全文获取类型
收费全文 | 669篇 |
免费 | 38篇 |
国内免费 | 3篇 |
专业分类
化学 | 421篇 |
晶体学 | 1篇 |
力学 | 39篇 |
数学 | 90篇 |
物理学 | 159篇 |
出版年
2024年 | 3篇 |
2023年 | 5篇 |
2022年 | 31篇 |
2021年 | 36篇 |
2020年 | 17篇 |
2019年 | 13篇 |
2018年 | 21篇 |
2017年 | 16篇 |
2016年 | 21篇 |
2015年 | 22篇 |
2014年 | 36篇 |
2013年 | 41篇 |
2012年 | 39篇 |
2011年 | 38篇 |
2010年 | 46篇 |
2009年 | 36篇 |
2008年 | 38篇 |
2007年 | 31篇 |
2006年 | 34篇 |
2005年 | 27篇 |
2004年 | 29篇 |
2003年 | 22篇 |
2002年 | 8篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 9篇 |
1998年 | 7篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1989年 | 2篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1967年 | 1篇 |
1962年 | 1篇 |
1955年 | 1篇 |
1927年 | 1篇 |
排序方式: 共有710条查询结果,搜索用时 31 毫秒
601.
Optimization of affinity capillary electrophoresis for routine investigations of protein–metal ion interactions 下载免费PDF全文
Hassan A. Alhazmi Sami El Deeb Markus Nachbar Sabine Redweik Hassan M. Albishri Deia Abd El‐Hady Hermann Wätzig 《Journal of separation science》2015,38(20):3629-3637
To facilitate the implementation of affinity capillary electrophoresis into routine binding screening studies of proteins with metal ions, method acceleration, transfer and precision improvement were investigated. Affinity capillary electrophoresis was accelerated by using shorter capillaries, employing lower sample concentrations and smaller injection volumes. Intra‐ and inter‐instrument method transfers were investigated considering the temperature setting of the capillary cooling system. For intra‐instrument method transfer, similar results were obtained when transferring a method from a long (62 cm) to a short (31 cm) capillary. The analysis time was reduced from 9 to 4 min. In case of inter‐instrument method transfer, interaction results showed small variation on the capillary electrophoresis instrument with inefficient capillary cooling system. Binding measurement precision was enhanced by slightly pushing the sample above the beginning of the capillary. Changing the buffer vials after each 30 runs and employing extra flushing after each 60 subsequent runs further enhanced the precision. The use of 0.1 molar ethylenediaminetetraacetic acid in the rinsing solution successfully desorbs the remaining metal ions from the capillary wall. Excellent precision for apparent mobility ratio measurements was achieved for different protein–metal ion interactions (relative standard deviation of 0.16–0.89%, 15 series, 12 runs for each). 相似文献
602.
Maria Theresia Pöschko Basile Vuichoud Jonas Milani Dr. Aurélien Bornet Dr. Matthias Bechmann Prof. Geoffrey Bodenhausen Dr. Sami Jannin Prof. Norbert Müller 《Chemphyschem》2015,16(18):3859-3864
We report proton spin noise spectra of a hyperpolarized solid sample of commonly used “DNP (dynamic nuclear polarization) juice” containing TEMPOL (4‐hydroxy‐2,2,6,6‐tetramethylpiperidine N‐oxide) and irradiated by a microwave field at a temperature of 1.2 K in a magnetic field of 6.7 T. The line shapes of the spin noise power spectra are sensitive to the variation of the microwave irradiation frequency and change from dip to bump, when the electron Larmor frequency is crossed, which is shown to be in good accordance with theory by simulations. Small but significant deviations from these predictions are observed, which can be related to spin noise and radiation damping phenomena that have been reported in thermally polarized systems. The non‐linear dependence of the spin noise integral on nuclear polarization provides a means to monitor hyperpolarization semi‐quantitatively without any perturbation of the spin system by radio frequency irradiation. 相似文献
603.
Durre Shahwar Naeem Ahmad Asma Yasmeen Muhammad Akmal Khan Sami Ullah Rahman Atta-ur 《Natural product research》2015,29(3):274-276
Whole plant extracts of Croton sparsiflorus in methanol have shown significant enzyme inhibition and antioxidant activities. Bioassay-guided isolation of chloroform fraction at pH 3 resulted in the identification of crotsparinine (1) and crotsparine (2), while sparsiflorine (3) was purified from the chloroform fraction at pH 9. The structures of the compounds were confirmed through spectral analyses (EI-MS, 1H and 13C NMR). The isolated compounds 1–3 exhibited remarkable enzyme inhibition activity with IC50 values 27.01 ± 1.1, 22.26 ± 1.0 and 18.02 ± 1.3 μM in xanthine oxidase and 48.42 ± 1.5, 48.05 ± 1.4 and 7.42 ± 1.0 μM in acetylcholine esterase assays, respectively. These compounds also showed potent radical scavenging and reducing properties in DPPH and FRAP assays, respectively. The present results suggest the validity of the traditional uses of C. sparsiflorus in rheumatism and gout. Furthermore, the isolated noraporphine alkaloids can be useful in the treatment of neurodegenerative diseases. 相似文献
604.
605.
606.
607.
Jaroslav Pól Tiina J. Kauppila Sami Franssila Tapio Kotiaho Risto Kostiainen 《Rapid communications in mass spectrometry : RCM》2010,24(17):2584-2590
An ionspray microchip is introduced. The chip is based on the earlier presented nebulizer microchip that consists of glass and silicon plates bonded together. A liquid inlet channel, nebulizer gas inlet, and nozzle are etched on the silicon plate and a platinum heater is integrated on the glass plate. The nebulizer microchip has been previously used in atmospheric pressure chemical ionization, atmospheric pressure photoionization, sonic spray ionization, and thermospray ionization modes. In this work we show that the microchip can be operated also in ionspray mode by introducing high voltage to the silicon plate of the microchip. The effects of operation parameters (voltage, nebulizer gas pressure, sample solution flow rate, solvent composition, and analyte concentration) on the performance of the ion spray microchip were studied. Under optimized conditions the microchip provides efficient ionization of small and large compounds and good quantitative performance. The feasibility of the ion spray microchip in liquid chromatography/mass spectrometry (LC/MS) was demonstrated by the analysis of tryptic peptides of bovine serum albumin. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
608.
In this paper, the complex Korteweg-de Vries equation with power law nonlinearity is studied in presence of perturbation terms. The exact 1-soliton solution is obtained. It will be seen that the time-dependent coefficients must be simply Riemann integrable for the solitons to exist. The solitary wave ansatz is used to carry out the integration. 相似文献
609.
Jari S. Kavakka Viktor Parviainen Kristiina Wähälä Ilkka Kilpeläinen Sami Heikkinen 《Magnetic resonance in chemistry : MRC》2010,48(10):777-781
NMR analysis of complex mixtures can be significantly simplified using polyethyleneglycol (PEG) as resolving additive in DOSY NMR technique, which allows the extraction of individual spectra of mixture components with differing polarity. Resolving power of PEG‐assisted DOSY was demonstrated with natural product mixtures. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
610.
Hazem Ali Amit B. Shirode Paul W. Sylvester Sami Nazzal 《Colloids and surfaces. A, Physicochemical and engineering aspects》2010,353(1):43-51
The primary objective of this study was to prepare nanostructured lipid carriers loaded with tocotrienol-rich-fraction of palm oil (TRF-NLCs) and to evaluate their antiproliferative effects against neoplastic +SA mammary epithelial cells. This necessitated optimizing the ultrasonic homogenization process parameters and the surfactant to lipid ratio within the NLCs. Therefore, sonication time and pulsar rate were initially evaluated for their effect on the size and polydispersity of the nanoparticles using a full factorial design. Also, varying the surfactant to lipid ratio from 0.25:1 to 3:1 was evaluated for its effect on the same responses. Optimal nanoparticles were obtained when dispersions containing a surfactant to lipid ratio of 0.5:1, with a total lipid concentration of 0.25 (w/v), were sonicated at 60% pulsar rate for 10 min. These parameters were subsequently used to prepare TRF-NLCs. TRF was loaded into the nanoparticles by substituting 10% (TRF-10-NLC) or 50% (TRF-50-NLC) of the lipid phase with TRF. In an extended stability study, no significant change in particle size of the TRF-NLCs was observed over 6 months of storage. In the cell culture studies, TRF-NLCs were shown to exhibit potent antiproliferative effect against neoplastic +SA mammary epithelial cells. The IC50 values of TRF-10-NLCs were 2-fold lower than the IC50 value of the reference TRF/BSA solution. In contrast, TRF-50-NLCs had comparable IC50 values as the TRF/BSA solution, which signified the importance of TRF encapsulation within NLCs on their activity. Furthermore, these findings suggested that TRF-NLCs may have potential value in the treatment of breast cancer. 相似文献