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991.
Lian C. T. Shoute Nikola Pekas Yiliang Wu Richard L. McCreery 《Applied Physics A: Materials Science & Processing》2011,102(4):841-850
The relationship between bias-induced redox reactions and resistance switching is considered for memory devices containing
TiO2 or a conducting polymer in “molecular heterojunctions” consisting of thin (2–25 nm) films of covalently bonded molecules,
polymers, and oxides. Raman spectroscopy was used to monitor changes in the oxidation state of polythiophene in Au/P3HT/SiO2/Au devices, and it was possible to directly determine the formation and stability of the conducting polaron state of P3HT
by applied bias pulses [P3HT = poly(3-hexyl thiophene)]. Polaron formation was strongly dependent on junction composition,
particularly on the interfaces between the polymer, oxide, and electrodes. In all cases, trace water was required for polaron
formation, leading to the proposal that water reduction acts as a redox counter-reaction to polymer oxidation. Polaron stability
was longest for the case of a direct contact between Au and SiO2, implying that catalytic water reduction at the Au surface generated hydroxide ions which stabilized the cationic polaron.
The spectroscopic information about the dependence of polaron stability on device composition will be useful for designing
and monitoring resistive switching memory based on conducting polymers, with or without TiO2 present. 相似文献
992.
Huilan Su Fang Song Qun Dong Tuoqi Li Xin Zhang Di Zhang 《Applied Physics A: Materials Science & Processing》2011,104(1):269-274
A simple and versatile technique was developed to prepare hierarchical ZnO single crystals by introducing eggshell membrane
(ESM) to a bio-inspired approach. Based on the control of nucleation and gestation, ZnO nanocrystallites could grow at three
dimensions into polyhedral single crystals through a surface sol-gel process followed by a calcination treatment. Different
from traditional wet chemical techniques, our synthetic process depends more on the restrictive or directing functions of
the ESM biomacromolecules. The hierarchical ZnO nanostructures doped with polyhedral single crystallites could be desirable
for catalysts, photoelectrochemical devices, especially solar cells. 相似文献
993.
Galyna P. Gorbenko 《Journal of fluorescence》2011,21(3):945-951
Fluorescence spectroscopy is one of the most powerful tools for characterization of a multitude of biological processes. Of
these, the phenomenon of protein oligomerization attracts especial interest due to its crucial role in the formation of fibrillar
protein aggregates (amyloid fibrils) involved in ethiology of so-called protein misfolding diseases. It is becoming increasingly
substantiated that protein fibrillization in vivo can be initiated and modulated at membrane-water interface. All steps of
membrane-assisted fibrillogenesis, viz., protein adsorption onto lipid bilayer, structural transition of polypeptide chain
into a highly aggregation-prone partially folded conformation, assembly of oligomeric nucleus from membrane-bound monomeric
species and fiber elongation can be monitored with a mighty family of fluorescence-based techniques. Furthermore, the mechanisms
behind cytotoxicity of prefibrillar protein oligomers are highly amenable to fluorescence analysis. The applications of fluorescence
spectroscopy to monitoring protein oligomerization in a membrane environment are exemplified and some problems encountered
in such kinds of studies are highlighted. 相似文献
994.
An accurate numerical model to investigate the pump-to-signal relative intensity noise (RIN) transfer in two-pump fibre optical
parametric amplifiers (2-P FOPAs) for low modulation frequencies is presented. Compared to other models in the field, this
model takes into account the fibre loss, pump depletion as well as the gain saturation. As a result, the model allows to include
a wide range of practical circumstances, both in and beyond the undepleted pump regime, related to different applications
of FOPAs. In the small-signal or undepleted pump regime, the model predicts the ripples of the RIN spectrum very well and
yields better results than those of other models. It is shown that beyond the small-signal regime, pump power variations do
not remain unchanged over the length of the amplifier and for high signal powers, when the FOPA saturates, minimum pump-to-signal
RIN transfer occurs. The results of the model are also compared with the available experimental data in the field and a very
good agreement can be seen. 相似文献
995.
The Gauge/Bethe correspondence of Nekrasov and Shatashvili relates the spectrum of integrable spin chains to the ground states
of supersymmetric gauge theories. Up to now, this correspondence has been an observation; the underlying reason for its existence
remaining elusive. We argue here that geometrical representation theory is a mathematical foundation of the Gauge/Bethe correspondence,
and it provides a framework to study families of gauge theories in a unified way. 相似文献
996.
Vladimir Petukhov John Stoemenos Johan Rothman Andrey Bakin Andreas Waag 《Applied Physics A: Materials Science & Processing》2011,102(1):161-168
In order to interpret results of temperature dependent Hall measurements in heteroepitaxial ZnO-thin films, we adopted a multilayer
conductivity model considering carrier-transport through the interfacial layer with degenerate electron gas as well as the
upper part of ZnO layers with lower conductivity. This model was applied to the temperature dependence of the carrier concentration
and mobility measured by Hall effect in a ZnO-layer grown on c-sapphire with conventional high-temperature MgO and low-temperature
ZnO buffer. We also compared our results with the results of maximum entropy mobility-spectrum analysis (MEMSA). The formation
of the highly conductive interfacial layer was explained by analysis of transmission electron microscopy (TEM) images taken
from similar layers. 相似文献
997.
Carlyle T. B. Menezes Erilson C. Barros Raquel D. Rufino Juliana M. Luna Leonie A. Sarubbo 《Applied biochemistry and biotechnology》2011,163(4):540-546
Dissolved air flotation (DAF) is a well-established separation process employing micro bubbles as a carrier phase. The application
of this technique in the treatment of acid mine drainage, using three yeast biosurfactants as alternative collectors, is hereby
analyzed. Batch studies were carried out in a 50-cm high acrylic column with an external diameter of 2.5 cm. High percentages
(above 94%) of heavy metals Fe(III) and Mn(II) were removed by the biosurfactants isolated from Candida lipolytica and Candida sphaerica and the values were found to be similar to those obtained with the use of the synthetic sodium oleate surfactant. The DAF
operation with both surfactant and biosurfactants, achieved acceptable turbidity values, in accordance with Brazilian standard
limits. The best ones were obtained by the biosurfactant from C. lipolytica, which reached 4.8 NTU. The results obtained with a laboratory synthetic effluent were also satisfactory. The biosurfactants
removed almost the same percentages of iron, while the removal percentages of manganese were slightly higher compared with
those obtained in the acid mine drainage effluent. They showed that the use of low-cost biosurfactants as collectors in the
DAF process is a promising technology for the mining industries. 相似文献
998.
999.
Xiongxin Dai Sheila Kramer-Tremblay 《Journal of Radioanalytical and Nuclear Chemistry》2011,289(2):461-466
Assays of alpha- and beta-emitting radionuclides in swipe samples are often required to monitor the presence of removable
surface contamination for radiological protection and control in nuclear facilities. Swipe analysis has also proven to be
a very sensitive analytical technique to detect nuclear signatures for safeguard verification purposes. A new sequential method
for the determination of actinide isotopes and radiostrontium in swipe samples, which utilizes a streamlined column separation
with stacked anion and extraction chromatography resins, has been developed. To validate the separation procedure, spike and
blank samples were prepared and analyzed by inductively coupled mass spectrometry (ICP-MS), alpha spectrometry and liquid
scintillation (LS) counting. Low detection limits have been achieved for isotopic analysis of Pu (238Pu, 239Pu, 240Pu, 241Pu), U (234U, 235U, 238U), Am (241Am), Cm (242Cm, 243/244Cm) and Sr (90Sr) at ultra-trace concentration levels in swipe samples. 相似文献
1000.
James Casey 《Meccanica》2011,46(2):471-476
For motion of a material point along a space curve, a kinematical decomposition, discovered by Siacci, expresses the acceleration
vector as the sum of two special oblique components in the osculating plane to the curve. A new proof of Siacci’s theorem
is presented. 相似文献