全文获取类型
收费全文 | 4066篇 |
免费 | 174篇 |
国内免费 | 16篇 |
专业分类
化学 | 2688篇 |
晶体学 | 13篇 |
力学 | 103篇 |
数学 | 646篇 |
物理学 | 806篇 |
出版年
2023年 | 33篇 |
2022年 | 29篇 |
2021年 | 89篇 |
2020年 | 77篇 |
2019年 | 79篇 |
2018年 | 58篇 |
2017年 | 57篇 |
2016年 | 146篇 |
2015年 | 120篇 |
2014年 | 118篇 |
2013年 | 211篇 |
2012年 | 257篇 |
2011年 | 305篇 |
2010年 | 130篇 |
2009年 | 129篇 |
2008年 | 234篇 |
2007年 | 229篇 |
2006年 | 223篇 |
2005年 | 207篇 |
2004年 | 178篇 |
2003年 | 144篇 |
2002年 | 130篇 |
2001年 | 70篇 |
2000年 | 64篇 |
1999年 | 51篇 |
1998年 | 40篇 |
1997年 | 26篇 |
1996年 | 52篇 |
1995年 | 34篇 |
1994年 | 34篇 |
1993年 | 40篇 |
1992年 | 52篇 |
1991年 | 30篇 |
1990年 | 23篇 |
1989年 | 26篇 |
1988年 | 38篇 |
1987年 | 25篇 |
1986年 | 20篇 |
1985年 | 29篇 |
1984年 | 22篇 |
1983年 | 31篇 |
1982年 | 37篇 |
1981年 | 30篇 |
1980年 | 26篇 |
1979年 | 28篇 |
1978年 | 21篇 |
1977年 | 22篇 |
1976年 | 28篇 |
1975年 | 26篇 |
1974年 | 21篇 |
排序方式: 共有4256条查询结果,搜索用时 31 毫秒
1.
Dr. Yolimar Gil Dr. Alejandro Castro-Alvarez Dr. Pablo Fuentealba Prof. Evgenia Spodine Dr. Daniel Aravena 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(48):e202200336
Enhancement of axial magnetic anisotropy is the central objective to push forward the performance of Single-Molecule Magnet (SMM) complexes. In the case of mononuclear lanthanide complexes, the chemical environment around the paramagnetic ion must be tuned to place strongly interacting ligands along either the axial positions or the equatorial plane, depending on the oblate or prolate preference of the selected lanthanide. One classical strategy to achieve a precise chemical environment for a metal centre is using highly structured, chelating ligands. A natural approach for axial-equatorial control is the employment of macrocycles acting in a belt conformation, providing the equatorial coordination environment, and leaving room for axial ligands. In this review, we present a survey of SMMs based on the macrocycle belt motif. Literature systems are divided in three families (crown ether, Schiff-base and metallacrown) and their general properties in terms of structural stability and SMM performance are briefly discussed. 相似文献
2.
3.
4.
D. I. Naiduss W. W. Kiesewetter S. L. Dikanskaja J. Schapiro R. Meurice J. Cartiaux E. F. Posorski G. N. Murthy S. Mihaéloff A. D. Rich J. J. Vollertsen Gh. Ghimicescu G. Kotsis C. T. Townsend J. A. Esty F. C. Baselt R. Dubrisay J. Gascon E. R. Scheggia K. M. Renner E. S. Miller C. A. Mitchell A. G. Sossin und S. E. Spektor 《Fresenius' Journal of Analytical Chemistry》1939,118(1-2):48-51
Ohne Zusammenfassung 相似文献
5.
M. Missous C. Mitchell J. Sly K. T. Lai R. Gupta S. K. Haywood 《Physica E: Low-dimensional Systems and Nanostructures》2004,20(3-4):496
Highly strained quantum cascade laser (QCL) and quantum well infrared photodetector (QWIPs) structures based on InxGa(1−x)As−InyAl(1−y)As (x>0.8,y<0.3) layers have been grown by molecular beam epitaxy. Conditions of exact stoichiometric growth were used at a temperature of 420°C to produce structures that are suitable for both emission and detection in the 2–5 μm mid-infrared regime. High structural integrity, as assessed by double crystal X-ray diffraction, room temperature photoluminescence and electrical characteristics were observed. Strong room temperature intersubband absorption in highly tensile strained and strain-compensated In0.84Ga0.16As/AlAs/In0.52Al0.48As double barrier quantum wells grown on InP substrates is demonstrated. Γ–Γ intersubband transitions have been observed across a wide range of the mid-infrared spectrum (2–7 μm) in three structures of differing In0.84Ga0.16As well width (30, 45, and 80 Å). We demonstrate short-wavelength IR, intersubband operation in both detection and emission for application in QC and QWIP structures. By pushing the InGaAs–InAlAs system to its ultimate limit, we have obtained the highest band offsets that are theoretically possible in this system both for the Γ–Γ bands and the Γ–X bands, thereby opening up the way for both high power and high efficiency coupled with short-wavelength operation at room temperature. The versatility of this material system and technique in covering a wide range of the infrared spectrum is thus demonstrated. 相似文献
6.
7.
Juan Pablo Vielma 《Operations Research Letters》2007,35(1):29-35
Two independent proofs of the polyhedrality of the split closure of mixed integer linear program have been previously presented. Unfortunately neither of these proofs is constructive. In this paper, we present a constructive version of this proof. We also show that split cuts dominate a family of inequalities introduced by Köppe and Weismantel. 相似文献
8.
Chaotic dynamics in open systems produces fractals. This can be seen, for example, in the ionization of an electron from a
hydrogen atom in applied parallel electric and magnetic fields. We summarize some of our recent work on the order that can
be found in these fractals. 相似文献
9.
We obtain Dirac’s classic monopole charge quantization from the point of view of geometric quantization and demonstrate how this leads to the conclusion that the electromagnetic field is a U(1)-gauge field. 相似文献
10.