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111.
Holger Lang Margarete Gottlieb Michael Schwarz Silke Farkas BerndS. Schulz Frank Himmelsbach Ramamurthy Charubala Wolfgang Pfleiderer 《Helvetica chimica acta》1999,82(12):2172-2185
A series of new base-protected and 5′-O-(4-monomethoxytrityl)- or 5′-O-(4,4′-dimethoxytrityl)-substituted 3′-(2-cyanoethyl diisopropylphosphoramidites) and 3′-[2-(4-nitrophenyl)ethyl diisopropylphosphoramidites] 52 – 66 and 67 – 82 , respectively, are prepared as potential building blocks for oligonucleotide synthesis (see Scheme). Thus, 3′,5′-di-O-acyl- and N 2,3′-O,5′-O-triacyl-2′-deoxyguanosines can easily be converted into the corresponding O6-alkyl derivatives 6 , 8 , 10 , 12 , 14 , and 16 by a Mitsunobu reaction using the appropriate alcohol. Mild hydrolysis removes the acyl groups from the sugar moiety (→ 9 , 11 , 13 , 15 , and 19 (via 18 ), resp.) which can then be tritylated (→ 38 – 42 ) and phosphitylated (→ 57 – 61 ) in the usual manner. N 2-[2-(4-nitrophenyl)ethoxycarbonyl]-substituted and N 2-[2-(4-nitrophenyl)ethoxycarbonyl]-O6-[2-(4-nitrophenyl)ethyl]-substituted 2′-deoxyguanosines 5 and 7 , respectively, are synthesized as new starting materials for tritylation (→ 28 , 35 , and 37 ) and phosphitylation (→ 54 , 56 , 70 , and 78 ). Various O4-alkylthymidines (see 20 – 24 ) are also converted to their 5′-O-dimethoxytrityl derivatives (see 43 – 47) and the corresponding phosphoramidites (see 62 – 66 and 79 – 82 ). 相似文献
112.
Yu-Ming ZHENG Hong-Min LIU Ben-Hao SA Zhong-Dao LU Zhong-Qi WANG Xiao-Ze ZHANG 《理论物理通讯》1993,19(1):71-74
A simple Monte Carlo simulation and even a partition method can be used to reproduce quite well the power law behavior between the factorial moment and the charge interval of fragment charge distributions from the multifragmentation of 197Au nucleus bombarding emulsion at~1 GeV/nucleon. This indicates that the above power law seems not to be a unique precursor of the intermittent behavior in nuclear multifragmentations. 相似文献
113.
Following the method developed by the authors,recently,the equation of state of hot nuclei(238U in concrete) before break-up was investigated numerically.The isotherms are drawn in the plan of the general pressure P versus volume VRT. They are similar to those of Van der Waals gas.The critical temperature of phase transition should correspond to the isotherm with one turning point only.It turns out that the data of mass yield distribution can be reproduced by many pairs of parameters T and VRT (freeze-out temperature and freeze-out volume) varying in certain range.For each isotherm (each T),the data are always best reproduced by the value of VRT located at the maximum general pressure within two phases coexistence region. 相似文献
114.
115.
116.
Steven Gottlieb Paul B. Mackenzie H.B. Thacker Don Weingarten 《Physics letters. [Part B]》1984,134(5):346-350
We present a method for studying hadronic transitions in lattice gauge theory which requires computer time comparable to that required by recent hadron spectrum calculations. This method is applied to a calculation of the decay ?→ππ. 相似文献
117.
Zafrani Y Gottlieb HE Sprecher M Braverman S 《The Journal of organic chemistry》2005,70(24):10166-10168
[reaction: see text] In a recent article, we reported on the base-catalyzed rearrangements of dipropargyl selenides, -sulfides, -sulfoxides, and -sulfones that eventually lead to polycyclic aromatic products. In the present work, we report on the first isolation and characterization of the thiophene dioxide intermediates 5b,c from a mild tandem isomerization/cyclization/aromatization of bis(pi-conjugated propargyl) sulfones. Monoallene 2b,c and diallene 3b intermediates were also identified by NMR. A kinetic study of the rearrangement of 1a-c revealed that the unusual facile tandem process is highly dependent on the nature of gamma-substitution. 相似文献
118.
Aubin C Bernard C Detar C Dipierro M El-Khadra A Gottlieb S Gregory EB Heller UM Hetrick J Kronfeld AS Mackenzie PB Menscher D Nobes M Okamoto M Oktay MB Osborn J Simone J Sugar R Toussaint D Trottier HD;Fermilab Lattice;MILC;HPQCD 《Physical review letters》2005,94(1):011601
We present the first three-flavor lattice QCD calculations for D-->pilnu and D-->Klnu semileptonic decays. Simulations are carried out using ensembles of unquenched gauge fields generated by the MILC Collaboration. With an improved staggered action for light quarks, we are able to simulate at light quark masses down to 1/8 of the strange mass. Consequently, the systematic error from the chiral extrapolation is much smaller than in previous calculations with Wilson-type light quarks. Our results for the form factors at q(2)=0 are f(D-->pi)(+)(0)=0.64(3)(6) and f(D-->K)(+)(0)=0.73(3)(7), where the first error is statistical and the second is systematic, added in quadrature. Combining our results with experimental branching ratios, we obtain the Cabibbo-Kobayashi-Maskawa matrix elements |V(cd)|=0.239(10)(24)(20) and |V(cs)|=0.969(39)(94)(24), where the last errors are from experimental uncertainties. 相似文献
119.
The crystal structures of T?3PSe4 and T?3AsS4 have been determined by x-ray diffraction techniques. These isomorphous materials are layered, with orthorhombic Pcmn symmetry. Ultrasonic measurements have shown that the shear mode velocity is anomalously low for both materials. Measurements at high pressure on T?3PSe4 have shown that the anomalous shear velocity softens to zero at 1.40 ± 0.01 GPa, indicating a second- order structural transition at that pressure. 相似文献
120.
This paper considers the simultaneous solution of the matrix equations AH + HA1 = A1H + HA = I, where H is Hermitian. A full characterization of A in terms of a given H is obtained. Various results are also obtained for those H satisfying the equations with a given A. 相似文献