环冷却水中最常用的水处理剂。介绍了红外光谱仪、核磁共振仪、凝胶渗透液相色谱、扫描电镜等测试仪器在阻垢缓蚀剂研究中的应用。 相似文献
64.
Zvi Mendel Lev Zegelman Alfred Hassner Fabienne Assael Miriam Harel Shlomo Tam Ezra Dunkelblum 《Journal of chemical ecology》1995,21(3):331-341
The active component of the sex pheromone ofMatsucoccus josephi is (2E,6E,8E)-5,7-dimethyl-2,6,8-decatrien-4-one; the chemical is also a powerful kairomone of adult males and females of the bugElatophilus hebraicus the principal predator ofM. josephi. The presence of theZ isomer (2E,6Z,8E)-5,7-dimethyl-2,6,8-decatrien-4-one does not interfere with the attractancy of the activeE component forM. josephi males or the bug. Our results show a clear dose-response between trap catch ofM. josephi males andE. hebraicus. Conversely, increasing amounts of theZ isomer in the mixture did not affect the attraction of the scale insect males or the bug. The catch ofM. josephi males did not differ significantly among traps of different color, and was significantly higher with traps attached to the tree trunk than those suspended between trees. Comparison of the catch ofM. josephi among the three forests and between pine species suggests that the level of infestation ofPinus halepepsis andPinus brutia ssp.brutia is similar, despite the fact that the latter pine is resistant to the scale insect. Both sexes ofE. hebraicus were trapped in much lower numbers at the more infested sites. This may be related to interference with the activity ofE. hebraicus due to deterioration and drying of parts of the tree crowns and heavy colonization by generalist predators in injured trees. 相似文献
65.
66.
Local‐scale Benefits of River Connectivity Restoration Planning Beyond Jurisdictional Boundaries 下载免费PDF全文
A. W. Milt P. J. Doran M. C. Ferris A. T. Moody T. M. Neeson P. B. McIntyre 《河流研究与利用》2017,33(5):788-795
Conservation planning aims to optimize outcomes for select species or ecosystems by directing resources toward high‐return sites. The possibility that local benefits might be increased by directing resources beyond the focal area is rarely considered. We present a case study of restoring river connectivity for migratory fish of the Great Lakes Basin by removing dams and road crossings within municipal jurisdictions versus their broader watersheds. We found that greater river connectivity could often be achieved by considering both intra‐jurisdictional and extra‐jurisdictional barriers. Focusing on jurisdictional barriers alone generally forfeited <20% (median = 0%) of habitat gains for those who value solely habitat gains within the jurisdiction, but >75% (median = 100%) for planners who value larger‐scale habitat gains. Similarly, cost savings tended to be between ?50% and +50%, but in some cases were very negative. Our study underscores the local‐scale benefits of broadening restoration investments, especially for decision makers of the Great Lakes Basin and contributes to a discussion of appropriate and efficient scales of conservation planning. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
67.
前大油田注水系统防腐防垢技术的研究 总被引:1,自引:0,他引:1
前大油田注水系统腐蚀、结垢问题十分突出,开发了适用于前大油田注水水质的JYSJ-Q型杀菌剂、JYHZJ-Q型缓蚀阻垢剂,并通过试验确定了配套加药工艺.经现场应用,有效缓解了注水系统的腐蚀结垢问题,获得了显著的社会效益及经济效益. 相似文献
68.
69.
Scale formation has been recognised as a widespread problem in membrane filtration and water desalination processing for water treatment. In this paper, the effect of surface energy of Ni-P-PTFE composite coatings on the microstructure and adhesion of CaSO4 deposits was investigated. The surface energies of the Ni-P-PTFE coatings were altered by changing the PTFE proportion in the coatings. Initial experimental results showed that the surface energy of the coatings had a significant influence on the microstructure and adhesion of CaSO4 deposits. The Ni-P-PTFE coatings have a potential for reducing CaSO4 scale formation on water treatment equipment. 相似文献
70.