全文获取类型
收费全文 | 385136篇 |
免费 | 13447篇 |
国内免费 | 6334篇 |
专业分类
电工技术 | 12204篇 |
技术理论 | 9篇 |
综合类 | 8805篇 |
化学工业 | 62883篇 |
金属工艺 | 22790篇 |
机械仪表 | 18460篇 |
建筑科学 | 13639篇 |
矿业工程 | 7289篇 |
能源动力 | 7392篇 |
轻工业 | 18972篇 |
水利工程 | 6806篇 |
石油天然气 | 20283篇 |
武器工业 | 1073篇 |
无线电 | 35349篇 |
一般工业技术 | 81465篇 |
冶金工业 | 39373篇 |
原子能技术 | 13510篇 |
自动化技术 | 34615篇 |
出版年
2022年 | 6275篇 |
2021年 | 8517篇 |
2020年 | 6486篇 |
2019年 | 6282篇 |
2018年 | 9554篇 |
2017年 | 10271篇 |
2016年 | 10091篇 |
2015年 | 8202篇 |
2014年 | 11753篇 |
2013年 | 17835篇 |
2012年 | 15809篇 |
2011年 | 17968篇 |
2010年 | 14973篇 |
2009年 | 15597篇 |
2008年 | 15603篇 |
2007年 | 14743篇 |
2006年 | 12959篇 |
2005年 | 11219篇 |
2004年 | 9638篇 |
2003年 | 9386篇 |
2002年 | 9353篇 |
2001年 | 8740篇 |
2000年 | 8140篇 |
1999年 | 7151篇 |
1998年 | 9436篇 |
1997年 | 7674篇 |
1996年 | 6110篇 |
1995年 | 5123篇 |
1994年 | 4647篇 |
1993年 | 4537篇 |
1992年 | 4070篇 |
1991年 | 4039篇 |
1990年 | 4096篇 |
1989年 | 3937篇 |
1988年 | 3741篇 |
1987年 | 3681篇 |
1986年 | 3500篇 |
1985年 | 3617篇 |
1984年 | 3516篇 |
1983年 | 3409篇 |
1981年 | 3303篇 |
1980年 | 3336篇 |
1979年 | 3565篇 |
1978年 | 3783篇 |
1977年 | 3772篇 |
1976年 | 4225篇 |
1975年 | 3521篇 |
1974年 | 3591篇 |
1973年 | 3613篇 |
1972年 | 3305篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
The article investigates the state of stress and strain of the surface of an elastic cylindrical shell whose outer part is subjected to the effect of an incident acoustic wave. A qualitative and quantitative analysis of the state of strain of the surface is carried out and recommendations are given for optimizing the functional purpose of the shell and minimizing the arising stresses.Translated from Problemy Prochnosti, No. 4, pp. 43–47, April, 1991. 相似文献
132.
V. I. Gorynin 《Strength of Materials》1991,23(5):524-527
The influence of the level of defectiveness of design and service origin (grooves and cracks) of a fastener and an impact specimen on the accuracy of determination of the allowable values of the ductile-to-brittle transition temperature is investigated. An evaluation of the allowable ductile-to-brittle transition temperatures making it possible to impose more soundly based requirements for effectiveness of the material in the stages of design, production, and service in relation to the production condition of the steel, the level of defectiveness of the fastener, and the specified operating life of the threaded joint is proposed.Translated from Problemy Prochnosti, No. 5, pp. 35–37, May, 1991. 相似文献
133.
J Byrne S Kienzle D Johnson G Duke V Gannon B Selinger J Thomas 《Water science and technology》2006,53(10):327-334
Long-term trends in alpine and prairie snow pack accumulation and melt are affecting streamflow within the Oldman River Basin in southern Alberta, Canada. Unchecked rural and urban development also has contributed to changes in water quality, including enhanced microbial populations and increased waterborne pathogen occurrence. In this study we look at changing environment within the Oldman River Basin and its impact on water quality and quantity. The cumulative effects include a decline in net water supplies, and declining quality resulting in increased risk of disease. Our data indicates that decreases in the rate of flow of water can result in sedimentation of bacterial contaminants within the water column. Water for ecosystems, urban consumption, recreation and distribution through irrigation is often drawn from waterholding facilities such as dams and weirs, and concern must be expressed over the potential for contaminate build-up and disproportionate potential of these structures to pose a risk to human and animal health. With disruption of natural flow rates for water resulting from environmental change such as global warming and/or human intervention, increased attention needs to be paid to use of best management practices to protect source water supplies. 相似文献
134.
M.G. Pujar N. Parvathavarthini Sidhartha S. Jena B.V.R. Tata R.K. Dayal H.S. Khatak 《Journal of Materials Engineering and Performance》2008,17(6):793-801
In the present work 316LN as well as 316 stainless steel (SS) coupons each of dimensions (0.025 × 0.018 × 0.006 m3) in well-polished condition were used as two nominal electrodes which were immersed in the aerated solution of 0.5 M NaCl.
Correlated current and potential electrochemical noise (EN) signals were collected at 1 Hz sampling frequency for 1 h daily
over a period of 30 days. The detrended EN data were used to calculate the noise resistance (R
N) as well as the spectral noise resistance at zero frequency (R
SNo) values and other statistical parameters. To study the nature of pits and distribution of their diameters as well as depths,
extensive observations of the pitted and the blank specimens were carried out using Confocal Laser Scanning Microscopy (CLSM).
The current and the potential records of the two alloys showed distinct differences in their corrosion behavior. It was observed
that within less than 4 h of immersion, 316SS showed signals indicative of unstable pitting and onset of stable pitting was
noticed after 48 h of exposure. However, until about 24 h, 316LN showed just the random signals and unstable pitting was observed
after 28 h. The signals clearly indicated continuous growth of the stable pits in 316SS as against the repassivation of the
unstable pits in 316LN after 7 days exposure. It was observed that R
N values showed a continuous decrease in the case of 316SS, but were quite stable in the case of 316LN over the exposure period.
Concurrent to these observations it was observed that 316SS specimen was extensively pitted. The frequency distributions of
pit diameters as well pit depths were observed to be highest at 10-20 μm and 5-10 μm, respectively. However, pits with as
large as 70-80 μm diameter and as deep as 20-25 μm too were observed. No pits were observed in case of 316LN even after 30 days
of exposure, an observation that corroborates well with the stable R
N values. Thus, in the present investigation, the long-term tests using EN technique coupled with CLSM studies conclusively
prove that many unstable pits initiated in 316SS turn into stable ones resulting in insidious localized corrosion attack whereas
the unstable pits initiated in 316LN get passivated in the simulated coastal environment. 相似文献
135.
The switchable optical properties of Pd-protected RCo2-type Ho0.6Mm0.4Co2 alloy thin films have been investigated in a KOH electrolyte. The reversible optical switching has been carried out simultaneously by measuring transmitted light through the thin film during electrochemical charging–discharging of hydrogen. The dependence of switching speed and cyclic durability of the film on the charging and discharging current density as well as concentration of KOH electrolyte has been studied. In addition, cyclic voltammetric measurements have been performed to examine the hydride formation and decomposition reactions. 相似文献
136.
Filled fibrous sorbents modified with transition metal ferro- and ferricyanides capable to recover americium(III) and rare-earth metals(III) from nitric acid solutions were prepared. The most complete and rapid recovery is attained on complex-forming and cation-exchange sorbents (as filled fibrous materials) saturated with nickel ions. The sorbents are characterized by good kinetic properties and can be used for recovery of the above metals. 相似文献
137.
V. Ya. Sakulin V. P. Migal’ A. P. Margishvili V. V. Bulin 《Refractories and Industrial Ceramics》2008,49(5):354-358
A range of refractories is presented for handling steel outside a furnace, which are produced by the Borovichi Refractories
Corporation. The refractory characteristics and working features are given.
Translated from Novye Ogneupory, No. 9, pp. 29–35, September, 2008. 相似文献
138.
Production methods used to prepare graphite crucibles with high operating properties are considered: use as a filler of good
graphitizing acicular coke, vibration molding of the original coke mix, use of production cycles for impregnation with medium
temperature coal-tar pitch — firing, firing of compacted billets in metal containers, graphitization of fired billets in graphite
cylinders. The last two production methods make it possible to reduce the temperature drop throughout the volume of a billet
during heat treatment, and as a consequence to reduce crack development to a minimum as a result of reducing thermal stresses.
All of the production methods recommended may be entirely accomplished in existing electrode plants and may be used to increase
markedly the quality crucible graphite. It is possible to achieve a quality for these materials at the best world level.
Translated from Novye Ogneupory, No. 8, pp. 28–33, August 2008. 相似文献
139.
V. V. Slovikovskii 《Refractories and Industrial Ceramics》2008,49(3):216-218
Research results are given on magnesian box-type components in the tuyere belt of horizontal converters at Ufalei Nickel Corporation.
The purpose has been to eliminate the zoning in them by impregnation with nickel or copper mattes to relieve thermal stresses
during use. Components impregnated with matte show improved physicomechanical and thermophysical properties. A technology
has been developed and tested for impregnating standard components under conditions found at Ufalei Nickel Corporation.
Translated from Novye Ogneupory, No. 5, pp. 44–47, May, 2008. 相似文献
140.
L. M. Aksel’rod V. I. Rumyantsev N. Yu. Korableva N. V. Belykh Ya. G. Dyatlova 《Refractories and Industrial Ceramics》2008,49(2):116-119
Technology is developed for preparing refractory components made of partially stabilized zirconium dioxide using an isostatic
compaction press. Technology is provided for manufacturing dispensing nozzles using combined and separately stabilized zirconium
dioxide, and also indices of the refractories obtained and imported materials are compared.
__________
Translated from Novye Ogneupory, No. 3, pp. 127–131, March 2008. 相似文献