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排序方式: 共有756条查询结果,搜索用时 15 毫秒
741.
Sung Eun Kim Yong Woo Cho Eun Jung Kang Ick Chan Kwon Eunhee Bae Lee Jung Hyun Kim Hesson Chung Seo Young Jeong 《Fibers and Polymers》2001,2(2):64-70
A three-dimensional, porous collagen/chitosan complex sponge was prepared to closely simulate basic extracellular matrix (ECM)
constitutes, collagen and glycosaminoglycan. The complex sponge was prepared by a lyophilization method and had the regular
network with highly porous structure, suitable for cell adhesion and growth. The pores were well interconnected, and their
distribution was fairly homogeneous. The complex sponge was crosslinked using 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide
(EDC) and N-hydroxysuccinimide (NHS) to increase its biological stability and enhance its mechanical properties. The crosslinking
medium had a great effect on the inner structure of the sponge. The homogeneous, porous structure of the sponge was remarkably
collapsed in an aqueous crosslinking medium. However, the morphology of the sponge remained almost intact in a water/ethanol
mixture crosslinking milieu. Mechanical properties of the collagen/chitosan sponge were significantly enhanced by EDC-mediated
crosslinking. The potential of the sponge as a scaffold for tissue engineering was investigated using a Chinese hamster ovary
cell (CHO-K1) line. 相似文献
742.
To better understand the formation of necking in drawing processes of fibers, strain distributions during drawing processes
have been analyzed. For simplicity, one-dimensional incompressible steady flow at a constant temperature was assumed and quasi-static
model was used. To describe mechanical properties of solid polymers, non-linear visco-plastic material properties were assumed
using the power law type hardening and rate-sensitive equation. The effects of various parameters on the neck formation were
mathematically analyzed. As material property parameters, strain-hardening parameter, visco-elastic coefficient and strain-rate
sensitivity were considered and, for process parameters, the drawing ratio and the process length were considered. It was
found that rate-insensitive materials do not reach a steady flow state and the rate-sensitivity plays a key role to have a
steady flow. Also, the neck formation is mainly affected by material properties, especially for the quasi-static model. If
the process length changes, the strain distribution was found to be proportionally re-distributed along the process line by
the factor of the total length change. 相似文献
743.
Wet spun silk fibroin (SF) filaments have attracted considerable attention because of their potential in biotechnological applications including surgical sutures, tissue engineering and wound dressing. Although the molecular weight (MW) of polymers is one of key factors affecting the wet spinnability of dope along with the structural characteristics and properties of wet spun filament, no related study has been conducted. In this study, regenerated SFs with different MWs and concentrations were prepared by wet spinning. The effects of the SF concentration and MW on 1) wet spinnability and rheology of silk dope solution and 2) crystallinity index and post drawing performance of wet spun silk filament were examined. Their relationships were also investigated. The rheological measurements showed that an 80 mPa·s viscosity is needed to obtain a continuous wet spun SF filament. As the MW of SF increased, the peak position of the maximum draw ratio shifted to a lower SF concentration with a concomitant increase in the maximum draw ratio value at the peak. Interestingly, the crystallinity index obtained from Fourier transform infrared spectroscopy (FTIR) revealed a similar trend to the maximum draw ratio suggesting that the post drawing ability is strongly affected by the quantity of short-ordered crystalline regions in wet spun SF filaments. On the other hand, X-ray diffraction did not detect any crystallinity change in the SF filament produced from the formic acid solvent system. It was concluded that MW strongly affected the dope solution viscosity and the crystallinity index from FTIR and these determined the fiber formation of dope and post drawing performance of fiber. 相似文献
744.
This study investigated the incorporation of nanoscale germanium (Ge) and silicon dioxide (SiO2) particles into poly(vinyl alcohol) (PVA) nanofibers with the aim of developing nanostructures with far-infrared radiation effects and antimicrobial properties for biomedical applications. Composite fibers containing Ge and SiO2 were fabricated at various concentrations of Ge and/or SiO2 using electrospinning and layered on polypropylene nonwoven. The morphological properties of the nanocomposite fibers were characterized using a field-emission scanning electron microscope and a transmission electron microscope. The far-infrared emissivity and emissive power of the nanocomposite fibers were examined in the wavelength range of 5-20 μm at 37 °C. The antibacterial properties were quantitatively assessed by measuring the bacterial reductions of Staphylococcus aureus, Klebsiella pneumoniae, and Escherichia coli. Multi-component composite fibers electrospun from 11 wt% PVA solutions containing 0.5 wt% Ge and 1 wt% SiO2 nanoparticles exhibited a far-infrared emissivity of 0.891 and an emissive power of 3.44·102 W m?2 with a web area density of 5.55 g m?2. The same system exhibited a 99.9 % bacterial reduction against both Staphylococcus aureus and Escherichia coli, and showed a 34.8 % reduction of Klebsiella pneumoniae. These results demonstrate that PVA nanofibrous membranes containing Ge and SiO2 have potential in medical and healthcare applications such as wound healing dressings, skin care masks, and medical textile products. 相似文献
745.
The effects of giant embryo brown rice Seonong 17 and Keunnunjami, in comparison with that of ordinary normal brown rice, on the body weight and lipid profile in mice under a high‐fat diet condition were investigated. The animals were fed with experimental diets for eight weeks: normal control, high fat (HF), and high fat supplemented with normal brown rice, Seonong 17 rice, or Keunnunjami rice powder. Their body and fat weights, lipid profiles, lipogenic enzyme activities, and adipokine concentrations were determined. Significant differences between the animal groups were analyzed with Tukey's test (P < 0.05). A marked increase in the body weight and fat, plasma triglyceride and total cholesterol concentrations, and free fatty acid level were found in HF mice relative to the control group. On the other hand, diet supplementation with rice, particularly the giant embryo rice samples, significantly suppressed this high‐fat‐induced body weight gain and hyperlipidemia via regulation of lipogenesis and adipokine production. Both the Seonong 17 and Keunnunjami exhibited greater hypolipidemic and body fat–lowering effects than the normal brown rice. The results demonstrate that these giant embryo mutants may be beneficial as biomaterials for functional foods with antiobesity and hypolipidemic effects. 相似文献
746.
Yong-Jin Park Anupam Dixit Kyung-Ho Ma Ju-Kyung Lee Myoung-Hee Lee Chan-Sik Chung Miyuki Nitta Kazutoshi Okuno Tae-San Kim Eun-Gi Cho V. Ramanatha Rao 《Genetic Resources and Crop Evolution》2008,55(4):523-535
The present study demonstrates utilization of 11 microsatellite markers to explore genetic diversity held in Perilla frutescens (L.) Britt. landrace accessions growing on farms in different parts of Korea and Japan and to assess their genetic relationships.
All microsatellite loci were polymorphic and produced a total of 96 alleles ranging from 4 to 20, with an average of 8.7 alleles
per locus. Of the 96 alleles found, a total of 15 unique landrace-specific alleles were observed at 9 different loci. The
locus GBPFM203 provided the highest number of alleles (20), of which five were unique and each specific to a particular landrace
accession. The occurrence of unique, accession-specific alleles presented molecular evidence for the generation of new alleles
within on-farm collection of Perilla. The mean values of observed (H
O) and expected heterozygosity (H
E) were 0.39 and 0.68, respectively, indicating a considerable amount of polymorphism within this collection. A genetic distance-based
phylogeny grouped the two Perilla varieties, var. frutescens and var. crispa (Thunb.) Decne into two distinct groups. Accessions belonging to var. frutescens could also be divided into two subgroups at a close genetic distance (GD = 0.432). The overall clustering pattern did not
strictly follow the grouping of accessions according to their geographic origins. These observations are indicative of extensive
germplasm exchange among farms from different geographical regions. The genetic similarity observed among the Perilla landraces may be useful for future Perilla crop variety identification, conservation, and improvement programs. 相似文献
747.
Sang S Ju J Lambert JD Lin Y Hong J Bose M Wang S Bai N He K Reddy BS Ho CT Li F Yang CS 《Journal of agricultural and food chemistry》2006,54(26):9792-9797
This study was designed to investigate the cancer preventive activities of wheat bran (WB) oil. We studied the colon cancer preventive effects of WB oil and its subfractions in the Apc(min/+) mouse model, a recognized mouse model for human colorectal cancer, and used human colon cancer cell lines (HCT-116 and HT-29) to identify possible active fractions in WB oil. Our results showed that the oil fraction of WB was more active than the water fraction against the growth of human colon cancer cell lines and that 2% WB oil significantly inhibited the overall tumorigenesis by 35.7% (p < 0.0001) in the Apc(min/+) mouse model. The WB oil was further fractioned into nonpolar lipids and phytochemicals and the phytochemical fraction was fractionated into phytosterols and phytosterol ferulates, 5-alk(en)ylresorcinols, and unidentified constituents by normal phase silica gel column chromatography. Results on cell culture showed that the phytochemical fraction had a higher inhibitory effect on HCT-116 human colon cancer cells than that of WB oil, whereas the nonpolar lipid fraction had less growth inhibitory effectiveness. However, neither fractions showed a stronger inhibition than WB oil in the Apc(min/+) mouse model. The current results demonstrate, for the first time, the intestinal cancer preventive activity of WB oil. The active ingredients, however, remain to be identified. 相似文献
748.
749.
Yong-Chan Chung Sang Hyeon Kim Jin Cheol Bae Byoung Chul Chun 《Fibers and Polymers》2018,19(6):1157-1165
The bulky and rigid triphenylmethyl group was grafted onto polyurethane (PU) to reduce the molecular attractions between hard segments and to improve the mobility of the PU chain under freezing conditions. The triphenylmethyl-grafted PU exhibited improvement in the cross-link density, solution viscosity, maximum tensile stress, shape recovery at 10 °C, and low temperature flexibility compared with the plain PU. The soft segment melting was not affected by the grafted triphenylmethyl group, whereas the soft segment crystallization disappeared with the increase of the triphenylmethyl group content. The glass transition temperature (Tg) increased with the increase of the triphenylmethyl group content. The rapid increase of the tensile strength and shape recovery at 10 °C resulted from the cross-linking effect, whereas the strain at break and shape retention at -25 °C slightly decreased with the increase of the triphenylmethyl group content. The triphenylmethylgrafted PU displayed an excellent low temperature flexibility even at -50 °C due to the improved mobility of the PU chain compared to ordinary PU. 相似文献
750.
Revealing the compositions of the intestinal microbiota of three Anguillid eel species using 16S rDNA sequencing
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Hsiang‐Yi Hsu Fang‐Chi Chang Yu‐Bin Wang Shu‐Hwa Chen Ya‐Po Lin Chung‐Yen Lin Yu‐San Han 《Aquaculture Research》2018,49(7):2404-2415
Anguilla japonica, A. marmorata and A. bicolor pacifica are important eel species for aquaculture in Taiwan. In the past, seldom studies focused on the intestinal microbiome of them or the probiotics used in their cultivation. Probiotics are microbes that can improve the health of organisms, and the microbes isolated from the intestines of organisms might be the potential probiotics. Therefore, the aim of this study was to collect the intestinal mucus samples of these three eel species for investigating the autochthonous microbiome using 16S rDNA sequencing. The diversity, abundance of the intestinal microbiome and compositions of all the libraries were identified. Moreover, the composition of intestinal microbiome of eel was suggested that it would be affected by the waters and the characteristics of different eel species. Furthermore, most of the identified predominant genera of the intestinal microbiome of these three eel species, such as Cetobacterium, Clostridium, Shewanella, Acinetobacter and Bacteroides, seemed to have great potential as the probiotics. In the future, more studies shall be conducted to promote the practical application of these candidate probiotics for improving the techniques of eel farming. 相似文献