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81.
Dmitrii V. Zagorevskii Tatyana V. Volkova Sergey O. Yakushin Boris G. Antipov Yurii S. Nekrasov 《Journal of mass spectrometry : JMS》1991,26(9):748-750
Fragmentation of the acetyl- and propionyl-ferrocenes under electron impact together with the rupture of C? CO bonds, characteristic of ketones, also includes elimination of water and migration of the OH group to the central metal atom, which is due to keto-enol tautomerization of the acyl group in molecular or fragment ions. 相似文献
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Mikhail E. Minyaev Dmitrii M. Roitershtein Ilya E. Nifant'ev Ivan V. Ananyev Tatyana V. Minyaeva Timofey A. Mikhaylyev 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(6):491-498
(1RS,2SR,3RS,4SR,5RS)‐2,4‐Dibenzoyl‐1,3,5‐triphenylcyclohexan‐1‐ol or (4‐hydroxy‐2,4,6‐triphenylcyclohexane‐1,3‐diyl)bis(phenylmethanone), C38H32O3, (1), is formed as a by‐product in the NaOH‐catalyzed synthesis of 1,3,5‐triphenylpentane‐1,5‐dione from acetophenone and benzaldehyde. Single crystals of the chloroform hemisolvate, C38H32O3·0.5CHCl3, were grown from chloroform. The structure has triclinic (P) symmetry. One diastereomer [as a pair of (1RS,2SR,3RS,4SR,5RS)‐enantiomers] of (1) has been found in the crystal structure and confirmed by NMR studies. The dichoromethane hemisolvate has been reported previously [Zhang et al. (2007). Acta Cryst. E 63 , o4652]. (1RS,2SR,3RS,4SR,5RS)‐2,4‐Dibenzoyl‐3,5‐bis(2‐methoxyphenyl)‐1‐phenylcyclohexan‐1‐ol or [4‐hydroxy‐2,6‐bis(2‐methoxyphenyl)‐4‐phenylcyclohexane‐1,3‐diyl]bis(phenylmethanone), C40H36O5, (2), is also formed as a by‐product, under the same conditions, from acetophenone and 2‐methoxybenzaldehyde. Crystals of (2) have been grown from chloroform. The structure has orthorhombic (Pca21) symmetry. A diastereomer of (2) possesses the same configuration as (1). In both structures, the cyclohexane ring adopts a chair conformation with all bulky groups (benzoyl, phenyl and 2‐methoxyphenyl) in equatorial positions. The molecules of (1) and (2) both display one intramolecular O—H...O hydrogen bond. 相似文献
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Cyclotetrabenzoin: Facile Synthesis of a Shape‐Persistent Molecular Square and Its Assembly into Hydrogen‐Bonded Nanotubes 下载免费PDF全文
Qing Ji Ha T. M. Le Dr. Xiqu Wang Dr. Yu‐Sheng Chen Dr. Tatyana Makarenko Prof. Allan J. Jacobson Prof. Ognjen Š. Miljanić 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(48):17205-17209
Cyanide‐catalyzed benzoin condensation of terephthaldehyde produces a cyclic tetramer, which we propose to name cyclotetrabenzoin. Cyclotetrabenzoin is a square‐shaped macrocycle ornamented with four α‐hydroxyketone functionalities pointing away from the central cavity, the dimensions of which are 6.9×6.9 Å. In the solid state, these functional groups extensively hydrogen bond, resulting in a microporous three‐dimensional organic framework with one‐dimensional nanotube channels. This material exhibits permanent—albeit low‐porosity, with a Langmuir surface area of 52 m2 g?1. Cyclotetrabenzoin’s easy and inexpensive synthesis and purification may inspire the creation of other shape‐persistent macrocycles and porous molecular crystals by benzoin condensation. 相似文献
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Adaptive approximation (or interpolation) takes into account local variations in the behavior of the given function, adjusts
the approximant depending on it, and hence yields the smaller error of approximation. The question of constructing optimal
approximating spline for each function proved to be very hard. In fact, no polynomial time algorithm of adaptive spline approximation can be designed and no exact
formula for the optimal error of approximation can be given. Therefore, the next natural question would be to study the asymptotic
behavior of the error and construct asymptotically optimal sequences of partitions. In this paper we provide sharp asymptotic
estimates for the error of interpolation by splines on block partitions in
\mathbbRd{\mathbb{R}^d} . We consider various projection operators to define the interpolant and provide the analysis of the exact constant in the
asymptotics as well as its explicit form in certain cases. 相似文献
89.
Feyer V Plekan O Kivimäki A Prince KC Moskovskaya TE Zaytseva IL Soshnikov DY Trofimov AB 《The journal of physical chemistry. A》2011,115(26):7722-7733
Core-level X-ray photoemission and near-edge X-ray absorption fine structure spectra of 5-methylcytosine, 5-fluorocytosine, and isocytosine are presented and discussed with the aid of high-level ab initio calculations. The effects of the methylation, halogenation, and isomerization on the relative stabilities of cytosine tautomers are clearly identified spectroscopically. The hydroxy-oxo tautomeric forms of these molecules have been identified, and their quantitative populations at the experimental temperature are calculated and compared with the experimental results and with previous calculations. The calculated values of Gibbs free energy and Boltzmann population ratios are in good agreement with the experimental results characterizing tautomer equilibrium. 相似文献
90.
Tatyana Kovshova Nadezhda Osipova Anna Alekseeva Julia Malinovskaya Alexey Belov Andrey Budko Galina Pavlova Olga Maksimenko Shakti Nagpal Svenja Braner Harshvardhan Modh Vadim Balabanyan Matthias G. Wacker Svetlana Gelperina 《Molecules (Basel, Switzerland)》2021,26(4)
Targeted delivery of doxorubicin still poses a challenge with regards to the quantities reaching the target site as well as the specificity of the uptake. In the present approach, two colloidal nanocarrier systems, NanoCore-6.4 and NanoCore-7.4, loaded with doxorubicin and characterized by different drug release behaviors were evaluated in vitro and in vivo. The nanoparticles utilize a specific surface design to modulate the lipid corona by attracting blood-borne apolipoproteins involved in the endogenous transport of chylomicrons across the blood–brain barrier. When applying this strategy, the fine balance between drug release and carrier accumulation is responsible for targeted delivery. Drug release experiments in an aqueous medium resulted in a difference in drug release of approximately 20%, while a 10% difference was found in human serum. This difference affected the partitioning of doxorubicin in human blood and was reflected by the outcome of the pharmacokinetic study in rats. For the fast-releasing formulation NanoCore-6.4, the AUC0→1h was significantly lower (2999.1 ng × h/mL) than the one of NanoCore-7.4 (3589.5 ng × h/mL). A compartmental analysis using the physiologically-based nanocarrier biopharmaceutics model indicated a significant difference in the release behavior and targeting capability. A fraction of approximately 7.310–7.615% of NanoCore-7.4 was available for drug targeting, while for NanoCore-6.4 only 5.740–6.057% of the injected doxorubicin was accumulated. Although the targeting capabilities indicate bioequivalent behavior, they provide evidence for the quality-by-design approach followed in formulation development. 相似文献