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11.
Aerial spray applications of the herbicide glyphosate were made over a forest canopy under various meteorological conditions. A ‘Thru Valve Boom’ dispersal system carried by a Cessna 188 fixed-wing aircraft flying at 49 m s?1 was used to generate an aqueous spray cloud with a volume median diameter of 150 μm. Glyphosate deposits from multiple overlaid crosswind line sources released at 10 m above ground level were measured on ground sheets and artificial foliage at downwind distances between 50 and 400 m. Trials were conducted in stable, neutral and unstable atmospheric boundary layers with average wind speeds between 2·2 and 5·7 m s?1 and vertical intensities of turbulence between 0·07 and 0·16. Linear regression lines fitted to logarithmically transformed measurements and downwind distances (x) gave statistically significant correlation coefficients (P = 0·01), and were compared by ANOVA. Glyphosate deposits on ground sheets and artificial foliage were attenuated at rates inversely proportional to x to the power 1·7-4·3. Regression line comparison showed that, in general, deposits on ground sheets decreased with increasing wind speed and intensity of turbulence, and some statistically significant differences were found in slopes and elevations of regression lines from different trials. However, deposits at the 50-m station increased with wind speed due to the large-drop cloud component. Regression line comparison for deposits on artificial foliage showed that, in general, they were highest in the intermediate wind speed-neutral stability case and similar in the high wind speed-unstable and low wind speed-stable boundary layers, although deposits at the 50-m station also increased with wind speed.  相似文献   
12.
Culture fluids from Marek's disease (MD) lymphoblastoid cell lines have suppressive activity against normal and mitogen-stimulated chicken spleen and bursal cells and also against the homologous cell lines. Suppressive activity was also present in supernatants from spleen cells infected in vitro with MD virus. The suppressor factor from MD cell lines was non-sedimentable, trypsin sensitive, heat resistant and partially dialysable. Preliminary studies suggest it has a molecular weight of 20,000 daltons. Studies were also conducted on the effect of the prostaglandin inhibitors indomethacin and aspirin on the production and action of the suppressor factor. At low concentrations they have a stimulatory effect on the cell lines suggesting that they inhibit the effects of suppressor factor; however only small amounts of prostaglandin E2 were present in supernatants. Evidence was obtained that the suppressor factor may act indirectly by stimulating the production of prostaglandin by spleen cell cultures. The role of a suppressor factor in the immunosuppression observed in MD is discussed.  相似文献   
13.
Studies on the mechanism of vaccinal immunity to Marek''s disease   总被引:1,自引:0,他引:1  
Current knowledge of the nature of the antigens and of the host immune responses in vaccinal immunity to Marek's disease is reviewed. It is suggested that a two-step mechanism of resistance operates. The first step involves humoral and cell-mediated responses directed against viral antigens; the second step occurs after challenge with Marek's disease virus and consists of cellmediated responses directed against tumour cells.  相似文献   
14.
15.
Separate groups of goats were used to determine drug depletion patterns in serum (n=10), tissue (n=20) and milk (n=8) following a single intramuscular (i.m.) dose of 20 mg/kg of a long-acting oxytetracycline (OTC) formulation (Liquamycin LA-200). Milk residues were also determined following a subcutaneous (s.c.) administration of the same product at the same dose. Serum samples were taken for 24 h post-treatment and tissues (fat, liver, kidney, muscle and injection site) collected at 4, 7, 14, 21 and 28 days following injection. Milk from lactating goats was collected every 12 h for 8 days following both the i.m. and s.c. treatments utilizing an intervening 5-week washout period. Residues in serum and tissue were measured using a microbial inhibition assay, while milk residues were measured using both a microbial inhibition assay and a validated HPLC method. The serum pharmacokinetic parameters of OTC in goats were determined, with a mean AUC=67.4 microg h/mL, mean terminal half-life=14.4 h, and apparent clearance=0.33 L/kg h. Tissue half-lives could not be determined with confidence because the collection times provided only two points at which residues could be measured for most tissues. Oxytetracycline residues in all goat tissue samples measured less then cattle tissue tolerance by 96 h postdosing. One-compartment model describing milk depletion data for i.m. and s.c. dosing had terminal slope half-lives of 20.1 and 36.1 h, respectively. By 96 h post-treatment none of the milk samples contained OTC residues in excess of the cattle milk tolerance (0.3 p.p.m.). For both milk and tissue, the upper-bound 99% confidence intervals for the samples taken from goats 96 h postdosing were lower than approved cow milk and tissue tolerances.  相似文献   
16.
Two cases of fatal cryptococcosis are described, one of Cryptococcus neoformans infection in a Gilbert's potoroo (Potorous gilbertii) and one of Cryptococcus gattii infection in a long-nosed potoroo (Potorous tridactylus). The diagnoses were confirmed by culture and specific immunohistochemistry, respectively. The long-nosed potoroo tested positive using the latex cryptococcal antigen test (LCAT), whereas the Gilbert's potoroo had a negative LCAT result despite having advanced disease of some duration. In both cases, the clinical presentation was a progressive neurologic disease associated with a central nervous system infection. Pulmonary infection was also observed in the long-nosed potoroo. Specific treatment with antifungal agents was unsuccessful in the long-nosed potoroo.  相似文献   
17.
The ecology of cytopathic expression of bovine coronavirus (BCV) in HRT-18 cells was analyzed within virus-induced plaques by scanning electron microscopy. Virus replication was cytocidal for many HRT-18 cells, a function enhanced in the presence of trypsin. A monolayer of cells remained that imparted a characteristic turbidity to the plaque. These structurally normal, lysis-resistant cells did not stain with fluorescent antibodies specific for BCV antigens, failed to adsorb virus particles or mouse erythrocytes in contrast to the susceptible cells. The survival of cells in the plaque interior reflects a non-productively infected population with evidence of viral persistence.  相似文献   
18.

Background

Population characteristics and outcome of cats with arterial thromboembolism (ATE) managed in general practice (GP) have been poorly described.

Hypothesis

Cats with ATE presenting to GP are usually euthanized at presentation, but survival times >1 year are possible.

Animals

Cats with ATE managed by 3 GP clinics in the United Kingdom.

Methods

Records of cases presenting to GP over a 98‐month period (2004–2012) were reviewed. Cats with an antemortem diagnosis of limb ATE were included. Outcome information was obtained.

Results

Over 98 months, 250 cats were identified with ATE. Prevalence was approximately 0.3%. At presentation, 153 cats (61.2%) were euthanized, with 68/97 (70.1%) of the remaining cats (27.2% of the total population) surviving >24 hours after presentation. Of these, 30/68 (44.1%) survived for at least 7 days. Hypothermia (HR, 1.44; 95% CI, 1.002–2.07; P = .049) and management by Clinic 2 (HR, 5.53; 95% CI, 1.23–24.8; P = .026) were independent predictors of 24‐hour euthanasia or death. For cats surviving >24 hours, hypothermia (HR, 2.25; 95% CI, 1.12–4.48; P = .021) and failure to receive aspirin, clopidogrel, or both (HR, 8.26; 95% CI, 1.39–50; P = .001) were independent predictors of euthanasia or death within 7 days. For cats that survived ≥7 days, median survival time was 94 (95% CI, 42–164) days, with 6 cats alive 1 year after presentation.

Conclusions

Although 153/250 cats were euthanized at presentation, 6 cats survived >12 months. No factors were identified that predicted euthanasia on presentation.  相似文献   
19.
Open surgical ovariohysterectomy in the mare provides limited visualisation and a long surgical incision. Laparoscopically‐assisted ovariohysterectomy has been performed by the authors in 3 mares with pyometra. This approach does seem to offset some of these disadvantages.  相似文献   
20.
The tilapia species occurring in the lower Nile are Sarotherodon niloticus, S. aureus, S. galiaeus and Tilapia zillii. The distinguishing characteristics between the previously confused S. niloticus and S. aureus are summarised; from these there is no evidence of hybridization of the two species in natural populations in Egypt. The scales are used to estimate the growth rates of tilapia species in two coastal lakes and in both, S. niloticus grows faster than S. aureus after the first year. The possible factors causing the growth checks on the scales are considered.

The spawning season of S. niloticus appears to attain a discrete peak in April–May, whilst the spawning season of S. aureus extends from May to September with at least two actual spawnings within this period. Natural spawning cycles are compared with those observed in fish ponds.

A more extended spawning period of S. aureus may explain the reduced growth rate of the species after the first year. The spawning cycle of all species coincides with the temperature regime of the water bodies. The fecundities of S. aureus and S. niloticus are similar and are described by log F = log 1.33 + 2.23 log L, which suggests that small fishes produce more eggs per g body weight than large.

The salinity tolerance of the Nile tilapia can be ranked as T. zillii > S. galilaeus > S. aureus > S. niloticus. Evidence on chronic and acute effects of salinity are reviewed and upper estimates for salinities giving unimpeded growth are deduced as being, T. zillii 29‰, S. galilaeus 15–20‰, S. areus 10–15‰ and S. niloticus 5–10‰.  相似文献   

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