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排序方式: 共有1300条查询结果,搜索用时 15 毫秒
991.
Hideaki Tsubaki Atsushi Sugawara Hiroyuki Takeda Bobak Gholamkhass Kazuhide Koike Osamu Ishitani 《Research on Chemical Intermediates》2007,33(1-2):37-48
Photocatalysis of biscarbonylrhenium complexes cis,trans-[Re(dmbpy)(CO)2(PR3) (PR′3)]+ (dmbpy=4,4′-dimethyl-2,2′-bipyridine: R, R′=Ph (1a +); p-FPh (1b +); R=Ph, R′=OEt (1c +); R, R′=O-i-Pr (1d +)) is reported for the first time. The rhenium complexes with two triarylphosphine ligands (1a +, 1b +) efficiently photocatalyzed CO2 reduction with triethanolamine as a sacrificial donor. On the other hand, the complexes with one or two trialkylphosphite ligand(s) (1c +, 1d +) had low photocatalytic abilities under the same reaction conditions. 相似文献
992.
993.
Kiriyama H Mori M Nakai Y Yamamoto Y Tanoue M Akutsu A Shimomura T Kondo S Kanazawa S Daido H Kimura T Miyanaga N 《Optics letters》2007,32(16):2315-2317
We describe a compact, reliable, high-power, and high-contrast noncollinear optical parametric chirped-pulse amplifier system. With a broadband Ti:sapphire oscillator and grating-based stretching and compression, the chirped pulses are amplified from 0.1 nJ to 122 mJ in type I beta-barium borate optical parametric chirped-pulse amplifiers with a total gain of over 10(9) at 10 Hz repetition rate. Pulse compression down to 19-fs duration achieved after amplification indicates a peak power of 3.2 TW at an average power of 0.62 W. The prepulse contrast is measured to be less than 10(-8) on picosecond time scales. 相似文献
994.
Akutagawa T Sato D Koshinaka H Aonuma M Noro S Takeda S Nakamura T 《Inorganic chemistry》2008,47(13):5951-5962
Supramolecular rotators of hydrogen-bonding assemblies between anilinium (Ph-NH 3 (+)) or adamantylammonium (AD-NH 3 (+)) and dibenzo[18]crown-6 (DB[18]crown-6) or meso-dicyclohexano[18]crown-6 (DCH[18]crown-6) were introduced into [Ni(dmit) 2] salts (dmit (2-) is 2-thioxo-1,3-dithiole-4,5-dithiolate). The ammonium moieties of Ph-NH 3 (+) and AD-NH 3 (+) cations were interacted through N-H (+) approximately O hydrogen bonding with the six oxygen atoms of crown ethers, forming 1:1 supramolecular rotator-stator structures. X-ray crystal-structure analyses revealed a jackknife-shaped conformation of DB[18]crown-6, in which two benzene rings were twisted along the same direction, in (Ph-NH 3 (+))(DB[18]crown-6)[Ni(dmit) 2] (-) ( 1) and (AD-NH 3 (+))(DB[18]crown-6)[Ni(dmit) 2] (-) ( 3), whereas the conformational flexibility of two dicyclohexyl rings was observed in (Ph-NH 3 (+))(DCH[18]crown-6)[Ni(dmit) 2] (-) ( 2) and (AD-NH 3 (+))(DCH[18]crown-6)[Ni(dmit) 2] (-) ( 4). Sufficient space for the molecular rotation of the adamantyl group was achieved in the crystals of salts 3 and 4, whereas the rotation of the phenyl group in salts 1 and 2 was rather restricted by the nearest neighboring molecules. The rotation of the adamantyl group in salts 3 and 4 was evidenced from the temperature-dependent wide-line (1)H NMR spectra, dielectric properties, and X-ray crystal structure analysis. ab initio calculations showed that the potential energy barriers for the rotations of adamantyl groups in salts 3 (Delta E approximately 18 kJmol (-1)) and 4 (Delta E approximately 15 kJmol (-1)) were similar to those of ethane ( approximately 12 kJmol (-1)) and butane (17-25 kJmol (-1)) around the C-C single bond, which were 1 order of magnitude smaller than those of phenyl groups in salts 1 (Delta E approximately 180 kJmol (-1)) and 2 (Delta E approximately 340 kJmol (-1)). 1D or 2D [Ni(dmit) 2] (-) anion arrangements were observed in the crystals according to the shape of crown ether derivatives. The 2D weak intermolecular interactions between [Ni(dmit) 2] (-) anions in salts 1 and 3 led to Curie-Weiss behavior with weak antiferromagnetic interaction, whereas 1D interactions through lateral sulfur-sulfur atomic contacts between [Ni(dmit) 2] (-) anions were observed in salts 2 and 4, whose magnetic behaviors were dictated by ferromagnetic (salt 2) and singlet-triplet (salt 4) intermolecular magnetic interactions, respectively. 相似文献
995.
feasible new preparation was reported for an octacarboxylphenyl functionalized spherosilicate, octakis[(pcarboxyphenyl) dimethylsilyl]silicate, which was a versatile monomer leading to other functional spherosilicate derivatives. The synthesis was started from octakis[dimethyl(p-methylphenyl)silyl]silicate. Octakis[dimethyl(pmethylphenyl) silyl]silicate was brominated by NBS to produce octakis[dimethyl(4-tribromomethylphenyl)silyl]silicate. Finally, octakis[dimethyl(4-tribromomethylphenyl)silyl]silicate was hydrolyzed in the presence of AgNO3 and formic acid to give the desired compound. Octakis[(pcarboxyphenyl) dimethylsilyl]silicate was fully characterized by FTIR, 1H NMR, 13C NMR, 29Si NMR spectra, ESI-MS, and elemental analysis. 相似文献
996.
A simple and sensitive method for the determination of nanomolar levels of hydrogen peroxide (H2O2) in seawater has been developed and validated. This method is based on the reduction of H2O2 by ferrous iron in acid solution to yield hydroxyl radical (OH) which reacts with benzene to produce phenol. Phenol is separated from the reaction mixture by reversed phase high performance liquid chromatography and its fluorescence intensity signals were measured at excitation and emission of 270 and 298 nm, respectively. Under optimum conditions, the calibration curve exhibited linearity in the range of (0-50) × 103 nmol L−1 H2O2. The relative standard deviations for five replicate measurements of 500 and 50 nmol L−1 H2O2 are 1.9 and 2.4%, respectively. The detection limit for H2O2, defined as three times the standard deviation of the lowest standard solution (5 nmol L−1 H2O2) in seawater is 4 nmol L−1. Interference of nitrite ion (NO2−) on the fluorescence intensity of phenol was also investigated. The result indicated that the addition of 10 μmol L−1 NO2− to seawater samples showed no significant interference, although, the addition of 50 μmol L−1 NO2− to the seawater samples decreases the fluorescence intensity signals of phenol by almost 40%. Intercomparison of this method with well-accepted (p-hydroxyphenyl) acetic acid (POHPAA)-FIA method shows excellent agreement. The proposed method has been applied on-board analysis of H2O2 in Seto Inland seawater samples. 相似文献
997.
Hiroyuki Morita Shintaro Tashiro Masahiro Takeda Ken Fujimori Nobuhiko Yamada Md. Chanmiya Sheikh Hiroyuki Kawaguchi 《Tetrahedron》2008,64(16):3589-3595
We have synthesized α-(phosphoryl)methyl tetrazolyl sulfoxides and examined the reactivities in the thermolyses and in the presence of several amines, such as aniline, benzylamine, piperidine, pyrrolidine, and morpholine. Thermolyses of the derivatives in the presence of 2,3-dimethyl-1,3-butadiene afforded 2-phosphoryl substituted 4,5-dimethyl-3,6-dihydro-2H-thiopyran S-oxide. In addition, novel phosphinecarbothioamides were obtained in the reaction of the derivatives with amines. 相似文献
998.
Photoexcited Carrier Transfer in CuInS2 Nanocrystal Assembly by Suppressing Resonant-Energy Transfer
Prof. Dr. Yasushi Hamanaka Satoshi Okuyama Rin Yokoi Dr. Toshihiro Kuzuya Dr. Keiki Takeda Prof. Dr. Chihiro Sekine 《Chemphyschem》2023,24(21):e202300029
High-density assemblies or superlattice structures composed of colloidal semiconductor nanocrystals have attracted attention as key materials for next-generation photoelectric conversion devices such as quantum-dot solar cells. In these nanocrystal solids, unique transport and optical phenomena occur due to quantum coupling of localized energy states, charge-carrier hopping, and electromagnetic interactions among closely arranged nanocrystals. In particular, the photoexcited carrier dynamics in nanocrystal solids is important because it significantly affects various device parameters. In this study, we report the photoexcited carrier dynamics in a solid film of CuInS2 nanocrystals, which is one of the potential nontoxic substitutes with Cd- and Pb-free compositions. Meanwhile, these subjects have been extensively studied in nanocrystal solids formed by CdSe and PbS systems. A carrier-hopping mechanism was confirmed using temperature-dependent photoluminescence spectroscopy, which yielded a typical value of the photoexcited carrier-transfer rate of (2.2±0.6)×107 s−1 by suppressing the influence of the excitation-energy transfer. 相似文献
999.
Enantioselective Addition of a 2‐Alkoxycarbonyl‐1,3‐dithiane to Imines Catalyzed by a Bis(guanidino)iminophosphorane Organosuperbase
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Dr. Azusa Kondoh Masafumi Oishi Tadahiro Takeda Prof. Dr. Masahiro Terada 《Angewandte Chemie (International ed. in English)》2015,54(52):15836-15839
A chiral bis(guanidino)iminophosphorane catalyzes enantioselective addition reactions of a 1,3‐dithiane derivative as a pronucleophile. The chiral uncharged organosuperbase facilitates the addition of benzyloxycarbonyl‐1,3‐dithiane to aromatic N‐Boc‐protected imines to provide optically active α‐amino‐1,3‐dithiane derivatives, which are valuable versatile building blocks in organic synthesis. 相似文献
1000.
H Tatebe G Goshima K Takeda T Nakagawa K Kinoshita M Yanagida 《Micron (Oxford, England : 1993)》2001,32(1):67-74
The fission yeast Schizosaccharomyces pombe has been used as a model organism to study cell cycle control and dynamic chromosome behavior during anaphase segregation as genetic and cytological approaches are easily amenable. To understand the role of gene products involved in these cellular events, it is important to determine intracellular localization of each gene product during the cell cycle. In this article, visualization in living cells of several gene products involved in cell cycle control and sister chromatid separation is described. The genes tagged with jellyfish green fluorescent protein (GFP) include sad1(+) (encoding a spindle pole body (SPB) protein), atb2(+) (alpha-tubulin), mis6(+) (a kinetochore protein), eat1(+) (a novel actin-like protein localized in the nucleus) and cdc13(+) (a mitotic cyclin). In addition, LacI which is bound to a DNA segment containing LacO repeat sequences integrated near the centromere (cen1) is visualized. These are useful to monitor cell cycle events in living cells. 相似文献