全文获取类型
收费全文 | 111681篇 |
免费 | 7599篇 |
国内免费 | 6969篇 |
专业分类
化学 | 65994篇 |
晶体学 | 1592篇 |
力学 | 6294篇 |
综合类 | 523篇 |
数学 | 13247篇 |
物理学 | 38599篇 |
出版年
2023年 | 980篇 |
2022年 | 2174篇 |
2021年 | 2671篇 |
2020年 | 2837篇 |
2019年 | 3045篇 |
2018年 | 3352篇 |
2017年 | 3340篇 |
2016年 | 4138篇 |
2015年 | 3098篇 |
2014年 | 4333篇 |
2013年 | 5961篇 |
2012年 | 6223篇 |
2011年 | 6534篇 |
2010年 | 5174篇 |
2009年 | 5141篇 |
2008年 | 5448篇 |
2007年 | 5032篇 |
2006年 | 4604篇 |
2005年 | 4015篇 |
2004年 | 3548篇 |
2003年 | 3102篇 |
2002年 | 3192篇 |
2001年 | 2865篇 |
2000年 | 2232篇 |
1999年 | 1811篇 |
1998年 | 1722篇 |
1997年 | 1459篇 |
1996年 | 1401篇 |
1995年 | 1166篇 |
1994年 | 1238篇 |
1993年 | 1164篇 |
1992年 | 1119篇 |
1991年 | 1166篇 |
1990年 | 1169篇 |
1989年 | 1079篇 |
1988年 | 940篇 |
1987年 | 930篇 |
1986年 | 903篇 |
1985年 | 941篇 |
1984年 | 928篇 |
1983年 | 831篇 |
1982年 | 818篇 |
1979年 | 812篇 |
1978年 | 815篇 |
1977年 | 809篇 |
1976年 | 924篇 |
1975年 | 815篇 |
1974年 | 852篇 |
1973年 | 849篇 |
1972年 | 755篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
Yu. A. Kumzerov L. S. Parfen’eva I. A. Smirnov H. Misiorek J. Mucha A. Jezowski 《Physics of the Solid State》2003,45(1):57-60
The thermal conductivity of crystalline chrysotile asbestos made up of hollow tubular Mg3Si2O5(OH)4 filaments is measured in the range 5–300 K. The paper discusses the possibility of using this material in studies of the thermal conductivity of thin filaments of metals and semiconductors incorporated into the channels of crystalline chrysotile asbestos tubes. 相似文献
32.
Jihua Zhang Xi WangWeidong Yu Tao FengFumin Zhang Zhihong ZhengQiong Li Xianghuai Liu 《Solid State Communications》2003,127(4):289-293
Effects of ion impinging on the microstructure and field electron emission properties of screen-printed carbon nanotube films were investigated. We observed that the plasma treatment modified the microstructure of CNTs along with the remarkable increase of emission site density. With the prolongation of ion impinging time, the emission current falls down first, and then rises up to higher than that of the untreated films. It is proposed that the change of emission characteristics is due to the different emission mechanisms. After the treatment, electrons are emitted predominantly from the nano-nodes on the tube wall instead from the nanotube tips. 相似文献
33.
A lithium(I) coordination polymer has been formed from LiClO4 and the 2,2′‐bipyrimidine (bpym) ligand in which each square pyramidal lithium(I) atom is coordinated in the basal plane by four nitrogen donor atoms derived from two bpym ligands and one water molecule at the apical position. These are connected into a layer structure via hydrogen‐bonding interactions involving the perchlorate anions. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
34.
Porous silicon (PS) exhibits several photoluminescence (PL) bands, whose spectral position and intensity depend strongly on the actual conditions of preparation of PS, its treatment, and subsequent use. The PS PL band peaking at about 1.8 eV and usually assigned to the intrinsic emission of silicon nanocrystals was studied. It was shown that the temperature-induced variation of the PL kinetics in the 80 to 300-K interval follows a complex pattern and depends noticeably on the actual point on the band profile. The temperature behavior of PL decay in the 1.8-eV band is determined by the electron-hole recombination rate within a nanocrystal and the cascade carrier transitions from small to large nanocrystals, with an attendant decrease in energy. 相似文献
35.
Solid state nuclear track detectors are commonly used for measurements of concentrations of radon gas and/or radon progeny. All these measurements depend critically on the thickness of the removed layer during etching. However, the thickness of removed layer calculated using the etching period does not necessarily provide a sufficiently accurate measure of the thickness. For example, the bulk etch rate depends on the strength of stirring during etching for the LR 115 detector. We propose here to measure the thickness of the removed layer by using energy-dispersive X-ray fluorescence spectrometry. In the present work, a reference silver nitrate pellet is placed beneath the LR 115 detector, and the fluorescence X-ray intensity for silver is then measured. We have found a linear relationship between the X-ray intensity and the thickness of the removed layer for LR 115 detector. This provides a fast method to measure the thickness of removed layer from etching of LR 115 detector. However, this method was found to be inapplicable for the CR-39 detector. Therefore, alternative methods have yet to be explored for the CR-39 detector. 相似文献
36.
Some possible errors in determining the gravity anomalies are discussed. Such errors may be caused by an inaccurate calibration of the gravimeter used in an airborne survey system. An approach based on wavelet decompositions is proposed for its additional calibration with the use of flight data obtained during repeated flights. 相似文献
37.
The aim of this study is to construct a quantitative characteristic for the degree of gaze stabilization on a visual target with consideration of physiological constraints. A quality criterion for visual tracking during optokinetic vestibulocervical nystagmus is proposed. The index of imaginary tracking during rotation in the dark allows one to speak of a difference in the image stabilization quality between a healthy person and a patient. Experimental nystagmus data are used to calculate the quality index of visual tracking and the index of imaginary tracking. 相似文献
38.
A. V. Ivanov M. Yu. Tsentalovich E. G. Kogan L. G. Tomilova N. S. Zefirov 《Russian Chemical Bulletin》2008,57(8):1676-1679
The chlorination of benzene, toluene, and o-xylene with molecular chlorine in the presence of the phthalocyanine complexes of different structures was studied. The transformations
of the catalysts during the reaction were investigated.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1644–1647, August, 2008. 相似文献
39.
40.
M. K. Bratenko Yu. V. Kadel’nik V. A. Chornous M. V. Vovk 《Russian Journal of Organic Chemistry》2008,44(2):247-250
Oximes of 4-(4-pyrazolyl)-3-buten-2-onees obtained by successive reaction of 3-aryl-4-formylpyrazoles with acetone and hydroxylamine at the treatment with iodine suffered an oxidative cyclization yielding 3-aryl-4-(5-isoxazolyl)pyrazoles. 相似文献