全文获取类型
收费全文 | 3485篇 |
免费 | 205篇 |
国内免费 | 17篇 |
专业分类
化学 | 2441篇 |
晶体学 | 13篇 |
力学 | 76篇 |
数学 | 602篇 |
物理学 | 575篇 |
出版年
2023年 | 29篇 |
2022年 | 39篇 |
2021年 | 61篇 |
2020年 | 79篇 |
2019年 | 76篇 |
2018年 | 70篇 |
2017年 | 76篇 |
2016年 | 177篇 |
2015年 | 138篇 |
2014年 | 122篇 |
2013年 | 224篇 |
2012年 | 266篇 |
2011年 | 281篇 |
2010年 | 164篇 |
2009年 | 117篇 |
2008年 | 230篇 |
2007年 | 196篇 |
2006年 | 171篇 |
2005年 | 171篇 |
2004年 | 152篇 |
2003年 | 137篇 |
2002年 | 124篇 |
2001年 | 39篇 |
2000年 | 29篇 |
1999年 | 37篇 |
1998年 | 37篇 |
1997年 | 25篇 |
1996年 | 39篇 |
1995年 | 15篇 |
1994年 | 24篇 |
1993年 | 28篇 |
1992年 | 18篇 |
1991年 | 15篇 |
1990年 | 15篇 |
1989年 | 11篇 |
1988年 | 19篇 |
1987年 | 14篇 |
1986年 | 14篇 |
1985年 | 32篇 |
1984年 | 24篇 |
1983年 | 12篇 |
1982年 | 14篇 |
1981年 | 10篇 |
1980年 | 11篇 |
1979年 | 20篇 |
1978年 | 13篇 |
1977年 | 12篇 |
1975年 | 10篇 |
1974年 | 13篇 |
1973年 | 13篇 |
排序方式: 共有3707条查询结果,搜索用时 31 毫秒
71.
72.
Summary We prove that every mixing
d
by automorphisms of a compact, connected, abelian group is mixing of all orders.Oblatum 5-II-1992The second author gratefully acknowledges support from NSF grant DMS-91-03056 at the Ohio State University 相似文献
73.
研究了基于微芯片电泳分离和电感耦合等离子体质谱的连接技术,并对不同形态的Cu和As进行了快速分离和检测. 相似文献
74.
New boracites containing nitrato- or fluoroanions that appear to be true low-pressure phases have been synthesized at superatmospheric pressures. The M3B7O13NO3 compounds (M = Co, Ni, Cu, Zn, Cd) transform rapidly and reversibly in the temperature region 300–500°C between probable orthorhombic and face centered cubic symmetry, while the M3B7O13F compounds (M = Mg, Mn, Fe, Co, Zn) appear to maintain rhombohedral symmetry up to their decomposition temperatures of 800–900°C. True high-pressure boracite-like phases containing F and Cr, Mn, Fe, or Co that decompose upon heating to M3B7O13F have also been isolated. 相似文献
75.
76.
Tomás Moya-Pizarro Roger Salmon Léopold Fournes Gilles Le Flem Barbara Wanklyn Paul Hagenmuller 《Journal of solid state chemistry》1984,53(3):387-397
Single crystals of the high-temperature form of NaFeP2O7 have been grown by a flux technique. II-NaFeP2O7 crystallizes in the monoclinic space group with lattice parameters: a = 7.298(2) Å, b = 7.874(2) Å, c = 9.536(3) Å, β = 111.85(2)°. The structure refined from 1481 independent reflections leads to R = 0.044 and confirms the work previously published by M. Gabelica-Robert, M. Goreaud, P. Labbe, and B. Raveau (J. Solid State Chem.45, 389, 1982). Magnetic Mössbauer resonance studies have shown the existence of antiferromagnetic ordering with a weak ferromagnetic component below 30 K. The FeO bond is markedly ionic in character due to the highly polarizing power of phosphorus in tetrahedral site. 相似文献
77.
Macho S Miguel D Neo AG Rodriguez T Torroba T 《Chemical communications (Cambridge, England)》2005,(3):334-336
Indene and cyclopentene enaminonitriles were reacted with SCl2, iBu3N and NCS to give the first cyclopenta[1,2,6]thiadiazines that showed unusual characteristics, one as a NIR dye and another as a liquid crystal. 相似文献
78.
Burke AJ Davies SG Garner AC McCarthy TD Roberts PM Smith AD Rodriguez-Solla H Vickers RJ 《Organic & biomolecular chemistry》2004,2(9):1387-1394
Conjugate addition of lithium (S)-N-benzyl-N-alpha-methylbenzylamide to a range of alpha, beta-unsaturated Weinreb amides proceeds with high levels of diastereoselectivity (>95% de). The beta-amino Weinreb amide products may be transformed into beta-amino ketones via reactions with Grignard reagents, while treatment with DIBAL-H furnishes beta-amino aldehydes. Trapping of the aldehyde via Wadsworth-Emmons reaction and subsequent manipulation offers an efficient route to homochiral delta-amino acid derivatives and 2-substituted piperidines. The application of this methodology for the synthesis of (S)-coniine is demonstrated. 相似文献
79.
Isotypic pseudooctahedral complexes of Co, Ni, and Cu with two chelating oxalurate ligands and two water molecules, trans-[M(oxalurate)(2)(H(2)O)(2)], have been synthesized and isolated by a novel progressive crystallization technique. Diffraction analyses reveal that the three complexes form isotypic solid-state structures in which the molecular connectivity and complex network of noncovalent interactions are qualitatively identical throughout the series. The oxalurate groups form unbounded chains through two different self-recognition patterns-a typical DA-AD motif and an unusual DDA'-A'DD form (D = hydrogen bond donor, A' = double acceptor). The unsymmetrical oxalurate group possesses the topological properties necessary to form aggregates of higher symmetry, and the "M(oxalurate)(2)" fragments form a rhombic 2-D motif with hydrogen-bonded corners and with hydrogen-bond acceptors directed to the inside of the cyclic aggregate. The 2-D net is stacked to form a channeled 3-D structure, in which the coordinated aqua ligands form the principal interlayer interactions. The slanted channels are occupied by the axial waters and by waters of crystallization, which are hydrogen bonded to the channel walls to form an ordered bushing. The extensive 3-D hydrogen-bonded superstructure is flexible enough to accommodate the distortion produced by the Jahn-Teller effect in the copper compound without requiring a qualitative structural change. The bonds affected by Jahn-Teller distortion in the Cu complex [Cu-O = 2.3788(15) A] are significantly longer than their analogues in the Co and Ni complexes [Co-O = 2.175(2), Ni-O = 2.094(9) A]. 相似文献
80.
With the use of the tritium monitoring network the samples of river water, air humidity and precipitation are collected and analysed for HTO in the vicinity of Temelín nuclear power plant. 相似文献