全文获取类型
收费全文 | 4176篇 |
免费 | 183篇 |
国内免费 | 20篇 |
专业分类
化学 | 2565篇 |
晶体学 | 58篇 |
力学 | 93篇 |
数学 | 623篇 |
物理学 | 1040篇 |
出版年
2023年 | 29篇 |
2022年 | 61篇 |
2021年 | 86篇 |
2020年 | 72篇 |
2019年 | 82篇 |
2018年 | 57篇 |
2017年 | 56篇 |
2016年 | 151篇 |
2015年 | 132篇 |
2014年 | 122篇 |
2013年 | 191篇 |
2012年 | 255篇 |
2011年 | 302篇 |
2010年 | 129篇 |
2009年 | 145篇 |
2008年 | 224篇 |
2007年 | 223篇 |
2006年 | 206篇 |
2005年 | 183篇 |
2004年 | 167篇 |
2003年 | 111篇 |
2002年 | 136篇 |
2001年 | 63篇 |
2000年 | 56篇 |
1999年 | 52篇 |
1998年 | 39篇 |
1997年 | 42篇 |
1996年 | 49篇 |
1995年 | 32篇 |
1994年 | 51篇 |
1993年 | 45篇 |
1992年 | 36篇 |
1991年 | 41篇 |
1990年 | 42篇 |
1989年 | 26篇 |
1988年 | 47篇 |
1987年 | 48篇 |
1986年 | 18篇 |
1985年 | 42篇 |
1984年 | 32篇 |
1983年 | 32篇 |
1982年 | 26篇 |
1981年 | 43篇 |
1980年 | 33篇 |
1979年 | 31篇 |
1978年 | 25篇 |
1976年 | 22篇 |
1975年 | 25篇 |
1974年 | 18篇 |
1973年 | 20篇 |
排序方式: 共有4379条查询结果,搜索用时 78 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.
Alloys of the systems Fe–Al (mixable over the whole concentration range) and Fe–Mg (insoluble with each other) were produced by implantation of Fe ions into Al and Mg, respectively. The implantation energy was 200 keV and the ion doses ranged from 1 × 1014 to 9 × 1017cm-2The obtained implantation profiles were determined by Auger electron spectroscopy depth profiling. Maximum iron concentrations reached were up to 60 at.% for implantation into Al and 94 at.% for implantation into Mg. Phase analysis of the implanted layers was performed by conversion electron Mössbauer spectroscopy and X‐ray diffraction. For implantation into Mg, two different kinds of Mössbauer spectra were obtained: at low doses paramagnetic doublets indicating at least two different iron sites and at high doses a dominant ferromagnetic six‐line‐pattern with a small paramagnetic fraction. The X‐ray diffraction pattern concluded that in the latter case a dilated αiron lattice is formed. For implantation into Al, the Mössbauer spectra were doublet structures very similar to those obtained at amorphous Fe–Al alloys produced by rapid quenching methods. They also indicated at least two different main iron environments. For the highest implanted sample a ferromagnetic six‐line‐pattern with magnetic field values close to those of Fe3Al appeared. 相似文献
5.
6.
For a graph G and a positive integer m, G(m) is the graph obtained from G by replacing every vertex by an independent set of size m and every edge by m2 edges joining all possible new pairs of ends. If G triangulates a surface, then it is easy to see from Euler's formula that G(m) can, in principle, triangulate a surface. For m prime and at least 7, it has previously been shown that in fact G(m) does triangulate a surface, and in fact does so as a “covering with folds” of the original triangulation. For m = 5, this would be a consequence of Tutte's 5‐Flow Conjecture. In this work, we investigate the case m = 2 and describe simple classes of triangulations G for which G(2) does have a triangulation that covers G “with folds,” as well as providing a simple infinite class of triangulations G of the sphere for which G(2) does not triangulate any surface. © 2003 Wiley Periodicals, Inc. J Graph Theory 43: 79–92, 2003 相似文献
7.
8.
9.
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
10.
YoungJu Choie Olav K. Richter 《Proceedings of the American Mathematical Society》2007,135(8):2309-2315
We determine a class of functions spanned by theta series of higher degree. We give two applications: A simple proof of the inversion formula of such theta series and a classification of skew-holomorphic Jacobi forms.