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141.
Pascal Wintergerst Kamil Witas Djawed Nauroozi Marie-Ann Schmid Ebru Dikmen Stefanie Tschierlei Sven Rau 《无机化学与普通化学杂志》2020,646(13):842-848
The synthesis of alkyne functionalized bipyridine ruthenium complexes are reported. The improved synthetic approach through application of stable protecting groups prevents formation of possible side products while facilitating purification. By applying copper-catalysed azide-alkyne cycloaddition reactions (CuAAC) pyrene units with flexible alkyl linkers are introduced at the periphery of the complex, opening up various applications including surface immobilization and DNA intercalation. All complexes are characterized structurally as well as photophysically, especially regarding the influence of the introduced alkyne and triazolyl substituents on their photophysical behavior. 相似文献
142.
Henrik Land Alina Sekretareva Ping Huang Holly J. Redman Brigitta Nmeth Nakia Polidori Lívia S. Mszros Moritz Senger Sven T. Stripp Gustav Berggren 《Chemical science》2020,11(47):12789
[FeFe]-hydrogenases are known for their high rates of hydrogen turnover, and are intensively studied in the context of biotechnological applications. Evolution has generated a plethora of different subclasses with widely different characteristics. The M2e subclass is phylogenetically distinct from previously characterized members of this enzyme family and its biological role is unknown. It features significant differences in domain- and active site architecture, and is most closely related to the putative sensory [FeFe]-hydrogenases. Here we report the first comprehensive biochemical and spectroscopical characterization of an M2e enzyme, derived from Thermoanaerobacter mathranii. As compared to other [FeFe]-hydrogenases characterized to-date, this enzyme displays an increased H2 affinity, higher activation enthalpies for H+/H2 interconversion, and unusual reactivity towards known hydrogenase inhibitors. These properties are related to differences in active site architecture between the M2e [FeFe]-hydrogenase and “prototypical” [FeFe]-hydrogenases. Thus, this study provides new insight into the role of this subclass in hydrogen metabolism and the influence of the active site pocket on the chemistry of the H-cluster.Characterization of a group D putative sensory [FeFe]-hydrogenase reveals how the active site can be tuned to decrease CO inhibition and increase stability of a reduced H-cluster while retaining the ability to catalyze H+/H2 interconversion. 相似文献
143.
Nikolaus Nestle Zi Jian Lim Tobias Böhringer Sarah Abtmeyer Sven Arenz Felix C. Leinweber Thomas Weiß Erik von Harbou 《Magnetic resonance in chemistry : MRC》2020,58(12):1213-1221
The considerations for use of compact nuclear magnetic resonance in a large-scale industrial environment clearly differ from those in academic and educational settings and even from those in smaller companies. In the first part of this article, these differences will be discussed along with the additional requirements that need to be fulfilled for successful applicability in different use cases. In the second part of the article, outcomes from different research activities aiming to fulfill these requirements will be presented with a focus on an online reaction-monitoring study on a lab-scale nucleophilic chlorination reaction. 相似文献
144.
Anja Müller Katia Sparnacci Wolfgang E.S. Unger Sven Tougaard 《Surface and interface analysis : SIA》2020,52(11):770-777
Most real core-shell nanoparticle (CSNP) samples deviate from an ideal core-shell structure potentially having significant impact on the particle properties. An ideal structure displays a spherical core fully encapsulated by a shell of homogeneous thickness, and all particles in the sample exhibit the same shell thickness. Therefore, analytical techniques are required that can identify and characterize such deviations. This study demonstrates that by analysis of the inelastic background in X-ray photoelectron spectroscopy (XPS) survey spectra, the following types of deviations can be identified and quantified: the nonuniformity of the shell thickness within a nanoparticle sample and the incomplete encapsulation of the cores by the shell material. Furthermore, CSNP shell thicknesses and relative coverages can be obtained. These results allow for a quick and straightforward comparison between several batches of a specific CSNP, different coating approaches, and so forth. The presented XPS methodology requires a submonolayer distribution of CSNPs on a substrate. Poly(tetrafluoroethylene)-poly(methyl methacrylate) and poly(tetrafluoroethylene)-polystyrene polymer CSNPs serve as model systems to demonstrate the applicability of the approach. 相似文献
145.
We present a comprehensive theoretical investigation of the influence of the ligand L on the regulation of the product selectivity for the [Ni(0)L]-catalyzed cyclodimerization of 1,3-butadiene. The investigation was based on density functional theory (DFT) and a combined DFT and molecular mechanics (QM/MM) approach for the real [bis(butadiene)Ni(0)L] catalysts with L = PMe(3), I; PPh(3), II; P((i)Pr)(3), III; and P(OPh)(3), IV. The role of electronic and steric effects has been elucidated for all crucial elementary steps of the entire catalytic cycle. Allylic isomerization, allylic enantioface conversion, as well as oxidative coupling are shown to be influenced to a minor extent by electronic and steric effects. In contrast, the ligand's properties have a distinct influence on the preestablished equilibrium between the eta(3),eta(1)(C(1)) and bis-eta(3) forms 2 and 4, respectively, of the [(octadienediyl)Ni(II)L] complex and on the rate-determining reductive elimination following competing routes for generation of either VCH, cis-1,2-DVCB, or cis,cis-COD. Electronic factors are shown to predominantly determine the position of the kinetically mobile 2 right harpoon over left harpoon 4 equilibrium. 4 is the prevailing species for ligands L that are pi-acceptors (L = P(OPh)(3)) or weak sigma-donors (L = PPh(3)), while stronger sigma-donors (L = PMe(3), P((i)Pr)(3)) displace the equilibrium to the left. Steric bulk on the ligand as well as its pi-acceptor ability act to facilitate the reductive elimination, while sigma-donor abilities serve to retard this process. Electronic and steric factors are found to not influence uniformly the reductive elimination routes with either 2 or 4 involved. The regulation of the product selectivity is elucidated on the basis of both thermodynamic and kinetic considerations. 相似文献
146.
A Separation‐Integrated Cascade Reaction to Overcome Thermodynamic Limitations in Rare‐Sugar Synthesis 下载免费PDF全文
Nina Wagner Andreas Bosshart Jurek Failmezger Dr. Matthias Bechtold Prof. Sven Panke 《Angewandte Chemie (International ed. in English)》2015,54(14):4182-4186
Enzyme cascades combining epimerization and isomerization steps offer an attractive route for the generic production of rare sugars starting from accessible bulk sugars but suffer from the unfavorable position of the thermodynamic equilibrium, thus reducing the yield and requiring complex work‐up procedures to separate pure product from the reaction mixture. Presented herein is the integration of a multienzyme cascade reaction with continuous chromatography, realized as simulated moving bed chromatography, to overcome the intrinsic yield limitation. Efficient production of D ‐psicose from sucrose in a three‐step cascade reaction using invertase, D ‐xylose isomerase, and D ‐tagatose epimerase, via the intermediates D ‐glucose and D ‐fructose, is described. This set‐up allowed the production of pure psicose (99.9 %) with very high yields (89 %) and high enzyme efficiency (300 g of D ‐psicose per g of enzyme). 相似文献
147.
M. Sc. Yasemin Akbulut Hannah J. Gaunt Prof. Katsuhiko Muraki Dr. Melanie J. Ludlow Dr. Mohamed S. Amer Dr. Alexander Bruns Dr. Naveen S. Vasudev Dr. Lea Radtke Dr. Matthieu Willot M. Sc. Sven Hahn M. Sc. Tobias Seitz Dr. Slava Ziegler Prof. Dr. Mathias Christmann Prof. Dr. David J. Beech Prof. Dr. Herbert Waldmann 《Angewandte Chemie (International ed. in English)》2015,54(12):3787-3791
Current therapies for common types of cancer such as renal cell cancer are often ineffective and unspecific, and novel pharmacological targets and approaches are in high demand. Here we show the unexpected possibility for the rapid and selective killing of renal cancer cells through activation of calcium‐permeable nonselective transient receptor potential canonical (TRPC) calcium channels by the sesquiterpene (?)‐englerin A. This compound was found to be a highly efficient, fast‐acting, potent, selective, and direct stimulator of TRPC4 and TRPC5 channels. TRPC4/5 activation through a high‐affinity extracellular (?)‐englerin A binding site may open up novel opportunities for drug discovery aimed at renal cancer. 相似文献
148.
Michael G. Pfeffer Tanja Kowacs Dr. Maria Wächtler Dr. Julien Guthmuller Prof. Dr. Benjamin Dietzek Prof. Dr. Johannes G. Vos Prof. Dr. Sven Rau 《Angewandte Chemie (International ed. in English)》2015,54(22):6627-6631
A molecular photocatalyst consisting of a RuII photocenter, a tetrapyridophenazine bridging ligand, and a PtX2 (X=Cl or I) moiety as the catalytic center functions as a stable system for light‐driven hydrogen production. The catalytic activity of this photochemical molecular device (PMD) is significantly enhanced by exchanging the terminal chlorides at the Pt center for iodide ligands. Ultrafast transient absorption spectroscopy shows that the intramolecular photophysics are not affected by this change. Additionally, the general catalytic behavior, that is, instant hydrogen formation, a constant turnover frequency, and stability are maintained. Unlike as observed for the Pd analogue, the presence of excess halide does not affect the hydrogen generation capacity of the PMD. The highly improved catalytic efficiency is explained by an increased electron density at the Pt catalytic center, this is confirmed by DFT studies. 相似文献
149.
Square‐Planar Ruthenium(II) Complexes: Control of Spin State by Pincer Ligand Functionalization 下载免费PDF全文
Dr. Bjorn Askevold Dr. Marat M. Khusniyarov Dr. Wolfgang Kroener Dr. Klaus Gieb Prof. Paul Müller Dr. Eberhardt Herdtweck Dr. Frank W. Heinemann Dr. Martin Diefenbach Prof. Max C. Holthausen Veacheslav Vieru Prof. Liviu F. Chibotaru Prof. Sven Schneider 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(2):579-589
Functionalization of the PNP pincer ligand backbone allows for a comparison of the dialkyl amido, vinyl alkyl amido, and divinyl amido ruthenium(II) pincer complex series [RuCl{N(CH2CH2PtBu2)2}], [RuCl{N(CHCHPtBu2)(CH2CH2PtBu2)}], and [RuCl{N(CHCHPtBu2)2}], in which the ruthenium(II) ions are in the extremely rare square‐planar coordination geometry. Whereas the dialkylamido complex adopts an electronic singlet (S=0) ground state and energetically low‐lying triplet (S=1) state, the vinyl alkyl amido and the divinyl amido complexes exhibit unusual triplet (S=1) ground states as confirmed by experimental and computational examination. However, essentially non‐magnetic ground states arise for the two intermediate‐spin complexes owing to unusually large zero‐field splitting (D>+200 cm?1). The change in ground state electronic configuration is attributed to tailored pincer ligand‐to‐metal π‐donation within the PNP ligand series. 相似文献
150.
Dr. Natalie Spomer Dr. Sven Holl Dr. Larissa Zherlitsyna Dr. Fariba Maysamy Andreas Frost Prof. Dr. Norbert Auner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(14):5600-5616
Amorphous silicon is synthesized by treating the tetrahalosilanes SiX4 (X=Cl, F) with molten sodium in high boiling polar and non‐polar solvents such as diglyme or nonane to give a brown or a black solid showing different reactivities towards suitable reagents. With regards to their technical relevance, their stability towards oxygen, air, moisture, chlorine‐containing reaction partners RCl (R=H, Cl, Me) and alcohols is investigated. In particular, reactions with methanol are a versatile tool to deliver important products. Besides tetramethoxysilane formation, methanolysis of silicon releases hydrogen gas under ambient conditions and is thus suitable for a decentralized hydrogen production; competitive insertion into the MeO?H versus the Me?OH bond either yields H‐ and/or methyl‐substituted methoxy functional silanes. Moreover, compounds, such as MenSi(OMe)4?n (n=0–3) are simply accessible in more than 75 % yield from thermolysis of, for example, tetramethoxysilane over molten sodium. Based on our systematic investigations we identified reaction conditions to produce the methoxysilanes MenSi(OMe)4?n in excellent (n=0:100 %) to acceptable yields (n=1:51 %; n=2:27 %); the yield of HSi(OMe)3 is about 85 %. Thus, the methoxysilanes formed might possibly open the door for future routes to silicon‐based products. 相似文献