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181.
The signal quality of a fiber-optic distributed temperature sensor based on optical time domain reflectometry (OTDR) is improved using a pre-filtering technique in the iterative deconvolution method. Investigation of the performance is proposed using iteration conditions in which recovery rate of the signal-component is equal to that of the unfiltering technique. The recovered signal in the pre-filtering technique gives a good signal-to-noise ratio (SNR), 3 times of the unfiltered signal. Consequently, improvements in the OTDR signal with SNR of from 10 to 100 are obtained under the iterations for both distance and temperature resolutions. 相似文献
182.
183.
I. Shirotani S. Yoshida Y. Wada T. Kajiwara M. Murakami S. Yoshimura 《Solid State Communications》1981,38(7):653-656
The electrical resistivity of N-n-propylpyridinium-TCNQ2 (NPPy-TCNQ2) and N-n-butylpyridinium-TCNQn (NBPy-TCNQn) has been measured as a function of temperature and pressure. Phase transitions in these salts have been studied at high pressures. The transition temperature (Tc) in NPPy-TCNQ2 at atmospheric pressure increased with increasing pressure at the rate of dTc/dP = + 12.0 degkbar?1. The value of volume change calculated from the Clapeylon-Clausius relation was + 4.4 cm3 mol?1. The electrical resistivity along the a- and c-axis increased with increasing pressure below 7 kbar. This anomalous electrical behaviour is closely related to the crystal structure of NPPy-TCNQ2. The resistivity dropped sharply at about 11 kbar. This abrupt change may be due to a new pressure induced phase transition.The Tc of the NBPy-TCNQn increased remarkably with increasing pressure up to 0.7 kbar, above which the phase transition disappeared. The phase transitions of N-n-alkyl-substituted pyridinium TCNQ salts depend strongly on the nature of cations. 相似文献
184.
185.
Y. Asano E. Kikutani S. Kurokawa T. Miyachi M. Miyajima Y. Nagashima T. Shinkawa S. Sugimoto Y. Yoshimura 《Physics letters. [Part B]》1982,113(2):195-198
A search for K+ → π+γ, π+γγ, π+γγγ was made detecting pions from stopped kaons in the kinetic energy region between 117 MeV and 127 MeV. New Limits of 1.4 ×10?6, 8.4 × 10?6 and 1.0 × 10?4 for the branching ratio were obtained assuming a phase-space spectrum on the pion energy. The first limit also aplies to another process K+ → π+ + a, where a is a light meson with mass smaller than 100 MeV/c2 and decays into nγ's with lifetime less than 10?9 s. 相似文献
186.
187.
Renato P. Freitas Cristiane Calza Tania A. Lima Angela Rabello Ricardo Tadeu Lopes 《X射线光谱测定》2010,39(5):307-310
In this work, 102 fragments of Marajoara ceramics, belonging to the National Museum collection (Rio de Janeiro, Brazil), were analyzed using energy dispersive X‐ray fluorescence (EDXRF) and principal component analysis (PCA) in order to identify possible groups of samples that present similar behaviors or different characteristics. This information will give an important aid to a more accurate classification of these artifacts. The EDXRF measurements were carried out with a portable system developed in the Nuclear Instrumentation Laboratory consisting of an Oxford TF3005 X‐ray tube, with W anode, and an Si‐PIN XR‐100CR detector from Amptek, working at 25 kV and 100 µA, acquisition time of 600 s and a beam collimation of 2 mm. PCA applied to the X‐ray fluorescence results revealed a clear cluster separation to the samples. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
188.
Lee Y Watanabe T Takata T Hara M Yoshimura M Domen K 《The journal of physical chemistry. B》2006,110(35):17563-17569
The photocatalytic activity of beta-Ge(3)N(4) powder for overall water splitting is successfully enhanced by ammonia treatment at 823 K for 5-24 h at ammonia pressures of 20 MPa or greater. The surface and bulk nitrogen content in the treated samples varies according to the treatment temperature and treatment time, related to the stability of beta-Ge(3)N(4) powder under pressurized ammonia. The change in nitrogen content resulted in a change in the photocatalytic activity for overall water splitting. A beta-Ge(3)N(4) powder treated at 823 K for 5 h under ammonia at 20 MPa exhibited a photocatalytic activity 4 times higher than that of the as-synthesized powder, attributable to a decrease in the density of anion defects in the bulk and surface. 相似文献
189.
[reaction: see text] Ortho-lithiation of (2R,4S,5R)-3,4-dimethyl-2-ferrocenyl-5-phenyl[1,3,2]oxazaphospholidine 2-oxide 2 was carried out with diastereoselectivity of >99%, affording a new and efficient way for introducing planar chirality into the ferrocene backbone. Various electrophiles were used to quench the lithiated species, showing the wide applicability of the new ortho-directing group and its potential to generate ligands for use in asymmetric catalysis. 相似文献
190.
Luciana S. Buriol Michael J. Hirsch Panos M. Pardalos Tania Querido Mauricio G. C. Resende Marcus Ritt 《Optimization Letters》2010,4(4):619-633
One of the main goals in transportation planning is to achieve solutions for two classical problems, the traffic assignment
and toll pricing problems. The traffic assignment problem aims to minimize total travel delay among all travelers. Based on
data derived from the first problem, the toll pricing problem determines the set of tolls and corresponding tariffs that would
collectively benefit all travelers and would lead to a user equilibrium solution. Obtaining high-quality solutions for this
framework is a challenge for large networks. In this paper, we propose an approach to solve the two problems jointly, making
use of a biased random-key genetic algorithm for the optimization of transportation network performance by strategically allocating
tolls on some of the links of the road network. Since a transportation network may have thousands of intersections and hundreds
of road segments, our algorithm takes advantage of mechanisms for speeding up shortest-path algorithms. 相似文献