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121.
Strain‐Induced Double Carbon–Carbon Bond Activations of Cycloparaphenylenes by a Platinum Complex: Application to the Synthesis of Cyclic Diketones 下载免费PDF全文
Dr. Eiichi Kayahara Toshiki Hayashi Dr. Katsuhiko Takeuchi Prof. Dr. Fumiyuki Ozawa Keita Ashida Prof. Dr. Sensuke Ogoshi Prof. Dr. Shigeru Yamago 《Angewandte Chemie (International ed. in English)》2018,57(35):11418-11421
The carbon–carbon (C?C) bond activation of [n]cycloparaphenylenes ([n]CPPs) by a transition‐metal complex is herein reported. The Pt0 complex Pt(PPh3)4 regioselectively cleaves two C?C σ bonds of [5] CPP and [6]CPP to give cyclic dinuclear platinum complexes in high yields. Theoretical calculations reveal that the relief of ring strain drives the reaction. The cyclic complex was further transformed into a cyclic diketone by using a CO insertion reaction. 相似文献
122.
Kazuaki Kuwata Rie Fujita Kengo Hanaya Shuhei Higashibayashi Takeshi Sugai 《Tetrahedron》2018,74(7):740-745
A formal total synthesis of (?)-hamigeran B was achieved in 17 steps from commercially available ethyl 2-oxocyclopentanecarboxylate. Carbonyl reductase-catalyzed asymmetric reduction and the subsequent chemical transformations furnished an enantiomerically pure synthetic intermediate, (R)-5-formyl-2-isopropyl-5-methylcyclopent-1-en-1-yl trifluoromethylsulfonate. Suzuki-Miyaura coupling with Gao's arylboronate [2-(2-formyl-3-methoxy-5-methylphenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane], under PdCl2(dppf)?CH2Cl2 catalysis, and the subsequent cyclization by way of intramolecular reductive SmI2-mediated 1,2-diol formation provided a tricyclic skeleton with a tetrasubstituted double bond between C-1 and C-9b. Upon hydrogenation of this double bond, the proper stereochemistry of the remaining chiral centers was established. Exclusive addition of the hydrogen atom from the β-face occurred, owing to the shielding of the α-face with a bulky TBS protective group on the C-4 alcohol. The hydrogenation products were transformed into Clive's synthetic precursor for (?)-hamigeran B. 相似文献
123.
Daisuke Sasaki Yasushi Okada Toshiki Hagiwara Takashi Sawaguchi 《Polymer Degradation and Stability》2007,92(2):271-279
It was found that telechelic isotactic oligo(1-butene) and telechelic oligo(propylene-ran-1-butene) could be isolated as nonvolatile oligomers from polymer residues resulting from the thermal degradation of isotactic poly(1-butene) and poly(propylene-ran-1-butene), respectively. Their structures were determined by 1H and 13C NMR with attention being paid to their reactive end groups. The maximum average number of terminal vinylidene groups per molecule (fTVD) was 1.8, indicating that about 80 mol% were α,ω-diene oligomers having two terminal vinylidene groups. This useful new telechelic oligomer had a lower polydispersity than the original polymer, in spite of its lower molecular weight and Tm. The composition of end groups of nonvolatile oligomers obtained by thermal degradation of poly(propylene-ran-1-butene) could be explained by the differences in bond dissociation energy and activation energy of elementary reactions during thermal degradation, based on the monomer composition of the original polymer. 相似文献
124.
Recent studies on electrochemical partial fluorination in ionic liquid fluoride salts are reviewed. At first, historical background and some problems of electrochemical fluorination in organic solvents are briefly mentioned. Solvent-free electrochemical fluorinations in ionic liquids are explained as follows. Ultrasonication was found to improve both the yield and current efficiency for electrochemical fluorination of α-phenylthioacetate, which is mainly attributable to marked mass transport promotion of the substrate and the suppression of anode passivation. Highly regioselective and efficient fluorination of cyclic ethers, lactones, and cyclic carbonate was achieved in Et4NF·4HF and Et3N·5HF. Selective fluorination of hardly oxidizable phthalide was realized using a combination of imidazolium and fluoride ionic liquids. The unique effect of imidazolium ionic liquids on electrochemical fluorodesulfurization of 3-phenylthiophthalide was explained. Reuse of ionic liquids for electrochemical fluorination is also possible. 相似文献
125.
126.
We have developed a novel electrolytic system based on the anion exchange reaction between KCl and Amberlyst A26. It was demonstrated by preparative electrolysis experiments as well as cyclic voltammetry that the anion exchange reaction offers a unique electrolytic system for electroreduction of organic compounds. On the basis of the electrolytic system, electroreduction of aromatic carbonyl compounds was successfully achieved by using an undivided cell to provide the corresponding coupling products as pinacols in good to high yields with high diastereoselectivity. 相似文献
127.
Hiromitsu Kiriyama Michiaki Mori Yoshiki Nakai Takuya Shimomura Manabu Tanoue Atushi Akutsu Hajime Okada Tomohiro Motomura Shuji Kondo Shuhei Kanazawa Akito Sagisaka Jinglong Ma Izuru Daito Hideyuki Kotaki Hiroyuki Daido Sergei Bulanov Toyoaki Kimura Toshiki Tajima 《Optics Communications》2009,282(4):625-2346
We demonstrate a high-contrast, high-intensity double chirped-pulse amplification (CPA) Ti:sapphire laser system using an optical parametric chirped-pulse (OPCPA) pre- amplifier. By injecting cleaned microjoule seed pulses into the OPCPA, a temporal contrast greater than 1010 within picosecond times before the main femtosecond pulse is demonstrated with an output pulse energy of 1.7 J and a pulse duration of 30 fs, corresponding to a peak power of 60 TW at a 10 Hz repetition rate. This system uses a cryogenically-cooled Ti:sapphire final amplifier and generates focused peak intensities in excess of 1020 W/cm2. 相似文献
128.
N. Kawamura K. Nagamine T. Matsuzaki K. Ishida S.N. Nakamura S. Sakamoto M. Iwasaki M. Tanase M. Kato K. Kurosawa T. Hashimoto H. Sugai K. Kudo N. Takeda G.H. Eaton 《Hyperfine Interactions》1999,118(1-4):213-215
This article reports the accumulation effect of the 3He originating from tritium β decay; 3He created in solid remains in it, while one in liquid diffuses and goes out to the vapor gas. We observed this effect through
the neutron detection from muon catalyzed fusion phenomenon (μCF), and gave it qualitative understanding, by which the muon
transfer rate from (dμ) and (tμ) to helium was derived.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
129.
S.N. Nakamura K. Nagamine T. Matsuzaki K. Ishida N. Kawamura S. Sakamoto M. Iwasaki M. Tanase M. Kato K. Kurosawa H. Sugai I. Watanabe K. Kudo N. Takeda G.H. Eaton 《Hyperfine Interactions》1999,118(1-4):209-212
At the RIKEN-RAL Muon Facility, μ- to α sticking K
β
X-rays were observed for the first time taking advantage of the pulsed beam structure. The precision of the present measurements
was insufficient to distinguish between theoretical models, however the observed K
β
/K
α
X-ray intensity ratio tends to be smaller than most of these theoretical predictions.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
130.