全文获取类型
收费全文 | 203篇 |
免费 | 12篇 |
国内免费 | 22篇 |
专业分类
化学 | 113篇 |
晶体学 | 1篇 |
力学 | 1篇 |
综合类 | 5篇 |
数学 | 83篇 |
物理学 | 34篇 |
出版年
2023年 | 5篇 |
2022年 | 9篇 |
2021年 | 7篇 |
2020年 | 1篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 9篇 |
2016年 | 6篇 |
2015年 | 1篇 |
2014年 | 6篇 |
2013年 | 13篇 |
2012年 | 6篇 |
2011年 | 8篇 |
2010年 | 13篇 |
2009年 | 7篇 |
2008年 | 10篇 |
2007年 | 6篇 |
2006年 | 8篇 |
2005年 | 9篇 |
2004年 | 9篇 |
2003年 | 12篇 |
2002年 | 14篇 |
2001年 | 7篇 |
2000年 | 10篇 |
1999年 | 11篇 |
1998年 | 7篇 |
1997年 | 12篇 |
1996年 | 4篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有237条查询结果,搜索用时 953 毫秒
71.
The oxygen stoichiometry in the YBa2Cu3O7−δ high temperature superconductors is studied, using DSC/DTA techniques on samples subjected to different heat and gas treatments.
Characteristic temperature regions of high temperature superconductivity exchange with oxygen in gas phase are identified
and the resulting structural changes are discussed. 相似文献
72.
Xiaojing Xiang 《Annals of the Institute of Statistical Mathematics》1995,47(2):237-251
A Berry-Esseen bound is established for the kernel quantile estimator under various conditions. The results improve an earlier result of Falk (1985,Ann. Statist.,13, 428–433) and rely on the local smoothness of the quantile function. This new Berry-Esseen bound is applied to studying the deficiency of the sample quantile estimator with respect to the kernel quantile estimator. A new result is obtained which is an extension of that in Falk (1985). 相似文献
73.
不依赖图的其它参数, 而主要依据图嵌入在定向曲面上的有关嵌入性质, 该文研究图的最大亏格. 相似文献
74.
我们用显微拉曼、卢瑟福背散射谱、X射线散射和非对称摇摆等实验手段研究了在1 0 - 2 到1 0 - 5帕氧气压下用激光分子束外延技术生长的BaTiO3-x薄膜的结构动力学特性。测量结果表明生长氧压越低,晶格常数c和c/a越大,晶格常数a稍微减小,晶胞体积变大。随着生长氧压的减小,薄膜中氧含量减小。在3 0×1 0 - 5帕氧气压下生长的薄膜中氧缺陷可达0 48,但是样品的四方相结构可以很好的维持。显微拉曼研究进一步确定了样品都是四方相结构。另外,在BaTiO2 52 薄膜的拉曼光谱中发现高频段有两个新峰,其可能是由于氧缺陷导致的二级拉曼散射引起的。随着生长氧压的减小,拉曼峰向低频移动,表明薄膜中的应力减小。同时,拉曼峰变宽,这可能是由于氧缺陷导致的结构畸变引起的。由于在薄膜中存在二维张应力,BaTiO3单晶样品中的结构相变特征在我们的样品中从78到5 5 0K的温度范围内不存在。 相似文献
75.
预反应微波密封消解催化光度法测定尿碘研究 总被引:3,自引:0,他引:3
提出尿碘的预反应微波密封消解催化光度法,该法解决了微波密封消解尿样过程中有机物反应产生气体造成内压过大的关键问题,将消解时间由传统的1h缩短至10min左右,可同时消解上百个样,将该法用于质控样测定,结果符合要求。实际尿样测定RSD≤1.1%,回收率90.1%-110.4%,该法有较好的实用性,可作为常规法测尿碘的等效或取代方法。 相似文献
76.
This paper is devoted to the lower bounds on the maximum genus of graphs. A simple statement of our results in this paper can be expressed in the following form:
Let G be a k-edge-connected graph with minimum degree δ, for each positive integer k(3), there exists a non-decreasing function f(δ) such that the maximum genus γM(G) of G satisfies the relation γM(G)f(δ)β(G), and furthermore that limδ→∞f(δ)=1/2, where β(G)=|E(G)|-|V(G)|+1 is the cycle rank of G.
The result shows that lower bounds of the maximum genus of graphs with any given connectivity become larger and larger as their minimum degree increases, and complements recent results of several authors. 相似文献
77.
78.
Makoto ASAHINA Reiko FUJINAWA Haruhiko FUJIHIRA Yuki MASAHARA-NEGISHI Tomohiro ANDOU Ryuichi TOZAWA Tadashi SUZUKI 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2021,97(2):89
N-Glycanase 1 (NGLY1) deficiency is a congenital disorder caused by mutations in the NGLY1 gene. Because systemic Ngly1−/− mice with a C57BL/6 (B6) background are embryonically lethal, studies on the mechanism of NGLY1 deficiency using mice have been problematic. In this study, B6-Ngly1−/+ mice were crossed with Japanese wild mice-originated Japanese fancy mouse 1 (JF1) mice to produce viable F2 Ngly1−/− mice from (JF1×B6)F1 Ngly1−/+ mice. Systemic Ngly1−/− mice with a JF1 mouse background were also embryonically lethal. Hybrid F1 Ngly1−/− (JF1/B6F1) mice, however, showed developmental delay and motor dysfunction, similar to that in human patients. JF1/B6F1 Ngly1−/− mice showed increased levels of plasma and urinary aspartylglycosamine, a potential biomarker for NGLY1 deficiency. JF1/B6F1 Ngly1−/− mice are a useful isogenic animal model for the preclinical testing of therapeutic options and understanding the precise pathogenic mechanisms responsible for NGLY1 deficiency. 相似文献
79.
In this paper, we mainly investigate the dynamical properties of entire solutions of complex differential equations. With some conditions on coefficients, we prove that the set of common limiting directions of Julia sets of solutions, their derivatives and their primitives must have a definite range of measure. 相似文献
80.
The decycling number of a graph is the smallest number of vertices which can be removed from so that the resultant graph contains no cycle. A decycling set containing exactly vertices of is called a -set. For any decycling set of a -regular graph , we show that , where is the cycle rank of , is the margin number of , and are, respectively, the number of components of and the number of edges in . In particular, for any -set of a 3-regular graph , we prove that , where is the Betti deficiency of . This implies that the decycling number of a 3-regular graph is . Hence for a 3-regular upper-embeddable graph , which concludes the results in [Gao et al., 2015, Wei and Li, 2013] and solves two open problems posed by Bau and Beineke (2002). Considering an algorithm by Furst et al., (1988), there exists a polynomial time algorithm to compute , the cardinality of a maximum nonseparating independent set in a -regular graph , which solves an open problem raised by Speckenmeyer (1988). As for a 4-regular graph , we show that for any -set of , there exists a spanning tree of such that the elements of are simply the leaves of with at most two exceptions providing . On the other hand, if is a loopless graph on vertices with maximum degree at most , then The above two upper bounds are tight, and this makes an extension of a result due to Punnim (2006). 相似文献