全文获取类型
收费全文 | 437198篇 |
免费 | 3413篇 |
国内免费 | 1197篇 |
专业分类
化学 | 234859篇 |
晶体学 | 6719篇 |
力学 | 18989篇 |
综合类 | 15篇 |
数学 | 50488篇 |
物理学 | 130738篇 |
出版年
2019年 | 4018篇 |
2018年 | 5555篇 |
2017年 | 5464篇 |
2016年 | 7805篇 |
2015年 | 4567篇 |
2014年 | 7309篇 |
2013年 | 18198篇 |
2012年 | 13571篇 |
2011年 | 16559篇 |
2010年 | 11793篇 |
2009年 | 11508篇 |
2008年 | 15673篇 |
2007年 | 15924篇 |
2006年 | 14866篇 |
2005年 | 13452篇 |
2004年 | 12123篇 |
2003年 | 11052篇 |
2002年 | 10939篇 |
2001年 | 11814篇 |
2000年 | 9289篇 |
1999年 | 7098篇 |
1998年 | 6232篇 |
1997年 | 6250篇 |
1996年 | 5857篇 |
1995年 | 5165篇 |
1994年 | 5359篇 |
1993年 | 5116篇 |
1992年 | 5682篇 |
1991年 | 5706篇 |
1990年 | 5593篇 |
1989年 | 5427篇 |
1988年 | 5465篇 |
1987年 | 5355篇 |
1986年 | 5117篇 |
1985年 | 6770篇 |
1984年 | 7128篇 |
1983年 | 5857篇 |
1982年 | 6253篇 |
1981年 | 6070篇 |
1980年 | 5843篇 |
1979年 | 6025篇 |
1978年 | 6392篇 |
1977年 | 6315篇 |
1976年 | 6377篇 |
1975年 | 5954篇 |
1974年 | 5994篇 |
1973年 | 6282篇 |
1972年 | 4393篇 |
1971年 | 3722篇 |
1967年 | 3695篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
We show that, in dimensions equal or greater than three, classical strings do not join or split. This is part of a no-interaction theorem that is also proved. The quantum theory is considered. 相似文献
13.
D. N. Karimov E. A. Krivandina Z. I. Zhmurova B. P. Sobolev V. A. Bezhanov S. P. Chernov G. M. Shapochkin 《Crystallography Reports》2006,51(6):1009-1015
Crystalline materials that are transparent in the vacuum UV spectral region and currently used have been reviewed. Transmission of crystals of solid solutions with the fluorite structure Ca1?x R xF2+x (R = Sc, Y, La, Yb, Lu) in the UV and vacuum UV spectral regions has been investigated. It is shown that application of different methods of purification of fluorides from some impurities can significantly improve the optical quality of fluoride multicomponent crystals in the short-wavelength spectral region. 相似文献
14.
15.
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
16.
K. C. Kumara Swamy E. Balaraman M. Phani Pavan N. N. Bhuvan Kumar K. Praveen Kumar N. Satish Kumar 《Journal of Chemical Sciences》2006,118(6):495-501
The diversity of products in the reaction of diethyl azodicarboxylate (DEAD)/diisopropyl azodicarboxylate (DIAD) and activated
acetylenes with PIII compounds bearing oxygen or nitrogen substituents is discussed. New findings that are useful in understanding the nature
of intermediates involved in the Mitsunobu reaction are highlighted. X-ray structures of two new compounds (2-t-Bu-4-MeC6H3O)P (μ-N-t-Bu)2P+[(NH-t-Bu)N[(CO2]-i-Pr)(HNCO2-i-Pr)]](Cl-)(2-t-Bu-4-MeC6H3OH)(23)and [CH2(6-t-Bu-4-Me-C6H2O)2P(O)C(CO2Me)C-(CO2Me)CClNC(O)Cl] (33) are also reported. The structure of23 is close to one of the intermediates proposed in the Mitsunobu reaction. 相似文献
17.
H. Moers H. Klewe-Nebenius G. Pfennig und H. J. Ache 《Fresenius' Journal of Analytical Chemistry》1987,329(2-3):361-366
Summary The adsorption of gaseous molecular iodine on clean silver surfaces proceeds in the first stage by dissociative chemisorption. After the formation of half a monolayer of chemisorbed iodine atoms the formation of silver iodide begins, which forms a very regular overlayer on top of the substrate. Both iodine species can be distinguished due to a difference in chemical shift of the M4N4, 5N4, 5-Auger transitions. After completion of this overlayer further iodine uptake is slowed down significantly. Above an overlayer thickness of about 10 nm a further progress of the reaction cannot be followed anymore due to the limited information depth of XPS. 相似文献
18.
19.
20.
The title compound is a centrosymmetric dimer with each cadmium in a distorted CdS5 square pyramidal geometry. The Cd–S bond distances range from 2.5626(11) to 2.8459(11) Å. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献