全文获取类型
收费全文 | 2257篇 |
免费 | 17篇 |
国内免费 | 8篇 |
专业分类
化学 | 1935篇 |
晶体学 | 5篇 |
力学 | 13篇 |
数学 | 70篇 |
物理学 | 259篇 |
出版年
2023年 | 5篇 |
2022年 | 3篇 |
2021年 | 8篇 |
2020年 | 15篇 |
2019年 | 7篇 |
2018年 | 15篇 |
2017年 | 9篇 |
2016年 | 25篇 |
2015年 | 13篇 |
2014年 | 23篇 |
2013年 | 53篇 |
2012年 | 146篇 |
2011年 | 286篇 |
2010年 | 88篇 |
2009年 | 40篇 |
2008年 | 202篇 |
2007年 | 215篇 |
2006年 | 207篇 |
2005年 | 202篇 |
2004年 | 147篇 |
2003年 | 127篇 |
2002年 | 105篇 |
2001年 | 66篇 |
2000年 | 72篇 |
1999年 | 20篇 |
1998年 | 19篇 |
1997年 | 11篇 |
1996年 | 16篇 |
1995年 | 10篇 |
1994年 | 18篇 |
1993年 | 11篇 |
1992年 | 7篇 |
1991年 | 8篇 |
1990年 | 3篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1980年 | 3篇 |
1976年 | 3篇 |
1974年 | 4篇 |
1972年 | 2篇 |
1971年 | 3篇 |
1969年 | 3篇 |
1968年 | 2篇 |
1967年 | 5篇 |
1966年 | 5篇 |
排序方式: 共有2282条查询结果,搜索用时 15 毫秒
161.
Sonication of chitin-glucan, preparation of water-soluble fractions and characterization by HPLC 总被引:1,自引:0,他引:1
A water-insoluble chitin-glucan complex, isolated from the mycelium of Aspergillus niger, was swollen in various aqueous media and treated subsequently by high-energy sonication. The concentration of the resulting water-soluble polysaccharide fractions was dependent on the swelling medium, the amount of the chitin-glucan complex in the suspension, and on the time of sonication. The yields of water-soluble chitin-glucan were within the range 13.6 to 24.4% relative to the mass of the original chitin-glucan. The nitrogen content obtained for the samples of water-soluble chitin-glucan indicated a higher content of chitin (3.45% of nitrogen in high-molecular fraction) than in the original water-insoluble chitin-glucan sample (1.8%). The distribution of the molecular weights of the water-soluble fractions prepared was determined by high-performance liquid chromatography. 相似文献
162.
B. Saghai J. -C. David B. Juliá-Dıaz T. -S. H. Lee 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):512-514
Differential cross-section and single polarization observables in the process γp→K
+
Λ are investigated within a constituent-quark model and a dynamical coupled-channel formalism. The effects of two new nucleon
resonances and of the K
*(892)- and K1(1270)-exchanges are briefly presented. 相似文献
163.
F. J. Baltá Calleja D. R. Rueda T. Secall R. K. Bayer M. Schlimmer 《Journal of Macromolecular Science: Physics》2013,52(4):461-469
Native potato starch was prepared using different processing methods. The samples were characterized by wide-angle X-ray scattering (WAXS), optical microscopy, differential scanning calorimetry (DSC), and microhardness. Compression molding of the starch granules led to sintered relatively brittle materials. Here, the amylopectin crystals of the native powder remained grossly preserved. Preparation of dry films from aqueous gels resulted in disintegration of the structure of the native starch granules and in the formation of a new semicrystalline structure comprised of crystallized amylose molecules. Injection molding of native starch was found to be a processing method that gives rise to amorphous materials with superior mechanical properties. 相似文献
164.
The inhibition of the oxygen evolution rate (OER) in Chlorella vulgaris by 2-alkylsulphanyl-4-pyridinecarbothioamides (APCTs; alkyl = methyl up to hexadecyl) was studied. APCTs were found to inhibit
photosynthetic electron transport (PET) which resulted in the inhibition of OER in algae. The inhibitory activity of APCTs
was highly dependent on the alkyl chain length of the 2-alkylsulphanyl substituent and the corresponding dependence showed
a bilinear course with the decyl derivative as being the most active inhibitor. Using EPR spectroscopy, the site of APCT action
in the algal photosynthetic apparatus was determined. It was confirmed that APCT interacted mainly with the D. intermediate,
i.e. with tyrosine radical (TyrD) occurring at the 161st position in D2 protein which is situated on the donor side of photosystem 2. 相似文献
165.
Mariá Ernestina Chávez Rodríguez Angel López Gómez 《International Journal of Theoretical Physics》2001,40(1):95-104
The only pair of binary classical essential connectives for which the Artin braid relation holds is a distributive lattice, i.e. the Boolean disjunction and conjunction of 相似文献
166.
B. Juliá-Díaz 《Few-Body Systems》2008,43(1-4):103-108
Recent developments on a dynamical coupled-channels model of hadronic and electromagnetic production of nucleon resonances are summarized. 相似文献
167.
States on sharply dominating effect algebras 总被引:1,自引:0,他引:1
Zdenka RIEANOV~ WU JunDe~ 《中国科学A辑(英文版)》2008,51(5):907-914
We prove that sharply dominating Archimedean atomic lattice effect algebras can be characterized by the property called basic decomposition of elements.As an application we prove the state smearing theorem for these effect algebras. 相似文献
168.
Manuela Martín‐Zarco Santiago Toribio Joaquín C. García‐Martínez Julián Rodríguez‐López 《Journal of polymer science. Part A, Polymer chemistry》2009,47(23):6409-6419
A series of polyamido amine (PAMAM) dendrimers (Generations 2, 3, 4, and 6) fully functionalized at their periphery with first‐ and second‐generation poly (phenylenevinylene) (PPV) dendrons have been efficiently prepared. MALDI‐TOF mass spectrometry proved to be particularly useful for the characterization of the new hybrid dendrimers as well as for the estimation of the average number of PPV dendrons attached to the surface. The optical absorption and emission properties of these systems were studied. The materials display extremely high molar extinction coefficients and emit blue light with only slightly lower fluorescence quantum yields than the corresponding free dendrons. Self‐quenching interactions between PPV units were not observed in THF. However, the luminescence properties underwent a dramatic change when toluene was used as the solvent. The lower polarity of toluene caused shrinkage of the PAMAM structure and brought the PPV chromophores closer together, leading to self‐quenching interactions and excimer formation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6409–6419, 2009 相似文献
169.
170.
This study investigated the organic and inorganic constituents of healthy leaves and Candidatus Liberibacter asiaticus (CLas)-inoculated leaves of citrus plants. The bacteria CLas are one of the causal agents of citrus greening (or Huanglongbing) and its effect on citrus leaves was investigated using laser-induced breakdown spectroscopy (LIBS) combined with chemometrics. The information obtained from the LIBS spectra profiles with chemometrics analysis was promising for the construction of predictive models to identify healthy and infected plants. The major, macro- and microconstituents were relevant for differentiation of the sample conditions. The models were then applied to different inoculation times (from 1 to 8 months). The models were effective in the classification of 82-97% of the diseased samples with a 95% significance level. The novelty of this method was in the fingerprinting of healthy and diseased plants based on their organic and inorganic contents. 相似文献