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991.
Kurt Schank Claude Marson Thomas Heisel Klaus Martens Christiane Wagner 《Helvetica chimica acta》2000,83(12):3312-3332
Surprising Results during the Re‐investigation of the Formation and Decomposition of Triptene Ozonide . Revision of the ozonolysis of triptene (=2,3,3‐trimethylbut‐1‐ene; 1 ) revealed that molecular oxygen of an applied ozone/oxygen gas mixture participates as well in the cleavage of the C=C bond as in the ozonide formation. Ozone‐to‐olefin stoichiometry varies in the range of 0.64 – 0.95 : 1 in terms of complete olefin consumption, depending on solvents, on reaction temperature, and on reaction conditions. Thermal decomposition of distilled monomeric triptene ozonide ( 2 ) does not lead to 3,6‐di(tert‐butyl)‐3,6‐dimethyl‐1,2,4,5‐tetroxane ( 5 ), which is formed by formaldehyde extrusion from an unstable oligomeric (probably dimeric) triptene ozonide 2 ′. Acid‐catalyzed decomposition of 2 exclusively yields pinacolone ( 7 ) and formic acid ( 9 ). 相似文献
992.
A simple and fast synthesis of radioactive methylmercury is presented. It is based on the methylation of inorganic 203Hg(II) by methylcobalamin and isolation of resulting CH3203Hg(II) in a single extraction step. Time required is less than 4 hours and the final yield is ⩾90%. © 1997 John Wiley & Sons, Ltd. 相似文献
993.
Claude Rouleau 《应用有机金属化学》1998,12(6):435-438
A method of synthesis of tributyl[113Sn]tin,(n/C4H9)3113Sn(IV), from commercially avail-able inorganic 113Sn(IV) is presented. Inorganic tin is first extracted in diethyl ether and reacted with C4H9MgCl to produce tetrabutyltin, (C4H9)4113Sn, which is then debutylated with HgCl2. The resulting tributyl[113Sn]tin chloride is isolated from the reaction mixture by successive extractions with hexane and aqueous Na2S2O3. The yield is 40–60% and the product obtained is >98% pure. It has the same specific activity as the starting 113Sn(IV), i.e. up to 550 MBq mg−1 Sn, making it suitable for use in environmental fate and toxicology studies at concentrations relevant of those found in the aquatic environment. © 1998 John Wiley & Sons, Ltd. 相似文献
994.
Narcis Avarvari Pascal Le Floch Claude Charrier Franois Mathey 《Heteroatom Chemistry》1996,7(5):397-402
1-Alkynyl-1,2-dihydrophosphetes, as prepared by reaction of the appropriate titanacyclobutenes with alkynyldichlorophosphines, rearrange to the corresponding phosphinines via an original 4π-cycloreversion-6π-electrocyclization mechanism. The reaction of dimethyltitanocene with 1,4-diphenylbutadiyne affords a new 3-vinyltitanacyclobut-3-ene that can serve to prepare a 3-vinylphosphinine 6 by the same route. © 1996 John Wiley & Sons, Inc. 相似文献
995.
T. Watanabe D. Zou B. Mohamed H. Usui S. Miyata C. Claude Y. Okamoto 《Macromolecular Symposia》1995,98(1):895-895
Second-harmonic generation in the guided waveguide configuration is very attractive because a high fundamental power density can be coupled over long propagation length therefore remarkably high conversion efficiencies can be expected compared to bulk materials.1 Organic SHG devices in optical waveguides have not been developed extensively because of the difficulty encountered in phase-matching. To avoid this problem, the use of an artificial periodic structure, Cerenkov radiation, and non-colinear light path geometry have already been demonstrated. Recently, we reported an electric field-induced dynamic phase-matching in a guided wave configuration using a main-chain polymer in which the effective phase-matching thickness can be controlled by an applied electric field.2 This technique is able to increase the waveguide dimension tolerances of phase-matching condition. In the case of a main-chain polymer, the thermal optic effects due to the heating prevent to satisfy the optimum phase-matching conditions, which causes a reduction in the conversion efficiency of devices. In order to overcome this problem, we have synthesized novel low glass transition temperature (Tg) nonlinear optical (NLO) polymers. In this presentation, we will discuss an electric field-induced dynamic phase-matching of a multilayer waveguide at room temperature using a low Tg NLO polymer which can increase both the waveguide dimension tolerances and overlap integral. Using this technique, efficient phase-matched SHG was generated from p-nitroaniline grafted NLO materials. The dimension tolerance of waveguides under an electric field will be described. 相似文献
996.
The Caenorhabditis elegans DEG-3/DES-2 Channel Is a Betaine-Gated Receptor Insensitive to Monepantel
Tina V. A. Hansen Heinz Sager Cline E. Toutain Elise Courtot Cdric Neveu Claude L. Charvet 《Molecules (Basel, Switzerland)》2022,27(1)
Natural plant compounds, such as betaine, are described to have nematocidal properties. Betaine also acts as a neurotransmitter in the free-living model nematode Caenorhabditis elegans, where it is required for normal motility. Worm motility is mediated by nicotinic acetylcholine receptors (nAChRs), including subunits from the nematode-specific DEG-3 group. Not all types of nAChRs in this group are associated with motility, and one of these is the DEG-3/DES-2 channel from C. elegans, which is involved in nociception and possibly chemotaxis. Interestingly, the activity of DEG-3/DES-2 channel from the parasitic nematode of ruminants, Haemonchus contortus, is modulated by monepantel and its sulfone metabolite, which belong to the amino-acetonitrile derivative anthelmintic drug class. Here, our aim was to advance the pharmacological knowledge of the DEG-3/DES-2 channel from C. elegans by functionally expressing the DEG-3/DES-2 channel in Xenopus laevis oocytes and using two-electrode voltage-clamp electrophysiology. We found that the DEG-3/DES-2 channel was more sensitive to betaine than ACh and choline, but insensitive to monepantel and monepantel sulfone when used as direct agonists and as allosteric modulators in co-application with betaine. These findings provide important insight into the pharmacology of DEG-3/DES-2 from C. elegans and highlight the pharmacological differences between non-parasitic and parasitic nematode species. 相似文献
997.
998.
999.
Yves Claude Guillaume Lydie Lethier Claire André 《Biomedical chromatography : BMC》2015,29(9):1338-1342
In a previous paper Guillaume's group demonstrated that magnesium (Mg2+ concentration range 0.00–2.60 mm ) increased the passive diffusion of statins and thus played a role in their potential toxicity. In order to confirm an increase in this passive diffusion by divalent salt cations, the role of calcium chloride (CaCl2) on the statin–immobilized artificial membrane (IAM) association was studied. It was demonstrated that calcium supplementation (Ca2+ concentration range 0.00–3.25 mm ) increases the statin passive diffusion. In addition, it was shown that the Ca2+ effect on the statin–IAM association is higher than that of Mg2+. These results show that Ca2+ enhances the passive diffusion of drugs into biological membranes and thus their potential toxicity. Also, addition of H2O2 to the medium showed a hyperbolic response for the statin passive diffusion and this effect was enhanced for the highest Ca2+ or Mg2+ concentrations in the medium. H2O2 is likely to interact with the polar head groups of the IAM through dipole–dipole interactions. The conformational changes in H2O2–IAM result in a higher degree of exposure of hydrophobic areas, thus explaining why the binding of pravastatin, which showed the lowest logP value, was less affected by H2O2. This result shows the significant contribution of H2O2 and thus the oxidative stress on the statin passive diffusion. Much of the sensitivity derives from the action of Ca2+ or Mg2+, in turn supported the idea that H2O2 may serve a Ca2+ or Mg2+ sensing function in statin passive diffusion Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
1000.