全文获取类型
收费全文 | 934篇 |
免费 | 50篇 |
国内免费 | 3篇 |
专业分类
化学 | 702篇 |
晶体学 | 5篇 |
力学 | 7篇 |
数学 | 133篇 |
物理学 | 140篇 |
出版年
2023年 | 9篇 |
2022年 | 11篇 |
2021年 | 14篇 |
2020年 | 20篇 |
2019年 | 21篇 |
2018年 | 7篇 |
2017年 | 14篇 |
2016年 | 33篇 |
2015年 | 42篇 |
2014年 | 35篇 |
2013年 | 51篇 |
2012年 | 76篇 |
2011年 | 66篇 |
2010年 | 41篇 |
2009年 | 31篇 |
2008年 | 64篇 |
2007年 | 77篇 |
2006年 | 40篇 |
2005年 | 43篇 |
2004年 | 36篇 |
2003年 | 34篇 |
2002年 | 45篇 |
2001年 | 23篇 |
2000年 | 8篇 |
1999年 | 9篇 |
1998年 | 12篇 |
1997年 | 13篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1988年 | 5篇 |
1984年 | 4篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1971年 | 5篇 |
1932年 | 2篇 |
1931年 | 2篇 |
1927年 | 2篇 |
1897年 | 2篇 |
排序方式: 共有987条查询结果,搜索用时 62 毫秒
101.
Dembski S Milde M Dyrba M Schweizer S Gellermann C Klockenbring T 《Langmuir : the ACS journal of surfaces and colloids》2011,27(23):14025-14032
A novel method for the synthesis of luminescent SiO(2)/calcium phosphate (CaP):Eu(3+) core-shell nanoparticles (NPs) was developed via a sol-gel route followed by annealing at a temperature of 800 °C. The object of this study was the investigation of the effect of pH on the formation of a CaP shell around the silica core. The resulting annealed NPs exhibited an amorphous SiO(2) core and a crystalline luminescent shell. The formation of a CaP layer was possible at pH below 4.5 and above 6.5 during the coating step. The crystal structure of the shell was studied by X-ray diffraction analysis. Hydroxyapatite (HAp) and α-tricalcium phosphate were detected as crystal phases of the surrounding layer. However, NPs produced under basic conditions exhibited a higher crystallinity of the CaP layer than did samples coated at pH below 4.5. In the pH interval between 4.5 and 6.5, no shell growth but the formation of secondary NPs containing CaO and Ca(OH)(2) was observed. Furthermore, SiO(2)/CP:Eu(3+) core-shell NPs were investigated by transmission electron microscopy, dynamic light scattering, Fourier transform infrared spectroscopy, inductively coupled plasma optical emission spectrometry, and photoluminescence spectroscopy. The resulting HAp-coated NPs were successfully tested by a cell-culture-based viability assay with respect to a later application as a luminescent marker for biomedical applications. 相似文献
102.
Campione M Parravicini M Moret M Papagni A Schröter B Fritz T 《Langmuir : the ACS journal of surfaces and colloids》2011,27(19):12008-12015
The integration of nanoscale processes and devices demands fabrication routes involving rapid, cost-effective steps, preferably carried out under ambient conditions. The realization of the metal/organic semiconductor interface is one of the most demanding steps of device fabrication, since it requires mechanical and/or thermal treatments which increment costs and are often harmful in respect to the active layer. Here, we provide a microscopic analysis of a room temperature, electroless process aimed at the deposition of a nanostructured metallic silver layer with controlled coverage atop the surface of single crystals and thin films of organic semiconductors. This process relies on the reaction of aqueous AgF solutions with the nonwettable crystalline surface of donor-type organic semiconductors. It is observed that the formation of a uniform layer of silver nanoparticles can be accomplished within 20 min contact time. The electrical characterization of two-terminal devices performed before and after the aforementioned treatment shows that the metal deposition process is associated with a redox reaction causing the p-doping of the semiconductor. 相似文献
103.
104.
105.
Andreasson-Ochsner M Romano G Håkanson M Smith ML Leckband DE Textor M Reimhult E 《Lab on a chip》2011,11(17):2876-2883
Lateral mobility and dimensionality have both been shown to influence cellular behavior, but have yet to be combined and applied in a single in vitro platform to address, e.g., cell adhesion in a setting mimicking the three-dimensional environment of neighboring cells in a reductionist way. To study the effect of the lateral mobility of cell adhesive ligands in three dimensions we present and characterize a platform, which enables patterning of single cells into microwells presenting a cell membrane mimetic interface pre-patterned to its walls. Soluble E-cadherin extracellular domains coupled through an optimized streptavidin-antibody linkage to lipids in a supported lipid bilayer (SPB) were presented on the microwell walls as either laterally mobile or immobile ligands. The fluidity was controlled through a small change in temperature by choosing phospholipids for the SPB with a lipid phase transition temperature around 30 °C. The platform thus enabled the investigation of cell adhesion to either laterally immobile or mobile E-cadherin ligands presented on the same cell membrane mimetic surface. Chinese hamster ovary (CHO) cells engineered to express E-cadherin that were cultured on the platform demonstrated that enhanced cadherin lateral mobility significantly decreased the formation of actin bundles and resulted in more diffuse actin organization, while constraining the cell shape to that of the microwell. This example highlights the potential to use in vitro cell culture platforms to mimic direct cell-cell interaction in a controlled environment that nevertheless captures the dynamic nature of the native cell environment. 相似文献
106.
The classical Strong Szegö-Widom Limit Theorem describes the asymptotic behavior of the determinants of the finite sections PnT(a)Pn of Toeplitz operators, i.e., of operators which have constant entries along each diagonal. We generalize these results to operators which have almost periodic sequences as their diagonals. 相似文献
107.
Steffen Oroszi Torsten Jakob Christian Wilhelm Hauke Harms Thomas Maskow 《Journal of Thermal Analysis and Calorimetry》2011,104(1):223-231
Isothermal microcalorimetry can be used to investigate the photosynthetic energy conversion of autotrophic organisms. In this
study, for the first time a diatom alga was used to compare the calorimetrically measured heat flux with measurements of the
photosynthetic performance by oxygen evolution and pulse-amplitude modulated fluorescence. The presented experimental setup
proved suitable to compare calorimetric data with those of conventional methods of the determination of photosynthesis rates.
Special attention was paid to the contribution of energy dissipation via non-photochemical quenching (NPQ) of chlorophyll
fluorescence to the metabolic energy balance. This was achieved by a combination of different light conditions and the use
of an inhibitor of NPQ. Although NPQ is an important photoprotective mechanism in diatoms, the inhibition of NPQ resulted
in an activation of alternative, energy dissipating pathways for absorbed radiation which completely compensated for the fraction
of energy dissipation by NPQ. 相似文献
108.
109.
Goran Radojev Torsten Linß 《Numerical Methods for Partial Differential Equations》2019,35(6):2305-2317
Collocation with triquadratic C1‐splines for a singularly perturbed reaction–diffusion problem in three dimension is studied. A posteriori error bound in the maximum norm is derived for the collocation method on arbitrary tensor‐product meshes which is robust in the perturbation parameter. Numerical results are presented that support our theoretical estimate. 相似文献
110.
Banbara Mutsunori Inoue Katsumi Kaufmann Benjamin Okimoto Tenda Schaub Torsten Soh Takehide Tamura Naoyuki Wanko Philipp 《Annals of Operations Research》2019,275(1):3-37
Annals of Operations Research - Answer Set Programming (ASP) is an approach to declarative problem solving, combining a rich yet simple modeling language with high performance solving capacities.... 相似文献