全文获取类型
收费全文 | 839篇 |
免费 | 21篇 |
国内免费 | 14篇 |
专业分类
化学 | 497篇 |
晶体学 | 14篇 |
力学 | 43篇 |
数学 | 124篇 |
物理学 | 196篇 |
出版年
2023年 | 6篇 |
2022年 | 17篇 |
2021年 | 16篇 |
2020年 | 19篇 |
2019年 | 17篇 |
2018年 | 22篇 |
2017年 | 16篇 |
2016年 | 20篇 |
2015年 | 17篇 |
2014年 | 30篇 |
2013年 | 50篇 |
2012年 | 67篇 |
2011年 | 56篇 |
2010年 | 40篇 |
2009年 | 29篇 |
2008年 | 46篇 |
2007年 | 47篇 |
2006年 | 52篇 |
2005年 | 39篇 |
2004年 | 24篇 |
2003年 | 36篇 |
2002年 | 23篇 |
2001年 | 12篇 |
2000年 | 5篇 |
1999年 | 8篇 |
1998年 | 7篇 |
1997年 | 9篇 |
1996年 | 7篇 |
1994年 | 8篇 |
1993年 | 10篇 |
1992年 | 10篇 |
1991年 | 3篇 |
1990年 | 11篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1970年 | 3篇 |
1969年 | 3篇 |
1968年 | 5篇 |
1961年 | 4篇 |
1960年 | 4篇 |
1958年 | 3篇 |
1948年 | 3篇 |
排序方式: 共有874条查询结果,搜索用时 15 毫秒
791.
Chikkamath Santosh S. Patil Dinesh M. Kabadagi Anand S. Tripathi Vaidehi S. Kar Aishwarya S. Manjanna Jayappa 《Journal of Radioanalytical and Nuclear Chemistry》2019,321(3):1027-1034
Journal of Radioanalytical and Nuclear Chemistry - In this study, simple and a rapid solvent extraction method is investigated to recover Mo(VI) from simulated HLLW. The (NH4)6Mo7O24·4H2O... 相似文献
792.
Selvam Athavan Alias Anand Kiran George Nisha Susan Thomas 《Phosphorus, sulfur, and silicon and the related elements》2020,195(10):821-829
AbstractTwo series of thiazinone and thiosemicarbazone derivatives (1-12) were synthesized using 2,4-diaryl-3-azabicyclo[3.3.1]nonan-9-ones (ABNs) and 3–alkyl–2,6–diarylpiperidin–4–ones as the starting materials. The structures of newly synthesized compounds were established on the basis of FT–IR, NMR spectroscopy and mass spectrometry. From the spectroscopic data, we identified that the cyclization reaction of thioamide with dialkyl acetylenedicarboxylate selectively gives six membered methyl 2-(2-(2,4-disubstituted-3-azabicyclo[3.3.1]nonan-9-ylidene)hydrazinyl)-4-oxo-4H-1,3-thiazine-6-carboxylates (1-6). In order to investigate the antitumor activities of the synthesized compounds, in vitro cytotoxicity studies were carried out using human prostate cancer cell lines. Tested compounds showed good/moderate activities against cancer cell lines and further investigation carried out by live/dead assay. 相似文献
793.
A. Anand L. Nussana M. P. Sham Aan K. Ekwipoo S. G. Sangashetty 《Journal of Macromolecular Science: Physics》2020,59(11):697-712
AbstractNanoparticles of zinc oxide were synthesized by a solution combustion method. The average size of these particles was analyzed by using X-ray diffraction. Composites of natural rubber and the ZnO nanoparticles were prepared by a latex blending method. The matrix phase was cured by using the crosslinking agent, pentane-1,5-diylidenediamine. Effects of crosslinking and incorporation of nanoparticles on the tensile and solvent transport properties of the natural rubber were studied in detail. The nature of the dispersion of the nanoparticles was analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). It was observed from the tensile studies that the addition of the curing agent and the ZnO nanoparticles increased the stability considerably. Incorporation of the nanoparticles also considerably increased the solvent resistance of the cured natural rubber. We suggest the addition of ZnO nanoparticles at a low loading level provided better properties compared to other reinforcements, such as carbon black and nano-clay. 相似文献
794.
Ya'acov Peterzil Anand Pillay Sergei Starchenko 《Transactions of the American Mathematical Society》2000,352(10):4421-4450
We continue the investigation of infinite, definably simple groups which are definable in o-minimal structures. In Definably simple groups in o-minimal structures, we showed that every such group is a semialgebraic group over a real closed field. Our main result here, stated in a model theoretic language, is that every such group is either bi-interpretable with an algebraically closed field of characteristic zero (when the group is stable) or with a real closed field (when the group is unstable). It follows that every abstract isomorphism between two unstable groups as above is a composition of a semialgebraic map with a field isomorphism. We discuss connections to theorems of Freudenthal, Borel-Tits and Weisfeiler on automorphisms of real Lie groups and simple algebraic groups over real closed fields.
795.
K. N. Murty P. V. S. Anand V. Lakshmi Prasannam 《Proceedings of the American Mathematical Society》1997,125(12):3533-3539
In this paper, the general solution of the homogeneous matrix difference system is constructed in terms of two fundamental matrix solutions. The general solution of the inhomogeneous matrix difference system is established by the variation of parameters formula. A unique solution of the two-point boundary value problem associated with the matrix difference system is constructed by applying the QR-algorithm and the Bartels-Stewart algorithm.
796.
We present the design, fabrication, and measurement of an ultracompact directional coupler in InP/InGaAsP/InP. By utilizing the lag effect in the dry etching process, in one etch step, deeply etched asymmetric waveguides with a shallow groove in between are fabricated. This special property enhances the coupling efficiency for the directional coupler and thus makes the device ultracompact. We demonstrate directional couplers as short as 55 microm, which is only 1/30th the length of the conventional design. 相似文献
797.
798.
Anand Paul 《Journal of Mathematical Analysis and Applications》2003,284(1):397-402
We prove that an absolutely continuous probability distribution with compact support is uniformly distributed if and only if the mean sample spacings resulting from a random sample of size N are all equal for every integer N. We also present a related characterization of uniformity using nonlinear transformations. We discuss potential applications of these results to hypothesis testing and to testing the effectiveness of different random number generators. 相似文献
799.
800.
J. Anand Subramony 《Solid State Communications》2004,132(12):827-830
We previously determined the crystal structures of the high temperature phases of KH2PO4 [J.A. Subramony, S. Lovell, B. Kahr, Chem. Mater. 10 (1998) 2053. [6]]. These triclinic and monoclinic phases were obtained by heating the room temperature tetragonal form until new crystal phases were identified by polarization microscopy. These samples were subsequently cooled to room temperature thereby preserving the metastable high temperature phases for analysis. KD2PO4 is distinct from KH2PO4 in that it crystallizes at room temperature in a monoclinic phase unknown for its isotopomer, therefore the question as to whether it would support the corresponding high temperature phases remained open until our report here of the transformation of monoclinic KD2PO4 to an isomorphous triclinic high temperature phase: space group P with a=7.475(1) Å, b=7.440(1) Å, c=7.184(1) Å, α=88.53(1) Å, β=86.81(1)°, γ=88.09(1)°, V=398.58 Å3. This is the first known high temperature phase of DKDP, a material coveted at room temperature for its optical properties. 相似文献