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121.
K.V. Rajkumar R. Rajaraman Anish Kumar G. Amarendra T. Jayakumar C.S. Sundar 《哲学杂志》2013,93(20):1597-1610
Microstructural evolution of M250 grade maraging steel subjected to various thermal-aging treatments has been investigated using positron annihilation, X-ray diffraction, hardness and electron microscopy studies. Isochronal aging treatment in the range of 600–900 K, in steps of 100 K, was carried out and positron lifetime, austenite volume fraction and hardness values have been measured. The stages corresponding to point defect dynamics and formation of intermetallics have been clearly identified. Based on these results, measurements were performed on specimens isothermally aged at 755 K from 0.1 to 100 h to elucidate the time evolution of microstructural changes, and the results are discussed. 相似文献
122.
Pseudohalogenogermylenes versus Halogenogermylenes: Difference in their Complexation Behavior towards Group 6 Metal Carbonyls 下载免费PDF全文
Mahendra Kumar Sharma Soumen Sinhababu Dhirendra Yadav Goutam Mukherjee Prof. Gopalan Rajaraman Prof. Selvarajan Nagendran 《化学:亚洲杂志》2018,13(10):1357-1365
Pseudohalogenogermylenes [(iBu)2ATI]GeY (Y=NCO 4 , NCS 5 ) show different coordination behavior towards group 6 metal carbonyls in comparison to the corresponding halogenogermylenes [(iBu)2ATI]GeX (X=F 1 , Cl 2 , Br 3 ) (ATI=aminotroponiminate). The reactions of compounds 4 – 5 and 1 – 3 with cis‐[M(CO)4(COD)] (M=Mo, W, COD=cyclooctadiene) gave trans‐germylene metal complexes {[(iBu)2ATI]GeY}2M(CO)4 (Y=NCO, M=Mo 6 , W 11 ; Y=NCS, M=Mo 7 ) and cis‐germylene metal complexes {[(iBu)2ATI]GeX}2M(CO)4 (M=Mo, X=F 8 , Cl 9 , Br 10 ; M=W, X=Cl 12 ), respectively. Theoretical studies on compounds 7 and 9 reveal that donor–acceptor interactions from Mo to Ge atoms are better stabilized in the observed trans and cis geometries than in the hypothetical cis and trans structures, respectively. 相似文献
123.
Development of injectable high molecular weight hyaluronic acid hydrogels for cartilage regeneration
Shraddha Mondal Neena Haridas S. Sneha Letha V. Vijith G. Rajmohan 《高分子科学杂志,A辑:纯化学与应用化学》2016,53(8):507-514
The study focuses on developing hyaluronic acid (1200 kilo Dalton) hydrogels for cartilage regeneration. In spite of being highly biocompatible; a large amount of water absorption and easily degrading nature restricts the use of hyaluronic acid in the field of tissue regeneration. This can be rectified by crosslinking hyaluronic acid with a crosslinking agent such as divinyl sulfone; which results in a biocompatible hydrogel with superior rheological properties. Different amounts of divinyl sulfone have been used for crosslinking hyaluronic acid to get three types of hydrogels with differing properties. Swelling studies, rheology analysis, enzymatic degradation and scanning electron microscopic analysis were conducted on all the different types of hydrogels prepared. Viscoelastic properties of the hydrogel were analyzed so that a hydrogel with better elastic property and stability is obtained. Scanning electron microscopy was used to study the morphology of the HA hydrogels. The cytotoxicity testing was conducted to prove the non-toxic nature of the hydrogels and cell culture studies using adipose mesenchymal stem cells showed better adhesion and proliferation properties in all the three hydrogels. Thus hyaluronic acid hydrogel makes a promising material for cartilage regeneration. 相似文献
124.
Prescimone A Wolowska J Rajaraman G Parsons S Wernsdorfer W Murugesu M Christou G Piligkos S McInnes EJ Brechin EK 《Dalton transactions (Cambridge, England : 2003)》2007,(45):5282-5289
Reaction of the dinuclear complex [Mn2O2(bpy)4](ClO4)3 with H3cht (cis,cis-l,3,5-cyclohexanetriol) in MeCN produces the complex [Mn3(Hcht)2(bpy)4](ClO4)3.Et2O.2MeCN (1.Et2O.2MeCN). Dc magnetic susceptibility measurements reveal the existence of weak ferromagnetic exchange between the three Mn ions, leading to a spin ground state of S = 7, with D = -0.23 cm(-1). W-Band (94 GHz) EPR measurements on restrained powdered crystalline samples confirm the S = 7 ground state and determine the ground state zero-field splitting (ZFS) parameters of D = -0.14 cm(-1) and B4(0)= +1.5 x 10(-5) cm(-1). The apparent 4th order behaviour is due to a breakdown of the strong exchange limit approximation (J approximately d, the single-ion ZFS). Single crystal dc relaxation decay and hysteresis loop measurements reveal the molecule to have an appreciable energy barrier to magnetization relaxation, displaying low temperature sweep rate and temperature-dependent hysteresis loops. Density functional studies confirm the ferromagnetic exchange coupling between the Mn ions. 相似文献
125.
126.
Berg N Rajeshkumar T Taylor SM Brechin EK Rajaraman G Jones LF 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(19):5906-5918
The synthesis and magnetic characterisation of a series of bis-μ-alkoxide bridged Mn(III) dinuclear complexes of general formula [Mn(III)(2)(μ-OR)(2)(biphen)(2)(ROH)(x)(L)(y)] (where R = Me, Et; H(2) biphen = 2,2'-biphenol and L = terminally bonded N-donor ligand) is described, doubling the literature basis set for this type of complex. Building on these findings we have categorised all known μ-OR bridged Mn(III) dinuclear complexes into one of three classifications with respect to their molecular structures. We have then employed DFT and MO calculations to assess all potential magneto-structural correlations for this class of compound in order to identify the structural requirements for constructing ferromagnetic family members. Our analysis indicates that the most influential parameter which governs the exchange interaction in this class of compounds is the relative orientation of the JT axes of the Mn(III) atoms. A perpendicular orientation of the JT axes leads to a large ferromagnetic contribution to the exchange. These results also suggest that a large ferromagnetic interaction and a large anisotropy are unlikely to co-exist in such structural types. 相似文献
127.
R Rajaraman 《Pramana》1985,24(1-2):1-14
We review here classical Bogomolnyi bounds, and their generalisation to supersymmetric quantum field theories by Witten and
Olive. We also summarise some recent work by several people on whether such bounds are saturated in the quantised theory. 相似文献
128.
Some subtleties regarding regularizations in computing the soliton energy of degenerate systems are discussed. 相似文献
129.
Aaron J. Scott Julia Vallejo Arup Sarkar Lucy Smythe E. Regincs Martí Gary S. Nichol Wim T. Klooster Simon J. Coles Mark Murrie Gopalan Rajaraman Stergios Piligkos Paul J. Lusby Euan K. Brechin 《Chemical science》2021,12(14):5134
Reaction of Ni(OTf)2 with the bisbidentate quaterpyridine ligand L results in the self-assembly of a tetrahedral, paramagnetic cage [NiII4L6]8+. By selectively exchanging the bound triflate from [OTf⊂NiII4L6](OTf)7 (1), we have been able to prepare a series of host–guest complexes that feature an encapsulated paramagnetic tetrahalometallate ion inside this paramagnetic host giving [MIIX4⊂NiII4L6](OTf)6, where MIIX42− = MnCl42− (2), CoCl42− (5), CoBr42− (6), NiCl42− (7), and CuBr42− (8) or [MIIIX4⊂NiII4L6](OTf)7, where MIIIX4− = FeCl4− (3) and FeBr4− (4). Triflate-to-tetrahalometallate exchange occurs in solution and can also be accomplished through single-crystal-to-single-crystal transformations. Host–guest complexes 1–8 all crystallise as homochiral racemates in monoclinic space groups, wherein the four {NiN6} vertexes within a single Ni4L6 unit possess the same Δ or Λ stereochemistry. Magnetic susceptibility and magnetisation data show that the magnetic exchange between metal ions in the host [NiII4] complex, and between the host and the MX4n− guest, are of comparable magnitude and antiferromagnetic in nature. Theoretically derived values for the magnetic exchange are in close agreement with experiment, revealing that large spin densities on the electronegative X-atoms of particular MX4n− guest molecules lead to stronger host–guest magnetic exchange interactions.The tetrahedral [NiII4L6]8+ cage can reversibly bind paramagnetic MX41/2− guests, inducing magnetic exchange interactions between host and guest. 相似文献
130.
Chaboussant G Basler R Güdel HU Ochsenbein S Parkin A Parsons S Rajaraman G Sieber A Smith AA Timco GA Winpenny RE 《Dalton transactions (Cambridge, England : 2003)》2004,(17):2758-2766
The synthesis and structural characterisation of three small nickel(II) cages are reported, all stabilised by pivalate ligands. The magnetic properties of the cages have been studied by a combination of susceptibility measurements and inelastic neutron scattering. For a dinuclear cage, [Ni2(mu-OH2)(O2CCMe3)4(HO2CCMe3)4] 1 the ground state is S=2, with a ferromagnetic exchange interaction between the Ni(II) centres of J=0.32 meV and D(S=2)=-0.09 meV in the ground state. For a tetranuclear heterocubane cage, [Ni4(mu(3)-OMe)4(O2CCMe3)4(MeOH)4] 2, two ferromagnetic exchange interactions are found and an S=4 ground state observed. While the zero-field splitting of this state cannot be determined unambigiously the most likely value is DS=4=-0.035 meV. For a tetranuclear nickel butterfly, [Ni4(mu3-OH)2(O2CCMe3)6(EtOH)6] 3, three exchange interactions are required, two anti-ferromagnetic and one weakly ferromagnetic; the resulting ground state is S=0. The data enable us to estimate the zero-field splitting of single Ni(II) ions involved in the cage as Di=+1.0 meV. Both and are therefore expected to be new single molecule magnets. 相似文献