全文获取类型
收费全文 | 38941篇 |
免费 | 2885篇 |
国内免费 | 3723篇 |
专业分类
电工技术 | 1103篇 |
综合类 | 2286篇 |
化学工业 | 5575篇 |
金属工艺 | 14328篇 |
机械仪表 | 2681篇 |
建筑科学 | 2488篇 |
矿业工程 | 476篇 |
能源动力 | 828篇 |
轻工业 | 389篇 |
水利工程 | 265篇 |
石油天然气 | 3538篇 |
武器工业 | 282篇 |
无线电 | 578篇 |
一般工业技术 | 7523篇 |
冶金工业 | 2228篇 |
原子能技术 | 429篇 |
自动化技术 | 552篇 |
出版年
2024年 | 186篇 |
2023年 | 641篇 |
2022年 | 972篇 |
2021年 | 1241篇 |
2020年 | 1440篇 |
2019年 | 1277篇 |
2018年 | 1086篇 |
2017年 | 1569篇 |
2016年 | 1584篇 |
2015年 | 1599篇 |
2014年 | 2178篇 |
2013年 | 2384篇 |
2012年 | 2491篇 |
2011年 | 2954篇 |
2010年 | 2218篇 |
2009年 | 2402篇 |
2008年 | 1794篇 |
2007年 | 2264篇 |
2006年 | 2210篇 |
2005年 | 1802篇 |
2004年 | 1778篇 |
2003年 | 1542篇 |
2002年 | 1279篇 |
2001年 | 1079篇 |
2000年 | 952篇 |
1999年 | 811篇 |
1998年 | 601篇 |
1997年 | 599篇 |
1996年 | 515篇 |
1995年 | 420篇 |
1994年 | 355篇 |
1993年 | 267篇 |
1992年 | 221篇 |
1991年 | 145篇 |
1990年 | 157篇 |
1989年 | 132篇 |
1988年 | 95篇 |
1987年 | 52篇 |
1986年 | 38篇 |
1985年 | 39篇 |
1984年 | 44篇 |
1983年 | 37篇 |
1982年 | 41篇 |
1981年 | 10篇 |
1980年 | 19篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1974年 | 2篇 |
1959年 | 5篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
Copper phthalocyanine as corrosion inhibitor for ASTM A606-4 steel in 16% hydrochloric acid 总被引:2,自引:0,他引:2
A study based on the corrosion inhibition properties of copper phthalocyanine is described. Coverage degrees of copper phthalocyanine (Cu-phcy) on ASTM-A606-4 steel, obtained by weight loss measurements, were fitted to Langmuir, Frumkin, Temkin and Flory–Huggins adsorption isotherms. A better fit to the Langmuir isotherm was obtained. The polarization curves showed that polarization of both the anodic and cathodic reactions were verified for concentrations higher than 10–4 M, indicating a mixed type action. Only the anodic reactions were polarized for lower concentrations. At high frequencies the Nyquist diagrams showed one capacitive loop attributable to double layer charging and a small one at intermediary frequencies attributable to the faradaic process of hydrogen evolution. The formation of an adsorbed film was characterized by increasing charge transfer resistance values in the low frequency range for increasing inhibitor concentrations. According to the techniques used in this study, copper phthalocyanines showed a high corrosion inhibiting efficiency for all concentrations. 相似文献
72.
This paper focuses on the microscopic damage and progressive failure of a composite reinforced by plain-weave glass cloth under tensile fatigue loading. The fatigue process was divided into three stages like that of multi-directional laminates. It was found that the internal damage at each stage (matrix cracks, debonds in the weft, successive debonds in the warp and ‘metadelaminations’ between warps and wefts) occurred near the cross-over point of the fabric. The modulus decay mechanism was explained by considering the progression of this internal damage. From the end of the first stage to the beginning of the middle stage, a characteristic damage state (CDS) (called a ‘meta-CDS’) was observed. It was found that woven composites have a unit area of damage accumulation (called a ‘unit cell’) and the damage of each unit cell and its distribution control the total fatigue damage of the material. 相似文献
73.
74.
Abstract— In response to the increasing structural applications in duplex steels for welded structures, fatigue behaviour of a SAF 2304 grade duplex stainless steel was investigated, considering both the base metal and GTAW welded joints. Fatigue curves and fatigue limits under rotary bending fatigue were obtained. The study focused attention on the microstructural features of fatigue crack propagation of the two series of experiments, thereby permitting an evaluation of the tortuous crack path of welded joints and the mechanisms related to threshold microstructural barriers. 相似文献
75.
The GILDES computer model, incorporating Stumm's concept of proton- and ligand-promoted dissolution, has been used to simulate the exposure of copper at room temperature to 210 ppb sulfur dioxide and 80% relative humidity. The agreement is good between the calculations and laboratory exposures performed under these exposure conditions. Surface reactions are relatively more important at lower relative humidities and the dominant corrosion products formed are solid state Cu2SO3, CuSO3 and Cu2U. Free-radical redox processes are important participants and control the relative distribution of Cu(I)- and Cu(H)-containing corrosion products. 相似文献
76.
C. M. Branco J. M. Ferreira M. O. W. Richardson P. Fael 《International Journal of Fatigue》1992,14(6):367-376
This paper presents results of a fatigue life investigations carried out in plate specimens of a fibre-glass-reinforced phenolic matrix composite. Tensile and Young's modulus data were obtained at four different testing temperatures (room temperature, 100, 150 and 200 °C). The fatigue S−N data were obtained at room temperature only and for two stress ratio values (R=0 and 0.4). Fatigue and tensile behaviour was assesesed in the composite with the fibres aligned in the longitudinal loading direction. The results were obtained for two values of volume fraction (0.28 and 0.42) and three different glass surface treatments. A detailed comparison of fatigue results is given taking into account several fatigue parameters and also the testing variables. Results of observations of SEM fracture surfaces are also presented. 相似文献
77.
本文简要介绍了国外在开发超酸性气体过程中遇到的材料选择、腐蚀监测、水化物堵塞、超酸性气的处理和加工等问题所采取的措施和办法。 相似文献
78.
J. Weise Dr.‐Ing. O. Yezerska M. Busse M. Haesche V. Zanetti‐Bueckmann M. Schmitt 《Materialwissenschaft und Werkstofftechnik》2007,38(11):901-906
Micro‐porous syntactic foams were produced by means of integration of glass bubbles into aluminium and zinc matrices. Preforms of glass bubbles were pressure infiltrated with the alloys AlSi9Cu9 ans ZnAl4Cu using squeeze casting. The preforms were sintered thermically without the use of bonding agents. Using the combination of different sintering steps syntactic foams with locally different densities could be produced. The mechanical properties of the foams were tested indicating a high compression strength of the foams and a very good compression energy absorption. Furthermore, corrosion behaviour and behaviour at higher temperatures were investigated. 相似文献
79.
文章较全面的介绍了如何根据设备、装置、构件所处的工作环境及使用条件进行防腐蚀设计,及其防腐蚀设计的内容和注意事项,选择合适的防腐蚀材料,确保产品的使用寿命 相似文献
80.
Ali Hassanzadeh 《Corrosion Science》2007,49(4):1895-1906
In our previous works, the corrosion inhibition properties of propylamine (PA), iso-propylamine (i-PA), butylamine (BA), tert-butylamine (t-BA), hexylamine (HA), ethylenediamine (EDA), diethanolamine (DEA), 3-amino-1-propanol (3-AP), 2-dimethylethanolamine (2-DEA), cyclohexylamine (CHA), N-methylcyclohexylamine (N-MCA) and dicyclohexylamine (DCHA) have been investigated by means of electrochemical impedance spectroscopy (EIS) with a carbon steel rotating disc electrode in some petroleum/water corrosive mixtures containing acetic acid and NaCl at 25 °C. In this work, the Kramers-Kronig transformations (KKTs) were applied to evaluate the validity of the impedance data of these amine compounds in hydrodynamic condition. The results obtained showed that experimental impedance data did not satisfy in K-K relations completely viz. indicated some errors. These errors were related to stray capacitances, external transmission line effects, pits formation and change in interface during data acquisition at high and low frequencies regions. In addition, the selection of a suitable equivalent circuit strongly emphasized to better interpret of EIS data which in turn cause better resulted KKTs spectra. With considering obtained transformations, more effective inhibitor was selected with regard to its charge transfer resistance, the corrosion capacitance and well satisfying in K-K relations. 相似文献