全文获取类型
收费全文 | 426007篇 |
免费 | 3545篇 |
国内免费 | 1057篇 |
专业分类
化学 | 202683篇 |
晶体学 | 5738篇 |
力学 | 21467篇 |
综合类 | 7篇 |
数学 | 62070篇 |
物理学 | 138644篇 |
出版年
2021年 | 2621篇 |
2020年 | 2940篇 |
2019年 | 3291篇 |
2018年 | 11685篇 |
2017年 | 12398篇 |
2016年 | 9838篇 |
2015年 | 4615篇 |
2014年 | 6349篇 |
2013年 | 15724篇 |
2012年 | 15585篇 |
2011年 | 24812篇 |
2010年 | 16301篇 |
2009年 | 16247篇 |
2008年 | 22256篇 |
2007年 | 25230篇 |
2006年 | 12840篇 |
2005年 | 17042篇 |
2004年 | 13407篇 |
2003年 | 12297篇 |
2002年 | 10354篇 |
2001年 | 10622篇 |
2000年 | 8256篇 |
1999年 | 6230篇 |
1998年 | 5135篇 |
1997年 | 5044篇 |
1996年 | 4443篇 |
1995年 | 4369篇 |
1994年 | 4213篇 |
1993年 | 3981篇 |
1992年 | 4525篇 |
1991年 | 4453篇 |
1990年 | 4335篇 |
1989年 | 4102篇 |
1988年 | 4189篇 |
1987年 | 4210篇 |
1986年 | 3927篇 |
1985年 | 5194篇 |
1984年 | 5478篇 |
1983年 | 4634篇 |
1982年 | 4879篇 |
1981年 | 4675篇 |
1980年 | 4561篇 |
1979年 | 4798篇 |
1978年 | 4927篇 |
1977年 | 4829篇 |
1976年 | 4964篇 |
1975年 | 4694篇 |
1974年 | 4637篇 |
1973年 | 4922篇 |
1972年 | 3162篇 |
排序方式: 共有10000条查询结果,搜索用时 375 毫秒
121.
122.
123.
124.
Francesco Segatta David M. Rogers Naomi T. Dyer Ellen E. Guest Zhuo Li Hainam Do Artur Nenov Marco Garavelli Jonathan D. Hirst 《Molecules (Basel, Switzerland)》2021,26(2)
A fully quantitative theory of the relationship between protein conformation and optical spectroscopy would facilitate deeper insights into biophysical and simulation studies of protein dynamics and folding. In contrast to intense bands in the far-ultraviolet, near-UV bands are much weaker and have been challenging to compute theoretically. We report some advances in the accuracy of calculations in the near-UV, which were realised through the consideration of the vibrational structure of the electronic transitions of aromatic side chains. 相似文献
125.
Dorovskikh S. I. Stabnikov P. А. Zelenina L. N. Sysoev S. V. Morozova N. B. 《Russian Journal of General Chemistry》2021,91(10):1977-1983
Russian Journal of General Chemistry - Thermogravimetry, differential scanning calorimetry, and flow methods were used to investigate thermal properties of a series of cobalt(II)... 相似文献
126.
Corina Andronescu Justus Masa Richard D. Tilley John J. Gooding Wolfgang Schuhmann 《Current Opinion in Electrochemistry》2021
The complex interplay of restricted mass transport leading to local accumulation or depletion of educts, intermediates, products, counterions and co-ions influences the reactions at the active sites of electrocatalysts when electrodes are rough, three-dimensionally mesoporous or nanoporous. This influence is important with regard to activity, and even more to selectivity, of electrocatalytic reactions. The underlying principles are discussed based on the growing awareness of these considerations over recent years. 相似文献
127.
João Marcos G. Barbosa Milenna K. Fernandes Rodrigues Lurian C. David Taynara C. e Silva Danielly A. Fortuna Lima Naiara Z. Pereira Emmanuel B. D'Alessandro Anselmo E. de Oliveira Paulo H. Jorge da Cunha Maria Clorinda S. Fioravanti Nelson R. Antoniosi Filho 《Biomedical chromatography : BMC》2020,34(11):e4935
An innovative volatolomic approach employs the detection of biomarkers present in cerumen (earwax) to identify cattle intoxication by Stryphnodendron rotundifolium Mart., Fabaceae (popularly known as barbatimão). S. rotundifolium is a poisonous plant with the toxic compound undefined and widely distributed throughout the Brazilian territory. Cerumen samples from cattle of two local Brazilian breeds (‘Curraleiro Pé-Duro’ and ‘Pantaneiro’) were collected during an experimental intoxication protocol and analyzed using headspace (HS)/GC–MS followed by multivariate analysis (genetic algorithm for a partial least squares, cluster analysis, and classification and regression trees). A total of 106 volatile organic metabolites were identified in the cerumen samples of bovines. The intoxication by S. rotundifolium influenced the cerumen volatolomic profile of the bovines throughout the intoxication protocol. In this way, it was possible to detect biomarkers for cattle intoxication. Among the biomarkers, 2-octyldecanol and 9-tetradecen-1-ol were able to discriminate all samples between intoxicated and nonintoxicated bovines. The cattle intoxication diagnosis by S. rotundifolium was accomplished by applying the cerumen analysis using HS/GC–MS, in an easy, accurate, and noninvasive way. Thus, the proposed bioanalytical chromatography protocol is a useful tool in veterinary applications to determine this kind of intoxication. 相似文献
128.
Valentin A. Semenov Dmitry O. Samultsev Leonid B. Krivdin 《Magnetic resonance in chemistry : MRC》2020,58(6):532-539
The density functional theory calculation of 1H and 13C NMR chemical shifts in a series of ten 10 classically known Strychnos alkaloids with a strychnine skeleton was performed at the PBE0/pcSseg-2//pcseg-2 level. It was found that calculated 1H and 13C NMR chemical shifts provided a markedly good correlation with experiment characterized by a mean absolute error of 0.08 ppm in the range of 7 ppm for protons and 1.67 ppm in the range of 150 ppm for carbons, so that a mean absolute percentage error was as small as ~1% in both cases. 相似文献
129.
Two new divalent copper (C1) and zinc (C2) chelates having the formulae [M(PIMC)2] (where M = Cu(II), Zn(II) and PIMC = Ligand [(E)-3-(((3-hydroxypyridin-2-yl)imino)methyl)-4H-chromen-4-one] were obtained and characterized by several techniques. Structures and geometries of the synthesized complexes were judged based on the results of alternative analytical and spectral tools supporting the proposed formulae. IR spectral data confirmed the coordination of the ligands to the copper and zinc centers as monobasic tridentate in the enol form. Thermal analysis, UV-Vis spectra and magnetic moment confirmed the geometry around the copper center to be tetrahedral, square pyramidal and octahedral. Study of the binding ability of the synthesized compounds with Circulating tumor DNA (CT-DNA) bas been evaluated applying UV-Vis spectral titration and viscosity measurements. The copper and zinc oxides were achieved from the copper and zinc nano-particles structures Schiff base complexes as the raw material after calcination for 5 hr at 600°C. On the other hand, synthesized of C1 and C2 NPs were used as suitable precursors to the preparation of CuO and ZnO NPs. Finally, the synthesized of the two complexes exhibited enhanced activity against the tested bacterial (Staphylococcus aureus and Escherichia Coli) and fungal strains (Candida albicans and Aspergillus fumigatus) as compared to HPIMC. Among all these synthesized compounds, C1 exhibits good cleaving ability compared to other newly synthesized C2. 相似文献
130.