全文获取类型
收费全文 | 224668篇 |
免费 | 2839篇 |
国内免费 | 631篇 |
专业分类
化学 | 125848篇 |
晶体学 | 3763篇 |
力学 | 8543篇 |
综合类 | 11篇 |
数学 | 23397篇 |
物理学 | 66576篇 |
出版年
2020年 | 2004篇 |
2019年 | 2210篇 |
2018年 | 2457篇 |
2017年 | 2537篇 |
2016年 | 3967篇 |
2015年 | 2610篇 |
2014年 | 4007篇 |
2013年 | 10317篇 |
2012年 | 7531篇 |
2011年 | 9317篇 |
2010年 | 6375篇 |
2009年 | 6325篇 |
2008年 | 8324篇 |
2007年 | 8264篇 |
2006年 | 7843篇 |
2005年 | 7182篇 |
2004年 | 6520篇 |
2003年 | 5949篇 |
2002年 | 5642篇 |
2001年 | 6473篇 |
2000年 | 4887篇 |
1999年 | 3759篇 |
1998年 | 2999篇 |
1997年 | 2990篇 |
1996年 | 2926篇 |
1995年 | 2673篇 |
1994年 | 2590篇 |
1993年 | 2416篇 |
1992年 | 3052篇 |
1991年 | 2957篇 |
1990年 | 2857篇 |
1989年 | 2915篇 |
1988年 | 2939篇 |
1987年 | 2914篇 |
1986年 | 2776篇 |
1985年 | 3574篇 |
1984年 | 3639篇 |
1983年 | 2808篇 |
1982年 | 3062篇 |
1981年 | 3073篇 |
1980年 | 2833篇 |
1979年 | 3167篇 |
1978年 | 3167篇 |
1977年 | 3258篇 |
1976年 | 3083篇 |
1975年 | 2785篇 |
1974年 | 2750篇 |
1973年 | 2688篇 |
1972年 | 1829篇 |
1968年 | 1780篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
41.
Robert G. W. Anderson 《Ambix》2015,62(4):333-344
Following colonisation of South America by the Spanish, many new naturally occurring substances were sent to Europe. One of these was the silvery, unreactive metal, platinum, discovered in New Grenada in the mid-eighteenth century. It was often found in granular form, associated with gold, and the challenge to chemists was to refine it, produce it as wire or sheet, and determine its chemical properties. This interested the professor of chemistry at the University of Edinburgh, Joseph Black, who was able to obtain samples from London-based Spanish contacts, particularly Ignacio Luzuriaga. This paper examines how Black transmitted his knowledge of the metal to large numbers of students attending his annual course. 相似文献
42.
43.
44.
Ajeel Raheem K. Salim W. S.-I. W. 《Journal of Thermal Analysis and Calorimetry》2021,144(4):1161-1173
Journal of Thermal Analysis and Calorimetry - Over the last few decades, tremendous consideration is drawn towards corrugation surfaces because of their advantages over the improvement in thermal... 相似文献
45.
V. V. Sagaradze N. V. Kataeva V. A. Zavalishin K. A. Kozlov V. V. Makarov A. R. Kuznetsov 《哲学杂志》2020,100(14):1868-1879
ABSTRACT The authors present the results of an investigation in Fe–Ni-Cr austenitic alloys of the low-temperature deformation-induced segregations of nickel that form in the micro regions being (i) located close to grain- and subgrain boundaries and (ii) characteristic of the concentration and magnetic inhomogeneities indicated by the appearance of a dark diffraction contrast at the electron diffraction patterns taken from these regions typical (at the same time) of an enhanced value of Curie temperature. The observed effects were connected with the micro distortions caused by the local change of lattice parameter because of an increase in nickel concentration, as well as in the result of a magnetostriction dilatation. Using methods of the X-ray energy dispersive spectroscopy (XEDS) and atomic-probe body-section radiography (tomography – APT) has made it possible to determine the borders of those regions of austenite that were characteristic of an enhanced concentration of nickel in the fields of the localisation of a deformation-induced segregation of nickel in the vicinity of grain (subgrain) boundaries of austenitic alloys of the types Fe–13Cr–30Ni and Fe–37Ni–3Ti. 相似文献
46.
47.
48.
Hui Li Jian Liu Juan Zhao Huiting He Dr. Dabo Jiang Prof. Steven Robert Kirk Prof. Qiong Xu Dr. Xianxiang Liu Prof. Dulin Yin 《ChemistryOpen》2021,10(4):477-485
A series of tetraimidazolium salts with different anions was prepared and applied in the isomerization of β-pinene oxide. After examining the activity of different catalysts, a remarkable enhancement of the selectivity of perillyl alcohol (47 %) was obtained over [PEimi][HNO3]4 under mild reaction conditions and using DMSO as the solvent. Furthermore, noncovalent interactions between solvent molecules and the catalyst were found by FT-IR spectroscopy and confirmed by computational chemistry. The homogeneous catalyst showed excellent stability and was reused up to six times without significant loss. 相似文献
49.
Mathematical Notes - 相似文献
50.
Acoustical Physics - The problem of pulsed excitation of an acoustic waveguide with a constant cross section is considered. Absorption is ignored. As the most general model of such a waveguide,... 相似文献