全文获取类型
收费全文 | 900篇 |
免费 | 8篇 |
国内免费 | 6篇 |
专业分类
化学 | 518篇 |
晶体学 | 5篇 |
力学 | 26篇 |
数学 | 163篇 |
物理学 | 202篇 |
出版年
2020年 | 7篇 |
2019年 | 12篇 |
2018年 | 9篇 |
2017年 | 8篇 |
2016年 | 11篇 |
2015年 | 7篇 |
2014年 | 14篇 |
2013年 | 51篇 |
2012年 | 38篇 |
2011年 | 32篇 |
2010年 | 24篇 |
2009年 | 28篇 |
2008年 | 26篇 |
2007年 | 40篇 |
2006年 | 37篇 |
2005年 | 19篇 |
2004年 | 27篇 |
2003年 | 32篇 |
2002年 | 19篇 |
2001年 | 23篇 |
2000年 | 27篇 |
1999年 | 19篇 |
1998年 | 14篇 |
1997年 | 10篇 |
1996年 | 7篇 |
1995年 | 15篇 |
1994年 | 17篇 |
1993年 | 11篇 |
1992年 | 12篇 |
1991年 | 8篇 |
1990年 | 13篇 |
1989年 | 8篇 |
1988年 | 13篇 |
1987年 | 8篇 |
1985年 | 17篇 |
1984年 | 17篇 |
1983年 | 16篇 |
1982年 | 17篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 12篇 |
1978年 | 16篇 |
1977年 | 15篇 |
1975年 | 12篇 |
1974年 | 11篇 |
1973年 | 10篇 |
1972年 | 14篇 |
1971年 | 14篇 |
1970年 | 11篇 |
1969年 | 13篇 |
排序方式: 共有914条查询结果,搜索用时 15 毫秒
1.
In this paper, we investigate the evolution of joint invariants under invariant geometric flows using the theory of equivariant moving frames and the induced invariant discrete variational complex. For certain arc length preserving planar curve flows invariant under the special Euclidean group , the special linear group , and the semidirect group , we find that the induced evolution of the discrete curvature satisfies the differential‐difference mKdV, KdV, and Burgers' equations, respectively. These three equations are completely integrable, and we show that a recursion operator can be constructed by precomposing the characteristic operator of the curvature by a certain invariant difference operator. Finally, we derive the constraint for the integrability of the discrete curvature evolution to lift to the evolution of the discrete curve itself. 相似文献
2.
Fixed-frequency and threshold photoelectron spectra have been recorded for ionization from the S ls shells in SF6, CS2 and COS, the Si 1s shells in SiH4 and SiCl4 and the Cl 1s shell in SiCl4 using synchrotron radiation. Fixed-frequency spectra generally showed a single strong ionization feature with associated weak satellite structure due to excited ionized states. Threshold spectra closely resembled X-ray absorption spectra but with an additional feature due to direct ionization. In cases where resonant process enhanced the NEXAFS spectrum direct ionization was not observed. 相似文献
3.
Y. Zhang T. M. Benson P. Sewell A. Vukovic D. Zhang W. J. Pan A Loni D. Furniss A. B. Seddon 《Optical and Quantum Electronics》2006,38(1-3):97-110
This paper presents our recent simulation results and novel designs of single mode large cross-section glass-based waveguides for photonic integrated circuits (PICs). Simulations were performed using an in-house Finite Difference (FD) based mode solver and the FD Beam propagation Method (FD-BPM). Our simulation results show that this innovative technology could provide a simplified means to couple optical energy efficiently between optical components in a single chip. This would provide the base for the future large-scale integration of optical components in PICs. The novel idea of using single mode large cross-section glass-based waveguides as an optical integration platform is an evolutionary innovative solution for the monolithic integration of optical components, in which the glass-based structures act both as waveguides and as an optical bench for integration. This allows easy and efficient optical coupling between optical components and optical fibres, removing costly and tedious alignment problems and considerably reducing optical coupling losses in PICs. We expect that the glass-based waveguide PICs technology will enable the emergence of a new generation of compact, reliable, high speed, and multifunctional devices. 相似文献
4.
5.
6.
7.
8.
An azacrown system has been developed for selective membrane binding of phosphatidylinositol-4,5-bis(phosphate) recognition. Neutral and cationic forms of the metacyclophane macrocycles have been synthesized by divergent routes in acceptable yields. Such diversity will be useful in identifying anion receptors that operate best at membrane interfaces. 相似文献
9.
10.
Skehel JM Schneider K Murphy N Graham A Benson GM Cutler P Camilleri P 《Electrophoresis》2000,21(12):2540-2545
Apolipoprotein E (ApoE) plays an important role in cholesterol and triglyceride metabolism, being one of the major structural components of chylomicrons and very low density lipoprotein (VLDL) remnants. ApoE functions as a ligand in the receptor-mediated uptake of these remnants from the blood by the liver. A variant form of ApoE, apolipoprotein E*3-Leiden, shows reduced affinity for the low density lipoprotein (LDL) receptor, and results in the dominant expression of type III hyperlipoproteinemia. Two-dimensional electrophoresis (2-DE) has been used to characterise protein expression in serum samples from control and transgenic mice expressing the human ApoE*3-Leiden mutation, fed a cholesterol-rich diet, and transgenic mice fed a normal diet. For the identification of proteins, single silver-stained spots were excised from the 2-DE gels and subjected to in-gel enzymatic digestion. Extracted peptides were analysed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). This proteomic approach has enabled the ApoE*3-Leiden variant to be positioned in a 2-DE separation of serum proteins, and has identified changes in the expression of haptoglobin, indicating that this protein may provide a marker for the potential onset of atherosclerosis. 相似文献