全文获取类型
收费全文 | 371篇 |
免费 | 8篇 |
国内免费 | 5篇 |
专业分类
化学 | 210篇 |
力学 | 14篇 |
数学 | 52篇 |
物理学 | 108篇 |
出版年
2022年 | 7篇 |
2021年 | 11篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 10篇 |
2016年 | 10篇 |
2015年 | 9篇 |
2014年 | 8篇 |
2013年 | 18篇 |
2012年 | 18篇 |
2011年 | 26篇 |
2010年 | 17篇 |
2009年 | 16篇 |
2008年 | 21篇 |
2007年 | 23篇 |
2006年 | 31篇 |
2005年 | 24篇 |
2004年 | 26篇 |
2003年 | 15篇 |
2002年 | 14篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 8篇 |
1996年 | 14篇 |
1995年 | 7篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有384条查询结果,搜索用时 15 毫秒
1.
Statistical Inference for Stochastic Processes - We propose a randomized approach to the consistent statistical analysis of random processes and fields on $${\mathbb {R}}^m$$ and $${\mathbb {Z}}^m,... 相似文献
2.
Gusev AI Wilkinson WR Proctor A Hercules DM 《Analytical and bioanalytical chemistry》1996,354(4):455-463
The protocol and various matrices were examined for quantification of biomolecules in both the low ca. 1200 amu and mid mass 6000-12000 amu ranges using an internal standard. Comparative studies of different matrices of MALDI quantitative analysis showed that the best accuracy and standard curve linearity were obtained for two matrices: (a) 2,5-dihydroxybenzoic acid (DHB) combined with a comatrix of fucose and 5-methoxysalicylic acid (MSA) and (b) ferulic acid/fucose. In the low mass range, the quantitative limit was in the 30 fmol range and in the mid mass range the quantitative limit was in the 250 fmol range. Linear response was observed over 2-3 decades of analyte concentration. The relative error of the standard curve slope was 1.3-1.8% with correlation coefficients of 0.996-0.998.The main problem for quantitative measurement was suppression of the signal of the less concentrated component (analyte or internal standard) by the more concentrated component. The effect was identified with saturation of the matrix by the analyte. The threshold of matrix saturation was found to be in the range of 1/(3000-5000) analyte/matrix molar ratio. To avoid matrix saturation the (analyte+internal standard) to matrix molar ratio should be below this threshold. Thus the internal standard concentration should be as low as possible.DHB/MSA/fucose and ferulic acid/fucose matrices demonstrated good accuracy and linearity for standard curves even when the internal standard had chemical properties different from the analyte. However, use of an internal standard with different chemical properties requires highly stable instrumental parameters as well as constant (analyte+internal standard)/matrix molar ratio for all samples. 相似文献
3.
Crawford MJ Ellern A Karaghiosoff K Mayer P Nöth H Suter M 《Inorganic chemistry》2004,43(22):7120-7126
The synthesis and characterization of the dioxouranium(VI) dibromide and iodide hydrates, UO(2)Br(2)x3H(2)O (1), [UO(2)Br(2)(OH(2))(2)](2) (2), and UO(2)I(2)x2H(2)Ox4Et(2)O (3), are reported. Moreover, adducts of UO(2)I(2) and UO(2)Br(2) with large, bulky OP(NMe(2))(3) and OPPh(3) ligands such as UO(2)I(2)(OP(NMe(2))(3))(2) (4), UO(2)Br(2)(OP(NMe(2))(3))(2) (5), and UO(2)I(2)(OPPh(3))(2)(6) are discussed. The structures of the following compounds were determined using single-crystal X-ray diffraction techniques: (1) monoclinic, P2(1)/c, a = 9.7376(8) A, b = 6.5471(5) A, c = 12.817(1) A, beta = 94.104(1) degrees , V = 815.0(1) A(3), Z = 4; (2) monoclinic, P2(1)/c, a = 6.0568(7) A, b = 10.5117(9) A, c = 10.362(1) A, beta = 99.62(1) degrees , V = 650.5(1) A(3), Z = 2; (4) tetragonal, P4(1)2(1)2, a = 10.6519(3) A, b = 10.6519(3) A, c = 24.0758(6) A, V = 2731.7(1) A(3), Z = 4; (5) tetragonal, P4(1)2(1)2, a = 10.4645(1) A, b = 10.4645(1) A, c = 23.7805(3) A, V = 2604.10(5) A(3), Z = 4, and (6) monoclinic, P2(1)/c, a = 9.6543(1) A, b = 18.8968(3) A, c = 10.9042(2) A, beta =115.2134(5) degrees , V = 1783.01(5) A(3), Z = 2. Whereas 1 and 2 are the first UO(2)Br(2) hydrates and the last missing members of the UO(2)X(2) hydrate (X = Cl --> I) series to be structurally characterized, 4 and 6 contain room-temperature stable U(VI)-I bonds with 4 being the first structurally characterized room temperature stable U(VI)-I compound which can be conveniently prepared on a gram scale in quantitative yield. The synthesis and characterization of 5 using an analogous halogen exchange reaction to that used for the preparation of 4 is also reported. 相似文献
4.
Pikovsky AS 《Chaos (Woodbury, N.Y.)》1993,3(2):225-232
Local Lyapunov exponents are proposed for characterization of perturbations in distributed dynamical systems with chaotic behavior. Their relation to usual and velocity-dependent exponents is discussed. Local Lyapunov exponents are analytically calculated for coupled map lattices using random field approximation. Boundary Lyapunov exponents describing reflection of perturbations at boundaries are also introduced and calculated. 相似文献
5.
6.
Ilya I. Moiseev Tatiana A. Stromnova Irina N. Busygina Natalya Yu. Tihonova Natalya Yu. Kozitsyna Arkady M. Ellern Mikhail Yu. Antipin Yury T. Struchkov 《Journal of Cluster Science》1992,3(4):411-421
Thermolysis of tetranuclear palladium clusters Pd4(-Q)4 Pd4(-Q)4(-O2CR)4 (Q=CPh2 or CO;R=Me, CMe3, Ph, CH2Cl or CF3) has been found to involve innersphere oxidation of carbene or carbonyl ligands during which an oxygen atom transfer occurs from the carboxylate group to the carbene or carbonyl ligand. The thermolysis of the carbonyl clusters gives rise to the products of CO2 insertion into the C–H bond of benzene or toluene used as solvents forming benzoic acid from benzene and a mixture of phenylacetic and toluic acids from toluene. The reaction of [Pd(OAc)2(PPh3)]2 with HCO2H includes the transfer of an O atom from formate ligand to the P atom and cleavage of the P-Ph bond accompanied by transfer of the Ph group from PPh3 ligand to the palladium atom. The structure of the complex formed, [Pd(-O2PPh2)(C6H5)(PPh3)]2, has been resolved by X-ray analysis. 相似文献
7.
Alexander V. Gusakov Arkady P. Sinitsyn Alejandro G. Berlin Nonna N. Popova Alexander V. Markov Oleg N. Okunev Dmitry F. Tikhomirov Mark Emalfarb 《Applied biochemistry and biotechnology》1998,75(2-3):279-293
A model microassay system was developed to measure indigo backstaining on cotton fabrics in the presence of enzymes on a small
laboratory scale. Backstaining indexes for 11 cellulase samples were measured, and the enzymes were ranked from lower to higher
backstaining. Two multienzyme cellulase preparations were separated into fractions using chromatofocusing on a Mono P column.
Adsorption ability and backstaining properties of purified enzyme fractions were studied. Evidence was obtained that protein
adsorption on cotton fabrics is a crucial parameter causing backstaining (both for crude cellulase samples and purified enzyme
components). 相似文献
8.
Alex Berlin Neil Gilkes Douglas Kilburn Vera Maximenko Renata Bura Alexander Markov Anton Skomarovsky Alexander Gusakov Arkady Sinitsyn Oleg Okunev Irina Solovieva John N. Saddler 《Applied biochemistry and biotechnology》2006,130(1-3):528-545
Seven cellulase preparations from Penicillium and Trichoderma spp. were evaluated for their ability to hydrolyze the cellulose fraction of hardwoods (yellow poplar and red maple) pretreated by organosolv extraction, as well as model cellulosic substrates such as filter paper. There was no significant correlation among hydrolytic performance on pretreated hardwood, based on glucose release, and filter paper activity. However, performance on pretreated hardwood showed significant correlations to the levels of endogenous β-glucosidase and xylanase activities in the cellulase preparation. Accordingly, differences in performance were reduced or eliminated following supplementation with a crude β-glucosidase preparation containing both activities. These results complement a previous investigation using softwoods pretreated by either organosolv extraction or steam explosion. Cellulase preparations that performed best on hardwood also showed superior performance on the softwood substrates. 相似文献
9.
John Fielden Patrick T. Gunning De-Liang Long Margaret Nutley Arkady Ellern Paul Kgerler Leroy Cronin 《Polyhedron》2006,25(18):3474-3480
The coordination chemistry of the tetradentate pyridyl N-donor ligand cis-3,5-bis-[2-pyridinyleneamin]-trans-hydroxycyclohexane (DDOP) has been investigated with zinc(II) nitrate and triflate. The resulting complexes, [Zn(DDOP)(H2O)(NO3)](NO3) (1), and [Zn(DDOP)(H2O)(OTf)](OTf) (2) differ not only in their counterions, but also the arrangement of the axial ligands and their solid state hydrogen bonded networks. Isothermal titration calorimetry was used to assess the difference in binding properties exhibited by the two zinc complexes at physiological pH in an aqueous environment. A series of coordinating amino acids were found to preferentially bind to the mononuclear zinc triflate (1) complex over the corresponding nitrate (2) assembly, with histidine exhibiting a two centre binding mode. 相似文献
10.