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991.
Soil microbes are an essential component of most terrestrial ecosystems; as decomposers they are responsible for regulating nutrient dynamics, and they also serve as a highly labile nutrient pool. Here, we evaluated seasonal variations in microbial biomass carbon (MBC) and nitrogen (MBN) as well as microbial activity (as qCO2) for 16 months with respect to several factors relating to soil moisture and nutrients under different land management practices (plant residue application, fertilizer application) in both clayey (38% clay) and sandy (4% clay) croplands in Tanzania. We observed that MBC and MBN tended to decrease during the rainy season whereas they tended to increase and remain at high levels during the dry season in all treatment plots at both of our test sites, although soil moisture did not correlate with MBC or MBN. qCO2 correlated with soil moisture in all treatment plots at both sites, and hence soil microbes act as decomposers mainly during the rainy season. Although the effect of seasonal variation of soil moisture on the dynamics of MBC, MBN, and qCO2 was certainly greater than that attributable to plant residue application, fertilizer application, or soil texture, plant residue application early in the rainy season clearly increased MBC and MBN in both clayey and sandy soils. This suggests that plant residue application can help to not only counter the N loss caused by leaching but also synchronize crop N uptake and N release from soil microbes by utilizing these microbes as an ephemeral nutrient pool during the early crop growth period. We also found substantially large seasonal variations in MBC and MBN, continuously high qCO2, and rapid turnover of soil microbes in sandy soil compared to clayey soil. Taken together, our results indicate that soil microbes, acting as both a nutrient pool and decomposers, have a more substantial impact on tropical sandy soil than on clayey soil. 相似文献
992.
993.
Toshikazu Irie Yoichi Honda Hyo-Cheol Ha Takashi Watanabe Masaaki Kuwahara 《Journal of Wood Science》2000,46(3):230-233
We have isolated the cDNA and genomic sequences encoding the major isozyme of manganese peroxidase, MnP3, from the white rot basidiomycetePleurotus ostreatus strain IS1. The genemnp3 is interrupted by 10 introns and encodes a mature protein of 357 amino acid residues with a 26-amino-acid signal peptide. The amino acid residues known to be involved in peroxidase function and those that form the Mn-binding site in thePanerochaete chrysosporium MnP isozyme are conserved in MnP3. Comparison of the deduced primary structure of MnP3 with those of other peroxidases from various white rot fungi suggested that MnPs fromP. ostreatus andTrametes versicolor belong to a subgroup that is more similar to the lignin peroxidases than MnPs fromP. chrysosporium orCeriporiopsis subvermispora. 相似文献
994.
Masahiro Takatani Osamu Kato Takashi Kitayama Tadashi Okamoto Mitsuhiko Tanahashi 《Journal of Wood Science》2000,46(3):210-214
The effect of steam-exploded wood flour (SE) added to wood flour/plastic composite was examined using SE from beech, Japanese cedar, and red meranti and three kinds of thermoplastic polymer: polymethylmethacrylate, polyvinyl chloride, and polystyrene. Addition of SE increased the fracture strength and water resistance of the composite board to an extent dependent on the polymer species and the composition of wood/SE/polymer. However, water resistance decreased with the increasing proportion of SE when SE meranti was added. Effects of the wood species of SE on the properties of resulting board were small. An increased moisture content of wood flour or SE (or both) increased the variation of board performance. 相似文献
995.
A detection method specific for Xanthomonas oryzae pv. oryzae, the pathogen responsible for bacterial blight of rice, was based on the polymerase chain reaction (PCR) and designed by amplifying
the 16S–23S rDNA spacer region from this bacterium. The nucleotide sequence of the spacer region between the 16S and 23S rDNA,
consisting of approximately 580-bp, from X. oryzae pv. oryzae, X. campestris pv. alfalfae, X. campestris pv. campestris, X. campestris pv. cannabis, X. campestris pv. citri, X. campestris pv. cucurbitae, X. campestris pv. pisi, X. campestris pv. pruni and X. campestris pv. vitians, was determined. The determined sequences had more than 95% identity. Therefore, a pair of primers, XOR-F (5′-GCATGACGTCATCGTCCTGT-3′)
and XOR-R2 (5′-CTCGGAGCTATATGCCGTGC-3′) was designed and found to specifically amplify a 470-bp fragment from all strains
of X. oryzae pv. oryzae isolated from diverse regions in Japan. No PCR product was amplified from X. campestris pathovars alfalfae, campestris, cannabis, carotae, cucurbitae, dieffenbachiae, glycines, pisi, pruni, vitians or zantedeschiae, except for pathovars citri, incanae and zinniae. The method could also detect the pathogen in infected rice leaves within 3 hr, at a detection limit of 4×101 cfu/ml.
Received 17 December 1999/ Accepted in revised form 10 April 2000 相似文献
996.
Viral movement in the leaf tissues of a resistant host, Cucumis figarei, inoculated with the pepo strain of Cucumber mosaic virus (CMV) and incubated at 24°C or 36°C was investigated by fluorescence in situ hybridization (FISH), leaf-press blotting, tissue printing and immunogold-silver staining techniques. Observation by FISH
revealed that at 24°C most infection sites with CMV at 0.01 mg/ml or 0.1 mg/ml were limited to a single cell during the incubation
period, that the number of infection sites increased from 24hpi (hours post inoculation) to 80 hpi in the leaves inoculated
with CMV at 0.5 mg/ml, and that the size as well as the number of infection sites rapidly increased with time in the leaves
inoculated with CMV at 2.0 mg/ml. These results suggested that one factor for the resistance of C. figarei at 24°C might be an inhibition of viral movement in and out of the infection sites. Leaf-press blotting and tissue blotting
indicated that CMV remained in the infection sites at 24°C, whereas it spread from the inoculated leaves to other parts of
the plants through vascular systems at 36°C. Immunogold-silver staining demonstrated that at 24°C CMV infected bundle sheath
(BS) cells in minor veins, whereas at 36°C it invaded not only BS cells, but also phloem parenchyma (PP)/ companion cell (CC)
or PP/intermediary cell (IC) complexes in minor veins in the regions with chlorotic symptoms. These results indicated that
at 24°C CMV had difficulty in passing through the interface between BS and PP/CC or PP/ IC complexes and that viral entry
from mesophyll to the phloem pathway was inhibited in the inoculated leaves.
Received 26 August 1999/ Accepted in revised form 14 December 1999 相似文献
997.
998.
To evaluate the importance of acetic acid and 3-hydroxybutyric acid (3-HB) in cerebrospinal fluid (CSF) of cattle, CSF samples were taken from a population of 60 cattle including healthy and sick animals with central nervous disorders. Mean acetic acid and 3-HB levels in blood plasma were 0.30 (SD 0.24) and 0.30 (SD 0.28) mM, and those in CSF were 0.14 (SD 0.06) and 0.08 (SD 0.07) mM, respectively. Significant differences were observed between plasma and CSF samples for both acetic acid and 3-HB levels. Acetic acid levels in CSF showed less relationship with those in blood plasma, whereas plasma 3-HB levels accompanied proportional changes with its CSF levels, which were about 30% of plasma 3-HB. It was revealed that both acetic acid and 3-HB levels in plasma and CSF have less relationship to glucose levels in plasma and CSF; therefore, the decrease of glucose levels in plasma or CSF is not necessarily accompanied by hyperketonemia. 相似文献
999.
1000.
Takashi Hirooka Yukio Miyagi Fujio Araki Hitoshi Kunoh Hiroshi Ishizaki 《Pest management science》1982,13(4):379-386
The effect of isoprothiolanea (di-isopropyl 1,3-dithiolan-2-ylidenemalonate), a systemic fungicide used for rice blast control, on the infection process of Pyriculuria oryzae was studied by micromanipulation in a scanning electron microscope. Whether or not infection pegs emerged from the appressoria was examined by inverting each appressorium contact surface. Infection pegs were observed on more than 80% of the appressoria, 48 h after inoculation, on both untreated rice leaves and cellophane film. Isoprothiolane, approximately 10 μg ml?1 in the ambient water of inoculated conidia, reduced the emergence of infection pegs on rice leaves and cellophane film by 96 and 100%, respectively. 相似文献