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51.
Some limitations of three dimensional Navier-Stokes Characteristic Boundary Conditions (3D-NSCBC) are discussed for flows traveling in a direction that is oblique to the boundary. To limit errors generated at boundaries with flows having any arbitrary direction, it is proposed to organize the wave decomposition in a coordinate system that is attached to the local flow streamline crossing the boundary, because some modeled expressions are not frame independent. Compared to previous 3D-NSCBC, the modified strategy accounting for oblique waves is found to improve the outflow treatment for transverse outgoing vortices, up to vortices crossing an outflow corner. The method is also applied to an expanding laminar flame. 相似文献
52.
综合涡流和超声波检测技术,针对长庆油田CO2驱小口径管道,成功研制了小口径管道电磁涡流内腐蚀检测机器人和超声波内腐蚀检测机器人,并在长2.97 km、管径为Φ114 mm、壁厚为4.5 mm的管线上进行了试验。研制过程包括检测系统探头、腐蚀情况检测系统、壁厚检测系统、采集处理系统、动力控制系统、储存分析系统、里程记录单元以及上位机成像系统、整体检测系统的设计和开发。电磁涡流内腐蚀检测机器人可用于Φ89 mm、Φ114 mm、Φ133 mm管径的腐蚀检测,能够通过4D弯头,能将管道腐蚀、壁厚减薄甚至盗油孔等隐患进行检测、定位。超声波内腐蚀检测机器人,能够对输油管道进行全程检测和数据记录,确定缺陷在管道上的位置,形成相应波形曲线。 相似文献
53.
为实现对静/动目标的有效定位,推导出定位精度的几何稀释(Geometric Dilution of Positioning Accuracy,GDOP)的协方差矩阵计算公式和GDOP的影响因素。利用时差和目标方位角对静/动目标进行定位的基本原理,可得到定位精度的一般表达式及其理论曲线,以及其目标和接收机之间的相对几何关系与测量误差的关系,可有效实现对静/动目标的定位。 相似文献
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E. Creusé Y. Le Menach S. Nicaise F. Piriou R. Tittarelli 《Computers & Mathematics with Applications》2019,77(6):1549-1562
In this paper a guaranteed equilibrated error estimator is developed for the 3D harmonic magnetodynamic problem of Maxwell’s system. This system is recasted in the classical potential formulation and solved by the Finite Element method. The error estimator is built starting from the numerical solution by a local flux reconstruction technique. Its equivalence with the error in the energy norm is established. A comparison of this estimator with an equilibrated error estimator already developed through a complementary problem points out the advantages and drawbacks of these two estimators. In particular, an analytical benchmark test illustrates the obtained theoretical results and a physical benchmark test shows the efficiency of these two estimators. 相似文献
56.
Michele Scagliarini 《Quality and Reliability Engineering International》2015,31(6):977-988
Multivariate measurement systems analysis (MSA) is usually performed by designing suitable gauge repeatability and reproducibility (R&R) experiments, ignoring available data generated by the measurement system while used for inspection or process control. This article proposes an approach that, by using the data that are routinely available from the regular operation of the instrument, allows the measurement instrument's current precision to be compared against a benchmark. The proposed method may be appropriately used in an integrated and coordinated manner with the usual multivariate gauge study in the sense that it can be used to assess the stability or a possible deterioration in the precision of the measurement instrument while operational. Therefore, the complementary use of the proposed approach and the traditional multivariate gauge R&R studies can be a useful strategy for improving the overall quality of multivariate measurement systems. Furthermore, because it can be implemented at almost no additional cost, it may be effective in reducing the costs of a multivariate MSA performed with a certain frequency. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
57.
Hideo Yamashita Tatsuya Johkoh Shinichi Takita Eihachiro Nakamae 《Computer Animation and Virtual Worlds》1991,2(1):34-40
In order to observe the physical values (magnetic flux density and eddy current) in 3D magnetic field analysis, an interactive and highly manipulative visualization system depicting stereo images is intalled in a graphics workstation with high functional graphic processors. The system has the following characteristics:
- 1 An interactive and highly manipulative menu window with many functions: it enables visualization of complex phenomena in a 3D field through observation of various combinations of physical values from various viewpoints.
- 2 Simultaneous display of both magnetic flux density and eddy current by using the appropriate use of two colour display methods for stream lines and distribution maps of density: this function facilitates observation of the mutual relations between two physical values in a 3D field.
- 3 Animations and stereo displays: since they give extremely distinct images, observers can easily understand even highly complex 3D phenomena.
58.
结合实际涡流无损检测应用中的含磁介质点探头的特点,分析了探头中磁介质引入的各种附加效应及其对缺陷阻抗的影响。通过引入等效电流的概念,讨论了磁介质对涡流场的作用,建立含磁介质点探头涡流无损检测模型,并给出含磁介质探头周围的电磁场方程,求得均匀半无限导体系统的磁矢量势分布和导体中涡流、电场强度分布。通过实例,计算了非铁磁性导体中无缺陷时探头信号与提离高度的关系、存在缺陷时探头阻抗变化的特点。理论计算与实验结果基本吻合。 相似文献
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