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21.
Rasoul Yousefpour Jette Bredahl Jacobsen Henrik Meilby Bo Jellesmark Thorsen 《Annals of Forest Science》2014,71(2):301-312
Context
We develop a modelling concept that updates knowledge and beliefs about future climate changes, to model a decision-maker’s choice of forest management alternatives, the outcomes of which depend on the climate condition.Aims
Applying Bayes’ updating, we show that while the true climate trajectory is initially unknown, it will eventually be revealed as novel information become available. How fast the decision-maker will form firm beliefs about future climate depends on the divergence among climate trajectories, the long-term speed of change, and the short-term climate variability.Methods
We simplify climate change outcomes to three possible trajectories of low, medium and high changes. We solve a hypothetical decision-making problem of tree species choice aiming at maximising the land expectation value (LEV) and based on the updated beliefs at each time step.Results
The economic value of an adaptive approach would be positive and higher than a non-adaptive approach if a large change in climate state occurs and may influence forest decisions.Conclusion
Updating knowledge to handle climate change uncertainty is a valuable addition to the study of adaptive forest management in general and the analysis of forest decision-making, in particular for irreversible or costly decisions of long-term impact. 相似文献22.
Abstract. The feasibility of including individual records on correlated traits in a family selection programme which aims to increase resistance to furunculosis in Atlantic salmon was studied; markers were selected because of their potential role in the pathogenesis of the disease. Fibrinogen and α2 -antiplasmin both show genetic variation; both are correlated with survival after challenge with Aeromonas salmonicida , the correlation being 0·44 and 0·37 ( P < 0·05), respectively, and it is possible to measure both on a large scale at low costs. Contrary to α2 -antiplasmin, fibrinogen was negatively correlated with survival due to furunculosis within the 10 most resistant families and within the 10 most susceptible families in contrast to an overall positive correlation. This inconsistency could be attributable to the presence of different allelic phases in different families, and of major linked loci influencing survival and fibrinogen levels. Thus, only α2 -antiplasmin fulfils the requirements for a marker trait for resistance to the disease suitable for individual selection at the population level, whereas the use of fibrinogen would be restricted to within family selection. The full statistical model explained 51% of the variation in resistance to furunculosis, and α2 -antiplasmin contributed 15% to this variation when considered as a separate entity. Thus, the additional gain from including individual records on α2 -antiplasmin in a family selection programme could be significant. 相似文献
23.
Odd J. Jacobsen 《Aquaculture (Amsterdam, Netherlands)》1977,11(1):81-84
The growth of brown trout (Salmo trutta) yearlings (18 months) was studied at environmental pH levels of about 6.26, 5.44 and 5.00 and a daily ration of 2.9% of the initial body weight. Growth increments for fish at each pH level during a 48-day period were similar. 相似文献
24.
Fatemeh Bakhtiari Jette Bredahl Jacobsen Frank Søndergaard Jensen 《Urban Forestry & Urban Greening》2014,13(4):662-671
Conflicts among forest visitors have direct effects on the quality of a recreational experience. As the number of visitors to forests close to residential areas increases, as well as the number of different activities, so does the potential for perceived conflicts. According to the literature, expanding knowledge of conflict characteristics and their causes is important for recreation planners and managers who aim to reduce conflicts.In the present study, different forest user groups were identified and categorised according to their pursued activities, and for each group, causes of conflict were identified. Furthermore, a choice experiment was constructed to estimate the distance visitors are willing to travel to encounter few visitors as opposed to many visitors, and thereby potentially experience fewer conflicts. Comparing the marginal willingness to travel (WTT) of different user groups suggests that some groups have a WTT further than the average to reach a forest with ‘Few’ visitors. The average WTT to reach a forest area with ‘Few’ visitors. ‘Mountain bikers,’ ‘Peace and nature lovers’ and ‘Horse riders’ are willing to travel 4 km more than the average per visit to reach a less crowded forest. At the other end of the scale, we find that people who are doing physical exercise are willing to travel 2 km less than the average to reach a less crowded forest. 相似文献
25.
J.L. Christiansen S.-E. Jacobsen 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(6):539-544
Abstract Sensitivity to photoperiod in quinoa (Chenopodium quinoa Willd.) was studied under controlled conditions to enhance crop adaptation to environments outside its centre of origin. Two varieties, a traditional variety from Bolivia (Real), which will not mature under Danish conditions, and an early maturing variety (Q52), developed for Danish climatic conditions, were used in this reciprocal transfer experiment. Plants were moved from a short daylength of 10 h (SD) to a long daylength of 18 h (LD) and vice versa at set intervals from sowing to 100 days after sowing (DAS). A reaction of LD in time to flowering was observed only in the Bolivian variety Real. Under SD both varieties flowered after 39 DAS. For Real the LD regime resulted in a moderate increase in time to flowering to 44 DAS. The non-sensitive, juvenile period in Real was estimated to be approximately 16 days. In Q52 a moderate increase in the number of leaves was formed on the main stem after flowering at LD, which indicates that some daylength sensitivity remains. The most striking difference occurred during seed filling, when going from SD to LD. In Q52 the time from the end of flowering to maturity increased from 39 to 52 days. Under SD, Real had a seed-filling period similar to Q52, but at LD Real remained with green leaves during seed filling. Hard seed was observed in the still green perigonium 57 days after end of flowering. At this moment re-shooting occurred from the inflorescence, and seed maturity was not reached at the termination of the experiment at 150 DAS. This study shows that flower induction is not a major problem for adaptation of quinoa to North European conditions but that a very strong, daylength sensitive, stay green reaction is the main cause of the late maturity of South American introductions. 相似文献
26.
F. Razzaghi S. H. Ahmadi S.‐E. Jacobsen C. R. Jensen M. N. Andersen 《Journal of Agronomy and Crop Science》2012,198(3):173-184
Drought and salinity reduce crop productivity especially in arid and semi‐arid regions, and finding a crop which produces yield under these adverse conditions is therefore very important. Quinoa (Chenopodium quinoa Willd.) is such a crop. Hence, a study was conducted in field lysimeters to investigate the effect of salinity and soil–drying on radiation use efficiency, yield and water productivity of quinoa. Quinoa was exposed to five salinity levels (0, 10, 20, 30 and 40 dS m?1) of irrigation water from flower initiation onwards. During the seed‐filling phase the five salinity levels were divided between two levels of irrigation, either full irrigation (FI; 95 % of field capacity) or non‐irrigated progressive drought (PD). The intercepted photosynthetically active radiation was hardly affected by salinity (8 % decrease at 40 dS m?1) and did not differ significantly between FI and PD. Radiation use efficiency of dry matter was similar between salinity levels and between FI and PD. In line with this, no negative effect of severe salinity and soil–drying on total dry matter could be detected. Salinity levels between 20 and 40 dS m?1 significantly reduced the seed yield by ca. 33 % compared with 0 dS m?1 treatment owing to a 15–30 % reduction in seed number per m2, whereas the seed yield of PD was 8 % less than FI. Consequently, nitrogen harvested in seed was decreased by salinity although the total N‐uptake was increased. Both salinity and drought increased the water productivity of dry matter. Increasing salinity from 20 to 40 dS m?1 did not further decrease the seed number per m2 and seed yield, which shows that quinoa (cv. Titicaca) acclimated to saline conditions when exposed to salinity levels between 20 and 40 dS m?1. 相似文献
27.
The commercial and economic value of genetically modified crops is determined by a predictable, consistent and stable transmission
and expression of the transgenes in successive generations. No gene inactivation is expected after selfings or crosses with
non-transformed plants of homozygous transgenic oilseed rape plants if the expression of the transgene in homozygous or hemizygous
nature in such plants is stable. The segregation ratios of phosphinothricin (PPT) tolerance in successive generations of selfings
and mutual crosses of a few independent transgenic PPT-tolerant oilseed rape plants indicated a dominant, monogenic inheritance.
In within-variety and between-variety crosses no transgene inactivation was observed. However, after selfings and backcrosses
with non-transgenic oilseed rape infrequent loss of the expression of the PPT tolerance transgene was observed independent
from its homozygous or hemizygous nature. Molecular analysis of PPT-susceptible plants showed that the loss of expression
was due to gene inactivation and not to the absence of the transgene. Methylation and co-suppression are mechanisms that might
cause reduced or even loss of expression of the transgene in later generations. The implications of this observation for seed
multiplication of varieties and breeding activities with transgenic oilseed rape are discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
28.
Colchicine induced polyploids have not directly contributed for crop improvement in the past. On the other hand, the so-called
natural polyploids, derived from the functioning of numerically unreduced(2n) gametes have been shown to be more relevant for crop improvement in many cases. Different types of cytological abnormalities
during meiosis can give rise to 2n gametes and the genetic composition of these gametes is variable. Depending on the type meiotic abnormalities, various types
of 2ngametes, such as first division restitution(FDR), second division restitution (SDR),indeterminate meiotic restitution (IMR)
and post meiotic restitution (PMR) gametes,among others, have been described in recent years. For the improvement of autopolyploids
such as potato, alfalfa,Vaccinium spp., and some of the fodder grasses, FDR gametes have been proved to be highly useful. However, the use of 2n gametes for the improvement of allopolyploid crops has received much less attention so far. Some of the investigations on
allopolyploids, derived from Festuca-Lolium, Alstroemeria and Lilium species hybrids, have revealed that 2ngametes can be most useful for the introgression of alien genes and chromosomes into cultivars. An important feature of using
sexual polyploidization in the case of allopolyploids is that introgression can be achieved through recombination due to genetic
crossing-over between alien chromosomes as well as addition of alien chromosomes, which is extremely difficult or impossible
to achieve in the case of colchicine induced allopolyploids. Because of the recent developments in the field of plant molecular
biology, methods have become available for the analysis of 2ngametes and sexual polyploid progenies more accurately and to develop systematic breeding approaches. The methods include
DNA in situ hybridization (GISH and FISH)and molecular mapping (AFLP, RFLP, RAPDs).In addition to providing basic information
on the genetic and genome composition of the polyploid progenies, these methods can be potentially useful for a more efficient
creation of desirable breeding material and cultivars.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
29.
R. C. B. Hutten M. G. M. Schippers J. Eising P. M. van Til J. G. Th. Hermsen E. Jacobsen 《Euphytica》1996,88(3):175-179
Summary The parental effects on progenies from potato 4x.2x(FDR) crosses were analyzed to determine anether and to what extent selection criteria used for selecting tetraploid breeding lines have to be adjusted when selecting diploid breeding lines. For vine maturity and chip colour multiple regression analysis of progeny means on means of diploid and tetraploid parents revealed high coefficients of determination (R2) for both characters, indicating good predicting power of the performance of both diploid and tetraploid parents on the performance of their 4x.2x progenies. For vine maturity the multiple regression slope for the tetraploid perents was significantly larger than for the diploid parents, and progeny means were towards the tetraploid parents. This indicates that selection criteria for vine maturity may be less stringent at the diploid level. However, diploids may be earlier maturing than tetraploids and therefore selection criteria can better be similar at both ploidy levels. For chip colour, multiple regression slopes for diploid and tetraploid parents were similar and progeny means were towards the darkest coloured parent irrespective of its ploidy level. This indicates that selection of breeding lines for chip colour can be conducted similarly at both ploidy levels. 相似文献
30.
Summary Selection criteria for agronomic characters in a potato breeding program at the diploid (2x) level may differ from selection criteria used when selecting breeding lines at the tetraploid (4x) level. Differences between selection criteria are expected, (1) when expression of the characters is different at both ploidy levels and/or (2) when the effect of diploid breeding lines on agronomic characters of tetraploid progenies is different from the effect of tetraploid breeding lines. In this investigation sets of diploid and tetraploid progenies, each set derived from the same 2x.2x cross, were compared as to the expression of six agronomic characters. Diploid progenies had significantly lower yields (due to smaller tubers) and significantly higher under water weights than tetraploid progenies. Vine maturity and chip colour were similarly expressed at both ploidy levels. Correlations between yield and yield components, and between under water weight and chip colour were similar at both ploidy levels. The lower yields and higher under water weights found in diploids point to the need of different selection criteria for selecting diploid and tetraploid breeding lines. 相似文献