全文获取类型
收费全文 | 270篇 |
免费 | 4篇 |
国内免费 | 5篇 |
专业分类
化学 | 149篇 |
晶体学 | 6篇 |
力学 | 11篇 |
数学 | 77篇 |
物理学 | 36篇 |
出版年
2023年 | 1篇 |
2022年 | 7篇 |
2021年 | 6篇 |
2020年 | 10篇 |
2019年 | 12篇 |
2018年 | 9篇 |
2017年 | 9篇 |
2016年 | 16篇 |
2015年 | 8篇 |
2014年 | 14篇 |
2013年 | 21篇 |
2012年 | 14篇 |
2011年 | 9篇 |
2010年 | 8篇 |
2009年 | 8篇 |
2008年 | 11篇 |
2007年 | 4篇 |
2006年 | 6篇 |
2005年 | 5篇 |
2004年 | 3篇 |
2003年 | 6篇 |
2002年 | 6篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1981年 | 5篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有279条查询结果,搜索用时 15 毫秒
101.
Thuy Bui Thi Phuong My Tran Thi Ai Hai Nguyen Thi Thanh Loan Huynh Thi Phuong Hieu Le Trung Hoa Tran Thai Bui Thanh Q. Tuong Ho Nhat Thuy Nguyen Thi Thu Dung Doan Kim Van Tat Pham Quy Phan Tu Nhung Nguyen Thi Ai 《Structural chemistry》2021,32(1):135-148
Structural Chemistry - Rice, well known as the most important staple food source worldwide, is highly susceptible to many infectious diseases, especially rice sheath blight caused by fungus... 相似文献
102.
Nguyen Ngoc-Hong Pham Duc Dung Le Thi-Thanh-Van Nguyen Thi-Anh-Tuyet Huynh Dinh-Long Duong Thuc-Huy Sichaem Jirapast 《Chemistry of Natural Compounds》2021,57(6):1038-1041
Chemistry of Natural Compounds - Seven synthetic derivatives of ursolic acid, lupeol, and betulinic acid (1a–1b, 2a–2b, and 3a–3c) were synthesized to study their... 相似文献
103.
In this paper we propose several modified hybrid projection methods for solving common solutions to variational inequality problems involving monotone and Lipschitz continuous operators. Based on differently constructed half-spaces, the proposed methods reduce the number of projections onto feasible sets as well as the number of values of operators needed to be computed. Strong convergence theorems are established under standard assumptions imposed on the operators. An extension of the proposed algorithm to a system of generalized equilibrium problems is considered and numerical experiments are also presented. 相似文献
104.
Nguyen V. Hung Dung T. Tran Nguyen C. Toan Barbara Kirchnner 《Central European Journal of Physics》2011,9(1):222-229
A thermodynamic lattice theory has been developed for determination of the melting curves and eutectic points of binary alloys.
Analytical expressions for the melting curves of binary alloys composed of constituent elements with the same structure have
been derived from expressions for the ratio of root mean square fluctuation in atomic positions on the equilibrium lattice
positions and the nearest neighbor distance. This melting curve provides information on Lindemann’s melting temperatures of
binary alloys with respect to any proportion of constituent elements, as well as on their eutectic points. The theory has
been applied to fcc and bcc structure. Numerical results for some binary alloys provide a good correspondence between the
calculated and experimental phase diagrams, where the calculated results for Cu1−x
Ni
x
agree well with the measured ones, and those for the other alloys are found to be in a reasonable agreement with experiment. 相似文献
105.
Nguyen Dang Tien Dung Fu-Sheng Chuang Kung-Jeng Wang 《Continuum Mechanics and Thermodynamics》2014,26(4):423-435
Solar energy provides significant opportunities to the power needs. The pipes with micro-grooves etched in the inner wall have been widely taken on the absorber receiver in the parabolic trough and cooling systems for solar thermal absorbers because this sort of pipes improves heat transfer. To support parabolic trough design in solar energy application systems, this study developed a capillary-driven two-phase flow model. The study further examines the influences caused by different micro-grooves, fluids, temperatures, radiuses and widths of groove. Our study concludes that (1) the triangular-microgroove has better influence of the liquid front position than semicircular-microgroove. (2) Water has better influence of liquid front position than ethanol and benzene. (3) The saturated temperature is indirectly proportional to the liquid front position. (4) The length of liquid front position is longer if value of radius is higher. (5) The width of groove does not significantly affect on the liquid front position and velocity. In addition, the proposed mathematical modeling is solved more correctly as compared to previous research. From our results, a good design of the micro-groove pipe can be achieved. 相似文献
106.
In addition to their optical properties, the ability of gold nanoparticles (Au NPs) to generate table immobilization of biomolecules, whilst retaining their bioactivities is a major advantage to apply them as biosensors. Optical biosensors using Au NPs are simple, fast and reliable and, recently, they have been moving from laboratory study to the point of practical use. The optical properties of Au NPs strongly depend on their size, shape, degree of aggregation and the functional groups on their surface. Rapid advances in the field of nanotechnology offer us a great opportunity to develop the controllable synthesis and modification of Au NPs as well as to study on their properties and applications. The size-controlled growth of Au NPs requires the isotropic growth on the surface of Au nuclei whereas anisotropic growth will induce the formation of Au NPs of varying shape. Functionalized Au NPs provide sensitive and selective biosensors for the detection of many targets, including metal ions, small organic compounds, protein, DNA, RNA and cell based on their optical, electrical or electrochemical signals. In this review, we will discuss the size- and shape-controlled growth and functionalization of Au NPs to obtain Au nanoprobes. The basis of the optical detection of Au nanoprobes and their applications in nucleic acid, protein detection and cell imaging are also introduced. 相似文献
107.
Liu CL Smith JD Che DL Ahmed M Leone SR Wilson KR 《Physical chemistry chemical physics : PCCP》2011,13(19):8993-9007
The reaction of Cl atoms, in the presence of Cl(2) and O(2), with sub-micron squalane particles is used as a model system to explore how surface hydrogen abstraction reactions initiate chain reactions that rapidly transform the chemical composition of an organic particle. The heterogeneous reaction is measured in a photochemical flow tube reactor in which chlorine atoms are produced by the photolysis of Cl(2) at 365 nm. By monitoring the heterogeneous reaction, using a vacuum ultraviolet photoionization aerosol mass spectrometer, the effective reactive uptake coefficient and the distributions of both oxygenated and chlorinated reaction products are measured and found to depend sensitively upon O(2), Cl(2), and Cl concentrations in the flow reactor. In the absence of O(2), the effective reactive uptake coefficient monotonically increases with Cl(2) concentration to a value of ~3, clearly indicating the presence of secondary chain chemistry occurring in the condensed phase. The effective uptake coefficient decreases with increasing O(2) approaching a diffusion corrected value of 0.65 ± 0.07, when 20% of the total nitrogen flow rate in the reactor is replaced with O(2). Using a kinetic model it is found that the amount of secondary chemistry and the product distributions in the aerosol phase are controlled by the competitive reaction rates of O(2) and Cl(2) with alkyl radicals. The role that a heterogeneous pathway might play in the reaction of alkyl radicals with O(2) and Cl(2) is investigated within a reasonable range of reaction parameters. These results show, more generally, that for heterogeneous reactions involving secondary chain chemistry, time and radical concentration are not interchangeable kinetic quantities, but rather the observed reaction rate and product formation chemistry depends sensitively upon the concentrations and time evolution of radical initiators and those species that propagate or terminate free radical chain reactions. 相似文献
108.
Ho Manh Dung Menno Blaauw Daniel Beasley Maria Do Carmo Freitas 《Journal of Radioanalytical and Nuclear Chemistry》2012,291(2):485-492
The k
0-based cyclic neutron activation analysis (k
0-CNAA) technique has been studied to explore the applicability at the Portuguese research reactor (RPI). In particular, for
the determination of elements which form short-lived radionuclides, particularly fluorine (20F, 11.16 s half-life) and selenium (77mSe, 17.36 s half-life) in polymer, biological and environmental samples. The detection limits obtained for F and Se were about
50 and 0.01 mg kg−1, respectively, in the investigated materials. The timing parameters for the procedure were 10 to 20 s for irradiation, 5 s
decay, 10 to 20 s counting, 5 s waiting and performed with eight cycles. The k
0-IAEA program was modified to use millisecond time resolution for irradiation, decay and counting times as needed for interpreting
k
0-CNAA data in terms of concentration, accuracy and detection limit. The quality control of the procedure was performed by
preparing a standard solution containing fluorine with different contents as well as using the certified reference materials
containing selenium from which the bias between the results and the certified values were within 15% for most elements at
the investigated content ranges. The analytical results for several other elements producing short-lived or detectable radionuclides,
e.g., Al, Ca, Cl, Cu, Dy, I, Mg, Mn, Ti, and V were also obtained by the k
0-CNAA procedure with accuracy within 12%. 相似文献
109.
HC Yeh J Sharma IeM Shih DM Vu JS Martinez JH Werner 《Journal of the American Chemical Society》2012,134(28):11550-11558
Rapid and precise screening of small genetic variations, such as single-nucleotide polymorphisms (SNPs), among an individual's genome is still an unmet challenge at point-of-care settings. One crucial step toward this goal is the development of discrimination probes that require no enzymatic reaction and are easy to use. Here we report a new type of fluorescent molecular probe, termed a chameleon NanoCluster Beacon (cNCB), that lights up into different colors upon binding SNP targets. NanoCluster Beacons (NCBs) are collections of a small number of Ag atoms templated on single-stranded DNA that fluoresce strongly when placed in proximity to particular DNA sequences, termed enhancers. Here we show the fluorescence emission color of a NCB can change substantially (a shift of 60-70 nm in the emission maximum) depending upon the alignment between the silver nanocluster and the DNA enhancer sequence. Chameleon NCBs exploit this color shift to directly detect SNPs, based on the fact that different SNPs produce a different alignment between the Ag nanocluster and the enhancer. This SNP detection method has been validated on all single-nucleotide substitution scenarios in three synthetic DNA targets, in six disease-related SNP targets, and in two clinical samples taken from patients with ovarian serous borderline tumors. Samples with single-nucleotide variations can be easily identified by the naked eye under UV excitation, making this method a reliable and low-cost assay with a simple readout format. 相似文献
110.
We give an estimate of the smallest spectral value of the Laplace operator on a complete noncompact stable minimal hypersurface
M in a complete simply connected Riemannian manifold with pinched negative sectional curvature. In the same ambient space,
we prove that if a complete minimal hypersurface M has sufficiently small total scalar curvature then M has only one end. We also obtain a vanishing theorem for L
2 harmonic 1-forms on minimal hypersurfaces in a Riemannian manifold with sectional curvature bounded below by a negative constant.
Moreover, we provide sufficient conditions for a minimal hypersurface in a Riemannian manifold with nonpositive sectional
curvature to be stable. 相似文献