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排序方式: 共有137条查询结果,搜索用时 109 毫秒
51.
Vanda Acácio Milena Holmgren Francisco Rego Francisco Moreira Godefridus M. J. Mohren 《Agroforestry Systems》2009,76(2):389-400
In the Iberian Peninsula Mediterranean oak forests have been transformed into a mosaic landscape of four main patch-types:
forests, savannas, shrublands and grasslands. We used aerial photographs over a period of 45 years (1958–2002) to quantify
the persistence and rates of transitions between vegetation patch-types in southern Portugal, where cork oak is the dominant
tree species. We used logistic regression to relate vegetation changes with topographical features and wildfire history. Over
the 45 years, shrublands have been the most persistent patch-type (59%), and have been expanding; forests are also persistent
(55%) but have been decreasing since 1985; savannas and grasslands were less persistent (33% and 15%, respectively). Shrublands
persistence was significantly correlated with wildfire occurrence, particularly on southern exposures after 1995. In contrast,
forest persistence decreased with wildfire occurrence, and forests were more likely to change into shrublands where wildfire
had occurred after 1995. 相似文献
52.
Milena Pietraszko Grzegorz Gryń Włodzimierz Przewodowski 《American Journal of Potato Research》2018,95(3):278-285
The aim of research was to evaluate an effect of weather conditions in the years of study considering the air temperature and precipitation as well as granulometric distribution of soil, taking into account the temperature and moisture content, on asymptomatic infection caused by Clavibacter michiganensis subsp. sepedonicus (Cms) in leaves and tubers. The level of infection of leaves and tubers with Cms was differentiated by the thermal and humidity conditions occurring in the years of research. The granulometric distribution of soil (soil profile) had a significant effect on the level of leaf infection. In the year 2014, with moderate temperature and humidity, the highest intensity of leaves and tubers infection was observed on soil of the highest moisture content – sandy loam. In the years with extreme weather conditions, i.e. the drought in 2015 or the abundant rainfall in 2016, the most intensive infection was observed in leaves and tubers grown on soil of low humidity – slightly loamy sand and loamy sand. The degree of infection was found to decrease with increasing air temperature and precipitation level as well as with the increase of soil moisture. On the other hand, increasing soil temperature favoured infection in tubers. 相似文献
53.
Lauri Rautkari Milena Properzi Frédéric Pichelin Mark Hughes 《Wood Science and Technology》2010,44(4):679-691
The chemistry and wetting behaviour of surface densified wood were investigated using FT-IR spectroscopy and contact angle
analyses. Furthermore, set-recovery of the surface under conditions of fluctuating humidity was measured and quantitative
microscopy analyses were undertaken. FT-IR indicated that no significant chemical changes took place during the densification
process. However, the wettability of the densified surfaces was significantly lower than unmodified surfaces. Following several
high humidity-oven dry cycles, it was found that this densification process was almost completely reversible, i.e., there
was full set-recovery. 相似文献
54.
Gorinstein S Leontowicz H Leontowicz M Namiesnik J Najman K Drzewiecki J Cvikrová M Martincová O Katrich E Trakhtenberg S 《Journal of agricultural and food chemistry》2008,56(12):4418-4426
Polish garlic and white and red onions were subjected to blanching, boiling, frying, and microwaving for different periods of time, and then their bioactive compounds (polyphenols, flavonoids, flavanols, anthocyanins, tannins, and ascorbic acid) and antioxidant activities were determined. It was found that blanching and frying and then microwaving of garlic and onions did not decrease significantly the amounts of their bioactive compounds and the level of antioxidant activities ( P > 0.05). The HPLC profiles of free and soluble ester- and glycoside-bound phenolic acids showed that trans-hydroxycinnamic acids (caffeic, p-coumaric, ferulic, and sinapic) were as much as twice higher in garlic than in onions. Quercetin quantity was the highest in red onion among the studied vegetables. The electrophoretic separation of nonreduced garlic and onion proteins after boiling demonstrated their degradation in the range from 50 to 112 kDa. 相似文献
55.
Malaki Nik A Tosh SM Poysa V Woodrow L Corredig M 《Journal of agricultural and food chemistry》2008,56(22):10893-10900
Harovinton, a variety of tofu type soybean, and 11 derived null soybean genotypes lacking specific glycinin (11S) and beta-conglycinin (7S) protein subunits were investigated to determine whether changes in protein composition affected the protein recovery in soymilk and its soluble fractions after various centrifugation steps. As both heating and homogenization have a marked effect on the increase in protein solubility, the changes occurring during these processing steps were studied for each soybean genotype. Harovinton and 11S-null genotypes showed significantly higher protein yields than the other genotypes evaluated. Subunits of group I (A(1), A(2)) of glycinin had a negative impact on protein solubility in all treatments, but this effect was the greatest in unheated soymilk samples. Samples containing a high beta-conglycinin to glycinin ratio showed an effect of heating on the solubility of the protein, as beta-conglycinin subunits aggregate with heating. The presence of the alpha' subunit of beta-conglycinin aids in the recovery of protein in the supernatant prepared from lines containing group I (A(1,4) A(2)) glycinin. The results of this study will help determine which specific protein composition will confer an increased stability in soymilk and soymilk-derived products. 相似文献
56.
Corredig M Verespej E Dalgleish DG 《Journal of agricultural and food chemistry》2004,52(14):4465-4471
The physical aggregation of commercial whey protein isolate (WPI) and purified beta-lactoglobulin was studied by ultrasound spectroscopy. Protein samples were dialyzed to achieve constant ionic strength backgrounds of 0.01 and 0.1 NaCl, and gelation was induced in situ at constant temperatures (from 50 to 75 degrees C) or with a temperature ramp from 20 to 85 degrees C. Changes in the ultrasonic properties were shown in the early stages of heating, at temperatures below those reported for protein denaturation. During heating, the relative ultrasound velocity (defined as the difference between sample velocity and reference velocity) decreased continuously with temperature, indicating a rearrangement of the hydration layer of the protein and an increase in compressibility of the protein shell. At temperatures <50 degrees C the ultrasonic attenuation decreased, and <65 degrees C both velocity and attenuation differentials showed increasing values. A sharp decrease in the relative velocity and an increase in the attenuation at 70 degrees C were indications of "classical" protein denaturation and the formation of a gel network. Values of attenuation were significantly different between samples prepared with 0.01 and 0.1 M NaCl, although no difference was shown in the overall ultrasonic behavior. WPI and beta-lactoglobulin showed similar ultrasonic properties during heating, but some differences were noted in the values of attenuation of WPI solutions, which may relate to a less homogeneous distribution of aggregates caused by the presence of alpha-lactalbumin and other minor proteins in WPI. 相似文献
57.
Stabilizing behavior of soy soluble polysaccharide or high methoxyl pectin in soy protein isolate emulsions at low pH 总被引:2,自引:0,他引:2
Roudsari M Nakamura A Smith A Corredig M 《Journal of agricultural and food chemistry》2006,54(4):1434-1441
The stability of emulsions prepared with soy protein isolates was investigated as a function of pH in the presence of two negatively charged polysaccharides: high methoxyl pectin (HMP) and soy soluble polysaccharide (SSPS). Both polysaccharides are composed of a backbone which contains galacturonic acid but, when added to soy protein isolate-stabilized emulsions, SSPS showed a different behavior than that of HMP. At neutral pH and above a critical concentration of stabilizer (0.05%), HMP caused flocculation of the emulsion droplets via a depletion mechanism. On the other hand, the emulsions containing a similar amount of SSPS did not show creaming or flocculation. At acidic pH (<4.0) the addition of pectin caused extensive droplet aggregation, while no aggregation was observed with the addition of SSPS. The differences in the stabilization behavior between the two polysaccharides can be attributed to their differences in charge, neutral sugars side chains, and molecular weight. 相似文献
58.
Jacobson M Gerth Löfstedt M Holmgren N Lundeheim N Fellström C 《Journal of veterinary medicine. B, Infectious diseases and veterinary public health》2005,52(9):386-391
The aim of the present study was to survey the prevalences of the enteric pathogens Brachyspira hyodysenteriae, Brachyspira pilosicoli and Lawsonia intracellularis in Swedish growing pigs and in the Swedish wild boar population and to relate these findings to clinical signs. The study included 105 randomly selected herds, constituting approximately one third of Swedish herds with a herd size of >100 sows. The herds were located all over the country. In these herds, growth promoters were not used and pigs sampled were not subjected to any medication. From each herd, samples were taken from 10 growing pigs aged 8-12 weeks, corresponding to approximately 2.5% of all growing pigs present in the herd at the sampling occasion. If possible, the samples were taken from pigs with diarrhoea. Forty-eight faecal samples and 71 rectal swabs were also taken from free-living wild boars (31 piglets, 19 growers and 21 adult animals) at shooting. The samples were analysed by culture and biochemical tests for the presence of Brachyspira spp. and by nested PCR for the presence of L. intracellularis. Brachyspira hyodysenteriae was not demonstrated in any sample. Brachyspira intermedia was detected in 22 samples originating from 15 herds, Brachyspira innocens/Brachyspira murdochii was detected in 370 samples from 82 herds and B. pilosicoli was detected in 134 samples originating from 34 herds. In 21 herds and in 534 samples, no Brachyspira spp. were detected. Lawsonia intracellularis was demonstrated in 285 samples from 50 herds. Further, 418 samples from conventional herds were negative with respect to L. intracellularis and in 345 samples the PCR had been inhibited. All samples from the wild boars were negative for Brachyspira spp., 12 of 48 samples were negative for L. intracellularis, and in 36 wild boar samples, the PCR was inhibited. 相似文献
59.
60.
Marine tardigrades are very poorly known and up to now only c. 200 taxa have been reported around the world (mostly from European coasts). In a marine algae sample, collected on the coast of Fuerteventura island (Atlantic Ocean, Canary Islands), six specimens of three marine Arthrotardigrada species were found: Archechiniscus minutus Grimaldi de Zio & D’Addabbo Gallo, 1987, Styraconyx craticulus (Pollock, 1983) and Styraconyx sargassi Thulin, 1942. This is the third record of marine tardigrades from the Canary Islands. In this paper we also list all heterotardigrades known from marine environments around Africa. 相似文献