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951.
Protonation Switching to the Least‐Basic Heteroatom of Carbamate through Cationic Hydrogen Bonding Promotes the Formation of Isocyanate Cations
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Hiroaki Kurouchi Akinari Sumita Prof. Dr. Yuko Otani Prof. Dr. Tomohiko Ohwada 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(28):8682-8690
We found that phenethylcarbamates that bear ortho‐salicylate as an ether group (carbamoyl salicylates) dramatically accelerate O?C bond dissociation in strong acid to facilitate generation of isocyanate cation (N‐protonated isocyanates), which undergo subsequent intramolecular aromatic electrophilic cyclization to give dihydroisoquinolones. To generate isocyanate cations from carbamates in acidic media as electrophiles for aromatic substitution, protonation at the ether oxygen, the least basic heteroatom, is essential to promote C?O bond cleavage. However, the carbonyl oxygen of carbamates, the most basic site, is protonated exclusively in strong acids. We found that the protonation site can be shifted to an alternative basic atom by linking methyl salicylate to the ether oxygen of carbamate. The methyl ester oxygen ortho to the phenolic (ether) oxygen of salicylate is as basic as the carbamate carbonyl oxygen, and we found that monoprotonation at the methyl ester oxygen in strong acid resulted in the formation of an intramolecular cationic hydrogen bond (>C?O+?H???O<) with the phenolic ether oxygen. This facilitates O?C bond dissociation of phenethylcarbamates, thereby promoting isocyanate cation formation. In contrast, superacid‐mediated diprotonation at the methyl ester oxygen of the salicylate and the carbonyl oxygen of the carbamate afforded a rather stable dication, which did not readily undergo C?O bond dissociation. This is an unprecedented and unknown case in which the monocation has greater reactivity than the dication. 相似文献
952.
Hiroaki Yonemura Ippei Sakamoto Sunao Yamada 《Molecular Crystals and Liquid Crystals》2015,620(1):64-70
The fabrication of copper phthalocyanine (CuPc)–gold nanorod (AuNR) composite films on indium-tin-oxide electrodes was performed by electrostatic layer-by-layer adsorption technique. The photocurrents in CuPc–AuNR composite films were larger than those in CuPc films as a reference. The enhancements of the photocurrents in CuPc–AuNR composite films due to AuNR increased with increasing of wavelength up to near-infrared region. The enhancements are attributable to localized surface plasmon resonance (LSPR) due to AuNR. The enhancements at near-infrared wavelength due to the longitudinal LSPR were larger than those at visible wavelength due to the transverse LSPR. 相似文献
953.
Visible‐Light‐Induced Electron Transport from Small to Large Nanoparticles in Bimodal Gold Nanoparticle‐Loaded Titanium(IV) Oxide
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Dr. Shin‐ichi Naya Tadahiro Niwa Takahiro Kume Prof. Dr. Hiroaki Tada 《Angewandte Chemie (International ed. in English)》2014,53(28):7305-7309
A key to realizing the sustainable society is to develop highly active photocatalysts for selective organic synthesis effectively using sunlight as the energy source. Recently, metal‐oxide‐supported gold nanoparticles (NPs) have emerged as a new type of visible‐light photocatalysts driven by the excitation of localized surface plasmon resonance of Au NPs. Here we show that visible‐light irradiation (λ>430 nm) of TiO2‐supported Au NPs with a bimodal size distribution (BM‐Au/TiO2) gives rise to the long‐range (>40 nm) electron transport from about 14 small (ca. 2 nm) Au NPs to one large (ca. 9 nm) Au NP through the conduction band of TiO2. As a result of the enhancement of charge separation, BM‐Au/TiO2 exhibits a high level of visible‐light activity for the one‐step synthesis of azobenzenes from nitrobenzenes at 25 °C with a yield greater than 95 % and a selectivity greater than 99 %, whereas unimodal Au/TiO2 (UM‐Au/TiO2) is photocatalytically inactive. 相似文献
954.
Plasmon‐Assisted Water Splitting Using Two Sides of the Same SrTiO3 Single‐Crystal Substrate: Conversion of Visible Light to Chemical Energy
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Yuqing Zhong Prof. Kosei Ueno Yuko Mori Dr. Xu Shi Dr. Tomoya Oshikiri Prof. Kei Murakoshi Prof. Haruo Inoue Prof. Hiroaki Misawa 《Angewandte Chemie (International ed. in English)》2014,53(39):10350-10354
A plasmon‐induced water splitting system that operates under irradiation by visible light was successfully developed; the system is based on the use of both sides of the same strontium titanate (SrTiO3) single‐crystal substrate. The water splitting system contains two solution chambers to separate hydrogen (H2) and oxygen (O2). To promote water splitting, a chemical bias was applied by regulating the pH values of the chambers. The quantity of H2 evolved from the surface of platinum, which was used as a reduction co‐catalyst, was twice the quantity of O2 evolved from an Au‐nanostructured surface. Thus, the stoichiometric evolution of H2 and O2 was clearly demonstrated. The hydrogen‐evolution action spectrum closely corresponds to the plasmon resonance spectrum, indicating that the plasmon‐induced charge separation at the Au/SrTiO3 interface promotes water oxidation and the subsequent reduction of a proton on the backside of the SrTiO3 substrate. The chemical bias is significantly reduced by plasmonic effects, which indicates the possibility of constructing an artificial photosynthesis system with low energy consumption. 相似文献
955.
Size‐Dependent Thermochromism through Enhanced Electron–Phonon Coupling in 1 nm Quantum Dots
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Haruna Tamaki Dr. Hiroto Watanabe Sachiko Kamiyama Dr. Yuya Oaki Prof. Dr. Hiroaki Imai 《Angewandte Chemie (International ed. in English)》2014,53(40):10706-10709
1 nm CuO quantum dots (QDs) were produced in size‐controlled super‐micropores of a silica matrix. The reversible color change of the QDs from pale blue to deep green was clearly observed in a wide temperature range from 298 to 673 K. This particular thermochromism is ascribed to an enhanced bandgap shift depending on temperature with a strong electron–phonon coupling in the confined space of the 1 nm QDs. 相似文献
956.
Masashi Shigenobu Kazuhiro Takenaka Hiroaki Sasai 《Angewandte Chemie (International ed. in English)》2015,54(33):9572-9576
A palladium‐catalyzed direct arylation of isoxazoles with aryl iodides has been achieved. The C H bond at the 5‐position is activated selectively to give coupling products in moderate to good yields. This direct arylation was applied to the synthesis of a spiro‐type chiral ligand, which proved to be most effective to the palladium‐catalyzed tandem cyclization of a dialkenyl alcohol. 相似文献
957.
Wataru Yoshida Aki Kezuka Yoshiyuki Murakami Jinhee Lee Koichi Abe Hiroaki Motoki Takafumi Matsuo Nobuaki Shimura Mamoru Noda Shizunobu Igimi Kazunori Ikebukuro 《Analytica chimica acta》2013
An automatic polymerase chain reaction (PCR) product detection system for food safety monitoring using zinc finger (ZF) protein fused to luciferase was developed. ZF protein fused to luciferase specifically binds to target double stranded DNA sequence and has luciferase enzymatic activity. Therefore, PCR products that comprise ZF protein recognition sequence can be detected by measuring the luciferase activity of the fusion protein. We previously reported that PCR products from Legionella pneumophila and Escherichia coli (E. coli) O157 genomic DNA were detected by Zif268, a natural ZF protein, fused to luciferase. In this study, Zif268–luciferase was applied to detect the presence of Salmonella and coliforms. Moreover, an artificial zinc finger protein (B2) fused to luciferase was constructed for a Norovirus detection system. In the luciferase activity detection assay, several bound/free separation process is required. Therefore, an analyzer that automatically performed the bound/free separation process was developed to detect PCR products using the ZF–luciferase fusion protein. By means of the automatic analyzer with ZF–luciferase fusion protein, target pathogenic genomes were specifically detected in the presence of other pathogenic genomes. Moreover, we succeeded in the detection of 10 copies of E. coli BL21 without extraction of genomic DNA by the automatic analyzer and E. coli was detected with a logarithmic dependency in the range of 1.0 × 10 to 1.0 × 106 copies. 相似文献
958.
N-Alkyl-N-arylthiocarbamoylacetates, the key intermediates for the synthesis of novel antinephritic agents, have been prepared for the first time. Some of the esters were in turn hydrolyzed to the corresponding acids. An alternative, indirect synthetic route was also developed to prepare some unusual acids. 相似文献
959.
Hiroaki Kawasaki Kazunari Taira 《Phosphorus, sulfur, and silicon and the related elements》2013,188(6-7):1645-1649
Artificial protein-RNA hybrid ribozymes with an unwinding activity were created. Since the novel hybrid ribozymes can attack any site within mRNA, libraries can be made of the hybrid ribozymes with randomized binding arms and thus be introduced into cells. This represents a new paradigm of powerful ribozyme technology that can enjoy many unique and exciting uses for various purposes in the post-genome project era, including applications for discovery of novel functional genes associated with specific important phenotypes and targeted elimination of expression of disease-causing genes in vivo in gene therapy approaches. 相似文献
960.
Hiroto Tamura Yudai Hotta Hiroaki Sato 《Journal of the American Society for Mass Spectrometry》2013,24(8):1185-1193
Matrix-assisted laser-desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is one of the most widely used mass-based approaches for bacterial identification and classification because of the simple sample preparation and extremely rapid analysis within a few minutes. To establish the accurate MALDI-TOF MS bacterial discrimination method at strain level, the ribosomal subunit proteins coded in the S10-spc-alpha operon, which encodes half of the ribosomal subunit protein and is highly conserved in eubacterial genomes, were selected as reliable biomarkers. This method, named the S10-GERMS method, revealed that the strains of genus Pseudomonas were successfully identified and discriminated at species and strain levels, respectively; therefore, the S10-GERMS method was further applied to discriminate the pathovar of P. syringae. The eight selected biomarkers (L24, L30, S10, S12, S14, S16, S17, and S19) suggested the rapid discrimination of P. syringae at the strain (pathovar) level. The S10-GERMS method appears to be a powerful tool for rapid and reliable bacterial discrimination and successful phylogenetic characterization. In this article, an overview of the utilization of results from the S10-GERMS method is presented, highlighting the characterization of the Lactobacillus casei group and discrimination of the bacteria of genera Bacillus and Sphingopyxis despite only two and one base difference in the 16S rRNA gene sequence, respectively. Figure
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