全文获取类型
收费全文 | 1595篇 |
免费 | 42篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 43篇 |
综合类 | 11篇 |
化学工业 | 136篇 |
金属工艺 | 61篇 |
机械仪表 | 37篇 |
建筑科学 | 16篇 |
矿业工程 | 25篇 |
能源动力 | 2篇 |
轻工业 | 13篇 |
水利工程 | 50篇 |
石油天然气 | 43篇 |
无线电 | 156篇 |
一般工业技术 | 241篇 |
冶金工业 | 634篇 |
原子能技术 | 55篇 |
自动化技术 | 119篇 |
出版年
2022年 | 12篇 |
2021年 | 20篇 |
2020年 | 18篇 |
2019年 | 27篇 |
2018年 | 30篇 |
2017年 | 36篇 |
2016年 | 39篇 |
2015年 | 38篇 |
2014年 | 32篇 |
2013年 | 29篇 |
2012年 | 34篇 |
2011年 | 48篇 |
2010年 | 34篇 |
2009年 | 32篇 |
2008年 | 37篇 |
2007年 | 45篇 |
2006年 | 42篇 |
2005年 | 63篇 |
2004年 | 32篇 |
2003年 | 25篇 |
2002年 | 42篇 |
2001年 | 29篇 |
2000年 | 23篇 |
1999年 | 28篇 |
1998年 | 158篇 |
1997年 | 91篇 |
1996年 | 70篇 |
1995年 | 35篇 |
1994年 | 41篇 |
1993年 | 19篇 |
1992年 | 9篇 |
1991年 | 23篇 |
1990年 | 14篇 |
1989年 | 11篇 |
1988年 | 23篇 |
1987年 | 17篇 |
1986年 | 16篇 |
1985年 | 18篇 |
1982年 | 15篇 |
1981年 | 15篇 |
1980年 | 16篇 |
1978年 | 15篇 |
1977年 | 39篇 |
1976年 | 61篇 |
1974年 | 14篇 |
1972年 | 14篇 |
1971年 | 8篇 |
1970年 | 16篇 |
1969年 | 9篇 |
1966年 | 10篇 |
排序方式: 共有1642条查询结果,搜索用时 15 毫秒
1.
2.
3.
In the present investigation, the process model developed in Part I has been applied to evaluate the microstructure and strength
evolution during active brazing of ceramics. As a starting point, reaction-layer growth is assumed to occur isothermally with
no restrictions in the supply of reactive element. Different kinds of diagrams are then constructed to show how specific process
variables (e.g. the heating and cooling period, the limiting layer thickness, and the diffusion mechanism) affect the growth
kinetics. It is concluded that the key to improved joint properties lies in control of the reaction-layer thickness through
optimization of the brazing conditions, and an illustration of this is given.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
4.
KL Gatford TP Fletcher IJ Clarke PC Owens KJ Quinn PE Walton PA Grant BJ Hosking AR Egan EN Ponnampalam 《Canadian Metallurgical Quarterly》1996,74(6):1314-1325
The effects of sex and age on patterns of circulating somatotropin (ST) concentration and plasma IGF-I, IGF-II, insulin, and IGF binding protein-3 (IGFBP-3) were studied in ram, wether, and ewe lambs (n = 7 or 8) sampled at mean ages of 81 (I1) and 158 d (I2). Between 81 and 158 d of age, rams grew more rapidly than wethers (P < .01), and wethers grew more rapidly than ewes (P < .01). The sex differences in growth were reflected in empty body weight at slaughter: rams > wethers > ewes (P < .05). Mean plasma ST concentrations, ST pulse amplitude, and integrated plasma ST concentrations were greater (P < .05) in rams than in ewes at I1 and I2. Characteristics of the ST plasma profile in wethers were generally intermediate between those of rams and ewes. The interpulse interval was greater in ewes than in wethers at I2. The IGF-I and IGFBP-3 concentrations were greater in rams than in ewes at both sampling times. Plasma IGF-II was greater in ewes than in rams at I2. Mean plasma ST was approximately two thirds less at I2 than at I1 regardless of sex. Mean plasma ST and IGF-I at both ages were positively correlated with growth. Mean plasma ST at I2 was negatively correlated with fatness at slaughter. Sex and age significantly affected patterns of circulating ST and concentrations of IGF-I and IGFBP-3 in prepubertal growing lambs, under conditions for which growth rates and composition were also sexually dimorphic. 相似文献
5.
Borodina I. A. Zaitsev B. D. Kuznetsova I. E. Teplykh A. A. Shurygin V. V. 《Technical Physics Letters》2003,29(9):781-783
The conditions for hybridization of the zero-order and high-order acoustic waves propagating in a piezoelectric crystal plate have been studied. The dependence of the phase velocity of the hybrid waves on the parameter hf (h is the plate thickness and f is the wave frequency) is established for the potassium niobate and lithium niobate plates possessing various crystallographic orientations and conductivities. It is found that hybridization takes place when the conductivity of a thin surface layer exceeds a certain critical value, which can vary within broad limits depending on the plate material and orientation. The degree of dispersive repulsion of the coupled modes grows with increasing electromechanical coupling coefficient. 相似文献
6.
7.
Investigation of the morphology of ganglion cells in the cat retina has shown that a remarkable reduction in the number of dendritic spines and branches occurs during development of the alpha and beta cell classes. To learn whether dendritic remodelling represents a generalized mechanism of mammalian retinal ganglion cell development, we have examined the morphology of ganglion cells in the retina of the developing rat. The present study has concentrated on type II cells, which retain a great number of dendritic spines and branches in the adult and comprise a large proportion of the population of rat retinal ganglion cells. To reveal fine dendritic and axonal processes, Lucifer yellow was injected intracellularly in living retinae maintained in vitro. Size and complexity of the dendritic trees were found to increase rapidly during an initial stage of development lasting from late fetal life until approximately postnatal day 12 (P12). Dendrites and axons of immature ganglion cells expressed several transient morphological features comprising an excessive number of dendritic branches and spine-like processes, and short, delicate axonal sidebranches. The following developmental stage was characterized by a remarkable decrease in the morphological complexity of retinal ganglion cells and a slowed growth of their dendritic fields. The number of dendritic branches and spines of types I and II retinal ganglion cells declined after P12 to reach a mature level by the end of the first postnatal month. Thus, even cells that retain a highly complex dendritic tree into the adult state undergo extensive remodelling. These results suggest that regressive modifications at the level of the dendritic field constitute a generalized mechanism of maturation in mammalian retinal ganglion cells. 相似文献
8.
E. Kh. Shakhpazov I. G. Rodionova O. N. Baklanova A. I. Zaitsev D. A. Burko A. D. Gorin S. D. Zinchenko 《Metallurgist》2006,50(1-2):65-70
It is shown that the corrosion resistance of automobile sheet can be improved by ensuring that steels of this type have a
low content of corrosion-active nonmetallic inclusions (CANI). The main mechanisms responsible for the formation of CANI in
automobile sheet have been established, and recommendations have been developed to reduce their concentration in this product
• optimize the deoxidation processes that are used by ensuring that the proportions of the additions made to the steel are
consistent with the composition of the ladle slag and that certain key temperature-time parameters of these processes are
maintained
• control the composition of the ladle slag to prevent the formation of solid phases in the slag and their transfer to the
metal; certain conditions must also be observed in the argon blow and the introduction of the addtions.
Use of the above recommendations to make automobile sheet and tube steels cleaner with respect to their content of CANI and
thus help optimize out-of-furnace treatments at metallurgical and pipe plants will make it possible to improve the corrosion
resistance of metal products used in automotive manufacturing.
__________
Translated from Metallurg, No. 2, pp. 45–48, February, 2006. 相似文献
9.
10.
V. G. Zaitsev 《Strength of Materials》1994,26(3):216-222
A study is made of the distribution law for the amplitudes of random stresses and associated parameters. A theoretical law is proposed to describe an empirical distribution, and a comparison is made between the deviations of the endurances corresponding to these laws and the coefficient of variation of random endurance values. An empirical formula is obtained to determine maximum stress amplitudes.Translated from Problemy Prochnosti, No. 3, pp. 63–70, March, 1994. 相似文献