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91.
Arne Hole 《International Journal of Theoretical Physics》1994,33(5):1085-1111
A mathematical model for the general notion of a deterministic physical theory is introduced, and incompleteness results analogous to the halting theorem for Turing machines are demonstrated for this model. The discussion is not limited to algorithmic systems. 相似文献
92.
93.
We continue the study of the linear complexity of binary sequences, independently introduced by Sidel’nikov and Lempel, Cohn,
and Eastman. These investigations were originated by Helleseth and Yang and extended by Kyureghyan and Pott. We determine
the exact linear complexity of several families of these sequences using well-known results on cyclotomic numbers. Moreover,
we prove a general lower bound on the linear complexity profile for all of these sequences. 相似文献
94.
95.
The adsorption of methanol in zeolites of the faujasite type with sodium and calcium counter ions is studied with quantum chemical methods. The zeolite is represented with a cluster model allowing calculations at the Møller-Plesset as well as the DFT level of theory. An adsorption energy of −62.4 kJ/mol is calculated at the MP2/TZVP//BP86/TZVP level of theory for one methanol molecule at one site II sodium cation. Insight into the adsorption process is obtained with a three-body decomposition which reveals a strong destabilisation of the adsorption strength by large, positive three-body terms, which is important for force field development. 相似文献
96.
Asymmetric Synthesis of Fully Substituted Cyclopentane‐Oxindoles through an Organocatalytic Triple Michael Domino Reaction 下载免费PDF全文
Dr. Liang‐Hua Zou Arne R. Philipps Prof. Dr. Gerhard Raabe Prof. Dr. Dieter Enders 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(3):1004-1008
An efficient, highly stereoselective asymmetric synthesis of fully functionalized cyclopentanes bearing an oxindole moiety and several other functional groups in one pot has been developed. Key step is an organocatalytic triple Michael domino reaction forming three C?C bonds and six stereocenters, including a quaternary one. Starting from equimolar amounts of simple substrates, a high molecular complexity can be reached after a Wittig olefination in one pot. The new protocol can easily be scaled up to gram amounts. 相似文献
97.
Mohammed A. K. Ahmed Helmer Fjellvåg Prof. Dr. Arne Kjekshus David S. Wragg Nalinava Sen Gupta 《无机化学与普通化学杂志》2011,637(1):56-61
The mixed‐ligand complex [Cr(thd)2(OEt)]2 [(thd)– = anion of H(thd) = C11H20O2 = 2,2,6,6‐tetramethylheptane‐3,5‐dione] appears as by‐product when EtOH/H2O is used as solvent during preparation of Cr(thd)3. [Cr(thd)2(OEt)]2 can be difficult to separate from Cr(thd)3 by sublimation, but separation is easily accomplished by extracting Cr(thd)3 with acetone. A detailed account for the sublimation behavior of [Cr(thd)2(OEt)]2/Cr(thd)3 mixtures is advanced. Good yields of [Cr(thd)2(OEt)]2 are obtained when CrCl3, H(thd), and Na(EtO) react in absolute EtOH. [Cr(thd)2(OEt)]2 is obtained in the form of green needle‐shaped crystals by recrystallization from toluene. The crystal structure is triclinic [a = 10.2919(15), b = 10.6686(16), c = 14.194(3) Å, α = 106.559(2), β = 107.869(2), and γ = 98.326(2)° at 295 K; space group P . The complex contains two crystallographic equivalent chromium atoms, which are bridged by two cis‐configured ethoxy groups, the four remaining sites in the octahedral coordination around each chromium atom being occupied by oxygen atoms from two thd ligands. The bond lengths and angles concur with the findings for related molecular complexes. The temperature dependence of the magnetic susceptibility of [Cr(thd)2(OEt)]2 follows Curie–Weiss law with Weiss constant θ ≈? –65 K and μp = 3.87 μB. 相似文献
98.
Dieckmann A Beniken S Lorenz CD Doltsinis NL von Kiedrowski G 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(2):468-480
We have investigated a diastereoselective self‐replicating system based on a cycloaddition of a fulvene derivative and a maleimide using a two‐pronged approach of combining NMR spectroscopy with computational modelling. Two diastereomers are formed with identical rates in the absence of replication. When replication is enabled, one diastereomer takes over the resources as a “selfish” autocatalyst, while exploiting the competitor as a weak “altruist”, resulting in a diastereoselectivity of 16:1. We applied 1D and 2D NMR spectroscopic techniques supported by ab initio chemical shifts as well as ab initio molecular dynamics simulations to study the structure and dynamics of the underlying network. This powerful combination allowed us to decipher the energetic and structural rationale behind the observed behaviour, while static computational methods currently used in the field did not. 相似文献
99.
100.
Xiao-Lei Li Lang Zhao Jianfeng Wu Wei Shi Niklas Struch Arne Lützen Annie K. Powell Peng Cheng Jinkui Tang 《Chemical science》2022,13(34):10048
In situ metal-templated (hydrazone) condensation also called subcomponent self-assembly of 4,6-dihydrazino-pyrimidine, o-vanillin and dysprosium ions resulted in the formation of discrete hexa- or dodecanuclear metallosupramolecular Dy6(L)6 or Dy12(L)8 aggregates resulting from second-order template effects of the base and the lanthanide counterions used in these processes. XRD analysis revealed unique circular helical or tetragonal bipyramid architectures in which the bis(hydrazone) ligand L adopts different conformations and shows remarkable differences in its mode of metal coordination. While a molecule of trimethylamine acts as a secondary template that fills the void of the Dy6(L)6 assembly, sodium ions take on this role for the formation of heterobimetallic Dy12(L)8 by occupying vacant coordination sites, thus demonstrating that these processes can be steered in different directions upon subtle changes of reaction conditions. Furthermore, Dy6(L)6 shows an interesting spin-relaxation energy barrier of 435 K, which is amongst the largest values within multinuclear lanthanide single-molecular magnets.Subcomponent self-assembly gave access to Dy12(L)8 and Dy6(L)6 architectures via second-order template effects. The Dy6(L)6 assembly behaves as a single-molecule magnet exhibiting a high anisotropy barrier and butterfly-shaped magnetic hysteresis. 相似文献