全文获取类型
收费全文 | 748篇 |
免费 | 21篇 |
国内免费 | 24篇 |
专业分类
电工技术 | 24篇 |
综合类 | 35篇 |
化学工业 | 57篇 |
金属工艺 | 75篇 |
机械仪表 | 115篇 |
建筑科学 | 96篇 |
矿业工程 | 54篇 |
能源动力 | 23篇 |
轻工业 | 6篇 |
水利工程 | 8篇 |
石油天然气 | 16篇 |
武器工业 | 25篇 |
无线电 | 24篇 |
一般工业技术 | 101篇 |
冶金工业 | 26篇 |
原子能技术 | 19篇 |
自动化技术 | 89篇 |
出版年
2023年 | 4篇 |
2022年 | 21篇 |
2021年 | 17篇 |
2020年 | 13篇 |
2019年 | 7篇 |
2018年 | 13篇 |
2017年 | 18篇 |
2016年 | 15篇 |
2015年 | 30篇 |
2014年 | 27篇 |
2013年 | 41篇 |
2012年 | 60篇 |
2011年 | 45篇 |
2010年 | 32篇 |
2009年 | 43篇 |
2008年 | 37篇 |
2007年 | 52篇 |
2006年 | 43篇 |
2005年 | 40篇 |
2004年 | 21篇 |
2003年 | 40篇 |
2002年 | 30篇 |
2001年 | 15篇 |
2000年 | 20篇 |
1999年 | 22篇 |
1998年 | 21篇 |
1997年 | 15篇 |
1996年 | 15篇 |
1995年 | 12篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1984年 | 2篇 |
排序方式: 共有793条查询结果,搜索用时 15 毫秒
81.
The dynamic fracture toughness K1d and J1d, arrest toughness K1a and Charpy V-notched impact toughness (CVN) of a pipeline steel, X70, were studied at different temperatures. It was found that fracture toughness was strongly affected by temperature and loading rate. The fracture toughness decreases with decreasing temperature from 213 to193 K and increasing loading rate from
to
. At constant temperatures, only increasing loading rate can induce the transition from ductile to brittle. There exists a fracture transition caused by loading rate. Through thermal activation analysis, a quantitative relationship has been derived: . It can describe the fracture process at different temperatures and loading rates. At a loading rate of
, the relationship can predict arrest toughness well. It provides the possibility of measuring arrest toughness with small size specimen. An empirical equation has been derived: CVN=4.84×106T−2.8K1d(K1a), which correlates K1d and K1a with CVN in one equation. This means that we can calculate K1d and K1a when we get CVN. 相似文献
82.
本文介绍5MW 低功率堆(5MW LPR)首次装料及首次临界试验。由于本堆使用有燃耗的燃料元件,铍作反射层,光激中子成为强的内中子源,其强度随着燃料元件装量的增加而增加。因此,装料时元件法外堆结果有较大的涨落,但整个装料过程是安全的。在次临界下,做了控制棒相对效率曲线,然后,提升控制棒,进行计数外推,达到首次临界。 相似文献
83.
Electric Loading Simulation System for Missile Wings and Rudders 总被引:1,自引:0,他引:1
The design and the realization of missile wings and rudders loading simulation system based on digital signal processor (DSP) TMS320LF2407 and direct torque control (DTC) servo driver ACS600 are discussed. The structure and opration principle for the system are presented. Speediness and elimination of superabundant torque are two key difficulties for electric loading simulation system. The method which can eliminate the superabundant torque is researched. Test results show the airflow resistance when missile wings and rudders are spreading can be rapidly simulated with high accuracy. 相似文献
84.
梁新邦 《理化检验(物理分册)》2006,42(8):396-400
对圆柱形对中传感器试样横截面圆周弯曲应变的分布进行了理论分析,导出了最大弯曲应变的表示通式,使多点测量方式的加载同轴度达到了理论上的统一表达。分别提供了表示最大弯曲应变方位角、净试验机最大弯曲应变和净试样弯曲应变的通式。指出了国外文献关于净试验机弯曲分量表示式的错误。 相似文献
85.
热壁加氢反应器是大型化工容器,在铁路运输过程中需使用特种车辆并要进行装载加固。本介绍我公司为抚顺石化总厂制造的热壁加氢反应器的铁路运输用特种车辆的装载加固设计方案。 相似文献
86.
机器人六分量腕力传感器加载试验台系统误差分析 总被引:5,自引:2,他引:3
简要介绍了对机器人六分量腕力传感器进行标定的方法和装置,对目前使用的一种加载试验台的系统误差进行分析,提出了对各种误差的分析方法,导出相应的计算公式,为制定有关的产品检测标准和设计标准检测设备提供参考。 相似文献
87.
Nathaniel B. Weston James T. Hollibaugh 《The Science of the total environment》2009,407(10):3347-3356
We used more than thirty years of water quality monitoring data collected by the United States Geological Survey at several stations in the Altamaha River and its tributaries to examine the relationship between population density, agricultural land use, and nutrient export from the watershed. Population densities in the Altamaha River watershed increased during the study period, most notably in the upper watershed near metropolitan Atlanta, while agricultural land use declined throughout the watershed. NOx, TN and P in rivers were related to human population densities, while OC and NH4+ concentrations in rivers were apparently related to agricultural land use. A general pattern of increasing NOx and TN and decreasing NH4+, P and OC over time throughout the watershed reflected changing population and land use. The overall average load from the Altamaha River to the coastal zone during the study period was 1.1, 5.6, 16.9, 0.9 and 262 kmol km− 2 yr− 1, delivering 40, 197, 596, 30, and 9213 · 106 mol yr− 1 of NH4+, NOx, TN, P and OC, respectively, to the coastal zone. The nutrient export patterns suggest that N and P loading to rivers in the Altamaha River watershed was greatest in the upper watershed where high population densities were found, and in-stream processing, dilution, and only moderate inputs during transit through the lower watershed resulted in relatively low export from the watershed to coastal waters. 相似文献
88.
Determination of performance of non-ideal aluminized explosives 总被引:1,自引:0,他引:1
Keshavarz MH Mofrad RT Poor KE Shokrollahi A Zali A Yousefi MH 《Journal of hazardous materials》2006,137(1):83-87
Non-ideal explosives can have Chapman-Jouguet (C-J) detonation pressure significantly different from those expected from existing thermodynamic computer codes, which usually allows finding the parameters of ideal detonation of individual high explosives with good accuracy. A simple method is introduced by which detonation pressure of non-ideal aluminized explosives with general formula C(a)H(b)N(c)O(d)Al(e) can be predicted only from a, b, c, d and e at any loading density without using any assumed detonation products and experimental data. Calculated detonation pressures show good agreement with experimental values with respect to computed results obtained by complicated computer code. It is shown here how loading density and atomic composition can be integrated into an empirical formula for predicting detonation pressure of proposed aluminized explosives. 相似文献
89.
Katsushi Furutani Noriyuki Ohguro Nguyen Trong Hieu Takashi Nakamura 《International Journal of Machine Tools and Manufacture》2002,42(13)
This paper deals with an in-process measurement method for topography change of a grinding wheel, which can apply to wet grinding. A pressure sensor is set beside a grinding wheel with a small gap. When grinding fluid is dragged into the gap, hydrodynamic pressure, which corresponds to the gap length and the topography, can be measured. This method is applied to a cylindrical grinding machine. No electromagnetic properties of a workpiece and a grinding wheel affect measured results. The pressure is decreased with the increase of the gap length when the grinding fluid is supplied in the tangential direction of the grinding wheel. Spectra of the pressure are measured with an FFT analyzer. Higher frequency components are increased with the progress of grinding because of turbulent flow. Loading and dulling of a grinding wheel can be detected by the proposed method as well as its wear. 相似文献
90.