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51.
Experimental investigation on tunnel sonic boom 总被引:1,自引:0,他引:1
Upon the entrance of a high-speed train into a relatively long train tunnel, compression waves are generated in front of the train. These compression waves subsequently coalesce into a weak shock wave so that a unpleasant sonic boom is emitted from the tunnel exit. In order to investigate the generation of the weak shock wave in train tunnels and the emission of the resulting sonic boom from the train tunnel exit and to search for methods for the reduction of these sonic booms, a 1300 scaled train tunnel simulator was constructed and simulation experiments were carried out using this facility.In the train tunnel simulator, an 18 mm dia. and 200 mm long plastic piston moves along a 40 mm dia. and 25 m long test section with speed ranging from 60 to 100 m/s. The tunnel simulator was tilted 8° to the floor so that the attenuation of the piston speed was not more than 10 % of its entrance speed. Pressure measurements along the tunnel simulator and holographic interferometric optical flow visualization of weak shock waves in the tunnel simulator clearly showed that compression waves, with propagation, coalesced into a weak shock wave. Although, for reduction of the sonic boom in prototype train tunnels, the installation of a hood at the entrance of the tunnels was known to be useful for their suppression, this effect was confirmed in the present experiment and found to be effective particularly for low piston speeds. The installation of a partially perforated wall at the exit of the tunnel simulator was found to smear pressure gradients at the shock. This effect is significant for higher piston speeds. Throughout the series of train tunnel simulator experiments, the combination of both the entrance hood and the perforated wall significantly reduces shock overpressures for piston speeds ofu
p
ranging from 60 to 100 m/s. These experimental findings were then applied to a real train tunnel and good agreement was obtained between the tunnel simulator result and the real tunnel measurements. 相似文献
52.
53.
Takashi Nishikazea Mitsuo Takayama 《Journal of the American Society for Mass Spectrometry》2010,21(12):1979-1988
Although conventional N-Cα bond cleavage in electron capture dissociation (ECD) of multiply-charged peptides generates a complementary
c′ and z′ fragment pair, the N-Cα cleavage followed by hydrogen transfer from c′ to z′ fragments produces other fragments,
namely c′ and z′. In this study, the influence of charge state and amino acid composition on hydrogen transfer in ECD is described
using sets of peptides. Hydrogen transferred ionic species such as c′ and z′ were observed in ECD spectra of doubly-protonated
peptides, while the triply-protonated form did not demonstrate hydrogen transfer. The extent of hydrogen transfer in ECD of
doubly-protonated peptides was dependent on constituent amino acids. The ECD of doubly-protonated peptides possessing numerous
basic sites showed extensive hydrogen transfer compared with ECD of less basic peptides. The extent of hydrogen transfer is
discussed from the viewpoints of the structure of peptide ions, the possibility of internal hydrogen bonding and intermediate
lifetime of complex [c′+z′]. 相似文献
54.
We have performed high-resolution spin- and angle-resolved photoemission spectroscopy of bismuth thin film on Si(111) to investigate the spin structure of surface states. Unlike the conventional Rashba splitting, the magnitude of the in-plane spin polarization is asymmetric between the two elongated surface hole pockets across the zone center. Moreover, we uncovered a giant out-of-plane spin polarization as large as the in-plane counterpart which switches the sign across the Γ-M line. We discuss the present finding in terms of the symmetry breaking and the many-body effects. 相似文献
55.
References: 《分析测试学报》2001,20(Z1):12-13
Unusual amine - bond fragmentation on the peptide/protein backbone has been reported using matrix - assisted laser desorption/ionization time - of- flight mass spectrometry (MALDI - TOFMS)The amine - bond cleavage occurred without metastable decay, while the peptide - bond cleavage occurred with metastable decay of peptide ions in a drift region of TOF mass analyzer. It was presumed that the amine - bond cleavage occurred as a non - ergodic process independent of the ionization under MALDI conditions. 相似文献
56.
Experimental studies were carried out to investigate projectile acceleration in a single-stage gun at breech pressures below
50 MPa. The gun was driven by firing either liquid or solid propellant. In-bore projectile velocity was continuously recorded
using the well-known, precise VISAR interferometer technique so that accurate projectile acceleration data could be deduced.
Both the attained projectile acceleration and muzzle exit velocity depend upon the charge-to-mass ratio and the pressure at
which the blow-out disk ruptures. The results obtained from these experiments render information on the interplay between
propellant combustion and projectile acceleration for low in-bore pressure regimes, and they provide the input data required
for adequate numerical simulation. 相似文献
57.
58.
Hideaki Ichiba Mio Nakamoto Takehiko Yajima Mitsuo Takayama Takeshi Fukushima 《Biomedical chromatography : BMC》2010,24(2):140-147
The C‐terminal octapeptide of cholecystokinin (CCK8) includes some easily oxidizable amino acids. The oxidation of CCK8 by reactive oxygen species (ROS) such as hydrogen peroxide (H2O2) and hydroxyl radicals (OH?) was investigated using reversed‐phase high performance liquid chromatography (RP‐HPLC) and subsequent electrospray ionization mass spectrometry. The mechanism of oxidation of CCK8 in the H2O2 system differed from that of CCK8 in the Fenton system, in which OH? are produced. In the H2O2 system, 28Met and 31Met were oxidized to methionine sulfoxide, and no further oxidation or degradation/hydrolysis occurred. On the other hand, in the Fenton system, 28Met and 31Met residues were oxidized to methionine sulfone via the formation of methionine sulfoxide. In addition, the oxidized product was observed at the Trp residue but not at the Tyr residue, and small peptide fragments from CCK8 were observed in the Fenton system. From these results, it was concluded that 28Met and 31Met residues of CCK8 are susceptible to oxidation by ROS. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
59.
A degradation of esperamicin A1, which is a potent antitumor antibiotic having DNA-cleaving activity, was studied by fast-atom bombardment (FAB) mass spectrometry. It was proved that the degradation easily occurs via the thiol group(s) in the matrix solution and not by a FAB-induced reaction. It was concluded that from the FAB mass spectra of all non-volatile compounds, the molecular weight should be determined by using at least two chemically different matrices. 相似文献
60.
Masakazu Tatsuno Hajime Amamoto Koji Ishi-i
Tetsunobu Takayama
《Fluid Dynamics Research》1991,8(5-6):253-272The stable posture of a pair of parallel circular cylinders in a uniform flow was experimentally studied when it was free to rotate about an axis at the middle of the two cylinders. The cylinder pair comes to rest facing the oncoming flow side by side, the line connecting the centers of the two cylinders being perpendicular to the flow, when s/d = 0.5, where s is the distance between the center of rotation and the central axis of each cylinder and d is the diameter of the cylinder. When s/d = 1.0 or 1.5, the cylinder pair is stable both in tandem, with one cylinder behind the other, and in side-by-side arrangements to the oncoming flow. When s/d 2.0, the cylinder pair is stable only in tandem arrangements. 相似文献