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排序方式: 共有434条查询结果,搜索用时 15 毫秒
41.
Malcolm J. Hawkesford Andrea Schneider Ann R. Belcher David T. Clarkson 《植物养料与土壤学杂志》1995,158(1):55-57
The regulation of enzymes involved in sulphate assimilation in plants has been investigated. Extractable activity of ATP sulphurylase (the first enzyme of the assimilatory pathway) has been shown to be regulated by sulphate availability and O-acctylserine (OAS) supply. OAS addition to the medium increased extractable activity and was able, at least partially, to overcome the repression of extraclable activity observed by supply of sulphate and cysteine. Cysteine synthase, the final enzyme of the cysteine biosynthetic pathway, was not regulated under these conditions. 相似文献
42.
The role played by organic chemistry in the pharmaceutical industry continues to be one of the main drivers in the drug discovery process. However, the precise nature of that role is undergoing a visible change, not only because of the new synthetic methods and technologies now available to the synthetic and medicinal chemist, but also in several key areas, particularly in drug metabolism and chemical toxicology, as chemists deal with the ever more rapid turnaround of testing data that influences their day-to-day decisions. 相似文献
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44.
Pelejero C Calvo E McCulloch MT Marshall JF Gagan MK Lough JM Opdyke BN 《Science (New York, N.Y.)》2005,309(5744):2204-2207
The oceans are becoming more acidic due to absorption of anthropogenic carbon dioxide from the atmosphere. The impact of ocean acidification on marine ecosystems is unclear, but it will likely depend on species adaptability and the rate of change of seawater pH relative to its natural variability. To constrain the natural variability in reef-water pH, we measured boron isotopic compositions in a approximately 300-year-old massive Porites coral from the southwestern Pacific. Large variations in pH are found over approximately 50-year cycles that covary with the Interdecadal Pacific Oscillation of ocean-atmosphere anomalies, suggesting that natural pH cycles can modulate the impact of ocean acidification on coral reef ecosystems. 相似文献
45.
Jinxiu Zhang Allen G. Xue Malcolm J. Morrison Yao Meng 《European journal of plant pathology / European Foundation for Plant Pathology》2011,131(1):95-102
This study evaluated the impact of time between the application of cell suspensions or cell-free filtrates of Bacillus subtilis strains SB01 or SB24 on soybean plants under field conditions and inoculation with Sclerotinia sclerotiorum on their effectiveness for suppression of S. sclerotiorum. The results showed that the cell suspensions of two strains provided greater effectiveness than the cell-free filtrates,
but the suppression effectiveness decreased as the time between application in the field and S. sclerotiorum inoculation increased. The B. subtilis cell suspensions applied on soybean leaves for up to 10 days under field conditions were able to provide a significant (P < 0.01) reduction in disease severity by approximately 20–90% at 5 days after the S. sclerotiorum inoculation. When rated 15 days after S. sclerotiorum inoculation, plants treated with bacterial cells for ≤6 days reduced Sclerotinia stem rot severity by 15–70%. Most effectiveness was provided by the cell suspensions present on soybean leaves for <3 days
under field conditions, which significantly (P < 0.01) reduced disease severity by 40–70% over 15 days. In comparison, the cell-free filtrates remaining on leaves for <6 days
significantly (P < 0.01) reduced disease severity during the first 5 days after the inoculation, while the best cell-free filtrate treatments
were those with ≤1-day intervals, which significantly (P < 0.01) reduced disease severity by 10–40% during 15 days after the inoculation. The effectiveness of B. subtilis was reduced when it rained after application. 相似文献
46.
47.
Arsenate Displacement from Fly Ash in Amended Soils 总被引:1,自引:0,他引:1
Qafoku Nikolla P. Kukier Urszula Sumner Malcolm E. Miller William P. Radcliffe David E. 《Water, air, and soil pollution》1999,114(1-2):185-198
Arsenic (As) is the biggest environment contaminant in most of the soils where fly ash is applied. Usually, it is not mobile and strongly adsorbed on to soil particles. However, in gypsum and phosphorus amended soils As may be much more mobile. A study in repacked columns was conducted to determine whether or not As becomes mobile when Ca(H2PO4)2and CaSO4are used as leaching solutions, and to compare the competitive interactions between PO4-AsO4and SO4-AsO4. Arsenic concentration in leachate was found to be approximately ten times greater when Ca(H2PO4)2was used to leach the columns as compared to CaSO4. A maximum concentration of 800 μg As L-1was found in the leachate in this case, which is much higher than the groundwater limit of 50 μg L-1for drinking water established by the United States Environmental Protection Agency. In fly ash, the portion of arsenate non-specifically adsorbed is believed to be much lower than that of specifically adsorbed. Sulfate anions were able to displace only non-specifically adsorbed arsenate. In this case the concentration of As in leachate was found to be within acceptable limits. On the other hand, phosphate can compete with arsenate for all available adsorption sites, non-specific and specific. Phosphate displacement of both forms of arsenates increases As mobility in both control and fly ash treatments. 相似文献
48.
49.
J. Malcolm Baker 《Canadian journal of veterinary research》1954,18(10):373-374
50.
Derek R. Clifford Peter Gendle Margaret E. Holgate Malcolm Lulham 《Pest management science》1981,12(5):509-514
The eradicant activities of 24 nitrogen-containing preparations, comprising primary, secondary or tertiary amines, amine acetates, diamines, amine oxides or quaternary ammonium salts, were assessed in trials with potted dormant apple rootstocks, heavily infected with the powdery mildew fungus Podosphaera leucotricha. The surfactants consisted of mixtures in which C12/C14 or C16/C18 alkyl or alkenyl compounds predominated. Of the amine acetates (at 50g litre?1), only the formulation containing C12/C14 primary amine acctates was considered worthy of further evaluation. Some amine oxides and quaternary ammonium compounds (at 35 g litre?1) were good eradicants and were as effective as ‘PP222’ a (nonylphenol-ethoxylate mixture) which was included for comparison. All the compounds showing good activity contained one C12/C14 alkyl group whereas C16/C18 compounds, whether saturated or unsaturated, were relatively inactive. In a field trial, C12/C14 (dimethyl) amine oxide, C12/C14bis (2-hydroxyethyl) amine oxide, and C12/C14 amine acetate (35 g litre?1) greatly reduced the amount of primary mildew on trees that were previously heavily infected, but there were signs that the fruit yield was reduced. 相似文献