全文获取类型
收费全文 | 432601篇 |
免费 | 13987篇 |
国内免费 | 6379篇 |
专业分类
电工技术 | 13012篇 |
技术理论 | 9篇 |
综合类 | 8887篇 |
化学工业 | 68759篇 |
金属工艺 | 27709篇 |
机械仪表 | 20871篇 |
建筑科学 | 14620篇 |
矿业工程 | 7663篇 |
能源动力 | 7930篇 |
轻工业 | 20114篇 |
水利工程 | 7532篇 |
石油天然气 | 20740篇 |
武器工业 | 1073篇 |
无线电 | 39816篇 |
一般工业技术 | 93981篇 |
冶金工业 | 42816篇 |
原子能技术 | 13951篇 |
自动化技术 | 43484篇 |
出版年
2022年 | 6275篇 |
2021年 | 8513篇 |
2020年 | 6485篇 |
2019年 | 6269篇 |
2018年 | 14910篇 |
2017年 | 15761篇 |
2016年 | 13463篇 |
2015年 | 8521篇 |
2014年 | 11828篇 |
2013年 | 17880篇 |
2012年 | 17533篇 |
2011年 | 23197篇 |
2010年 | 20159篇 |
2009年 | 19564篇 |
2008年 | 19911篇 |
2007年 | 20433篇 |
2006年 | 12995篇 |
2005年 | 13244篇 |
2004年 | 11009篇 |
2003年 | 10711篇 |
2002年 | 9910篇 |
2001年 | 8800篇 |
2000年 | 8277篇 |
1999年 | 7170篇 |
1998年 | 9444篇 |
1997年 | 7676篇 |
1996年 | 6124篇 |
1995年 | 5132篇 |
1994年 | 4676篇 |
1993年 | 4562篇 |
1992年 | 4087篇 |
1991年 | 4060篇 |
1990年 | 4096篇 |
1989年 | 3938篇 |
1988年 | 3748篇 |
1987年 | 3681篇 |
1986年 | 3500篇 |
1985年 | 3618篇 |
1984年 | 3516篇 |
1983年 | 3409篇 |
1981年 | 3304篇 |
1980年 | 3336篇 |
1979年 | 3565篇 |
1978年 | 3784篇 |
1977年 | 3774篇 |
1976年 | 4229篇 |
1975年 | 3522篇 |
1974年 | 3592篇 |
1973年 | 3613篇 |
1972年 | 3306篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
AM Luciani S Di Capua L Guidoni R Ragona A Rosi V Viti 《Canadian Metallurgical Quarterly》1996,41(3):509-521
NMR relaxation times T1 and T2 of agarose and Fricke agarose gels have been measured in the range 17-51 MHz. The analysis of the spin echo curves indicates a multiexponential behaviour, characterized by three components, at all the examined frequencies. The relative T2 values, ranging from a few to a hundred milliseconds, can be attributed to different species of water molecules present in the gel. Two of these components are characterized by relaxation rates R2a and R2b, more sensitive than R1 to gamma irradiation, the sensitivity S being S(R1) = 0.066 s-1 Gy-1, S(R2a) = 0.088 s-1 Gy-1, S(R2b) = 0.17 s-1 Gy-1. The three T2 values decrease as a function of frequency, but no gain in dose sensitivity is obtained by changing the working frequency in the examined range. The relaxivity of agarose gels containing ferrous or ferric ions has also been measured and found to be different from those of the corresponding solutions in the absence of agarose. Thus it was possible to estimate the irradiation yield from three independent parameters, R1, R2a and R2b. No effect of the dose rate or of the source energy has been observed for any of these parameters. 相似文献
992.
V. A. Varlachev A. N. Kuzin S. V. Lykhin E. S. Solodovnikov Yu. P. Usov A. V. Fotin Yu. A. Tsibul'nikov 《Atomic Energy》1995,79(1):447-449
All-Union Scientific-Research Institute of Nuclear Physics at the S. M. Kirov Tomsk Polytechnical University. Translated from
Atomnaya énergiya, Vol. 79, No. 1, pp. 38–40, July, 1995. 相似文献
993.
A mathematical model of complex heat exchange in the flame space of the melting zone of a regenerative bath furnace for sheet glass is presented. The calculated temperature fields in the gas space and on the internal surface of the roof, fields of the density of heat absorption by the surface of the pool. and consumption components in the heat balance of the furnace indicate the possibility of using the model for detailed analysis and prediction of its thermal operation.Translated from Steklo i Keramika, No. 3–5, May, 1996. 相似文献
994.
Using power resources of the outer space and its industrialization have become an urgent task in the development of present day civilization. Solar energy is the most suitable basis for power supply for the majority of projects in the near-Earth space. Passing on to the large-scale space-based systems of power supply requires putting into life demonstration experiments in which power transmission by electromagnetic emission is supposed.In the paper the expedience of developing an autonomous power module which provides the possibility of space programs with great power consumption and wireless transmission system running-up is proved. Ukraine can design a solar power satellite of 10–20 kW power on the basis of the research satellite AUOS-SM. Two variants of design solutions for such satellite with solar arrays of great area are presented. Power transmission to the space vehicle-consumer can be conducted by cable as well as in a wireless way. The possibilities of placing microwave and laser energy transmission systems on board the satellite are analysed. It is shown that a power supply system for space vehicles with transmission distance of thousands km can be designed basing on modern lasers.Some experiments making use of great electric power generated by the plant of the satellite under consideration are proposed. The running-up of electric thrusters which are necessary for orientation and distancing is of great interest. Wireless power transmission may be carried on to a small satellite equipped with electric thrusters. 相似文献
995.
Ionic conductivity in poly(vinyl butyral) based polymeric electrolytes: Effect of solvents and salts
Li+ conductive solid polymeric electrolytes (SPEs) have been prepared by complexing Li salts LiX (X = I, SCN, CLO4, CF3SO3) with poly(vinyl butyral) (PVB) an amorphous polymer with a low Tg value and well known for its outstanding laminating properties. These self-supporting SPEs have been prepared by the solution cast technique using cyclohexanone, tetrahydrofuran, and n-butyl alcohol as solvents. The XRD and DSC investigations correlated to measured ionic conductivities have revealed that in addition to the amorphous nature of the resulting complex, its Tg value, the concentration and the values of the lattice energies of the complexing salts, the solvent used in making the SPEs also govern the value of ionic conductivity. Highest ionic conductivity values attained in SPEs made with n-butyl alcohol are explained in terms of the interception of the hydrogen bonding due to solvation. 相似文献
996.
997.
This article considers a discrete sequential multilevel automated system for recording electron-diffraction patterns. A comparative
analysis is presented, along with experimental results that make it possible to evaluate the effectiveness of the technical
decisions on which the device is based. The general design of the system is presented.
Translated from Izmeritel'naya Tekhnika No. 5, pp. 16–18, May, 1996. 相似文献
998.
高性能各向异性Sm2Fe17Nx磁粉的制备 总被引:5,自引:0,他引:5
本文研究了高性能各向异性Sm2Fe17Nx磁粉的制备工艺路线与工艺参数。优化了制备与工艺参数。已制备出磁性能达到:Br=1.39T,Hci=850KA/m和(BH)m=236KJ/m^3的各向异性Sm2Fe17N2.88磁粉,该磁粉的各向异性场HA达到20T。 相似文献
999.
NIKIÉT. Translated from Atomnaya Énergiya, Vol. 75, No. 4, pp. 265-269, October, 1993. 相似文献
1000.
氯化铁催化合成富马酸二甲酯 总被引:9,自引:0,他引:9
氯化铁可代替硫酸催化酯化反应,探讨了氯化铁催化合成富马酸二甲酯的条件,操作简便,反应温和,无腐蚀,减少了污染与产品纯化。 相似文献