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991.
本文设计了一种具有准全向吸波特性的平板超材料吸波体,其准全向吸波特性是由超材料吸波单元的双面吸波、极化不敏感和宽入射角实现的.理论分析和仿真结果表明:该吸波体在6.18 GHz的确有一个双面吸波的吸收点,且吸收率对极化角和入射角均不敏感.提取的等效阻抗表明可以调节超材料的电磁响应使其在吸收频率处与自由空间阻抗匹配来抑制反射.仿真的能量损耗分布表明:该吸波体对电磁波的吸收主要源于基板的介质损耗;采用两种不同介质基板的设计可使前吸波体与后吸波体的耦合度明显降低、抑制耦合所导致的传输.该吸波体可能在许多领域具有
关键词:
准全向吸波
双面吸波
极化不敏感
宽入射角 相似文献
992.
Single‐electron oxidation of a diiron‐sulfur complex [Cp*Fe(μ‐bdt)FeCp*] ( 1 , Cp*=η5‐C5Me5; bdt=benzene‐1,2‐dithiolate) to [Cp*Fe(μ‐bdt)FeCp*]+ ( 2 ) has been experimentally conducted. The bdt ligand with redox‐active character has been computationally proposed to be a dianion (bdt2?) rather than previously proposed monoanion (bdt·?) radical in 1 though it has un‐equidistant aromatic C? C bond lengths. The ground state of 1 is predicted to be two low‐spin ferrous ions (SFe=0) and 2 has a medium‐spin ferric ion (SFe=1/2) and a low‐spin ferrous center (SFe=0), and the oxidation of 1 to 2 is calculated to be a single‐metal‐based process. Both complexes have no significant antiferromagnetic coupling character. 相似文献
993.
994.
In this paper, the separation and determination of the sweetener aspartame by ion chromatography coupled with electrochemical amperometric detection is reported. Sodium saccharin, acesulfame-K and aspartame were separated using 27.5 mmol/l NaOH isocratic elution on a Dionex IonPac AS4A-SC separation column. Aspartame can be determined by integrated amperometric detection without interference from the other two sweeteners. The method can be applied to the determination of aspartame in powered tabletop, fruit juice and carbonated beverage samples, and the results obtained by integrated amperometry were in agreement with those obtained using a UV detection method. A method for determining analytes with an NH2 group by ion chromatography with integrated amperometry was developed. 相似文献
995.
Hou Chen Lingfang Chen Chunhua Wang Rongjun Qu 《Journal of polymer science. Part A, Polymer chemistry》2011,49(4):1046-1049
Atom transfer radical polymerization using activators regenerated by electron transfer (ARGET ATRP) of acrylonitrile (AN) was first approached with 1‐(1‐ethoxycarbonylethyl)‐3‐methylimidazolium tetrafluoroborate ([ecemim][BF4]) as reaction medium and tin(II) bis(2‐ethylhexanoate) (Sn(EH)2) as reducing agent in the presence of air. When compared with in bulk, an obvious increase of polymer isotacticity was observed for ARGET ATRP of AN in 1‐(1‐ethoxycarbonylethyl)‐3‐methylimidazolium hexafluorophospate ([ecemim][PF6]), the reaction rate of ARGET ATRP of AN in [ecemim][PF6] was higher and the polymerization process was better controlled. The block copolymer polyacrylonitrile‐block‐poly(methyl methacrylate) with molecular weight at 69,750, distribution at 1.34, and isotacticity at 0.36 was successfully obtained in [ecemim][PF6]. [Ecemim][PF6] and the catalyst system were recycled and reused and had no effect on the living nature of polymerization. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
996.
To get deep insights into the structure–reactivity relationship for ring‐opening oligomerization reactions toward targeted design of novel main‐chain boron‐containing materials, detailed DFT B97D/TZVP calculations are carried out to compare the ring‐opening oligomerization of both unsubstituted and tert‐butyl (tBu)‐substituted 9H?9‐borafluorenes. In contrast to substituent exchange between normal boranes, such reactions are initiated by substituent exchanges involving double B? C? B bridged intermediates. On tBu‐substitution, the B? C? B, and B? H? B bridged dimer intermediate is stabilized mainly due to enhanced barrier of 18.1 kcal/mol toward further trimerization channel and higher isomerization barrier of 22.5 kcal/mol toward the double B? H? B bridged dimer. In good agreement with available experiments, it is clearly shown that various product channels can be efficiently controlled by bulky substitution and by reaction temperatures, pointing out the way toward desired higher oligomers with improved thermal stability. © 2014 Wiley Periodicals, Inc. 相似文献
997.
配位化合物中不少先前被认为是简单的1∶1配合物,而实际上却是多核配合物,原因是它们的组成比相同,都是1,因而多核配合物的存在不易被发现目前已有数种方法可以识别并可测定其稳定常数,如图解偿试法,但计算较繁琐本文基于直接测定配合物吸光度建立一种新的图解法,不需通过偿试而后测定多核配合物组成和稳定常数,实验与计算均较简单,试用于Fe(Ⅲ)ECR或CAS体系,获得了满意的结果 相似文献
998.
吲哚基丁烯酮缩氨基硫脲配合物的合成及生物活性 总被引:3,自引:1,他引:3
缩氨基硫脲类Schiff碱化合物因具有显著的抗菌和抗肿瘤等活性而受到广泛关注,研究发现很多这类化合物与金属离子形成配合物以后,生物活性明显增强。例如,3-乙氧基-2-氧代丁醛双缩氨基硫脲(H2KTs)单独用于治疗大鼠腹水癌瘤没有效果,而H2KTs与铜的配合物则可明显抑制大鼠腹水癌瘤。由于研究这类化合物有重要意义,考虑到吲哚类化合物往往出具有多种生物活性,我们利用拼合原理设计合成了一种带有吲哚基团的缩氨基硫脲Schiff碱配体,并制备了其铜、镍、锌、钴四种边渡金属的配合物,并对配体和配合物的抗菌、抗种瘤活性进行了测试。 相似文献
999.
Qu S Qin C Islam A Wu Y Zhu W Hua J Tian H Han L 《Chemical communications (Cambridge, England)》2012,48(55):6972-6974
A novel D-A-π-A type organic dye (YCD01) incorporating a diketopyrrolopyrrole unit with a branched alkyl chain was synthesized for dye-sensitized solar cells. YCD01 showed a high conversion efficiency of 7.43% (AM 1.5, 100 mW cm(-2)) with a J(sc) of 13.40 mA cm(-2), a V(oc) of 0.76 V, a FF of 0.73 and an excellent stability. 相似文献
1000.