全文获取类型
收费全文 | 22504篇 |
免费 | 2344篇 |
国内免费 | 1427篇 |
专业分类
电工技术 | 1731篇 |
技术理论 | 1篇 |
综合类 | 2370篇 |
化学工业 | 2484篇 |
金属工艺 | 1889篇 |
机械仪表 | 1727篇 |
建筑科学 | 2165篇 |
矿业工程 | 1754篇 |
能源动力 | 848篇 |
轻工业 | 1490篇 |
水利工程 | 1031篇 |
石油天然气 | 1148篇 |
武器工业 | 253篇 |
无线电 | 1426篇 |
一般工业技术 | 2378篇 |
冶金工业 | 1060篇 |
原子能技术 | 236篇 |
自动化技术 | 2284篇 |
出版年
2024年 | 101篇 |
2023年 | 312篇 |
2022年 | 649篇 |
2021年 | 699篇 |
2020年 | 797篇 |
2019年 | 655篇 |
2018年 | 652篇 |
2017年 | 836篇 |
2016年 | 972篇 |
2015年 | 964篇 |
2014年 | 1564篇 |
2013年 | 1474篇 |
2012年 | 1718篇 |
2011年 | 1809篇 |
2010年 | 1351篇 |
2009年 | 1366篇 |
2008年 | 1157篇 |
2007年 | 1512篇 |
2006年 | 1323篇 |
2005年 | 1079篇 |
2004年 | 912篇 |
2003年 | 756篇 |
2002年 | 649篇 |
2001年 | 524篇 |
2000年 | 474篇 |
1999年 | 396篇 |
1998年 | 259篇 |
1997年 | 258篇 |
1996年 | 201篇 |
1995年 | 154篇 |
1994年 | 148篇 |
1993年 | 94篇 |
1992年 | 81篇 |
1991年 | 60篇 |
1990年 | 62篇 |
1989年 | 44篇 |
1988年 | 38篇 |
1987年 | 17篇 |
1986年 | 23篇 |
1985年 | 18篇 |
1984年 | 15篇 |
1983年 | 18篇 |
1982年 | 16篇 |
1980年 | 10篇 |
1977年 | 4篇 |
1964年 | 5篇 |
1963年 | 6篇 |
1961年 | 4篇 |
1960年 | 5篇 |
1959年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
概述了广义线性模型(含半参数广义线性模型)与非线性模型研究的新进展,着重讨论了它们参数估计的统计推断。近年来,广义线性模型与非线性模型的研究发展迅速,有着广泛的应用前景。 相似文献
72.
The catalytic behavior of the novel MCM-22 zeolite for the continuous alkylation of isobutane with 2-butene has been investigated at a temperature of 50°C, 2.5 MPa total pressure, and a variety of olefin space velocities. At high olefin conversions the MCM-22 zeolite showed a very high initial cracking activity attributable to strong Brønsted acid sites, as well as to the existence of strong diffusional restrictions of the TMP's (formed inside the zeolite) to exit through the channels. At short times on stream (TOS), TMP's account for ca. 40% of the C8 fraction. The olefin conversion and the cracking activity rapidly decline with TOS, while the alkylate product became richer in dimethylhexenes, indicating a predominance of 2-butene dimerization and a loss of hydrogen transfer activity as the catalyst aged. Moreover, MCM-22 gives less TMP's than large-pore zeolites (USY, beta, mordenite), but more than the mediumpore ZSM-5 at similar 2-butene conversion. The latter catalyst was much more selective for olefin dimerization than for isobutane alkylation, presumably because formation of the bulkier TMP's was strongly impeded in its smaller pores. 相似文献
73.
Y. Castrillejo M. R. Bermejo A. M. Martínez C. Abejón S. Sánchez G. S. Picard 《Journal of Applied Electrochemistry》1999,29(1):65-73
The stability of indium chloride and oxide as well as the electrochemical behaviour of indium ions have been studied in the equimolar CaCl2–NaCl melt at 550 C by X-ray diffraction (XRD) and different electrochemical techniques, using molybdenum and tungsten wires as working electrodes. Voltammetric and chronopotentiometric studies showed signals attributed to the presence of three oxidation states of indium, i.e. 0, i and iii. The standard potential of the redox couples, as well as the solubility products of indium oxides have been determined, showing that In(iii) ions are completely reduced to monovalent indium by the indium metal according to the reaction: In () + 2 In 3 In () and that In2O is a strong oxide donor according to the reaction: In2O(s) 2 In() + O2- These results have allowed the construction of E-pO2– equilibrium diagrams summarising the properties of In–O compounds. The electrodeposition of indium was uncomplicated at Mo and W electrodes. Very good adherence of liquid indium to the electrode materials was observed, with the formation of Na–In alloys at highly reducing potentials, and there was no evidence of indium dissolution into the melt. Moreover, the voltammograms corresponding to the electrochemical In(iii)/In(i) exchange were well defined. The two electrochemical steps were found to be quasi-reversible, and the values of the kinetic parameters, ko and , for both reactions, as well as the diffusion coefficients, DIn(III) and DIn(I) were calculated. 相似文献
74.
75.
Abstract. In this paper we consider the time series dependence, stationarity, and higher moments issues of a family of first-order conditionally heteroskedastic in mean models with a possibly time-varying mean parameter. The interest in these models lies in the fact that economic theory and physics often require the connection between the first and second conditional moments of time series. Our results reveal important properties of these models, which are consistent with stylized facts in financial and turbulence data sets. They can also be employed for model identification, estimation, and testing. 相似文献
76.
77.
78.
Anthony G. Dixon 《Chemical Engineering Communications》1988,71(1):217-237
The effective radial thermal conductivity and apparent heat transfer coefficient for a packed bed were experimentally determined for beds of spheres, full cylinders and hollow cylinders, for flow rates giving particle Reynolds numbers in the range 100-1000, and for tube to particle diameter ratios of 5-12. Over these ranges the radial Peclet number Per showed significant dependence on solid conductivity, gas flow rate and particle shape, while the wall Biot number Bi showed significant dependence on tube to particle diameter ratio, gas flow rate and particle shape. These dependencies were predicted well by equations incorporating the effects of these variables into individual gas and solid phase parameters, which were then combined to give the effective or lumped parameters 相似文献
79.
80.
M.A. Montero 《Electrochimica acta》2007,52(5):2083-2090
An alternative method for the determination of the kinetic parameters involved in the elementary steps of the reaction mechanism of the hydrogen electrode reaction is proposed. It is based on the determination of the variation of the polarization resistance in a tubular platinum electrode with a laminar flow of electrolyte as a function of the activity of protons of the electrolyte solution. A theoretical expression that relates the experimental variables and the equilibrium polarization resistance is developed, which takes into account the current distribution along the electrode surface. The results are compared with others obtained previously, contributing to the verification of the kinetic mechanism through a completely different experimental procedure. 相似文献