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1.
Growth of an ultrathin lead oxide layer causes massive changes in the shape of lead crystallites. The dynamics of this process was investigated with time-lapsed scanning tunneling microscopy. Pure lead crystallites proved extremely resistant to oxidation. Once nucleated by surface impurities, monolayer films of lead oxide grew readily on lead (111) microfacets in an autocatalytic process. The anisotropic growth of orthorhombic lead oxide films (massicot structure) was most rapid along the direction of weakest lead-oxygen bonding, which suggests that the growth edge autocatalyzes oxygen dissociation by providing proximal sites for oxygen dissociation and attachment. 相似文献
2.
Nutrient availability in the soil is not only determined by chemical, physical, and micro-biological factors but can be actively influenced by the plant root system. Various components of root activity have been studied in our laboratory during the last 10 years. The major findings are summarized and discussed with special emphasis on root morphology, cation-anion imbalance and proton release, the mechanism of proton release and anion secretion. Large species differences in root morphology were found between red clover and rye-grass. Root morphology was also found to be controlled by environmental and physiological factors. Experimental results obtained with different plant species suggest that proton release by plant roots is not primarily a consequence of excess cation uptake to achieve charge balance in the plant, but rather that active proton extrusion by ATPase activity creates a charge imbalance and a pH gradient which drive nutrient uptake. The pH gradient across the plasmalemma of root cells was also found to be essential for the retention of organic anions by plant roots. 相似文献
3.
Konrad R. Dabrowski 《Fish physiology and biochemistry》1986,1(3):125-144
Oxygen consumption, ammonia excretion and fish swimming speed were measured in fish induced to swim by optomotor reaction in a circular metabolism chamber. The relationship between the swimming speed and fish metabolism described by exponential equations allowed the extrapolation to the standard metabolism, i.e. at zero swimming speed. The partitioning of the catabolised protein in the energy supply was estimated based on AQ (volume of ammonia/ volume of oxygen) values. Weight specific standard metabolism, as expressed by the ammonia excretion rate, decreased by one order of magnitude in coregonids as the fish grew from 20 to 780 mg body weight. The slope of the relationship between oxygen uptake and swimming speed decreased in coregonid ontogenesis. In salmon, after 12 days of fasting 28% of energy used was derived from protein, whilst coregonid juveniles utilized mostly lipid. Active swimming in fasted juveniles of coregonid, as well as in salmon, led to the accelerated utilization of protein as a source of energy, based on AQ coefficients. In juveniles acclimated to a range of water temperatures from 14 to 26°C, the changes in standard or active metabolic rate (expressed as oxygen uptake or ammonia excretion) were described by Q10 coefficients. They were generally higher for the ammonia excretion rate than for the oxygen uptake rate and for active metabolism than for standard metabolism. Utilization of protein as energy for swimming differed significantly between the species, being in general one order of magnitude higher in coregonids than in salmon. The use of protein for swimming activity tended to decrease during coregonid ontogenesis. 相似文献
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Diets based on fish meal and soyabean meal were fed to grass carp fry, the average body weight of each individual being 0.4 g. During the 70 days of the experiment, the best results were obtained with a diet containing 40% fish meal, when growth increment, protein efficiency ratio and apparent net protein utilization amounted to 209, 1.26 and 20.3, respectively. There was a deficiency in sulphuric amino acids in both fish meal- and soyabean meal-containing diets, and this was particularly marked in the latter. A significant decrease in available lysine was found in the diets containing soyabean meal. The main reason for the retardation in fish growth and the reduction of protein utilization when soyabean meal content is increased in the diets, seemed to be that the destruction of anti-nutritional factors by the heat processing of the meal was only partial. 相似文献
7.
Background
Inkjet micropatterning is a versatile deposition technique with broad applications in numerous fields. However, its application in plant science is largely unexplored. Leaf expansion is one of the most important parameters in the field of plant science and many methods have been developed to examine differential expansion rates of different parts of the leaf lamina. Among them, methods based on the tracking of natural landmarks through digital imaging require a complicated setup in which the leaf must remain fixed and under tension. Furthermore, the resolution is limited to that of the natural landmarks, which are often difficult to find, particularly in young leaves. To study the fine scale expansion dynamics of the leaf lamina using artificial landmarks it is necessary to place small, noninvasive marks on a leaf surface and then recover the location of those marks after a period of time. 相似文献8.
R. E. Ciereszko Konrad Dabrowskl A. Ciereszko J. Ebeling J. S. Ottobre 《Journal of the World Aquaculture Society》1997,28(4):344-356
The involvement of photoperiod and temperature in the regulation of reproductive processes was investigated in female yellow perch. Initially, all fish kept indoors were exposed to the same water temperature (22°C) and photoperiod (15L:9D). By the end of August, following the first sampling, fish were submitted to different photothermal regimes. Group A3 was maintained under photothermal conditions characteristic for southern Ohio. Group B3 was submitted to a condensed light/temperature regime designed to accelerate photothermal changes. The mean gonadosomatic index in group A3 gradually increased throughout the experiment. Gonadosomatic index in group A3 was higher than that in group B3 from February through April. The highest plasma concentrations of estradiol in group A3 occurred in November and December and exceeded those in group B3. Plasma concentrations of testosterone in group A3 were highest in December and tended to be higher in October and April than in other months. There was no difference in plasma testosterone between groups A3 and B3 except in March when concentrations of this androgen were extremely high in group B3. Ovulation occurred earlier in B regime fish in comparison to that of A regime fish. However, egg quality of fish from regime B was lower than that of fish from regime A. We conclude that the condensed photothermal cycle is not an entirely effective method of inducing out-of-season spawning in female yellow perch. These data suggest that although the compression of the photothermal cycle slightly accelerated spawning, it also caused disturbances in patterns and levels of plasma steroids, diminished ovarian and hepatic growth, and reduced the quality of eggs. Thus, temperature and/or photoperiod may have only a modifying effect on the onset of perch spawning, but these environmental cues seem to markedly influence earlier stages of gonadal growth and development. 相似文献
9.
T. Kirisits H. Konrad E. Halmschlager C. Stauffer M. J. Wingfield D. B. Chhetri 《Forest Pathology》2007,37(1):40-50
During a recent survey of forest tree diseases in Western and Central Bhutan, Sirococcus shoot blight and an associated Sirococcus sp. were found on saplings and mature trees of Eastern Himalayan spruce (Picea spinulosa). Based on morphological characteristics and DNA sequence comparisons of the ITS region of the rDNA operon, representative isolates from Bhutan were unequivocally identified as Sirococcus conigenus. The DNA sequence data also showed that these isolates belong to the P group of S. conigenus. To our best knowledge, this is the first report of Sirococcus shoot blight from the Himalayas or any other part of Asia. Sirococcus conigenus does not appear to cause dramatic damage at the moment, but this fungus has the potential to cause severe disease problems on P. spinulosa in Bhutan. 相似文献
10.
Konrad Dabrowski 《Aquaculture (Amsterdam, Netherlands)》1977,12(1):63-73
The study was aimed at determining the optimal level of protein in a casein diet for grass carp. There was a linear relationship between the percentage of protein in the diet and the increase in fish protein and weight up to optimal levels of 41 and 43%, respectively. No further increase in fish protein or weight was noted with diets containing up to 64% of protein. However, if the optimal level was defined by the parabolic curve with the formula y = 36.21 + 6.238x ? 0.0593x2, it would equal 52.6 ± 1.93%. Net protein utilization (NPU) values for experimental diets were obtained using a formula which took the maintenance nitrogen metabolism on a non-protein diet into consideration. This NPU formula was related to the length of the experiment, difference in the weight of fish at the beginning of the experiment, and growth of fish fed protein diets. Both protein efficiency ratio (PER) and NPU decreased with the increase in protein content of the diets according to the formulae y = 1.966?0.018x and , respectively. 相似文献