全文获取类型
收费全文 | 493篇 |
免费 | 4篇 |
国内免费 | 4篇 |
专业分类
化学 | 181篇 |
晶体学 | 4篇 |
力学 | 18篇 |
数学 | 203篇 |
物理学 | 95篇 |
出版年
2020年 | 5篇 |
2019年 | 8篇 |
2018年 | 1篇 |
2017年 | 8篇 |
2016年 | 8篇 |
2015年 | 11篇 |
2014年 | 23篇 |
2013年 | 38篇 |
2012年 | 31篇 |
2011年 | 45篇 |
2010年 | 31篇 |
2009年 | 39篇 |
2008年 | 40篇 |
2007年 | 30篇 |
2006年 | 36篇 |
2005年 | 22篇 |
2004年 | 19篇 |
2003年 | 26篇 |
2002年 | 16篇 |
2001年 | 18篇 |
2000年 | 5篇 |
1999年 | 9篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1994年 | 9篇 |
1993年 | 1篇 |
排序方式: 共有501条查询结果,搜索用时 31 毫秒
1.
2.
3.
The commonly used ultrasonic horn generates localized cavitation below its converging tip resulting in a dense bubble cloud near the tip and limiting diffusion of reactive components into the bubble cloud or reactive radicals out of the bubble cloud. To improve contact between reactive components, a novel ultrasonic horn design was developed based on the principles of the dynamic wave equation. The horn, driven at 20 kHz, has a multi-stepped design with a cone-shaped tip increasing the energy-emitting surface areas and creating multiple reactive zones. Through different physical and chemical experiments, performance of the horn was compared to a typical horn driven at 20 kHz. Hydrophone measurements showed high acoustic pressure areas around the horn neck and tip. Sonochemiluminescence experiments verified multiple cavitation zones consistent with hydrophone readings. Calorimetry and dosimetry results demonstrated a higher energy efficiency (31.3%) and a larger hydroxyl radical formation rate constant (0.36 μM min−1) compared to typical horns. In addition, the new horn degraded naphthalene faster than the typical horn tested. The characterization results demonstrate that the multi-stepped horn configuration has the potential to improve the performance of ultrasound as an advanced oxidation technology by increasing the cavitation zone in the solution. 相似文献
4.
Glass is a promising substitute substrate material being evaluated for electronic packaging technology. Improving the electroless copper plated layer adhesion of the glass is one of the most important considerations for development of the technology. An excimer laser (248 nm) was used for structured texturing of glass surfaces (to improve adhesion) by changing mask dimensions, laser operating parameters and overlapping pitch spacing, and therefore producing a range of micro-scale features. Electroless plated copper adhesion strength was assessed using quantitative scratch testing, demonstrating that micro-patterned structures can significantly improve copper/glass adhesion. New ISO 25178 Part 2 areal surface texture parameters were used to characterise the surface roughness of ablated glass surfaces, and correlated to the scratch testing results. Highly correlated parameters were identified that could be used as predictive surface design tools, directly linking surface topography to adhesion performance, without the need for destructive adhesion quantification via scratch testing. 相似文献
5.
In this paper,we consider a possible modification of the de Sitter and anti-de Sitter space for the extended uncertainty principle.For the modified anti-de Sitter model we discuss the representation and wave functions of the momentum operator for a one-dimensional box problem.Also,we consider modified Snyder and anti-Snyder models for the generalized uncertainty principle.Then,we assume the Hamiltonian with different potential and solve the Heisenberg algebra for the modified(anti)-de Sitter and(anti)-Snyder models in both position and in the momentum space. 相似文献
6.
7.
Chung Won Sang Hassanabadi Hassan 《International Journal of Theoretical Physics》2019,58(6):1791-1802
In this paper we show that the position representation of the higher order generalized uncertainty principle (HGUP) is also well defined without approximation. We find the simpler form of this representation with a help of the signature of the discriminant of the cubic equation. Using this we discuss the HGUP derivative, HGUP exponential and HGUP trigonometric functions and HGUP-corrected Bohr atom model. Finally we discuss the D-dimensional HGUP algebra and compute the cosmological constant.
相似文献8.
In this work, a projection algorithm is considered for treating strongly continuous semigroups of demicontinuous pseudocontractions. Theorems of strong convergence of fixed points are established in the framework of real Hilbert spaces. 相似文献
9.
Various indane and cyclobuta[a]indene derivatives were synthesized by palladium-catalyzed cyclization of homoallylic alcohol derivatives prepared from Baylis-Hillman adducts. Especially, cyclobuta[a]indene derivative was synthesized stereoselectively by palladium-catalyzed 5-exo-trig/4-exo-trig cascade cyclization, albeit in moderate yield. The Z isomer was formed exclusively in the presence of Et3N by usual Heck-type carbopalladation process while E isomer with Cs2CO3 most likely by a concerted metalation/deprotonation (CMD) process. 相似文献
10.
Won-Bo Shim Jeong-Eon Song Hyoyoung Mun Duck-Hwa Chung Min-Gon Kim 《Analytical and bioanalytical chemistry》2014,406(3):859-866
Detection of pathogenic bacteria that pose a great risk to human health requires a rapid, convenient, reliable, and sensitive detection method. In this study, we developed a selective filtration method using monoclonal antibody (MAb)–magnetic nanoparticle (MNP) nanocomposites for the rapid and sensitive colorimetric detection of Salmonella typhimurium. The method contains two key steps: the immunomagnetic separation of the bacteria using MAb–MNP nanocomposites and the filtration of the nanocomposite-bound bacteria. Color signals from the nanocomposites remaining on the membrane were measured, which reflected the amount of bacteria in test samples. Immunomagnetic capture efficiencies of 8 to 90 % for various concentrations of the pathogen (2?×?104–2?×?101 cells) were obtained. After optimization of the method, 2?×?101 cells of S. typhimurium in pure culture solution was detectable as well as in artificially inoculated vegetables (100 cells/g). The method was confirmed to be highly specific to S. typhimurium without cross-reaction to other pathogenic bacteria and could be concluded within 45 min, yielding results in a shorter or similar time period as compared with recently reported antibody immobilized on magnetic-particle-based methods. This study also demonstrated direct application of MAb–MNP nanocomposites without a dissociation step of bacteria from magnetic beads in colorimetric assays in practice. 相似文献