全文获取类型
收费全文 | 1286篇 |
免费 | 35篇 |
国内免费 | 9篇 |
专业分类
化学 | 818篇 |
晶体学 | 7篇 |
力学 | 91篇 |
数学 | 147篇 |
物理学 | 267篇 |
出版年
2022年 | 27篇 |
2021年 | 19篇 |
2020年 | 7篇 |
2019年 | 16篇 |
2018年 | 8篇 |
2017年 | 7篇 |
2016年 | 25篇 |
2015年 | 15篇 |
2014年 | 33篇 |
2013年 | 54篇 |
2012年 | 72篇 |
2011年 | 93篇 |
2010年 | 40篇 |
2009年 | 63篇 |
2008年 | 80篇 |
2007年 | 61篇 |
2006年 | 70篇 |
2005年 | 68篇 |
2004年 | 37篇 |
2003年 | 44篇 |
2002年 | 38篇 |
2001年 | 27篇 |
2000年 | 31篇 |
1999年 | 12篇 |
1998年 | 10篇 |
1997年 | 15篇 |
1996年 | 31篇 |
1995年 | 17篇 |
1994年 | 14篇 |
1993年 | 23篇 |
1992年 | 21篇 |
1991年 | 23篇 |
1990年 | 15篇 |
1989年 | 14篇 |
1988年 | 15篇 |
1987年 | 8篇 |
1986年 | 13篇 |
1985年 | 21篇 |
1984年 | 12篇 |
1983年 | 10篇 |
1982年 | 15篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1978年 | 7篇 |
1977年 | 24篇 |
1976年 | 11篇 |
1974年 | 7篇 |
1973年 | 6篇 |
1972年 | 5篇 |
1971年 | 5篇 |
排序方式: 共有1330条查询结果,搜索用时 15 毫秒
101.
AbstractThe photochemical reactions of eight carbohydrate trifluoromethanesulfonates (triflates) have been investigated in methanol in the presence of potassium iodide. For those compounds which do not contain an aromatic chromophore, photolysis results in two types of reaction. One type produces deoxy sugars by replacement of the trifluoromethylsulfonyloxy (triflyloxy) group with a hydrogen atom. The second type of reaction generates partially protected sugars by replacement of the trifluoromethylsulfonyl (triflyl) group with a hydrogen atom. When the triflate being irradiated also has a protecting group containing an aromatic ring (i.e., benzyl, benzoyl, or p-tolylsulfonyl group), removal of the protecting group is the exclusive reaction pathway. 相似文献
102.
Wen-Hua Zhang Sheau Wei Chien T.S. Andy Hor 《Coordination chemistry reviews》2011,255(17-18):1991-2024
This review summarises some recent developments of the metal complexes of hetero-functional hybrid ligands of C-, N-, O-, P- and S-donors. It highlights the ligand designs, synthetic pathways, structural motifs and catalytic prowess of these complexes. 相似文献
103.
Extracting and concentrating mitochondrial protein complexes from gel strips after blue native PAGE (BN‐PAGE) can be daunting tasks using the traditional methods, such as electroelution, passive diffusion and centrifugal concentration. We present a simplified gel electrophoresis method to concentrate mitochondrial protein complexes with excellent recovery rate. Mitochondrial complex I present in a long gel strip from BN‐PAGE can be easily concentrated into a 0.8 cm gel strip when a second BN‐PAGE is performed with a Y‐shaped gel and the addition of 0.01% n‐dodecyl β‐D ‐maltoside and 0.001% SDS in the cathode buffer. Once completed, the concentrated protein complex in the gel strip is ready for SDS‐PAGE or proteomic studies. 相似文献
104.
The purpose of this paper is to apply a numerical technique in solving problems involving light beams in a random medium. The technique starts by generating numerically sample media with prescribed statistical properties. Rays are then traced in these sample media and the ray statistics are compiled. These statistics are utilized to find the mean square displacement and distribution of a beam. Problems on beam broadening and distortion of radiation patterns are considered. Fluctations in wave amplitude and phase are also investigated. When possible, the numerical results are compared with the analytical results and experimental results.It seems that the numerical technique has a potential to solve a great variety of problems. This is because it does not have severe restrictive conditions as those imposed on the analytic formulation. For example the technique is equally applicable when the irregularities are anisotropic, or when the background medium is inhomogeneous, or when the background is anistropic, or when there exist background wind. Some of these are discussed. 相似文献
105.
Reflection of an obliquely incident solitary wave onto a vertical wall is studied analytically and experimentally. We use
the Kadomtsev-Petviashivili (KP) equation to analyze the evolution and its asymptotic state. Laboratory experiments are performed
using the laser induced fluorescent (LIF) technique, and detailed features and amplifications at the wall are measured. Due
to the lack of physical interpretation of the theory, the numerical results were previously thought not in good agreement
with the theory. With proper treatment, we demonstrate that the KP theory provides an excellent model to predict the present
laboratory results as well as the previous numerical results. The KP theory also indicates that the present laboratory apparatus
is too short to achieve the asymptotic state. The laboratory and numerical results suggest that the maximum of the predicted
four-fold amplification would be difficult to be realized in the real-fluid environment. The reality of this amplification
remains obscure. 相似文献
106.
107.
In this paper, we compute the congruences of Catalan and Motzkin numbers modulo 4 and 8. In particular, we prove the conjecture proposed by Deutsch and Sagan that no Motzkin number is a multiple of 8. 相似文献
108.
Yi-Chun Chen Jin-Ming Chen Chia-Haw Hsu Jyh-Fu Lee Jien-Wei Yeh Han C. Shih 《Solid State Ionics》2009,180(20-22):1215-1219
Recently, lithium bi-metal phosphates (LiM′M″PO4) have been synthesized for use as cathode materials in order to increase cell voltages and electrical performances. In this work, we have substituted Mn2+ at the 4c site of LiFePO4 to prepare the lithium bi-metal phosphate LiMn0.25Fe0.75PO4 and have found that it greatly enhances the cell voltage. At a 0.05 C discharge rate, the cell capacity was about 153 mAhg− 1 and the average working voltage rose to 3.53 V due to the Mn substitution. However, the capacity and working voltage both decrease as the discharge rate increases. By in-situ metal K-edge absorption analysis, it reveals that the substituted metal Mn2+ does not work completely at a higher discharge rate, due to poor electrical conductivity and a serious Jahn–Teller effect. 相似文献
109.
110.