全文获取类型
收费全文 | 168594篇 |
免费 | 1180篇 |
国内免费 | 193篇 |
专业分类
电工技术 | 2553篇 |
综合类 | 119篇 |
化学工业 | 26622篇 |
金属工艺 | 9472篇 |
机械仪表 | 5715篇 |
建筑科学 | 3013篇 |
矿业工程 | 1887篇 |
能源动力 | 2704篇 |
轻工业 | 8831篇 |
水利工程 | 2730篇 |
石油天然气 | 8692篇 |
武器工业 | 12篇 |
无线电 | 14495篇 |
一般工业技术 | 38259篇 |
冶金工业 | 27826篇 |
原子能技术 | 6933篇 |
自动化技术 | 10104篇 |
出版年
2018年 | 2978篇 |
2017年 | 3094篇 |
2016年 | 3346篇 |
2015年 | 1675篇 |
2014年 | 2956篇 |
2013年 | 6341篇 |
2012年 | 4313篇 |
2011年 | 5402篇 |
2010年 | 4423篇 |
2009年 | 4899篇 |
2008年 | 4944篇 |
2007年 | 4869篇 |
2006年 | 4143篇 |
2005年 | 3820篇 |
2004年 | 3635篇 |
2003年 | 3523篇 |
2002年 | 3452篇 |
2001年 | 3465篇 |
2000年 | 3361篇 |
1999年 | 3214篇 |
1998年 | 7018篇 |
1997年 | 5149篇 |
1996年 | 3821篇 |
1995年 | 2920篇 |
1994年 | 2594篇 |
1993年 | 2724篇 |
1992年 | 2257篇 |
1991年 | 2305篇 |
1990年 | 2410篇 |
1989年 | 2316篇 |
1988年 | 2314篇 |
1987年 | 2191篇 |
1986年 | 2248篇 |
1985年 | 2295篇 |
1984年 | 2207篇 |
1983年 | 2138篇 |
1982年 | 1982篇 |
1981年 | 2193篇 |
1980年 | 2054篇 |
1979年 | 2269篇 |
1978年 | 2431篇 |
1977年 | 2430篇 |
1976年 | 3095篇 |
1975年 | 2246篇 |
1974年 | 2309篇 |
1973年 | 2342篇 |
1972年 | 2156篇 |
1971年 | 1911篇 |
1970年 | 1701篇 |
1969年 | 1632篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
Yu. V. Larichev D. A. Shlyapin P. G. Tsyrul’nikov V. I. Bukhtiyarov 《Catalysis Letters》2008,120(3-4):204-209
Sibunit-supported Ru-catalysts promoted with cesium or rubidium compounds have been comparatively studied with XPS. The cesium promoter interacts both with support and with active component. The absence of the promoter–support interaction in the case of rubidium provides a stronger interaction between promoter and active component compared to the cesium-based catalysts. These differences in the promoter–support and promoter–metal interactions are exhibited when a sequence of ruthenium and alkali introduction are changed. 相似文献
192.
A. V. Lyutetskii N. A. Pikhtin S. O. Slipchenko N. V. Fetisova A. Yu. Leshko E. G. Golikova Yu. A. Ryaboshtan I. S. Tarasov 《Technical Physics Letters》2003,29(4):290-293
Separate confinement InGaAsP/InP laser heterostructures were grown by metalorganic-hydride vapor-phase epitaxy. High-power single-mode laser diodes of mesastripe design based on these heterostructures operate in a wavelength interval of 1.7–1.8 μm with a maximum continuous room temperature output power of 150 mW. The single-mode lasing regime is maintained up to an output power level of 100 mW. 相似文献
193.
Valentina I. Simagina Pavel A. Storozhenko Olga V. Netskina Oksana V. Komova Galina V. Odegova Yury V. Larichev Arcady V. Ishchenko Anna M. Ozerova 《Catalysis Today》2008,138(3-4):253
Catalytic hydrolysis of NaBH4 and NH3BH3 has been studied. It was shown that the nature of the support and the active component of the catalyst affect the H2 generation rate. Despite similar sizes of rhodium particles formed on the surface of different supports (γ-Al2O3, TiO2, carbon), their reactivity is different. Rh/TiO2 with low rhodium concentration (1 wt.%) is the most active catalyst both in the hydrolysis of NaBH4 and NH3BH3. The obtained results show that the rhodium chloride interaction with titania determines the reactivity of rhodium particles formed under action of NaBH4 medium. TEM, DRS UV–vis and XPS were used to characterize the catalysts. 相似文献
194.
Yu. F. Patrakov E. S. Pavlusha N. I. Fedorova Yu. A. Strizhakova 《Solid Fuel Chemistry》2008,42(1):10-13
The results of the thermal solution of oil shale in benzene in a flow unit under supercritical conditions are reported. It was found that the conversion of shale organic matter into liquid products increased by a factor of 2.5 with an increase in the solvent pressure from 5 to 15 MPa. 相似文献
195.
A. I. Nikolaev F. D. Larichkin O. A. Nikolaeva 《Theoretical Foundations of Chemical Engineering》2008,42(5):675-679
The main rules and principles which govern the choice of new variants for chemical technology of combined processing of titanium-rare-metal raw materials are considered. The existing variants of the technology are characterized from the viewpoint of their technological, economical, and ecological efficiency and social importance for a given region. A realistic choice of a technology from a large number of available variants should take into account the entire combination of their advantages and disadvantages The implementation of a rational technological scheme will result in the creation of economically profitable and efficient domestic production satisfying the demands of Russian industry in rare-metal and titanium materials. Directions are noted in which it is expedient to continue studies on designing a rational technology of loparite concentrate or some other concentrate. 相似文献
196.
This paper presents data relating to the performance of sprinklers and detectors in real office fire situations. For sprinklers, these data are additional to that associated with the standardized testing used to determine the design delivery density and pressure requirements for various occupancy situations, and provide a useful insight into the effect of sprinklers on developing fires with various office situations. The data given in this paper include the times for activation of various types of sprinkler heads (normal and fast response), the efficacy of the systems as far as extinguishment is concerned, estimates of the maximum size of the fires prior to commencement of extinguishment and associated air temperatures at various locations within the office enclosures. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
197.
The results of the oxidation of carbon nanofibers and materials obtained on their basis are presented; these results demonstrate that the nanofibers were formed by carbon with different degrees of crystal structure ordering. The experimental data supported previous hypotheses that amorphous carbon results from the decomposition of metal carbides. The subsequent formation of spatial structures and the appearance of crystalline carbon species resulted from catalytic graphitization. It was demonstrated that sorbents can be prepared based on carbon nanofibers after pyrolytic consolidation followed by activation, and these sorbents are more effective than well-known sorbents. 相似文献
198.
I. I. Nemets Yu. N. Trepalina E. A. Doroganov 《Refractories and Industrial Ceramics》2008,49(3):205-208
Physicotechnical properties are provided for concretes based on mechanically-activated phosphate suspensions previously modified
with magnesium and aluminum hydroxides and silicic acid. The results obtained demonstrate the efficiency of using modifying
additions in order to increase the strength and heat resistance of corundum concretes.
Translated from Novye Ogneupory, No. 5, pp. 32–35, May 2008. 相似文献
199.
I. V. Smirnov 《Automatic Documentation and Mathematical Linguistics》2007,41(3):108-113
The task of ascertaining minimal semantic-syntactic text units within the framework of the task of the semantic analysis of texts in the Russian language is considered. The use of the DSM-method for producing rules for ascertaining the meanings of syntaxemes is described, the setting of the goal of producing rules in DSM-method terminology is presented. The analysis of the results of computer experiments and the causes of the presence of contradictory rules are given. 相似文献
200.
A high-power and high-repetition-rate passively Q -switched ytterbium-doped single-mode double-clad fiber laser was built using a Cr4+:YAG saturable absorber (SA). Two different SAs with initial transmissions of Tomicron = 30% and Tomicron = 50% were studied. At the maximum coupled pump power of 9.8 W, an output power of 4.7 W, pulse duration of 143 ns, pulse repetition rate of 253 KHz, pulse energy of 18.5 muJ, and slope efficiency of 49% were obtained with the Tomicron = 30% SA. 相似文献