全文获取类型
收费全文 | 1358篇 |
免费 | 24篇 |
国内免费 | 12篇 |
专业分类
化学 | 929篇 |
晶体学 | 21篇 |
力学 | 18篇 |
数学 | 276篇 |
物理学 | 150篇 |
出版年
2022年 | 19篇 |
2021年 | 19篇 |
2020年 | 12篇 |
2018年 | 22篇 |
2017年 | 13篇 |
2016年 | 34篇 |
2015年 | 11篇 |
2014年 | 31篇 |
2013年 | 59篇 |
2012年 | 45篇 |
2011年 | 49篇 |
2010年 | 34篇 |
2009年 | 34篇 |
2008年 | 53篇 |
2007年 | 43篇 |
2006年 | 45篇 |
2005年 | 44篇 |
2004年 | 33篇 |
2003年 | 32篇 |
2002年 | 30篇 |
2001年 | 12篇 |
2000年 | 14篇 |
1999年 | 25篇 |
1998年 | 21篇 |
1997年 | 22篇 |
1996年 | 15篇 |
1995年 | 22篇 |
1994年 | 20篇 |
1991年 | 21篇 |
1990年 | 11篇 |
1989年 | 12篇 |
1988年 | 19篇 |
1987年 | 25篇 |
1986年 | 13篇 |
1984年 | 13篇 |
1983年 | 18篇 |
1982年 | 17篇 |
1981年 | 23篇 |
1980年 | 25篇 |
1978年 | 20篇 |
1977年 | 19篇 |
1976年 | 22篇 |
1975年 | 19篇 |
1974年 | 15篇 |
1973年 | 35篇 |
1972年 | 22篇 |
1971年 | 14篇 |
1970年 | 22篇 |
1967年 | 12篇 |
1962年 | 11篇 |
排序方式: 共有1394条查询结果,搜索用时 0 毫秒
121.
122.
123.
124.
In this paper, the authors continue their investigation of loops which give rise to alternative loop rings. If the coefficient ring has characteristic 2, these loops turn out to form a surprisingly wide class, in contrast to the situation of characteristic ≠ 2. This paper describes many properties of this class, includes diverse examples of Moufang loops which are united by the fact that they have loop rings which are alternative, and discusses analogues in loop theory of a number of important group theoretic constructions. 相似文献
125.
126.
127.
128.
The analysis of mitochondria by capillary electrophoresis usually takes longer than 20 min per replicate which may compromise the quality of the mitochondria due to degradation. In addition, low sample consumption may be beneficial in the analysis of rare or difficult samples. In this report, we demonstrate the ability to analyze individual mitochondrial events in picoliter-volume samples (approximately 80 pL) taken from a bovine liver preparation using microchip capillary electrophoresis with laser-induced fluorescence detection (micro-chip CE-LIF). Using a commercial "double-T" glass microchip, the sample was electrokinetically loaded in the "double-T" intersection and then subjected to electrophoretic separation along the main separation channel. In order to decrease interactions of mitochondria with channel walls during the analysis, poly(vinyl alcohol) was used as a dynamic coating. This procedure eliminates the need for complicated covalent surface modifications within the channels that were previously used in capillary electrophoresis methods. For analysis, mitochondria, isolated from bovine liver tissue, were selectively labelled using 10-nonyl acridine orange (NAO). The results consist of electropherograms where each mitochondrial event is a narrow spike (240 +/- 44 ms). While the spike intensity is representative of its NAO content, its migration time is used to calculate and describe its electrophoretic mobility, which is a property still largely unexplored for intracellular organelles. The five-fold decrease in separation time (4 min for microchip versus 20 min for capillary electrophoresis) makes microchip electrophoretic separations of organelles a faster, sensitive, low-sample volume alternative for the characterization of individual organelle properties and for investigations of subcellular heterogeneity. 相似文献
129.
Starting from a five-dimensional (5D) vacuum theory of gravity where the extra coordinate is considered as non-compact, we investigate the possibility of inducing four-dimensional (4D) phantom scenarios by applying form-invariance symmetry transformations. In particular we obtain phantom scenarios for two cosmological frameworks. In the first framework we deal with an induced 4D de Sitter expansion and in the second one a 4D induced model where the expansion of the universe is dominated by a decreasing cosmological parameter Λ(t) is discussed. 相似文献
130.
The degradation of azure B dye (C15H16ClN3S; AB) has been studied by Fenton, sonolysis and sono-electroFenton processes employing ultrasound at 23 kHz and the electrogeneration of H2O2 at the reticulated vitreous carbon electrode. It was found that the dye degradation followed apparent first-order kinetics in all the degradation processes tested. The rate constant was affected by both the pH of the solution and initial concentration of Fe2+, with the highest degradation obtained at pH between 2.6 and 3. The first-order rate constant decreased in the following order: sono-electroFenton > Fenton > sonolysis. The rate constant for AB degradation by sono-electroFenton is ∼10-fold that of sonolysis and ∼2-fold the one obtained by Fenton under silent conditions. The chemical oxygen demand was abated ∼68% and ∼85% by Fenton and sono-electroFenton respectively, achieving AB concentration removal over 90% with both processes. 相似文献