首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   79356篇
  免费   6041篇
  国内免费   1862篇
电工技术   4337篇
技术理论   9篇
综合类   4392篇
化学工业   12880篇
金属工艺   4889篇
机械仪表   4959篇
建筑科学   5393篇
矿业工程   2452篇
能源动力   2464篇
轻工业   5430篇
水利工程   1360篇
石油天然气   5024篇
武器工业   612篇
无线电   8794篇
一般工业技术   9560篇
冶金工业   4104篇
原子能技术   1170篇
自动化技术   9430篇
  2025年   252篇
  2024年   2029篇
  2023年   1708篇
  2022年   2520篇
  2021年   3482篇
  2020年   2869篇
  2019年   2550篇
  2018年   2477篇
  2017年   2666篇
  2016年   2538篇
  2015年   3290篇
  2014年   4092篇
  2013年   4597篇
  2012年   4822篇
  2011年   4997篇
  2010年   4452篇
  2009年   4012篇
  2008年   3880篇
  2007年   3783篇
  2006年   3884篇
  2005年   3258篇
  2004年   2075篇
  2003年   1819篇
  2002年   1740篇
  2001年   1396篇
  2000年   1543篇
  1999年   1789篇
  1998年   1428篇
  1997年   1211篇
  1996年   1211篇
  1995年   1047篇
  1994年   834篇
  1993年   556篇
  1992年   470篇
  1991年   361篇
  1990年   295篇
  1989年   241篇
  1988年   219篇
  1987年   137篇
  1986年   131篇
  1985年   84篇
  1984年   74篇
  1983年   56篇
  1982年   52篇
  1981年   49篇
  1980年   30篇
  1979年   17篇
  1977年   20篇
  1976年   37篇
  1975年   14篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
In this paper, we propose a new hard problem, called bilateral inhomogeneous small integer solution (Bi-ISIS), which can be seen as an extension of the small integer solution problem on lattices. The main idea is that, instead of choosing a rectangle matrix, we choose a square matrix with small rank to generate Bi-ISIS problem without affecting the hardness of the underlying SIS problem. Based on this new problem, we present two new hardness problems: computational Bi-ISIS and decisional problems. As a direct application of these problems, we construct a new lattice-based key exchange (KE) protocol, which is analogous to the classic Diffie- Hellman KE protocol. We prove the security of this protocol and show that it provides better security in case of worst-case hardness of lattice problems, relatively efficient implementations, and great simplicity.  相似文献   
22.
In the environment of space radiation, the high-energy charged particles or high-energy photons acting on a spacecraft can cause either temporary device degradation or permanent failure. The traditional probability model is difficult to obtain reliable estimation of unit radiation resistance performance with small samples. Considering that different products will change differently after high-energy particle radiation, we construct a model based on the gamma degradation process. This model can efficiently describe the law of unit radiation resistance variation with the total radiation dose levels under the effect of the total dose and displacement damage. Finally, the proposed model is used to assess the anti-radiation performance of the N-channel power MOSFET device STRH60N20FSY3 produced by STM to obtain average unit radiation resistance, survival probability, survival function, etc.  相似文献   
23.
The viscous damping coefficient(VDC) of hydraulic actuators is crucial for system modeling,control and dynamic characteristic analysis.Currently,the researches on hydraulic actuators focus on behavior assessment,promotion of control performance and efficiency.However,the estimation of the VDC is difficult due to a lack of study.Firstly,using two types of hydraulic cylinders,behaviors of the VDC are experimentally examined with velocities and pressure variations.For the tested plunger type hydraulic cylinder,the exponential model B=αυ~(-β),(α0,β0)or B=α_1e~(-β_1υ)+α_2e~(-β_2υ)(α_1,α_20,β_1,β_20),fits the relation between the VDC and velocities for a given pressure of chamber with high precision.The magnitude of the VDC decreases almost linearly under certain velocities when increasing the chamber pressure from 0.6 MPa to 6.0 MPa.Furthermore,the effects of the chamber pressures on the VDC of piston and plunge type hydraulic cylinders are different due to different sealing types.In order to investigate the VDC of a plunger type hydraulic actuator drastically,a steady-state numerical model has been developed to describe the mechanism incorporating tandem seal lubrication,back-up ring related friction behaviors and shear stress of fluid.It is shown that the simulated results of VDC agree with the measured results with a good accuracy.The proposed method provides an instruction to predict the VDC in system modeling and analysis.  相似文献   
24.
25.
26.
Based on the quantum Zeno dynamics, a scheme is presented to implement a Toffoli gate of three separated superconducting qubits (SQs) by one step. Three separated SQs are connected by two resonators. The scheme is insensitive to the resonator decay because the Zeno subspace does not include the state of the resonators being excited. Numerical simulations indicate that the scheme is robust to the fluctuation of the parameters and the Toffoli gate can be implemented with high fidelity.  相似文献   
27.
28.
29.
30.
马骏  陈妍曙 《小水电》2011,(3):51-52
以小型水利工程项目划分为对象,从质量监督确认工作角度出发,根据小型水利工程的特点,探讨在现有规程下针对实际不同工程的恰当的项目划分方式,以利参建各方更好地控制工程质量。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号