全文获取类型
收费全文 | 221169篇 |
免费 | 2699篇 |
国内免费 | 1324篇 |
专业分类
化学 | 122847篇 |
晶体学 | 3239篇 |
力学 | 8904篇 |
综合类 | 61篇 |
数学 | 24397篇 |
物理学 | 65744篇 |
出版年
2020年 | 1754篇 |
2019年 | 1896篇 |
2018年 | 2483篇 |
2017年 | 2531篇 |
2016年 | 3646篇 |
2015年 | 2425篇 |
2014年 | 3538篇 |
2013年 | 8883篇 |
2012年 | 7692篇 |
2011年 | 9401篇 |
2010年 | 6651篇 |
2009年 | 6454篇 |
2008年 | 8800篇 |
2007年 | 8900篇 |
2006年 | 8388篇 |
2005年 | 7707篇 |
2004年 | 6873篇 |
2003年 | 6058篇 |
2002年 | 5987篇 |
2001年 | 6708篇 |
2000年 | 5071篇 |
1999年 | 3675篇 |
1998年 | 3040篇 |
1997年 | 3013篇 |
1996年 | 3015篇 |
1995年 | 2623篇 |
1994年 | 2722篇 |
1993年 | 2584篇 |
1992年 | 2831篇 |
1991年 | 2900篇 |
1990年 | 2705篇 |
1989年 | 2619篇 |
1988年 | 2561篇 |
1987年 | 2503篇 |
1986年 | 2529篇 |
1985年 | 3304篇 |
1984年 | 3366篇 |
1983年 | 2812篇 |
1982年 | 3062篇 |
1981年 | 2825篇 |
1980年 | 2617篇 |
1979年 | 2799篇 |
1978年 | 3005篇 |
1977年 | 3039篇 |
1976年 | 3064篇 |
1975年 | 2799篇 |
1974年 | 2912篇 |
1973年 | 2963篇 |
1972年 | 2320篇 |
1971年 | 1846篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
231.
D. Chithrani R. L. Williams J. Lefebvre P. J. Poole G. C. Aers 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):290
We discuss the preparation and spectroscopic characterisation of a single InAs/InP quantum dot suitable for long-distance quantum key distribution applications around λ=1.55 μm. The dot is prepared using a site-selective growth technique which allows a single dot to be deposited in isolation at a controlled spatial location. Micro-photoluminescence measurements as a function of exciton occupation are used to determine the electronic structure of the dot. Biexciton emission, shell filling and many-body re-normalization effects are observed for the first time in single InAs/InP quantum dots. 相似文献
232.
The logarithmic decrement and shear modulus of a bulk amorphous Zr52.5Ti5Cu17.9Ni14.6Al10 alloy were studied with an inverse torsion pendulum in the range from room temperature to the crystallization temperature and in the frequency range 5–40 Hz. The activation energy spectra of reversible and irreversible structural relaxation were estimated. The results obtained are discussed in the context of a two-energy-level model. 相似文献
233.
234.
The general theory on the transformation of elastic waves at a rigid nodal junction of an arbitrary number of thin plates is considered. The notion of transformation marix is introduced, and a way for computing it and numerical examples are given. Properties of the transformation matrix resulted from the reciprocity principle and the energy conservatin law are studied. In particular, a new relation that expresses the energy conservation low for the case where a wave damped in the direction of the joint of plates is a source of a field is obtained. Bibliography: 18 titles. 相似文献
235.
V. L. Tsymbalenko 《JETP Letters》2003,78(8):493-496
The kinetics of formation of an anomalous phase from a solution with a small 3He impurity was studied in the temperature range 0.2–0.7 K up to a supersaturation of ~30 mbar. The phase diagram was determined for normal and anomalous growths. It is found that, in the presence of impurities, the formation of a fast-growing state is retarded. This experimental fact indicates that the dissipative processes in fluids have an appreciable effect on the phase formation kinetics. The retardation is, possibly, caused by the direct interaction of an impurity with the crystal surface. 相似文献
236.
237.
238.
Makarov V. L. Khlobystov V. V. Kashpur E. F. Mikhal'chuk B. R. 《Ukrainian Mathematical Journal》2003,55(6):942-955
We construct an integral Newton-type interpolation polynomial with a continual set of nodes. This interpolant is unique and preserves an operator polynomial of the corresponding degree. 相似文献
239.
We establish some liminf theorems on the increments of a (N,d)-Gaussian process with the usual Euclidean norm, via estimating upper bounds of large deviation probabilities on the suprema
of the (N,d)-Gaussian process.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
240.
Z. J. Yu L. J. Liu R. X. Zhuo 《Journal of polymer science. Part A, Polymer chemistry》2003,41(1):13-21
The ring‐opening polymerization of ε‐caprolactone (ε‐CL), initiated by carboxylic acids such as benzoic acid and chlorinated acetic acids under microwave irradiation, was investigated; with this method, no metal catalyst was necessary. The product was characterized as poly(ε‐caprolactone) (PCL) by 1H NMR spectroscopy, Fourier transform infrared spectroscopy, ultraviolet spectroscopy, and gel permeation chromatography. The polymerization was significantly improved under microwave irradiation. The weight‐average molecular weight (Mw) of PCL reached 44,800 g/mol, with a polydispersity index [weight‐average molecular weight/number‐average molecular weight (Mw/Mn)] of 1.6, when a mixture of ε‐CL and benzoic acid (25/1 molar ratio) was irradiated at 680 W for 240 min, whereas PCL with Mw = 12,100 and Mw/Mn = 4.2 was obtained from the same mixture by a conventional heating method at 210 °C for 240 min. A degradation of the resultant PCL was observed during microwave polymerization with chlorinated acetic acids as initiators, and this induced a decrease in Mw of PCL. However, the degradation was hindered by benzoic acid at low concentrations. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 13–21, 2003 相似文献