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71.
Torsten Roth Vladislav Vasilenko Callum G. M. Benson Hubert Wadepohl Dominic S. Wright Lutz H. Gade 《Chemical science》2015,6(4):2506-2510
A simple, “click” synthetic approach to a new type of hybrid phosph(III)azane/NHC system is described. The presence of the phosphazane P2N2 ring unit, with P atoms flanking the NCN fragment and with this ring perpendicular to the binding site of the NHC, provides unique opportunities for modifying the electronic and steric character of these carbenes. 相似文献
72.
73.
David John Benson 《Archiv der Mathematik》2017,109(5):413-414
Let K be a field of characteristic zero, and let R be a ring containing K. Then either \(R^\times = K^\times \) or \(K^\times \) is a subgroup of infinite index in \(R^\times \). 相似文献
74.
A phenomenological high strain rate model with failure for ice 总被引:3,自引:0,他引:3
Kelly S. Carney David J. Benson Paul DuBois Ryan Lee 《International Journal of Solids and Structures》2006,43(25-26):7820-7839
75.
Grainger RS Patel B Kariuki BM Male L Spencer N 《Journal of the American Chemical Society》2011,133(15):5843-5852
Three peri-substituted trisulfide-2-oxides are prepared by treatment of 1,8-naphthalene dithiols with thionyl chloride and pyridine. The 1,2,3-trithiane-2-oxide ring adopts a sofa conformation in the solid state, with a pseudoaxial oxygen and evidence of ring strain (peri-interaction). Heating the trisulfide-2-oxides in the presence of a diene results in formal sulfur monoxide (SO) transfer to form unsaturated cyclic sulfoxides, along with a recyclable 1,8-naphthalene disulfide. The presence of o-methoxy or o-tert-butyl substituents on the naphthalene ring lowers the temperature and increases the rate at which SO transfer occurs. Trapping experiments and kinetic studies are consistent with the generation of triplet SO, followed by in situ trapping by diene. Transfer of SO also occurs upon irradiation at room temperature, but yields of sulfoxide are lower. Dehydration of the sulfoxides under Pummerer conditions gives thiophenes, including the naturally occurring thioperillene. Two dienes form thiophenes directly under the SO transfer conditions. The methodology is applied in a formal synthesis of the antiplatelet medication Plavix. 相似文献
76.
Patel B Carlisle J Bottle SE Hanson GR Kariuki BM Male L McMurtrie JC Spencer N Grainger RS 《Organic & biomolecular chemistry》2011,9(7):2336-2344
Acyclic bissulfonylnitroxides have never been isolated, and degrade through fragmentation. In an approach to stabilising a bissulfonylnitroxide radical, the cyclic, peri-substituted N,N-bissulfonylhydroxylamine, 2-hydroxynaphtho[1,8-de][1,3,2]dithiazine 1,1,3,3-tetraoxide (1), has been prepared by formal nitrogen insertion into the sulfur-sulfur bond of a sulfinylsulfone, naphtho[1,8-cd][1,2]dithiole 1,1,2-trioxide. The heterocyclic ring of 1 is shown to adopt a sofa conformation by X-ray crystallography, with a pseudo-axial hydroxyl group. N,N-Bissulfonylhydroxylamine 1 displays high thermal, photochemical and hydrolytic stability compared to acyclic systems. EPR analysis reveals formation of the corresponding bissulfonylnitroxide 2 upon oxidation of 1 with the Ce(IV) salts CAN and CTAN. Although 2 does not undergo fragmentation, it cannot be isolated, since hydrogen atom abstraction to reform 1 occurs in situ. The stability and reactivity of 1 and 2 are compared with the known cyclic benzo-fused N,N-bissulfonylhydroxylamine, N-hydroxy-O-benzenedisulfonimide (6), for which the X-ray data, and EPR of the corresponding nitroxide 10, are also reported for the first time. 相似文献
77.
Jeffs L Arquier D Kariuki B Bethell D Page PC Hutchings GJ 《Organic & biomolecular chemistry》2011,9(4):1079-1084
By synthesising S-2-phenyl-N-(4-nitrophenyl)aziridine from S-phenylglycinol, it has been demonstrated that the aziridination of styrene by [N-(4-nitrobenzenesulfonyl)imino]phenyliodinane (nosyliminophenyliodinane, PhINNs) in the presence of S,S-2,2'-isopropylidene-bis(4-phenyl-2-oxazoline), catalysed by copper(II) triflate in CH(3)CN solution or heterogeneously by CuHY, has predominantly an R-configuration. The enantioselectivity of the aziridination of styrene by [N-arenesulfonylimino]-phenyliodinanes catalysed by copper-exchanged zeolite Y (CuHY), in conjunction with a chiral bis-oxazoline ligand, has been re-examined. In the case of PhINNs, it is shown that the product mixture of enantiomeric aziridines, on treatment with hexane, gives rise to a solid phase of low enantiomeric excess (ee) and a solution phase of high ee. Separation of the solid phase and recrystallisation afforded a true racemate (racemic compound), which has been confirmed by X-ray crystallography. The aziridine obtained from the solution phase could be recrystallised to produce the pure enantiomer originally in excess. A consequence of the new findings is that previous reports on the enantioselectivity of copper-catalysed aziridination, both in heterogeneous and homogeneous conditions, should be regarded with caution if the analytical procedure involved HPLC with injection of the enantiomeric mixture in a hexane-rich solvent. Such a method has been used in previous work from this laboratory, but has also been used elsewhere, following the procedure developed by Evans and co-workers when the (homogeneous) copper-catalysed aziridination by PhINTs was first discovered. Evidently, the change of substituent in the benzenesulfonyl group reduces the solubility in hexane, affording a solution phase of enhanced ee. 相似文献
78.
Newman PD Cavell KJ Hallett AJ Kariuki BM 《Dalton transactions (Cambridge, England : 2003)》2011,40(35):8807-8813
A tridentate N^C^N ligand, 1, containing a bicyclic central NHC ring and two flanking pyridyl groups has been coordinated to Rh(I) and Ir(I) to give complexes of the type [M(κ(3)-1)(1,5-COD)]PF(6) (2 M = Rh; 3 M = Ir). In contrast to our earlier study with this ligand, the complexes have been shown to approximate to a trigonal bipyramidal geometry in the solid state and exist as an isomeric mixture in solution as determined by (1)H and (13)C NMR spectroscopy. Electrochemical studies revealed that both complexes undergo a 1-electron oxidation with the potential of the Rh complex 0.1 V less than that of the Ir complex in CH(2)Cl(2). Preliminary DFT studies confirm the lowest energy conformations as those seen in the solid state and show the location and energy of the HOMOs to be identical in 2 and 3. Partial charge analysis shows a greater positive charge on the Ir in 3 compared to the Rh in 2. Some preliminary studies of hydrogenation reactivity have shown the complexes to be efficient for both transfer and direct hydrogenation of prochiral ketones and alkenes at moderate temperatures but without any discernible enantioselectivity. 相似文献
79.
Dreyfuss JM Jacobs C Gindin Y Benson G Staples GO Zaia J 《Analytical and bioanalytical chemistry》2011,399(2):727-735
Hydrophilic interaction chromatography (HILIC) liquid chromatography/mass spectrometry (LC/MS) is appropriate for all native
and reductively aminated glycan classes. HILIC carries the advantage that retention times vary predictably according to oligosaccharide
composition. Chromatographic conditions are compatible with sensitive and reproducible glycomics analysis of large numbers
of samples. The data are extremely useful for quantitative profiling of glycans expressed in biological tissues. With these
analytical developments, the rate-limiting factor for widespread use of HILIC LC/MS in glycomics is the analysis of the data.
In order to eliminate this problem, a Java-based open source software tool, Manatee, was developed for targeted analysis of
HILIC LC/MS glycan datasets. This tool uses user-defined lists of compositions that specify the glycan chemical space in a
given biological context. The program accepts high-resolution LC/MS data using the public mzXML format and is capable of processing
a large data file in a few minutes on a standard desktop computer. The program allows mining of HILIC LC/MS data with an output
compatible with multivariate statistical analysis. It is envisaged that the Manatee tool will complement more computationally
intensive LC/MS processing tools based on deconvolution and deisotoping of LC/MS data. The capabilities of the tool were demonstrated
using a set of HILIC LC/MS data on organ-specific heparan sulfates. 相似文献
80.
Short R Carta M Bezzu CG Fritsch D Kariuki BM McKeown NB 《Chemical communications (Cambridge, England)》2011,47(24):6822-6824
Microporous polymers derived from the 1,2- and 1,4-regioisomers of di(3',4'-dihydroxyphenyl)tetraphenylbenzene have very different properties with the former being composed predominantly of cyclic oligomers whereas the latter is of high molar mass suitable for the formation of robust solvent-cast films of high gas permeability. 相似文献