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51.
Balakrishnan S. Anju Neeraja R. Nair Dr. Subrata Kundu 《Angewandte Chemie (International ed. in English)》2023,62(48):e202311523
Nitrite (NO2−) and nitric oxide (NO) interconversion is crucial for maintaining optimum NO flux in mammalian physiology. Herein we demonstrate that [ L 2CuII(nitrite)]+ moieties (in 2 a and 2 b ; where, L = Me2PzPy and Me2PzQu ) with distorted octahedral geometry undergo facile reduction to provide tetrahedral [ L 2CuI]+ (in 3 a and 3 b ) and NO in the presence of biologically relevant reductants, such as 4-methoxy-2,6-di-tert-butylphenol (4-MeO-2,6-DTBP, a tyrosine model) and N-benzyl-1,4-dihydronicotinamide (BNAH, a NAD(P)H model). Interestingly, the reaction of excess NO gas with [ L 2CuII(MeCN)2]2+ (in 1 a ) provides a putative {CuNO}10 species, which is effective in mediating the nitrosation of various nucleophiles, such as thiol and amine. Generation of the transient {CuNO}10 species in wet acetonitrile leads to NO2− as assessed by Griess assay and 14N/15N-FTIR analyses. A detailed study reveals that the bidirectional NOx-reactivity, namely, nitrite reductase (NIR) and NO oxidase (NOO), at a common CuII site, is governed by the geometric-preference-driven facile CuII/CuI redox process. Of broader interest, this study not only highlights potential strategies for the design of copper-based catalysts for nitrite reduction, but also strengthens the previous postulates regarding the involvement of red copper proteins in denitrification. 相似文献
52.
Kundu T Sarkar B Mondal TK Mobin SM Urbanos FA Fiedler J Jiménez-Aparicio R Kaim W Lahiri GK 《Inorganic chemistry》2011,50(11):4753-4763
Using the [RuCl(μ-tppz)ClRu](2+) [tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine] platform for bridging two o-quinone/catecholate two-step redox systems (unsubstituted, Q(n), or 3,5- di-tert-butyl-substituted, DTBQ(n)), we have obtained the stable complexes [(Q(?-))Ru(II)Cl(μ-tppz)ClRu(II)(Q(?-))] (1) and the structurally characterized [(DTBQ(?-))Ru(II)Cl(μ-tppz)ClRu(II)(DTBQ(?-))] (2). The compounds exhibit mostly quinone-ligand-based redox activity within a narrow potential range, high-intensity near-IR absorptions (λ(max) ≈ 920 nm; ε > 50,000 M(-1) cm(-1)), and variable intra- and intermolecular spin-spin interactions. Density functional theory calculations, electron paramagnetic resonance (EPR), and spectroelectrochemical results (UV-vis-near-IR region) for three one-electron-reduction and two one-electron-oxidation processes were used to probe the electronic structures of the systems in the various accessible valence states. EPR spectroscopy of the singly charged doublet species showed semiquinone-type response for 1(+), 2(+), and 2(-), while 1 exhibits more metal based spin, a consequence of the easier reduction of Q as compared to DTBQ. Comparison with the analogous redox series involving a more basic N-phenyliminoquinone ligand reveals significant differences related to the shifted redox potentials, different space requirements, and different interactions between the metals and the quinone-type ligands. As a result, the tppz bridge is reduced here only after full reduction of the terminal quinone ligands to their catecholate states. 相似文献
53.
Ojah Namita Thakur Susmita Gogoi Dolly Ahmed Gazi Ameen Mandal Manabendra Doley Robin Choudhury Arup Jyoti 《Plasma Chemistry and Plasma Processing》2022,42(1):147-162
Plasma Chemistry and Plasma Processing - This work reports an investigation of the discharge characteristics of atmospheric dielectric barrier discharge (DBD) plasma in terms of I-V curves and... 相似文献
54.
Chatterjee PB Kundu N Bhattacharya S Choi KY Endo A Chaudhury M 《Inorganic chemistry》2007,46(14):5483-5485
Isovalent mu-oxo divanadium(V) compounds [L1VO(mu-O)VO(salen)] (1) and its bromo derivative [L2VO(mu-O)VO(salen)].CH3CN (2) (both H2L1 and H2L2 are tridentate dithiocarbazate-based ONS ligands) with ligands providing donor set and coordination number asymmetry in tandem have been synthesized for the first time; confirmations in favor of these unsymmetrical molecular structures have come from single-crystal X-ray diffraction analysis, as well as from NMR (both 1H and 51V) spectroscopy. 相似文献
55.
S Prabhakar P Krishna A Kundu S Roy M Vairamani 《Rapid communications in mass spectrometry : RCM》1999,13(15):1564-1572
The electron impact (EI) mass spectra of allyl aryl selenides showed abundant molecular ions and many fragment ions containing the selenium atom. alpha-Cleavage is the dominant process in the fragmentation of selenides, and cleavage product ions are characteristic of the substituents. In the case of 3-methyl allyl and related aryl selenides, characteristic delta-hydrogen migration to the selenium atom is observed. A McLafferty-type rearrangement is found in benzyl allyl selenides and substituted alkyl allyl selenides. The charge on the rearrangement products preferably remains on the fragments containing the phenyl group. The [M - SeH](+), [M - CH(3)](+) and [M - C(2)H(4)](+) ions are found only in the EI mass spectrum of allyl phenyl selenide, and are attributed to a Claisen rearrangement in the source of the mass spectrometer. All structurally informative fragmentation processes are supported by collision induced dissociation spectra of molecular ions. The fragmentation patterns found in methane chemical ionization (CI) spectra of the selenides were significantly different from those observed in EI. The EI and CI mass spectra of analogous sulfides showed similar behaviour to that observed in the corresponding selenides. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
56.
Alok K. Mukherjee Subhadra Guha M. Wahab Khan Nitya G. Kundu Madeleine Helliwell 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(1):85-87
Two isoindolin‐1‐one derivatives, (Z)‐3‐benzylidene‐N‐phenylisoindolin‐1‐one, C21H15NO, (II), and (Z)‐3‐benzylidene‐N‐(4‐methoxyphenyl)isoindolin‐1‐one, C22H17NO2, (III), were synthesized by the palladium‐catalysed heteroannulation. The molecules of both compounds have a Z configuration. The interplanar angles between the five‐ and six‐membered rings of the isoindolinone moiety in (II) and (III) are 1.66 (11) and 2.26 (7)°, respectively. The phenyl rings at the N‐position in (II) and (III) are twisted out of the C4N ring plane by 62.77 (11) and 67.10 (7)°, respectively. The substitutions at the N and C‐3 positions of the isoindolinone system have little influence on the molecular dimensions of the resulting compounds. 相似文献
57.
A spectrophotometric method has been developed for determination of trace amounts of platinum in glass. The method is based on the extraction of platinum(II) from 1M hydrochloric acid containing 0.2M stannous chloride and 4 x 10(-4)M dithizone onto polyurethane foam, elution with acetone (containing 3% v/v concentrated hydrochloric acid) and measurement of the absorbance of the eluate at 530 nm. Beer's law is obeyed up to 10.0 microg/ml Pt. The minimum platinum level in the eluate that can be determined by this method is 0.1 microg/ml. 相似文献
58.
Simone S. Silva Banani Kundu Shenzhou Lu Rui L. Reis Subhas C. Kundu 《Macromolecular bioscience》2019,19(3)
Chinese nonmulberry temperate oak tasar/tussah, Antheraea pernyi (Ap) silk is a natural biopolymer that has attracted considerable attention as a biomaterial. The proteinaceous components of Ap silk proteins, namely fibroin and sericin may represent an alternative over mulberry Bombyx mori silk proteins. In fact, the silk fibroin (SF) of Ap is rich in Arginyl‐Glycyl‐Aspartic acid (RGD) peptides, which facilitate the adhesion and proliferation of various cell types. The possibility of processing Ap silk proteins into different distinct 2D‐ and 3D‐based matrices is described in earlier studies, such as membranes, nanofibers, scaffolds, and micro/nanoparticles, contributing to a different rate of degradation, mechanical properties, and biological performance useful for various biomedical applications. This review summarizes the current advances and developments on nonmulberry Chinese oak tasar silk protein (fibroin and sericin)‐based biomaterials and their potential uses in tissue engineering, regenerative medicine, and therapeutic delivery strategies. 相似文献
59.
Modular Functionalization of Arenes in a Triply Selective Sequence: Rapid C(sp2) and C(sp3) Coupling of C−Br,C−OTf,and C−Cl Bonds Enabled by a Single Palladium(I) Dimer 下载免费PDF全文
Dr. Sinead T. Keaveney Gourab Kundu Prof. Dr. Franziska Schoenebeck 《Angewandte Chemie (International ed. in English)》2018,57(38):12573-12577
Full control over multiple competing coupling sites would enable straightforward access to densely functionalized compound libraries. Historically, the site selection in Pd0‐catalyzed functionalizations of poly(pseudo)halogenated arenes has been unpredictable, being dependent on the employed catalyst, the reaction conditions, and the substrate itself. Building on our previous report of C?Br‐selective functionalization in the presence of C?OTf and C?Cl bonds, we herein complete the sequence and demonstrate the first general arylations and alkylations of C?OTf bonds (in <10 min), followed by functionalization of the C?Cl site (in <25 min), at room temperature using the same air‐ and moisture‐stable PdI dimer. This allowed the realization of the first general and triply selective sequential C?C coupling (in 2D and 3D space) of C?Br followed by C?OTf and then C?Cl bonds. 相似文献
60.
Rao CN Kundu AK Seikh MM Sudheendra L 《Dalton transactions (Cambridge, England : 2003)》2004,(19):3003-3011
Electronic phase separation is increasingly getting recognized as a phenomenon of importance in understanding the magnetic and electron transport properties of transition metal oxides. The phenomenon dominates the rare-earth manganates of the formula Ln(1-x)A(x)MnO(3)(Ln = rare earth and A = alkaline earth) which exhibit ferromagnetism and metallicity as well as charge-ordering, depending on the composition, size of A-site cations and external factors such as magnetic and electric fields. We discuss typical phase separation scenarios in the manganates, with particular reference to Pr(1-x)Ca(x)MnO(3)(x= 0.3-0.4), (La(1-x)Ln(x))(0.7)Ca(0.3)MnO(3)(Ln = Pr, Nd, Gd and Y) and Nd(0.5)Sr(0.5)MnO(3). Besides discussing the magnetic and electron transport properties, we discuss electric field effects. Rare-earth cobaltates of the type Pr(0.7)Ca(0.3)CoO(3) and Gd(0.5)Ba(0.5)CoO(3) also exhibit interesting magnetic and electron transport properties which can be understood in terms of phase separation. 相似文献