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141.
Crystal Structure of the Isopropylzinc Alkoxide of Pyrimidyl Alkanol: Mechanistic Insights for Asymmetric Autocatalysis with Amplification of Enantiomeric Excess 下载免费PDF全文
Dr. Arimasa Matsumoto Takaaki Abe Atsushi Hara Takayuki Tobita Taisuke Sasagawa Prof. Dr. Tsuneomi Kawasaki Prof. Dr. Kenso Soai 《Angewandte Chemie (International ed. in English)》2015,54(50):15218-15221
Asymmetric amplification during self‐replication is a key feature that is used to explain the origin of homochirality. Asymmetric autocatalysis of pyrimidyl alkanol in the asymmetric addition of diisopropylzinc to pyrimidine‐5‐carbaldehyde is a unique example of this phenomenon. Crystallization of zinc alkoxides of this 5‐pyrimidyl alkanol and single‐crystal X‐ray diffraction analysis of the alkoxide crystals reveal the existence of tetramer or higher oligomer structures in this asymmetric autocatalytic system. 相似文献
142.
Identification and Purification of the CPD Photolyase in Vibrio parahaemolyticus RIMD2210633 下载免费PDF全文
Kazuaki Mawatari Ping Tang Shuya He Takaaki Shimohata Yimou Wu Weidong Yin Akira Takahashi 《Photochemistry and photobiology》2015,91(5):1165-1172
Photoreactivation is an error‐free mechanism of DNA repair, utilized by prokaryotes and most eukaryotes and is catalyzed by specific enzymes called DNA photolyases. Photoreactivation has been reported in Vibrio parahaemolyticus WP28; however, information on photolyases in V. parahaemolyticus (V.p) strains has not been reported. This study examined the photoreactivation in V.p RIMD2210633. The photolyase responsible for repairing cyclobutane pyrimidine dimer (CPD) in DNA was identified, and the corresponding gene was determined as VPA1471. The protein was overexpressed in Escherichia coli and was purified for functional assessment in vitro. The mRNA level and protein expression level of this gene increased after ultraviolet A (UVA) illumination following ultraviolet C (UVC) irradiation. In vitro experiments confirmed that the protein encoded by VPA1471 could reduce the quantity of CPD in DNA. We designated the corresponding gene and protein of VPA1471 phr and Phr, respectively, although the function of two other photolyase/cryptochrome family members, VPA0203 and VPA0204, remains unclear. UV (ultraviolet) irradiation experiments suggest that these two genes possess some photorepairing ability. Therefore, we hypothesize that VPA0203 and VPA0204 encode (6‐4) photolyase in V. parahaemolyticus RIMD2210633. 相似文献
143.
Hiroki Hirai Kiichi Nakajima Soichiro Nakatsuka Kazushi Shiren Jingping Ni Shintaro Nomura Toshiaki Ikuta Takuji Hatakeyama 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(46):13785-13789
The development of a one‐step borylation of 1,3‐diaryloxybenzenes, yielding novel boron‐containing polycyclic aromatic compounds, is reported. The resulting boron‐containing compounds possess high singlet‐triplet excitation energies as a result of localized frontier molecular orbitals induced by boron and oxygen. Using these compounds as a host material, we successfully prepared phosphorescent organic light‐emitting diodes exhibiting high efficiency and adequate lifetimes. Moreover, using the present one‐step borylation, we succeeded in the synthesis of an efficient, thermally activated delayed fluorescence emitter and boron‐fused benzo[6]helicene. 相似文献
144.
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146.
Effects of inertia, surface tension and gravity in the constant force stretching of isothermal cylindrical filaments of Newtonian, power-law and Maxwell-type fluids were analysed in Lagrangian coordinates. Solution for the purely gravitational extension of Newtonian fluid cylinder was found to be as simple as = 1 – C
3
(1 – ) where designates the cross sectional area, the Lagrangian distance and the time. Analytical solutions were also available for the case of inertialess Newtonian and power-law fluids.A first-order backward differencing scheme and minimal computer time were sufficient to numerically analyse the constant force extension of Maxwell-type fluids in the presence of inertia, gravity and surface tension. Effects of inertia, surface tension and gravity on the severity of neck down occurring at either end of the filament are summarized in diagrams. The present approach is valid on any other constitutive model as far as there is a numerical scheme to analyse thehomogeneous extension of a cylinder of that particular fluid. 相似文献
147.
Kenji ArimitsuSayo Nomura Hiroki IwasakiMinoru Ozeki Masayuki Yamashita 《Tetrahedron letters》2011,52(52):7046-7048
The first total synthesis of (±)-adunctin B (1), a natural product isolated from Piper aduncum (Piperaceae) and having antibacterial activity, was achieved in 1.26% overall yield in 15 steps from 5,7-dimethoxycoumarin-3-carboxylate (8). 相似文献
148.
Kuniaki Tatsuta Sonoko TokishitaTomohiro Fukuda Takaaki KanoTadaaki Komiya Seijiro Hosokawa 《Tetrahedron letters》2011,52(9):983-986
K1115 B1, isolated from the broth of Streptomyces species, was found to be a mixture of stereoisomers. Authors synthesized all stereoisomers of K1115 B1 by convergent synthesis coupling a rhamnose derivative, an isobenzofuranone, and a chiral tetraol. Comparison of 1H NMR spectra and optical rotations made it clear that the absolute structures of K1115 B1α (the major isomer) and K1115 B1β (the minor isomer) were (1R, 17S)- and (1R, 17R)-configurations, respectively. The optical rotations of the stereoisomers revealed that alnumycin, reported as the identical structure with K1115 B1, might be another mixture of stereoisomers. 相似文献
149.
Mitsushiro Nomura Chikako Fujita-Takayama 《Journal of organometallic chemistry》2011,696(25):4018-4038
This review paper summarizes the reactivities of metal dithiolene complexes based on the ‘coexistence of aromaticity and unsaturation’ in the five-membered metallacycle, the so-called metalladithiolene ring (MS2C2). The 16-electron [LM(dithiolene)] (LM = CpMIII, Cp*MIII, (C6R6)MII) complexes are coordinatively unsaturated and usually show M-S centered cycloaddition reactions with nucleophiles (e.g. diazoalkanes, organic azides, quadricyclane) and electrophiles (e.g. tetracyanoethylene oxide, activated acetylene). The resulting metalladithiolene cycloadducts, which have three-membered M-S-C or M-S-N rings, further react with protic acids or PR3 to undergo the ring-opening reactions involving the M-C bond, M-S bond or M-N bond cleavages. Furthermore, diverse adduct dissociations are observed by thermal, photochemical or electrochemical redox reactions. Such reactions normally produce the original [LM(dithiolene)] complexes (non-adduct) and the eliminated fragments. Among them, the Co-S centered imido adduct [CpCo(dithiolene)(NR)] (R = Ts, Ms) reacted under thermal conditions in the presence of PR3 to undergo the intramolecular imido migration reaction to the Cp ligand, giving [(C5H4-NHR)Co(dithiolene)] complexes. The M-S centered multinuclear cluster complexes are obtained by the reaction of [LM(dithiolene)] with low valent M(CO)n complexes. The square-planar bis(dithiolene) complexes [M(dithiolene)2]0 (M = Ni, Pd, Pt) or tris(dithiolene) complexes [M(dithiolene)3]0 yield cycloaddition products with olefins. These reactions are due to ligand centered reactions made possible by a molecular orbital overlap between dithiolene LUMO and olefin HOMO. Similar ligand centered adducts are obtained by the reaction of dianionic [M(dithiolene)2]2− with haloalkanes or dihaloalkanes. Also these adducts of bis(dithiolene) complex are dissociated photochemically and electrochemically. This paper also describes the reactivities of organometallic o-carborane dithiolate complexes, which are generally formulated as [LM(S2C2B10H10)] (LM = CpCo, Cp*Rh, Cp*Ir, (p-cymene)Ru and (p-cymene)Os). Diverse addition reactions are reported; in particular, the reaction with acetylene involves B-H bond activation in the carborane moiety. 相似文献
150.
Keiichiro Ishikawa Nobuyasu Hanari Yoshitaka Shimizu Toshihide Ihara Akira Nomura Masahiko Numata Takashi Yarita Kenji Kato Koichi Chiba 《Accreditation and quality assurance》2011,16(6):311-322
Purity assay of high-purity materials (HPMs) of phthalic acid esters (PAEs) was carried out by means of a mass balance method.
In this method, chromatographic methods such as gas chromatography-flame ionization detector (GC-FID) and/or high-performance
liquid chromatography (HPLC) in combination with other methods such as Karl-Fischer (KF) titration and vacuum evaporation
(VE) were applied. The sum of the impurities estimated by these methods allowed the estimation of the purity of the main component
by difference. Seven PAEs with varying side chain structures and levels of impurities were analysed on a systematic way in
which impurities were classified into several groups in terms of their abundance, availability of qualitative information
and availability of authentic compounds, etc. The absolute quantity of each impurity was determined by GC-FID and/or HPLC
based on the calibration made by the authentic compounds of impurities whenever available. The purities in mass fraction of
these PAEs were certified at the National Metrology Institute of Japan (NMIJ), and the PAEs were registered as primary reference
materials playing an essential role in linking the metrological traceability of the Japan Calibration Service System (JCSS)
to the International System of Units (SI). 相似文献