全文获取类型
收费全文 | 364212篇 |
免费 | 3825篇 |
国内免费 | 1155篇 |
专业分类
化学 | 190172篇 |
晶体学 | 6147篇 |
力学 | 16280篇 |
综合类 | 4篇 |
数学 | 40277篇 |
物理学 | 116312篇 |
出版年
2020年 | 2933篇 |
2019年 | 3304篇 |
2018年 | 4281篇 |
2017年 | 4280篇 |
2016年 | 6473篇 |
2015年 | 4038篇 |
2014年 | 6367篇 |
2013年 | 16070篇 |
2012年 | 12053篇 |
2011年 | 14767篇 |
2010年 | 10566篇 |
2009年 | 10480篇 |
2008年 | 13884篇 |
2007年 | 13580篇 |
2006年 | 12990篇 |
2005年 | 11821篇 |
2004年 | 10796篇 |
2003年 | 9708篇 |
2002年 | 9513篇 |
2001年 | 11776篇 |
2000年 | 8805篇 |
1999年 | 6858篇 |
1998年 | 5376篇 |
1997年 | 5376篇 |
1996年 | 5101篇 |
1995年 | 4705篇 |
1994年 | 4620篇 |
1993年 | 4507篇 |
1992年 | 5106篇 |
1991年 | 5299篇 |
1990年 | 4969篇 |
1989年 | 4916篇 |
1988年 | 4903篇 |
1987年 | 4795篇 |
1986年 | 4505篇 |
1985年 | 5967篇 |
1984年 | 6180篇 |
1983年 | 4917篇 |
1982年 | 5077篇 |
1981年 | 4891篇 |
1980年 | 4780篇 |
1979年 | 5104篇 |
1978年 | 5285篇 |
1977年 | 5162篇 |
1976年 | 5206篇 |
1975年 | 4777篇 |
1974年 | 4758篇 |
1973年 | 4843篇 |
1972年 | 3307篇 |
1971年 | 2716篇 |
排序方式: 共有10000条查询结果,搜索用时 765 毫秒
311.
312.
It is proved that biorthogonal polynomials obey two different kinds of Christoffel-Darboux-type formulae, one linking polynomials with a different parameter and one combining polynomials with different degrees. This is used to produce a mixed recurrence relation, which is valid for all biorthogonal polynomials. This recurrence relation establishes several results on interlacing property of zeros of successive biorthogonal polynomials and leads to a new result on the interlace of zeros of orthogonal polynomials (of equal degrees) with respect to two distributionsdψ(x) andx p dψ(x), 0<p≤1, with support in either [0, 1] or [1, ∞). 相似文献
313.
314.
315.
S. P. Mukherjee A. K. Chattopadhyay 《The Journal of the Operational Research Society》1989,40(5):489-494
Consider an organization with several categories of staff, each having a specified number of members. The age of entry into service and the age of retirement are both specified. Withdrawals occur at time-independent rates. Under this set-up, the authors have computed the maximum ages at which promotions should take place, assuming that the staff members continuing at various ages are random. Some illustrative calculations have been carried out. 相似文献
316.
317.
P. Le Bars 《Journal of Combinatorial Theory, Series A》2006,113(8):1771-1782
The aggregate error locator is defined and a computation method is given. The aggregate error locator is then used in a type of Forney algorithm to compute the error values in the received words of a Ca,b algebraic geometry code. 相似文献
318.
A three-dimensional molecular dynamics (MD) model is utilized to investigate the effect of tool geometry on the deformation process of the workpiece and the nature of deformation process at the atomic-scale. Results show that different states exist between the atomic force microscope (AFM) pin tool and the workpiece surface, i.e. the non-wear state, the ploughing state, the state in which ploughing is dominant and the state in which cutting plays a key role. A relationship between the deformation process of the workpiece and the potential energy variation is presented. The potential energy variation of atoms in different deformed regions in the workpiece such as plastically deformed region, elastically deformed region and the mixed deformation region is different. The features of variations of potential energy are discussed. 相似文献
319.
A systematic study on the electrochemical behavior of diosmin in Britton-Robinson buffer (pH 2.0-10.0) at a glassy carbon electrode (GCE) was made. The oxidation process of the drug was found to be quasi-reversible with an adsorption-controlled step. The adsorption stripping response was evaluated with respect to various experimental conditions, such as the pH of the supporting electrolyte, the accumulation potential and the accumulation time. The observed anodic peak current at +0.73 V vs. Ag/AgCl reference electrode increased linearly over two orders of magnitude from 5.0x10(-8) M to 9.0x10(-6) M. A limit of detection down to 3.5x10(-8) M of diosmin at the GCE was achieved with a mean recovery of 97+/-2.1%. Based on the electrochemical data, an open-circuit accumulation step in a stirred sample solution of BR at pH 3.0 was developed. The proposed method was successfully applied to the determination of the drug in pharmaceutical formulations. The results compared favorably with the data obtained via spectrophotometric and HPLC methods. 相似文献
320.
In the field of industrial vision, the 3D inspection of highly reflective metallic objects is still a delicate task. The specular
reflections prevent the use of a 3D laser scanner, whereas the phase shifting-based 3D systems are more adapted to inspect
surfaces with low curvature. This paper deals with a new automated 3D inspection system based on polarization analysis. Studying
the state of polarization of the reflected light is very useful for obtaining information on the normals of the surface. An
extension of the shape from polarization method from dielectric to metallic surfaces is demonstrated. Then, an improved relaxation
algorithm is provided in order to reconstruct the shape from the normal field given by the polarization analysis. Finally,
applications to shape defect detection are discussed and the efficiency of the system in discriminating defects on highly
reflective metallic objects made by stamping and polishing is presented.
The text was submitted by the authors in English. 相似文献