全文获取类型
收费全文 | 3925篇 |
免费 | 195篇 |
国内免费 | 15篇 |
专业分类
电工技术 | 35篇 |
综合类 | 10篇 |
化学工业 | 1164篇 |
金属工艺 | 113篇 |
机械仪表 | 141篇 |
建筑科学 | 62篇 |
矿业工程 | 29篇 |
能源动力 | 157篇 |
轻工业 | 162篇 |
水利工程 | 28篇 |
石油天然气 | 92篇 |
武器工业 | 1篇 |
无线电 | 371篇 |
一般工业技术 | 974篇 |
冶金工业 | 237篇 |
原子能技术 | 70篇 |
自动化技术 | 489篇 |
出版年
2023年 | 51篇 |
2022年 | 179篇 |
2021年 | 185篇 |
2020年 | 83篇 |
2019年 | 98篇 |
2018年 | 127篇 |
2017年 | 123篇 |
2016年 | 141篇 |
2015年 | 105篇 |
2014年 | 189篇 |
2013年 | 276篇 |
2012年 | 215篇 |
2011年 | 262篇 |
2010年 | 201篇 |
2009年 | 196篇 |
2008年 | 206篇 |
2007年 | 162篇 |
2006年 | 123篇 |
2005年 | 117篇 |
2004年 | 102篇 |
2003年 | 108篇 |
2002年 | 105篇 |
2001年 | 79篇 |
2000年 | 68篇 |
1999年 | 47篇 |
1998年 | 36篇 |
1997年 | 42篇 |
1996年 | 38篇 |
1995年 | 29篇 |
1994年 | 30篇 |
1993年 | 23篇 |
1992年 | 26篇 |
1991年 | 11篇 |
1990年 | 30篇 |
1989年 | 21篇 |
1987年 | 13篇 |
1985年 | 14篇 |
1984年 | 18篇 |
1983年 | 14篇 |
1981年 | 13篇 |
1980年 | 13篇 |
1979年 | 15篇 |
1978年 | 13篇 |
1977年 | 14篇 |
1975年 | 16篇 |
1974年 | 13篇 |
1973年 | 18篇 |
1970年 | 10篇 |
1969年 | 10篇 |
1968年 | 12篇 |
排序方式: 共有4135条查询结果,搜索用时 15 毫秒
1.
I. N. Andronov Yu. I. Ryabkov N. P. Bogdanov N. A. Severova A. N. Danilov I. V. Churilina 《Russian Metallurgy (Metally)》2015,2015(10):778-784
The influence of the thermal cycling conditions on the thermal-cycling creep of a TN-1 alloy and the related irreversible deformations is studied. The conditions under which an anomalous increase in the irreversible deformations begins are determined. The structural mechanism of the irreversible deformations of an equiatomic alloy is shown to be analogous to the structural mechanism of metal creep at high temperatures: it predominantly has a dislocation character. It is proposed to use the effect of anomalous increase in the deformation of materials with reversible martensitic transformations for forming parts made of these materials at low temperatures. 相似文献
2.
3.
Vladimir Rozenshtein Alexander Berg Haim Levanon Uwe Krueger Dietmar Stehlik Yuri Kandrashkin Art Van Der Est 《Israel journal of chemistry》2003,43(3-4):373-381
Light-induced spin-polarized transient EPR spectra are reported for several water-soluble copper porphyrins. The spectra are assigned to the doublet ground state, with emissive spin polarization resulting from photoexcitation and subsequent electronic relaxation. In contrast to other systems for which polarization of a doublet ground state has been observed, the exchange interactions in the copper porphyrins are strong and the geometry is fixed. It is proposed that intersystem crossing from the photoexcited trip-doublet to the trip-quartet state can lead to net polarization of the spin system and that this polarization is maintained during electronic decay, possibly via charge-transfer and exciplex states. The intensity of the observed spin polarization is essentially independent of the molecular orientation in the external field, but is strongly dependent on the nature of the charged peripheral groups. Possible reasons for this behavior are discussed. 相似文献
4.
5.
Brezina V 《Neurocomputing》2007,70(10-12):1863-1869
Variability of the neuronal spike pattern is usually thought of in terms of the information that the different interspike intervals might be encoding. However, the very presence of the variability can have other kinds of functional significance. Here we consider the example of the B15/B16-ARC neuromuscular system of Aplysia, a model system for the study of neuromuscular modulation and control. We show that variability of motor neuron spike timing at the input to the system penetrates throughout the system, affecting all downstream variables including modulator release, modulator concentrations, modulatory actions, and the contraction of the muscle. Furthermore, not only does the variability penetrate through the system, but it is actually instrumental in maintaining its modulation and contractions at a robust, physiological level. 相似文献
6.
V. V. Andrikanis B. V. Andreev K. B. Rudyak F. V. Karpeko A. V. Ivanov N. N. Parsent’ev V. S. Nikitchenko G. V. Danilov I. A. Sinel’nikov 《Chemistry and Technology of Fuels and Oils》2006,42(3):229-234
Increasing attention at oil refineries is being focused on solving environmental problems caused by stiffening of the requirements
for emissions of harmful substances into air and water. Advanced technologies that reduce the effect of industrial enterprises
on the environment to the minimum are becoming increasingly in demand. Treatment of process wastewaters to remove hydrogen
sulfide and ammonia is one such problem of the modern refinery with cat crackers.
__________
Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 3, pp. 52–55, May–June, 2006. 相似文献
7.
Svetlana A. Yashnik Zinfer R. Ismagilov Vladimir F. Anufrienko 《Catalysis Today》2005,110(3-4):310-322
The effect of ion exchange conditions, such as Si/Al ratio, precursor copper salt, pH and concentration of the solution, on the catalytic activity in SCR of NO by propane and on the electronic state of copper ions in Cu-ZSM-5 has been studied. The NO conversion in NO SCR by C3H8 has been found to reach a maximum value at Cu/Al ratio about 0.37–0.4 and remain constant at higher Cu/Al.
ESR and UV–vis DR spectroscopy have been used to elucidate stabilization conditions of copper ions in Cu-ZSM-5 zeolites as isolated Cu2+ ions, chain copper oxide structures and square-plain oxide clusters. The ability of copper ions for reduction and reoxidation in the chain structures may be responsible for the catalytic activity of Cu-ZSM-5. These transformations of copper ions are accompanied by the observation of intervalence transitions Cu2+–Cu+ and CTLM of the chain structures in the UV–vis spectra. 相似文献
8.
A technique is proposed for introducing microdoses (10?5–10?10 g) of germanium and indium metals into semiconductor compounds by coulometric titration in a solid electrolyte cell. The solid electrolytes that are reversible with respect to germanium cations (the GeSe-GeI2 system containing 5 mol % GeI2) and indium cations (the InCl3-MgCl2 system containing 15 mol % MgCl2, the InCl3-CdCl2 system containing 1.5 mol % CdCl2, and the In2S3-InCl3 system containing 5 mol % InCl3) are chosen, and their electric transport properties are characterized. The optimum conditions for electrochemical doping (temperature, current density), under which the current efficiency reaches 90–100%, are determined. The doping with germanium and indium is performed for nonstoichiometric compounds, such as lead monotelluride, indium sulfide, and ternary chalcogenide spinel Cd1 ± δCr2Se4. The doping efficiency is controlled by measuring the electromotive force of the corresponding electrochemical cells and the Hall effect, as well as using the electrical conductivity method. The solid electrolytes that are reversible with respect to indium are used to determine the standard Gibbs energies of formation of a number of indium-containing semiconductors. 相似文献
9.
Vladimir Katkovnik Jaakko Astola Karen Egiazarian 《IEEE transactions on image processing》2008,17(6):833-846
The local polynomial approximation (LPA) is a nonparametric regression technique with pointwise estimation in a sliding window. We apply the LPA of the argument of cos and sin in order to estimate the absolute phase from noisy wrapped phase data. Using the intersection of confidence interval (HCI) algorithm, the window size is selected as adaptive pointwise varying. This adaptation gives the phase estimate with the accuracy close to optimal in the mean squared sense. For calculations, we use a Gauss-Newton recursive procedure initiated by the phase estimates obtained for the neighboring points. It enables tracking properties of the algorithm and its ability to go beyond the principal interval [-pi, pi] and to reconstruct the absolute phase from wrapped phase observations even when the magnitude of the phase difference takes quite large values. The algorithm demonstrates a very good accuracy of the phase reconstruction which on many occasion overcomes the accuracy of the state-of-the-art algorithms developed for noisy phase unwrap. The theoretical analysis produced for the accuracy of the pointwise estimates is used for justification of the HCI adaptation algorithm. 相似文献
10.
Porous carbon nanofibers are synthesized by CVD method from acetylene with use of iron-containing catalysts. Activation of the nanofibers in melted potassium hydroxide results in increasing surface area from initial 300–400 m2 g−1 to 1700 m2 g−1. As follows from XRD data, activated nanofibers do not contain regular packages of graphene layers, but retain high electric conductivity. Deposition of copper improves electrochemical hydrogen storing characteristics of carbon nanofibers. Carbon nanomaterials obtained can be used as hydrogen storing materials in batteries instead of hydride forming metals. 相似文献