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861.
在选择性催化还原(SCR)烟气脱硝系统中,催化剂碱(土)金属中毒和再生受到广泛关注。本文综述了SCR脱硝催化剂碱(土)金属中毒的失活机理及基于分子水平上碱金属中毒的研究新思路,并根据催化剂的各种失活机理,有针对性地综述了提高催化剂抗碱金属中毒的途径及中毒催化剂的再生方法。 相似文献
862.
Sequential Synthesis of 3 d–3 d, 3 d–4 d,and 3 d–5 d Hybrid Polyoxometalates and Application to the Electrocatalytic Oxygen Reduction Reactions
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Dr. Guillaume Rousseau Shuangshuang Zhang Dr. Olivier Oms Dr. Anne Dolbecq Dr. Jérôme Marrot Dr. Rongji Liu Xinke Shang Prof. Guangjin Zhang Prof. Pierre Mialane 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(34):12153-12160
The Co7(AlePy)2 polyoxometalate, which encloses a {(PW9)2CoII7} core covalently bound to two free aminopyridine groups through bisphosphonate ligands ( AlePy ), has been isolated. It can be used as a precursor, allowing the synthesis of heterometallic hybrid compounds, as illustrated by the characterization of cobalt/zinc ( Co7(AlePyZn)2 ), cobalt/palladium ( Co7(AlePyPd)2 ), and cobalt/platinum ( Co7(AlePyPt)2 ) species. A composite based on the water‐insoluble precious metal‐free Co7(AlePyZn)2 compound and the low‐cost carbon material Vulcan XC‐72 has been selected as a cathode material ( Co7Zn/C ) for oxygen reduction reaction studies. The electrocatalytic performances of the Co7Zn/C hybrids were assessed at neutral and basic pH, showing that Co7Zn/C exhibits high selectivity for the four‐electron reduction of O2. Moreover, its durability is superior to that of a commercial Pt/C catalyst with 20 % loading. Also, comparative studies performed in the presence of methanol have indicated that Co7Zn/C has a much better tolerance to the crossover effect than Pt/C . Altogether, these results indicate for the first time that, even in neutral media, polyoxometalate/carbon composites can represent low‐cost oxygen reduction catalysts that can function stably, for a long time, and with high performance. 相似文献
863.
Enhanced Photocatalytic Reduction of CO2 to CO through TiO2 Passivation of InP in Ionic Liquids
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Guangtong Zeng Jing Qiu Bingya Hou Haotian Shi Dr. Yongjing Lin Mark Hettick Prof. Ali Javey Prof. Stephen B. Cronin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(39):13502-13507
A robust and reliable method for improving the photocatalytic performance of InP, which is one of the best known materials for solar photoconversion (i.e., solar cells). In this article, we report substantial improvements (up to 18×) in the photocatalytic yields for CO2 reduction to CO through the surface passivation of InP with TiO2 deposited by atomic layer deposition (ALD). Here, the main mechanisms of enhancement are the introduction of catalytically active sites and the formation of a pn‐junction. Photoelectrochemical reactions were carried out in a nonaqueous solution consisting of ionic liquid, 1‐ethyl‐3‐methylimidazolium tetrafluoroborate ([EMIM]BF4), dissolved in acetonitrile, which enables CO2 reduction with a Faradaic efficiency of 99 % at an underpotential of +0.78 V. While the photocatalytic yield increases with the addition of the TiO2 layer, a corresponding drop in the photoluminescence intensity indicates the presence of catalytically active sites, which cause an increase in the electron‐hole pair recombination rate. NMR spectra show that the [EMIM]+ ions in solution form an intermediate complex with CO2?, thus lowering the energy barrier of this reaction. 相似文献
864.
James P. C. Coverdale Dr. Carlos Sanchez‐Cano Dr. Guy J. Clarkson Dr. Rina Soni Prof. Dr. Martin Wills Prof. Dr. Peter J. Sadler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(22):8043-8046
Asymmetric transfer hydrogenation (ATH) is an important process in organic synthesis for which the Noyori‐type RuII catalysts [(arene)Ru(Tsdiamine)] are now well established and widely used. We now demonstrate for the first time the catalytic activity of the osmium analogues. X‐ray crystal structures of the 16‐electron OsII catalysts are almost identical to those of RuII. Intriguingly the precursor complex was isolated as a dichlorido complex with a monodentate amine ligand. The OsII catalysts are readily synthesised (within 1 h) and exhibit excellent enantioselectivity in ATH reactions of ketones. 相似文献
865.
Chemical‐Bond‐Mediated p–n Heterojunction Photocatalyst Constructed from Coordination Polymer Nanoparticles and a Conducting Copolymer: Visible‐Light Active and Highly Efficient
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Prof. Dr. Xinxin Xu Dr. Tingting Lu Prof. Dr. Xiaoxia Liu Prof. Dr. Xiuli Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(48):17430-17436
A visible‐light‐active p–n heterojunction photocatalyst has been synthesized by the enwrapping of poly[aniline‐co‐N‐(4‐sulfophenyl)aniline] ( PAPSA ) on a coordination polymer nanoparticle ( NCP ). Compared with the visible‐light‐inactive NCP , the new p–n heterojunction photocatalyst, PAPSA/NCP , exhibits a much higher efficiency in the reduction of CrVI under visible light. PAPSA performs two functions in this p–n heterojunction photocatalyst. First, as a visible‐light‐active material, it extends the photoresponse region of the photocatalyst from the ultraviolet to the visible‐light region. Secondly, as a p‐type semiconductor possessing suitable energy levels with respect to NCP , PAPSA forms a p–n heterojunction with the n‐type NCP ; the inner electric field of the p–n heterojunction accelerates the separation of electrons and holes, which enhances the photocatalytic efficiency. Furthermore, the p–n heterojunction photocatalyst exhibits outstanding stability during the photocatalytic reduction of CrVI. 相似文献
866.
867.
N. Chary Mamillapalli Prof. Govindasamy Sekar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(51):18584-18588
Synthesis of enantiomerically enriched α‐hydroxy amides and β‐amino alcohols has been accomplished by enantioselective reduction of α‐keto amides with hydrosilanes. A series of α‐keto amides were reduced in the presence of chiral CuII/(S)‐DTBM‐SEGPHOS catalyst to give the corresponding optically active α‐hydroxy amides with excellent enantioselectivities by using (EtO)3SiH as a reducing agent. Furthermore, a one‐pot complete reduction of both ketone and amide groups of α‐keto amides has been achieved using the same chiral copper catalyst followed by tetra‐n‐butylammonium fluoride (TBAF) catalyst in presence of (EtO)3SiH to afford the corresponding chiral β‐amino alcohol derivatives. 相似文献
868.
以高锰酸钾和硝酸锰为锰源,采用改进的共沉淀法制备了不同Ce/Mn摩尔比的Ce O2-Mn Ox催化剂.以NH3为还原剂,考察了催化剂低温(小于150℃)NH3选择性催化还原NO的性能.并采用XRD,BET,H2-TPR,NH3-TPD和XPS等手段对催化剂的物理化学性质进行表征.结果表明,Ce O2-Mn Ox催化剂在50~150℃温度区间内表现出了良好的催化活性.引入适量的Ce可以有效地改变催化剂的晶粒大小,增强其氧化还原能力;而Mn的加入,促进了其低温SCR活性.当Ce/Mn摩尔比为1∶3时(C1M3),低温活性最佳,在82~150℃温度区间内NO去除率达到90%以上,这主要是由于C1M3催化剂有较高含量的表面吸附氧、大量的弱酸性位点、良好的氧化还原性能以及表面较高含量的Mn4+物种. 相似文献
869.
分别采用共沉淀法和浸渍法、不同铁前驱物以及不同焙烧温度等研究了制备工艺对Mn-Fe/ZSM-5催化剂的结构、化学组分及NH3-SCR活性的影响。结果显示,当采用Fe(NO3)3作为Fe前驱物,并用共沉淀法制备、300°C焙烧条件下得到的MFZ-CP-N-300样品低温活性最优,在120°C时,其NO的转化率达到96.7%,120-300°C范围内NO转化率始终保持在95%以上。同时利用XRD、NH3-TPD、XPS、SEM、TEM、氮吸附等手段对催化剂结构、晶相、酸位、锰铁氧化物的化学形态及表面的形貌特征进行表征分析。结果表明锰铁氧化物分别以MnO2-Mn2O3和Fe2O3的形式高度分散于催化剂表面,特别是当Mn4+/Mn3+比例为1.254时,有较强的表面中强酸和较多的酸位数,从而增加了NH3的吸附能力,提高NO的转化率。 相似文献
870.