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891.
892.
K. P. Butin A. A. Moiseeva T. V. Magdesieva E. V. Sergeeva V. I. Rozenberg V. G. Kharitonov 《Russian Chemical Bulletin》1994,43(5):783-789
The potentials of electrochemical oxidation (
) and reduction (
) of monobromo- and isomeric di- and tribromo[2.2]paracyclophanes as well as
of mono-, di-, and tribromobenzenes were measured in acetonitrile. The similarity between the properties ofpseudo-para-disubstituted cyclophanes andmeta-disubstituted benzenes, on the one hand, andpseudo-meta-disubstituted cyclophanes andpara-disubstituted benzenes, on the other hand, was confirmed by the existence of a linear relationship between
of bromo-substituted [2.2]paracyclophanes and
of the corresponding bromo-substituted benzenes. The results were explained in terms of the qualitative theory of molecular orbitals, taking into account a through space interaction between the -systems of the benzene rings.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 839–845, May, 1994.The authors wish to express their gratitude to Professor R. Hoffmann (Cornell University, USA) for a useful discussion and criticisms of the text of this paper.This work was financially supported by the Russian Foundation for Basic Research (Project 93-03-5246). 相似文献
893.
894.
报道了5种N-芳基芴亚胺在酸性条件下被烟酰胺辅酶模型(Hantzsch酯,BNAH)还原的反应。结果表明:亚胺的结构、酸的强度以及溶剂的不同均会影响亚胺的还原效率,本文结合反应的结构效应、溶剂效应和同位素效应,对其可能的酸催化氢负离子转移机理进行了讨论。 相似文献
895.
Ramasamy、Osuka等用NaHTe/EtOH研究了二卤代物的脱邻二溴、偕二溴反应和α-溴代羰基化合物的脱卤还原反应,我们选择结构不同的卤代物以NaHTe还原,发现在水介质和催化量碲代替计算量碲时也能顺利地进行这类反应,其反应条件温和,产率高,是有机官能团转化的好方法。 相似文献
896.
NO dissociation and subsequent N2 production in the presence of co-adsorbed S18O2 and D2 on the surface of stepped Pt(3 3 2) were studied using Fourier transform infra red reflection–absorption spectroscopy (FTIR-RAS) combined with thermal desorption spectroscopy (TDS). Reduction of NO by D (D2 is adsorbed dissociatively on Pt surfaces) proceeds to a limited extent, because this reaction is rate-controlled by NO dissociation and the supply of D atoms at the higher surface temperatures at which NO dissociation becomes significant (350 K and higher). NO–D reaction is suppressed in the presence of S18O2, depending significantly on the S18O2 coverage and the competition between the reactions NO–D and S18O2–D. When the supply of D2 is limited, e.g., 0.1 L in this study, the presence of S18O2 suppresses the NO–D reaction. With a sufficient supply of D2, e.g., 0.4 L and higher, D-atom competing reactions do not play a role any more because the reactions of both NO and S18O2 with D proceed only to a very limited extent. As such, generation of O atoms from S18O2 dissociation is the main reaction that leads to the suppression in NO dissociation and consequently, N2 production.It is also concluded that the presence of S18O2 does not seriously poison the active sites on the Pt surface, providing that there is a sufficient D supply to remove O atoms from both NO dissociation and S18O2 dissociation. 相似文献
897.
《Applied Mathematical Modelling》2014,38(15-16):3987-4005
In this study, we reduce the uncertainty embedded in secondary possibility distribution of a type-2 fuzzy variable by fuzzy integral, and apply the proposed reduction method to p-hub center problem, which is a nonlinear optimization problem due to the existence of integer decision variables. In order to optimize p-hub center problem, this paper develops a robust optimization method to describe travel times by employing parametric possibility distributions. We first derive the parametric possibility distributions of reduced fuzzy variables. After that, we apply the reduction methods to p-hub center problem and develop a new generalized value-at-risk (VaR) p-hub center problem, in which the travel times are characterized by parametric possibility distributions. Under mild assumptions, we turn the original fuzzy p-hub center problem into its equivalent parametric mixed-integer programming problems. So, we can solve the equivalent parametric mixed-integer programming problems by general-purpose optimization software. Finally, some numerical experiments are performed to demonstrate the new modeling idea and the efficiency of the proposed solution methods. 相似文献
898.
化石燃料的燃烧和其他人类活动排放了大量的CO2气体,引发了诸多环境问题。电催化CO2还原反应(CO2RR)可以储存间歇可再生能源,实现人为闭合碳循环,被认为是获得高附加值化学品和燃料的有效途径。电催化CO2RR涉及多个电子-质子转移步骤,其中*CO通常被认为是关键中间体。铜由于对*CO具有合适的吸附能,已被广泛证明是唯一能够有效地将CO2还原为碳氢化合物和含氧化合物的金属催化剂。然而,纯Cu稳定性差、产品选择性低、过电位高,阻碍了工业级多碳产品的生产。构筑Cu基串联催化剂是提高CO2RR性能的一种有前途的策略。本文首先介绍电催化CO2RR的反应路线和串联机理。然后,系统地总结铜基串联催化剂对电催化CO2RR的最新研究进展。最后,提出合理设计和可控合成新型电催化CO2RR串联催化剂面临的挑战和机遇。 相似文献
899.
A LOI-RCCE methodology for reducing chemical kinetics, with application to laminar premixed flames 总被引:1,自引:0,他引:1
A framework for automated development of reduced mechanisms is presented by combining the methodologies of level of importance (LOI) and rate-controlled constrained equilibrium (RCCE). It is shown that these methods are complimentary, as they deal with different aspects of the overall reduction problem: LOI is a method of determining the species governed by fast/slow scales, while RCCE is a physical model that yields ODEs that describe the reduced model for a given selection. The potential for the synergy of the two methods is demonstrated by reducing a comprehensive mechanism for propane combustion (117 species, 665 reactions) and applying the reduced mechanism to the problem of 1-D laminar flame propagation. Results show that RCCE yields substantial CPU gainings, while predicting the major species as well as important minor species (such as radicals and C2H2) with sufficient accuracy. 相似文献
900.
影响超稠油油藏水平井蒸汽吞吐开发效果的因素包括地质参数、流体参数、开发参数、水平井设计参数等众多因素,寻找主要因素对于超稠油油藏水平井吞吐效果评价及开发调整设计具有重要意义.基于粗糙集理论对影响超稠油油藏水平井吞吐效果的10个因素进行数据属性约简,同时利用灰色关联分析,对这些因素进行敏感性分析;应用Elman神经网络比较上述两种结果,证明了粗糙集理论进行数据属性约简的方法更准确.最终得到注汽干度、注汽强度、注汽速度、水平段长度和注汽压力对水平井的开发效果影响最大.实例计算表明,方法实用有效,精度较高,可用于超稠油油藏水平井吞吐效果评价及开发、调整设计. 相似文献