全文获取类型
收费全文 | 25237篇 |
免费 | 1920篇 |
国内免费 | 859篇 |
专业分类
电工技术 | 1327篇 |
技术理论 | 1篇 |
综合类 | 1381篇 |
化学工业 | 4511篇 |
金属工艺 | 1325篇 |
机械仪表 | 1319篇 |
建筑科学 | 1865篇 |
矿业工程 | 581篇 |
能源动力 | 886篇 |
轻工业 | 1635篇 |
水利工程 | 340篇 |
石油天然气 | 1344篇 |
武器工业 | 118篇 |
无线电 | 3109篇 |
一般工业技术 | 3241篇 |
冶金工业 | 1440篇 |
原子能技术 | 314篇 |
自动化技术 | 3279篇 |
出版年
2024年 | 84篇 |
2023年 | 408篇 |
2022年 | 702篇 |
2021年 | 1029篇 |
2020年 | 720篇 |
2019年 | 674篇 |
2018年 | 695篇 |
2017年 | 809篇 |
2016年 | 758篇 |
2015年 | 923篇 |
2014年 | 1240篇 |
2013年 | 1586篇 |
2012年 | 1574篇 |
2011年 | 1723篇 |
2010年 | 1400篇 |
2009年 | 1446篇 |
2008年 | 1345篇 |
2007年 | 1241篇 |
2006年 | 1350篇 |
2005年 | 1164篇 |
2004年 | 841篇 |
2003年 | 761篇 |
2002年 | 761篇 |
2001年 | 542篇 |
2000年 | 524篇 |
1999年 | 602篇 |
1998年 | 573篇 |
1997年 | 463篇 |
1996年 | 446篇 |
1995年 | 345篇 |
1994年 | 281篇 |
1993年 | 190篇 |
1992年 | 174篇 |
1991年 | 117篇 |
1990年 | 92篇 |
1989年 | 72篇 |
1988年 | 88篇 |
1987年 | 48篇 |
1986年 | 44篇 |
1985年 | 25篇 |
1984年 | 33篇 |
1983年 | 19篇 |
1982年 | 27篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 15篇 |
1977年 | 4篇 |
1976年 | 9篇 |
1975年 | 4篇 |
1965年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
针对实时监控系统中的运行设备或装置的异常报警信息,设计了基于GSM无线通讯的微机监测系统,实现了多故障远程短信息报警功能,介绍了系统的软硬件设计及主要功能;经应用测试,系统具有宴时性强、稳定性高、投入成本低等特点,能将信息同时发送至多个移动通信终端,已成功应用于农业温室大棚监控系统的实时故障报警,系统也可方便地应用于工厂生产线、金融、交通及家庭安全等方面的远程监测. 相似文献
102.
The objective of this study is to develop a tri-rotor flying robot, which adopts the Y-shaped three-rotor structure. In order to balance the yaw torque produced by the three rotors, the RC servomotor and linkage is installed on the tail axis in order to improve the angle of the rolling axis of the tail motor. Moreover, through the torque generated by the horizontal component of the lift from the inclined motor on the tail axis, it balances the yaw torque of the three rotors. The dynamic equations of the tri-rotor flying robot are determined in this paper. The relationship between motor thrust, angular acceleration, and voltage input was also studied in this research. In order to study the effect of control parameters on the flight stability completely, this study develops a universal stability experimental platform to help tuning the control parameters safely. Based on this, the tri-rotor flying robot can rapidly change flying gesture and avoid oscillation. Finally, we conducted some indoor and outdoor flight tests. From the experimental results, the tri-rotor flying robot can fly and hover stably in the sky. 相似文献
103.
We present the path-planning techniques of the fire-escaping system for intelligent building, and use multiple mobile robots to present the experimental scenario. The fire-escaping system contains a supervised computer, an experimental platform, some fire-detection robots and some navigation robots. The mobile robot has the shape of a cylinder, and its diameter, height and weight are 10?cm, 15?cm and 1.5?kg, respectively. The mobile robot contains a controller module, two DC servomotors (including drivers), three IR sensor modules, a voice module and a wireless RF module. The controller of the mobile robot acquires the detection signals from reflective IR sensors through I/O pins and receives the command from the supervised computer via wireless RF interface. The fire-detection robot carries the flame sensor to detect fire sources moving on the grid-based experiment platform, and calculates the more safety escaping path using piecewise cubic Bezier curve on all probability escaping motion paths. Then the user interface uses A* searching algorithm to program escaping motion path to approach the Bezier curve on the grid-based platform. The navigation robot guides people moving to the safety area or exit door using the programmed escaping motion path. In the experimental results, the supervised computer programs the escaping paths using the proposed algorithms and presents movement scenario using the multiple smart mobile robots on the experimental platform. In the experimental scenario, the user interface transmits the motion command to the mobile robots moving on the grid-based platform, and locates the positions of fire sources by the fire-detection robots. The navigation robot guides people leaving the fire sources using the low-risk escaping motion path and moves to the exit door. 相似文献
104.
A.c. impedance has been determined at room temperature on hydrogen-free and hydrogen-charged passivating oxide films on aluminium in 0.05m Na2SO4 solution. Analysis of the impedance data enabled a clear distinction between the capacitance and inductance of the hydrogen-free oxide film and those of the hydrogen-charged oxide film to be made. The changes in capacitance and inductance by hydrogen-charging into the oxide films are discussed in relation to the compositional change from -Al2O3 to hydrated alumina. 相似文献
105.
Numerical and asymptotic solutions are developed to the equations governing large torsional, axisymmetric deformation of rubberlike shells of revolution. The shell equations include large-strain geometric and material nonlinearities, transverse shear deformation, transverse normal stress and strain, and torsion. Both analyses allow ready incorporation of different strain-energy density functions. In the asymptotic analysis, the interior solution corresponds to that of nonlinear membrane theory and contains a primary boundary layer. The edge-zone solution gives a secondary boundary layer that, for large strain, divides into a bending-twisting moment component and a torsional-membrane component. The boundary layer behavior is illustrated for a clamped neo-Hookean cylinder subjected to internal pressure and axial torque.List of symbols Latin symbols
a
General dependent variable
-
a
(mn)
Terms of the asymptotic expansion of a(x)
-
b
Characteristic length
-
c
Scalar curvature components in the normal direction
-
c
, c
,
, c
Cosine of
, respectively
-
C
Material constant with units of a Young's modulus
-
e
i
Deformed local orthonormal basis associated with (, s, n)(x
1, x
2, x
3) coordinates
-
Undeformed cylindrical coordinate basis
-
Intermediate coordinate basis
-
g
Shear correction factor
-
H
Horizontal stress resultants
-
l
1
Strain invariant
-
k
Scalar curvature components
-
L
Undeformed cylinder length
-
M
Moment resultants
-
M
r, M
, M
z
Moment resultant components in the basis
-
N
Membrane stress resultants
-
p
Internal pressure
-
p
H, p
v
Horizontal and vertical surface loads, respectively
-
p
i
Thickness-averaged surface tractions
-
Q
Transverse shear stress resultants
-
, r
Radial coordinate prior to, after deformation
-
R
Undeformed cylinder radius
-
, s
Meridional coordinate prior to, after deformation
-
s
, s
x,
, s
Sine of
, respectively
-
, S
Reference surface prior to, after deformation
-
S
1, S
2
Shear stress resultants parallel to the reference surface
-
S
3
Average transverse normal stress resultant
-
t
Undformed shell thickness
-
T
Axial torque
-
V
Vertical stress resultants
-
w
Two-dimensional strain-energy density function
-
w
n
Terms in expansion for w
-
W
Three-dimensional strain-energy density function
-
x
Undeformed axial coordinate in cylinder
-
, z
Axial coordinate prior to, after deformation 相似文献
106.
根据NCBI已公布的花斑无须鲶全基因组序列,利用MISA软件对花斑无须鲶全基因组的6种完整型微卫星进行筛选并分析其分布特征. 结果如下:在花斑无须鲶全基因组(约1.03Gb)中符合条件的微卫星序列共336 037个,丰度为326个/Mb. 微卫星总长度为7 720 686 bp,占花斑无须鲶全基因组的0.75%. 其中二碱基类型的微卫星数目最多,为145 318个,占微卫星总数的43.24%,其次分别为单碱基(37.12%)、三碱基(11.00%)、四碱基(7.39%)、五碱基(1.04%)和六碱基(0.21%). 花斑无须鲶全基因组微卫星中的优势碱基类别按照数量从高到低排列依次为A、AC、AG、AT、AAT、AAAT、TATC、AAG、AAC和TGA,共有305 243个,占微卫星总数的 90.84%,A、T碱基在微卫星中占绝对优势. 相似文献
107.
Dongmei Hu Jin Du Guosheng Su Zhenyun Lu Chongyan Zhang Xiangmin Kong Chonghai Xu 《International Journal of Applied Ceramic Technology》2021,18(4):1222-1234
The hardness and toughness of regenerated cemented carbides, in general, are contradictory. Therefore, it is critical to explore regenerated cemented carbides with both high hardness and high toughness. In this study, regenerated WC-8-wt% Co cemented carbide with SiC nanowhisker were prepared by low-pressure sintering. The influence of SiCw contents on the microstructure and mechanical properties of regenerated WC-8-wt% Co cemented carbide was investigated. The results indicated that the hardness, density, flexural strength, and fracture toughness of regenerated cemented carbide first increased and then decreased with the addition of SiCw. The Vickers hardness, density, flexural strength, and fracture toughness could reach 1575 HV, 14.6 g/cm3, 2204 MPa, 16.85 MPa·m1/2, respectively, with SiCw content 0.5 wt%, which were increased by 14.4%, 0.7%, 12.2%, and 17.3%, respectively, when compared with the regenerated cemented carbide without SiCw. The lowest friction coefficient and the best wear resistance could be also reached when 0.5-wt% SiCw was added. The fracture mechanism of the regenerated cemented carbide contained both transgranular and intergranular fracture through the microscopic observation of fracture surface via scanning electron microscope. 相似文献
108.
109.
介绍了铂铑包覆钼合金搅拌器的结构与技术要求,以及搅拌器的制作与使用效果。研制结果表明,国产搅拌器达到了日本同类产品的水平。 相似文献
110.
针对模拟移动床(SMB)综合速率模型,采用有限元法和正交配点法分别对柱向和颗粒径向模型进行离散化,利用MatLab ODE求解器对SMB过程进行数值求解。通过仿真,验证了该方法的可行性。 相似文献