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831.
832.
Ilia A. Dereven'kov Sergei V. Makarov Pavel A. Molodtsov Anna S. Makarova 《国际化学动力学杂志》2021,53(1):146-153
Selenocysteine (Sec) is a crucial component of mammalian thioredoxin reductase (TrxR) where it serves as a nucleophile for disulfide bond rupture in thioredoxin (Trx). Generation of the reduced state of Sec in TrxR requires consecutive two electron transfer steps, namely: (i) from NADPH to flavin adenine dinucleotide, (ii) from reduced flavin to the disulfide bond Cys59‐S‐S‐Cys64, and finally (iii) from Cys59 and Cys64 to the selenosulfide bond Cys497‐S‐Se‐Sec498. In this work, we studied the reaction between reduced riboflavin (RibH2) and selenocystine (Sec‐Sec), an oxidized form of Sec. The interaction between RibH2 and Sec‐Sec proceeded relatively slowly in comparison with its reverse reaction, that is, reduction of riboflavin (Rib) by Sec. The rate constant for the reaction between RibH2 and Sec‐Sec was (7.9 ± 0.1) × 10?2 M?1 s?1 (pH 7.0, 25.0°C). The reaction between Rib and Sec proceeded via two steps, namely, a rapid reversible binding of Rib to Sec having a protonated selenol group to form a Sec‐Rib complex, followed by nucleophilic attack of Sec‐Rib by a second Sec molecule harboring a deprotonated selenol group. The equilibrium constant for the overall reduction process of Rib by Sec is (1.2 ± 0.1) × 106 M?1 (25.0°C). The finding that the interaction of RibH2 with oxidized selenol is reversible with its equilibrium favored toward the reverse reaction provides an additional explanation for the exceptional mechanism of the mammalian Trx/TrxR system involving transient reduction of a disulfide bond. 相似文献
833.
The partial representation extension problem is a recently introduced generalization of the recognition problem. A circle graph is an intersection graph of chords of a circle. We study the partial representation extension problem for circle graphs, where the input consists of a graph and a partial representation giving some predrawn chords that represent an induced subgraph of . The question is whether one can extend to a representation of the entire graph , that is, whether one can draw the remaining chords into a partially predrawn representation to obtain a representation of . Our main result is an time algorithm for partial representation extension of circle graphs, where is the number of vertices. To show this, we describe the structure of all representations of a circle graph using split decomposition. This can be of independent interest. 相似文献
834.
835.
836.
Benjamín Mallada Qifan Chen Dr. Taras Chutora Dr. Ana Sánchez-Grande Dr. Borja Cirera Dr. José Santos Prof. Nazario Martín Dr. David Ecija Dr. Pavel Jelínek Dr. Bruno de la Torre 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(48):e202200944
Atomic scale defects significantly affect the mechanical, electronic, and optical properties of π-conjugated polymers. Here, isolated atomic-scale defects are deliberately introduced into a prototypical anthracene-ethynylene π-conjugated polymer, and its local density of states is carefully examined on the atomic scale to show how individual defects modify the inherent electronic and magnetic properties of this one-dimensional systems. Scanning tunneling and atomic force microscopy experiments, supplemented with density functional theory calculations, reveal the existence of a sharp electronic resonance at the Fermi energy around certain defects, which is associated with the formation of a local magnetic moment accompanied by substantial mitigation of the mobility of charge carriers. While defects in traditionally synthesized polymers lead to arbitrary conformations, the presented results clearly reflect the preferential formation of low dimensional defects at specific polymer sites, which may introduce the possibility of engineering macroscopic defects in surface-synthesized conjugated polymers. 相似文献
837.
Vladislav Y. Korotaev Vyacheslav Y. Sosnovskikh Alexey Y. Barkov Pavel A. Slepukhin Yurii V. Shklyaev 《Journal of heterocyclic chemistry》2012,49(4):856-860
Uncatalyzed cycloaddition of 3,4‐dihydroisoquinolines to (E)‐1,1,1‐trifluoro‐3‐nitro‐2‐butene via Grob reaction provide a simple one‐step route to the 5,6‐dihydropyrrolo[2,1‐a]isoquinolines, which represent the basic structural framework of the antitumor active alkaloid crispine. 相似文献
838.
Pavel Shumyatsky 《Israel Journal of Mathematics》2013,194(2):895-906
Let e be a positive integer and G a finite group acted on by the four-group V in such a manner that C G (V) = 1. Suppose that V contains an element v such that the centralizer C G (v) has exponent e. Then the exponent of G″, the second derived group of G, is bounded in terms of e only. 相似文献
839.
840.