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981.
982.
983.
Influence of long-term fertilization with farmyard manure on soil organic matter: Characteristics of particle-size fractions 总被引:10,自引:0,他引:10
Summary The influence of more than 100 years of fertilization with farmyard manure on soil organic matter in comparison to unfertilized soil was studied in particle-size fractions using elemental (C and N) analyses and pyrolysis-field ionization mass spectrometry. Distinct differences in C and N concentrations and distribution and in the quality of organic matter between the size fractions and the fertilization treatments were observed. Clay-associated C and N were relatively higher in the unfertilized treatment, whereas the application of farmyard manure preferentially increased soil organic matter associated with the fine and medium silt fractions. Pyrolysis-field ionization mass spectrometry of soil fractions <20 m showed increasing values for lignin monomers and dimers and fatty acids with larger equivalent diameters, whereas the proportion of N compounds, mono- and polysaccharides and phenolics decreased in the larger size fractions. Sand fractions were particularly rich in lignin fragments, mono- and polysaccharides, and alkanes/alkenes. These relationships seemed to be independent of management practices. In the same size fractions of the different treatments, however, a higher relative abundance of N-compounds, mono- and polysaccharides, phenolics, lignin monomers, and alkanes/alkenes was observed in the unfertilized variant. Lignin dimers and fatty acids were more abundant in the farmyard manure treatment. Both trends together imply that soil enrichment in organic matter due to the application of farmyard manure largely reflects an increase in lignin building blocks and partly reflects an increase in lipids such as fatty acids in the silt fractions. Therefore these constituents are of particular importance in assessing the positive effects of farmyard manure on soil fertility. 相似文献
984.
985.
986.
土壤水分状况和质地对稻田N2O 排放的影响 总被引:34,自引:0,他引:34
1994年中国科学院封丘生态试验站通过小区试验研究了土壤质地和水分状况对稻田N2O排放的影响。结果表明稻田N2O排放主要受土壤水分状况的影响,淹水状态下,N2O排放很少,水分落于期间N2O排放量占水稻生长期N2O排放总量的87.50%~98.65%。土壤质地显影响稻田平均N2O排放通量,砂质土壤排放的N2O显或极显高于壤质和粘质土壤,水稻生长期砂质、壤质及粘质土壤的平均N2O排放通量分别为137.63、87.54和63.6μgN2O-N/m^2.h。 相似文献
987.
988.
S. J. Kerley 《Biology and Fertility of Soils》2000,32(2):94-101
The effects of a limed soil upon root and shoot growth of white lupin (Lupinus albus L.) were investigated using soil tubes and pots. After 75 days in the soil tubes, the combined taproot and lateral root dry
weight in limed soil (2.5% CaO w/w) was significantly less than in neutral pH soil (by 57%). However, the dry weight and numbers
of cluster roots remained comparable between the treatments, demonstrating for the first time that the cluster roots respond
differently to the rest of the root system. Cluster roots accounted for 17% of the total root biomass in neutral soil, increasing
significantly to over 30% in limed soil. When grown for 43 days in pots containing soil with different additions of lime (0.5–2.5%
CaO w/w), soil citrate concentrations were higher than in the neutral pH soil treatment in all except the 2.5% lime treatment,
in which they were lower. In both experiments, shoot dry weights were lower in the presence of the limed soil compared with
those in the neutral pH soil. Although a reduction in shoot dry weight was not apparent at 21 days in the limed-soil tubes,
the initiation of fewer mainstem leaf primordia indicated a slower shoot development than occurred in the neutral soil. Plants
grown in the limed-soil tubes showed leaf yellowing and some chlorosis within 9 days. At the final harvest, the shoot phosphorus
and manganese concentrations were significantly lower in plants grown in limed soil compared with those in the neutral pH
soil, whereas the concentration of calcium was higher.
Received: 11 October 1999 相似文献
989.
Soil amidase activity in polyacrylamide-treated soils and potential activity toward common amide-containing pesticides 总被引:1,自引:0,他引:1
Jeanine L. Kay-Shoemake M. E. Watwood Robert E. Sojka Roderick D. Lentz 《Biology and Fertility of Soils》2000,31(2):183-186
Polyacrylamide (PAM) is currently used as an irrigation water additive to significantly reduce the amount of soil erosion
that occurs during furrow irrigation of crops. Elevated soil amidase activity specific toward the large PAM polymer has been
reported in PAM-treated field soils; the substrate specificity of the induced amidase is uncertain. PAM-treated and untreated
soils were assayed for their capacity to hydrolyze the amide bond in carbaryl (Sevin), diphenamid (Dymid), and naphthalene
acetamide. Based on results obtained with a soil amidase assay, there was no difference between PAM-treated and untreated
soils with respect to the rate of amide bond hydrolysis of any of the agrochemicals tested. It appears that under these assay
conditions the PAM-induced soil amidase is not active toward the amide bonds within these molecules. However, carbaryl was
hydrolyzed by a different soil amidase. To our knowledge, this is the first soil enzyme assay-based demonstration of the hydrolysis
of carbaryl by a soil amidase.
Received: 23 June 1999 相似文献
990.
Measurements of sap flow, vapour fluxes, throughfall and soil water content were conducted for 19 months in a young beech stand growing at low elevation, in the Hesse forest. This experiment is part of the Euroflux network, covering 15 representative European forests. Study of the radial variation of sap flow within tree trunks, showed a general pattern of sap flux density in relation to the depth below cambium. Among-tree variation of sap flow was also assessed, in order to determine the contribution of the different crown classes to the total stand transpiration. Stand sap flow and vapour flux, measured with eddy covariance technique, were well correlated, for half hourly as well for daily values, the ratios of the fluxes for both averaging periods being 0.77. A strong canopy coupling to the atmosphere was found, omega factor ranging between 0.05 and 0.20 relative to the windspeed. Canopy conductance variation was related to a range of environmental variables: global radiation, vapour pressure deficit, air temperature and soil water deficit. In addition to the effect of radiation and of vapour pressure deficit often found in various other tree species, here beech exhibited a strong reduction in canopy conductance when air temperature decreased below 17°C. The model of transpiration was calibrated using data measured in the Hesse forest and applied to another beech stand under mountainous conditions in the Vosges mountains (east France). Measured and modelled stand transpiration were in good agreement. 相似文献