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111.
K. Boye G. Almkvist S. I. Nilsson J. Eriksen I. Persson 《European Journal of Soil Science》2011,62(6):874-881
A new data treatment method for fitting spectra obtained by sulphur (S) K‐edge X‐ray absorption near‐edge structure (XANES) spectroscopy was used to quantify the chemical S speciation at three experimental sites with arable soils receiving the same long‐term field treatments. Two treatments, crop residue (CR) incorporation and farmyard manure (FYM) application, with equal applications of mineral nutrients were included in the study. In the new data treatment method, internally calibrated spectra of dilute solutions (30 mm ) of model compounds were used to fit the sample spectra. This greatly enhanced the reliability of quantitative determination of contributing S species in soil samples and soil extracts. The results indicated that long‐term FYM application shifted S species composition from highly oxidized towards intermediate oxidization in two of the soils, but in the third soil the opposite trend was observed. Sulphur XANES spectroscopy of acetylacetone extracts of physically protected and unprotected organic S in two of the soils revealed that physical protection was not related to S speciation; however, intermediate forms of oxidized S species appeared to accumulate in the residual S pool (not extractable by acetylacetone). 相似文献
112.
Aspholm-Hurtig M Dailide G Lahmann M Kalia A Ilver D Roche N Vikström S Sjöström R Lindén S Bäckström A Lundberg C Arnqvist A Mahdavi J Nilsson UJ Velapatiño B Gilman RH Gerhard M Alarcon T López-Brea M Nakazawa T Fox JG Correa P Dominguez-Bello MG Perez-Perez GI Blaser MJ Normark S Carlstedt I Oscarson S Teneberg S Berg DE Borén T 《Science (New York, N.Y.)》2004,305(5683):519-522
Adherence by Helicobacter pylori increases the risk of gastric disease. Here, we report that more than 95% of strains that bind fucosylated blood group antigen bind A, B, and O antigens (generalists), whereas 60% of adherent South American Amerindian strains bind blood group O antigens best (specialists). This specialization coincides with the unique predominance of blood group O in these Amerindians. Strains differed about 1500-fold in binding affinities, and diversifying selection was evident in babA sequences. We propose that cycles of selection for increased and decreased bacterial adherence contribute to babA diversity and that these cycles have led to gradual replacement of generalist binding by specialist binding in blood group O-dominant human populations. 相似文献
113.
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115.
Eyes removed from frog embryos at various stages of development gave a definite pattern of change in the electroretinogram. From the 7th to 9th days the electroretinogram consisted of slow, purely cornea-negative potentials. From the 9th to 10th days the responses were negative but included a prominent fast, negative component superimposed on the slow potentials. During the 11th to 17th days positive potentials appeared and developed. From the 20th day on, the typical electroretinogram of the adult obtained. 相似文献
116.
Nilsson C 《Science (New York, N.Y.)》1966,153(3741):1242-1246
Considerable doubt is cast on the validity of past satellite measurements of micrometeoroid fluxes in which piezoelectric microphones have been used as detectors. Data have been obtained from satellite and laboratory experiments which show that the microphone crystals emit noise when subject to slowly varying temperatures. The rate of noise is consistent with past flight data which have previously been interpreted on the basis of micrometeoroid impacts. These measurements have given rise to the theory that the earth is surrounded by a cloud of dust, although no satisfactory mechanism has yet been found to explain this apparent phenomenon. On the basis of the results reported here, it now appears that whether or not a concentration of dust exists in the vicinity of the earth, the data from satellite microphone measurements should not be used to support such a hypothesis. 相似文献
117.
T. H. Le E. Norberg B. Nielsen P. Madsen K. Nilsson N. Lundeheim 《Acta Agriculturae Scandinavica, Section A - Animal Sciences》2013,63(3-4):132-138
AbstractSelection for sow longevity using information from traits, which are expressed in early life and genetically highly related to longevity, is expected to be more effective than direct selection as it can overcome the disadvantage of late recording of true longevity. Our aim was to investigate the correlation between leg conformation recorded on young pigs, litter size at first parity and longevity of Danish Landrace and Yorkshire sows. Information on conformation from 116,733 Landrace and 89,963 Yorkshire pigs and information on reproduction and longevity from 27,070 Landrace and 11,895 Yorkshire sows were analyzed. All considered traits were low to moderately heritable, ranging from 0.02 to 0.41. In general, both conformation and reproduction traits were favorably genetically correlated with longevity (0.07–0.39 and 0.00–0.58, respectively). These estimates suggest a potential of improving sow longevity by selection on conformation recorded at young age and litter size at first parity. 相似文献
118.
Abstract – Investigating the influence of evolutionary forces on the genetic structure and genetic diversity remains a major challenge. Yet, it is of considerable interest for conservation and management of a species. This study investigates the influence of life‐history and landscape features, such as altitude, connectivity and habitat size, on genetic diversity and genetic structure of brown trout (Salmo trutta L.) with stream‐resident, lake‐dwelling and sea‐migrating life‐history in two river systems in northern Sweden. Using regression tree analysis including ecological and landscape characteristics, we show that life history is the most important variable explaining genetic diversity and population differentiation. Sea‐migrating populations show high diversity and low differentiation, and lake‐ and stream‐resident populations show low diversity and high population differentiation, among all samples. No overall genetic correlation with geographical distance was noted; however, among sea‐migrating populations within the River Vindelälven drainage, this pattern was observed. This study illustrates that life‐history and landscape features help to explain genetic structure and genetic variation. The information is important for conservation and management actions, such as fisheries regulations, habitat restorations, stocking of hatchery fish, defining management units and introducing genetic monitoring programmes. 相似文献
119.
Frauke Ecke Pernilla Christensen Ralf Rentz Mats Nilsson Per Sandström Birger Hörnfeldt 《Landscape Ecology》2010,25(4):551-560
Changes in forest landscape structure have been suggested as a likely contributing factor behind the long-term decline in
the numbers of cyclic grey-sided voles (Clethrionomys rufocanus) in northern Fennoscandian lowland regions in contrast to mountain regions due to the absence of forest management in the
mountains. This study, for the first time, formally explored landscape structure in 29 lowland (LF) and 14 mountain forest
(MF) landscapes (each 2.5 × 2.5 km) in northern Sweden, and related the results to the cumulated spring trapping index of
the grey-sided vole in 2002–2006. The grey-sided vole showed striking contrasts in dynamics close in space and time. The MF
landscapes were characterized by larger patches and less fragmentation of preferred forest types. The grey-sided vole was
trapped in all of 14 analyzed MF landscapes but only in three out of 29 of the LF landscapes. MF and LF landscapes with grey-sided
vole occurrence were characterized by similar focal forest patch size (mean 357 ha, minimum 82 ha and mean 360 ha, minimum
79 ha, respectively). In contrast, these MF compared to the LF landscapes were characterized by larger patches of preferred
forest types and less fragmented preferred forest types and by a lower proportion of clear-cut areas. The present results
suggest that landscape structure is important for the abundance of grey-sided voles in both regions. However, in the mountains
the change from more or less seasonal dynamics to high-amplitude cycles between the mid 1990s and 2000s cannot be explained
by changes in landscape structure. 相似文献
120.
E. Holmström K. Hjelm U. Johansson M. Karlsson S. Valkonen U. Nilsson 《Scandinavian Journal of Forest Research》2016,31(1):56-65
Early management of the regenerated seedlings shapes the future stand properties. To address these issues, pre-commercial thinning (PCT) and control treatments were applied to planted Norway spruce (Picea abies L. Karst) and naturally regenerated birch (Betula pendula Roth., Betula pubescens Ehrh.) stands in forest experiments in southern Sweden (lat. 56–57?N) containing 1.1–5.5?m tall saplings. The treatments were retention of 1000 or 2000?stems?ha?1 of Norway spruce, with no birch or birch at 1000?stems?ha?1. Treatments were replicated with and without annual removal of birch sprouts from stumps. The periodic annual increment (PAI) over five years was calculated for total stand volume and individual trees. The mean PAI of dominant trees was significantly higher both following all PCT treatments than controls, and following low rather than high-density PCT. Birch retention did not affect growth of the dominant trees but PAI was lower in plots with uncontrolled sprouting. The PAI of birch was significantly higher in low-density Norway spruce plots than in control plots and the high-density plots. The treatment response was significant even in stands with initial heights of only 1–2?m. 相似文献