全文获取类型
收费全文 | 1009篇 |
免费 | 35篇 |
国内免费 | 1篇 |
专业分类
化学 | 709篇 |
晶体学 | 8篇 |
力学 | 36篇 |
数学 | 104篇 |
物理学 | 188篇 |
出版年
2023年 | 9篇 |
2022年 | 23篇 |
2021年 | 42篇 |
2020年 | 25篇 |
2019年 | 29篇 |
2018年 | 21篇 |
2017年 | 14篇 |
2016年 | 35篇 |
2015年 | 28篇 |
2014年 | 30篇 |
2013年 | 80篇 |
2012年 | 60篇 |
2011年 | 79篇 |
2010年 | 39篇 |
2009年 | 49篇 |
2008年 | 49篇 |
2007年 | 56篇 |
2006年 | 48篇 |
2005年 | 59篇 |
2004年 | 40篇 |
2003年 | 38篇 |
2002年 | 31篇 |
2001年 | 10篇 |
2000年 | 8篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 7篇 |
1996年 | 10篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1987年 | 5篇 |
1986年 | 9篇 |
1985年 | 5篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 9篇 |
1981年 | 9篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1975年 | 2篇 |
1973年 | 5篇 |
1937年 | 2篇 |
1931年 | 2篇 |
1930年 | 2篇 |
排序方式: 共有1045条查询结果,搜索用时 46 毫秒
91.
Platov Yu. T. Metlenkin D. A. Platova R. A. Rassulov V. A. Vereshchagin A. I. Marin V. A. 《Journal of Applied Spectroscopy》2021,88(4):723-730
Journal of Applied Spectroscopy - The application of UV-VIS-NIR spectroscopy combined with multivariate analysis for the classification and identification of buckwheat groats was analyzed. Samples... 相似文献
92.
Antibacterial effects of the essential oils of commonly consumed medicinal herbs using an in vitro model 总被引:1,自引:0,他引:1
Soković M Glamočlija J Marin PD Brkić D van Griensven LJ 《Molecules (Basel, Switzerland)》2010,15(11):7532-7546
The chemical composition and antibacterial activity of essential oils from 10 commonly consumed herbs: Citrus aurantium, C. limon, Lavandula angustifolia, Matricaria chamomilla, Mentha piperita, M. spicata, Ocimum basilicum, Origanum vulgare, Thymus vulgaris and Salvia officinalis have been determined. The antibacterial activity of these oils and their main components; i.e. camphor, carvacrol, 1,8-cineole, linalool, linalyl acetate, limonene, menthol, a-pinene, b-pinene, and thymol were assayed against the human pathogenic bacteria Bacillus subtilis, Enterobacter cloacae, Escherichia coli O157:H7, Micrococcus flavus, Proteus mirabilis, Pseudomonas aeruginosa, Salmonella enteritidis, S. epidermidis, S. typhimurium, and Staphylococcus aureus. The highest and broadest activity was shown by O. vulgare oil. Carvacrol had the highest antibacterial activity among the tested components. 相似文献
93.
94.
Jung A. Jung Young Baek Kim Young A. Kim Seung Bum Ryu Veronica Kim 《Journal of nanoparticle research》2011,13(6):2361-2374
Functional spherical solid and hollow particles of polysilsesquioxanes (PSQs) containing amine, thiol, and vinyl groups were
prepared by polymerizing organotrialkoxysilanes (OTASs) containing corresponding chemical groups. Fluorescent PSQ particles
were prepared by physically entrapping Rhodamine 6G, Coumarin 7, and Fluoresceine sodium salts. The intensity of fluorescent
light increased initially with increasing amount of entrapped fluorophores and then leveled off or decreased slightly after
reaching a maximum value. PSQ particles containing gold nanoparticles (GNPs), both inside and on the surface, were prepared
by the in situ reduction of gold ions by the PSQ particles. When the reduction reaction was carried out for extended periods
of time, the GNP that had formed inside the poly(3-mercaptopropyl)silsesquioxane (PMPSQ) and polyvinylsilsesequioxane (PVSQ)
particles underwent interesting morphological changes. PSQ particles containing amine and thiol groups fixed the GNPs on the
surface, which could be utilized further in binding amine-modified oligo-DNA strands. The aggregation of PSQ/GNP particles
combined with complementary oligo-DNA strands was examined to demonstrate that these particles could be applied to DNA assays
and isolation. The particles were characterized by scanning electron microscopy, transmission electron microscopy, solid state
nuclear magnetic resonance spectroscopy, ultraviolet/visible spectroscopy, and fluorescence microscopy. 相似文献
95.
Cyclic voltammetry, galvanostatic charge?Cdischarge technique, potentiostatic intermittent titration technique (PITT), and electrochemical impedance spectroscopy (EIS) were used to study the behavior of a LiMn1.95Cr0.05O4 (substituted lithium?Cmanganese spinel) electrode in nonaqueous electrolytes at 25 °C. Quantitative and qualitative changes of the electrode transport parameters as functions of lithium concentration were analyzed. Several equivalent circuits are discussed; the results obtained by different methods are compared. The PITT and EIS results are in good agreement; the chemical diffusion coefficient D varies within 10?14?C10?9 cm2 s?1 depending on the lithium content in the LixMn1.95Cr0.05O4 electrode. 相似文献
96.
D. ?krabelj M. Gorjan I. Dreven?ek-Olenik M. Marin?ek 《Applied physics. B, Lasers and optics》2011,105(4):793-800
We present a comprehensive numerical model that accounts for non-uniform pumping and a related thermal and electronic lensing effects in Q-switched unstable laser cavities. We study the influence of these effects on the output beam profile in Nd:YAG and ruby laser systems with side-pumped crystal rods. We also constructed both lasers to experimentally validate the numerical results and found very good agreement. The results show that both types of lensing effects are particularly detrimental in ruby, while they are insignificant in Nd:YAG. 相似文献
97.
We report on the operation and performance of a gain-switched Er:ZBLAN fiber laser based on an active pulsed diode pump system. The produced laser pulses offer high peak powers while retaining the high average powers and efficiency of the cw regime. The measured pulse duration was about 300 ns and nearly independent of the pump repetition frequency. The maximum obtained 68 W of peak power is the highest reported, to our knowledge, for diode-pumped Er:ZBLAN fiber lasers, and the 2 W of average power at the repetition frequency of 100 kHz is 2 orders of magnitude higher than previously reported average power in a pulsed regime. The obtained slope efficiency was 34%. 相似文献
98.
The difficulties in synthesizing phase pure BaTiO3 doped-(Na0.5Bi0.5)TiO3 are known. In this work, we reporting the optimized pulsed laser deposition (PLD) conditions for obtaining pure phase 0.92(Na0.5Bi0.5)TiO3-0.08BaTiO3, (BNT-BT0.08), thin films. Dielectric, ferroelectric and piezoelectric properties of BNT-BT0.08, thin films deposited by PLD on Pt/TiO2/SiO2/Si substrates are investigated in this paper. Perovskite structure of BNT-BT0.08 thin films with random orientation of nanocrystallites has been obtained by deposition at 600 °C. The relative dielectric constant and loss tangent at 100 kHz, of BNT-BT0.08 thin film with 530 nm thickness, were 820 and 0.13, respectively. Ferroelectric hysteresis measurements indicated a remnant polarization value of 22 μC/cm2 and a coercive field of 120 kV/cm. The piezoresponse force microscopy (PFM) data showed that most of the grains seem to be constituted of single ferroelectric domain. The as-deposited BNT-BT0.08 thin film is ferroelectric at the nanoscale level and piezoelectric. 相似文献
99.
100.
Antonio Monari Jose Pitarch‐Ruiz Gian Luigi Bendazzoli Stefano Evangelisti Jose Sanchez‐Marin 《International journal of quantum chemistry》2010,110(4):874-884
The high‐spin electronic states for lithium, sodium, and potassium four‐atom clusters were studied. In particular, we performed coupled cluster geometry optimization of the quintet state in tetrahedral geometry. The quintet state of these systems is characterized by having all the valence electron unpaired, giving rise to the so‐called no‐pair bonding. Single‐point full configuration interaction computations on the equilibrium geometries for the various clusters are also presented. The analysis of the valence orbitals in a localized representation confirms the importance of the p atomic orbitals to explain this unusual type of bond. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 相似文献