全文获取类型
收费全文 | 147篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
化学 | 118篇 |
晶体学 | 2篇 |
数学 | 11篇 |
物理学 | 22篇 |
出版年
2024年 | 2篇 |
2023年 | 2篇 |
2022年 | 9篇 |
2021年 | 4篇 |
2020年 | 5篇 |
2019年 | 6篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 11篇 |
2015年 | 3篇 |
2014年 | 7篇 |
2013年 | 12篇 |
2012年 | 10篇 |
2011年 | 11篇 |
2010年 | 9篇 |
2009年 | 11篇 |
2008年 | 7篇 |
2007年 | 7篇 |
2006年 | 7篇 |
2005年 | 7篇 |
2004年 | 5篇 |
2003年 | 2篇 |
2002年 | 4篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
排序方式: 共有153条查询结果,搜索用时 0 毫秒
41.
A systematic and novel quality by design–enabled, rapid, simple, and economic stability–indicating HPLC method for quantifying nirmatrelvir (NMT) was successfully developed and validated. An analytical target profile (ATP) was established, and critical analytical attributes (CAAs) were allocated to meet the ATP requirements. The method used chromatographic separation using a Purosphere column with a 4.6 mm inner diameter × 250 mm (2.5 μm). The analysis occurred at 50°C with a flow rate of 1.2 mL/min and detection at 220 nm. A 10 μL sample was injected, and the mobile phase consisted of two components: mobile phase A, containing 0.1% formic acid in water (20%), and mobile phase B, containing 0.1% formic acid in acetonitrile (80%). The diluent was prepared by mixing acetonitrile and water at a 90:10 v/v ratio. The retention time for the analyte was determined to be 2.78 min. Accuracy exceeded 99%, and the correlation coefficient was greater than 0.999. The validated HPLC method was characterized as precise, accurate, and robust. Significantly, NMT was found to be susceptible to alkaline, acidic, and peroxide conditions during forced degradation testing. The stability-indicating method developed effectively separated the degradation products formed during stress testing, underlining its effectiveness in stability testing and offering accuracy, reliability, and sensitivity in determining NMT. 相似文献
42.
Ponuganti Pallavi Penumaka Nagababu Sirasani Satyanarayana 《Helvetica chimica acta》2007,90(3):627-639
Pseudo‐first‐order reaction kinetics and binding studies of trans‐[Co(en)2(Et)H2O] complex with 1H‐imidazole, substituted 1H‐imidazoles, histidine, histamine, glycine and glycine ethyl ester were investigated by means of spectrophotometric techniques. Equilibrium constants were determined as a function of pH at 25°. Binding and kinetic studies were correlated to basicity and steric hindrance. From the equilibrium data, it was found that the entering nucleophile is participating in the transition state, an Id mechanism is proposed. The effect of the incoming ligands on the complex was studied by molecular mechanics. The interaction of trans‐[Co(en)2(Et)H2O] with CT DNA was studied spectrophotometrically. 相似文献
43.
Umaprasana Ojha Pallavi Kulkarni Jagdeep Singh Rudolf Faust 《Journal of polymer science. Part A, Polymer chemistry》2009,47(14):3490-3505
The syntheses of {‐poly(L ‐lactide) (PLLA)‐b‐polyisobutylene (PIB)‐}n multiblock copolymers were accomplished for the first time by chain extension of PLLA‐b‐PIB‐b‐PLLA triblock copolymers. Well‐defined PLLA‐b‐PIB‐b‐PLLA triblock copolymers with predictable Mns, low PDIs (1.10–1.18) and excellent blocking efficiencies were prepared by anionic ring‐opening polymerizations of L ‐lactide initiated with hydroxyallyl telechelic PIB (HO‐Allyl‐PIB‐Allyl‐OH) in toluene at 110 °C. The triblock copolymers were successfully chain extended with 4,4′‐methylenebis(phenylisocyanate) (MDI) to obtain the multiblock copolymers with good gravimetric yields of ~86 to 96%. The chain‐extended polymers were soluble in a range of common organic solvents. The block copolymers showed two glass transition temperatures in differential scanning calorimetric analysis for the PIB and PLLA blocks indicating microphase separation, which was supported by atomic force microscopy images. The as‐synthesized compression molded multiblock copolymers exhibited tensile strengths in the range of 8–24 MPa with elongations at break in the range of 2.5–400%. The static and dynamic mechanical properties showed a strong dependence on the relative PLLA content in the copolymer. The dynamic mechanical analysis also indicated microphase separation at higher PLLA compositions. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3490–3505, 2009 相似文献
44.
Pallavi Singh Devandra K. Tripathi Shikha Jaiswal H. K. Dixit 《Optical and Quantum Electronics》2014,46(11):1435-1444
In the paper a novel scheme for an all-optical buffer and OR logic gates based on Mach–Zehnder interferometer structure is discussed. The operations of the scheme with 10 Gb/s return to zero pseudorandom bit streams simulated correctly with extinction ratio 19.21 and 17.61 dB where Q-factor 25.94 and 11.22 for buffer and OR gate respectively. With the help of numerical analyses, it can be seen that the extinction ratio of the OR operation is degraded and the output pattern effect is decreased by 0.9 dB compared to optical buffer schemes under the same condition. Furthermore, the carrier recovery time of a semiconductor optical amplifier is no longer a crucial parameter to restrict the operation speed of this scheme. The scheme is also potentially capable of multi input OR operation at higher speed. 相似文献
45.
A concise synthesis of key isoxazole-based side chain of Micafungin, an USFDA approved anti-fungal agent, has been delineated. The route design notably involves a one pot regioselective isoxazole construction from the corresponding aryl aldehyde and alkyne intermediates. 相似文献
46.
A short synthesis of the revised structure of the marine natural product tridachiahydropyrone is described. A novel biomimetic photochemical electrocyclization was employed to construct the bicyclic carbon framework from an open-chain polyene precursor. The spectroscopic data matched that of the isolated natural product, supporting a revised structure of this complex metabolite. 相似文献
47.
Pallavi Pushp Frederico Castelo Ferreira Joaquim M. Sampaio Cabral Mukesh Kumar Gupta 《Polymer Science Series A》2017,59(4):515-523
Polycaprolactone (PCL) is a popular synthetic polymer used in the field of cardiac tissue engineering (CTE) due to its non-toxic degraded by products and low cost manufacturing method. However, hydrophobic nature of this material limits its wide spread application in different cell interaction processes. Therefore, current study aims to chemically modify PCL made random and aligned nanofibers with collagen coating mimicking the oriented matrix of the cardiac cells. Morphological and chemical properties of the electrospun PCL nanofibers were evaluated by SEM, FTIR, XRD and water contact angle measurement. Results indicated that the anisotropic characteristics of aligned nanofibers promoted cell attachment and alignment, which closely match the requirements of native cardiac cells. Thus, aligned nanofibers could be preferred for cardiac tissue regeneration and defects over random nanofibers. 相似文献
48.
Yadav VK Kumar V Chhikara N Kumar S Manral P Kashav T Saini S Srinivasan A Singh S Singh TP Yadav S 《Journal of separation science》2011,34(9):1076-1083
The seminal plasma comprises secretions from various accessory sex glands. During fertilization spermatozoa undergo complex sequences of precisely timed events that are regulated by the activation of different intracellular signaling pathways. The precision and efficacy of these pathways are often influenced by the assembly and interactions of multiprotein complexes, thereby directing the flow of regulatory information. Our knowledge about these protein complexes present in human seminal plasma (HuSP) is limited. Here we report the identification and characterization of a native high molecular weight zinc-binding multiprotein complex from HuSP by utilizing 2-DE followed by MS. Twenty-six proteins representing isoforms and/or fragments of 11 different proteins were found to be assembled in this complex. Prostate-specific antigen, zinc α2-glycoprotein, prostatic acid phosphatase, and prolactin inducible protein were the major proteins of this complex. Dynamic light scattering experiments revealed changes in aggregation pattern accompanied with deviation from physiological pH and in presence of SDS. However, no significant changes were observed in the presence of physiological ligands such as zinc and fructose. The present study will be useful and contribute to guide the future studies performed for elucidation of biological significance of this native complex in HuSP. 相似文献
49.
Pallavi ThakurB. Kumaraswamy G. Raji ReddyRakeshwar Bandichhor K. Mukkanti 《Tetrahedron letters》2012,53(29):3703-3705
The first stereoselective total synthesis of polyacetylene panaxjapyne C is described. The key reactions include regioselective opening of the epoxide and Cadiot-Chodkiewicz cross-coupling reactions. l-Ascorbic acid was used as a chiral pool material for the construction of the both terminal acetylenes. 相似文献
50.
Surajit Saha Pallavi Ghalsasi D. V. S. Muthu Surjeet Singh R. Suryanarayanan A. Revcolevschi A. K. Sood 《Journal of Raman spectroscopy : JRS》2012,43(8):1157-1165
We revisit the assignment of Raman phonons of rare‐earth titanates by performing Raman measurements on single crystals of O18 isotope‐rich spin ice and nonmagnetic pyrochlores and compare the results with their O16 counterparts. We show that the low‐wavenumber Raman modes below 250 cm−1 are not due to oxygen vibrations. A mode near 200 cm−1, commonly assigned as F2g phonon, which shows highly anomalous temperature dependence, is now assigned to a disorder‐induced Raman active mode involving Ti4+ vibrations. Moreover, we address here the origin of the ‘new’ Raman mode, observed below TC ~ 110 K in Dy2Ti2O7, through a simultaneous pressure‐dependent and temperature‐dependent Raman study. Our study confirms the ‘new’ mode to be a phonon mode. We find that dTC/dP = + 5.9 K/GPa. Temperature dependence of other phonons has also been studied at various pressures up to ~8 GPa. We find that pressure suppresses the anomalous temperature dependence. The role of the inherent vacant sites present in the pyrochlore structure in the anomalous temperature dependence is also discussed. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献