全文获取类型
收费全文 | 9008篇 |
免费 | 580篇 |
国内免费 | 316篇 |
专业分类
电工技术 | 356篇 |
综合类 | 1047篇 |
化学工业 | 366篇 |
金属工艺 | 560篇 |
机械仪表 | 2367篇 |
建筑科学 | 1210篇 |
矿业工程 | 582篇 |
能源动力 | 206篇 |
轻工业 | 155篇 |
水利工程 | 243篇 |
石油天然气 | 188篇 |
武器工业 | 124篇 |
无线电 | 576篇 |
一般工业技术 | 797篇 |
冶金工业 | 130篇 |
原子能技术 | 55篇 |
自动化技术 | 942篇 |
出版年
2024年 | 13篇 |
2023年 | 48篇 |
2022年 | 97篇 |
2021年 | 131篇 |
2020年 | 151篇 |
2019年 | 112篇 |
2018年 | 138篇 |
2017年 | 196篇 |
2016年 | 264篇 |
2015年 | 313篇 |
2014年 | 609篇 |
2013年 | 548篇 |
2012年 | 848篇 |
2011年 | 958篇 |
2010年 | 800篇 |
2009年 | 805篇 |
2008年 | 662篇 |
2007年 | 789篇 |
2006年 | 618篇 |
2005年 | 480篇 |
2004年 | 320篇 |
2003年 | 314篇 |
2002年 | 166篇 |
2001年 | 104篇 |
2000年 | 85篇 |
1999年 | 61篇 |
1998年 | 53篇 |
1997年 | 46篇 |
1996年 | 35篇 |
1995年 | 26篇 |
1994年 | 28篇 |
1993年 | 23篇 |
1992年 | 17篇 |
1991年 | 6篇 |
1990年 | 9篇 |
1989年 | 4篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1979年 | 1篇 |
1972年 | 1篇 |
1961年 | 2篇 |
1960年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有9904条查询结果,搜索用时 15 毫秒
991.
微热对流角速度传感器是一种新型的惯性传感器件,由于采用流体代替传统的固体质量块作为敏感载体,因而具有极其独特的性能,特别是高抗冲击性。采用ANSYS有限元分析软件,对微热对流角速度传感器的加热丝支撑层和检测丝支撑层进行动静态变形和应力计算,得出应力最大点,微加热丝支撑层的应力最大点在固支位置附近,检测丝支撑层的应力最大点在固支位置附近和内拐角处。在z方向有一定加速度载荷作用下,加热丝支撑层的最大应力比检测丝支撑层的最大应力大,更容易破坏。理论计算得到微热对流角速度传感器样品可抗冲击200000gn,经过抗冲击实验验证,微热对流角速度传感器样品在21200gn的冲击下仍完好无损,有极好的抗冲击性能。 相似文献
992.
993.
994.
995.
Eric Dauler Gregg Jaeger Antoine Muller A. Migdall A. Sergienko 《Journal of research of the National Institute of Standards and Technology》1999,104(1):1-10
An investigation is made of a recently introduced quantum interferometric method capable of measuring polarization mode dispersion (PMD) on sub-femtosecond scales, without the usual interferometric stability problems associated with such small time scales. The technique makes use of the extreme temporal correlation of orthogonally polarized pairs of photons produced via type-II phase-matched spontaneous parametric down-conversion. When sent into a simple polarization interferometer these photon pairs produce a sharp interference feature seen in the coincidence rate. The PMD of a given sample is determined from the shift of that interference feature as the sample is inserted into the system. The stability and resolution of this technique is shown to be below 0.2 fs. We explore how this precision is improved by reducing the length of the down-conversion crystal and increasing the spectral band pass of the system. 相似文献
996.
997.
Pro/ENGINEER功能强大,它的参数化设计理念深受用户青睐。目前它已成为我国的主流三维CAD软件。运用Pro/ENGINEER设计数字样机精确、效率高、经济性好,可避免许多不必要的浪费,并且可达到直观的、立体化的视觉效果,方便在制造过程中用户与厂家沟通,以便设计出用户更满意的产品。 相似文献
998.
This paper focuses on the design of non‐linear parametric controllers, around a nominal input/output trajectory of a discrete‐time non‐linear system. The main result provided herein is a relationship between the tracking performance of the closed‐loop control system in the neighbourhood of a nominal trajectory, and some local features (the first‐order linear approximations about the nominal trajectory) of the non‐linear mappings which characterize the plant and the feedback controller. Such a result can be used to predict the dynamic behaviour of the control system, and to reduce the computational complexity of the optimization task associated with the tuning of the parametric feedback controller. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
999.
The control of a novel aerospace actuator is considered, viz., an electro-hydrostatic actuator. It offers a high degree of maintainability and combat survivability of the aircraft's flight control system because all the actuator's elements are collocated. The quantitative feedback theory robust control method is used to design a controller for this novel actuator. Parameter variation, sensor noise and flight condition variability are explicitly considered in the design process. The resulting design is not only robust with respect to actuator parameter variations and flight condition and insensitive to sensor noise, but, in addition, the controlled actuator's phase lag is significantly reduced, thus improving the performance of the overall flight control system. © 1997 by John Wiley & Sons, Ltd. This paper was prepared under the auspices of the U.S. Government and it is therefore not subject to copyright in the U.S. 相似文献
1000.
T. Y. Ng Li Hua K. Y. Lam C. T. Loy 《International journal for numerical methods in engineering》1999,44(6):819-837
The parametric instability of truncated conical shells of uniform thickness under periodic edge loading is examined. The material considered is homogeneous and isotropic. This is the first instance that the Generalized Differential Quadrature (GDQ) method is used to study the effects of boundary conditions on the parametric instability in shells. The formulation is based on the dynamic version of Love's first approximation for thin shells. A formulation is presented which incorporates the GDQ method in the assumed‐mode method to reduce the partial differential equations of motion to a system of coupled Mathieu–Hill equations. The principal instability regions are then determined by Bolotin's method. Assumptions made in this study are the neglect of transverse shear deformation, rotary inertia as well as bending deformations before instability. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献