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71.
Gaylord Erwan Machinet Isabelle Bertrand Yves Barrière Sylvie Recous 《Soil biology & biochemistry》2011,43(7):1544-1552
Residue quality is a key factor governing biodegradation and the fate of C in soil. Most investigations of relationships existing between crop residue quality and soil decomposition have been based on determining the relative proportions of soluble, cellulose, hemicellulose and lignin components. However, cell wall cohesion is increased by tight interconnections between polysaccharides and lignin that involve cross-linking agents (phenolic acids). The aim of this study was to determine the role of lignin composition and phenolic acids on short- to medium-term decomposition of maize roots in soil. Sixteen maize genotypes, presenting a range of chemical characteristics related to root lignin and phenolic acids, were used. The main components were characterized by Van Soest (VS) extraction and cell wall acid hydrolysis, and the non-condensed Syringyl and Guaicyl lignin monomers, esterified phenolic acids and etherified phenolic acids were determined. Maize roots were then incubated in soil under controlled conditions (15 °C, −80 kPa moisture) for 796 days. Results showed that VS extraction over-estimated the structural hemicellulose content and that VS lignin was more recalcitrant than Klason lignin. The tremendous effect of cell wall chemical characteristics was shown by marked variations (almost two-fold differences in C mineralization), between the 16 maize roots. Decomposition was controlled by soluble residue components in the short term whereas lignin and the interconnections between cell wall polymers were important in the long-term. Notably the cell wall domain rich in non-condensed lignin and esterified phenolic acids was prone to decomposition whereas the presence of etherified ferulic acids seemed to hamper cell wall decomposition. 相似文献
72.
Colin Nakata Clara Qualizza Mike MacKinnon Sylvie Renault 《Water, air, and soil pollution》2011,214(1-4):59-72
Methylibium petroleiphilum PM1, which is capable of degrading of methyl tert-butyl ether (MTBE), was immobilized in calcium alginate gel beads. Various applications were explored to increase the mechanical strength of these gel beads. The introduction of 0.3 mol/L calcium chloride into the crosslinking solution, 0.002 mol/L calcium chloride into the growth medium, and 0.2% polyethyleneimine (PEI) as chemical crosslinking agent increased the stability of the Ca-alginate gel beads under the operation conditions of the bioreactor. The degradation rates of MTBE by the immobilized cells in the bioreactor system operated in batch and continuous mode , respectively, were compared. A MTBE biodegradation rate of 5.79 mg/L·h was reached for over 400 h (50 batches), and the immobilized cells in the bioreactor removed >96% MTBE during 50 days of operation. Molecular analysis of the PM1 cells revealed that microbial growth occurred predominantly as microcolonies in the outer area of the beads during the first 20 days of operation. The results of this study show that a continuous-mode, fixed-bed bioreactor reactor coupled with PM1-immobilized cells is a promising technology for remediating MTBE-contaminated groundwater. 相似文献
73.
Thanh Thuy Nguyen Tu Céline Egasse Gérard Bardoux Jean-François Ponge Sylvie Derenne 《Soil biology & biochemistry》2011,43(11):2222-2228
We monitored the carbon isotope composition of bulk leaves and specific long-chain alkanes during a four-year litterbag experiment using 13C-labelled leaves and unlabelled reference leaves of the European beech tree (Fagus sylvatica L.). Whereas the isotope composition of alkanes from 13C-enriched leaves exhibited a marked decrease in 13C-content, the isotope composition of unlabelled reference leaves remained nearly constant. We interpreted this difference as evidence for a microbial contribution to the long-chain alkane pool of the decomposing leaves and related it to the progressive invasion of leaves by soil organisms which was revealed upon microscopic examination. These results suggest that long-chain alkanes may not provide an unaltered record of organic carbon isotope composition in soils and sediments. 相似文献
74.
The ability of plants to utilize P efficiently is important for crops growing in P‐deficient soils or on soils with a high P‐fixing capacity. The purpose of this work was to investigate early physiological changes which occur when wheat (Triticum aestivum L.) seedlings were grown under P‐deficient conditions. Wheat plants were grown in a greenhouse and watered with nutrient solution containing or lacking P. During the interval 12 to 18 days after planting, the dry weight of wheat seedlings was similar regardless of P treatment, although the P‐deficient plants had a greater proportion of the total plant weight in the roots. Sixteen days after planting, the roots and leaves of P‐deficient plants had only 20 to 30% the P content of P‐sufficient plants. After 16 days, plants grown under P stress had 41% more p‐nitrophenol phosphatase activity and 70% more β‐glucosidase activity in shoot homogenates than was found in P‐sufficient plants. Changes in both enzyme activities may be involved in the mobilization of plant resources during the early stages of P‐deficient growth. 相似文献
75.
Summary The susceptibility of 21 potato cultivars to leak (watery wound rot) caused byPythium aphanidermatum was compared. Whole tubers were inoculated after wounding by dipping into a water suspension of 103 oospores/ml and incubated for 3 days at 25°C. The mean penetration of tissue calculated from the recording of lesion width
and depth and the qualitative assessment of rot extension were highly correlated. For 10 of 12 cultivars tested at least twice,
consistent reactions were obtained: cvs Korrigane. Superstar, Safrane and Yesmina were moderately susceptible, whereas Atlas,
Diamant, Mondial, Obélix, Spunta and Timate were susceptible to highly susceptible. Tubers originated from two locations and/or
two cropping seasons: thus, the performance of these cultivars under different production conditions reveals a satisfactory
level of agreement with the test. Moreover, ratings assigned are supported by field or store observations. 相似文献
76.
Summary This paper reports results of a 3-year evaluation of CIP advanced potato clones in a bacterial wilt-infested field (race 3)
in Peru. Clones resistant or moderately resistant to wilt were selected and all tubers harvested from each clone were tested
for latent infection byRalstonia solanacearum using a sensitive serological technique developed at CIP. A sampling strategy to estimate accurately the frequency of infected
tubers in the clones has been evaluated. This method will allow consideration of tuber latent infection as a new selection
criterion in breeding for resistance to bacterial wilt. Thirteen clones were found resistant to wilt in all three evaluations
(i.e.≤6% wilt), from which five had no wilt in all trials. However, all clones harboured latent infection in tubers averaging
30%. Analysing 30 tubers/clone provides an accurate estimation of the proportion of infected tubers with a high precision
level. 相似文献
77.
Micha?l C Fontaine Krystal A Tolley Ursula Siebert Sylvie Gobert Gilles Lepoint Jean-Marie Bouquegneau Krishna Das 《BMC ecology》2007,7(1):1
Background
We investigated the feeding ecology and habitat use of 32 harbour porpoises by-caught in 4 localities along the Scandinavian coast from the North Sea to the Barents Sea using time-integrative markers: stable isotopes (δ13C, δ15N) and trace elements (Zn, Cu, Fe, Se, total Hg and Cd), in relation to habitat characteristics (bathymetry) and geographic position (latitude). 相似文献78.
Landscape Ecology - Sets of ecosystem services that occur together across space or time are called ‘bundles’, and the interactions among them can result in synergies or trade-offs.... 相似文献
79.
Reuben M.J. Kadigi Ntengua S.Y. Mdoe Gasper C. Ashimogo Sylvie Morardet 《Agricultural Water Management》2008,95(8):984-992
The need for achieving efficient, equitable and sustainable use of water resources to meet water demands of different sectors is pressing, particularly in areas where water resources are dwindling. Along with this is the quest for having a good understanding of the value of water in its different uses. Using a simplified model derived from the residual imputation approach (the Change in Net Income Model) we assess the value of water in irrigated paddy and hydropower generation in the Great Ruaha River Catchment (GRRC) in Tanzania. The estimated productivity of water (PW) in irrigated paddy ranges from 0.059 to 0.250 kg/m3 (for withdrawn water) and 0.126 to 0.265 kg/m3 (for consumed water). The PW in hydropower generation is estimated to range from 0.45 to 1.68 kWh/m3. In monetary terms the value of water in irrigated paddy is estimated at 15.3 Tanzanian shilling (Tsh)/m3 (for water withdrawn) and 0.19 Tsh/m3 (for water consumed). The values of water for hydropower generation are relatively higher than for irrigated paddy, ranging from 59 to 226 Tsh/m3. Yet, irrigated paddy also supports livelihoods of about 30,000 agrarian families in the GRRC, with gross revenue of about Tsh 15.9 million per annum and GRCC paddy contributes about 14–24% of national rice production. We conclude that understanding the value of water in its alternative uses is key to fostering informed debate on water management and allocation, identifying the basis for making ‘agreeable’ trade-offs, the potential for improvement and creating linkages with water allocation options particularly in agricultural-based economies, where agriculture competes with other sectors and where water re-allocation decisions may involve large transfers of water from the sector generating the highest pro-poor returns (agriculture for this case) to the sectors generating the highest economic returns (hydropower generation and industrial uses). 相似文献
80.
Résumé Les antisérums sont obtenus en immunisant deux lapins par voie intraveineuse avec des antigènes purifiés par chromatographie
d'échange d'ions. On utilise deux préparations d'extraits mycéliens: normale et chauffée. La spécificité des anticorps obtenus
est appréciée sur différentes souches deRhizoctonia. Deux techniques sérologiques sont utilisées: immunodiffusion et ELISA indirect. Les deux immunsérums obtenus présentent
la même spécificité vis-à-vis du groupe AG3. Les deux techniques permettent la reconnaissance du groupe AG3 à partir des sclérotes
formés sur tubercules.
Summary Total mycelial extract ofR. solani AG3 was purified by ion-exchange chromatography. Beforehand part of the extract was heat-treated at 60°C for 10 min (Ch) and the rest left untreated (N). Results of the chromatographic analysis are given in Fig. 3. Electrophoretic analysis of the peak fractions is shown in Fig. 2. Peak C was chosen as antigen for the preparation of the two antisera by intravenous injections in two rabbits. Antibodies obtained were titrated in both cases by immunodiffusion and in indirect ELISA (Fig. 4). Specificity was examined by immunodiffusion and ELISA on heat-treated extracts of reference strains listed in Table 1. Similar results were obtained for the two antisera which were both specific to AG3 (Fig. 1 and Table 2). Characterisation tests were done by the two methods directly on sclerotia of tubers of different cultivars and origins harvested in 1991 (Table 3). The purified antigens appeared to be of a complex nature (peptides-polysaccharides) and were very immunogenic. Antibodies raised against them were sufficiently specific as to allow the identification ofR. solani AG3 sclerotica on tubers.相似文献