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51.
52.
Aurelija Samuiloviene Antanas Kontautas Riho Gross 《Fish physiology and biochemistry》2009,35(4):649-659
The genetic diversity and differentiation of sea trout were studied in three river basins in Lithuania: Akmena-Dane, Bartuva,
and Nemunas. A total of 282 individuals were genotyped at eight microsatellite loci. A similar level of genetic diversity
was found in all of the populations studied: mean allelic richness ranged from 3.64 to 5.03, and average expected heterozygosity
ranged from 0.588 to 0.721. Significant genetic divergence was observed among the different river basins as well as between
populations within the drainages. All pairwise F
ST values were highly significant, ranging from 0.027 to 0.197. The analysis of molecular variance showed rather weak hierarchical
population structuring within the Nemunas basin, which may be explained by extensive gene flow among different river basins
or, alternatively, reflect the influence of artificial breeding. Information on genetic diversity and differentiation of the
Lithuanian sea trout populations will be useful for future management decisions. 相似文献
53.
ABSTRACT: The present study reports the annual variation in consumption of the sea urchin Strongylocentrotus intermedius by avian predators on a rocky shore where the culture of sea urchins has been conducted. Carrion crow and a few gull species were the most abundant avian predators and consumed a large number of sea urchins. Crows consumed mostly natural sea urchins, approximately 36 kg ww/ha per year on the intertidal rocky bench, but the gull species consumed mostly cultured sea urchins, approximately 100 kg ww/ha per year in the culture area. The seasonal variation in the amount of sea urchins consumed by crows was higher than that by the gull species, presumably because of the difference in foraging behavior in association with the seasonal tidal cycle. The natural sea urchins consumed are an allochthonous input from the subtidal to the intertidal habitat, and thus, crow predation may not affect the natural and the cultured populations of the sea urchin. The gull species consumed much of the cultured sea urchin, and thus, may be regarded as an effective predator causing damage to sea urchin culture. The results suggest that further studies are needed to determine why the gull species selectively feed on cultured sea urchins. 相似文献
54.
Sung Il Lee Kerim Y. Aydin Paul D. Spencer Thomas K. Wilderbuer Chang Ik Zhang 《Fisheries Science》2010,76(3):411-434
We evaluated the role of flatfishes in the organization and structure of the eastern Bering Sea ecosystem using the Ecopath/Ecosim
approach. As basic input data for the Ecopath/Ecosim model, we used estimates of biomass from bottom trawl surveys and age-structured
population models, production/biomass (P/B) ratio, consumption/biomass (Q/B) ratio, diet composition (DC), and fisheries harvests for each component of species or species groups. We estimated the trophic
level of each component, niche overlaps among flatfishes, and the impacts of competition and predation on flatfish species
in the eastern Bering Sea ecosystem. Based on those estimates, we developed the tropho-dynamic structure of the ecosystem,
and the model was used to simulate ecological effects of fishery exploitation patterns. No single flatfish species appeared
to have a profound and uniquely important role in the organization and structure of the ecosystem. Instead, the most important
component among the guild of flatfish species appeared to be yellowfin sole Pleuronectes asper, which had greater biomass than other flatfish and a relatively diverse diet among the small flatfish species. Pacific halibut
Hippoglossus stenolepis, Greenland turbot Reinhardtius hippoglossoides, and arrowtooth flounder Atheresthes stomias were important keystone predators in the eastern Bering Sea ecosystem together with some groups of marine mammals and sea
birds. Intra flatfish complex cannibalism was not observed, however, substantial diet overlaps were common in the flatfish
guild system. 相似文献
55.
ABSTRACT: This study assessed the stock-recruitment relationship (SRR) for the Japanese sardine Sardinops melanostictus in the North-western Pacific. Of the 20 SRR models investigated, the Akaike information criterion (AIC) was the minimum (AIC = 551.2) when the data were separated into two groups (A and B) and the log-normal distribution was applied as the error term. Group A was constructed with SRR data from 1976–1987 and 1992–2004. Group B consisted of data from 1988–1991. The AIC minimum model was R = 22.8 S × e ε for Group A, where R , S , and ε denote the recruitment of sardine (individual number of 0-year old fish), spawning stock biomass (SSB), and error term, respectively. This model indicated that recruitment was proportional to the SSB and that no density-dependent effect operated over the range of SSB investigated (51 000–11.3 million t). Recruitment was markedly higher (lower) when the sea surface temperature (SST) of the Kuroshio Extension area in February was low (high). The essential SRR can simply be expressed as R = 22.8 S × e ε with the level of recruitment deviating from the model to a greater or lesser degree depending on the environmental conditions. 相似文献
56.
Aki Namba Yuya Shigenobu Masahiro Kobayashi Takanori Kobayashi Ichiro Oohara 《Fisheries Science》2010,76(5):873-878
To construct high-quality 16S rDNA clone libraries for microbial communities associated with Porphyra yezoensis and to minimize the detection of rDNA from leafy gametophytes of P. yezoensis, we designed a new 16S rDNA universal primer (75F). Of the clones prepared using 75F, which was designed to distinguish between
bacteria and P. yezoensis, 95% were classified into four groups, namely, β-proteobacteria, γ-proteobacteria, Lentisphaerae, and Flavobacteria. PCR-based analysis of the 16S rDNA primer constructed in this study can be used to implement 16S rDNA-based methodologies
for the investigation of microbial community composition and diversity related to the Porphyra group. 相似文献
57.
Yong-Xin Liu Gui-Xing Wang Yu-Fen Wang Fei Si Zhao-Hui Sun Xiao-Yan Zhang Jia-Di Wang Hai-Jin Liu 《Fisheries Science》2011,77(1):87-93
To estimate genetic parameters of growth traits in Japanese flounder Paralichthys olivaceus, full-sib and half-sib families were produced in three consecutive years at the Beidaihe Central Experiment Station in China.
Each year 8–28 families were produced. The body weight, body length and body depth at 180, 240, and 360 days of age were measured
for 5,224 individuals. Four animal models were used to examine the phenotypic variation of growth traits and were compared
using the likelihood ratio test. The results showed that estimates for additive genetic effect heritabilities varied greatly
depending on the model, trait and age. The maternal effect had a significant impact on phenotypic variation only for body
depth at 180 days of age, which explained 49% of the phenotypic variance. The ratio of full-sib effect to phenotypic variation
ranged from 0.09 to 0.22. Growth traits all exhibited low heritability (0.13–0.39), indicating that there is the potential
for family selection breeding for these traits in Japanese flounder. Using the full model with the fixed, full-sib family,
additive and maternal genetic effects, genetic correlations among the three traits for fish of the same age were estimated
to be more than 0.80. Generally, the genetic correlations gradually increased as age increased. 相似文献
58.
59.
60.
Huimin Yang Murray Unkovich Ann McNeill Xianzhi Wang 《Biology and Fertility of Soils》2011,47(4):377-385
Symbiotic N2 fixation by lucerne (Medicago sativa) has capacity to provide significant inputs of N to agro-ecosystems, and the species has also been shown to scavenge soil
mineral N and thus act as a sink for excess reactive N. The balance between these two N cycle processes was investigated in
an extensive irrigated lucerne growing region where nitrate contamination of groundwater has been reported. We sampled 18
permanent pure lucerne stands under irrigation for standing dry matter, total shoot N, and N2 fixation using 15N natural abundance along with activity of the inducible enzyme nitrate reductase as indicators of use of soil NO3− by lucerne. On average 65% of lucerne N was obtained from symbiotic N2 fixation. Converting standing dry matter estimates to annual N2 fixation amounts we calculated average N2 fixation of 311 kg N/ha, including N in roots and nodules. Uptake of N from soil by lucerne was calculated to be 181 kg N/ha/year.
We were not able to identify the source of this soil mineral N, although nitrate reductase activity of lucerne was higher
than that of non-N2 fixing species examined. 相似文献