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91.
Masaki?HaradaEmail author Kohei?Komatsu Tomoyuki?Hayashi Masahiko?Karube 《Journal of Wood Science》2004,50(5):450-454
A wooden lattice floor with high stiffness and damping capacity has been developed to solve noise problems in wooden apartment houses. The lattice floor consisted of Douglas fir glulam beams with inserted steel plate joints and drift pins. To examine the structural performance of the floor, dynamic excitation and static loading tests were conducted on the full size floor. The first and second order resonance frequencies of the floor were 13.5Hz and 27.0Hz, respectively. These frequencies are similar to the peak frequency of a conventional wooden floor and the combined floor fabricated from glued laminated timber and iron. The maximum static load of the floor was 127kN. The apparent flexural rigidity was less than half the value of several floors studied in the past. However, it is considered that the stiffness is improved by constructing panels and this floor has almost equivalent performance. Relative deflection was not affected by the loading history.Part of this study was presented at the International Wood Engineering Conference, New Orleans, October 1996. 相似文献
92.
Muneto?HirobeEmail author John?Sabang Balram K.?Bhatta Hiroshi?Takeda 《Journal of Forest Research》2004,9(4):347-354
The effects of tree species on the dynamics of nutrient transformations during leaf-litter decomposition are not well understood
in tropical rain forests. To examine differences in the dynamics of C, nutrients, and organic constituents during decomposition
among tree species, the leaf-litter decomposition of 15 trees was assessed using a litter-bag method in a lowland tropical
rain forest in Sarawak. The dynamics of C was parallel to that of weight loss. The dynamics of nutrients were grouped into
three patterns. The dynamics of K was characterized by a high leaching loss in the initial stages, and that of Ca and Mg generally
showed a gradual decrease over the course of decomposition. The dynamics of N and P showed highly different patterns with
the weight loss, and was characterized by relatively higher remaining mass at the end of the experiment. The variations or
exceptions of nutrient dynamics among tree species were considered to be related to the initial concentration of each nutrient.
For the dynamics of organic constituents, water-soluble carbohydrates disappeared quickly at the initial stages, and acid-soluble
carbohydrates were the second fastest decomposing fraction; the decomposition of acid-insoluble residue (AIS) was the slowest.
The release of limiting nutrients (N and P) generally followed the disappearance of AIS, but was independent of the disappearance
of AIS when the initial concentrations of these nutrients were very low. 相似文献
93.
Chan-Woo?Park Won-Jae?Youe Song-Yi?Han Yong?Sik?KimEmail author Seung-Hwan?LeeEmail author 《Wood Science and Technology》2017,51(1):151-163
Lignin is a potential precursor for low-cost carbon fiber production, but it is difficult to spin and spool lignin because of its complex and interconnected molecular structure. This disadvantage can be overcome by introducing g-polyacrylonitrile (PAN) to lignin. However, the resulting copolymer is insoluble in common organic solvents. In this study, kraft lignin (KL)-g-polyacrylonitrile copolymers with different KL/PAN proportions were prepared via atom transfer radical polymerization (ATRP) method and their solubility in ionic liquids (ILs) was investigated at different temperatures. 1-Ethyl-3-methylimidazolium acetate ([EMIM]Ac), 1,3-dimethylimidazolium methyl sulfate ([MMIM]MeSO4), 1-butyl-3-methylimidazolium chloride ([BMIM]Cl), and 1-butyl-3-methylimidazolium bromide ([BMIM]Br) were used as the ILs. At all investigated temperatures, the highest solubility of KL-g-PAN was observed in [EMIM]Ac, with the order of [MMIM]MeSO4 > BMIM]Br > [BMIM]Cl. The solubility in BMIM]Br and [BMIM]Cl was remarkably low, reaching values of less than 4 g/Kg. The viscosity and surface tension of the KL-g-PAN/[EMIM]Ac solution increased and decreased, respectively, with increasing amounts of PAN and further by the addition of dimethylformamide (DMF) to the solution. FTIR spectra of KL-g-PAN copolymers before and after dissolution suggested that PAN was partially depolymerized from the copolymer during the dissolution process. 相似文献
94.
Li Xian-jun Zhang Bi-guang Li Wen-jun 《中国林学(英文版)》2005,7(2):47-51
In order to analyze the effects of the temperature gradient on moisture movement during the highly intensive microwave-vacuum drying, thermal diffusion of Masson pine wood was studied. Internal distribution of temperature and moisture in Masson pine samples sealed by epoxy resin and aluminum foil was measured, the magnitude of thermal diffusion was calculated and the influencing factors of thermal diffusion were discussed. Results showed that with the transfer of moisture toward the low temperature in wood, opposite temperature and moisture gradient occurred. The initial moisture content (MC), temperature and time are important factors affecting this process; the thermal diffusion is in proportion to wood temperature, its initial moisture and time. The temperature and distance from hot surface is strongly linearly correlated, and the relationship between MCs at different locations and distance from the hot end surface changes from logarithmically form to exponentially form with the increase in experimental time. 相似文献
95.
Christian?P.?Andersen Ivan?Nikolov Petia?Nikolova Rainer?Matyssek Karl-Heinz?H?berleEmail author 《European Journal of Forest Research》2005,124(3):155-163
Seasonal fluxes of CO2 from soil and the contribution of autotrophic (root + mycorrhizal) to total soil respiration (SR) were estimated for a mixed
stand of European beech (Fagus sylvatica) and Norway spruce (Picea abies) in Central Europe. Mature trees of each species were girdled in August 2002 to eliminate carbohydrate allocation to roots.
SR was measured at distances of 0.5, 1.0, and 1.5/2.0 m from the bole of each tree at 1–2 weeks intervals throughout the fall
of 2002 and monthly during the spring and summer of 2003. The contribution of roots and mycorrhizae to total SR was estimated
by the decrease in SR compared to ungirdled control trees to account for seasonal patterns evident in controls. SR decreased
with soil temperature in the fall 2002 and increased again in 2003 as soil warmed. During most of the study period, SR was
strongly related to soil temperature. During the dry summer of 2003, however, SR appeared to be uncoupled from temperature
and was strongly related to soil water content (SWC). Mean rates of SR in beech and spruce control plots as well as root densities
did not show a clear pattern with distance from the bole. SR decreased to levels below controls in beech within a few days
after girdling, whereas spruce did not show a significant decrease until October 2002, 6 weeks after girdling. In both beech
and spruce, decreased SR in response to girdling was greatest closest to the bole, possibly reflecting increased mycorrhizal
activity close to the bole. Autotrophic respiration was estimated in beech to be as much as 50% of the total SR in the stand.
The contribution of autotrophic respiration was less certain for spruce, although close to the bole, the autotrophic fraction
may contribute to total SR as much as in beech. The large fraction of autotrophic respiration in total SR requires better
understanding of tree level stresses that affect carbon allocation below ground. 相似文献
96.
Cotton?K.?RandallEmail author Mary?L.?Duryea Susan?W.?Vince R.?Jeffery English 《New Forests》2005,29(3):245-260
Sprouting can be an important mechanism of regeneration in harvested cypress (Taxodium sp.) wetlands; however, limited information exists on factors influencing sprouting. We examined the influence of harvesting practices, tree size, and site conditions on stump sprouting in eight pondcypress (Taxodium distichum var. nutans (Ait.) Sweet) wetlands in Florida, USA. Stumps were cut at three heights: 20 cm below high water level, at high water, and 40 cm above high water. Half of each site was harvested using a sawhead feller and the other half using shearhead. We monitored sprouting for 2 years post-harvest. Stump height affected first year sprouting, but the effect disappeared during year 2. Felling equipment did not affect sprouting; however, the shearhead caused greater stump damage. Sprouting declined with increasing parent tree size; percentage of stumps with sprouts after 2 years was 68% for trees 10–14 cm dbh and 28% for trees 20–24 cm dbh. Stump sprouting ranged among sites from 23 to 54% after 2 years. Results indicate that sprouting may be an important, but inadequate, form of regeneration. At sites with short hydroperiods, dense understories, and/or predominance of trees greater than 20 cm dbh, reduced sprouting may occur, and planting seedlings may be beneficial. 相似文献
97.
Y Gr?hn 《Research in veterinary science》1985,39(1):24-28
Propionate utilisation by the liver in spontaneously ketotic dairy cows was investigated by determining blood glucose levels after an intravenous sodium propionate load (2.5 mmol kg-1). In addition, blood ketone body concentrations were measured after propionate loading. Cows were divided into three groups (control, mildly ketotic and severely ketotic) by their blood acetoacetate concentrations. Plasma glucose concentrations increased significantly after sodium propionate injection in all three groups (P less than 0.05). The maximum glucose concentration occurred earlier in the control group than in the ketotic groups. Changes in glucose concentrations following propionate loading of control and ketotic cows differed significantly at 20 minutes and beyond. Differences in the change in glucose concentration between mildly ketotic and severely ketotic cows were not significant. Acetoacetate concentration was significantly decreased at five minutes and beyond after the injection in ketotic cows, whereas beta-hydroxybutyrate concentration decreased more slowly. A decrease in beta-hydroxybutyrate concentration was significant at 40 minutes and beyond in the severely ketotic group and at 10 minutes and beyond in the mildly ketotic group after loading. 相似文献
98.
Effect of shrimp head protein hydrolysates on the state of water and denaturation of fish myofibrils during dehydration 总被引:1,自引:0,他引:1
Yaowalux?Ruttanapornvareesakul Misako?Ikeda Kenji?HaraEmail author Kazufumi?Osako Orawan?Kongpun Yukinori?Nozaki 《Fisheries Science》2005,71(1):220-228
ABSTRACT: To utilize fisheries waste products as food materials with functional properties, shrimp head protein hydrolysates (SHPH) from three species of shrimp, that is, Northern pink shrimp ( Pandalus eous ), Endeavour shrimp ( Metapenaeus endeavouri ) and Black tiger shrimp ( Penaeus monodon ), were produced by enzymatic hydrolysis using endopeptidase derived from Bacillus subtilis and exopeptidase derived from Aspergillus oryzae at a level of 0.1% (w/w). SHPH were rich in protein (90–91%) and amino acids (71–84%) but little fat (0.01–0.02%). The average molecular weight of SHPH was 300–1400. The effect of 5% SHPH (dry basis) addition on the state of water and denaturation of lizard fish myofibrils (Mf) during the dehydration process was evaluated by the desorption isotherm and the Ca-ATPase activity, and compared with the effect of sodium glutamate (Na-Glu). SHPH decreased the water activity and the Ca-ATPase inactivation, and increased monolayer sorbed water and multilayer sorbed water of Mf, although these effects of SHPH were smaller than those of Na-Glu. These findings suggest that the SHPH suppressed dehydration-induced denaturation of myofibrillar protein by stabilizing the hydrated water surrounding myofibrils. 相似文献
99.
Daylily rust fungus, Puccinia hemerocallidis, was proven to host-alternate between a wild daylily, Hemerocallis fulva var. longituba, and a patrinia, Patrinia villosa. No proof was obtained for the early belief that the fungus is pathogenic to plantainlilies, Hosta species, in addition to daylilies, Hemerocallis species. The fungus seems to alternate regularly between daylilies and patrinias in Japan because most daylily species are deciduous, and a vegetatively reproducing stage of the pathogen does not seem capable of successfully overwintering free of the living host tissue. 相似文献
100.
The process of colonization of Ascaris lumbricoides eggs by the fungus Verticillium chlamydosporium was studied by scanning electron microscopy. The preparations were made by fractionation of egg suspension exposed to the fungus for four days and frozen in liquid nitrogen according to St?rba and Milácek (1986). Ovicidal fungus forms an abundant ramifying mycelial network in the area between the eggs. However, egg-shells are penetrated only by some hyphae without any penetration organs produced (simple hyphal penetration). In a liquid medium, after penetration, hyphae inside the eggs rapidly grow among inner structures of egg-shells and on the surface of developing larvae. In the next phase, hyphae colonize the developing larva. The eggs attacked by this fungus remain morphologically unchanged for a long time except the sites of penetration. Verticillium chlamydosporium is a fungus with unique ovicidal properties. It colonizes the eggs of Ascaris lumbricoides at all stages of embryo development and also attacks larvae inside the eggs. 相似文献