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151.
Lenard Hanf Jonas Henschel Marcel Diehl Martin Winter Sascha Nowak 《Electrophoresis》2020,41(9):697-704
A new CE method with ultraviolet–visible detection was developed in this study to investigate manganese dissolution in lithium ion battery electrolytes. The aqueous running buffer based on diphosphate showed excellent stabilization of labile Mn3+, even under electrophoretic conditions. The method was optimized regarding the concentration of diphosphate and modifier to obtain suitable signals for quantification. Additionally, the finally obtained method was applied on carbonate-based electrolytes samples. Dissolution experiments of the cathode material LiNi0.5Mn1.5O4 (lithium nickel manganese oxide [LNMO]) in aqueous diphosphate buffer at defined pH were performed to investigate the effect of a transition metal-ion-scavenger on the oxidation state of dissolved manganese. Quantification of both Mn species revealed the formation of mainly Mn3+, which can be attributed to a comproportionation reaction of dissolved and complexed Mn2+ with Mn4+ at the surface of the LNMO structure. It was also shown that the formation of Mn3+ increased with lower pH. In contrast, dissolution experiments of LNMO in carbonate-based electrolytes containing LIPF6 showed only dissolution of Mn2+. 相似文献
152.
以高含氮量的苯胺五聚体二羧酸为配体, 在预氧化的泡沫镍上通过溶剂热反应合成了Fe, Co金属有机框架材料Fe/Co-MOF, 再以Fe/Co-MOF为金属源和碳源, 经磷化后制备出一种新型的双金属(Fe, Co)和杂原子(N, P)共掺杂的碳材料Fe/Co/P-NPs. 通过扫描电子显微镜和高分辨透射电子显微镜表征发现, Fe/Co/P-NPs由纳米粒子和纳米片组成, 并且形成Fe2P和Co2P两种晶体. 电化学测试结果表明, Fe/Co/P-NPs在析氢、 析氧及水电解中表现出了优异的多功能催化活性. 在1 mol/L KOH中, Fe/Co/P-NPs在10和100 mA/cm 2电流密度时的析氧过电位分别为270和300 mV, 均小于其它对比材料, 优于负载在泡沫镍上的RuO2. 作为水电解双功能催化剂, Fe/Co/P-NPs仅需1.48 V的电位即可获得10 mA/cm 2的电流密度. 相似文献
153.
This work reports the ambient temperature synthesis and structural characterization of six new first row transition metal acetylenedicarboxylate coordination polymers. The Co and two Ni compounds adopt structures in which the octahedral metals are connected into 1D chains via the acetylenedicarboxylate ligand. In contrast the Mn and two Zn compounds adopt 3D metal-organic frameworks; while the Mn compound is non-porous the two Zn structures contain dimeric or trimeric clusters connected into frameworks that are potentially porous. These two anionic metal-organic frameworks are, however, charged balanced by cations siting in their pores which greatly reduces the ability to access their porosity. 相似文献
154.
在非均相催化加氢反应中,氢气(H2)一直被公认为是通过两步基元步骤参加还原反应的,包括第一步的分子解离和之后的反应物与原子氢键合,即所谓的Horiuti-Polanyi(HP)机理.直到我们研究组在Ag或Au催化丙烯醛加氢还原反应理论研究中发现非HP机理加氢路径存在时,新的机理才被提出,并引起广大研究者的浓厚兴趣.考虑到表面羟基(OH)和氧(O)在非均相催化体系中广泛存在,如常见的过渡金属催化的费托合成、甲烷重整、水汽转化及氨氧化等反应,基于第一性原理的密度泛函理论计算方法,我们对OH/O在一系列过渡金属催化作用下还原生成水的微观机理进行了系统全面的探究.研究发现,不同金属对应于不同的催化氢化反应活性,以及不同的催化反应机理.在某些金属上H2以分子形式进攻反应物种的非HP机理有利,而在其它金属上经典的H2解离后参与氢化还原反应的HP机理更容易发生.详细分析显示, H2的解离活性决定了反应机理的种类:在对H2解离具有催化活性的金属(如Pt、Ni)表面,不论是(211)台阶面还是(111)平面, H2解离几乎都是无能垒过程,且伴随氢原子的强吸附,反应放热明显,导致活泼金属上HP机理更容易发生;与之相反,在不活泼的催化剂表面, H2解离很难发生,原子吸附也相当微弱,相比于断键裂解, H2更倾向于发生分子氢化的非HP机理.另外,本文还定义了一个新的结构描述符(η)来帮助理解两种机理发生的结构因素差异.η是衡量分子氢化过渡态结构(TS)中H–H键解离程度的参数,根据其定义上下限数值分别设定为H2在各催化剂表面解离过渡态的键长(Ddis)和游离分子态的键长(DH2).结果显示,易发生非HP机理的催化剂表面的TS结构对应的η参数普遍低于0.4,即H–H原子对的确是以近分子形式参与氢化反应;相反发生经典HP机理的催化剂表面,η参数普遍在0.5–0.8,即H–H即使以分子形式参与反应也是处于近解离状态,这预示了以解离吸附氢参与反应的优选性. 相似文献
155.
一氧化碳是发展可持续化学经济的重要原料。人们希望能够将一氧化碳催化转变成高附加值化学品,从而减少石油等化石资源对人类的束缚。研究均相金属配合物与一氧化碳的反应能够使人们了解一氧化碳转变及利用机理,并开发新催化剂高效地利用一氧化碳资源。本文从金属配合物与一氧化碳反应的活性点出发,分别讨论不同类型的金属配合物与一氧化碳的反应,以求让人们在分子水平上了解一氧化碳的基本反应原理;并总结了该领域存在的难点问题,展望了未来,希望更多的科研工作者投入其中,从而实现利用一氧化碳合成出各种各样的化学品和材料。 相似文献
156.
《中国化学快报》2020,31(9):2177-2188
In the past few years, the increasing energy consumption of traditional fossil fuels has posed a huge threat to human health. It is very imperious to develop the sustainable and renewable energy storage and conversion devices with low cost and environment friendly features. Hybrid supercapacitors are emerging as one of the promising energy devices with high power density, fast charge-discharge process and excellent cycle stability. However, morphology and structure of the electrode materials exert serious effect on their electrochemical performances. In this review, we summarized recent progresses in transition metal oxide based electrode materials for supercapacitors. Different synthesis routes and electrochemical performances of electrode materials and storage mechanisms of supercapacitor devices have been presented in details. The future developing trends of supercapacitor based on metal oxide electrode materials are also proposed. 相似文献
157.
《中国化学快报》2020,31(9):2330-2332
By integrating the merits of lanthanide elements and quantum dots, we firstly design CeO2 quantum dots doped Ni-Co hydroxide nanosheet via a controllable synthetic strategy, which exhibits a large specific capacitance (1370.7 F/g at 1.0 A/g) and a good cyclic stability (90.6% retention after 4000 cycles). Moreover, we assemble an aqueous asymmetric supercapacitor with the obtained material, which has an extremely high energy density (108.9 Wh/kg at 378 W/kg) and outstanding cycle stability (retaining 88.1% capacitance at 2.0 A/g after 4000 cycles). 相似文献
158.
DONG Wenfei CHEN Xiaoyu PENG Juan LIU Wanyi JIN Xiaoyong NI Gang LIU Zheng 《高等学校化学研究》2020,36(4):648-661
Ammonia is a commodity chemical with high added value. Electrochemical reduction of nitrogen has great promise for the sustainable synthesis of ammonia in recent years. Because of its rich resources and unique electronic structure and characteristics, 2D transition metal compounds have been used as electrocatalysts for electrochemical reduction of nitrogen for clean and sustainable production of ammonia. This review outlines the latest development in the use of 2D transition metal compounds as high-efficiency electrocatalysts for nitrogen reduction reaction(NRR). First, we introduce the N2 reduction mechanism, and briefly summarize the performance indicators of the catalyst. Then, we focused on the functionalization of unique 2D materials to design high-performance 2D electrocatalysts in respect of simulation calculation and experimental development. Finally, the current challenges and future opportunities for NRR electrocatalysts are introduced. 相似文献
159.
Lin Zhang Ivan Merino-Garcia Jonathan Albo Carlos M. Sánchez-Sánchez 《Current Opinion in Electrochemistry》2020
The electrochemical CO2 reduction reaction (CO2RR) either to generate multicarbon (C2+) or single carbon (C1) value-added products provides an effective and promising approach to mitigate the high CO2 concentration in the atmosphere and promote energy storage. However, cost-effectiveness of catalytic materials limits practical application of this technology in the short term. Herein, we summarize and discuss recent and advanced works on cost-effective oxide-derived copper catalysts for the generation of C2+ products (hydrocarbons and alcohols) and transition metal–nitrogen–doped carbon electrocatalytic materials for C1 compounds production from CO2RR. We think they represent suitable electrocatalyst candidates for scaling up electrochemical CO2 conversion. This short review may provide inspiration for the future design and development of innovative active, cost-effective, selective and stable electrocatalysts with improved properties for either the production of C2+ (alcohols, hydrocarbons) or carbon monoxide from CO2RR. 相似文献
160.
The molecular structures of indazole and 3-halogeno-indazole tautomers were calculated by the B3LYP method at the 6-311G** level, both in the gaseous and aqueous phases, with full geometry optimization.The geometry and electronic structure of the tautomers of indazole, 3-halogeno-indazole and their transition states were obtained. The Onsager solvate theory model was employed for the aqueous solution calculations.The results of the calculation indicated that the N1-H form of the studied molecule is more stable than that of the N2-H form. The influences of the different 3-halogeno and solvent effects on the geometry, energy,charge and activation energy were discussed. The reaction mechanism of the tautomerization of indazole and 3-halogeno-indazole was also studied and a three-membered cyclic transition state of the tautomer reaction has been obtained. 相似文献