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排序方式: 共有158条查询结果,搜索用时 15 毫秒
41.
A.F.M.Y. Haider M. Wahadoszamen M.E. Sadat K.M. Abedin A.I. Talukder 《Optics & Laser Technology》2010,42(6):969-974
Laser-induced breakdown spectroscopic technique was used to study the elemental profile of beach sand samples of Bangladesh. Apart from Silicon, which is the main elemental constituent of sand, the presence of Li, Na, Mg, Al, Cl, K, Ca, Ti, Cr, Mn, Fe, Zr, Sr, Ba, Te and Zn was identified in the beach sand samples. In addition to the qualitative analyses, quantitative analyses of a particular element Titanium (Ti) has been done. The result shows the presence of (2.98±0.46)% of Ti by weight of the beach sand sample from Himchhori, Chittagong. It was determined by using six calibration curves drawn for six emission lines of TiI (489.991, 498.1732, 499.107, 499.951 , 503.591, 506.466 nm) by standard analyte addition method. The limit of detection (LoD) for this six calibration curves varied from 0.14 to 0.3% by weight. 相似文献
42.
This article reports on some theoretical studies concerning the impulsional mode of a cylindrical ion trap (CIT) supplied with a periodic impulsional radio frequency (rf) voltage of the form VaccosΩt/(1 ? kcos2Ωt) with 0 ≤ k < 1. The performance characteristics of CIT impulsional mode, for the twelve stability regions, were computed using fifth order Runge‐Kutta method and were compared to the classical sinusoidal mode k = 0. Also, the results show that, for the same equivalent operating point in two stability diagrams (having the same βz) the associated modulated secular ion frequencies behavior are the same. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
43.
Hojat Veisi Mehdi Adib Rahman Karimi‐Nami Zahra Yasaei Mahnaz Tajik Talieh Sadat Mosavat Saba Hemmati 《应用有机金属化学》2018,32(3)
An unprecedented environmentally friendly method has been developed for the synthesis of palladium nanoparticles supported on Glycyrrhiza glabra. The synthesized nanoparticles were utilized in Suzuki–Miyaura reaction between different aryl halides and aryl bronic acid in aqueous media. This heterogeneous catalyst can be reused and recycled repeatedly more than five times with only slight loss of its initial catalytic efficiency. This reaction carrid out under atmospheric pressure with high efficiency, unique and simple work‐up procedure and excellent yields. 相似文献
44.
45.
Synthesis,Spectroscopy, X‐ray Crystallography,and DFT Computations of Nanosized Phosphazenes 下载免费PDF全文
Zahra Shariatinia Elnaz Jalali Moghadam Narges Maghsoudi Hourieh Sadat Mirhosseini Mousavi Michal Dusek Vaclav Eigner 《无机化学与普通化学杂志》2015,641(5):967-978
Nanoparticles of nine phosphazenes with general formula 4‐CH3C6H4S(O)2N=PX3 [X = Cl ( A ), NC4H8 ( 1 ), NC6H12 ( 2 ), NC4H8N–C(O)OC2H5 ( 3 ), NC4H8N–C(O)OC6H5 ( 4 ), NC4H8O ( 5 ), NHCH2–C4H7O ( 6 ), N(CH3)(C6H11) ( 7 ), NHCH2–C6H5 ( 8 ), and 2‐NH‐NC5H4 ( 9 )] were synthesized using ultrasonic method and characterized by 1H, 13C, 31P NMR, FT‐IR, fluorescence, as well as UV/Vis spectroscopy and additionally with XRD, FE‐SEM, N2 sorption, and elemental analysis. The 31P NMR spectra of compounds 1 – 9 reveal the most up field shift δ(31P) for 9 at –11.45 ppm reflecting the most electron donation of 2‐aminopyridinyl rings through resonance to the phosphorus atom. The 1H, 13C NMR spectra of 7 exhibit two sets of signals for the hydrogen and carbon atoms of its two isomers present in the solution state in 1:4 ratio. The FE‐SEM micrographs illustrate that the nanoparticles of compounds 1 – 9 have spherical morphology and a size of 27–42 nm. From the XRD patterns, the crystal sizes were estimated to about 24–86 nm. The highest bandgap was measured for 3 (3.81 eV) whereas the smallest was measured for 8 (3.50 eV). The structures of two polymorphs of compound 5 ( 5 , 5′ ) were determined by X‐ray crystallography at 120 K. Both of these polymorphs are triclinic with P1 space group but 5 has a doubled unit cell volume and two symmetrically independent molecules ( 5a and 5b ). In structures 5a and 5′ , the phosphorus and all endocyclic atoms of two morpholinyl rings display disorder, whereas the molecule 5b does not show disorder. The strong intermolecular O–H ··· O hydrogen bonds plus weak intermolecular C–H ··· O and C–H ··· N interactions create three‐dimensional polymers in the crystalline networks of 5 and 5′ . The DFT computations illustrate that molecule 5b is more stable than 5a by –1.1062 and –0.9779 kcal · mol–1 at B3LYP and B3PW91 levels, respectively. The NBO calculations presented sp3d hybridization for phosphorus and sulfur atoms and sp2, sp3 hybrids for the nitrogen and oxygen atoms. 相似文献
46.
Surfactant‐assisted electromembrane extraction combined with capillary electrophoresis as a novel technique for the determination of acidic drugs in biological fluids 下载免费PDF全文
Ali Reza Fakhari Kobra Sadat Hasheminasab Zolfaghar Aladaghlo Mohammad Hosein Koruni 《Electrophoresis》2015,36(24):3034-3041
In this paper, for the first time, surfactant‐assisted electromembrane extraction coupled with capillary electrophoresis with UV detector was introduced for the extraction of acidic drugs from biological fluids. In this technique, in the presence of the nonionic surfactant in the donor phase, tendency of analyte ions into the supported liquid membrane (SLM) was increased. Naproxen and diclofenac were selected as model acidic drugs. In order to obtain the best extraction efficiency, several factors influencing the extraction efficiency were investigated. Optimal extractions were accomplished with 1‐octanol as the SLM, 15 Volt dc potential as the driving force, pH 12 in acceptor solution, and 0.2 mmol/L Triton X‐100 with pH 7.4 in donor solution. Equilibrium extraction conditions were obtained after 15 min of operation where the whole assembly agitated at 1000 rpm. Under the optimized conditions, preconcentration factors in the range of 176–184 and recoveries in the range of 88–92% were obtained. The applied method offers acceptable linearity with correlation coefficients higher than 0.9992. Limits of detection of 1.51 ng/mL and 2.42 ng/mL were obtained for naproxen and diclofenac, respectively. Finally, the developed method was successfully applied for the determination of naproxen and diclofenac in different matrices including plasma and urine samples. 相似文献
47.
Elahe Kazemi Ali Mohammad Haji Shabani Parisa Sadat Hashemi 《International journal of environmental analytical chemistry》2017,97(8):743-755
This study describes the successful sequential modification of multi-walled carbon nanotube (MWCNT) by Fe3O4 magnetic nanoparticles and 2-mercaptobenzothiazole (MBT) followed by its application as a novel sorbent for simultaneous magnetic solid phase microextraction of lead and cadmium. Fourier transform infrared spectroscopy and scanning electron microscopy were employed to confirm the chemical surface modification of the MWCNT. The ions retained on the 2-MBT/magnetic nanoparticles modified MWCNTs were eluted with 1.0 mL of nitric acid (0.8 mol L?1) in methanol solution and determined by the flame atomic absorption spectrometry. All parameters affecting the extraction condition were thoroughly investigated and optimised. Under the optimised condition preconcentration factor of 150.0, enhancement factors of 149.0 and 149.2 and limits of detection of 0.21 and 0.01 µg L?1 were achieved for lead and cadmium, respectively. Using the prepared magnetic nanocomposite, the possible interference of other common ions associated with lead and cadmium determination was effectively avoided and the method was successfully applied to the simultaneous determination of the target ions in various environmental water samples. 相似文献
48.
Majid Moghadam Shahram Tangestaninejad Valiollah Mirkhani Iraj Mohammadpoor‐Baltork Naghmeh Sadat Mirbagheri 《应用有机金属化学》2010,24(10):708-713
In the present work, highly efficient epoxidation of alkenes catalyzed by Mo(CO)6 supported on multi‐wall carbon nanotubes modified by 2‐aminopyrazine, APyz‐MWCNTs, is reported. The prepared catalyst was characterized by elemental analysis, scanning electron microscopy, FT IR and diffuses reflectance UV–vis spectroscopic methods. This new heterogenized catalysts, [Mo(CO)6@APyz‐MWCNT], was used as a highly efficient catalyst for epoxidation of alkenes with tert‐BuOOH. This robust catalyst was reused several times without loss of its catalytic activity. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
49.
Assia Siham Hadj Hamou Khaled Elmiloudi Said Djadoun 《Journal of Polymer Science.Polymer Physics》2009,47(21):2074-2082
In a first step of this contribution, the observed glass transition temperature‐composition behavior of miscible blends of poly(styrene‐co‐N,N‐dimethylacrylamide) (SAD17) containing 17 mol % of N,N‐dimethylacrylamide and poly(styrene‐co‐acrylic acid) (SAA18, SAA27, and SAA32) containing increasing acrylic acid content, are analyzed according to theoretical approaches. Both Kwei and Brostow equations describe well the experimental data though better fits were obtained with the Brostow's approach. The specific interactions involved in these systems are a combination of intra and interassociation hydrogen bonding. The positive deviation from the linear mixing rule of Tg‐composition observed within the SAA18+SAD17 blend system, indicates that interassociation interactions are prevailing. More pronounced intra‐association interactions within the SAA32+SAD17 blend system led to a large negative deviation while a fine balance is established between these two types of interactions within the SAA27+SAD17 blend. A thermodynamic analysis was carried out according to the Painter‐Coleman association model. The miscibility and phase behavior of SAD17+SAA18 and SAD17+SAA27 blends are well predicted. However, this model predicts a partial miscibility of SAD17+SAA32 system. Finally, the fitting parameter free method developed by Coleman to predict the Tg‐composition behavior is applied. This method predicts fairly well the evolution trend of experimental Tgs of the SAA18+SAD17 and SAA27+SAD17 blend systems. However, the compositional dependence of SAA32+SAD17 blend Tg was not predictable by this method. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47:2074–2082, 2009 相似文献
50.
The diffuse approximation is presented and applied to natural convection problems in porous media. A comparison with the control volume-based finite-element method shows that, overall, the diffuse approximation appears to be fairly attractive.Nomenclature
H
height of the cavities
-
I
functional
-
K
permeability
-
p(M
i
,M)
line vector of monomials
-
p
T
p-transpose
-
M
current point
- Nu
Nusselt number
- Ri
inner radius
- Ro
outer radius
- Ra
Rayleigh number
-
x, y
cartesian coordinates
-
u, v
velocity components
-
T
temperature
-
M
vector of estimated derivatives
-
t
thermal diffusivity
-
coefficient of thermal expansion
-
practical aperture of the weighting function
-
scalar field
-
(M, M
i
)
weighting function
-
streamfunction
-
kinematic viscosity 相似文献