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671.
The growth of pentacene on C60 film has been studied in real-time by low energy electron microscope. The standing-up phase overgrows on the lying-down phase at room temperature with increasing film thickness. At intermediate temperature we observed two distinct types of nucleation: an earlier nucleation of lying-down phase and a delayed nucleation of standing-up phase on the bare C60 surface between islands of lying-down phase. Further thermal activation control enabled us to tune the types of nucleation and the standing-up phase without co-presence of the lying-down phase could be achieved above ∼70 °C. 相似文献
672.
Ichihara C Kawakami N Yasuno S Hino A Fujikawa K Kobayashi A Ochi M Gotoh H Kugimiya T 《Micron (Oxford, England : 1993)》2009,40(1):66-69
High-resolution Rutherford backscattering spectrometry (HRBS) in combination with grazing angle argon sputtering was carried out to characterize the interface of aluminum-nickel (Al-Ni) alloy and amorphous-silicon films in a thin film transistor (TFT) for liquid crystal display (LCD). After thinning the top Al-Ni layer by a 1-keV Ar sputtering, the sensitivity of the interface oxygen was improved to be twice higher than that before sputtering. The results revealed that the oxygen at the interface relates to the contact characteristics. 相似文献
673.
Tomoya Miura Junki Nakahashi Takanori Sasatsu Masahiro Murakami 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(4):1150-1154
The stereoselective synthesis of anti isomers of γ‐boryl‐substituted homoallylic alcohols is disclosed. (E)‐1,2‐Di(boryl)alk‐1‐enes undergo Ru‐catalyzed double‐bond transposition with control of the geometry. The in situ generated (E)‐1,2‐di(boryl)alk‐2‐enes add to aldehydes in a stereospecific manner. The alkenylboron group within the product is amenable to a variety of synthetic derivatizations. 相似文献
674.
Tomoya Nishioka Kiyonori Kuroda Munetaka Akita Michito Yoshizawa 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(20):6651-6655
A gemini‐type amphiphilic molecule, constituted of two V‐shaped polyaromatic amphiphiles linked by a linear acetylene spacer, was synthesized. The gemini amphiphile assembles into a well‐defined aromatic micelle (ca. 2 nm in core diameter), providing higher stability in water even at low concentration (0.09 mm ) and high temperature (>130 °C). Unlike common gemini amphiphiles with aliphatic chains, the present amphiphile and its micellar assembly emit green and orange fluorescence (ΦF=33 and 9 %), respectively. Despite strong and multiple π‐stacks of the polyaromatic panels of the amphiphiles, the water‐soluble gemini aromatic micelle incorporates medium‐size to large hydrophobic compounds into the frameworks. Interestingly, the guest binding capability toward large planar molecules was enhanced by more than two times through the pre‐encapsulation of spherical molecules in the cavity. 相似文献
675.
Critical condition of inner cylinder radius for sustaining rotating detonation waves in rotating detonation engine thruster 总被引:1,自引:0,他引:1
Akira Kawasaki Tomoya Inakawa Jiro Kasahara Keisuke Goto Ken Matsuoka Akiko Matsuo Ikkoh Funaki 《Proceedings of the Combustion Institute》2019,37(3):3461-3469
We describe the critical condition necessary for the inner cylinder radius of a rotating detonation engine (RDE) used for in-space rocket propulsion to sustain adequate thruster performance. Using gaseous C2H4 and O2 as the propellant, we measured thrust and impulse of the RDE experimentally, varying in the inner cylinder radius ri from 31 mm (typical annular configuration) to 0 (no-inner-cylinder configuration), while keeping the outer cylinder radius (ro = 39 mm) and propellant injector position (rinj = 35 mm) constant. In the experiments, we also performed high-speed imaging of self-luminescence in the combustion chamber and engine plume. In the case of relatively large inner cylinder radii (ri = 23 and 31 mm), rotating detonation waves in the combustion chamber attached to the inner cylinder surface, whereas for relatively small inner cylinder radii (ri = 0, 9, and 15 mm), rotating detonation waves were observed to detach from the inner cylinder surface. In these small inner radii cases, strong chemical luminescence was observed in the plume, probably due to the existence of soot. On the other hand, for cases where ri = 15, 23, and 31 mm, the specific impulses were greater than 80% of the ideal value at correct expansion. Meanwhile, for cases ri = 0 and 9 mm, the specific impulses were below 80% of the ideal expansion value. This was considered to be due to the imperfect detonation combustion (deflagration combustion) observed in small inner cylinder radius cases. Our results suggest that in our experimental conditions, ri = 15 mm was close to the critical condition for sustaining rotating detonation in a suitable state for efficient thrust generation. This condition in the inner cylinder radius corresponds to a condition in the reduced unburned layer height of 4.5–6.5. 相似文献
676.
Takayuki Fuyuto Helmut Kronemayer Burkhard Lewerich Jan Brübach Taketoshi Fujikawa Kazuhiro Akihama Thomas Dreier Christof Schulz 《Experiments in fluids》2010,49(4):783-795
A detailed understanding of transport phenomena and reactions in near-wall boundary layers of combustion chambers is essential
for further reducing pollutant emissions and improving thermal efficiencies of internal combustion engines. In a model experiment,
the potential of laser-induced fluorescence (LIF) was investigated for measurements inside the boundary layer connected to
flame-wall interaction at atmospheric pressure. Temperature and species distributions were measured in the quenching boundary
layer formed close to a cooled metal surface located parallel to the flow of a premixed methane/air flat flame. Multi-line
NO-LIF thermometry provided gas-phase temperature distributions. In addition, flame species OH, CH2O and CO were monitored by single-photon (OH, CH2O) and two-photon (CO) excitation LIF, respectively. The temperature dependence of the OH-LIF signal intensities was corrected
for using the measured gas-phase temperature distributions. The spatial line-pair resolution of the imaging system was 22 μm
determined by imaging microscopic line pairs printed on a resolution target. The experimental results show the expected flame
quenching behavior in the boundary layer and they reveal the potential and limitations of the applied diagnostics techniques.
Limitations in spatial resolution are attributed to refraction of fluorescence radiation propagating through steep temperature
gradients in the boundary layer. For the present experimental arrangements, the applied diagnostics techniques are applicable
as close to the wall as 200 μm with measurement precision then exceeding the 15–25% limit for species detection, with estimates
of double this value for the case of H2CO due to the unknown effect of the Boltzmann fraction corrections not included in the data evaluation process. Temperature
measurements are believed to be accurate within 50 K in the near-wall zone, which amounts to roughly 10% at the lower temperatures
encountered in this region of the flames. 相似文献
677.
Nakao Y Yukawa T Hirata Y Oda S Satoh J Hiyama T 《Journal of the American Chemical Society》2006,128(22):7116-7117
Allyl cyanides are found to add across alkynes in the presence of a nickel catalyst prepared from Ni(cod)2 and P(4-CF3-C6H4)3 in situ to give variously functionalized di- or trisubstituted acrylonitriles in highly stereoselective manners possibly via a pi-allylnickel species as an intermediate. alpha-Siloxyallyl cyanides also react at the gamma-position of a cyano group with both internal and terminal alkynes having various functional groups to give silyl enol ethers, which give the corresponding aldehydes or ketones upon hydrolysis. 相似文献
678.
Shiro Kobayashi Masashi Ohmae Shun-ichi Fujikawa Hirofumi Ochiai 《Macromolecular Symposia》2005,226(1):147-156
Hyaluronidase (HAase)-catalyzed polymerization was performed to provide synthetic hyaluronan (HA), chondroitin (Ch) and their derivatives. The 2-methyl oxazoline derivatives derived from their repeating disaccharides of N-acetylhyalobiuronate ( 1a ) and N-acetylchondrosine ( 3a ) were effectively polymerized by the enzyme, giving rise to synthetic HA and synthetic Ch in good yields through regio-selective and stereo-controlled ring-opening polyaddition. The oxazoline derivatives of 2-ethyl ( 1b , 3b ), 2-n-propyl ( 1c , 3c ), 2-isopropyl ( 1d , 3d ), 2-phenyl ( 1e , 3e ), 2-vinyl ( 1f , 3f ) and 2-isopropenyl ( 1g ) were synthesized and subjected to the enzymatic reaction. Monomers 1b , 1c , 1f , 3b and 3f were polymerized to corresponding polysaccharides 2b , 2c , 2f , 4b and 4f , all of which are unnatural glycosaminoglycans. Compounds 1d , 3c and 3d were also catalyzed by the enzyme, affording oligomers of 2d , 4c and 4d were produced in trace amounts. Monomers 1e , 1g and 3e were not catalyzed by HAase. 相似文献
679.
Wang resin-supported Evans' chiral auxiliary (23) was designed based on a novel polymer-anchoring strategy, which utilizes the 5-position of the oxazolidinone ring, and its new synthetic route applicable to multi-gram preparation in just a day was developed. Solid-phase Evans' asymmetric alkylation on 23-derived N-acylimide resin and following lithium hydroperoxide-mediated chemoselective hydrolysis afforded the corresponding α-branched carboxylic acids in desired high stereoselectivities (up to 97% ee) and moderate to good overall yield (up to 70%, for 3 steps), which were comparable to those of the conventional solution-phase methods. Furthermore, recovery and recycling of the polymer-supported chiral auxiliary were successfully achieved without decreasing the stereoselectivity of the product. Therefore, this is the first successful example that the solid-phase Evans' asymmetric enolate-alkylation was efficiently performed on the solid-support, and it is concluded that the connection to the solid-support via the 5-position of the oxazolidinone ring is an ideal strategy in the solid-phase Evans' chiral auxiliary. 相似文献
680.
Hasegawa E Seida T Chiba N Takahashi T Ikeda H 《The Journal of organic chemistry》2005,70(23):9632-9635
[Reaction: see text]. In the photoreaction of benzophenones with 1,3-dimethyl-2-phenylbenzimidazoline (DMPBI), benzhydrols were major products. Addition of H2O accelerated the reaction with no change in the product distribution, while AcOH, PhOH, and metal salts such as LiClO4 and Mg(ClO4)2 were effective additives to produce benzpinacols. In contrast, benzpinacols were exclusively formed regardless of the solvent and the additive in the reactions with 2-(o-hydroxyphenyl)-1,3-dimethylbenzimidazoline (o-HPDMBI). These observations are consistent with the hypothesis that DMPBI*+ donates a proton at the C2 position to the benzophenone ketyl radicals while o-HPDMBI*+ donates a phenol proton. 相似文献