全文获取类型
收费全文 | 309篇 |
免费 | 9篇 |
国内免费 | 1篇 |
专业分类
化学 | 280篇 |
晶体学 | 4篇 |
数学 | 11篇 |
物理学 | 24篇 |
出版年
2021年 | 3篇 |
2020年 | 3篇 |
2016年 | 5篇 |
2015年 | 6篇 |
2014年 | 4篇 |
2013年 | 10篇 |
2012年 | 11篇 |
2011年 | 22篇 |
2010年 | 10篇 |
2009年 | 31篇 |
2008年 | 14篇 |
2007年 | 19篇 |
2006年 | 24篇 |
2005年 | 17篇 |
2004年 | 16篇 |
2003年 | 21篇 |
2002年 | 9篇 |
2001年 | 7篇 |
2000年 | 10篇 |
1999年 | 3篇 |
1997年 | 3篇 |
1996年 | 8篇 |
1995年 | 3篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 8篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1972年 | 2篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1967年 | 1篇 |
1935年 | 2篇 |
1934年 | 1篇 |
1928年 | 1篇 |
1914年 | 1篇 |
1913年 | 1篇 |
1909年 | 1篇 |
1899年 | 1篇 |
排序方式: 共有319条查询结果,搜索用时 15 毫秒
31.
Krishnamohan Sharma CV Chusuei CC Clérac R Möller T Dunbar KR Clearfield A 《Inorganic chemistry》2003,42(25):8300-8308
Phosphoric acid forms two distinct coordination compounds with manganese salts in aqueous media, a two-dimensional layered structure, [Mn(HPO4).(H2O)3], 1, under ambient conditions, and a three-dimensional synthetic mineral, [Mn5(mu-OH2)2(HPO4)2(PO4)2(H2O)2], 2, under hydrothermal procedures, at 120 degrees C. In compound 1, the oxygen atom of the doubly deprotonated phosphoric acid interconnects the metal centers to form a layered structure. The neutral hydrophilic layers of 1 are separated by 5.5 A and may potentially intercalate hydrophilic organic guest molecules. The metal centers in 2 are octahedral and bridged by PO4(3-), HPO4(2-), and OH2 groups to form a complex three-dimensional network. XPS analysis on 1 and 2 confirms that manganese exists in the +2 oxidation state. Compound 2 is a poor ion exchanger, but some improvement is observed on partial dehydration. The magnetic properties of both 1 and 2 were studied in detail to examine the amplitude of the magnetic interactions through phosphate ligand bridges. While 1 reveals dominant antiferromagnetic interactions between the spin carriers, a complete investigation of the magnetic properties of 2 revealed its true nature to be a glassy magnet. 相似文献
32.
33.
An alternative approach to synthesize pedamide,a key building block of pederin was described.Iodine-induced asymmetric heterocyclization was used as the key step to construct the skeleton,a tetrahydropyran ring with three chiral centers.Brown's asymmetric allylation and Lewis acid-mediated allylation were investigated to introduce chains and chiral alcohols.Sharpless dihydroxylation decorated the side chain.And high optically pure target was obtained by removing the epimers formed in these reactions on c... 相似文献
34.
E. Cohen J. W. Commelin Pfeffer van 't Hoff Ladenburg Adie Tammann Raoult Naccari Ponsot H. N. Morse D. W. Horn J. C. W. Frazer B. S. Hopkins E. J. Hoffmann W. L. Kennon L. F. Lovelace W. W. Holland F. M. Rogers P. B. Dunbar B. Mears B. F. Lovelace Berkeley Hartley Barlow und L. Kahlenberg 《Fresenius' Journal of Analytical Chemistry》1909,48(4-5):273-278
Ohne Zusammenfassung 相似文献
35.
A convenient route for the synthesis of 3,4-dihydrocoumarin derivates from salicylaldehyde derivates and 1,3-dicarbonyl compounds under solvent-free microwave irradiation conditions was described. In this way, a range of compounds was obtained in moderate to good yields in a short reaction time. 相似文献
36.
The ASMS conference on ion spectroscopy brought together at Asilomar on October 16–20, 2009 a large group of mass spectrometrists
working in the area of ion spectroscopy. In this introduction to the field, we provide a brief history, its current state,
and where it is going. Ion spectroscopy of intermediate size molecules began with photoelectron spectroscopy in the 1960s,
while electronic spectroscopy of ions using the photodissociation “action spectroscopic” mode became active in the next decade.
These approaches remained for many years the main source of information about ionization energies, electronic states, and
electronic transitions of ions. In recent years, high-resolution laser techniques coupled with pulsed field ionization and
sample cooling in molecular beams have provided high precision ionization energies and vibrational frequencies of small to
intermediate sized molecules, including a number of radicals. More recently, optical parametric oscillator (OPO) IR lasers
and free electron lasers have been developed and employed to record the IR spectra of molecular ions in either molecular beams
or ion traps. These results, in combination with theoretical ab initio molecular orbital (MO) methods, are providing unprecedented
structural and energetic information about gas-phase ions. 相似文献
37.
Eric W. Reinheimer Hanhua Zhao Kim R. Dunbar 《Journal of chemical crystallography》2010,40(6):514-519
Abstract
The synthesis and crystal structure of the 1:1 complex o-Me2TTF-TCNB is reported. The complex crystallizes in the triclinic space group P-1 with a = 6.920(1) ?, b = 7.928(2) ?, c = 17.453(4) ?, α = 100.53(3)°, β = 99.66(3)°, and γ = 97.32(3)°. The bond length of the central C=C bond in o-Me2TTF is 1.342(2) ?, indicating a neutral state for the o-Me2TTF donor. 相似文献38.
Self-injection length in La0.7Ca0.3MnO3-YBa2Cu3O7-δ ferromagnet-superconductor multilayer thin films
We have carried out extensive studies on the self-injection problem in barrierless heterojunctions between La0.7Ca0.3MnO3 (LCMO) and YBa2Cu3O7-δ (YBCO) thin films. The heterojunctions were formed in situ by sequentially growing LCMO and YBCO films on 〈100〉 LaAlO3 (LAO) substrate using a pulsed laser deposition (PLD) system. YBCO micro-bridges with 64 μm width were patterned both on
the LAO (control) and LCMO side of the substrate. Critical current, I
c, was measured at 77 K on both the control side as well as the LCMO side for different YBCO film thickness. It was observed
that while the control side showed a J
c of ∼ 2 × 106 A/cm2, the LCMO side showed about half the value for the same thickness (1800 ?). The difference in J
c indicates that a certain thickness of YBCO has become ‘effectively’ normal due to self-injection. From the measurement of
J
c at two different thicknesses (1800 ? and 1500 ?) of YBCO films both on the LAO as well as the LCMO side, the value of self-injection
length (at 77 K) was estimated to be ∼ 900 ?. To the authors’ best knowledge, this is the first time that self-injection length
has been quantified. A control experiment carried out with LaNiO3 deposited by PLD on YBCO did not show any evidence of self-injection. 相似文献
39.
All string theories naively contain a massless dilaton which couples with the strength of gravity in direct violation of experiment. We present a simple mechanism for giving the dilaton a mass In unoriented open bosonic string theories.This essay received an honourable mention from the Gravity Research Foundation, 1990. — Ed. 相似文献
40.
Strong Direct Magnetic Coupling in a Dinuclear CoII Tetrazine Radical Single‐Molecule Magnet
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Toby J. Woods Dr. Maria Fernanda Ballesteros‐Rivas Sergei M. Ostrovsky Andrew V. Palii Oleg S. Reu Sophia I. Klokishner Dr. Kim R. Dunbar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(29):10302-10305
The ligand‐centered radical complex [(CoTPMA)2‐μ‐bmtz.?](O3SCF3)3 ? CH3CN (bmtz=3,6‐bis(2′‐pyrimidyl)‐1,2,4,5‐tetrazine, TPMA=tris‐(2‐pyridylmethyl)amine) has been synthesized from the neutral bmtz precursor. Single‐crystal X‐ray diffraction studies have confirmed the presence of the ligand‐centered radical. The CoII complex exhibits slow paramagnetic relaxation in an applied DC field with a barrier to spin reversal of 39 K. This behavior is a result of strong antiferromagnetic metal–radical coupling combined with positive axial and strong rhombic anisotropic contributions from the CoII ions. 相似文献