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81.
This work presents data on a suite of diffuse pollutants, monitored in a stream draining an intensively managed grassland on a 30 min time step during a period of intense rainfall to better understand their sources and pathways. Nitrite (92 μg l?1), particulate phosphorus (107 μg l?1) and soluble phosphorus (74 μg l?1) exceeded environmental limits during base flow. Concentrations of nitrate and nitrite were decreased during the storm event, whereas all other pollutants generally increased and exceeded environmental limits where specified, especially when associated with a small subsidiary hydrograph on the rising limb of the main hydrograph. Total pollutants loads, when using a 60 min sampling frequency, would have led to significant over and under-estimations depending on which 60 min sample set was used. In the worst case, loads of ammonium could have been under-estimated by 35% or over estimated by 25% with errors being associated with loads on the rising limb of the hydrograph and more specifically a small subsidiary hydrograph. This subsidiary hydrograph may have occurred as a result of runoff from the farm hard standings within the catchment. Incidental transfer of pollutants associate with this runoff have masked the overall grassland pollutant response. To better understand these different source areas and pollutant dynamics, there is a need for novel tracing techniques to elucidate their relative contribution and pathways.  相似文献   
82.
83.
Chemical leaveners are used in doughs to generate carbon dioxide, as an alternative to yeast, in making a range of bakery products. In this study, the effects of fungal α-amylase and ascorbic acid on chemically leavened doughs were followed by measuring dough extensibility, true rheological properties, the amount of free liquid in doughs following ultracentrifugation and the quality of baked products. As with yeasted doughs, the bake qualities of chemically leavened doughs also improved in the presence of fungal α-amylases. The bake qualities were not affected when the equivalent amount of ascorbic acid was added. The differences in dough formulations were detected from measurements of true rheological properties, not from extensibilities of doughs. The amount of free liquid was larger and of lower viscosity in doughs containing α-amylases. The properties of the continuous liquid phase were found to be important in defining the rheological and baking qualities of doughs.  相似文献   
84.
Class I phosphoinositide 3-kinase (PI3K) signaling pathways regulate several important cellular functions, including cellular growth, division, survival, and movement. Class IB PI3K (also known as PI3Kgamma) links heterotrimeric GTP-binding protein-coupled receptors to these pathways. Activation of class IB PI3K results in the rapid synthesis of phosphatidylinositol-3,4,5-trisphosphate [PtdIns(3,4,5)P3] and its dephosphorylation product PtdIns(3,4)P2 in the plasma membrane. These two lipid messengers bind to pleckstrin homology domain-containing effectors that regulate a complex signaling web downstream of receptor activation. Characteristic features of this pathway are the regulation of protein kinases and the regulation of small guanosine triphosphatases that control cellular movement, adhesion, contraction, and secretion. Most of the ligands that activate class IB PI3K are involved in coordinating the body's response to injury and infection, and recent studies suggest that small molecule inhibitors of this enzyme may represent a novel class of anti-inflammatory therapeutic agents.  相似文献   
85.
This study examined the potential of using near infrared spectroscopy (NIRS) to predict the nutrient composition, energy density and the digestible protein and digestible energy values of lupin kernel meals when fed to rainbow trout. A series of 136 lupin kernel meals were assessed for their protein and energy digestibilities using the diet‐substitution approach in a series of 10 experiments over a 6‐year period from 2002 to 2008. Two reference diets were also included in each experiment. Minimal variance in the digestibility parameters of both reference diets was observed among the experiments ensuring that there was a high degree of robustness in the across‐experiment evaluations. The same lupin kernel meal samples were also scanned using a diode array near infrared spectrophotometer (DA‐NIRS). The spectra obtained by the DA‐NIRS were chemometrically calibrated against both the chemical composition and the digestible value data using multivariate analysis software. The cross validation tests used in this study provide a valid indication of the potential to predict the nutrient composition, energy value and digestible protein and energy values of the lupin kernel meals as used in diets for rainbow trout. That the standard errors of cross validation (SECV) of the parameters investigated were generally commensurate with the cross trial variation seen in the reference sample indicating robust calibrations for the two target parameters of digestible protein and digestible energy. Therefore this study demonstrates that within one raw material type that not only does significant variability in the digestible value of the raw materials exist, but that it is possible to use NIRS technology to provide rapid estimates of the digestible value of those raw materials in near real‐time.  相似文献   
86.
  • 1. Trap fishing is widespread on coral reefs but the sustainability of this practice is causing concern because it is efficient and unselective. The effects of trap fishing were investigated by comparing fish assemblages among six Caribbean islands subject to different trapping pressures. These ranged from none in Bonaire and Saba increasing through Puerto Rico, St Lucia, Dominica and Jamaica respectively.
  • 2. Fish were censused at depths of 5 m and 15 m on fore‐reef slopes by counting the numbers within replicate 10 m diameter areas for 15 min. Between 64 and 1375 counts were made in each country.
  • 3. In St Lucia and Jamaica abundance of fish censused on the reef was compared to representation in traps which were visually sampled underwater in the area of fish counts. Twenty‐three traps were sampled in Jamaica and 75 in St Lucia. For some comparisons between these islands, St Lucian sampling effort was reduced to that of Jamaica (23 traps and 112 counts) by randomly sub‐sampling 10 times.
  • 4. Traps contained 54 different species in St Lucia and 22 in Jamaica, while there were 90 and 57 respectively in counts. After reducing St Lucian sampling effort to Jamaican levels, an average of 35 species were found in traps and 70 seen in counts. Of these, 76% in St Lucia and 73% in Jamaica were relatively more abundant in traps than they were on the reef.
  • 5. Species were considered to be highly susceptible to trapping if the ratio of their abundance in traps compared to that on the reef exceeded 3:1. Trapping pressure was approximately three and a half times greater in Jamaica than St Lucia. After equalizing sampling effort, there was an average of 16 highly trappable species in St Lucia compared to 13 in Jamaica. Species did not always appear highly trappable in both countries. Eleven of St Lucia's highly trappable species were absent from Jamaica (falling to 8.5 on average after equalizing sampling effort), but none vice versa, suggesting that trapping may have contributed to their absence or rarity on Jamaican reefs.
  • 6. The Tetraodontiformes, which include many non‐target species, were particularly susceptible to trapping in both countries. Their abundance in the six islands censused was inversely related to trap fishing pressure, as was that of two other non‐target families, butterflyfish (Chaetodontidae) and angelfish (Pomacanthidae).
  • 7. To determine whether fish that are common in traps in St Lucia are reaching sexual maturity before capture, size frequency data for 23 species from a sample of trap catches were gathered and examined for their state of maturity. In seven species, more than a third of 705 trapped fish were immature, indicating that trap fishing causes growth over‐fishing (premature removal of fish), and calling into question the sustainability of yields for these species.
  • 8. In conclusion, at the intensities seen in this study, trap fisheries cause serious over‐fishing, reduce biodiversity, and alter ecosystem structure. While commonly perceived as low impact, coral reef trap fisheries in the Caribbean and further afield, need tighter regulation and control.
Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
87.
88.
On 27 June 1997, the Near Earth Asteroid Rendezvous (NEAR) spacecraft flew within 1212 kilometers of asteroid 253 Mathilde. Mathilde is an irregular, heavily cratered body measuring 66 kilometers by 48 kilometers by 46 kilometers. The asteroid's surface is dark (estimated albedo between 0.035 and 0.050) and similar in color to some CM carbonaceous chondrites. No albedo or color variations were detected. The volume derived from the images and the mass from Doppler tracking of the spacecraft yield a mean density of 1.3 +/- 0.2 grams per cubic centimeter, about half that of CM chondrites, indicating a porous interior structure.  相似文献   
89.
We used molecular markers to study genetic relationships in a diverse collection of 85 domestic dog breeds. Differences among breeds accounted for approximately 30% of genetic variation. Microsatellite genotypes were used to correctly assign 99% of individual dogs to breeds. Phylogenetic analysis separated several breeds with ancient origins from the remaining breeds with modern European origins. We identified four genetic clusters, which predominantly contained breeds with similar geographic origin, morphology, or role in human activities. These results provide a genetic classification of dog breeds and will aid studies of the genetics of phenotypic breed differences.  相似文献   
90.
Interspecific gene flow from crop species into wild relatives may compromise the genetic integrity of native species and in the case of transgenic crops lead to the escape of transgenes into natural populations. Approximately 72% of the upland cotton (Gossypium hirsutum L.) acreage grown in the United States in 2000 utilized transgenic cultivars. The closest relative of G. hirsutum is G. tomentosum Nuttall ex Seeman, endemic to the Hawaiian archipelago. Because these two species are fully interfertile, cultivation of transgenic G. hirsutum in the Hawaiian Islands is restricted. We investigated the possibility of identifying AFLP genetic markers that are diagnostic for each species and thus could be used in future studies to detect introgression between them. In addition, we were interested in comparing levels and geographic patterns of AFLP diversity in G. tomentosum to previous estimates using allozyme data. AFLP analysis led to the detection of 11 and 16 species-specific markers for G. tomentosum and G. hirsutum, respectively. These species-specific AFLP markers will be useful for detecting gene flow between G. hirsutum and G. tomentosum that has occurred in the past and thus might occur in the future if the restrictions on cultivation of transgenic G. hirsutum are relaxed in the Hawaiian Islands. Little genetic diversity and limited geographic patterning were discovered using AFLP markers, consistent with data from previous allozyme studies.  相似文献   
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