全文获取类型
收费全文 | 243篇 |
免费 | 18篇 |
专业分类
化学 | 150篇 |
力学 | 5篇 |
数学 | 80篇 |
物理学 | 26篇 |
出版年
2023年 | 4篇 |
2022年 | 9篇 |
2021年 | 15篇 |
2020年 | 13篇 |
2019年 | 11篇 |
2018年 | 12篇 |
2017年 | 9篇 |
2016年 | 19篇 |
2015年 | 14篇 |
2014年 | 14篇 |
2013年 | 17篇 |
2012年 | 17篇 |
2011年 | 29篇 |
2010年 | 14篇 |
2009年 | 3篇 |
2008年 | 10篇 |
2007年 | 6篇 |
2006年 | 8篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2003年 | 5篇 |
2002年 | 1篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1988年 | 1篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1975年 | 1篇 |
1971年 | 3篇 |
1969年 | 1篇 |
排序方式: 共有261条查询结果,搜索用时 609 毫秒
121.
Matthieu Réfrégiers Frank Wien Ha‐Phuong Ta Lavanya Premvardhan Stéphane Bac Frederic Jamme Valerie Rouam Bruno Lagarde François Polack Jean‐Luc Giorgetta Jean‐Paul Ricaud Michel Bordessoule Alexandre Giuliani 《Journal of synchrotron radiation》2012,19(5):831-835
The new synchrotron‐radiation circular‐dichroism (SRCD) endstation on the UV‐visible synchrotron beamline DISCO has been commissioned at the SOLEIL synchrotron. The design has been focused on preservation of a high degree of linear polarization at high flux and moderate resolving power covering the vacuum ultraviolet to visible spectral range (125–600 nm). The beam dimensions have been set to 4 mm × 4 mm at 1 nm bandwidth for lower sample degradation. The nitrogen‐purged sample chamber fits three types of sample holders accommodating conventional round cell mounting, automated rotation of the samples, as well as a microfluidic set‐up. Automated temperature‐controlled data collection on microvolumes is now available to the biology and chemistry communities. Macromolecules including membrane proteins, soluble proteins, bio‐nanotubes, sugars, DNA and RNAs are now routinely investigated. 相似文献
122.
A method is presented to improve the speed of convergence of Wang-Landau simulations as used to calculate the density of states of continuous systems. The density of states is first crudely estimated with calculations employing a smoothed potential-energy surface. This estimate is then used as a seed for subsequent Wang-Landau simulations using the original potential. The performance of the method is demonstrated by employing several simple models, including an analytically solvable harmonic system as well as a Go model of a protein. For all systems considered, the seeded simulations were found to converge significantly faster and with higher accuracy than the standard Wang-Landau simulations. 相似文献
123.
Plamen Kirilov Hubert Matondo Patricia Vicendo Jean‐Christophe Garrigues Michel Baboulne Hoang‐Phuong Nguyen Isabelle Rico‐Lattes 《应用有机金属化学》2006,20(2):125-129
The synthesis of a number of new 2,2′‐bipyridine ligands functionalized with bulky amino side groups is reported. Three homoleptic polypyridyl ruthenium (II) complexes, [Ru(L)3]2+ 2(PF6?), where L is 4,4′‐dioctylaminomethyl‐2,2′‐bipyridine (Ru4a), 4,4′‐didodecylaminomethyl‐2,2′‐bipyridine (Ru4b) and 4,4′‐dioctadodecylaminomethyl‐2,2′‐bipyridine (Ru4c), have been synthesized. These compounds were characterized and their photophysical properties examined. The electronic spectra of three complexes show pyridyl π → π* transitions in the UV region and metal‐to‐ligand charge transfer bands in the visible region. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
124.
Phuong Hoang Tran Poul Erik Hansen Thuy Thanh Pham Vy Thanh Huynh Vy Hieu Huynh Thao Du Thi Tran 《合成通讯》2014,44(20):2921-2929
The catalytic activity of metal triflates was investigated in Friedel–Crafts benzoylation under microwave irradiation. Friedel–Crafts benzoylation with benzoyl chloride of a variety of arenes containing electron-rich and electron-poor rings using bismuth triflate under microwave irradiation is described. This method allows the preparation of aryl ketones under solventless conditions in good to excellent yields and short reaction time. Bismuth triflate was easily recovered and reused five times without significant loss of the catalytic activity. 相似文献
125.
Phuong Mai Le Margaret McCooeye Anthony Windust 《Analytical and bioanalytical chemistry》2014,406(6):1739-1749
Here, we describe a new application of ultra-performance liquid chromatography coupled with an electrospray ionization quadrupole time-of-flight mass spectrometry operating in MSE mode (UPLC-QTOF-MSE) for the sensitive, fast, and effective characterization of alkaloids in goldenseal (Hydrastis canadensis). This approach allowed identification of alkaloids using a cyclic low and high collision energy spectral acquisition mode providing simultaneous accurate precursor and fragment ion mass information. A total of 45 compounds were separated and 40 of them characterized including one new compound and 7 identified for the first time in goldenseal. The spectral data obtained using this method is comparable to those obtained by conventional LC-MSn. However, the UPLC-QTOF-MSE method offers high chromatographic resolution with structural characterization facilitated by accurate mass measurement in both MS and MS/MS modes in a single analytical run; this makes it suitable for the rapid analysis and screening of alkaloids in plant extracts. Figure
Identification of alkaloids in goldenseal by UPLC-QTOF-MS in MSE mode 相似文献
126.
Existence of asymptotically stable solutions for a mixed functional nonlinear integral equation in N variables
下载免费PDF全文
![点击此处可从《Mathematische Nachrichten》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Motivated by recent known results about the solvability of nonlinear functional integral equations in one, two or N variables, this paper proves the existence of asymptotically stable solutions for a mixed functional integral equation in N variables with values in a general Banach space via a fixed point theorem of Krasnosels'ki? type. In order to illustrate the results obtained here, an example is given. 相似文献
127.
Nguyen?BuongEmail author Nguyen?Thi?Hong?Phuong Nguyen?Thi?Thu?Thuy 《Russian Mathematics (Iz VUZ)》2015,59(10):16-22
In this paper, in order to solve a variational inequality problem over the set of common fixed points of an infinite family of nonexpansive mappings on real reflexive and strictly convex Banach spaces with a uniformlyGâteaux differentiable norm, we introduce two new explicit iteration methods. 相似文献
128.
Phuong Mai Le Margaret McCooeye Anthony Windust 《Analytical and bioanalytical chemistry》2013,405(13):4487-4498
Liquid chromatography coupled to multistage mass spectrometry (LC-MSn) is being used increasingly in pharmaceutical research and for quality control in herbal medicines because of its superior sensitivity and selectivity. In this study, a rapid, high-resolution liquid chromatography-mass spectrometry (LC-MSn) method was developed to separate and identify alkaloids in the root extract of goldenseal, which is one of the 20 most popular herbal supplements used worldwide. In total, 28 alkaloids were separated and characterized including one novel compound and 21 identified, or tentatively identified, for the first time in goldenseal. The current high-resolution LC-MSn method provides a rapid and definitive means of profiling the composition of goldenseal root and will provide a useful tool in understanding the bioactivity of this medicinal plant. Figure
Extraction and Orbitrap LC-MSn analysis of Goldenseal root for alkaloid identification 相似文献
129.
Uyen Tu Thi Doan Duy Khanh Le Truong Lam Huynh Tung Thanh Ngo Trieu Quang Vo Dr. Minh Thu Tran Thi Anh Tuan Thanh Pham Vinh Cao Tran Phuong Tuyet Nguyen Ngoc Kim Pham 《Chemphyschem》2023,24(18):e202300210
In this study, the features of resistive random access memory (RRAM) employing a straightforward Cr/MAPbI3/FTO three-layer structure have been examined and clarified. The device displays various resistance switching (RS) behavior at various sweep voltages between 0.5 and 5 V. The RS effect has a conversion in the direction of the SET and RESET processes during sweeping for a number of cycles at a specific voltage. The directional change of the RS processes corresponds to the dominant transition between the generation/recombination of iodide ion and vacancy in the MAPbI3 perovskite layer and the electrochemical metallization of the Cr electrode under the influence of an electric field, which results in the conductive filament (CF) formation/rupture. At each stage, these processes are controlled by specific charge conduction mechanisms, including Ohmic conduction, space-charge-limited conduction (SCLC), and variable-range hopping (VRH). By identifying the biased voltage and the quantity of voltage sweep cycles, one can take a new approach to control or modulate the pathways for effective charge transport. This new approach is made possible by an understanding of the RS characteristics and the corresponding mechanisms causing the variation of RS behavior in the structure. 相似文献
130.
Fang Y Nguyen P Ivasenko O Aviles MP Kebede E Askari MS Ottenwaelder X Ziener U Siri O Cuccia LA 《Chemical communications (Cambridge, England)》2011,47(40):11255-11257
Charge-assisted hydrogen bond-directed self-assembly of a zwitterionic quinonemonoimine was investigated at the liquid/solid interface using scanning tunnelling microscopy. Factors governing morphology, chirality and multilayer formation are discussed, presenting an important foundation for understanding the properties of a large family of related molecules with interesting potential in supramolecular design. 相似文献