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121.
122.
Fayez M. Mina 《International Journal of Mathematical Education in Science & Technology》2013,44(5):525-529
In this paper the author attempts to build up an outline for a geometry syllabus in primary education. 相似文献
123.
Alfonso Zoleo Daria Confortin Nicola Dal Mina Marina Brustolon 《Applied magnetic resonance》2010,39(3):215-223
Samples from covers and endleaves of sixteenth to eighteenth century books in good conservation state from the Biblioteca
Nazionale Marciana in Venice have been investigated by means of electron paramagnetic resonance (EPR) spectroscopy and optical
microscopy to characterize the embedded paramagnetic species and to test differences and similarities of the materials in
the two types of book components. We detected the Mn(II), Fe(III), and Cu(II) paramagnetic ions, and analyzed their EPR signals
by comparing them with previous results in literature of EPR studies on paper. Interestingly, the Mn(II) EPR spectrum profile
appears as a fingerprint for samples coming from the same book, either from cover or endleaf, and it looks different for samples
extracted from different books. We discuss the role of EPR as a spectroscopic tool for characterizing the interaction of the
ions with the paper components and as possible agents of degradation. 相似文献
124.
125.
Mina Guli Xiaotian Li Kan Zhang Yue Chi 《Journal of Sol-Gel Science and Technology》2010,54(3):329-334
Large, flawless and transparent silica monoliths were prepared at room temperature by solvent evaporation method and loaded
with dye. The composites containing dye molecules were characterized by X-ray diffraction, transmission electron microscopy,
Uv–vis and photoluminescence spectra. A red-shift in photoluminescence spectrum was observed from the composite monolith compared
with that of laser dye in C2H5OH solution. The property of laser narrowing has been shown when the composites are pumped at p = 355 nm by nitrogen laser. 相似文献
126.
Li Jiang Mina Kim BettyAnn Chodkowski Manus J. Donahue James J. Pekar Peter C.M. Van Zijl Marilyn Albert 《Magnetic resonance imaging》2010
Arterial spin labeling (ASL) magnetic resonance imaging (MRI) is becoming a popular method for measuring perfusion due to its ability of generating perfusion maps noninvasively. This allows for frequent repeat scanning, which is especially useful for follow-up studies. However, limited information is available regarding the reliability and reproducibility of ASL perfusion measurements. Here, the reliability and reproducibility of pulsed ASL was investigated in an elderly population to determine the variation in perfusion among cognitively normal individuals in different brain structures. Intraclass correlation coefficients (ICC) and within-subject variation coefficients (wsCV) were used to estimate reliability and reproducibility over a period of 1 year. Twelve cognitively normal subjects (75.5±5.3 years old, six male and six female) were scanned four times (at 0, 3, 6 and 12 months). No significant difference in cerebral blood flow (CBF) was found over this period. CBF values ranged from 46 to 53 ml/100 g per minute in the medial frontal gyrus (MFG) and from 40 to 44 ml/100 g per minute over all gray matter regions in the superior part of the brain. Data obtained from the first two scans were processed by two readers and showed high reliability (ICC >0.97) and reproducibility (wsCV <6%). However, over the total period of 1 year, reliability reduced to a moderate level (ICC=0.63–0.74) with wsCVs of gray matter, left MFG, right MFG of 13.5%, 12.3%, and 15.4%, respectively. In conclusion, measurement of CBF with pulsed ASL provided good agreement between inter-raters. A moderate level of reliability was obtained over a 1-year period, which was attributed to variance in slice positioning and coregistration. As such pulsed ASL has the potential to be used for CBF comparison in longitudinal studies. 相似文献
127.
High field electrical switching on blown films of MoO3(60%)–P2O5(40%), MoO3(50%)–WO3(10%)–P2O5(40%), and MoO3(45%)–WO3(15%)–P2O5(40%) having different thicknesses was studied and compared. Switching was observed using two terminal samples. S-type current–voltage
characteristic (current-controlled negative resistance—CCNR) with memory was observed in molybdenum–phosphate glasses, but
N-type characteristic (voltage-controlled negative resistance—VCNR) with threshold in tungsten–molybdenum–phosphate glasses
was observed. The important observation was that with the addition of WO3 to binary MoO3–P2O5 led to a change of I–V characteristic from CCNR with memory to VCNR with threshold. The measurements of density and molar volume showed linear relation
between MoO3 content and density which decreased with the increase of MoO3 content. The samples’ thickness had no significant effect on threshold voltage. The attained results also indicated that
the electrode material had no effect on switching property of devices. The switching behavior of the devices did not show
any dependence on the polarity of the applied voltage. In terms of the effect of heat on the switching behavior of molybdenum–phosphate
glasses, it was found that threshold voltage decreases with increasing of temperature. Finally, the switching phenomenon was
explained by thermal (formation of crystalline filaments) and electronic models. 相似文献
128.
This paper is concerned with the initial boundary value problem for the p-system with damping. We prove the existence of the global smooth solution under the assumption that only the C0-norm of the derivative of the initial data is sufficiently small, while the C0-norm of the initial data is not necessarily small. The proof is based on several key a priori estimates, the maximum principle and the characteristic method. 相似文献
129.
One-photon mass-analyzed threshold ionization (MATI) spectrum of trans-C(2)H(2)Cl(2) was obtained by using vacuum ultraviolet radiation generated by four-wave mixing in Kr. The ionization energy determined from the position of the 0-0 band in the spectrum was 9.6306 +/- 0.0006 eV. Ten vibrational fundamentals for the cation were identified. The spectrum also displayed abundant overtones and combinations, most of which could be assigned adequately by comparing with the quantum chemical results. It was found that channel interaction was not important for this system. The equilibrium geometry of the cation was estimated through the Franck-Condon fit. 相似文献
130.
Zhou B Shimamura M Fujiwara E Kobayashi A Higashi T Nishibori E Sakata M Cui H Takahashi K Kobayashi H 《Journal of the American Chemical Society》2006,128(12):3872-3873
A single-component molecular conductor [Au(tmdt)2] (tmdt = trimethylenetetrathiafulvalenedithiolate) undergoes an antiferromagnetic phase transition at unprecedentedly high temperature (TN = 110 K). Black microcrystals of alloys, [Ni1-xAux(tmdt)2] (0.0 < x < 1.0) were prepared. The Au-rich system exhibited an antiferromagnetic transition. Metallic single crystal was obtained for x = 0.25. 相似文献