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Extracellular enzymatic activities in soils are essential for the cycling of organic matter. These activities take place in multiphase environments where solid phases profoundly affect biocatalytic activities. Aspergillus niger is ubiquitous in soils; its β-glucosidase plays an important role in the degradation of cellulose, and therefore in the global carbon cycle and in the turnover of soil organic matter. However, the information on the interactions of this protein with soil minerals is very limited, and even less is known about their consequences for the hydrolysis of the natural substrate cellobiose. We therefore characterised the sorptive interactions of this enzyme with the soil minerals montmorillonite, kaolinite and goethite and quantified the resulting changes in the hydrolysis rate of cellobiose. Fractions of adsorbed protein, and the resulting catalytic activity loss, were lower for montmorillonite than for kaolinite and goethite at given experimental conditions; adsorption was 9.7 ± 7.3% for montmorillonite, 70.3 ± 3.1% for kaolinite and 71.4 ± 1.8% for goethite, respectively. Adsorption of the protein to the minerals caused a total decrease in the catalytic activity of 18.8 ± 3.4% for kaolinite and 17.9 ± 4.7% for goethite whereas it was not significant for montmorillonite. The average catalytic activity lost by the pool of adsorbed molecules was 26.8% for kaolinite and 25.0% for goethite. Both the amount of adsorbed protein and the resulting loss of catalytic activity were found to be independent of the specific surface areas yet were influenced by the electrical properties of the mineral surfaces. Under the experimental conditions, montmorillonite and kaolinite are negatively charged whereas goethite is positively charged. However, because of the adsorption of phosphate anions from the buffer, a charge reversal took place at the surface of goethite. This was confirmed by zeta (ζ)-potential measurements in phosphate buffer, revealing negative values for all the tested minerals. Indeed goethite interacted with the enzyme as a negatively charged surface: the amount of adsorbed protein and the resulting catalytic activity loss were very similar to those of kaolinite. Our results show that, even if an important fraction of β-glucosidase is adsorbed to the minerals, the catalytic activity is largely retained. We suggest that this strong activity retention in presence of soil minerals results from a selective pressure on A. niger, which benefits from the activity of the adsorbed, and thus stabilized, enzyme pool. 相似文献
16.
Hybrid necrosis in Triticum is known to be caused by the interaction of two complementary dominant genes. In the present paper, the genotypes for hybrid necrosis of 64 winter wheat cultivars are presented. 41 cultivars were found to possess the Ne2 necrosis gene, whereas 23 cultivars were non-carriers. The Ne1 gene was not found in any of the cultivars analyzed. 相似文献
17.
Veli-Matti Rokka Yong-Sheng Xu Jyri Kankila Anja Kuusela Seppo Pulli Eija Pehu 《Euphytica》1994,80(3):207-217
Summary Symmetric somatic hybrids were produced by electrofusion of protoplasts of two dihaploid tuber-bearing potato (Solanum tuberosum L.) lines and Solanum brevidens Phil., a diploid non-tuber-bearing wild potato species. A total of 985 plants was obtained. Verification of nuclear hybridity of putative hybrids was based on additive RAPD patterns, general morphological characteristics and chromosome counts. 53 (90%) calli regenerated into plants which were identified as somatic hybrids. Most of the hybrids were aneuploids at the tetraploid (4×) or hexaploid (6×) level. The 20 hybrids tested expressed a high level of resistance to potato virus Y (PVY
N
) characteristic of the S. brevidens parent. Resistance to late blight (Phytophthora infestans (Mont.) de Bary) varied between hybrids, but was on average better than that of the fusion parents. Resistance of hybrids to bacterial stem rot (Erwinia carotovora subsp. atroseptica (van Hall) Dye) was not superior to that of commercial potato cultivars. 相似文献
18.
Traugott J. Scheytt Petra Mersmann Elzbieta Rejman-Rasinski Anja These 《Journal of Soils and Sediments》2007,7(2):75-84
Background, Aim and Scope
One of the first occurrences of pharmaceutically active compounds in groundwater was reported from the sewage irrigation farms
south of Berlin. At these sewage irrigation farms treated sewage effluent passed the soil and unsaturated zone before reaching
the aquifer. Clofibric acid was detected in pore water from soils of those sewage irrigation farms in concentrations between
65 ng/L and 1430 ng/L. The aim of this study was to investigate the transport behavior of regularly detected clofibric acid,
diclofenac, ibuprofen, and propyphenazone under conditions comparable to those at the sewage irrigation farms in a multiple
compound sand column laboratory experiment.
Materials and Methods
Sediment column experiments were conducted to study the transport of pharmaceuticals in the unsaturated zone. The migration
was measured in fine to medium grained sand and leaching solution containing 1 mg/L of pharmaceutically active compounds and
61 mg/L of the tracer lithium chloride (LiCl). For the analysis of the pharmaceutical compounds the water samples were adjusted
to a pH value of 2 and then extracted by solid-phase extraction (SPE). Before extraction, the samples were spiked with a surrogate
standard for analytical quality control. The sample extracts were analyzed by capillary gas chromatography-mass spectrometry
(GC-MS) with selected ion monitoring (SIM). Depending on the sample volume (100 to 200 mL) and the matrix, the limits of detection
were between 1 and 10 ng/L, and the limits of quantitation were between 5 and 25 ng/L. Analysis for calcium, magnesium and
lithium were carried out using a 'Trace Scan' ICP-AES from Thermo Jarrel Ash. Sodium, potassium, iron and manganese were analyzed
using a Philips PU 9400 flame AAS. Analysis of anions was performed on a Dionex ion chromatograph DX 120.
Results
At the sewage irrigation farms the average concentrations of clofibric acid in the unsaturated zone declined from higher values
near ground surface (480 ng/L) to lower values near the groundwater table (65 ng/L). From the pharmaceuticals analyzed only
clofibric acid, primidone and propyphenazone could be analyzed in the first (upper) aquifer at the sewage irrigation farms.
All other pharmaceuticals could neither be detected in the first aquifer nor in the deeper aquifers. Breakthrough curves from
soil column experiments revealed no transformation and no retardation for clofibric acid, whereas transformation of diclofenac
was so high (79%) that no retardation factor could be calculated. Ibuprofen was significantly transformed (37%), transformation
of propyphenazone (17%) was quite low and retardation (Rf = 2.05) was in the range of previously conducted column experiments.
Discussion
The results confirm previously conducted experiments with clofibric acid where this compound was identified as highly mobile
and persistent. The results that diclofenac and ibuprofen are significantly transformed where unexpected as other studies
exhibited much lower transformation under saturated conditions at least for diclofenac. However, lower pH values and higher
oxygen contents in the unsaturated zone compared to the aquifer may explain this observed high transformation of these compounds
at the column experiments.
Conclusions
We conclude that irrigation with sewage effluent containing the compounds used in our experiments will lead to an input into
groundwater of clofibric acid, whereas diclofenac and ibuprofen will most likely be transformed during the passage. Propyphenazone
will be retarded but will most likely occur in groundwater. These results from the column experiments coincide very well with
the occurrence of the pharmaceuticals clofibric acid, primidone, and propyphenazone in the first aquifer.
Recommendations and Perspective :
The results underline the need to study the sorption of pharmaceuticals on various materials. e.g. organic matter, surfaces
at pH values occurring in the unsaturated zone. Future field studies will also include the investigation of desorption behavior
in the unsaturated zone. 相似文献
19.
A stable isotope dilution assay (SIDA) for the quantitation of N(2)-[1-(carboxy)ethyl]folic acid (CEF) has been developed by using [(2)H(4)]CEF as the internal standard. After sample cleanup by anion exchange chromatography, the three-dimensional specifity of liquid chromatography-tandem mass spectrometry enabled unequivocal determination of the nonenzymatic glycation product of folic acid (FA). When CEF was added to cornstarch, the detection limit for CEF was found to be 0.4 microg/100 g, and a recovery of 98.5% was determined. In analyses of cookies, the intra-assay coefficient of variation was 8.0% (n = 5). Application of the SIDA to commercial cookies produced from wheat flour fortified with FA revealed CEF contents of up to 7.1 microg/100 g, which accounted for approximately 10-20% of the cookies' FA content. In baby foods, multivitamin juices, and multivitamin sweets, however, CEF was not detectable. Further studies on CEF formation during baking of cookies made from fortified flour and different carbohydrates revealed that fructose was most effective in generating CEF followed by glucose, lactose, and sucrose with 12.5, 3.9, 2.5, and 2.5 microg/100 g of dry mass, respectively. During baking, approximately 50% of FA was retained for both monosaccharides fructose and glucose, and 77% as well as 85% of its initial content was retained for the disaccharides lactose and sucrose, respectively. Of the degraded amount of FA, CEF comprised 28% for fructose as well as 18, 12, and 8% for sucrose, lactose, and glucose, respectively. Therefore, CEF can be considered an important degradation product of FA in baked foods made from fructose. To retain a maximum amount of FA, products should rather be baked with sucrose than with reducing carbohydrates. 相似文献
20.
Volatile compounds of selected strawberry varieties analyzed by purge-and-trap headspace GC-MS 总被引:1,自引:0,他引:1
Hakala MA Lapveteläinen AT Kallio HP 《Journal of agricultural and food chemistry》2002,50(5):1133-1142
Six strawberry (Fragaria x ananassa Duch.) varieties, Senga Sengana, Jonsok, Polka, Korona, Bounty, and Honeoye, were studied in relation to composition of their volatile headspace compounds collected by dynamic purge-and-trap concentration. Also, the influence of cultivation technique on the volatile compounds was tested by comparing conventionally and organically cultivated strawberry varieties. In addition, the effect of geographical origin on strawberry volatiles was investigated. The emphasis of this study was lay in the industrial utilization of strawberry. A total of 52 different volatile compounds were determined from frozen strawberries grown in 1997 and 1998. In addition to individual compounds, total areas of chromatogram profiles were compared. The major esters were found to be methyl butanoate, ethyl butanoate, methyl hexanoate, and ethyl hexanoate. With the application of principal component analysis and analysis of variance to the data matrix, the varieties were classified into three groups. Var. Honeoye was most different from the others. Organic cultivation had no effect on strawberry volatiles. 相似文献