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排序方式: 共有146条查询结果,搜索用时 46 毫秒
61.
Nguyen Duc Cuong Tran Thai Hoa Dinh Quang Khieu Nguyen Duc Hoa Nguyen Van Hieu 《Current Applied Physics》2012,12(5):1355-1360
The development of a low cost and scalable gas sensor for the detection of toxic and flammable gases with fast response and high sensitivity is extremely important for monitoring environmental pollution. In this work, we introduce two different synthesis pathways for the preparation of scalable Fe2O3 nanoparticles for gas sensor applications. One is co-precipitation and the other is hydrothermal method. The gas sensing properties of the α-Fe2O3 nanoparticles (NPs) fabricated by different synthesis pathways were studied and compared. The performance of the NPs in the detection of toxic and flammable gases such as carbon dioxide, ammonia, liquefied petroleum gas, ethanol, and hydrogen was evaluated. The Fe2O3 NP-based gas sensors exhibited high sensitivity and a response time of less than a minute to analytic gases. However, the NPs fabricated by the one-step direct method exhibited higher sensitivities than those generated by the α-Fe2O3 NPs obtained by co-precipitation synthesis possibly because of their nanoporous structure. This performance is attributed to the large specific surface area of the NPs, which results in higher sensitivity. 相似文献
62.
V. K. Ikonnikov P. A. Egoyants S. A. Sirotin Truong Tat Hieu 《Russian Journal of Physical Chemistry B, Focus on Physics》2010,4(8):1265-1271
The extraction of biologically active substances by carbon dioxide from various plant raw materials (amaranth seeds, Sophora japonica flower buds, Stephania rotunda stems, and Stevia rebaudiana leaves) was studied at sub- and supercritical parameters. A laboratory unit for the extraction of plant raw materials by
liquefied gases and supercritical fluids at 5–35 MPa pressures and 285–350 K temperatures was developed. The maximum yield
of the extracted substances from plants specified was obtained at temperature and pressure exceeding the critical parameters
of CO2 (320–330 K, 28–30 MPa). 相似文献
63.
Vu Van Hung Tran Xuan Linh Vu Thi Thanh Ha Duong Dai Phuong Ho Khac Hieu 《The European Physical Journal B - Condensed Matter and Complex Systems》2018,91(2):44
The elastic moduli and elastic constants of the ternary semiconductor alloy Al y Ga1-yAs at finite temperature have been investigated using the statistical moment method. The Young, shear, bulk moduli and elastic constants C11, C12, C44 of the zinc-blende Al y Ga1?yAs crystal are calculated as functions of Al composition and temperature. Numerical calculations have been performed and compared with those of the experimental and other theoretical results showing the reasonable agreements. Our study shows that elastic moduli and C11, C12 constants of zinc-blende Al y Ga1?yAs alloy are decreasing functions of the temperature and Al composition; C44 constant is a decreasing function of the Al composition. 相似文献
64.
In this paper, the nonlinear random vibration of a uniform beam clamped at both of its ends is investigated by the regulated stochastic linearization technique. A closed system of nonlinear algebraic equations for linearization coefficients is obtained using the frequency–response function matrix. Root mean-square response of maximum deflection of the beam that is obtained from the present technique is subsequently compared with that furnished by the conventional linearization. The numerical results show that the regulated stochastic linearization technique constitutes an excellent alternative to the classical linearization scheme for analyzing responses of the clamped–clamped beam. 相似文献
65.
ZnO nanorods, nanobelts, nanowires, and tetrapod nanowires were synthesized via thermal evaporation of Zn powder at temperatures in the range 550-600 °C under flow of Ar or Ar/O2 as carrier gas. Uniform ZnO nanowires with diameter 15-25 nm and tetrapod nanowires with diameter 30-50 nm were obtained by strictly controlling the evaporation process. Our experimental results revealed that the concentration of O2 in the carrier gas was a key factor to control the morphology of ZnO nanostructures. The gas sensors fabricated from quasi-one-dimensional (Q1D) ZnO nanostructures exhibited a good performance. The sensor response to 500 ppm ethanol was up to about 5.3 at the operating temperature 300 °C. Both response and recovery times were less than 20 s. The gas-sensing mechanism of the ZnO nanostructures is also discussed and their potential application is indicated accordingly. 相似文献
66.
Formation and stabilization of persistent free radicals 总被引:2,自引:0,他引:2
Barry Dellinger Slawomir Lomnicki Lavrent Khachatryan Zofia Maskos Randall W. Hall Julien Adounkpe Cheri McFerrin Hieu Truong 《Proceedings of the Combustion Institute》2007,31(1):521-528
We demonstrate that stable and relatively unreactive “environmentally persistent free radicals (PFRs)” can be readily formed in the post-flame and cool-zone regions of combustion systems and other thermal processes. These resonance-stabilized radicals, including semiquinones, phenoxyls, and cyclopentadienyls, can be formed by the thermal decomposition of molecular precursors including catechols, hydroquinones and phenols. Association with the surfaces of fine particles imparts additional stabilization to these radicals such that they can persist almost indefinitely in the environment. A mechanism of chemisorption and electron transfer from the molecular adsorbate to a redox-active transition metal or other receptor is shown through experiment, and supported by molecular orbital calculations, to result in PFR formation. Both oxygen-centered and carbon-centered PFRs are possible that can significantly affect their environmental and biological reactivity. 相似文献
67.
Kwang-Fu Shen C Duong HM Sonmez G Wudl F 《Journal of the American Chemical Society》2003,125(52):16206-16207
TTF produces two completely different phenomena with the different isomers of chloranil; with the para isomer it produces an insulating, alternating stack, ambient temperature neutral solid. While with the ortho isomer, it produces a more interesting system consisting of interconvertible conducting ionic and covalent components. 相似文献
68.
Goowon Yang Minhyeok Song Dang Hieu Hoang Quynh Hoa Tran Wonchae Choe Insug Kang Sung Soo Kim Joohun Ha 《Experimental & molecular medicine》2020,52(12):2055
The clinical application of doxorubicin, one of the most effective anticancer drugs, has been limited due to its adverse effects, including cardiotoxicity. One of the hallmarks of doxorubicin-induced cytotoxicity is mitochondrial dysfunction. Despite intensive research over recent decades, there are no effective approaches for alleviating doxorubicin-induced cytotoxicity. Melatonin, a natural hormone that is primarily secreted by the pineal gland, is emerging as a promising adjuvant that protects against doxorubicin-induced cytotoxicity owing to its pharmaceutical effect of preserving mitochondrial integrity. However, the underlying mechanisms are far from completely understood. Here, we provide novel evidence that treatment of H9c2 cardiomyoblasts with doxorubicin strongly induced AMP-activated protein kinase α2 (AMPKα2), which translocated to mitochondria and interfered with their function and integrity, ultimately leading to cellular apoptosis. These phenomena were significantly blocked by melatonin treatment. The levels of AMPKα2 in murine hearts were tightly associated with cardiotoxicity in the context of doxorubicin and melatonin treatment. Therefore, our study suggests that the maintenance of mitochondrial integrity is a key factor in reducing doxorubicin-induced cytotoxicity and indicates that AMPKα2 may serve as a novel target in the design of cytoprotective combination therapies that include doxorubicin.Subject terms: Biochemistry, Diseases 相似文献
69.
Lee GS Bashara JN Sabih G Oganesyan A Godjoian G Duong HM Marinez ER Gutiérrez CG 《Organic letters》2004,6(11):1705-1707
New adamantane derivatives 1 and 2 that bear functionalized one-carbon extensions at all four bridgehead positions have been prepared. Radical nucleophilic substitution (S(RN)1) reaction of 1,3,5,7-tetrabromoadamantane with cyanide produces 1,3,5,7-tetracyanoadamantane (1), which was reduced with borane reagents to 1,3,5,7-tetrakis(aminomethyl)adamantane (2). Improvements in the preparation of 1,3,5,7-tetrahaloadamantanes (halogen = Br, Cl, I) are also reported. [structure--see text] 相似文献
70.