全文获取类型
收费全文 | 315204篇 |
免费 | 3780篇 |
国内免费 | 1094篇 |
专业分类
化学 | 171202篇 |
晶体学 | 4470篇 |
力学 | 13053篇 |
综合类 | 7篇 |
数学 | 36372篇 |
物理学 | 94974篇 |
出版年
2020年 | 2007篇 |
2019年 | 1968篇 |
2018年 | 1976篇 |
2017年 | 1878篇 |
2016年 | 3873篇 |
2015年 | 3258篇 |
2014年 | 4441篇 |
2013年 | 14028篇 |
2012年 | 10763篇 |
2011年 | 13419篇 |
2010年 | 8304篇 |
2009年 | 8286篇 |
2008年 | 12370篇 |
2007年 | 12616篇 |
2006年 | 12247篇 |
2005年 | 11189篇 |
2004年 | 10059篇 |
2003年 | 8862篇 |
2002年 | 8723篇 |
2001年 | 10119篇 |
2000年 | 7721篇 |
1999年 | 6124篇 |
1998年 | 4907篇 |
1997年 | 4743篇 |
1996年 | 4779篇 |
1995年 | 4370篇 |
1994年 | 4130篇 |
1993年 | 3959篇 |
1992年 | 4449篇 |
1991年 | 4303篇 |
1990年 | 4019篇 |
1989年 | 3838篇 |
1988年 | 4132篇 |
1987年 | 3795篇 |
1986年 | 3688篇 |
1985年 | 5337篇 |
1984年 | 5404篇 |
1983年 | 4387篇 |
1982年 | 4768篇 |
1981年 | 4803篇 |
1980年 | 4553篇 |
1979年 | 4673篇 |
1978年 | 4676篇 |
1977年 | 4653篇 |
1976年 | 4606篇 |
1975年 | 4518篇 |
1974年 | 4366篇 |
1973年 | 4534篇 |
1972年 | 2571篇 |
1971年 | 1885篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
The variational approach based on the covariant quantization method for the curved Einstein space is applied. 相似文献
102.
Blood serum samples were irradiated by monochromatic synchrotron radiation (15 keV) and by 2.4-MeV protons to compare their performance for the detection of trace elements by x-ray fluorescence (XRF) spectrometry. Absolute concentration assignment was based on the addition of an internal standard and on a method which uses the incoherent and coherent radiation as a flux monitor of the incoming beam. Preliminary experiments with a synchrotron XRF microprobe are reported. 相似文献
103.
The precision of intensity modulated fiber optic sensor systems mainly is restricted by the attenuation characteristics of the analog fiber optical data link. Special encoding and referencing schemes are used to overcome this data link dependence. In this paper encoding and referencing principles for optical sensors are outlined and compared. Especially the two wavelengths referencing and the optical delay line processing techniques are discussed in more detail and results are presented. 相似文献
104.
105.
106.
In this paper we obtain a number of Maharam-type slice integral representations, with respect to scalar measures, for positive
projections in Dedekind complete vector lattices and f-algebras.
AMS Classification: 47B65, 46A40, 06F25 相似文献
107.
108.
109.
H E Cline W E Lorensen R J Herfkens G A Johnson G H Glover 《Magnetic resonance imaging》1989,7(1):45-54
A three-dimensional examination of blood vessels is provided using MR data from seven cases. The vascular surfaces are constructed with an algorithm that automatically follows the selected artery or vein and generates a projected three-dimensional gradient shaded image. Fast 3DFT pulse sequences were optimized to enhance the time-of-flight contrast of the intravascular region. By increasing the surface threshold value in a three-dimensional head study, the flesh of a patient's face was peeled away to demonstrate the superfacial temporal artery. Gated cardiac images show the great vessels and cardiac chambers. A three-dimensional view of the aorta shows an irregular surface in the vicinity of an adrenal tumor. 3D MR exams provide a non-invasive technique for assessing vascular morphology in a clinical setting. 相似文献
110.
Stress-Strain State in the Zone of Load Transfer in a Composite Specimen under Uniaxial Tension 总被引:2,自引:2,他引:0
Kulakov V. L. Tarnopol'skii Yu. M. Arnautov A. K. Rytter J. 《Mechanics of Composite Materials》2004,40(2):91-100
The stress-strain state in the zone of load transfer in a uniaxially stretched specimen made of a unidirectional epoxy carbon-fiber-reinforced plastic (CFRP) is investigated. A parametric analysis of the influence of geometric and mechanical characteristics of the specimen on its stress-strain state is performed by means of finite-element modeling. The parameters allowing us to significantly reduce the dangerous concentration of transverse and tangential stresses are revealed. The mechanical tensile characteristics of a high-strength pultruded unidirectional CFRP are determined experimentally, and the size effect of its strength is estimated. 相似文献