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41.
Matías Germán dell’Erba 《Journal of statistical physics》2012,146(6):1263-1273
We perform an analytical study of a simplified bipartite matching problem in which there exists a constant matching energy,
and both heterosexual and homosexual pairings are allowed. We obtain the partition function in a closed analytical form and
we calculate the corresponding thermodynamic functions of this model. We conclude that the model is favored at high temperatures,
for which the probabilities of heterosexual and homosexual pairs tend to become equal. In the limits of low and high temperatures,
the system is extensive, however this property is lost in the general case. There exists a relation between the matching energies
for which the system becomes more stable under external (thermal) perturbations. As the difference of energies between the
two possible matches increases the system becomes more ordered, while the maximum of entropy is achieved when these energies
are equal. In this limit, there is a first order phase transition between two phases with constant entropy. 相似文献
42.
43.
Syahmi AR Vijayarathna S Sasidharan S Latha LY Kwan YP Lau YL Shin LN Chen Y 《Molecules (Basel, Switzerland)》2010,15(11):8111-8121
Elaeis guineensis (Arecaceae) is widely used in West African traditional medicine for treating various ailments. An evaluation on the toxicity of extracts of this plant is crucial to support the therapeutic claims. The acute oral toxicity and brine shrimp lethality of a methanolic extract of this plant was tested. Oral administration of crude extract at the highest dose of 5,000 mg/kg resulted in no mortalities or evidence of adverse effects, implying that E. guineensis is nontoxic. Normal behavioral pattern, clinical signs and histology of vital organs confirm this evidence. The E. guineensis extracts screened for toxicity against brine shrimp had 50% lethal concentration (LC??) values of more than 1.0 mg/mL (9.00 and 3.87 mg/mL, at 6 and 24 h, respectively), confirming that the extract was not toxic. Maximum mortalities occurred at 100 mg/mL concentration while the least mortalities happened to be at 0.195 mg/mL concentration. The results of both tests confirm that E. guineensis is nontoxic and hence safe for commercial utilization. 相似文献
44.
Zañartu M Mehta DD Ho JC Wodicka GR Hillman RE 《The Journal of the Acoustical Society of America》2011,129(1):326-339
Different source-related factors can lead to vocal fold instabilities and bifurcations referred to as voice breaks. Nonlinear coupling in phonation suggests that changes in acoustic loading can also be responsible for this unstable behavior. However, no in vivo visualization of tissue motion during these acoustically induced instabilities has been reported. Simultaneous recordings of laryngeal high-speed videoendoscopy, acoustics, aerodynamics, electroglottography, and neck skin acceleration are obtained from a participant consistently exhibiting voice breaks during pitch glide maneuvers. Results suggest that acoustically induced and source-induced instabilities can be distinguished at the tissue level. Differences in vibratory patterns are described through kymography and phonovibrography; measures of glottal area, open/speed quotient, and amplitude/phase asymmetry; and empirical orthogonal function decomposition. Acoustically induced tissue instabilities appear abruptly and exhibit irregular vocal fold motion after the bifurcation point, whereas source-induced ones show a smoother transition. These observations are also reflected in the acoustic and acceleration signals. Added aperiodicity is observed after the acoustically induced break, and harmonic changes appear prior to the bifurcation for the source-induced break. Both types of breaks appear to be subcritical bifurcations due to the presence of hysteresis and amplitude changes after the frequency jumps. These results are consistent with previous studies and the nonlinear source-filter coupling theory. 相似文献
45.
The generation of aerodynamic sound by the interaction of flow at a Reynolds number of 150 and a Mach number of 0.2 with a rigid square cylinder attached to a rigid thin flat plate is numerically investigated. When the length of the plate is varied from L=0.5D to 6D, where D is the side length of the square cylinder, the results can be grouped into three distinct regimes. For the first regime (L?D), the sound levels decrease with increasing plate length. A 3 dB sound reduction is obtained when the length of the plate is D. For the second regime (1.25D?L?4.75D), the sound levels increase with increasing plate length. For the third regime (5D?L?6D), the sound levels decrease as the length of the plate increases but the levels are higher than for the other regimes. Results also show that the lift fluctuation is the dominant sound source. These acoustic results can be explained in terms of the fluid mechanics occurring in the near wake of the cylinder. 相似文献
46.
Chang Fu Dee Ishaq Ahmad Yan Long Zhou Xingtai M.M. Salleh B.Y. Majlis 《Physica E: Low-dimensional Systems and Nanostructures》2011,43(10):1857-1862
Study of proton beam induced welding of multiwall carbon nanotubes (MWCNTs) with ZnO nanowires (NWs) has been carried out by proton (H+) beam irradiation. The samples were irradiated by 70-keV proton (H+) ion beams at different substrate temperatures. The irradiation-induced defects in CNTs and ZnO NWs were greatly reduced at elevated temperature. The crystalline structure of ZnO NWs and MWCNTs were found to remain stable after the irradiation at 700 K. As a preparation step, a coupling of two parallel ZnO NWs with irradiation has also been demonstrated. The welding mechanisms of MWCNTs and ZnO NWs were also been suggested. These two welding processes between same and distinct nanostructures to form homo- and hetero-junctions have provided an opportunity to mass produce interconnecting one-dimensional structures used for the manufacturing of future nanowire-based electronic circuits and devices. 相似文献
47.
Pavel Řezanka Klára Navrátilová Pavel Žvátora David Sýkora Pavel Matějka Ivan Mikšík Václav Kašička Vladimír Král 《Journal of nanoparticle research》2011,13(11):5947-5957
In this study, spherical gold nanoparticles (GNPs) of 14.7 nm diameter, prepared by citrate reduction of a gold(III) salt
and characterized by UV–Vis absorption spectrometry and transmission electron microscopy, were modified by a covalent attachment
of 6I-O-(3-mercaptopropyl)β-cyclodextrin (β-CD-SH) or per-6-deoxy-per-6-mercapto-β-cyclodextrin (β-CD-SH7). Subsequently, via three
alternative approaches, β-CD-modified GNPs were immobilized onto the inner wall of the fused-silica (FS) capillaries and applied
as special stationary phases for open-tubular capillary electrochromatography (OT-CEC). The first immobilization procedure
was based on pre-derivatization of a FS capillary with (3-mercaptopropyl)trimethoxysilane (MPTMS) followed by subsequent reactions
with GNPs and β-CD-SH or β-CD-SH7. The other two preparation protocols took advantage of sol–gel approach gaining a significant
increase in the interaction surface for solutes. In both instances, the sol–gel created 3D structure was further covalently
modified with GNPs. Serving that purpose, either β-CD-SH7 modified GNPs were used for the immobilization into the sol–gel
matrix (“one-step sol–gel technique”) or native GNPs were immobilized first into the sol–gel matrix and subsequently modified
with β-CD-SH7 (“two-step sol–gel technique”). The separation performance of CD-GNPs modified FS capillaries was tested by
OT-CEC in reversed-phase mode applied to separation of a model mixture of five polyaromatic hydrocarbons. The highest separation
efficiencies were obtained with the capillaries prepared by two-step sol–gel technique. However, with respect to the relatively
low reproducibility of this method, the first of the above preparation procedures, i.e., a simple pre-derivatization of the
FS capillary with MPTMS ensued with β-CD-SH7-GNPs immobilization seems to be more feasible approach providing decent separation
efficiency. 相似文献
48.
A. Ali Yusuf A.K. Yahya Nawazish A. Khan F. Md. Salleh E. Marsom N. Huda 《Physica C: Superconductivity and its Applications》2011,471(11-12):363-372
Substitution of Ge4+ in place of Cu in Tl0.85Cr0.15Sr2CaCu2?xGexO7?δ (x = 0–0.6) showed initial increase in zero critical temperature value, Tc zero from 98 K (x = 0) to 100 K (x = 0.1) and in the range of 85–86 K for x = 0.2–0.3. The slow decrease in Tc zero is unexpected as tetravalent Ge4+ substitution is expected to strongly reduce hole concentration in the samples and suppress Tc zero. Excess conductivity analyses of resistance versus temperature data based on Asmalazov–Larkin (AL) theory revealed that the substitution induced 2D-to-3D transition of fluctuation induced conductivity with the highest transition temperature, T2D–3D observed at x = 0.1. FTIR spectroscopy analysis indicates Ge4+ substitution cause reduction in CuO2/GeO2 interplanar distance while our calculation based on Lawrence–Doniach model revealed highest superconducting coherence length, ξc(0) and interplanar coupling, J at x = 0.3. On the other hand, substitution of divalent Mg2+ for Ca2+ in (Tl0.5Pb0.5)(Sr1.8Yb0.2)(Ca1?yMgy)Cu2O7 (y = 0–1.0), which is not expected to directly vary hole concentration, surprisingly caused Tc zero to increase from 89.6 K (y = 0) to an optimum value of 95.9 K (y = 0.6) before decreasing with further increase in y. Excess conductivity analyses showed 2D-to-3D transition of fluctuation induced conductivity for all samples where the highest T2D–3D was at y = 0.4. Similar calculation revealed highest values of ξc(0) and J also at y = 0.4. FTIR analysis of the samples indicates inequivalent Cu(1)O(2)Pb/Tl lengths and possible tilting of CuO2 plane as a result of Mg2+ substitution. The increased ξc(0) and J as a result of the Ge4+ and Mg2+ substitutions are suggested to contributed to sustenance of superconductivity above 80 K in the samples. 相似文献
49.
Aurélie Matéos Jean‐Michel Girardet Daniel Mollé Catherine Corbier Jean‐Luc Gaillard Laurent Miclo 《Rapid communications in mass spectrometry : RCM》2010,24(11):1533-1542
Equine β‐casein is phosphorylated at variable degrees and isoforms carrying 3 to 7 phosphate groups (3P–7P) have been found in milk, but the phosphorylated amino acid residues of each isoform are not yet identified. In the present work, the different phosphorylation variants were first isolated by ion‐exchange chromatography and then hydrolysed by trypsin to generate caseinophosphopeptides (CPPs), each containing all the potential phosphorylation sites. The equine CPPs were prepared by metal oxide affinity chromatography, a method based on the affinity of phosphate groups towards titanium dioxide immobilized onto a micro‐column. This method turned out to be an efficient tool to separate the CPPs Arg1–Lys34 and Glu4–Lys34 from non‐phosphorylated peptides. Purification was achieved by reversed‐phase high‐performance liquid chromatography (RP‐HPLC) and each CPP was hydrolyzed by endoproteinase Glu‐C. Finally, the digests were analyzed by RP‐HPLC/electrospray ionization mass spectrometry (RP‐HPLC/ESI‐MS) and identified by nano‐electrospray ionization tandem mass spectrometry (nESI‐MS/MS) to locate the phosphorylated sites of the β‐casein isoforms 4P–7P with accuracy. Thus, the isoform 4P was found to be phosphorylated on residues Ser9, Ser23, Ser24, and Ser25. Addition of phosphate groups on Ser18, Thr12, and Ser10 led to the formation of the isoforms 5P–7P, respectively. The results indicated that the in vivo phosphorylation of the equine β‐casein follows a sequential way and is not randomly performed. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
50.
This paper reports the use of graphite thin films as a counter electrode of a solid state photoelectrochemical cells of ITO/TiO2/PVC-LiClO4/graphite. The photoelectrochemical cells material was a screen-printed layer of titanium dioxide onto an ITO-covered glass
substrate which was used as a working electrode of the device. The solid electrolyte used was PVC-LiClO4 that was prepared by solution casting technique. The graphite films which serve as a counter electrode were prepared onto
glass substrate by electron beam evaporation technique at substrate temperatures variation of 25, 50, 100, 150 and 200 °C.
The dependence of sheet resistance and surface morphology of the graphite films on substrate temperature were studied. The
films deposited at 25 °C shows the smoothest surface morphology and the smallest grain size. Bigger grain size, rougher surface
morphology of graphite film counter electrode. The current-voltage characteristics of four devices utilising the graphite
counter electrode with different substrate temperature in dark as well as under illumination of 100 mWcm−2 light from a tungsten halogen lamp were recorded at room temperature and at 50 °C, respectively. It was found that the photovoltaic
parameters of the device such as short-circuit current density, Jsc and open-circuit voltage, Voc increases with the decreasing average grain size of the graphite counter electrode. The device whose graphite film counter
electrode was deposited onto the glass substrate at 25 °C gave the highest Jsc of 0.32 μA/cm2 and Voc of 117 mV, respectively. 相似文献