全文获取类型
收费全文 | 845篇 |
免费 | 16篇 |
国内免费 | 2篇 |
专业分类
化学 | 518篇 |
晶体学 | 11篇 |
力学 | 17篇 |
数学 | 49篇 |
物理学 | 268篇 |
出版年
2024年 | 4篇 |
2023年 | 10篇 |
2022年 | 18篇 |
2021年 | 19篇 |
2020年 | 24篇 |
2019年 | 25篇 |
2018年 | 24篇 |
2017年 | 30篇 |
2016年 | 27篇 |
2015年 | 11篇 |
2014年 | 34篇 |
2013年 | 65篇 |
2012年 | 55篇 |
2011年 | 52篇 |
2010年 | 37篇 |
2009年 | 34篇 |
2008年 | 44篇 |
2007年 | 42篇 |
2006年 | 30篇 |
2005年 | 19篇 |
2004年 | 18篇 |
2003年 | 24篇 |
2002年 | 23篇 |
2001年 | 4篇 |
2000年 | 11篇 |
1999年 | 12篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1994年 | 9篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1987年 | 5篇 |
1985年 | 7篇 |
1983年 | 6篇 |
1982年 | 10篇 |
1981年 | 13篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1972年 | 3篇 |
1928年 | 6篇 |
1927年 | 6篇 |
1926年 | 3篇 |
1925年 | 3篇 |
1924年 | 3篇 |
1923年 | 3篇 |
排序方式: 共有863条查询结果,搜索用时 31 毫秒
1.
Molecular Diversity - The antifungals that are in current clinical practice have a high occurrence of a side effect and multidrug resistance (MDR). Researchers across the globe are trying to... 相似文献
2.
3.
The triple differential cross-section for K-shell ionization of silver and copper atoms by relativistic electrons have been
computed in the coplanar symmetric geometry with the inclusion of exchange effects following the multiple scattering theory
of Das and Seal [1] multiplied by suitable spinors. Present computed results are marginally improved in some cases from the
previous computed results [2]. Present results are compared with measured values [3] and with previous computation results
[2]. Some other theoretical computational results are also presented here for comparison.
相似文献
4.
The occurrence of charge on recoil56Mn produced by the (n,γ) reaction in polycrystalline potassium permanganate has been examined using the ‘charge plate technique’.
From considerations of capture gamma ray decay schemes and internal conversion it appears that, in a condensed medium, the
recoil atom develops charge after losing much of its initial kinetic energy which allows collection on charged electrodes.
Preliminary findings were presented at the International Symposium on Radiochemistry and Radiation Chemistry, RC-41 BARC,
Bombay, Feb. 4–6 (1991). 相似文献
5.
The present paper deals with the study of a Durrmeyer-type integral modification of certain modified Baskakov operators. Here
we study simultaneous approximation properties for these operators by using the iterative combinations. We obtain an asymptotic
formula and an error estimation in terms of higher order modulus of continuity for these operators.
相似文献
6.
A theoretical approach was made to find out a complete fluorine incorporation zone on a ternary diagram which serves as a useful graphical representation to select the flows of the supplied reagents for incorporation of the suitable amount of fluorine into cladding glass of optical fiber preform made by the MCVD process using CCl2F2 as a source of fluorine under oxygen abundance, oxygen deficiency and intermediate oxygen state conditions. The possible mechanism for incorporation of fluorine into cladding glass of optical fiber is also evaluated on the basis of the thermodynamical data. The fluorine incorporation mechanism in silica glass by the MCVD process is found to be dependent on the CCl2F2/SiCl4 ratio in the input gas mixture. Fluorine doping is found to be effective for removing the strained Si–O–Si bonds, which govern the optical transparency in deep ultra-violet (DUV) and vacuum ultra-violet (VUV) regions. The maximum refractive index depression of ?0.5 × 10?3 is obtained with incorporation of fluorine into silica cladding glass by the MCVD process using CCl2F2 as a dopant precursor with suitable flow of SiCl4 vapor along with O2 through backward deposition pass. The structure of fluorine doped silica glass preform samples containing 1.70–1.79 mol% fluorine incorporated by the MCVD process based on the analyses of 19F MAS spectra done by high-resolution 19F NMR spectroscopy reveal the presence of two distinct types of fluorine environments. The majority of the fluorine environments are formed in SiO1.5F polyhedral and less abundant species is observed to be highly unusual, yielding a fivefold coordinated silicon of the type SiO2F polyhedral which become increased with increasing the fluorine content. 相似文献
7.
8.
Boruah A Rao IN Nandy JP Kumar SK Kunwar AC Iqbal J 《The Journal of organic chemistry》2003,68(12):5006-5008
A cis-proline derived cyclic mimic of a type VI beta-turn is synthesized via a ring-closing metathesis reaction. The solution NMR conformational study indicates that the major conformer of the cyclic peptide adopts a type VIa beta-turn in CDCl(3) and a type VIb beta-turn in DMSO-d(6). 相似文献
9.
The temperature dependence of the electric quadrupole interaction frequency
l
o
, experienced by the181Ta probe occupying Hf site in the compounds Hf1-xTaxV2 has been measured for x=0.06, 0.10 and 0.20 in the temperature region between 8.5 K to 296 K. The measurements show lattice transformation in all the three compounds below 120 K. 相似文献
10.
Nandy JP Prabhakaran EN Kumar SK Kunwar AC Iqbal J 《The Journal of organic chemistry》2003,68(5):1679-1692
A novel chemo- and diastereoselective aerobic epoxidation of the N-cinnamoyl peptides catalyzed by polyaniline-supported cobalt(II) salen (PASCOS) is described. The N-cinnamoyl proline derived peptides 1 show a high pi-facial selectivity during these epoxidations. The origin of this diastereoselectivity in 1 has been attributed to (i) the propensity of the N-cinnamoyl proline amide to exist predominantly as trans rotamer in CDCl3, DMSO-d6, and CH3CN medium and (ii) existence of these peptides as organized structures (gamma- and beta-turns) due to the presence of intramolecular hydrogen bonds. An extensive solution NMR and MD simulation study on 1d and 1f indicates that the origin of the high pi-facial selectivity is due to the well-defined gamma- and beta-turns which result in the hindrance of one face of the cinnamoyl double bond in the transition state of the epoxidation reaction. 相似文献