全文获取类型
收费全文 | 34832篇 |
免费 | 3908篇 |
国内免费 | 2351篇 |
专业分类
电工技术 | 3982篇 |
综合类 | 3997篇 |
化学工业 | 3008篇 |
金属工艺 | 2441篇 |
机械仪表 | 3088篇 |
建筑科学 | 3291篇 |
矿业工程 | 2200篇 |
能源动力 | 1526篇 |
轻工业 | 2394篇 |
水利工程 | 1310篇 |
石油天然气 | 1948篇 |
武器工业 | 610篇 |
无线电 | 2914篇 |
一般工业技术 | 3339篇 |
冶金工业 | 1237篇 |
原子能技术 | 458篇 |
自动化技术 | 3348篇 |
出版年
2024年 | 176篇 |
2023年 | 502篇 |
2022年 | 963篇 |
2021年 | 1097篇 |
2020年 | 1194篇 |
2019年 | 1003篇 |
2018年 | 986篇 |
2017年 | 1271篇 |
2016年 | 1357篇 |
2015年 | 1422篇 |
2014年 | 2115篇 |
2013年 | 2075篇 |
2012年 | 2556篇 |
2011年 | 2794篇 |
2010年 | 2112篇 |
2009年 | 2200篇 |
2008年 | 1955篇 |
2007年 | 2641篇 |
2006年 | 2263篇 |
2005年 | 1806篇 |
2004年 | 1482篇 |
2003年 | 1233篇 |
2002年 | 999篇 |
2001年 | 866篇 |
2000年 | 765篇 |
1999年 | 609篇 |
1998年 | 436篇 |
1997年 | 456篇 |
1996年 | 351篇 |
1995年 | 293篇 |
1994年 | 253篇 |
1993年 | 169篇 |
1992年 | 166篇 |
1991年 | 120篇 |
1990年 | 84篇 |
1989年 | 81篇 |
1988年 | 62篇 |
1987年 | 24篇 |
1986年 | 31篇 |
1985年 | 14篇 |
1984年 | 22篇 |
1983年 | 16篇 |
1982年 | 17篇 |
1981年 | 5篇 |
1980年 | 10篇 |
1979年 | 13篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1975年 | 3篇 |
1959年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
An efficient path planning algorithm based on topologic method is presented in this paper.The collision free path planning for three-joint robotic arm consists of three parts:partition of C-space,construction of CN and search for a path in CN.We mainly solved the problems of partitioning the C-space and undging the connectivity between connected blocks,etc.For the motion planning of a robotic arm with a gripper,we developed the concepts of global planning and local planning,and discussed the basic factors for constructing the planning system.In the paper,some evaluation and analysis of the complexity and reliability of the algorithm are given,together with some ideas to improve the efficiency and increase the reliability.At last,some experimental results are pesented to show the efficency and accuracy of the algorithm. 相似文献
12.
预分解窑燃无烟煤生产水泥熟料技术及其应用 总被引:2,自引:2,他引:0
无烟煤着火温度高、燃烧速度低、燃烬时间长,故一直难以用作回转窑燃料.20世纪90年代,南京院率先进行了回转窑燃无烟煤生产的研究开发.经10多年的努力,解决了所有的技术问题,开发了配套的专有装备,已在福建三德水泥厂、福建南平水泥公司、龙岩春池集团、广西鱼峰水泥公司等厂的多条生产线上应用并获巨大成功. 相似文献
13.
ABSTRACT: Texture changes during ripening of Port Salut Argentino cheese for different sampling zones were studied. Compression relaxation tests were performed and results were analyzed using both Maxwellian and Peleg's models. Elastic equilibrium modulus obtained from the Maxwellian model decreased from 1.22 to 0.11 104 Pa during ripening. The constants derived from Peleg's model, k1 and k2 , diminished with ripening time from 1.18 to 0.71 min and from 1.27 to 1.12, respectively. Asymptotic equilibrium modulus from Peleg's model decreased from 0.95 to 0.07 104 Pa during ripening. Rate parameters derived from a 1st order kinetics applied to both equilibrium moduli showed that the decrease was faster in the external zone (0.0846 d−1 ) than in the central zone (0.0368 d−1 ). The correlation between equilibrium moduli, salt concentration, moisture content, and maturation indexes was obtained with a determination coefficient of 0.76. 相似文献
14.
准噶尔盆地侏罗系储集层的基本特征及其主控因素分析 总被引:28,自引:8,他引:20
从描述储集层基本特征、分析储集层性质的主控因素、建立储集层成因模式和评价、预测储集层性质这 4个层次 ,研究准噶尔盆地重点勘探目标区的侏罗系储集层。系统总结侏罗系储集层岩石学特征 ,认为成岩压实作用强弱是控制储集层性质的关键因素 ;指出相对优质储集层均为剩余原生粒间孔隙型储集层 ,溶蚀作用对渗透率贡献小 ;非煤系储集层的孔隙保存条件明显比煤系储集层好 ,这是三工河组、头屯河组和吐谷鲁群的物性普遍优于八道湾组和西山窑组的原因。在确定储集层性质的控制因素和控制机理基础上 ,建立了煤系和非煤系两大类储集层的成因 演化模型。在上述研究的基础上 ,分地区、分层位评价了储集层 ,并预测了不同渗透率储集层的深度界线及相对优质储集层的平面分布。图 6参 10 相似文献
15.
直线式电机在有杆抽油设备中的应用 总被引:4,自引:0,他引:4
通过对游梁式抽油机的效率、启动特性与直线式电机驱动的有杆抽油机特性的对比,论述了直线抽油机的优越性及应用前景。 相似文献
16.
大长径比自旋弹箭横向自振特性的有限元计算方法与结果分析 总被引:2,自引:0,他引:2
本文研究大长径比自旋弹箭在飞行时横向振动的自振特性。本文将转子动力学应用于弹道学 ,采用有限元法 ,建立自旋弹箭横向振动自振特性方程。同时给出了计算方法。利用该方程和该方法 ,开发了相应的计算程序。通过数值计算 ,可给出细长旋转弹箭飞行时的进动转速和临界转速 ,以及相应的位移和角度振型。利用该程序 ,进行了实例计算和分析。 相似文献
17.
I. Revilla & M. L. González-San José 《International Journal of Food Science & Technology》2003,38(1):29-36
Summary The effect of the addition of four commercial pectolytic preparations on the visual characteristics (colour and turbidity) of red wines has been evaluated. The effect of both clarifying and colour extracting enzymes and the effect of different doses used, were evaluated and compared. All the red wines treated enzymatically, independent of the type of enzyme and dose, present chromatic characteristics which can be considered better than those of the control wines. Also, those wines treated with enzymes had greater stability during 2 years storage in bottles, in particular the turbidity was better than untreated wines. 相似文献
18.
真空制盐蒸发结晶器的设计与实践 总被引:2,自引:0,他引:2
真空蒸发制盐外热式强制逆循环轴向出料蒸发结晶器,经多个厂家生产应用实践证明是成功的,具有生命力的。这种新型结构,作为一项新技术新设备应加强研究,总结提高,推广应用。不断完善。文章从流体力学、结晶机理角度要求,到具体工程设计参数和材质选用。论述了该罐的特点。 相似文献
19.
This article introduces the basic structure of a symmetric self-electrooptic effect device (S-SEED), and applies the Kirchoff' s current law and a purely equivalent capacitive model, to analyze S-SEED's switch characteristics. Linear approximation and N-segment approximation are utilized to obtain S-SEED's voltage-time (V-T) and characteristics. Theoretical analysis is verified by simulations, and the results demonstrate that the precision of S-SEED's switch time can satisfy the requirement in applications with linear approximation. Moreover, the simulations compare S-SEED's switch characteristics with different input powers and input contrast ratios, which reveal that increasing input contrast ratio is an effective way to improve S-SEED's switch characteristics. 相似文献
20.
Diane M. Hopkins Alan D. Jackson Kenneth Oates 《Microscopy research and technique》1991,18(2):176-182
The standardisation of frozen hydrated bulk biological specimens using gelatin standards is described. The relationship between corrected elemental X-ray counts and ionic concentration was found to be linear, and minimum detectable limits for each element are stated. Variations in uncorrected standard curves were found to be due to changes in aluminium coating thickness. There was an inverse relationship between coating thickness and elemental X-ray counts. The factors causing this are discussed. To avoid errors arising from inconsistent aluminium thickness, experimental material should only be compared with standards of similar aluminium net counts. This can be achieved most easily by mounting and analysing specimen and standard together. 相似文献