全文获取类型
收费全文 | 188篇 |
免费 | 5篇 |
专业分类
化学 | 153篇 |
晶体学 | 1篇 |
数学 | 13篇 |
物理学 | 26篇 |
出版年
2024年 | 2篇 |
2023年 | 4篇 |
2022年 | 7篇 |
2021年 | 4篇 |
2020年 | 5篇 |
2019年 | 3篇 |
2018年 | 10篇 |
2017年 | 4篇 |
2016年 | 10篇 |
2015年 | 5篇 |
2014年 | 12篇 |
2013年 | 21篇 |
2012年 | 18篇 |
2011年 | 22篇 |
2010年 | 12篇 |
2009年 | 3篇 |
2008年 | 8篇 |
2007年 | 3篇 |
2006年 | 4篇 |
2005年 | 1篇 |
2004年 | 4篇 |
2003年 | 2篇 |
2002年 | 1篇 |
2001年 | 1篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1979年 | 1篇 |
1978年 | 4篇 |
排序方式: 共有193条查询结果,搜索用时 46 毫秒
131.
In the present investigation, we obtain some subordination and superordination results involving Hadamard products for certain normalized analytic functions in the open unit disk. Relevant connections of the results, which are presented in this paper, with various other known results are also pointed out. 相似文献
132.
The response of a two-electron quantum ring system to the short laser pulses of different shapes in the presence of external static electric field is studied.The variation of transition probabilities of the two-electron quantum ring from ground state to excited states with a number of parameters is shown and explained.The energy levels and wavefunctions of the system in the presence of static electric field are found by solving the time-independent Schrodinger equation numerically by the finite difference method.The shape of the pulse plays a dominant role on the dynamics. 相似文献
133.
134.
Anita Raj Sanwaria Nikita Sharma Archana Chaudhary Meena Nagar 《Journal of Sol-Gel Science and Technology》2013,68(2):245-253
Non-aqueous reactions of aluminum isopropoxide with 8-hydroxyquinoline (Hq = HONH6C9) in 1:1, 1:2 and 1:3 molar ratios in anhydrous benzene yield complexes of the type [qnAl(OPri)3?n] {where n = 1 (1), n = 2 (2), n = 3 (3)}. Progress of the reactions were monitored by estimating liberated 2-propanol in benzene-2-propanol azeotrope by oxidimetric method. All the products were fluorescent green powders, sparingly soluble in CHCl3. They were characterized by elemental analysis, FT-IR and (1H, 13C and 27Al) NMR studies. The ESI mass spectral studies indicate dimeric nature for (1) and (2) and monomeric nature for the compound (3). The XRD spectra of (1–3) showed crystalline nature with the average particle size of 45, 32 and 27 nm respectively, as evaluated from Debye–Scherrer equation. The XRD spectrum of (3) also suggests the formation of β-crystalline polymorphs of Alq3. The SEM images appear to indicate granular morphology for (1) and formation of cylindrical shaped rods for (2) and (3). Sol–gel hydrolysis of (1), (2) or (3) in presence of a strong acid as well as of the precursor, Al(OPri)3,without acid or base catalyst, followed by sintering at 950 °C yielded tetragonal primitive phase of nano-sized δ-alumina in all the cases, as reflected by their powder X-ray diffraction pattern. The IR, SEM and EDX studies also support the formation of transition alumina. 相似文献
135.
Vijaya Kabra Sonia Sharma Neelima Gupta Ashok Kumar Priyadarshi Meena 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2212-2219
Novel chiral 1,3,2-oxazaphospholane-2-sulfides incorporating a dihydropyridine ring have been synthesized via phosphorylation of 2-aminopyridinium salts, followed by in situ oxidation and cyclocondensation with 2-(alkylamino)ethanol. Cyclic organothiophosphates thus obtained have been screened for their antioxidant properties. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. 相似文献
136.
An efficient regeneration system was established for an ethnomedicinal shrub Rhinacanthus nasutus from root-derived callus organogenesis. The root segments were cultured on MS medium supplemented with various concentrations of Kn (1.0–4.0 μM) alone or in combination with IBA (0.2–0.6 μM) or 2, 4-D (0.5–1.5 μM). The optimum frequency (94 %) of callus induction was recorded on MS medium supplemented with 3.0 μM Kn and 0.4 μM IBA. For shoot regeneration from callus, MS medium supplemented with different concentrations (1.0–7.0 μM) of BA or TDZ alone or in combination with NAA (0.2–1.0 μm) was employed. The highest frequency of shoot regeneration (91 %) and mean number of shoots (28.3) were observed on MS medium supplemented with 5.0 μM BA and 0.7 μM NAA. The shoots were excised and cultured on MS medium with 4.0 μM IBA produced 3.4 roots per shoot in 88 % cultures. Of the 65 plants transferred to soil 54 survived (83 %). The plants were transferred to field after successful hardening. RAPD analysis of the regenerated plants showed high similarity with the mother plant. 相似文献
137.
V. K. Mulik H. Naik S. V. Suryanarayana S. D. Dhole P. M. Prajapati B. S. Shivashankar K. C. Jagadeesan S. V. Thakre V. N. Bhoraskar A. Goswami 《Journal of Radioanalytical and Nuclear Chemistry》2013,296(3):1321-1329
The 56Fe(n, p)56Mn reaction cross-section at neutron energies of 5.9 ± 0.6, 9.85 ± 0.38, 14.8 ± 0.1 and 15.5 ± 0.7 MeV from the 7Li(p, n) as well as 3H(d, n) reactions has been experimentally measured using activation and off-line γ-ray spectrometric technique. The experimentally determined 56Fe(n, p)56Mn reaction cross-sections from the present work were compared with the latest available evaluated nuclear data libraries of ENDF/B-VII.1, JENDL-4.0 and JEFF-3.1/A. The present data along with the literature data in a wide range of neutron energies were interpreted in terms of competition between different reaction channels. The measured cross-sections were also estimated theoretically using TALYS-1.4 and EMPIRE-2.19 computer codes over neutron energies from near threshold to 20 MeV to compare with the experimental data. 相似文献
138.
H. Naik S. V. Suryanarayana K. C. Jagadeesan S. V. Thakare P. V. Joshi V. T. Nimje K. C. Mittal A. Goswami V. Venugopal S. Kailas 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(1):807-816
The radionuclide 99Mo, which has a half-life of 65.94 h was produced from 238U(γ, f) and 100Mo(γ, n) reactions using a 10 MeV electron linac at EBC, Kharghar Navi-Mumbai, India. This has been investigated since the daughter product 99mTc is very important from a medical point of view and can be produced in a generator from the parent 99Mo. The activity of 99Mo was analyzed by a γ-ray spectrometric technique using a HPGe detector. From the detected γ-rays activity of 140.5 and 739.8 keV, the amount of 99Mo produced was determined. For comparison, the amount of 99Mo from 238U(γ, f) and 100Mo(γ, n) reactions was also estimated using the experimental photon flux from 197Au(γ, n)196Au reaction. The amount of 99Mo from the detected γ-lines is in agreement with the estimated value for 238U(γ, f) and 100Mo(γ, n) reactions. The production of 99Mo activity from 238U(γ, f) and 100Mo(γ, n) reactions is a relevant and novel approach, which provides alternative routes to 235,238U(n, f) and 98Mo(n, γ) reactions, circumventing the need for a reactor. The viability and practicality of the 99Mo production from the 238U(γ, f) and 100Mo(γ, n) reactions alternative to 235,238U(n, f) and 98Mo(n, γ) reactions has been emphasize. An estimate has been also arrived based on the experimental data of present work to fulfill the requirement of DOE. 相似文献
139.
Hydrogel systems composed of kC/Xylan (kC/OSX or kC/BX) blends and linear polyvinylpyrrolidone (PVP) were prepared in the presence of water soluble initiator sodium persulphate (KPS) with microwave irradiation. The hydrogel materials were investigated by measuring their syneresis, swelling, gel fraction, and rheological properties. Physicochemical and rheological properties of the natural polysaccharide (kC/Xylans) blends were modified significantly after blending with PVP. The introduction of PVP and the formation of semi-interpenetrating polymer network (semi-IPN) structure improved the gelling properties of the resulting hydrogels. It has been proven, that a high incorporation of PVP could only be obtained if the hydrogels were prepared using KPS initiator and microwave irradiation in combination. FTIR, CP-MAS 13C NMR, and elemental analysis confirmed the presence of PVP in the blends but no direct evidence for covalent bonds could be obtained. 相似文献
140.
The boundary value problem in basic enzyme reactions is formulated and approximate expressions for substrate and product concentrations
are presented. He’s variational iteration method is used to give approximate and analytical solutions of non-linear reaction
equations containing a non-linear term related to enzymatic reaction. The relevant analytical solutions for the substrate,
enzyme, substrate-enzyme and product concentration profiles are discussed in terms of dimensionless reaction diffusion parameters
K, λ and e{\varepsilon}. 相似文献