全文获取类型
收费全文 | 3684篇 |
免费 | 142篇 |
国内免费 | 23篇 |
专业分类
化学 | 2545篇 |
晶体学 | 31篇 |
力学 | 82篇 |
数学 | 589篇 |
物理学 | 602篇 |
出版年
2023年 | 28篇 |
2022年 | 51篇 |
2021年 | 117篇 |
2020年 | 73篇 |
2019年 | 84篇 |
2018年 | 73篇 |
2017年 | 55篇 |
2016年 | 125篇 |
2015年 | 113篇 |
2014年 | 136篇 |
2013年 | 228篇 |
2012年 | 220篇 |
2011年 | 310篇 |
2010年 | 181篇 |
2009年 | 161篇 |
2008年 | 220篇 |
2007年 | 215篇 |
2006年 | 182篇 |
2005年 | 169篇 |
2004年 | 145篇 |
2003年 | 109篇 |
2002年 | 121篇 |
2001年 | 55篇 |
2000年 | 50篇 |
1999年 | 39篇 |
1998年 | 29篇 |
1997年 | 29篇 |
1996年 | 33篇 |
1995年 | 32篇 |
1994年 | 36篇 |
1993年 | 35篇 |
1992年 | 20篇 |
1991年 | 27篇 |
1990年 | 25篇 |
1989年 | 19篇 |
1988年 | 22篇 |
1987年 | 17篇 |
1986年 | 29篇 |
1985年 | 31篇 |
1984年 | 28篇 |
1983年 | 24篇 |
1982年 | 28篇 |
1981年 | 20篇 |
1980年 | 15篇 |
1979年 | 14篇 |
1978年 | 15篇 |
1977年 | 9篇 |
1976年 | 7篇 |
1975年 | 9篇 |
1974年 | 9篇 |
排序方式: 共有3849条查询结果,搜索用时 31 毫秒
51.
Ramiro Pino Olivier Bokanowski Eduardo V. Ludeña Roberto López Boada 《Theoretical chemistry accounts》2007,118(3):557-561
Bearing in mind the insight into the Hohenberg–Kohn theorem for Coulomb systems provided recently by Kryachko (Int J Quantum
Chem 103:818, 2005), we present a re-statement of this theorem through an elaboration on Lieb’s proof as well as an extension
of this theorem to finite subspaces.
Contribution to the Serafin Fraga Memorial Issue. 相似文献
52.
A. Alba M. A. Aramendia V. Borau C. Jimenez J. M. Marinas 《Reaction Kinetics and Catalysis Letters》1984,25(1-2):45-50
The reduction of ,-unsaturated (olefin) carbonyl compounds of the type using a 0.75 wt.% Pd catalyst supported on SiO2–AlPO4 (8020 w/w) in a Parr reactor at low hydrogen pressure is reported. Selectivity in the reduction of the C=C bond is 100% in every case, and the nature of the groups A and B affects reaction rate, thus suggesting a 1,4-hydrogen addition mechanism.
, - () , , 0,75 . % Pd, SiO2–AlPO4 (8020 /), . C=C 100% , A B , 1,4- .相似文献
53.
de Namor AF Chahine S Castellano EE Piro OE Jenkins HD 《Chemical communications (Cambridge, England)》2005,(30):3844-3846
An additive thermodynamic contribution of pendant arms to the complexation of calixarene derivatives with mercury(II) in acetonitrile is for the first time demonstrated. 相似文献
54.
The reaction of several α-amino acids and peptides (containing Gly, L-Ala, L-Leu, L- or DL-Phe, and/or L- or D-Val) with air-diluted nitrogen oxides has been studied to roughly mimic the N-nitrosation of peptide bonds that the contaminated urban air might produce in pulmonary tissues. Most N-protected α-amino acids give practically quantitative yields of N-nitroso derivatives. N-Protected dipeptides afford either dinitrosated peptides, mixtures of di- and mononitrosated compounds, selectively mononitrosated products, or no reaction at all, depending mainly on steric effects. The same trends are observed for some higher peptides. The (po1y)nitrosated Peptides, which retain the chirality of the starting materials, have been characterized by 1H and 13C NMR spectroscopy and are cleaved by pyrrolidine and amino esters under mild conditions to give (new) amides or peptides plus diazo derivatives. 相似文献
55.
J. Miguel Vadillo M. Esther Gonzalez Isabel Carretero J. Javier Laserna 《Mikrochimica acta》1995,118(3-4):273-282
Micellar liquid chromatography (MLC) and capillary zone electrophoresis (CZE) have been evaluated for the analysis of twelve banned drugs in sport including diuretics and -blockers. In MLC, a sodium dodecylsulphate aqueous solution has been used as mobile phase using an octadecylsilica column. In CZE, a pH 8 buffer solution and a silica capillary have been employed. Parameters of retention and efficiency have been compared. Limits of detection with UV detection at 254 nm and relative standard deviations for atenolol, furosemide, nadolol, spironolactone and triamterene were established and compared in both techniques. Examples of direct urine injection into the separation systems are presented. Drugs overlapping in MLC are well resolved in CZE, while the opposite is true for a limited number of drugs. Some interferences from urine may arise in CZE. The selectivity of analysis would be greatly enhanced by using both techniques, which require only filtration as pre-treatment. 相似文献
56.
Abe K Abt I Ash WW Aston D Bacchetta N Baird KG Baltay C Band HR Barakat MB Baranko G Bardon O Barklow T Bazarko AO Ben-David R Benvenuti AC Bienz T Bilei GM Bisello D Blaylock G Bogart JR Bolton T Bower GR Brau JE Breidenbach M Bugg WM Burke D Burnett TH Burrows PN Busza W Calcaterra A Caldwell DO Calloway D Camanzi B Carpinelli M Cassell R Castaldi R Castro A Cavalli-Sforza M Church E Cohn HO Coller JA Cook V Cotton R Cowan RF Coyne DG D'Oliveira A Damerell CJ Dasu S De Sangro R De Simone P 《Physical review D: Particles and fields》1994,50(9):5580-5590
57.
Oludotun A. Phillips Eduardo L. Setti Andhe V. N. Reddy Ronald G. Micetich Chieko Kunugita Akio Hyodo Samarendra N. Maiti 《Chemistry of Heterocyclic Compounds》1998,34(11):1319-1323
Two monobactam derivatives, potassium 4-methyl-(3E)-[(thien-2-yl)methylene]-2-azetidinone-1-sulfonate and its (3Z)-isomer, were prepared and evaluated for their -lactamase inhibitory activities. These compounds were devoid of -lactamase inhibitory activity.SynPhar Laboratories Inc., #2, 4290-91A Street, Edmonton, Alberta T6E 5V2, Canada. Tokushima Research Institute, Taiho Pharmaceutical Co., Ltd., 224-2 Ebisuno Hiraishi, Kawauchi-cho, Tokushima 771-01, Japan. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1548–1552, November, 1998. 相似文献
58.
Beltrão EI Correia MT Figueredo-Silva J Coelho LC 《Applied biochemistry and biotechnology》1998,74(3):125-134
The phenomenon of altered carbohydrates in transformed cell surfaces has been studied through histochemical techniques using
lectins. Specific binding patterns to normal and transformed mammary tissues were evaluated by Isoform 1 fromCratylia mollis lectin (Cra Iso 1). Protocols using a direct method, incubation of Cra Iso I conjugated to peroxidase (Cra Iso 1-Per) with
mammary tissues, followed by diaminobenzidine and hydrogen peroxidase interaction, were performed. Neoplastic tissues, marked
by Cra Iso 1, showed a higher intensity of staining than normal ones, in comparison withCanavalia ensiformis lectin, Concanavalin A (Con A), conjugated to peroxidase (Con A-Per). The assay with Cra Iso 1 also indicated a possible
utilization of this lectin to characterize normal and transformed mammary cells. 相似文献
59.
Radul has recently introduced a map from the Lie algebra of differential operators on the circle of W
n
. In this Letter, we extend this map to W
KP
(q)
, a recently introduced one-parameter deformation of WKP - the second Hamiltonian structure of the KP hierarchy. We use this to give a short proof that W is the algebra of additional symmetries of the KP equation. 相似文献
60.
Given a measurable function f on (0, ) with Mellin transformF(s), let |f|p denote the Lp-norm of f with respect to the measuredx/x. We prove that under certain assumptions, for instanceif f is real and non-negative and F() converges for in an openinterval and F() 0, then
wherecp (2e)1. We derive similar inequalities for complex-valuedf, for the Lp-norm of the derivative of f, and for the supremumof real-valued f and of its derivative. The lower bounds areeminently applicable when f is a convolution product. 相似文献