全文获取类型
收费全文 | 14007篇 |
免费 | 1012篇 |
国内免费 | 687篇 |
专业分类
电工技术 | 1272篇 |
综合类 | 796篇 |
化学工业 | 3296篇 |
金属工艺 | 1944篇 |
机械仪表 | 988篇 |
建筑科学 | 432篇 |
矿业工程 | 231篇 |
能源动力 | 1325篇 |
轻工业 | 410篇 |
水利工程 | 68篇 |
石油天然气 | 241篇 |
武器工业 | 65篇 |
无线电 | 910篇 |
一般工业技术 | 2167篇 |
冶金工业 | 638篇 |
原子能技术 | 179篇 |
自动化技术 | 744篇 |
出版年
2024年 | 45篇 |
2023年 | 207篇 |
2022年 | 301篇 |
2021年 | 379篇 |
2020年 | 424篇 |
2019年 | 381篇 |
2018年 | 290篇 |
2017年 | 441篇 |
2016年 | 423篇 |
2015年 | 422篇 |
2014年 | 671篇 |
2013年 | 792篇 |
2012年 | 756篇 |
2011年 | 1169篇 |
2010年 | 875篇 |
2009年 | 907篇 |
2008年 | 840篇 |
2007年 | 967篇 |
2006年 | 833篇 |
2005年 | 657篇 |
2004年 | 598篇 |
2003年 | 525篇 |
2002年 | 453篇 |
2001年 | 377篇 |
2000年 | 339篇 |
1999年 | 280篇 |
1998年 | 267篇 |
1997年 | 200篇 |
1996年 | 171篇 |
1995年 | 144篇 |
1994年 | 143篇 |
1993年 | 87篇 |
1992年 | 69篇 |
1991年 | 63篇 |
1990年 | 50篇 |
1989年 | 33篇 |
1988年 | 32篇 |
1987年 | 16篇 |
1986年 | 19篇 |
1985年 | 18篇 |
1984年 | 16篇 |
1983年 | 9篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1964年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
82.
83.
Boiler tubes in power plants have finite life because of prolonged exposure to high temperature, stress and aggressive environment. Service-exposed platen superheater and reheater tubes (148,900 h) made of 2.25Cr-1 Mo steels in a 120 MW boiler of a thermal power plant were evaluated for remnant life. The investigation included hot tensile tests, hardness measurement, dimensional measurement, microscopy and creep tests. Experimentally determined yield and ultimate tensile strength, and estimated 10,000–100,000 h rupture strength in the temperature range 520–580 °C, exhibited a decreasing trend with increasing temperature. Microstructural study did not reveal any significant degradation in terms of creep cavities, cracks, graphitization, etc. Analysis of tensile and stress rupture data revealed that although there was degradation of the tubes due to prolonged service exposure in terms of the ultimate tensile strength values, stress rupture plots showed that the service exposed superheater and reheater tubes could remain in service for a length of more than 10 years at the operating hoop stress of 40 MPa/540 °C, provided no localised damage in the form of cracks or dents develop. 相似文献
84.
Intrinsic, thermal and hygroscopic residual stresses in thin gas-barrier films on polymer substrates
P. Dumont 《Thin solid films》2007,515(19):7437-7441
Intrinsic, thermal, and hygroscopic contributions to the in-plane residual stress in silicon nitride films on polyimide substrates are identified, based on iso-hygric thermal ramps and isothermal relative humidity jumps, combined with non-linear elastic modeling of the resulting dynamics of film curvature. This approach enables the thermal and hygroscopic properties of thin nitride films to be determined and provides useful input for material and process control. 相似文献
85.
We report here a non-enzymatic detecting electrode strip for fast monitoring of uric acid in human whole blood. A single-use amperometric uric acid sensor strip, incorporating a three-electrode configuration, has been fabricated on a polypropylene substrate using low cost screen-printing (thick-film) technology. Both the working and counter electrodes were prepared by screen-printing commercial carbon ink. The integration on the same support of pseudo-reference electrode was obtained by screen-printing a commercial silver ink and subsequent electrochemical pretreatment. Simply by placing a 20 μl human whole blood drop on the strip is enough for uric acid analysis by square-wave voltammetry. Real human whole blood samples were analyzed by this method and compared to the phosphotungstic acid clinical test procedure with satisfactory results. 相似文献
86.
87.
P. K. Sharp J. Q. Clayton G. Clark 《Fatigue & Fracture of Engineering Materials & Structures》1997,20(4):605-614
Abstract— This paper presents results which demonstrate that polymeric filler materials, such as low-viscosity epoxies, can be vacuum-infiltrated into fatigue cracks in 7050 aluminium alloy to produce significant levels of fatigue crack retardation. It was found that the main test variable affecting the degree of retardation was the stress level at which the adhesive was introduced and cured. Two infiltrated adhesives were tested.
Infiltration at 0% (of the original) peak fatigue stress level produced negligible retardation, while infiltration at the 80% stress level produced about 300% increase in fatigue life for one adhesive and 3000% for the other adhesive. For the highest infiltration stress level both crack-face wedging and adhesion contributed initially to the retardation, but the adhesive component ceased after a crack grew through the adhesive to the original crack tip position. The results are discussed in terms of the applicability of the technique to highly-stressed aircraft components. 相似文献
Infiltration at 0% (of the original) peak fatigue stress level produced negligible retardation, while infiltration at the 80% stress level produced about 300% increase in fatigue life for one adhesive and 3000% for the other adhesive. For the highest infiltration stress level both crack-face wedging and adhesion contributed initially to the retardation, but the adhesive component ceased after a crack grew through the adhesive to the original crack tip position. The results are discussed in terms of the applicability of the technique to highly-stressed aircraft components. 相似文献
88.
89.
The mechanical methods based on milling rectilinear or annular grooves on a component's surface and measurement of relaxed strains are some of the most used semi-destructive methods for the determination of residual stresses. These are evaluated from the relaxed strains by means of equations based upon the linear elastic theory. In this paper the errors due to yielding localised at the bottom of the groove have been investigated. The analyses were carried out by means of the finite element technique varying the most important parameters involved. The experimental results show a good agreement with the numerical ones. 相似文献
90.