全文获取类型
收费全文 | 1609篇 |
免费 | 232篇 |
国内免费 | 183篇 |
专业分类
电工技术 | 74篇 |
综合类 | 225篇 |
化学工业 | 368篇 |
金属工艺 | 34篇 |
机械仪表 | 97篇 |
建筑科学 | 49篇 |
矿业工程 | 38篇 |
能源动力 | 325篇 |
轻工业 | 14篇 |
水利工程 | 361篇 |
石油天然气 | 76篇 |
武器工业 | 29篇 |
无线电 | 50篇 |
一般工业技术 | 124篇 |
冶金工业 | 49篇 |
原子能技术 | 66篇 |
自动化技术 | 45篇 |
出版年
2024年 | 7篇 |
2023年 | 20篇 |
2022年 | 38篇 |
2021年 | 37篇 |
2020年 | 40篇 |
2019年 | 50篇 |
2018年 | 33篇 |
2017年 | 47篇 |
2016年 | 51篇 |
2015年 | 54篇 |
2014年 | 79篇 |
2013年 | 109篇 |
2012年 | 94篇 |
2011年 | 96篇 |
2010年 | 91篇 |
2009年 | 96篇 |
2008年 | 75篇 |
2007年 | 99篇 |
2006年 | 118篇 |
2005年 | 99篇 |
2004年 | 83篇 |
2003年 | 77篇 |
2002年 | 63篇 |
2001年 | 54篇 |
2000年 | 51篇 |
1999年 | 51篇 |
1998年 | 45篇 |
1997年 | 41篇 |
1996年 | 36篇 |
1995年 | 44篇 |
1994年 | 28篇 |
1993年 | 24篇 |
1992年 | 25篇 |
1991年 | 15篇 |
1990年 | 12篇 |
1989年 | 14篇 |
1988年 | 15篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1959年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有2024条查询结果,搜索用时 93 毫秒
41.
根据湍流理论及异形坯连铸的特点, 建立了异形坯结晶器三维流场数学模型, 对不同条件下的流场进行了数值模拟, 分析了水口结构和工艺参数变化时异形坯结晶器内涡心深度的变化规律及液面湍动能的分布状态. 结果表明 采用上倾式水口, 水口夹角为120°, 拉速为0.9m/s时, 结晶器内流场分布较为合理, 液面较稳定. 模拟结果与水模实验结果吻合较好. 该模型可对连铸过程进行离线分析, 确定最佳参数, 并可作为在线控制模型的基础. 相似文献
42.
跌坎型底流消能工消力池内的水力特性受到跌坎深度的影响。应用平面紊动射流理论,以消力池内允许的最大时均动水压强为控制目标,对于跌坎最小深度的确定方法进行了初步分析,建立了计算跌坎最小深度值的理论公式。通过水力学试验方法,得到消力池底板时均动水压强与跌坎最小深度之间的关系,同时与跌坎最小深度试验值进行了比对,对本文建立的理论公式进行了验证。 相似文献
43.
The inception cavitating flows around a blunt body are studied based on flow visualizations and velocity field measurements. The main purpose of the present work is to study the incipient cavity evolution and the interplay between the inception cavitation and the local turbulent flows. A high-speed video camera is used to visualize the cavitating flow structures, and the particle image velocimetry(PIV) technique is used to measure the velocity field, the vorticity, and the Reynolds stresses under non-cavitating and inception cavitating flow conditions. It is found that the appearance of visible cavities is preceded by the formation of a cluster of micro-bubbles not attached to the body surface and in a hairpin-shaped vortex structure. During its evolution, the cavity moves downstream with a lower speed. The effect of the incipient cavity is significant on the local vortical structures but slight on the timeaveraged velocity distribution. The mean Reynolds stress distributions in the turbulent shear flow can be substantially altered by the incipient cavities. The presence of the incipient cavities can lead to the production of turbulent fluctuations. 相似文献
44.
45.
王环东 《水电自动化与大坝监测》2011,35(2):34-35
针对小山电站2号机组推力漏油问题,通过加大稳油板尺寸、加装挡油圈内挡油板、改变油位等方法进行了综合性的处理,弥补了推力轴承甩油导致碳刷打火这一重大缺陷,保证了机组的安全稳定运行. 相似文献
46.
Nikolai N. Kukharkin 《Journal of scientific computing》1995,10(4):409-448
General conditions for the formation of long-lived coherent vortices in decaying and force-driven 2-D turbulence are investigated. It is shown by a series of numerical simulations that the emergence of closed streamlines leading to the trapped trajectories of vorticity is a necessary, but not sufficient condition for this phenomenon, so that these trapped trajectories may be considered only as seed vortices. Numerical experiments which demonstrate the relations between phase correlations, finite-size effects, and the formation of coherent vortices in 2-D decaying turbulence are presented. It is shown that there is a universal dimensionless time for the onset of intermittency in the flow which corresponds to the time of establishment of phase correlations. The stricter conditions for appearance of coherent vortices in forced turbulence in comparison with decaying turbulence are associated with phase mixing introduced by random forcing. The universal features of decaying turbulence are discussed in terms of phase portraits based on inviscid constants of motion and their decay rates. 相似文献
47.
侧式进出水口出流工况水流呈现扩散态,拦污栅断面脉动流速很大,可能危及拦污栅安全,其脉动流速变化规律及产生原因有待进一步探讨。本文建立了典型进出水口试验装置,利用激光多普勒流速仪与声学多普勒流速仪开展试验研究。结果表明:在靠近扩散水流末端的拦污栅断面脉动流速很大,流速脉动值可达时均值的1.8倍,平均紊动强度为0.724,该断面流速脉动呈现出明显的正态性,其概率密度分布基本服从正态分布;水流自输水隧洞段经扩散段、调整段、防涡段、向库区流动的过程中,紊动强度沿程呈现先增大后减小的变化规律,水流在输水隧洞段脉动流速小,在扩散段及调整段内脉动流速沿程均较大,脉动流速值接近时均值,甚至大于时均值,进一步解释了拦污栅断面脉动流速很大的原因。拦污栅断面及进出水口沿程的脉动流速规律有别于对脉动流速的一般认知规律。研究成果将为进出水口体型参数优化及分析引起拦污栅振动破坏提供理论依据。 相似文献
48.
Defect‐Laden MoSe2 Quantum Dots Made by Turbulent Shear Mixing as Enhanced Electrocatalysts 下载免费PDF全文
Chongyang Zhu Yuan Huang Feng Xu Peng Gao Binghui Ge Jing Chen Haibo Zeng Eli Sutter Peter Sutter Litao Sun 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(27)
A high density of edge sites and other defects can significantly improve the catalytic activity of layered 2D materials. Herein, this study demonstrates a novel top‐down strategy to maximize catalytic edge sites of MoSe2 by breaking up bulk MoSe2 into quantum dots (QDs) via “turbulent shear mixing” (TSM). The ultrasmall size of the MoSe2 QDs provides a high fraction of atoms in reactive edge sites, thus significantly improving the catalytic activities. The violent TSM further introduces abundant defects as additional active sites for electrocatalytic reactions. These edge‐proliferated and defect‐laden MoSe2 QDs are found to be efficient electrocatalysts for the hydrogen evolution reaction, and useful as counter electrodes in dye‐sensitized solar cells. The work provides a new paradigm for creating edge‐proliferated and defect‐rich QDs from bulk layered materials. 相似文献
49.
50.
Demanding the compatibility of semi-Lagrangian trajectory schemes with the fundamental Euler expansion formula leads to the Monge-Ampère (MA) nonlinear second-order partial differential equation. Given standard estimates of the departure points of flow trajectories, solving the associated MA problem provides a corrected solution satisfying a discrete Lagrangian form of the mass continuity equation to round-off error. The impact of the MA enhancement is discussed in two diverse limits of fluid dynamics applications: passive tracer advection in a steady cellular flow and in fully developed turbulence. Improvements of the overall accuracy of simulations depend on the problem and can be substantial. 相似文献