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131.
Felipe Rossetti de Paula Pedro Gerhard Seth J. Wenger Anderson Ferreira Carlos Alberto Vettorazzi Silvio Frosini de Barros Ferraz 《Landscape Ecology》2013,28(1):13-27
Large wood (LW) is critical to the structure and function of streams and forests are the main LW source to stream channels. To assess the influence of forest cover changes at different spatial scales on in-stream LW quantity, we selected eighteen catchments (2nd–4th order) in Southeastern Brazil with forests at different levels of alterations. In each catchment we quantified the pattern of forest cover (% cover and relative catchment position), the physical characteristics of catchments (elevation and slope), the characteristics of channels (wetted channel width and depth), the abundance and volume of in-stream LW, and the frequency of LW pools. We used simple and multiple linear regression to assess the response of LW variables to landscape and stream reach variables. Most of the LW was relatively small; 72 % had a diameter <20 cm, and 66 % had a length <5 m. Although percent forest cover at reach scale had substantial support to explain LW variables, the best predictors of LW variables were forest cover at broader scales (LW abundance and LW pool frequency were best predicted by forest at intermediate distance at the catchment scale and LW volume was best predicted by forest cover at the drainage network scale), suggesting that downstream transport is an important process in addition to local processes in our study area. These findings have important management implications because although low forested reaches receive less LW from local forests (or no LW in the case of deforested stream reaches), they are receiving LW from upstream forested reaches. However, the material is generally small, unstable and likely to be easily flushed. This suggests that not only should riparian forest conservation encompass the full drainage network, but forests should also be allowed to regenerate to later successional stages to provide larger, higher quality LW for natural structuring of streams. 相似文献
132.
It is possible to separate rapeseed meal into two fractions, one of lower hull and higher protein content, the other of higher hull and lower protein content than whole rapeseed meal. The low‐hull fraction was found to contain about 25% more, and the high‐hull fraction about 25% less, metabolisable energy than the whole rapeseed meal.
Soluble tannins, oxazolidinethione, isothiocyanates and phosphorus were found to be concentrated in the endosperm rather than the pericarp of the seed while with calcium the reverse occurred.
No consistent changes in amino acid distribution resulting from the air‐classification of whole rapeseed meal into low‐hull and high‐hull fractions were observed. 相似文献
133.
Natural resource agencies often use mail surveys to collect stakeholder information. A major concern of mail surveys, however, has long been relatively low response rates compared to telephone or face-to-face interviews. Survey research has largely focused on achieving high response rates; however, in some situations even well-designed surveys can have low response rates. We present an example of a three-page (25 questions) survey measuring opinions and attitudes about native fish management in the South Dakota Black Hills region that received a relatively low response rate (21%) using a mailing, postcard reminder, and second mailing of the questionnaire. We compared response rate and data quality of a third mailing of the full questionnaire with a one-page (five questions) questionnaire measuring key variables to evaluate possible nonresponse bias. Within the total survey error (TSE) paradigm we provide evidence that reliable and useful information was collected by this survey. 相似文献
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135.
Romain M. Gloaguen Seth Byrd Diane L. Rowland D. Ray Langham Annie Couch 《Journal of Crop Improvement》2018,32(3):387-417
Sesame (Sesamum indicum L.) is being considered for commercial production in the southeastern USA, but very little is known about its potential and the appropriate management practices required to achieve sustainable yield potential in the area. This study thus aims to determine the optimal planting date and row spacing for several sesame cultivars. Traits examined were yield, plant height, number of nodes on the main stem, number of branches, height to first capsule on the main stem, and number of plants per meter. A first trial investigated three planting dates in Citra, FL (May, June, and July); whereas a second one examined several row spacings at two locations: 19 and 38.1 cm in Citra; and 19, 38.1, and 76.2 cm in Live Oak, FL. The May planting date showed higher yields, number of nodes, and taller plants than the other dates. Accumulated air and soil growing degree days (GDDs), rainfall, and solar radiation values were calculated for each planting date in both years. Soil GDDs provided similar results to air GDDs; thus, either model would seem appropriate for predicting crop development in this region. Plant height, number of nodes with capsules, and number of branches were increased at wider row spacings in the Live Oak trials as compared with narrow rows. These two trials illustrated the potential of sesame for attaining economically sustainable yields in the southeastern USA, but further exploration and modeling of agronomic traits will be needed to reach the crop’s full yield potential in these regions. 相似文献
136.
137.
Sean M. Cochran Seth Ricker Colin Anderson Sean P. Gallagher Darren M. Ward 《Fisheries Management and Ecology》2019,26(2):165-171
Obtaining reliable estimates of marine survival is essential for understanding anadromous salmon population dynamics. Two common approaches to estimating marine survival are (a) dividing abundance of returning adult salmon abundance by abundance of smolts from the same cohort, or (b) tagging a portion of the migrating smolts and estimating the return rate of tagged adults. This study compared these two approaches to estimating marine survival for coho salmon, Oncorhynchus kisutch (Walbaum), across multiple years in three California streams. Abundance‐based survival estimates were higher than tag‐based estimates; average estimates for the two techniques differed from 1.5‐fold to 7.4‐fold across streams. One likely cause for these divergent estimates is migration of juveniles from natal habitat before smolt trapping begins, resulting in an underestimate of smolt abundance and an overestimate of marine survival rate for the abundance‐based method. Estimates of marine survival obtained from abundance estimates and tag returns are not directly comparable. 相似文献
138.
139.
We tested the effects of exponential nutrient loading and springtime carbon loading during nursery culture on the field performance
of black spruce (Picea mariana (Mill.) B.S.P.). Seedlings were grown from seed with a conventional, fixed dose fertilizer (10 mg N seedling−1) or an exponential nutrient loading regime (75 mg N seedling−1). The following spring, seedlings were exposed for two weeks to either ambient (370 ppm) or elevated levels of CO2 (800 ppm) and then planted in the field; seedling growth was followed for the next six years. Exponential nutrient loading
increased seedling height, stem diameter and leader growth, with the largest increases in height and leader length occurring
in the first three years after outplanting. Carbon loading increased seedling height and leader length, but only in seedlings
that had been exponentially nutrient loaded. A combination of carbon and nutrient loading increased shoot height 26%, stem
diameter 37% and leader length 40% over trees that received neither treatment. These results demonstrate that the growth enhancement
seen under exponential nutrient loading is maintained under field conditions for at least six years. Carbon loading just before
outplanting was a useful supplement to nutrient loading, but was ineffective in the absence of nutrient loading. 相似文献
140.