全文获取类型
收费全文 | 40105篇 |
免费 | 5720篇 |
国内免费 | 3277篇 |
专业分类
电工技术 | 1844篇 |
技术理论 | 1篇 |
综合类 | 4773篇 |
化学工业 | 4329篇 |
金属工艺 | 3788篇 |
机械仪表 | 3240篇 |
建筑科学 | 4830篇 |
矿业工程 | 3289篇 |
能源动力 | 4487篇 |
轻工业 | 526篇 |
水利工程 | 3127篇 |
石油天然气 | 2602篇 |
武器工业 | 1355篇 |
无线电 | 1705篇 |
一般工业技术 | 4400篇 |
冶金工业 | 1714篇 |
原子能技术 | 662篇 |
自动化技术 | 2430篇 |
出版年
2024年 | 219篇 |
2023年 | 703篇 |
2022年 | 1376篇 |
2021年 | 1498篇 |
2020年 | 1603篇 |
2019年 | 1280篇 |
2018年 | 1304篇 |
2017年 | 1639篇 |
2016年 | 1842篇 |
2015年 | 1846篇 |
2014年 | 2638篇 |
2013年 | 2641篇 |
2012年 | 3392篇 |
2011年 | 3540篇 |
2010年 | 2651篇 |
2009年 | 2668篇 |
2008年 | 2387篇 |
2007年 | 2947篇 |
2006年 | 2503篇 |
2005年 | 2033篇 |
2004年 | 1622篇 |
2003年 | 1277篇 |
2002年 | 983篇 |
2001年 | 856篇 |
2000年 | 669篇 |
1999年 | 546篇 |
1998年 | 428篇 |
1997年 | 402篇 |
1996年 | 331篇 |
1995年 | 260篇 |
1994年 | 231篇 |
1993年 | 167篇 |
1992年 | 135篇 |
1991年 | 101篇 |
1990年 | 91篇 |
1989年 | 60篇 |
1988年 | 33篇 |
1987年 | 34篇 |
1986年 | 28篇 |
1985年 | 13篇 |
1984年 | 19篇 |
1983年 | 8篇 |
1982年 | 14篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 13篇 |
1978年 | 9篇 |
1977年 | 6篇 |
1959年 | 10篇 |
1951年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
91.
Ivan Cimrák 《Archives of Computational Methods in Engineering》2007,15(3):277-309
The Landau-Lifshitz (LL)equation of micromagnetism governs rich variety of the evolution of magnetization patterns in ferromagnetic
media. This is due to the complexity of physical quantities appearing in the LL equation. This complexity causes also an interesting
mathematical properties of the LL equation: nonlocal character for some quantities,nonconvex side-constraints, strongly nonlinear
terms. These effects influence also the numerical approximations. In this work, recent developments on the approximation of
weak solutions, together with the overview of well-known methods for strong solutions,are addressed.
Author is supported by the Fund for Scientific Research - Flanders FWO (Belgium). 相似文献
92.
为了回答灯泡贯流泵装置中的灯泡体究竟应该前置还是应该后置的问题,应用水泵装置三维湍流数值模拟的方法分别研究了南水北调东线工程某泵站前置灯泡和后置灯泡贯流泵装置两个不同方案的流态,揭示了前置灯泡和后置灯泡贯流泵装置的基本流动属性;数值模拟的结果得到流道模型试验的验证。研究结果表明:前置灯泡贯流泵装置的进、出水流态均匀平顺,水力损失较小;后置灯泡贯流泵装置的进水流态均匀平顺,但出水流道内存在明显的偏流和旋涡流动,水力损失较大;灯泡体前置符合水力学的基本原理,是获得最佳灯泡贯流泵装置水力性能的必要条件之一。 相似文献
93.
Lázaro Valentin Zuquette Janaina Barrios Palma Osni José Pejon 《Bulletin of Engineering Geology and the Environment》2005,64(3):257-271
There are more than 20,000 uncontrolled sanitary landfill areas in Brazil. The paper reports an integrated study undertaken
to develop an environmental assessment of the uncontrolled sanitary landfill area of the city of Po?os de Caldas, State of
Minas Gerais, Brazil. A number of remedial alternatives were evaluated. The USGS modular 3D finite difference groundwater
flow model (Modflow) and Modular 3D Finite Difference Mass Transport Model (MT3D) software were used to simulate groundwater
flow and contaminant transport modelling, as well as to predict changes due to the proposed remediation measures. The remedial
alternatives considered for normal conditions from 20 to 40 year periods were waste removal, vertical cut-off barriers, extraction
wells and top capping. The results indicated that extraction wells and waste removal are the best alternatives because they
significantly reduce both the extension and levels of the contamination plume even after 5 years. The extraction well proved
a less expensive remedial alternative than waste removal.
相似文献
94.
1 Introduction Rear axle bevel gearis a vital kind of annular accessory with high precision and hugeload availablefeatures ,andit is widely used as the differential drive in automobiles and tractor .In China ,the traditional manufactureapproach of producing the rear axle bevel gear blankis die forging,which not only requires a highinvestment ofproduct equipments , but also involves a low material utilization and great noise .In order to overcome thesedrawbacks , manyresearchers have done a gre… 相似文献
95.
在普通铣床上实施数控改造后,可应用软件程序使步进电机任意变速,并可在加工过程中任意改变这行方向.从而突破了凸轮加工的传统方式,达到了简化程序、提高效率的同的. 相似文献
96.
旋风燃烧器冷态模型内颗粒运动轨迹计算 总被引:2,自引:0,他引:2
在冷态模型流场内,考虑气流对粉煤颗粒的气动阻力,建立其运动微分方程式。通过计算,得到九种粒径的颗粒在流场中的运动轨迹、停留时间、着膜位置和气-固相相对速度与该燃烧器几何参数和气动参数的关系,为燃烧器的深入研究提出了建议。 相似文献
97.
Li Yu-cheng Teng Bin 《水动力学研究与进展(B辑)》1993,(2)
By using Cokelet's wave theory,the limiting wave height and the relative waveangular frequency in wave-current field were calculated in this paper.It is indicated by numeri-cal calculation that if the water depth is not too small,the result given by authors'calculationare very close to the results of limiting wave height by Dalrymple(1975)and to the data of rel-ative wave angular frequency by linear wave theory;but if water depth is rather small,thereare some discrepancy, 相似文献
98.
Linear stress analysis without body force can be easily carried out by means of the boundary element method. Some cases of linear stress analysis with body force can also be solved without the domain integral. However domain integrals are generally necessary to solve the linear stress problems with complicated body forces. This paper shows that the linear stress problems with complicated body forces can be solved approximately without the domain integral. In order to solve these problems, the domain is divided into small areas using contour lines of body force. In these areas, the distributions of body force are assumed approximately to satisfy the Laplace equation. 相似文献
99.
Wei Xiao-lin Institute of Mechanics Chinese Academy of Sciences Beijing China IVD. Stuttgart University Pfaffenwaldring D Stuttgart Germany Tian Wen-dong Wang Jian-min Sheng Hong-zhi Institute of Mechanics Chinese Academy of Sc 《水动力学研究与进展(B辑)》2001,(1)
NOTATIONSA Areaofinlet ,m2a Centrifugalacceleration ,m2 /si Gridofaxialdirectionml MaximumgridnumberofradialdirectionQ Fluidmassrate ,m3/sRc Maximumradiusofcyclone ,mRe Reynoldsnumberr Dimensionlessradialdistancet Dimensionlesstimeu Dimensionlessaxialveloc… 相似文献
100.
孤东油田极浅海区域新发现几个边际油藏。其中垦东401块水深-2m,距陆地2.7km,为稀油、疏松砂岩油藏,试油获14~25t/d工业油流。在三维地震、测井约束地震反演、数值模拟和油藏经营管理评价基础上编制了产能建设方案,通过修筑海公路、人工岛、丛式井组、大位移水平井、采用数据采集与控制的远程测控和紧急关断技术,能够无人职守、遥测遥控,整体实现了海油陆采。有效动用地质储量233×104t,钻井12口,建成年产油4×104t能力,累产油8.6×104t。目前在垦东12人工岛上钻打了26口井,推广了海油陆采经验。 相似文献