全文获取类型
收费全文 | 93篇 |
免费 | 5篇 |
国内免费 | 8篇 |
专业分类
化学 | 62篇 |
综合类 | 12篇 |
数学 | 2篇 |
物理学 | 30篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 4篇 |
2019年 | 1篇 |
2018年 | 4篇 |
2016年 | 3篇 |
2015年 | 4篇 |
2014年 | 7篇 |
2013年 | 3篇 |
2012年 | 9篇 |
2011年 | 1篇 |
2010年 | 7篇 |
2009年 | 5篇 |
2008年 | 4篇 |
2007年 | 5篇 |
2006年 | 5篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2002年 | 3篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1995年 | 6篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1974年 | 1篇 |
排序方式: 共有106条查询结果,搜索用时 156 毫秒
1.
2.
In the present work, we study the use of near infra-red spectroscopy (NIRS) technology together with a remote reflectance fibre-optic probe for determination of the major components in bee pollen. The method allows immediate control of the bee pollen without prior sample treatment or destruction through direct application of the fibre-optic probe to the sample.The regression method employed was modified partial least squares (MPLS). The calibration results obtained using 45 samples of bee pollen allowed the measurement of protein, moisture, ash, reducing sugars, and pH with multiple correlation coefficients (RSQ) and prediction corrected standard errors (SEPC) of 0.91, 0.56% for protein, of 0.78 and 0.49% for moisture; 0.92 and 0.049% for ash; 0.81 and 1.32 g of glucose/100 g of bee pollen; 0.84 and 0.15 for pH, respectively.The prediction capacity of the pattern was checked by applying it to samples of unknown pollen in external validation. 相似文献
3.
One hundred and forty-seven species of spores and pollen referred to 77 genera found in the crudeoil samples taken from four petroliferous provinces of the Tarim Basin of Xinjiang Provincehave been studied in this paper. By means of these spore and pollen fossils, the geological ages anddistribution of the petroleum source rocks of the basin are judged. Also, the principles and methodsto judge the petroleum source of a petroleum province by spore/pollen and other microfossils in crudeoils are explained. 相似文献
4.
Ascorbic acid (AA) is one of the essential nutrients in bee pollen, however, it is unstable and likely to be oxidized. Generally, the oxidation form (dehydroascorbic acid (DHA)) is considered to have equivalent biological activity as the reduction form. Thus, determination of the total content of AA and DHA would be more accurate for the nutritional analysis of bee pollen. Here we present a simple, sensitive, and reliable method for the determination of AA, total ascorbic acids (TAA), and DHA in rape (Brassica campestris), lotus (Nelumbo nucifera), and camellia (Camellia japonica) bee pollen, which is based on ultrasonic extraction in metaphosphoric acid solution, and analysis using hydrophilic interaction liquid chromatography (HILIC)-ultraviolet detection. Analytical performance of the method was evaluated and validated, then the proposed method was successfully applied in twenty-one bee pollen samples. Results indicated that contents of AA were in the range of 17.54 to 94.01 µg/g, 66.01 to 111.66 µg/g, and 90.04 to 313.02 µg/g for rape, lotus, and camellia bee pollen, respectively. In addition, percentages of DHA in TAA showed good intra-species consistency, with values of 13.7%, 16.5%, and 7.6% in rape, lotus, and camellia bee pollen, respectively. This is the first report on the discriminative determination between AA and DHA in bee pollen matrices. The proposed method would be valuable for the nutritional analysis of bee pollen. 相似文献
5.
珍汕97不育系和保持系水稻花粉发育过程中RNA含量变化的研究 总被引:1,自引:0,他引:1
采用组织化学方法,对珍汕97水稻不育系及保持系的花粉发育过程进行分析,结果表明从幼小的单孢花粉到单核边位出现中央大液泡时期,不育系花粉细胞RNA含量与保持系无显著差异,单核末期不育系开始败育,双核期RNA含量与保持系双核期花粉细胞相比有显著下降,说明RNA含量下降是珍汕97不育系花粉败育的一个重要生理特征,不育系花粉在单核末期以前发育是正常的. 相似文献
6.
Genetic Bee Colony (GBC) algorithm: A new gene selection method for microarray cancer classification
Naturally inspired evolutionary algorithms prove effectiveness when used for solving feature selection and classification problems. Artificial Bee Colony (ABC) is a relatively new swarm intelligence method. In this paper, we propose a new hybrid gene selection method, namely Genetic Bee Colony (GBC) algorithm. The proposed algorithm combines the used of a Genetic Algorithm (GA) along with Artificial Bee Colony (ABC) algorithm. The goal is to integrate the advantages of both algorithms. The proposed algorithm is applied to a microarray gene expression profile in order to select the most predictive and informative genes for cancer classification. In order to test the accuracy performance of the proposed algorithm, extensive experiments were conducted. Three binary microarray datasets are use, which include: colon, leukemia, and lung. In addition, another three multi-class microarray datasets are used, which are: SRBCT, lymphoma, and leukemia. Results of the GBC algorithm are compared with our recently proposed technique: mRMR when combined with the Artificial Bee Colony algorithm (mRMR-ABC). We also compared the combination of mRMR with GA (mRMR-GA) and Particle Swarm Optimization (mRMR-PSO) algorithms. In addition, we compared the GBC algorithm with other related algorithms that have been recently published in the literature, using all benchmark datasets. The GBC algorithm shows superior performance as it achieved the highest classification accuracy along with the lowest average number of selected genes. This proves that the GBC algorithm is a promising approach for solving the gene selection problem in both binary and multi-class cancer classification. 相似文献
7.
Victoria V. Roshchina 《Journal of fluorescence》2002,12(2):241-243
Rutacridone, alkaloid from plant Ruta graveolens was used for the histochemical staining of Hippeastrum hybridum pollen. The rutacridone fluorescence (excited by UV light at 360–380 nm) has been studied with Karnaukhov-constructed microspectrofluorimeters. Nucleus and DNA were stained by this dye in cells and fluoresced by green light with maxima of 530 and 555 nm, respectively. Development of the pollen was analyzed with this dye. 相似文献
8.
烟草脱外壁花粉的制备夏惠君,周嫦,杨弘远(武汉大学生命科学学院,武汉,430072)关键词脱外壁花粉,制备,烟草中图法分类号Q944.42花粉粒由外壁、内壁与原生质体3部分组成.有关花粉生物学的研究已有报道[‘·‘j.近年来,花粉原生质体的研究也取得... 相似文献
9.
利用膜不通透的荧光染料钙黄素作为指示剂,比较了烟草脱外壁花粉与完整的未萌发花粉和萌发花粉电激导入的效果.研究了电激过程中的电场强度、脉冲持续时间、电激液的介质成分和浓度对三者的导入率及电激后花粉萌发率的影响.结果表明,从未萌发花粉、萌发花粉到脱外壁花粉,导入率逐渐升高,证实了脱外壁花粉由于摆脱了外壁的阻碍而有利于外源物质的电激导入.但电激后花粉萌发率的变化规律相反.荧光指示剂的应用便于优化选择适宜电激参数,为外源基因的导入实验提供了参考依据. 相似文献
10.
You J Liu L Zhao W Zhao X Suo Y Wang H Li Y 《Analytical and bioanalytical chemistry》2007,387(8):2705-2718
A simple and sensitive method for evaluating the chemical compositions of protein amino acids, including cystine (Cys)2 and tryptophane (Try) has been developed, based on the use of a sensitive labeling reagent 2-(11H-benzo[α]-carbazol-11-yl) ethyl chloroformate (BCEC–Cl) along with fluorescence detection. The chromophore of the 1,2-benzo-3,4-dihydrocarbazole-ethyl
chloroformate (BCEOC-Cl) molecule was replaced with the 2-(11H-benzo[α]-carbazol-11-yl) ethyl functional group, yielding the sensitive fluorescence molecule BCEC–Cl. The new reagent BCEC–Cl
could then be substituted for labeling reagents commonly used in amino acid derivatization. The BCEC–amino acid derivatives
exhibited very high detection sensitivities, particularly in the cases of (Cys)2 and Try, which cannot be determined using traditional labeling reagents such as 9-fluorenyl methylchloroformate (FMOC-Cl)
and ortho-phthaldialdehyde (OPA). The fluorescence detection intensities for the BCEC derivatives were compared to those obtained when
using FMOC-Cl and BCEOC-Cl as labeling reagents. The ratios I
BCEC/I
BCEOC = 1.17–3.57, I
BCEC/I
FMOC = 1.13–8.21, and UVBCEC/UVBCEOC = 1.67–4.90 (where I is the fluorescence intensity and UV is the ultraviolet absorbance). Derivative separation was optimized on a Hypersil BDS
C18 column. The detection limits calculated from 1.0 pmol injections, at a signal-to-noise ratio of 3, ranged from 7.2 fmol for
Try to 8.4 fmol for (Cys)2. Excellent linear responses were observed, with coefficients of >0.9994. When coupled with high-performance liquid chromatography,
the method established here allowed the development of a highly sensitive and specific method for the quantitative analysis
of trace levels of amino acids including (Cys)2 and Try from bee-collected pollen (bee pollen) samples. 相似文献