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151.
152.
Conner D Jayaprakash KN Wells MB Manzer S Gunnoe TB Boyle PD 《Inorganic chemistry》2003,42(15):4759-4772
The octahedral Ru(II) amine complexes [TpRu(L)(L')(NH(2)R)][OTf] (L = L' = PMe(3), P(OMe)(3) or L = CO and L' = PPh(3); R = H or (t)Bu) have been synthesized and characterized. Deprotonation of the amine complexes [TpRu(L)(L')(NH(3))][OTf] or [TpRu(PMe(3))(2)(NH(2)(t)Bu)][OTf] yields the Ru(II) amido complexes TpRu(L)(L')(NH(2)) and TpRu(PMe(3))(2)(NH(t)Bu). Reactions of the parent amido complexes or TpRu(PMe(3))(2)(NH(t)Bu) with phenylacetylene at room temperature result in immediate deprotonation to form ruthenium-amine/phenylacetylide ion pairs, and heating a benzene solution of the [TpRu(PMe(3))(2)(NH(2)(t)Bu)][PhC(2)] ion pair results in the formation of the Ru(II) phenylacetylide complex TpRu(PMe(3))(2)(C[triple bond]CPh) in >90% yield. The observation that [TpRu(PMe(3))(2)(NH(2)(t)Bu)][PhC(2)] converts to the Ru(II) acetylide with good yield while heating the ion pairs [TpRu(L)(L')(NH(3))][PhC(2)] yields multiple products is attributed to reluctant dissociation of ammonia compared with the (t)butylamine ligand (i.e., different rates for acetylide/amine exchange). These results are consistent with ligand exchange reactions of Ru(II) amine complexes [TpRu(PMe(3))(2)(NH(2)R)][OTf] (R = H or (t)Bu) with acetonitrile. The previously reported phenyl amido complexes TpRuL(2)(NHPh) [L = PMe(3) or P(OMe)(3)] react with 10 equiv of phenylacetylene at elevated temperature to produce Ru(II) acetylide complexes TpRuL(2)(C[triple bond]CPh) in quantitative yields. Kinetic studies indicate that the reaction of TpRu(PMe(3))(2)(NHPh) with phenylacetylene occurs via a pathway that involves TpRu(PMe(3))(2)(OTf) or [TpRu(PMe(3))(2)(NH(2)Ph)][OTf] as catalyst. Reactions of 1,4-cyclohexadiene with the Ru(II) amido complexes TpRu(L)(L')(NH(2)) (L = L' = PMe(3) or L = CO and L' = PPh(3)) or TpRu(PMe(3))(2)(NH(t)Bu) at elevated temperatures result in the formation of benzene and Ru hydride complexes. TpRu(PMe(3))(2)(H), [Tp(PMe(3))(2)Ru[double bond]C[double bond]C(H)Ph][OTf], [Tp(PMe(3))(2)Ru=C(CH(2)Ph)[N(H)Ph]][OTf], and [TpRu(PMe(3))(3)][OTf] have been independently prepared and characterized. Results from solid-state X-ray diffraction studies of the complexes [TpRu(CO)(PPh(3))(NH(3))][OTf], [TpRu(PMe(3))(2)(NH(3))][OTf], and TpRu(CO)(PPh(3))(C[triple bond]CPh) are reported. 相似文献
153.
G. Wells 《Journal of separation science》1983,6(12):651-654
A new design for an electron capture detector cell is described. The cell is compatible with the requirements of high resolution capillary columns and is shown to be useful in applications that require high analysis speed. A unique method of sample introduction reduces the problems of sample loss by adsorption on the surfaces of the cell. Previously reported problems of sample loss by adsorption on active surfaces within the cell when using hydrogen carrier gas are shown to have been eliminated. Examples are shown demonstrating the increased speed of analysis that can be obtained when using hydrogen carrier gas and 100 micron diameter columns. 相似文献
154.
Cecil F. Wells 《Thermochimica Acta》1982,53(1):67-87
The acid dissociation constants of a wide range of acids in water+acetone mixtures have been combined with values for the free energy of transfer of the proton. ΔG0t(H+ to calculate values for the free energy of transfer of ions which derive only from the charge on the ion. ΔG0t(i)c. As the values of ΔG0t(H+) have been revised, revised values for the total free energies of transfer of cations and anions, ΔG0t(M+) and ΔGot(X-), are given. New data for ΔGot(MXn) is also split into values for ΔG0t(Mn+) (where n=1 and 2) and ΔG0t(X?). These free energies of transfer, both total and those deriving from the charge alone, are compared with similar free energies in other mixtures water+co-solvent. Values for ΔGot(i)c do not conform to a Born-type relationship and show the importance of structural effects in the solvent even when only the transfer of the charge is involved. 相似文献
155.
Miller TC Mann G Havrilla GJ Wells CA Warner BP Baker RT 《Journal of combinatorial chemistry》2003,5(3):245-252
A powerful high-throughput screening technique is described for the rapid screening of bead-based libraries for catalyst discovery and molecular recognition. Micro-X-ray fluorescence (MXRF) screens materials for elemental composition with mesoscale analysis. This method is nondestructive and requires minimal sample preparation and no special tags for analysis, and the screening time is dependent on the desired sensitivity. The speed, sensitivity, and simplicity of MXRF as a high-throughput screening technique were applied to screen bead-based libraries of oligopeptides for phosphate hydrolysis catalysts and molecular recognition of selective receptors for the degradation products and analogues of chemical warfare agents. This paper demonstrates the analytical or HTS capability of MXRF for combinatorial screening. It is meant only to show the capabilities of MXRF and is not meant as an exhaustive study of the catalyst and molecular recognition systems presented. 相似文献
156.
Shen Q Wells C Traetteberg M Bohn RK Willis A Knee J 《The Journal of organic chemistry》2001,66(17):5840-5845
Ab initio computational, microwave spectroscopic, and electron diffraction techniques have been used to study the gas-phase structure of cyclopropylbenzene. Theoretical calculations at the HF, B3LYP, and MP2 levels for basis sets 6-31G(d) and 6-311G(d) have been carried out. Both MP2 and B3LYP calculations showed the bisected form to be lower in energy (245/157 and 660/985 cal mol(-1), respectively, for basis sets 6-311G(d)/6-31G(d)). Rotational constants for the bisected form of the parent and eight singly substituted (13)C isotopic species were obtained. The selection rules of the observed rotational transitions and the facts that eight (rather than six) singly substituted (13)C isotopers are observed and assigned and that seven of the compound's nine carbon atoms lie in the molecule's symmetry plane required the molecule to exist in the bisected conformation. No transition from the perpendicular form was observed in the pulsed-jet microwave experiment. Gas-phase electron diffraction data were collected at a nozzle-tip temperature of 265 K. Least squares analyses were carried out using ED data alone and with the inclusion of microwave rotational constants. The principal structural results (r(g) and angle(alpha)) obtained from the combined ED/MW least-squares analysis are r(C-H)(av) = 1.093(6) A, r(C(7)-C(8))(v) = 1.514(20) A, r(C(8)-C(9))(d) = 1.507(26) A, r(C(7)-C(1)) = 1.520(25) A, r(C-C)(Ph) = 1.395(1) A, angleC(1)C(7)C(8) = 119.6(17) degrees, angleC(2)C(1)C(7) = 122.5(25) degrees, angleC(1)C(2)C(3) = 120.9(35) degrees, angleHC(8)C(9) = 116.7(20) degrees, angleHCC(Ph) = 120.0 degrees (assumed). 相似文献
157.
M. Gardner Judith Dobson Brian Miller Colin Allchin David McMullan Trevor Oliver David Wells R. Hudson Richard Toft Mike Jessep 《Accreditation and quality assurance》2002,7(2):60-65
The implementation of a strategy for the assessment of the validity of environmental monitoring data – a ”data filter”– is
described. The approach was developed through the UK National Marine AQC Scheme for application to data collected during the
UK National Marine Monitoring Programme. Data reported for the year 1999, by nine laboratories, for 74 determinand-matrix
combinations were assessed on the basis of the completeness of their supporting quality assurance and quality control information.
The approach to the establishment of criteria of acceptability for quality information is described.
Received: 28 August 2001 Accepted: 29 November 2001 相似文献
158.
The benzylic coupling constants 5Jm and 6Jp for a series of 2-alkyl-3-methoxypyrazines, in which the size of the 2-alkyl group is progressively increased, are reported and discussed. 5Jm remains virtually constant, while 6Jp falls steadily with increasing alkyl group size. These effects are largely attributed to variations in the time-averaged orientation of the benzylic protons and are consistent with the generally accepted mechanisms for meta and para benzylic coupling. The results illustrate the importance of taking conformational aspects into account when attempting to use benzylic coupling constants derived from substituted side-chains in making structural assignments. 相似文献
159.
H. F. Wiebe D. R. Harper L. Holborn F. Henning H. L. Callendar E. H. Griffiths C. W. Waidner G. K. Burgess A. L. Day R. B. Sosman L. H. Adams J. Johnston G. Moeller F. Hoffmann W. Meissner J. G. L. Stern Th. W. Richards R. C. Wells W. Meissner Th. W. Richards F. G. Jackson C. Kellner H. F. Wiebe P. Hebe P. Hebe M. Freund 《Analytical and bioanalytical chemistry》1913,52(5):304-308
160.