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991.
Formic and acetic acids are ubiquitous in the environment, food, and most of the natural products. Extraction of the acids from aqueous solution is required for their isotope analysis by the gas chromatography-isotope ratio mass spectrometry. To this objective, we have previously developed a purge-and-trap technique using the dynamic solid-phase microextraction technology, the NeedlEX. The extraction efficiency, however, remains unexamined. Here, we address this question using the flame ionization detector and isotope ratio mass spectrometer while comparing it with that of the CAR/PDMS fiber. The results show that the NeedlEX is applicable at a wide range of concentration through coordination of purge volume given the minimum amount 3.7 ng and 1.8 ng of formic and acetic, respectively, is extracted. The efficiency of NeedlEX was 6-7 times lower than the fiber at 1000 μg/mL depending on the analyte. It is, however, superior to the latter at 10 μg/mL or less owing to its lower detection limit. The extraction efficiency of both acids is equivalent in molar amount. This is, however, disguised by the different response of the flame ionization detector. The isotope ratio mass spectrometor overcomes this problem but is compromised by relatively large errors. These results are particularly useful for isotopic analysis of carboxylic acids. 相似文献
992.
993.
Different stable geometric configurations of Ge doped amorphous SiO2 (a-SiO2) system, originating from one, two, or three Si atoms in various places of the a-SiO2 substituted by Ge atoms randomly have been investigated using interatomic potentials in this work. The most stable structures have been identified and corresponding evolutional rules obtained. The structural growth pattern for Ge-doped a-SiO2 system is that Ge atoms tend to spread far away from each other and keep away from the center. Furthermore, the thermodynamic properties including speci?c heat, Debye temperature, vibrational entropy, and so on are calculated from the structure with 16 Si atoms of the constructed a-SiO2 cell replaced by Ge atoms and with the biggest Ge-Ge distance. It can be seen that entropy of Ge doped system with larger specific heat is higher than that of the pure system with smaller specific heat. At last, optical properties including optical absorption spectrum and electron energy loss function of nGe-doped a-SiO2 (n=0-3, 8) system is also obtained. 相似文献
994.
The development of new optical anion chemosensors with high sensitivity and selectivity is very important, since anions possess some fundamental roles in a wide range of biological and chemical processes. The displacement approach is a method using anion binding sites and signaling subunits, which are not covalently attached but forming a coordination complex, in which the presence of anions revives the noncoordinated spectroscopic behavior of the indicator. In the past five years, according to the displacement strategy, many good optical anion chemosensors have been successfully obtained. This paper reviews the recent progress in the field of the fluorescent and colorimetric anion chemosensors designed according to the displacement strategy (mainly from 2008 to 2011), and gives some outlooks for the further exploration of new optical anion chemosensors. 相似文献
995.
996.
White organic light-emitting diodes based on a combined electromer and monomer emission in doubly-doped polymers
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We report on white organic light-emitting diodes(WOLEDs) based on polyvinylcarbazole(PVK) doped with 1,1-bis((di-4-tolylamino)phenyl)cyclohexane(TAPC) and perylene,and investigate the luminescence mechanism of the devices.The chromaticity of light emission can be tuned by adjusting the concentration of the dopants.White light with the Commission Internationale de L’Eclairage(CIE) coordinates of(0.33,0.34) is achieved by mixing the yellow electromer emission of TAPC and the blue monomer emission of perylene from the device ITO/PVK:TAPC:perylene(100:9:1 in wt.)(100 nm)/tris-(8-hydroxyquinoline aluminum(Alq 3)(10 nm)/Al.The device exhibits a maximal luminance of 3727 cd/m2 and a current efficiency of 2cd/A. 相似文献
997.
C Zhang HB Wu C Yuan Z Guo XW Lou 《Angewandte Chemie (International ed. in English)》2012,51(38):9592-9595
Going into their shell: A novel carbon-sulfur nanocomposite has been synthesized by confining sulfur in double-shelled "soft" carbon hollow spheres with high surface area and porosity. This carbon-sulfur nanocomposite shows outstanding electrochemical performance when evaluated as a cathode material for lithium-sulfur batteries. 相似文献
998.
Der-Chyuan Lou Chao-Lung Chou Hao-Kuan Tso Chung-Cheng Chiu 《Optics Communications》2012,285(10-11):2510-2518
This paper presents an innovative active steganalysis algorithm for reversible data hiding schemes based on histogram shifting. These schemes use histogram shifting to embed secret data in cover-images. However, some histogram patterns originating during the embedding procedure may be recognized readily by a steganalyst. The proposed algorithm analyzes the characteristics of histogram changing during the data embedding procedure, and then models these features into reference templates by using a 1 × 4 sliding window. A support vector machine is trained as the classifier for discriminating between cover-images and stego-images by adopting the template matching techniques. The hidden messages located at the histogram peak of the cover-image were further estimated by measuring the feature of adjacent histogram differences. Experimental results indicate that the proposed active steganalysis algorithm can effectively detect stego-images at low bit rates and estimate the hidden messages locations. 相似文献
999.
Yan?ZhaoEmail author Yan-Lin?Liao Ping?Lou 《International Journal of Theoretical Physics》2012,51(7):2109-2112
We propose a concentration scheme of the W class state via cavity QED technique. In our scheme the influences of cavity decay and atomic spontaneous emission have been considered. Furthermore, the atomic spontaneous emission has been suppressed by using non-radiative transitions in atoms with three-level structure, and the photonic qubit is used as flying qubit and atomic qubit as stationary qubit. Therefore our scheme is comparatively easy to realize within techniques presently available. 相似文献
1000.
Varnum SM Warner MG Dockendorff B Anheier NC Lou J Marks JD Smith LA Feldhaus MJ Grate JW Bruckner-Lea CJ 《Analytica chimica acta》2006,570(2):137-143
Two immunoassay platforms were developed for either the sensitive or rapid detection of botulinum neurotoxin A (BoNT/A), using high-affinity recombinant monoclonal antibodies against the receptor binding domain of the heavy chain of BoNT/A. These antibodies also bind the same epitopes of the receptor binding domain present on a nontoxic recombinant heavy chain fragment used for assay development and testing in the current study. An enzyme-linked immunosorbent assay (ELISA) microarray using tyramide amplification for localized labeling was developed for the specific and sensitive detection of BoNT. This assay has the sensitivity to detect BoNT in buffer and blood plasma samples down to 14 fM (1.4 pg mL−1). Three capture antibodies and one antibody combination were compared in the development of this assay. Using a selected pair from the same set of recombinant monoclonal antibodies, a renewable surface microcolumn sensor was developed for the rapid detection of BoNT/A in an automated fluidic system. The ELISA microarray assay, because of its sensitivity, offers a screening test with detection limits comparable to the mouse bioassay, with results available in hours instead of days. The renewable surface assay is less sensitive but much faster, providing results in less than 10 min. 相似文献