全文获取类型
收费全文 | 223篇 |
免费 | 2篇 |
专业分类
化学 | 119篇 |
晶体学 | 8篇 |
力学 | 22篇 |
数学 | 28篇 |
物理学 | 48篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 5篇 |
2020年 | 3篇 |
2019年 | 7篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2015年 | 6篇 |
2014年 | 9篇 |
2013年 | 12篇 |
2012年 | 12篇 |
2011年 | 24篇 |
2010年 | 5篇 |
2009年 | 9篇 |
2008年 | 15篇 |
2007年 | 12篇 |
2006年 | 9篇 |
2005年 | 4篇 |
2004年 | 8篇 |
2003年 | 5篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 6篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1975年 | 3篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1970年 | 2篇 |
1969年 | 1篇 |
排序方式: 共有225条查询结果,搜索用时 15 毫秒
101.
The paper describes the synthesis of new 1,3,3‐triary‐1′‐methylspiro[azetidine‐2,3′‐indoline]‐2′,4‐diones from reaction of the 2‐diazo‐1,2‐diarylethanones with 3‐arylimino‐1‐methyl‐2‐indolinones. The compounds have been characterized by satisfactory analytical and spectral (IR, 1H NMR and 13C NMR) data. The diarylketenes, generated in situ from thermal decomposition of the 2‐diazo‐1,2‐diarylethanones, react with azomethine linkage in preference to carbonyl group leading to the formation of products. 相似文献
102.
103.
We describe the calculation of inclusive Higgs boson production at hadronic colliders at next-to-next-to-leading order (NNLO)
in perturbative quantum chromodynamics. We have used the technique developed in ref. [4]. Our results agree with those published
earlier in the literature. 相似文献
104.
P. Thomas R. S. Ernest Ravindran K. B. R. Varma 《Journal of Thermal Analysis and Calorimetry》2014,115(2):1311-1319
Poly(methyl methacrylate) (PMMA) and CaCu3Ti4O12 (CCTO) composites were fabricated via melt mixing followed by hot pressing technique. These were characterized using X-ray diffraction, thermo gravimetric, thermo mechanical, differential scanning calorimetry, fourier transform infrared (FTIR) and Impedance analyser for their structural, thermal and dielectric properties. Composites were found to have better thermal stability than that of pure PMMA. However, there was no significant difference in the glass transition (T g ) temperature between the polymer and the composite. The appearance of additional vibrational frequencies in the range 400–600 cm?1 in FTIR spectra indicated a possible interaction between PMMA and CCTO. The composite, with 38 vol% of CCTO (in PMMA), exhibited remarkably low dielectric loss at high frequencies and the low-frequency relaxation is attributed to the interfacial polarization/MWS effect. The origin of AC conductivity particularly in the high-frequency region was attributed to the electronic polarization. 相似文献
105.
Tarjeet Singh Girija S. Singh Ram Lakhan 《Phosphorus, sulfur, and silicon and the related elements》2013,188(10):1442-1448
Abstract The reactions of benzoylisothiocyanates with salicylamide in pyridine-xylene solution occurs chemoselectively at the hydroxyl group of the salicylamide to afford the corresponding O-benzoyl derivatives. The latter products, on prolonged heating in pyridine-xylene solution, undergo cyclodehydration to give 2-aryl-4H-benzo[e][1,3]oxazin-4-ones in good yields. These compounds could also be synthesized by a direct one-pot reaction of benzoylisothiocyanates with salicylamide by slow addition of benzoylisothiocyanates into a solution of salicylamide in xylene-pyridine solution under reflux. The products have been characterized on the basis of satisfactory analytical and spectral data. 相似文献
106.
B. Ravindran R. Sravani A. B. Mandal S. M. Contreras-Ramos G. Sekaran 《Journal of Thermal Analysis and Calorimetry》2013,111(3):1675-1684
Animal fleshing (ANFL) is the main solid waste generated during manufacturing leather, which should be disposed friendly to the environment. The effect of epigeic earthworm Eudrilus eugeniae (with and without addition) to transform fermented ANFL in solid state (SSF) and submerged state (SmF) mixed with cow dung and leaf litter into value added product was studied in a vermibioreactor at low residence period (25 days). The products were characterised for pH and C:N ratio and the results were declined at the end of the treatment process with significant reduction in earthworm processed product. The maturity and the chemical changes of the final products were determined using spectroscopic analysis as UV–Visible Spectroscopy in which worm products (vermicompost) reached >5; this indicated that they were well humified. The FT-IR analyses results confirmed the complete mineralisation of polypeptides, polysaccharides, aliphatic methyl groups and lignin, and formation of a deep nitrate band in worm product compared to without worm processed product. Thermogravimetry (TG) and differential scanning calorimetry analyses were carried out in the initial mixture and final products to identify the mass loss and quantitative and qualitative information regarding physical and chemical changes occurred during composting process. The overall results indicated that the maturity of vermicompost (with worms) was in the order SSF > SmF > control. The results indicate that the combination of both fermentation and bacterial/vermicomposting (without worms/with worms) reduced the overall time required for production of well humified organic manure especially with worms. 相似文献
107.
Vidhu VK Aromal SA Philip D 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,83(1):392-397
Green synthesis of noble metal nanoparticles is a vast developing area of research. In this paper we report the green synthesis of silver nanoparticles using aqueous seed extract of Macrotyloma uniflorum. The effect of experimental parameters such as amount of extract, temperature and pH on the formation of silver nanoparticles was studied. The as prepared samples are characterized using XRD, TEM, UV-Visible and FTIR techniques. The formation of silver nanoparticles is evidenced by the appearance of signatory brown colour of the solution and UV-vis spectra. The XRD analysis shows that the silver nanoparticles are of face centered cubic structure. Well-dispersed silver nanoparticles with anisotropic morphology having size ~12 nm are seen in TEM images. FTIR spectrum indicates the presence of different functional groups in capping the nanoparticles. The possible mechanism leading to the formation of silver nanoparticles is suggested. 相似文献
108.
In this paper we consider not necessarily symmetric co-positive as well as semi-monotoneQ-matrices and give a set of sufficient conditions for such matrices to beR
0-matrices. We give several examples to show the sharpness of our results. Construction of these examples is based on the following elementary proposition: IfA is a square matrix of ordern whose first two rows are identical and bothA
11 andA
22 areQ-matrices whereA
ii
stands for the principal submatrix ofA obtained by deleting rowi and columni fromA, thenA is aQ-matrix.Dedicated to our colleague and friend B. Ramachandran on his sixtieth birthday.Corresponding author. 相似文献
109.
We analyze the various inputs that go into computing the recently measured first moment of the proton spin structure functiong
1
p
(x). The basic inputs are the various valence and sea quark polarisations and the gluonic contribution coming through axial
anomaly. We show that the quark model predictions for valence quark polarisations, suitably modified to accommodate Bjorken
sum rule, are consistent with measured value of moment of the spin structure function. 相似文献
110.
Philip D Unni C Aromal SA Vidhu VK 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,78(2):899-904
A facile bottom-up 'green' and rapid synthetic route using Murraya Koenigii leaf extract as reducing and stabilizing agent produced silver nanoparticles at ambient conditions and gold nanoparticles at 373 K. The nanoparticles were characterized using UV-vis, transmission electron microscopy (TEM), X-ray diffraction (XRD) and FTIR analysis. This method allows the synthesis of well-dispersed silver and gold nanoparticles having size ~10 nm and ~20 nm, respectively. Silver nanoparticles with size ~10 nm having symmetric SPR band centered at 411 nm is obtained within 5 min of addition of the extract to the solution of AgNO3 at room temperature. Nearly spherical gold nanoparticles having size ~20 nm with SPR at 532 nm is obtained on adding the leaf extract to the boiling solution of HAuCl4. Crystallinity of the nanoparticles is confirmed from the high-resolution TEM images, selected area electron diffraction (SAED) and XRD patterns. From the FTIR spectra it is found that the biomolecules responsible for capping are different in gold and silver nanoparticles. A comparison of the present work with the author's earlier reports on biosynthesis is also included. 相似文献