全文获取类型
收费全文 | 24194篇 |
免费 | 1226篇 |
国内免费 | 536篇 |
专业分类
电工技术 | 1051篇 |
技术理论 | 2篇 |
综合类 | 751篇 |
化学工业 | 3798篇 |
金属工艺 | 918篇 |
机械仪表 | 1001篇 |
建筑科学 | 1202篇 |
矿业工程 | 297篇 |
能源动力 | 541篇 |
轻工业 | 2281篇 |
水利工程 | 323篇 |
石油天然气 | 669篇 |
武器工业 | 97篇 |
无线电 | 2648篇 |
一般工业技术 | 3265篇 |
冶金工业 | 3713篇 |
原子能技术 | 333篇 |
自动化技术 | 3066篇 |
出版年
2024年 | 51篇 |
2023年 | 249篇 |
2022年 | 393篇 |
2021年 | 646篇 |
2020年 | 480篇 |
2019年 | 463篇 |
2018年 | 551篇 |
2017年 | 575篇 |
2016年 | 575篇 |
2015年 | 588篇 |
2014年 | 851篇 |
2013年 | 1224篇 |
2012年 | 1123篇 |
2011年 | 1365篇 |
2010年 | 1082篇 |
2009年 | 1066篇 |
2008年 | 1187篇 |
2007年 | 1174篇 |
2006年 | 1041篇 |
2005年 | 956篇 |
2004年 | 702篇 |
2003年 | 686篇 |
2002年 | 723篇 |
2001年 | 647篇 |
2000年 | 530篇 |
1999年 | 529篇 |
1998年 | 1189篇 |
1997年 | 790篇 |
1996年 | 627篇 |
1995年 | 481篇 |
1994年 | 404篇 |
1993年 | 355篇 |
1992年 | 223篇 |
1991年 | 176篇 |
1990年 | 167篇 |
1989年 | 178篇 |
1988年 | 160篇 |
1987年 | 125篇 |
1986年 | 126篇 |
1985年 | 167篇 |
1984年 | 115篇 |
1983年 | 100篇 |
1982年 | 81篇 |
1981年 | 97篇 |
1980年 | 94篇 |
1979年 | 92篇 |
1977年 | 112篇 |
1976年 | 165篇 |
1975年 | 56篇 |
1973年 | 60篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
J. Buytaert L. De Boeck F. Verbeure
C. Bricman
F. Cao C. De Clercq L. Etienne B. Goorens J. Lemonne F. Stichelbaut S. Tavernier G. Van Beek C. Vander Velde W. Van Doninck L. Van Lancker J. WickensE. Daubie
F. Defontaines F. Grard J. Kesteman O. Pingot C. Poiret 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1991,310(3):596-606The layout and construction of the muon drift chambers equipping the end caps of the DELPHI detector are described. The performance of this forward muon detection system, determined from cosmic ray tests and data collected during the first year of LEP operation, is presented. 相似文献
82.
Influence of Storage Time and Temperature on Absorption of Flavor Compounds from Solutions by Plastic Packaging Materials 总被引:1,自引:0,他引:1
R. Van Willige D. Schoolmeester A. Van Ooij J. Linssen A. Voragen 《Journal of food science》2002,67(6):2023-2031
ABSTRACT: Linear low-density polyethylene (LLDPE), oriented polypropylene (OPP), polycarbonate (PC), polyethylene terephthalate (PET film and PET bottle), and polyethylene naphthalate (PEN) were stored in a model solution containing 10 flavor compounds at 4, 20, and 40 °C and flavor absorption by the plastic materials was followed in time. The absorption rate and/or total amount absorbed increased considerably with temperature from 4 to 40 °C. Depending on storage temperature, total flavor absorption by the polyolefins (LLDPE and OPP) was 3 to 2400 times higher than by the polyesters (PC, PET, and PEN). Therefore, in the factor of flavor absorption, polyesters are preferred over polyolefins as packaging material. 相似文献
83.
84.
蒸馏与减粘热联合装置的设备腐蚀及防护 总被引:4,自引:2,他引:2
介绍了锦西石化分公司南蒸馏与减粘热联合装置炼制辽河高酸值原油及带炼高硫进口油在 2 0 0~40 0℃范围内对设备、管线和阀门的腐蚀特点、腐蚀机理以及针对高温环烷酸腐蚀所采取的防护措施。通过试验和理论分析 ,提出了应用新材料和新工艺解决减粘后高温渣油系统的腐蚀及低温露点腐蚀的建议 相似文献
85.
J G De Nobel F M Klis A Ram H Van Unen J Priem T Munnik H Van Den Ende 《Yeast (Chichester, England)》1991,7(6):589-598
To study cell-cycle-related variations in wall permeability of Saccharomyces cerevisiae, two approaches were used. First, an asynchronous culture was fractionated by centrifugal elutriation into subpopulations containing cells of increasing size. The subpopulations represented different stages of the cell cycle as judged by light microscopy. Cell wall porosity increased when these subpopulations became enriched with budded cells. Secondly, synchronous cultures were obtained by releasing MATa cells from alpha-factor induced G1-arrest. These cultures grew synchronously for at least two generations. The cell wall porosity increased sharply in these cultures, shortly before buds became visible and was maximal during the initial stages of bud growth. It decreased in cells which had completed nuclear migration and before abscission of the bud had occurred. The porosity reached its lowest value during abscission and in unbudded cells. We examined the incorporation of mannoproteins into the wall during the cell cycle. SDS-extractable mannoproteins were incorporated continuously. However, the incorporation of glucanase-extractable mannoproteins, which are known to affect cell wall porosity, showed cyclic oscillations and reached its maximum after nuclear migration. This coincided with a rapid decrease in cell wall porosity, indicating that glucanase-extractable mannoproteins might contribute to this decrease. 相似文献
86.
An analysis is made of longitudinal effects in semiconductor lasers with low facet reflectivities. For this purpose, a self-consistent model is used based on the beam propagation method, which takes into account both the lateral and longitudinal dimension. The calculations show that longitudinal effects have a significant influence on the output fields in the laser. 相似文献
87.
88.
介绍了葡北地区地质构造及分层特征 ,分析了钻井难点 ,并给出了详细对策 ,从钻具组合、钻头优选、钻进参数优选、钻井液体系及安全技术措施等方面详细介绍了该区快速钻井技术。在葡北 4 - 11井和葡北 6- 1井的应用表明 ,该快速钻井技术能显著提高钻速 ,钻井周期明显缩短 相似文献
89.
双螺杆反应挤出模型的研究 总被引:5,自引:0,他引:5
详细研究了双螺杆中反应挤出聚合物的动力学模型、流动模型和传热模型。通过实验得到了双螺杆反应器中聚合物的停留时间分布及平均停留时间。 相似文献
90.
供应链管理的研究综述 总被引:31,自引:0,他引:31
首先阐述了供应链管理的概念,在此基础之上提出目前供应链的研究框架,并指出供应链管理实践中存在的问题,最后提出未来研究方向。 相似文献