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71.
Growth, activity of antioxidant enzymes viz. glutathione reductase (GR), superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and guaiacol peroxidase (GPX), and some metabolic processes related to ammonium metabolism were investigated in a salt‐tolerant Spatina alterniflora. In comparison to 0 mM–NaCl treatment, growth of S. alterniflora plant increased significantly at 200 mM NaCl, but was highly inhibited at 500 mM NaCl. Ammonium concentration in the leaves and roots increased 2.1–3.4 times when plants were treated with 500 mM NaCl. Under 200 mM NaCl, antioxidant‐enzyme activities increased, however, at 500 mM the antioxidant system was unable to compensate reactive oxygen species induced by NaCl. At this high level of salinity, ammonium production through nitrate reductase (NR) was inhibited, but no significant changes in the activities of glutamine synthetase (GS) or glutamate dehydrogenase (GDH) were found. We conclude that the accumulation of ammonium under high salt stress was not due to inhibition of the assimilatory activities of GS or GDH. Ammonia accumulation under high salinity may result from amino acid and protein catabolism activated by reactive oxygen species (ROS) and/or a lack of carbon skeletons to incorporate ammonium into organic molecules due to a decrease in photosynthetic activity in salt‐stressed plants.  相似文献   
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The Agricultural Health Study (www.aghealth.org) is a cohort of 89,658 pesticide applicators and their spouses from Iowa and North Carolina assembled between 1993 and 1997 to evaluate riskfactorsfor disease in ruralfarm populations. This prospective study is just now reaching sufficient maturity for analysis of many disease endpoints. Nonetheless, several analyses have already provided interesting and important leads regarding disease patterns in agricultural populations and etiologic clues for the general population. Compared to the mortality experience of the general population in the two states (adjusted for race, gender, age and calendar time), the cohort experienced a very low mortality rate overall and for many specific causes and a low rate of overall cancer incidence. A few cancers, however, appear elevated, including multiple myeloma and cancers of the lip, gallbladder, ovary, prostate, and thyroid, but numbers are small for many cancers. A study of prostate cancer found associations with exposure to several pesticides, particularly among individuals with a family history of prostate cancer. Links to pesticides and other agricultural factors have been found for injuries, retinal degeneration, and respiratory wheeze. Methodological studies have determined that information collected by interview is unbiased and reliable. A third round of interviews scheduled to begin in 2005 will collect additional information on agricultural exposures and health outcomes. The study can provide data to address many health issues in the agricultural community. The study investigators welcome collaboration with interested scientists.  相似文献   
74.
A thymic precursor to the NK T cell lineage   总被引:1,自引:0,他引:1  
CD1d-restricted autoreactive natural killer (NK1.1+) T cells function as regulatory cells in various disease conditions. Using improved tetramer tracking methodology, we identified a NK1.1- thymic precursor and followed its differentiation and emigration to tissues by direct cell transfer and in situ cell labeling studies. A major lineage expansion occurred within the thymus after positive selection and before NK receptor expression. Surprisingly, cytokine analysis of the developmental intermediates between NK and NK+ stages showed a T helper cell TH2 to TH1 conversion, suggesting that the regulatory functions of NK T cells may be developmentally controlled. These findings characterize novel thymic and postthymic developmental pathways that expand autoreactive cells and differentiate them into regulatory cells.  相似文献   
75.
In addition to six cyclopeptide alkaloids lotusines A-F, a new compound lotusine G, was isolated from the root bark of Zizyphus lotus by centrifugal partition chromatography.  相似文献   
76.
The chloroform extract of the aerial parts of Centaurea musimomum exhibited significant activity against Plasmodium falciparum. The phytochemical study of this extract gave seven native and four acetylated sesquiterpene lactones.  相似文献   
77.
ABSTRACT

The present study was performed to characterize the interaction between nitrogen (N) form and availability with respect to growth, water relations, and mineral nutrition of wild swiss chard (Beta macrocarpa Guss). Plants were cultured hydroponically with two levels of N concentrations, high-N (2.5 mM) or low-N (0.5 mM), added as nitrate (NO? 3) or ammonium (NH+ 4). At high N, growth was affected significantly by N form. If the NO? 3 medium was considered as control, the use of NH+ 4 decreased dry matter production and leaf area by ca. 35%. Use of NH+ 4 led to water economy and did not affect the nutrient content of the plant tissues. Compared to growth with high N, plants growth fell in either low- NO? 3 or low- NH+ 4 medium. In this case, the difference between the two N sources was not significant. Our results showed that the replacement of NO? 3 by NH+ 4 as the N source decreased the NO? 3 concentration in consumable leaves and increased the water use efficiency.  相似文献   
78.
Faba beans (Vicia faba L) are grown in northern Tunisia where annual rainfall approaches 1200 mm and where the soil acidity is the most limiting factor for plant growth. Aluminum (Al) and manganese (Mn) toxicities provide a hostile environment to root growth. To alleviate such a problem, farmers use selected acid-tolerant species. However, crop yields remain far below their optimal levels. Liming, a practice to eliminate acidity, has never been tried in this area before. This research aimed to evaluate the impact of lime and mineral fertilizers on root nodulation, plant uptake and yield of faba beans using a pot experiment. Treatments were combinations of two rates of calcium carbonate with three rates of superphosphate and three rates of potassium sulfate. Liming produced significantly higher number and weight of nodules on roots as well as higher nitrogen, phosphorus, and potassium contents in plant tissue. Liming also increased shoot growth and bean yield.  相似文献   
79.
Boron (B) foliar treatments (300 mg L?1 as Solubor DF) were applied at two different dates in 2006 and 2007, prior to flowering and just after fruit set, on olive (Olea europaea L.) trees with no visual symptoms of B deficiency. Leaf B level increased after the first application as compared to control (?B). After July treatment, leaf B levels in ?B and +B treated trees increased when compared to the first sampling date. Foliar B application did not significantly affect vegetative growth in either year. During the first year of study (considered as an “on year”), B application had no significant effect on several phenological characteristics including fruit set, yield oil contents and oil quality. In the second year (“off year”), B sprays improved blooming rate, which increased from 20% in ?B to 30% in + B treated trees, and olive yield, which increased by 27% in response to B.  相似文献   
80.
In order to determine the role of follicle-stimulating hormone (FSH) on the resumption of ovarian function in cows early postpartum (PP), bovine follicular fluid (FF) was used to selectively suppress concentrations of FSH. Calves were removed from all cows within 24 hr of birth. Follicular fluid that was treated with charcoal to remove steroids (15 ml; n = 14) or serum (S) from an ovariectomized cow (15 ml, n = 14) was injected i.m. twice daily from days 1 to 10 PP. Blood samples were collected before each injection and frequent samples (every 15 min for 6 hr) taken on days 5 and 10 PP. Eight cows from each group (FF and S) were slaughtered on the morning of day 11 PP and pituitaries and ovaries collected. The remaining cows (n = 6) were observed for estrus. Treatment with FF delayed follicular growth (P less than 0.01), as evidenced by the largest follicle per cow observed at time of slaughter (3.6 +/- 0.42 vs 11.5 +/- 1.77 mm dia; FF vs S). The intervals from parturition to first estrus (P less than 0.11) and to first progesterone rise (25.3 +/- 1.97 vs 18.0 +/- 3.62 d; P less than 0.06) tended to be delayed by treatment with FF vs S. Many of the cows treated with S ovulated by day 10 PP, they were divided retrospectively into those that had ovulated by (n = 9) or after (n = 5) day 10 PP for analysis. Cows treated with FF had lower (P less than 0.05) and less variable (P less than 0.01) serum FSH concentrations while levels of luteinizing hormone (LH) tended (P less than 0.08) to be greater on days 5 and 10 PP. Follicular fluid decreased levels of FSH (P less than 0.001), but not LH (P less than 0.15), in the samples obtained twice daily compared to S-treated cows that did not ovulate by day 10 PP. Anterior pituitaries were dissociated, and cells from each cow were cultured in order to ascertain whether treatment with FF in vivo would affect gonadotropin secretion in vitro. Estradiol-17 beta (E) was incubated with pituitary cells to determine the effect of E on gonadotropin secretion from cells of PP cows, and to ascertain whether treatment with FF in vivo and with E in vitro would interact to affect secretion of FSH and LH in culture. After 2 d of incubation, cells were treated with 10(-9) M E or vehicle (1% ethanol).(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   
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