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91.
Copper‐Catalyzed Propargylic Substitution of Dichloro Substrates: Enantioselective Synthesis of Trisubstituted Allenes and Formation of Propargylic Quaternary Stereogenic Centers
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Dr. Hailing Li Dr. David Grassi Dr. Laure Guénée Prof. Dr. Thomas Bürgi Prof. Dr. Alexandre Alexakis 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(50):16694-16706
An easy and versatile Cu‐catalyzed propargylic substitution process is presented. Using easily prepared prochiral dichloro substrates, readily available Grignard reagents together with catalytic amount of copper salt and chiral ligand, we accessed a range of synthetically interesting trisubstituted chloroallenes. Substrate scope and nucleophile scope are broad, providing generally high enantioselectivity for the desired 1,3‐substitution products. The enantioenriched chloroallenes could be further transformed into the corresponding trisubstituted allenes or terminal alkynes bearing all‐carbon quaternary stereogenic centers, through the copper‐catalyzed enantiospecific 1,1/1,3‐substitutions. The two successive copper‐catalyzed reactions could be eventually combined into a one‐pot procedure and different desired allenes or alkynes were obtained respectively with high enantiomeric excesses. 相似文献
92.
From Enantiopure Hydroxyaldehydes to Complex Heterocyclic Scaffolds: Development of Domino Petasis/Diels–Alder and Cross‐Metathesis/Michael Addition Reactions
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Dr. Alexandre Cannillo Dr. Stéphanie Norsikian Dr. Marie‐Elise Tran Huu Dau Dr. Pascal Retailleau Dr. Bogdan I. Iorga Prof. Jean‐Marie Beau 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(38):12133-12143
One‐step assembly of hexahydroisoindole scaffolds by a sequence that combines the Petasis (borono‐Mannich) and Diels–Alder reactions is described. The unique selectivity observed experimentally was confirmed by quantum calculations. The current method is applicable to a broad range of substrates, including free sugars, and holds significant potential to efficiently and stereoselectively build new heterocyclic structures. This easy and fast entry to functionalized polycyclic compounds can be pursued by further transformations, for example, additional ring closure by a cross‐metathesis/Michael addition domino sequence. 相似文献
93.
94.
Shunrui Luo Kostiantyn Turcheniuk Ah‐Young Song Aashray Narla Doyoub Kim Alexandre Magasinsky Gleb Yushin 《Angewandte Chemie (International ed. in English)》2020,59(1):403-408
Technologically important composites with enhanced thermal and mechanical properties rely on the reinforcement by the high specific strength ceramic nanofibers or nanowires (NWs) with high aspect ratios. However, conventional synthesis routes to produce such ceramic NWs have prohibitively high cost. Now, direct transformation of bulk Mg‐Li alloys into Mg alkoxide NWs is demonstrated without the use of catalysts, templates, expensive or toxic chemicals, or any external stimuli. This mechanism proceeds through the minimization of strain energy at the boundary of phase transformation front leading to the formation of ultra‐long NWs with tunable dimensions. Such alkoxide NWs can be easily converted in air into ceramic MgO NWs with similar dimensions. The impact of the alloy grain size and Li content, synthesis temperature, inductive and steric effects of alkoxide groups on the diameter, length, composition, ductility, and oxidation of the produced NWs is discussed. 相似文献
95.
Nikita K. Kulachenkov Dapeng Sun Yuri A. Mezenov Andrei N. Yankin Sergey Rzhevskiy Vyacheslav Dyachuk Alexandre Nomin Ghouti Medjahdi Evgeny A. Pidko Valentin A. Milichko 《Angewandte Chemie (International ed. in English)》2020,59(36):15522-15526
We demonstrate herein an all‐optical switch based on stimuli‐responsive and photochromic‐free metal–organic framework (HKUST‐1). Ultrafast near‐infrared laser pulses stimulate a reversible 0.4 eV blue shift of the absorption band with up to 200 s?1 rate due to dehydration and concomitant shrinking of the structure‐forming [Cu2C4O8] cages of HKUST‐1. Such light‐induced switching enables the remote modulation of intensities of photoluminescence of single crystals of HKUST‐1 as well visible radiation passing through the crystal by 2 order of magnitude. This opens up the possibility of utilyzing stimuli‐responsive MOFs for all‐optical data processing devices. 相似文献
96.
Peiguang Zhou Alexandre Blumstein 《Journal of polymer science. Part A, Polymer chemistry》1996,34(16):3399-3406
An interpenetrating polymer network (IPN) based on poly(N-butyl 2-ethynylpyridinum bromide) (PB2EPB) and polycarbonate-urethane (PCU) has been prepared and characterized. The simultaneous full IPNs of PCU and PB2EPB have two glass transition temperatures corresponding to those of the linear chain blends measured by DSC. This suggests immiscibility of the two networks in the IPNs. The IPNs display a multiphase morphology which is confirmed by SEM observation. The full IPNs exhibit excellent solvent resistance, good thermal stability and good mechanical properties. High UV absorption of these materials extending to the visible range and beyond indicates that the polyacetylene network is extensively conjugated. The electrical conductivity of the IPNs increases linearly with increasing polyacetylene content reaching 10-4 S/cm. © 1996 John Wiley & Sons, Inc. 相似文献
97.
98.
Inside Cover: Supramolecular Complexes of Multivalent Cholesterol‐Containing Polymers to Solubilize Carbon Nanotubes in Apolar Organic Solvents (Chem. Asian J. 5/2014)
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99.
Dr. Louwanda Lakiss Dr. Aurélie Vicente Prof. Jean-Pierre Gilson Dr. Valentin Valtchev Dr. Svetlana Mintova Dr. Alexandre Vimont Dr. Robert Bedard Dr. Suheil Abdo Dr. Jeffery Bricker 《Chemphyschem》2020,21(16):1873-1881
We outline two methodologies to selectively characterize the Brønsted acidity of the external surface of FAU-type zeolites by IR and NMR spectroscopy of adsorbed basic probe molecules. The challenge and goal are to develop reliable and quantitative IR and NMR methodologies to investigate the accessibility of acidic sites in the large pore FAU-type zeolite Y and its mesoporous derivatives often referred to as ultra-stable Y (USY). The accessibility of their Brønsted acid sites to probe molecules (n-alkylamines, n-alkylpyridines, n-alkylphosphine- and phenylphosphine-oxides) of different molecular sizes is quantitatively monitored either by IR or 31P NMR spectroscopy. It is now possible, for the first time to quantitatively discriminate between the Brønsted acidity located in the microporosity and on the external surface of large pore zeolites. For instance, the number of external acid sites on a Y (LZY-64) zeolite represents 2 % of its total acid sites while that of a USY (CBV760) represents 4 % while the latter has a much lower framework Si/Al ratio. 相似文献
100.
Rosana V. Pinto Sujing Wang Sergio R. Tavares Joo Pires Fernando Antunes Alexandre Vimont Guillaume Clet Marco Daturi Guillaume Maurin Christian Serre Moiss L. Pinto 《Angewandte Chemie (International ed. in English)》2020,59(13):5135-5143
Materials for the controlled release of nitric oxide (NO) are of interest for therapeutic applications. However, to date, many suffer from toxicity and stability issues, as well as poor performance. Herein, we propose a new NO adsorption/release mechanism through the formation of nitrites on the skeleton of a titanium‐based metal–organic framework (MOF) that we named MIP‐177, featuring a suitable set of properties for such an application: (i) high NO storage capacity (3 μmol mg?1solid), (ii) excellent biocompatibility at therapeutic relevant concentrations (no cytotoxicity at 90 μg mL?1 for wound healing) due to its high stability in biological media (<9 % degradation in 72 hours) and (iii) slow NO release in biological media (≈2 hours for 90 % release). The prospective application of MIP‐177 is demonstrated through NO‐driven control of mitochondrial respiration in cells and stimulation of cell migration, paving the way for the design of new NO delivery systems for wound healing therapy. 相似文献