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981.
Transgenically enhanced expression of indole-3-acetic Acid confers hypervirulence to plant pathogens
ABSTRACT Fusarium oxysporum and F. arthrosporioides, pathogenic on Orobanche aegyptiaca, were transformed with two genes of the indole-3-acetamide (IAM) pathway leading to indole-3-acetic acid (IAA) to attempt to enhance virulence. Transgenic F. oxysporum lines containing both the tryptophan-2-monooxyngenase (iaaM) and indole-3-acetamide hydrolase (iaaH) genes produced significantly more IAA than the wild type. IAM accumulated in culture extracts of F. oxysporum containing iaaM alone. F. arthrosporioides containing only iaaM accumulated IAM and an unidentified indole. Some transformants of F. oxysporum expressing only the iaaM gene also produced more IAA than the wild type. Sub-threshold levels (that barely infect Orobanche) of transgenic F. oxysporum expressing both genes and of F. arthrosporioides expressing iaaM were more effective in suppressing the number and size of Orobanche shoots than the wild type on tomato plants grown in soil mixed with Orobanche seed. Stimulating an auxin imbalance enhanced pathogen virulence by affecting the host in a manner similar to low doses of auxin herbicides such as 2,4-dichlorophenoxy acetic acid. 相似文献
982.
Parasitic Orobanche spp are major constraints to vegetable crop production in the Mediterranean basin (to eastern Europe) and in localized places in India, China and the USA. Transgenic target-site herbicide resistance (eg, to acetolactate synthase inhibitors) allows for movement of unmetabolized herbicide through the crop to the photosynthate sink in the parasite, as well as through the soil. We report the successful engineering of a mutant acetolactate synthase (ALS) gene into carrot, allowing control of broomrape already in heterozygotes of the first back-crossed generation, by imazapyr, an imidazolinone ALS inhibitor. It is expected that homozygotes will have higher levels of resistance. 相似文献
983.
The relationship between dose for each of four biorational insecticides (pyrethrins, neem extract, capsiacin extract, insecticidal soap) and mortality of the green peach aphid (Myzus persicae) was determined using a laboratory bioassay. These insecticides were toxic to aphids and paired mixtures of the insecticides provided synergistic activity as measured by aphid mortality under the laboratory bioassay conditions. Capsiacin extracts were found to provide low levels of mortality alone but acted synergistically in mixtures with the other insecticides and provided higher than expected levels of mortality. Activity as determined in the laboratory for each insecticide was not evident under field-use conditions in five separate experiments. Under field conditions and using common application methods, these insecticides did not provide significant levels of control of aphids. 相似文献
984.
985.
986.
Investigation of relative rates of solvent and solute penetration through protective glove materials
Adam C. Watkinson Keith R. Brain Kenneth A. Walters Jonathan Hadgraft 《Pest management science》1993,39(3):251-256
Pesticides are often formulated as a concentrate in volatile organic solvents. The most important means of preventing the contamination of workers using the concentrate is by the use of protective clothing, particularly gloves. The influence of formulation solvent on solute permeation rates across selected protective glove materials has been investigated. In one of the cases studied, the solute penetrated the glove material appreciably faster than the formulation solvent. This result, therefore, questions the manner in which gloves are often selected for protection against pesticide formulations (by selecting the glove that offers the best protection against the formulation solvent rather than the active ingredient). Although this is a preliminary study, it is recommended that, to gain the maximum protective effect, all selected gloves are tested using the formulation of choice and that the permeation of all components of the formulation is monitored and reported. It may, therefore, be necessary for glove and pesticide manufacturers to re-examine the way in which these tests are carried out and the processes of product selection used. 相似文献
987.
It is important to be able to predict the absorption of materials through the skin, particularly if there are toxicological implications. However, for pesticides which are known to be toxic, there are ethical considerations in conducting in-vivo human evaluations of percutaneous absorption. It would therefore be desirable to obtain an indication of the amount of pesticide that can penetrate the skin from a simple knowledge of its physico-chemical properties. It has been shown that the rate of penetration of a range of drugs through intact skin can be estimated from parameters such as partition coefficient, molecular size and solubility. These parameters will be equally applicable to pesticides and the relevant mathematical expressions are discussed. 相似文献
988.
The rate of gas interchange between the atmosphere within a freight container and the external air has an important influence on the effectiveness of in-container fumigation. When a container is exposed to the wind or is in motion, the rate of gas interchange may be much greater than that under static conditions. The effect of motion or wind on gas interchange was studied by observing gas loss from freight containers, both empty and loaded with rice, while stationary and while being transported by rail. The gas interchange rate was determined by measuring the rate of loss from the containers of either a combination of a fumigant, methyl bromide, and a relatively inert tracer gas, carbon monoxide, or of carbon monoxide alone. In loaded containers the difference between the loss rate constants of methyl bromide and carbon monoxide (0.29.0.03d?1) was within the range expected for the reaction of methyl bromide with rice. After allowing for gas loss caused by changes in temperature and pressure, the component of the interchange rate constant attributable to air motion was found to be proportional to gas-tightness as measured by a steady-state pressure test, and also to the relative air speed over the container. Under conditions of varying wind and train speed, the fraction of the initial concentration of gas remaining was found to be an exponential function of wind run past the container. When wind effects were not important, it was found to be an exponential function of distance travelled. 相似文献
989.
Jonathan Yuen Eva Twengström Roland Sigvald 《European journal of plant pathology / European Foundation for Plant Pathology》1996,102(9):847-854
The use of logistic regression is proposed as a method of verifying and calibrating disease risk algorithms. The logistic regression model calculates the log of the odds of a binary outcome as a function of a linear combination of predictors. The resulting model assumes a multiplicative (relative) relationship between the different risk factors. Computer programs for performing logistic regression produce both estimates and standard errors, thus permitting the evaluation of the importance of different predictive variables. The use of receiver operating characteristic (ROC) curves is also proposed as a means of comparing different algorithms. An example is presented using data on Sclerotinia stem rot in oil seed rape, caused bySclerotinia sclerotiorum. 相似文献
990.
Sarah E. Perfect Jonathan R. Green Richard J. O''Connell 《European journal of plant pathology / European Foundation for Plant Pathology》2001,107(8):813-819
During infection of bean (Phaseolus vulgaris), the hemibiotrophic anthracnose pathogen, Colletotrichum lindemuthianum, initially produces biotrophic primary hyphae that are large-diameter and entirely intracellular, followed by necrotrophic secondary hyphae that are narrower and either intercellular or intracellular. In the present study, transmission electron microscopy of infected tissues prepared by high-pressure freezing and freeze-substitution showed that secondary hyphae have much thinner cell walls (25–40 nm) than primary hyphae (100–130 nm) and are not surrounded by an extracellular matrix. Immunofluorescence labelling with a panel of monoclonal antibodies showed that glycoproteins which are present on conidia, germ-tubes, appressoria, primary hyphae and mycelium grown in vitro are absent from the surface of secondary hyphae. Chitin, detected with the lectin wheat germ agglutinin, was the only surface component shared by secondary hyphae and the other fungal cell types. The results suggest that the fungal cell surface becomes modified during necrotrophic growth, with none of the glycoproteins associated with earlier stages of the infection process being produced. 相似文献