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51.
Xu X Zhao Z Song P Zhou G Xu J Deng P Bourdet G Chanteloup JC Zou JP Fulop A 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(11-12):2444-2447
Infrared (1.2-1.6 microm) luminescence in a ytterbium aluminium garnet (YbAG) crystal, doped with Cr (0.05at.%) ions, was investigated under CW laser diode pumping (lambda=940 nm). The Cr4+ emission band was observed with its peak at 1.34 microm and measured to be about 1.3 times with respect to Yb3+ IR luminescence (lambda=1.03 microm). We demonstrate that for the excitation wavelength of 940 nm Yb3+ ions act as sensitizers of the 3B2(3T2)-3B1(3A2) emission of Cr4+ ions. This crystal is promising as a high-efficient system for tunable laser (1.2-1.6 microm) output. 相似文献
52.
The one-carbon elongation of aldoses to ketoses using iodomethyllithium as the key reagent in the homologation step is exemplified by the preparation of two carbohydrates of chemical and biological interests: d-manno-hept-2-ulose from d-mannose and l-fructose from l-arabinose. 相似文献
53.
Quantum Machine Learning (QML) has not yet demonstrated extensively and clearly its advantages compared to the classical machine learning approach. So far, there are only specific cases where some quantum-inspired techniques have achieved small incremental advantages, and a few experimental cases in hybrid quantum computing are promising, considering a mid-term future (not taking into account the achievements purely associated with optimization using quantum-classical algorithms). The current quantum computers are noisy and have few qubits to test, making it difficult to demonstrate the current and potential quantum advantage of QML methods. This study shows that we can achieve better classical encoding and performance of quantum classifiers by using Linear Discriminant Analysis (LDA) during the data preprocessing step. As a result, the Variational Quantum Algorithm (VQA) shows a gain of performance in balanced accuracy with the LDA technique and outperforms baseline classical classifiers. 相似文献
54.
55.
Janis V. Musso Jordan De Jesus Silva Mathis J. Benedikter Jonas Groos Wolfgang Frey Christophe Copret Michael R. Buchmeiser 《Chemical science》2022,13(29):8649
Cationic d0 group 6 olefin metathesis catalysts have been recently shown to display in most instances superior activity in comparison to their neutral congeners. Furthermore, their catalytic performance is greatly improved upon immobilization on silica. In this context, we have developed the new family of molecular cationic molybdenum oxo alkylidene complexes stabilized by N-heterocyclic carbenes of the general formula [Mo(O)(CHCMe3)(IMes)(OR)[X−]] (IMes = 1,3-dimesitylimidazol-2-ylidene; R = 1,3-dimesityl-C6H3, C6F5; X− = B(3,5-(CF3)2C6H3)4−, B(ArF)4, tetrakis(perfluoro-t-butoxy)aluminate (PFTA)). Immobilization of [Mo(O)(CHCMe3)(IMes)(O-1,3-dimesityl-C6H3)+B(ArF)4−] on silica via surface organometallic chemistry yields an active alkene metathesis catalyst that shows the highest productivity towards terminal olefins amongst all existing molybdenum oxo alkylidene catalysts.The first cationic molybdenum oxo complexes were synthesized and immobilized on partially dehydroxylated silica. Vastly enhanced catalytic activity for terminal olefins was found compared to their neutral congeners. 相似文献
56.
Emanuele Antico Markus Leutzsch Niklas Wessel Thomas Weyhermüller Christophe Werl Walter Leitner 《Chemical science》2022,14(1):54
The development of earth-abundant catalysts for the selective conversion of silanes to silanols with water as an oxidant generating valuable hydrogen as the only by-product continues to be a challenge. Here, we demonstrate that [MnBr(CO)5] is a highly active precatalyst for this reaction, operating under neutral conditions and avoiding the undesired formation of siloxanes. As a result, a broad substrate scope, including primary and secondary silanes, could be converted to the desired products. The turnover performances of the catalyst were also examined, yielding a maximum TOF of 4088 h−1. New light was shed on the debated mechanism of the interaction between [MnBr(CO)5] and Si–H bonds based on the reaction kinetics (including KIEs of PhMe2SiD and D2O) and spectroscopic techniques (FT-IR, GC-TCD, 1H-, 29Si-, and 13C-NMR). The initial activation of [MnBr(CO)5] was found to result from the formation of a manganese(i) hydride species and R3SiBr, and the experimental data are most consistent with a catalytic cycle comprising a cationic tricarbonyl Mn(i) unit as the active framework.This study presents the use of MnBr(CO)5 for the selective conversion of silanes to silanols with water as an oxidant generating valuable hydrogen as the only by-product. 相似文献
57.
Laurent Aubry Thierry Sayd Claude Ferreira Christophe Chambon Annie Vnien Sylvie Blinet Marie Bourin Anglique Travel Maeva Halgrain Vronique Sant-Lhoutellier Laetitia Thron 《Molecules (Basel, Switzerland)》2021,26(12)
The marketing of poultry livers is only authorized as fresh, frozen, or deep-frozen. The higher consumer demand for these products for a short period of time may lead to the marketing of frozen–thawed poultry livers: this constitutes fraud. The aim of this study was to design a method for distinguishing frozen–thawed livers from fresh livers. For this, the spectral fingerprint of liver proteins was acquired using Matrix-Assisted Laser Dissociation Ionization-Time-Of-Flight mass spectrometry. The spectra were analyzed using the chemometrics approach. First, principal component analysis studied the expected variability of commercial conditions before and after freezing–thawing. Then, the discriminant power of spectral fingerprint of liver proteins was assessed using supervised model generation. The combined approach of mass spectrometry and chemometrics successfully described the evolution of protein profile during storage time, before and after freezing-thawing, and successfully discriminated the fresh and frozen–thawed livers. These results are promising in terms of fraud detection, providing an opportunity for implementation of a reference method for agencies to fight fraud. 相似文献
58.
Electrochemical blocking is a type of single-entity electrochemical measurement particularly well adapted to the detection of insulating particles. The digital detection of ultralow concentrations of artificial entities such as polymer particles or biotargets such as proteins and bacteria represents an exceptional opportunity for sensing applications. In this review, we explore the latest development in the field of electrochemical blocking and propose some perspectives. 相似文献
59.
Dr. Marta Meneghello Dr. Christophe Léger Dr. Vincent Fourmond 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(70):17542-17553
Only two enzymes are capable of directly reducing CO2: CO dehydrogenase, which produces CO at a [NiFe4S4] active site, and formate dehydrogenase, which produces formate at a mononuclear W or Mo active site. Both metalloenzymes are very rapid, energy-efficient and specific in terms of product. They have been connected to electrodes with two different objectives. A series of studies used protein film electrochemistry to learn about different aspects of the mechanism of these enzymes (reactivity with substrates, inhibitors…). Another series focused on taking advantage of the catalytic performance of these enzymes to build biotechnological devices, from CO2-reducing electrodes to full photochemical devices performing artificial photosynthesis. Here, we review all these works. 相似文献
60.
Md Shahadat Hossan Mohammed Khaled Bin Break Tracey D. Bradshaw Hilary M. Collins Christophe Wiart Teng-Jin Khoo Ahmed Alafnan 《Molecules (Basel, Switzerland)》2021,26(8)
Cardamonin is a polyphenolic natural product that has been shown to possess cytotoxic activity against a variety of cancer cell lines. We previously reported the semi-synthesis of a novel Cu (II)–cardamonin complex (19) that demonstrated potent antitumour activity. In this study, we further investigated the bioactivity of 19 against MDA-MB-468 and PANC-1 cancer cells in an attempt to discover an effective treatment for triple-negative breast cancer (TNBC) and pancreatic cancer, respectively. Results revealed that 19 abolished the formation of MDA-MB-468 and PANC-1 colonies, exerted growth-inhibitory activity, and inhibited cancer cell migration. Further mechanistic studies showed that 19 induced DNA damage resulting in gap 2 (G2)/mitosis (M) phase arrest and microtubule network disruption. Moreover, 19 generated reactive oxygen species (ROS) that may contribute to induction of apoptosis, corroborated by activation of caspase-3/7, PARP cleavage, and downregulation of Mcl-1. Complex 19 also decreased the expression levels of p-Akt and p-4EBP1, which indicates that the compound exerts its activity, at least in part, via inhibition of Akt signalling. Furthermore, 19 decreased the expression of c-Myc in PANC-1 cells only, which suggests that it may exert its bioactivity via multiple mechanisms of action. These results demonstrate the potential of 19 as a therapeutic agent for TNBC and pancreatic cancer. 相似文献