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排序方式: 共有335条查询结果,搜索用时 15 毫秒
101.
Bibhuti B. Mazumder Yoshito Ohtani Zhou Cheng Kazuhiko Sameshima 《Journal of Wood Science》2000,46(5):364-370
The viscosity of kenaf bast fiber has been found to be highly sensitive and variable with different pulping methods; therefore, it is important to choose proper chemicals and conditions for pulping and bleaching of kenaf bast fiber. From several pulping experiments, a nonconventional pulping method with a combination of ammonium oxalate pretreatment followed by soda pulping at normal pressure and then acidic chlorite delignification was developed to obtain high-viscosity pulp (162 centipoise). The optimum level of alkali dosage of soda pulping for high-viscosity pulp was found to be 15% (on pulp as NaOH). Pulps showed linear relations between viscosity and xylose or glucose contents, but the combination pulping method gave extremely high pulp viscosity, beyond the relations. The highest viscosity pulp from kenaf bast fiber demonstrated a tear index about twofold and a folding endurance 6.2-fold higher than those of Manila hemp pulp with comparable tensile and burst indexes. The high-viscosity pulp could be used in the production of high-quality currency paper or longevity paper for special uses.Part of this paper was presented at the 43rd Lignin Symposium, Fuchu, Tokyo, October 26–27, 1998 相似文献
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104.
Masatsugu Yamazaki Masumi Okada Kazuhiko Kobayashi Makoto Kimura 《Soil Science and Plant Nutrition》2005,51(2):271-279
In the present study, the effect of free-air CO2 enrichment (FACE) on the diversity and the community structure of aquatic organisms in the floodwater of a paddy field in northern Japan was evaluated. The varieties and the number of aquatic organisms ranging from 30 μm to 2 cm were compared four times at intervals of 20 d between the FACE (599 ppm CO2 ) and ambient air (384 ppm CO2 ) plots during the flooding period of rice cultivation. Aquatic organisms were classified mainly at the order level. Twenty-eight taxonomical groups were detected, and the number of groups in the FACE plots was significantly lower than that in the ambient plots. Zygnematales and Chaetonotida were less frequently detected in the FACE plots. The population densities of Zygnematales, and Chaetonotida also tended to be lower in the FACE plots than in the ambient plots in the late flooding period (after 50 d of flooding). No groups showed a significantly higher population density and frequency of presence in the FACE plots than in the ambient plots. The seasonal variations in the number of taxonomical groups and the community structure of aquatic organisms were less conspicuous in the FACE plots than in the ambient plots. We concluded that the FACE conditions adversely affected the communities of aquatic organisms in paddy fields. 相似文献
105.
Weiguo Cheng Kazuyuki Inubushi Kazuyuki Yagi Hidemitsu Sakai Kazuhiko Kobayashi 《Biology and Fertility of Soils》2001,34(1):7-13
Controlled-environment chambers were used to study the effects of elevated CO2 concentrations on biological N fixation, N mineralization and C decomposition in rice soil. In three chambers, CO2 concentration was maintained at 353ᆣ/396ᆫ µmol mol-1 (day/night; ambient CO2), while in another three, CO2 was maintained at 667ᆸ/700ᆽ µmol mol-1 (day/night; elevated CO2) throughout the growing season. Rice (var. Nipponbare) seedlings were grown under either ambient or elevated CO2 concentrations, and then transplanted into the soils in the corresponding chambers. At different growth stages, soil samples were taken from surface (0-1cm) and sub-surface (1-10cm) layers at the centre of four hills, then sieved (<1 mm) to remove root residues. Fresh soil was used to measure N fixation activity (using the acetylene reduction assay), NH4+ content and organic C. Separate sets of soil samples were transferred to serum bottles and anaerobically incubated at 30°C for 30 days to measure potential rates of N mineralization and C decomposition. Under an elevated atmospheric CO2 concentration, acetylene reduction activity significantly increased in the surface soil layer during the early cultivation stages and in the sub-surface soil layer during the latter part of cultivation. There was no difference in the amount of NH4+ in fresh soils between elevated and ambient CO2 chambers, while the rate of N mineralization was increased by elevated CO2 during the latter part of cultivation. Soils from the elevated CO2 chambers had obviously higher rate of C decomposition than that from the ambient CO2 chambers. CH4 production gradually increased with the growth of rice plants. These results suggest that elevated CO2 affected biological N fixation, N mineralization and C decomposition in submerged rice soil during the different growth stages of rice. 相似文献
106.
Receptor assay-guided isolation of anti-GABAergic insecticidal alkaloids from a fungal culture 总被引:2,自引:0,他引:2
Kuriyama T Kakemoto E Takahashi N Imamura K Oyama K Suzuki E Harimaya K Yaguchi T Ozoe Y 《Journal of agricultural and food chemistry》2004,52(12):3884-3887
The gamma-aminobutyric acid (GABA) receptor bears sites of action for insecticides. To discover GABA receptor-directed insecticides in natural products, fungal culture extracts were screened for their ability to inhibit specific binding of the radiolabeled noncompetitive antagonist [3H]1-(4-ethynylphenyl)-4-n-propyl-2,6,7-trioxabicyclo[2.2.2]octane to housefly head membranes. The screening efforts led to the isolation of two alkaloids from Aspergillus terreus: PF1198A (alantrypinone) and PF1198B (serantrypinone), which had IC50 values of 0.34 and 2.1 microM, respectively, in this assay. These compounds were ca. 47-61-fold selective for housefly vs rat GABA receptors. Both compounds showed insecticidal activity against Myzus persicae in the range of 100-500 ppm. Binding assay-guided screening should provide significant opportunities for the identification of novel and selective insecticides. 相似文献
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109.
Toshiyuki?SuzukiEmail author Tomoji?Igarashi Kazuhiko?Ichimi Masatoshi?Watai Megumi?Suzuki Eri?Ogiso Takeshi?Yasumoto 《Fisheries Science》2005,71(4):948-955
ABSTRACT: Four toxins, okadaic acid (OA), dinophysistoxin-1 (DTX1), pectenotoxin-6 (PTX6), and yessotoxin (YTX), all associated with diarrhetic shellfish poisoning (DSP), were administered via syringe to Scallops Patinopecten yessoensis and their distribution in the hepatopancreas, adductor muscle, and combined other tissues (mantle, gill, gonad) was analyzed by liquid chromatography-mass spectrometry. Toxins exclusively remained in the hepatopancreas irrespective of the injection site, adductor muscle or hepatopancreas. When injected into hepatopancreas, OA, DTX1, and YTX were metabolized to 7- O -palmitoylOA, 7- O -palmitoylDTX1 and 45-hydroxyyessotoxin (45OH-YTX), respectively. Such metabolic changes were insignificant when toxins were injected into the adductor muscle. The residual ratio for each toxin in the hepatopancreas was less than 20%. Mortalities of scallops treated with PTX6 were lower than those treated with other toxins. 相似文献
110.
Nakahara K Roy MK Ono H Maeda I Ohnishi-Kameyama M Yoshida M Trakoontivakorn G 《Journal of agricultural and food chemistry》2003,51(22):6456-6460
Four prenylated flavanones were isolated from the methanol extract of the flowers of Azadirachta indica (the neem tree) as potent antimutagens against Trp-P-1 (3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole) in the Salmonella typhimurium TA98 assay by activity-guided fractionation. Spectroscopic properties revealed that those compounds were 5,7,4'-trihydroxy-8-prenylflavanone (1), 5,4'-dihydroxy-7-methoxy-8-prenylflavanone (2), 5,7,4'-trihydroxy-3',8-diprenylflavanone (3), and 5,7,4'-trihydroxy-3',5'-diprenylflavanone (4). All isolated compounds were found for the first time in this plant. The antimutagenic IC(50) values of compounds 1-4 were 2.7 +/- 0.1, 3.7 +/- 0.1, 11.1 +/- 0.1, and 18.6 +/- 0.1 microM in the preincubation mixture, respectively. These compounds also similarly inhibited the mutagenicity of Trp-P-2 (3-amino-1-methyl-5H-pyrido[4,3-b]indole) and PhIP (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine). All of the compounds 1-4 strongly inhibited ethoxyresorufin O-dealkylation activity of cytochrome P450 1A isoforms, which catalyze N-hydroxylation of heterocyclic amines. However, compounds 1-4 did not show significant inhibition against the direct-acting mutagen NaN(3). Thus, the antimutagenic effect of compounds 1-4 would be mainly based on the inhibition of the enzymatic activation of heterocyclic amines. 相似文献