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海量空间数据的管理需要多服务器的支持,空间数据的跨服务器操作是必须解决的关键问题。针对Oracle数据库系统的Client/Server体系在管理跨服务器空间数据中存在的问题,利用远程内嵌过程和触发器等相关技术,设计并扩展了Oracle Spatial的功能,实现了基于Oracle的空间数据跨服务器分布式管理。 相似文献
64.
Thermo-plasticity of homogenized 7050 aluminum ingot was investigated by instantaneous tensile tests conducted at different
temperatures. The results show that, with the increase of testing temperatures, the strength decreases, and the plasticity
increases firstly and then decreases in homogenized 7050 ingot. When the studied alloy is deformed between 380 °C and 420
°C, the deformation resistance is lower and plasticity is better. And the actual heating temperature for ingot before hot
extrusion should be controlled between 360 °C and 400 °C. At low tensile temperatures, the deformation structure is mainly
composed of dislocation substructure. With the increase of testing temperatures, transgranular fracture transforms into intergranular
fracture progressively during deformation. At high tensile temperatures, the grain boundaries are weakened, deformation is
concentrated at the grain boundaries and the re-orientation of equilibrium phases at grain boundaries appears. 相似文献
65.
Influence of subsequent curing on water sorptivity and pore structure of steam-cured concrete 总被引:1,自引:0,他引:1
Steam-cured condition is found to cause larger porosity and worse properties of concrete compared with normal curing condition.
For the sake of seeking effective measurements to eliminate this bad effect of steam-cured condition on concrete, the water
sorptivity and pore structure of steam-cured concretes exposed to different subsequent curing conditions were investigated
after steam-curing treatment. The capillary absorption coefficient and porosity of the corresponding concretes were analyzed,
and their mechanisms were also discussed. The results indicate that water sorptivity and pore structure of steam-cured concrete
are greatly influenced by the curing condition used in subsequent ages. Exposure steam-cured concrete to air condition has
an obviously bad effect on its properties and microstructures. Adopting subsequent curing of immersing steam-cured concrete
into about 20 °C water after steam curing period can significantly decrease its capillary absorption coefficient and porosity.
Steam-cured concrete with 7 d water curing has minimum capillary absorption coefficient and total porosity. Its water sorptivity
is decreased by 23% compared with standard curing concrete and the porosity is 9.6% lower. Moreover, the corresponding gradient
of water sorptivity and porosity of steam-cured concrete both decrease, thus microstructure of concrete becomes more homogeneous. 相似文献
66.
为分析重载条件下沥青路面易产生车辙及疲劳病害的成因,基于弹性层状体系理论,利用ABAQUS有限元软件,分别通过车辙量和剪应力、基层疲劳模型表征路面车辙和疲劳寿命,研究了超重交通荷载对沥青路面车辙及疲劳寿命的影响。结果表明,当基层模量为0.4GPa,轴载从100kN增加到200kN时,压密变形量增加了29.82%,路面内最大剪应力增加了24.7%,基层疲劳寿命缩减了95.30%;而当基层模量为2.0GPa时,上述指标分别为27.67%,39.2%,99.26%。由此可知,重载对沥青路面结构破坏影响显著,且随着基层模量的增加,车辙和疲劳病害更加严重。研究结果有助于解释重交通路段沥青路面车辙及疲劳病害的成因。 相似文献
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随着拱坝体型的复杂化,拱坝的建模及网格划分的难度也越来越大。以某拱坝为例,通过实体建模,介绍了ANSYS的APDL参数化建立拱坝的方法、过程与特点;采用ANSYS中的Extend(线的延伸)、Extrude(面的拉伸)和Divide(体切割)功能为该模型划分网格,解决了U型拱坝等边划分出的网格比例不当的问题。结果表明:APDL参数化建模的方法方便、快捷、易学习、易交流修改。采用切割等功能划分出的网格形状合理、比例恰当,并且可根据具体要求变更网格的密度,因此能对类似体型复杂、划分要求较高的有限元模型的划分具有很好的借鉴作用,也为此后的拱坝仿真计算打下坚实的基础。 相似文献
69.
In order to diagnose the working status of each module on sensor node and make sure the wireless sensor networks (WSN) work properly, the components of sensor node and their working characteristics are studied. An on-line fault self-diagnosis method for sensor node is proposed. First, a flexible fault sensing circuit is designed as a state detection module on sensor node. Second, a self-diagnosis algorithm is proposed based on the hardware design and the failure analysis on sensor node. Finally, in order to ensure the WSN reliability, the voltage changes of each module working statuses can be observed using the state detection module and the faulty module will be found out timely. The experimental results show that this self-diagnosis method is suitable to sensor nodes in WSN. 相似文献
70.