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171.
H. Imura H. Sakamoto K. Ohashi T. Shirasaki K. Oishi 《Journal of Radioanalytical and Nuclear Chemistry》1997,220(2):191-193
A novel analytical method, the substoichiometric isotope dilution mass spectrometry (SIDMS) has been proposed. This method consists of the substoichiometric separation of the element in question and the subsequent intensity measurement of a stable isotope of the element with a mass spectrometer. In SIDMS, the correction of the mass discrimination of isotope measurement is not necessary and the use of expensive enriched stable isotopes may be avoided. The validity and the usefulness of SIDMS are demonstrated by the substoichiometric extraction of iron(III) with 4-isopropyltropolone and 3,5-dichlorophenol following microwave-induced plasma mass spectrometry. 相似文献
172.
173.
Illudin S (lampterol) 总被引:1,自引:0,他引:1
174.
Transition metal complexes coordinated by an NAD(P)H model compound and their enhanced hydride-donating abilities in the presence of a base 总被引:1,自引:0,他引:1
Kobayashi A Konno H Sakamoto K Sekine A Ohashi Y Iida M Ishitani O 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(14):4219-4226
The ruthenium(II) and rhenium(I) complexes containing an NAD(P)H model compound, 1-benzyl-1,4-dihydronicotinamide (BNAH), as ligand, [Ru(tpy)(bpy)(BNAH)]2+ (1 a) and [Re(bpy)(CO)3(BNAH)]+ (1 b), were quantitatively produced by the reaction of the corresponding metal hydrido complexes with BNA(+) (1-benzylnicotinamidium cation). In the presence of base with pK(a) = 8.9, 1 a and 1 b have much greater reducing power than "free" BNAH. The oxidation potentials of 1 a in the absence and the presence of triethylamine were 0.55 V and -0.04 V, respectively, versus Ag/AgNO(3), whereas that of "free" BNAH was 0.30 V. Spectroscopic results clearly showed that the base extracts a proton from the carbamoyl group on 1 a and 1 b to give the deprotonated BNAH coordinating to the transition-metal complexes [Ru(tpy)(bpy)(BNAH-H+)]+ (3 a) and [Re(bpy)(CO)3(BNAH-H+)] (3 b); this deprotonation underlies the enhancement in reducing ability. The deprotonated forms 3 a and 3 b can efficiently reduce other NAD(P) models to give the corresponding 1,4-dihydro form, resulting in the deprotonated BNA+ being coordinated to the metal complexes [Ru(tpy)(bpy)(BNA(+)-H+)]2+ (2 a) and [Re(bpy)(CO)3(BNA+-H+)]+ (2 b); "free" BNAH and the protonated adducts 1 a and 1 b cannot act in this way. X-ray crystallography was performed on the PF6- salt of 2 a, and showed that the deprotonated nitrogen atom on the carbamoyl group coordinates to the ruthenium(II) metal center with a bond length of 2.086(3) Angstroms. Infrared spectral data suggested that the deprotonated carbamoyl group on the reduced forms 3 a and 3 b is converted to the imido group, and that the oxygen atom coordinates to the metal center. 相似文献
175.
Katsuyuki Ogura Shigeyuki Itoh Kazumasa Takahashi Hirotada Iida 《Tetrahedron letters》1986,27(52):6381-6384
Irradiation of an aldehyde dithioacetal S-oxide gives the corresponding aldehyde. The mechanism of this photochemical transformation is discussed and its application to organic synthesis is also described. 相似文献
176.
177.
Dr. Masaki Yoshida Dr. Mio Kondo Sena Torii Prof. Ken Sakai Prof. Shigeyuki Masaoka 《Angewandte Chemie (International ed. in English)》2015,54(27):7981-7984
Rational molecular design of catalytic systems capable of smooth O? O bond formation is critical to the development of efficient catalysts for water oxidation. A new ruthenium complex was developed, which bears pendant SO3? groups in the secondary coordination sphere: [Ru(terpy)(bpyms)(OH2)] (terpy=2,2′:6′,2′′‐terpyridine, bpyms=2,2′‐bipyridine‐5,5′‐bis(methanesulfonate)). Water oxidation driven by a Ce4+ oxidant is distinctly accelerated upon introduction of the pendant SO3? groups in comparisons to the parent catalyst, [Ru(terpy)(bpy)(OH2)]2+ (bpy=2,2′‐bipyridine). Spectroscopic, electrochemical, and crystallographic investigations concluded that the pendant SO3? groups promote the formation of an O? O bond via the secondary coordination sphere on the catalyst, whereas the influence of the pendant SO3? groups on the electronic structure of the [Ru(terpy)(bpy)(OH2)]2+ core is negligible. The results of this work indicate that modification of the secondary coordination sphere is a valuable strategy for the design of water oxidation catalysts. 相似文献
178.
Synthesis of Cyclobutenes and Allenes by Cobalt‐Catalyzed Cross‐Dimerization of Simple Alkenes with 1,3‐Enynes 下载免费PDF全文
Akira Nishimura Eri Tamai Dr. Masato Ohashi Prof. Dr. Sensuke Ogoshi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(22):6613-6617
Cobalt‐catalyzed cross‐dimerization of simple alkenes with 1,3‐enynes is reported. A [2+2] cycloaddition reaction occurred, with alkenes bearing no allylic hydrogen, by reductive elimination of a η3‐butadienyl cobaltacycle. On the other hand, aliphatic alkenes underwent 1,4‐hydroallylation by means of exo‐cyclic β‐H elimination. These reactions can provide cyclobutenes and allenes that were previously difficult to access, from simple substrates in a highly chemo‐ and regioselective manner. 相似文献
179.
Dr. Hiroyuki Takeda Dr. Masataka Ohashi Dr. Yasutomo Goto Dr. Tetsu Ohsuna Dr. Takao Tani Dr. Shinji Inagaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(29):9130-9136
An organic‐based photocatalysis system for water oxidation, with visible‐light harvesting antennae, was constructed using periodic mesoporous organosilica (PMO). PMO containing acridone groups in the framework (Acd‐PMO), a visible‐light harvesting antenna, was supported with [RuII(bpy)32+] complex (bpy=2,2′‐bipyridyl) coupled with iridium oxide (IrOx) particles in the mesochannels as photosensitizer and catalyst, respectively. Acd‐PMO absorbed visible light and funneled the light energy into the Ru complex in the mesochannels through excitation energy transfer. The excited state of Ru complex is oxidatively quenched by a sacrificial oxidant (Na2S2O8) to form Ru3+ species. The Ru3+ species extracts an electron from IrOx to oxidize water for oxygen production. The reaction quantum yield was 0.34 %, which was improved to 0.68 or 1.2 % by the modifications of PMO. A unique sequence of reactions mimicking natural photosystem II, 1) light‐harvesting, 2) charge separation, and 3) oxygen generation, were realized for the first time by using the light‐harvesting PMO. 相似文献
180.
High‐Throughput Development of a Hybrid‐Type Fluorescent Glutamate Sensor for Analysis of Synaptic Transmission 下载免费PDF全文
Dr. Kenji Takikawa Dr. Daisuke Asanuma Dr. Shigeyuki Namiki Hirokazu Sakamoto Tetsuro Ariyoshi Naoya Kimpara Prof. Kenzo Hirose 《Angewandte Chemie (International ed. in English)》2014,53(49):13439-13443
Fluorescent sensors are powerful tools for visualizing cellular molecular dynamics. We present a high‐throughput screening system, designated hybrid‐type fluorescence indicator development (HyFInD), to identify optimal position‐specific fluorophore labeling in hybrid‐type sensors consisting of combinations of ligand‐binding protein mutants with small molecular fluorophores. We screened sensors for glutamate among hybrid molecules obtained by the reaction of four cysteine‐reactive fluorescence probes with a set of cysteine‐scanning mutants of the 274 amino acid S1S2 domain of AMPA‐type glutamate receptor GluA2 subunit. HyFInD identified a glutamate‐responsive probe (enhanced glutamate optical sensor: eEOS) with a dynamic range >2400 %, good photostability, and high selectivity. When eEOS was specifically tethered to neuronal surfaces, it reliably visualized the spatiotemporal dynamics of glutamate release at single synapses, revealing synapse‐to‐synapse heterogeneity of short‐term plasticity. 相似文献