全文获取类型
收费全文 | 364164篇 |
免费 | 1573篇 |
国内免费 | 349篇 |
专业分类
化学 | 156517篇 |
晶体学 | 5380篇 |
力学 | 22486篇 |
综合类 | 3篇 |
数学 | 61517篇 |
物理学 | 120183篇 |
出版年
2021年 | 3093篇 |
2020年 | 3412篇 |
2019年 | 4191篇 |
2018年 | 11865篇 |
2017年 | 12350篇 |
2016年 | 10668篇 |
2015年 | 3968篇 |
2014年 | 6937篇 |
2013年 | 12172篇 |
2012年 | 13169篇 |
2011年 | 20451篇 |
2010年 | 14707篇 |
2009年 | 15030篇 |
2008年 | 18747篇 |
2007年 | 21171篇 |
2006年 | 10105篇 |
2005年 | 12406篇 |
2004年 | 10267篇 |
2003年 | 10158篇 |
2002年 | 9155篇 |
2001年 | 7772篇 |
2000年 | 6342篇 |
1999年 | 4526篇 |
1998年 | 4292篇 |
1997年 | 4135篇 |
1996年 | 3904篇 |
1995年 | 3403篇 |
1994年 | 3454篇 |
1993年 | 3455篇 |
1992年 | 3450篇 |
1991年 | 3863篇 |
1990年 | 3865篇 |
1989年 | 3881篇 |
1988年 | 3640篇 |
1987年 | 3720篇 |
1986年 | 3404篇 |
1985年 | 3946篇 |
1984年 | 4195篇 |
1983年 | 3589篇 |
1982年 | 3782篇 |
1981年 | 3468篇 |
1980年 | 3226篇 |
1979年 | 3733篇 |
1978年 | 3808篇 |
1977年 | 3890篇 |
1976年 | 4000篇 |
1975年 | 3726篇 |
1974年 | 3578篇 |
1973年 | 3782篇 |
1972年 | 3218篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Ozonolysis of a Series of Methylated Alkenes: Reaction Rate Coefficients and Gas‐Phase Products 下载免费PDF全文
Tristan Braure Véronique Riffault Alexandre Tomas Romeo Iulian Olariu Cecilia Arsene Yuri Bedjanian Patrice Coddeville 《国际化学动力学杂志》2015,47(9):596-605
The gas‐phase ozonolysis of three methylated alkenes, i.e., trans‐2,2‐dimethyl‐3‐hexene (22dM3H), trans‐2,5‐dimethyl‐3‐hexene (25dM3H), and 4‐methyl‐1‐pentene (4M1P), has been investigated in the presence of sufficient hydroxyl radical scavenger in a laminar flow reactor at ambient temperature (296 ± 2 K) and P = 1 atm of dry air (RH ≤ 5%). Ozone levels in the reactor were monitored by an automatic analyzer. Alkene and gas‐phase product concentrations were determined via online sampling either on three‐bed adsorbent cartridges followed by thermodesorption and GC/FID‐MS analysis or on 2,4‐dinitrophenylhydrazine (DNPH) cartridges for subsequent HPLC/UV analysis. Reaction rate coefficients of (3.38 ± 0.12) × 10?17 for 22dM3H and (2.71 ± 0.26) × 10?17 for 25dM3H, both in cm3 molecule?1 s?1 units, have been obtained under pseudo–first‐order conditions. Primary carbonyl products have been identified for the three investigated alkenes, and branching ratios are reported. In the case of 4M1P ozonolysis, the yield of a Criegee intermediate was indirectly determined. Kinetics and product study results are compared to those of literature when available. This work represents the first investigation of reaction products in the ozonolysis of 22dM3H, 25dM3H, and 4M1P in a flow reactor. 相似文献
63.
64.
65.
66.
67.
68.
69.
Gelikonov G. V. Ksenofontov S. Yu. Shilyagin P. A. Gelikonov V. M. 《Radiophysics and Quantum Electronics》2019,62(3):228-236
Radiophysics and Quantum Electronics - We propose and experimentally test a numerical method for correction of the influence of fluctuations in the distance to objects during noncontact probing in... 相似文献
70.
A.G. Rousskikh A.V. Fedyunin A.P. Artyomov A.S. Zhigalin V.I. Oreshkin 《Current Applied Physics》2019,19(6):704-708
The aim of the study presented in this paper was to characterize quantitatively the erosion of aluminum cathodes in high-current vacuum arcs. The experimental setup comprised two current generators. The first one, capable of generating a current of amplitude up to 350 kA, was used to produce a plasma jet, that is, the object to be investigated. The second generator was used to produce a source of probe radiation for imaging the object under investigation in soft x rays of energy ?ν ≈ 0.5–3 keV. The findings of the study are based on experimental data obtained by electrophysical and radiographic methods. It has been shown that the cathode erosion rate in a high-current vacuum arc is a function of the charge passed through the cathode. 相似文献