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排序方式: 共有212条查询结果,搜索用时 31 毫秒
81.
Kei’ichiro Iguchi Ken Fujimoto Hideki Kaeriyama Atsushi Tomiya Masahiro Enomoto Shin-ichiro Abe Toshinori Ishida 《Fisheries Science》2013,79(6):983-988
The Fukushima nuclear accident led to deposition of radionuclides into the freshwater fishery ground of ayu Plecoglossus altivelis. For the purpose of more comprehensive understanding of the radioactive contamination, cesium-137 (137Cs) was analyzed in running water, muddy sediment, attached algae, and ayu using samples from three river systems with different levels of contamination within Fukushima Prefecture in summer and autumn 2011. The amount of 137Cs contained in water as well as in sediment declined over an interval of two months, although the concentration in sediment samples was up to 10,000-fold higher than that in water samples. The changes in 137Cs concentration of algae showed different courses among the three river systems, the concentration being greater in autumn in the river systems with high and moderate radioactive contamination. 137Cs detected within a single stock of ayu appeared to be excreted rather rapidly with a calculated half-life of approximately 39 days, while the concentration ratio ranged from 103 to 104 l/kg, attaining higher levels than previously reported. These findings indicate that the most important pathway of 137Cs into ayu is via intake of algae as food but that the retention time of 137Cs inside ayu is relatively short. 相似文献
82.
It is important to select the most appropriate method for fish sampling in streams and rivers; the sampling efficiency as well as any negative effect of the method of fish sampling on fishes such as stress, injury, and mortality must be considered. This study aimed to investigate stress hormone responses in ayu Plecoglossus altivelis in reaction to direct current (DC) electrofishing, alternating current (AC) electrofishing, and cast netting in artificial streams. The mortality, injury rate, and catch efficiency of these catching methods were also compared. It was found that immediately after capture, fish caught using a cast net exhibited significantly higher cortisol levels than did control fish that were caught rapidly by a hand net. Cortisol levels did not differ between electroshocked fish and the controls. Time required to catch 12 fish was shorter when DC was used (20 s) than when AC was used (45 s). The time required to catch fish greatly increased when a cast net was used (840 s). Cortisol levels in DC electroshocked and control treatment groups were at resting levels 24 and 48 h after capture. However, higher cortisol levels were found in fish captured using a cast net at both these time points. Cortisol levels in AC electroshocked fish returned to lower levels at 24 h, but increased again at 48 h. Furthermore, 48 h following capture, the fish caught by AC electrofishing exhibited higher mortality (7.5 %) than those captured by other methods (0 %). Spinal injury was also detected in one of the fish in this group. Considering these findings, DC electrofishing is the most effective and least damaging method for collecting P. altivelis in streams with respect to stress, physical damage, and efficiency. 相似文献
83.
Shengjin WU Motoki NISHIHARA Yoshie KAWASAKI Akitoshi YOKOYAMA Kei MATSUURA Tomohiro KOGA Daisuke UENO Koichi INOUE Takashi SOMEYA 《Soil Science and Plant Nutrition》2009,55(2):258-263
Contamination of agricultural soil by fecal pathogenic bacteria poses a potential risk of infection to humans. For the biosafety control of field soil, soil solarization in an upland field was examined to determine the efficiency of solarization on the inactivation of Escherichia coli inoculated into soil as a model microorganism for human pathogenic bacteria. Soil solarization, carried out by sprinkling water and covering the soil surface with thin plastic sheets, greatly increased the soil temperature. The daily average temperature of the solarized soil was 4–10°C higher than that of the non-solarized soil and fluctuated between 31 and 38°C. The daily highest temperature reached more than 40°C for 8 days in total in the solarized soil during the second and third weeks of the experiment. Escherichia coli in the solarized soil became undetectable (< 0.08 c.f.u. g−1 dry soil) within 4 weeks as a result, whereas E. coli survived for more than 6 weeks in the non-solarized soil. Soil solarization, however, had little influence on the total direct count and total viable count of bacteria in the soil. These results indicate that soil solarization would be useful for the biosafety control of soil contaminated by human pathogens via immature compost or animal feces. 相似文献
84.
Rumi Kaida Tomomi Kaku Kei’ichi Baba Masafumi Oyadomari Takashi Watanabe Sri Hartati Enny Sudarmonowati Takahisa Hayashi 《Journal of Wood Science》2009,55(5):381-386
We examined the saccharification and fermentation of meals from Acacia mangium wood, Paraserianthes falcataria wood, and Elaeis guineensis trunk. The levels of enzymatic hydrolysis of cellulose and ethanol production were highest for P. falcataria wood and lowest for A. mangium wood. Ultrasonication pretreatment of meal further increased the rates of hydrolysis and ethanol production in meal from
P. falcataria wood. Through this pretreatment, hemicelluloses (xylan and xyloglucan) and cellulose were released in the meal from P. falcataria wood. Loosening of hemicellulose associations can be expected to make P. falcataria wood more useful for bioethanol production. 相似文献
85.
Monotonic and reversed cyclic loading tests were conducted on dowel-type timber joints with varying degrees of wood decay
due to Fomitopsis palustris (Berk. et Curt.), a brown rot fungus, and the effect of decay on various shear performances of dowel-type joints was investigated.
For joints affected by the brown rot fungus, the initial stiffness, yield load, and maximum load of dowel-type joints were
significantly decreased, even with a small mass loss of wood. The reductions in shear performance were the largest for initial
stiffness, followed by yield load and maximum load, in that order. For a 1% reduction of the yield load, initial stiffness
and maximum load showed reductions of 1.15% and 0.77%, respectively. When dowel-type joints that had been exposed to the brown
rot fungus were subjected to reversed cyclic loading, the gap between the dowel and the lead hole of the wood was increased
and equivalent viscous damping was decreased. These results indicate that decay around the dowel lead hole especially affects
the load-displacement behavior at small displacement level, and dowel-type joints under cyclic loading have very low resistance
to forces acting on the wooden structure.
Part of this report was presented at the 5th Symposium on Timber Bridges of the Japan Society of Civil Engineers, Tokyo, July
2006; the 56th Annual Meeting of the Japan Wood Research Society, Akita, August 2006; and the Annual Meeting of the Architectural
Institute of Japan, Fukuoka, August 2007 相似文献
86.
87.
Koichi Unami Kei Ishida Toshihiko Kawachi Shigeya Maeda Junichiro Takeuchi 《Paddy and Water Environment》2010,8(2):105-111
Adults of Carassius auratus grandoculis ascend from Lake Biwa, Japan, into riparian paddy fields via agricultural drainage systems for the purpose of spawning. However,
land improvement works conducted in the second half of the twentieth century have brought about obstacles for passage of the
fish, and several restoration projects to recover the migratory environment are being attempted. A continuous Markov process
model is presented to scientifically support such a project, defining an ascending probability that quantitatively assesses
the ability of an agricultural drainage system with hydraulic structures for the ascent of the fish. Computational methods
are developed to numerically obtain flow fields of the agricultural drainage system and then the ascending probability in
the entire spatio-temporal domain. The values of model parameters are deductively inferred, referring to results of field
observations. From the computational results of the ascending probability in the agricultural drainage system, effects of
hydraulic structures allowing ascent of the fish are clarified. 相似文献
88.
Chie Imagawa Junichiro Takeuchi Toshihiko Kawachi Kei Ishida Shunsuke Chono Natsuki Buma 《Paddy and Water Environment》2011,9(4):425-439
Long-term simulation using the distributed hydro-environmental watershed model is efficacious for assessing irrigation impacts
on hydrological cycle in detail and for implementing watershed management successfully. In this article, the previously developed
hydro-environmental watershed model (HEWM-1) is improved in the water exchange process caused by surface water-groundwater
interaction via drainage canals and/or underdrains. The time-varying stream flow in canals is described by the complete one-dimensional
shallow water equations in a newly introduced submodel, the open channel flow submodel. This submodel coordinates with the
other submodels: the tank, soil moisture and groundwater flow submodels which are interlinked in a cascade manner. The improved
model (HEWM-2) is applied to an agricultural watershed covering an area from an alluvial fan onto a nearly level alluvial
plain, to be validated. The simulation by HEWM-2 is informative for identifying whether any drainage canal is gaining or losing
water in relation to groundwater level. It could thus provide useful information for conserving a complex network of drainage
canals which also functions as a passage for aquatic animals like fishes. 相似文献
89.
Somfai T Inaba Y Aikawa Y Ohtake M Kobayashi S Konishi K Nagai T Imai K 《Acta veterinaria Hungarica》2010,58(4):465-474
The aim of the present study was to optimise the culture conditions for the in vitro production of bovine embryos. The development of in vitro fertilised bovine oocytes in CR1aa supplemented with 5% calf serum and IVD101 culture media were compared using traditional microdrops and Well of the Well (WOW) culture systems either under 5% or 20% oxygen tension. After 7 days of culture, a significantly higher blastocyst formation rate was obtained for embryos cultured in CR1aa medium compared to those cultured in IVD101, irrespective of O2 tensions and culture systems. The blastocyst formation in IVD101 was suppressed under 20% O2 compared to 5% O2 . Despite their similar total cell numbers, higher rates of inner cell mass (ICM) cells were observed in blastocysts developed in IVD101 medium than in those developed in CR1aa, irrespective of O2 tensions. There was no significant difference in blastocyst formation, total, ICM and trophectoderm (TE) cell numbers between embryos obtained by microdrop and WOW culture systems irrespective of the culture media and O2 tensions used. In conclusion, CR1aa resulted in higher blastocyst formation rates irrespective of O2 tension, whereas IVD101 supported blastocyst formation only under low O2 levels but enhanced the proliferation of ICM cells. 相似文献
90.
EMI SAKUNO TSUNASHI KAMO TOMOKO TAKEMURA HAJIME SUGIE SYUNTARO HIRADATE YOSHIHARU FUJII 《Weed Biology and Management》2010,10(3):202-207
The methanol extract of Bletilla striata, an ornamental orchid in eastern Asia, exhibited plant growth‐inhibitory activity. It was purified by continuous chromatography, based on the inhibitory activity against the growth of lettuce seedlings, resulting in two glycosidic compounds, militarine and dactylorhin A. The EC50 values of militarine and dactylorhin A against the radicle elongation of the lettuce seedlings were 0.28 and 0.88 mmol L?1, respectively. The amount of militarine and dactylorhin A in the methanol extract of the aerial part of B. striata was calculated to be 5.6 and 7.5 mg g?1 fresh weight, respectively. The inhibitory activity of militarine and its content in the methanol extract revealed that the plant growth‐inhibitory activity of the extract of B. striata was mainly related to militarine. The inhibitory activity of militarine against the growth of Italian ryegrass and timothy were of the same level as that of lettuce. 相似文献