全文获取类型
收费全文 | 412762篇 |
免费 | 3145篇 |
国内免费 | 953篇 |
专业分类
化学 | 192324篇 |
晶体学 | 6473篇 |
力学 | 21492篇 |
综合类 | 7篇 |
数学 | 60963篇 |
物理学 | 135601篇 |
出版年
2021年 | 3160篇 |
2020年 | 3364篇 |
2019年 | 3807篇 |
2018年 | 12018篇 |
2017年 | 12712篇 |
2016年 | 10664篇 |
2015年 | 4941篇 |
2014年 | 7288篇 |
2013年 | 16395篇 |
2012年 | 15993篇 |
2011年 | 25073篇 |
2010年 | 16989篇 |
2009年 | 16919篇 |
2008年 | 22062篇 |
2007年 | 24829篇 |
2006年 | 12553篇 |
2005年 | 16078篇 |
2004年 | 12678篇 |
2003年 | 11568篇 |
2002年 | 9966篇 |
2001年 | 10582篇 |
2000年 | 7991篇 |
1999年 | 6037篇 |
1998年 | 5040篇 |
1997年 | 4862篇 |
1996年 | 4678篇 |
1995年 | 3992篇 |
1994年 | 3927篇 |
1993年 | 3813篇 |
1992年 | 4204篇 |
1991年 | 4408篇 |
1990年 | 4205篇 |
1989年 | 4119篇 |
1988年 | 3893篇 |
1987年 | 4032篇 |
1986年 | 3789篇 |
1985年 | 4762篇 |
1984年 | 4835篇 |
1983年 | 4030篇 |
1982年 | 4104篇 |
1981年 | 3816篇 |
1980年 | 3776篇 |
1979年 | 4058篇 |
1978年 | 4067篇 |
1977年 | 3962篇 |
1976年 | 3981篇 |
1975年 | 3754篇 |
1974年 | 3705篇 |
1973年 | 3754篇 |
1972年 | 2665篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
A. S. Parshin G. A. Aleksandrova S. N. Varnakov S. A. Kushchenkov S. G. Ovchinnikov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2007,1(4):462-465
The results of studying Fe/Si and Si/Fe layered structures with different thicknesses of the top layer by reflected electron energy loss spectroscopy are presented. A new method is proposed for the estimation of volume fractions of components in binary systems within the framework of the effective dielectric medium model. 相似文献
993.
P. V. Ivannikov N. S. Chekalin P. A. Miroshnikov G. V. Saparin A. A. Altukhov A. V. Shustrov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2007,1(4):386-393
Surfaces of natural type-IIa diamond plates used in ionizing-radiation detectors are studied in a scanning electron microscope using techniques of electron-beam-induced conductivity at different bias voltages and real-color cathodoluminescence. 相似文献
994.
The article concerns heterojunction resonant cavity-enhanced (RCE) Schottky photodiodes with GaAs in the absorption layer. The quantum efficiency and linear pulse response have thoroughly been analysed. For the first time, the response of a heterojunction photodiode has been modelled by the phenomenological model for a two-valley semiconductor. The results obtained have shown that the satellite valleys, as well as the parasitic time constant, significantly influence the response and, accordingly, have to be taken into account when analysing and optimizing RCE photodetectors. 相似文献
995.
N. B. Valetova L. L. Semenycheva I. S. Il’ichev A. N. Artemov D. F. Grishin 《Russian Journal of Applied Chemistry》2007,80(5):818-821
Features of radical polymerization of styrene in the presence of (diphenylbutadiene)tricarbonylchromium were studied. 相似文献
996.
V. M. Arzhavitin 《Technical Physics》2003,48(6):797-799
The stressed state of in metallic composite systems is analyzed. It is analytically shown that the temperature dependences of the internal friction in the composites may have extrema that are caused by internal stresses. The analytical results are supported by the experimental temperature dependences of the internal friction in (Cu-13% Sn)-30% Nb and Cu-1.3% Cr composites. 相似文献
997.
998.
S. Mentus Dijana Jelić Veselinka Grudić 《Journal of Thermal Analysis and Calorimetry》2007,90(2):393-397
Thermal decomposition of lanthanum nitrate to lanthanum oxide was carried out by both temperature programmed heating (TPH)
and citrate-gel combustion. The temperature programmed heating was carried out under flow of oxidizing (air), neutral (nitrogen)
and reducing (25 vol.% hydrogen+argone mixture) gases, and the processes were controlled by simultaneous thermogravimetry
and differential thermal analysis. It was shown that hydrogen atmosphere helps to reduce temperatures of all decomposition
steps. The results of TPH were utilized to check the nature of residues in the products of lanthanum nitrate-to-oxide conversion
performed via citrate-gel combustion technique. 相似文献
999.
C.P. Paul P. Ganesh S.K. Mishra P. Bhargava J. Negi A.K. Nath 《Optics & Laser Technology》2007,39(4):800-805
This paper presents an investigation of laser rapid manufacturing (LRM) for Inconel-625 components. LRM is an upcoming rapid manufacturing technology, it is similar to laser cladding at process level with different end applications. In general, laser-cladding technique is used to deposit materials on the substrate either to improve the surface properties or to refurbish the worn out parts, while LRM is capable of near-net shaping the components by layer-by-layer deposition of the material directly from CAD model. In the present study, a high-power continuous wave (CW) CO2 laser system, integrated with a co-axial powder-feeding system and a three-axis workstation were used. The effect of processing parameters during LRM of Inconel-625 was studied and the optimum set of parameters for the maximum deposition rate was established employing Orthogonal L9 array of Taguchi technique. Results indicated that the powder feed rate and the scan speed contributed about 56% and 26%, respectively to the deposition rate, while the influence of laser power was limited to 10% only. Fabricated components were subjected to non-destructive testing (like—ultrasonic testing, dye-penetrant testing), tensile testing, impact testing, metallographic examinations and micro-hardness measurement. The test results revealed defect-free material deposition with improved mechanical strength without sacrificing the ductility. 相似文献
1000.
Nikulin S. S. Akatova I. N. Kondrat'eva N. A. 《Russian Journal of Applied Chemistry》2003,76(4):652-655
The influence of the charge of a metal cation and the nature of a coagulant on the recovery of butadiene-styrene rubber and properties of rubber stocks and vulcanizates was examined. 相似文献