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991.
Yongjie Wang Zhongbo Wei Qilong Zeng Huan Zhong 《Journal of Soils and Sediments》2016,16(12):2720-2727
Purpose
Both selenium (Se) and sulfate could largely affect methylmercury (MeHg) dynamics and phytoavailability in soil-rice systems, while their combined effects are less understood. Here, we aimed at exploring the potential effects of sulfate on MeHg accumulation in rice in the presence of Se.Materials and methods
Rice was cultivated in inorganic Hg-spiked soils amended with Se only (selenite/selenate, “Se treatments”) or Se and sulfate (“Se?+?Sulfate treatments”). Soil parameters (e.g., pH and redox potential (Eh)), MeHg concentrations in soils, as well as MeHg or Se accumulation in rice plants were quantified during the rice growth period.Results and discussion
Soil MeHg concentrations were generally comparable between Se?+?Sulfate and Se treatments. However, MeHg uptake by rice plants in Se?+?Sulfate treatments was 9–31 % lower than those in Se treatments, possibly due to the increased soil pH and formation of iron sulfides, which may reduce MeHg phytoavailability under sulfate amendment. Furthermore, sulfate input enhanced Se accumulation in root (especially in the presence of selenate), which could be responsible for the increased MeHg distribution in root and thus lower MeHg distribution in grain. Consequently, the reduced plant uptake of MeHg together with the decreased MeHg distribution in grain resulted in decline of grain MeHg concentrations in Se?+?Sulfate treatments (8–31 % lower compared to Se treatments).Conclusions
Our results suggest that sulfate input with Se could further reduce MeHg accumulation in rice, which improved mechanistic understanding of MeHg behaviors in soil-rice systems.992.
Martyna A. Rzętała 《Journal of Soils and Sediments》2016,16(10):2458-2470
Purpose
Cadmium (Cd) is considered a toxic element and its concentrations are relevant to human health and the environment. Therefore, the purpose of the study was to determine the extent to which the bottom sediments of water bodies (artificial lakes and ponds) in the Silesian Upland in southern Poland are contaminated with Cd; an attempt was also made to determine the factors that condition spatial differences in the concentration of this element between individual water bodies in the region.Materials and methods
Measurements of the Cd content in bottom sediments were carried out in 35 water bodies in southern Poland in 2011 and 2012. Depending on the surface area and morphometric characteristics, from two to nine samples representative in terms of sediment thickness were collected in each water body. Cadmium concentrations were determined for 92 0.25 g aliquots using the TD-ICP method.Results and discussion
Cadmium content in all samples (0.7–580.0 mg kg?1) was higher than the natural range of concentrations for this element in the Earth’s crust (0.1–0.3 mg kg?1) and the geochemical background for Poland (0.5 mg kg?1) and, with a few exceptions, was also higher than the preindustrial concentration (1.0 mg kg?1) and the regional geochemical background (2.5 mg kg?1). Adopting natural Cd concentrations in the Earth’s crust (0.1–0.3 mg kg?1) as the baseline for the geoaccumulation index (Igeo), the sediments examined can be classified as extremely and heavily contaminated (and moderately contaminated in a small number of cases). The assessment of sediment quality based on Igeo, with the regional geochemical background (2.5 mg kg?1) adopted as the baseline, results in non-contaminated and moderately contaminated sediments being dominant with a far smaller number of heavily and extremely contaminated ones.Conclusions
In the case of several water bodies, Cd concentrations were at record levels that have not been found anywhere else in the world. On the basis of the Igeo, sediments of varying quality were found—from virtually uncontaminated to extremely contaminated. The Igeo index as an indicator of the quality of bottom sediments is a measure that requires careful interpretation, especially when different concentration levels regarded as natural are used for determining its value.993.
Fernández PL Pablos F Martín MJ González AG 《Journal of agricultural and food chemistry》2002,50(7):1833-1839
994.
David M. Cole Timothy L. White P. K. R. Nair 《Genetic Resources and Crop Evolution》2007,54(1):189-204
Knowledge of the effects of farmer practices on population genetic parameters of peach palm (Bactris gasipaes Kunth) is relevant to the improvement and conservation of the palm’s genetic resources. Microsatellite markers were used
to assess genetic diversity and population structure of peach palm in swidden-fallow agroforestry systems in northeastern
Peru. The study covered eight communities, comprising two study areas 160 km apart – one occupied by indigenous Amerindians
and the other by mixed race campesinos. Simultaneous analysis of an ex situ peach palm germplasm collection provided a means to compare population genetic parameters. Farmers who were surveyed on seed
selection practices for peach palm reported that an average of only four palms (4.3 for campesino and 1.5 for indigenous populations)
were used to provide seed for the establishment of the forest gardens sampled. As expected, inbreeding coefficients observed
within communities were relatively high (f = 0.105 − 0.210), however, observed heterozygosities within communities were also high (0.625–0.741). A metapopulation approach
was used to describe migration within and among regions, implying a hierarchical structure of gene flow which maintains relatively
high levels of genetic diversity. Seed migration was found to occur over longer distances (≤600 km) and at a higher frequency
(46% of palms sampled) in the indigenous study area, and a proportionally greater number of alleles was found (49 vs. 43 over
three loci) with twice as many private alleles occurring only in the indigenous populations. The farmers’ practice of preserving
remnant palms through successive swidden generations may have contributed to the maintenance of alleles by reducing the severity
of founder effects. Although the campesino study area exhibited a significant (20% of the variation; p < 0.01) isolation-by-distance relationship across 35 km distance, in general, both study populations had relatively limited
genetic structure (θ = 0.012–0.03), which is believed to have resulted from the exchange of seeds over long distances and
periods of time. 相似文献
995.
996.
Regional Sediment Deficits in the Dutch Lowlands: Implications for Long-Term Land-Use Options (8 pp)
Michiel J. van der Meulen Ad J. F. van der Spek Ger de Lange Stephan H. L. L. Gruijters Serge F. van Gessel Buu-Long Nguyen Denise Maljers Jeroen Schokker Jan P. M. Mulder Rob A. A. van der Krogt 《Journal of Soils and Sediments》2007,7(1):9-16
Background, Aim and Scope
Coastal and river plains are the surfaces of depositional systems, to which sediment input is a parameter of key-importance.
Their habitation and economic development usually requires protection with dikes, quays, etc., which are effective in retaining
floods but have the side effect of retarding sedimentation in their hinterlands. The flood-protected Dutch lowlands (so-called
dike-ring areas) have been sediment-starved for up to about a millennium. In addition to this, peat decomposition and soil
compaction, brought about by land drainage, have caused significant land subsidence. Sediment deficiency, defined as the combined
effect of sediment-starvation and drainage-induced volume losses, has already been substantial in this area, and it is expected
to become urgent in view of the forecasted effects of climate change (sea-level rise, intensified precipitation and run-off).
We therefore explore this deficiency, compare it with natural (Holocene) and current human sediment inputs, and discuss it
in terms of long-term land-use options.
Materials and Methods:
We use available 3D geological models to define natural sediment inputs to our study area. Recent progress in large-scale
modelling of peat oxidation and compaction enables us to address volume loss associated with these processes. Human sediment
inputs are based on published minerals statistics. All results are given as first-order approximations.
Results:
The current sediment deficit in the diked lowlands of the Netherlands is estimated at 136 ± 67 million m3/a. About 85% of
this volume is the hypothetical amount of sediment required to keep up with sea-level rise, and 15% is the effect of land
drainage (peat decomposition and compaction). The average Holocene sediment input to our study area (based on a total of 145
km3) is ~14 million m3/a, and the maximum (millennium-averaged) input ~26 million m3/a. Historical sediment deficiency has
resulted in an unused sediment accommodation space of about 13.3 km3. Net human input of sediment material currently amounts
to ~23 million m3/a.
Discussion:
As sedimentary processes in the Dutch lowlands have been retarded, the depositional system's natural resilience to sea-level
rise is low, and all that is left to cope is human countermeasure. Preserving some sort of status quo with water management
solutions may reach its limits in the foreseeable future. The most viable long-term solutions therefore seem a combination
of allowing for more water in open country (anything from flood-buffer zones to open water) and raising lands that are to
be built up (enabling their lasting protection). As to the latter, doubling or tripling the use of filling sand in a planned
and sustained effort may resolve up to one half of the Dutch sediment deficiency problems in about a century.
Conclusions:
Conclusions, Recommendations and Perspectives. We conclude that sediment deficiency – past, present and future – challenges
the sustainable habitation of the Dutch lowlands. In order to explore possible solutions, we recommend the development of
long-term scenarios for the changing lowland physiography, that include the effects of Global Change, compensation measures,
costs and benefits, and the implications for long-term land-use options.
Recommendations and Perspectives:
- 相似文献
997.
Antonio M. De Ron María C. Menéndez-Sevillano Marta Santalla 《Genetic Resources and Crop Evolution》2005,51(8):883-894
The phenotypic variation found in four common bean (Phaseolus vulgaris L.) complex primitive landraces, among a group of accessions collected in Northwestern Argentina in several missions is described, with particular attention to the wide diversity found in some small areas. It is presented a hypothesis about the maintenance of such diversity in bean mixtures or complex primitive landraces that grow close to their wild relative. Wide diversity regarding to seed type and plant characteristics was displayed by the landraces MCM-SV (composed of 11 lines), MCM-292 (14 lines), MCM-298 (5 lines) and VAV-3716 (14 lines). Food uses of dry seed and fresh pod seemed to be more relevant than the aesthetic use although all of them were presumably considered by humans for centuries resulting in the current phenotypes of these complex primitive landraces. Additionally, some weedy types (intermediate between wild and domesticated types) were detected in the landracesMCM-292 and MCM-298. The four complex landraces described consisted of highly diverse mixtures and they could play a role in breeding to enlarge the genetic basis of domesticated bean varieties belonging to the Andean gene pool. 相似文献
998.
Romero C Brenes M García P García A Garrido A 《Journal of agricultural and food chemistry》2004,52(7):1973-1979
The individual evolution of phenolic compounds has been studied during the natural fermentation of black olives for the first time. Cyanidin 3-rutinoside and cyanidin 3-glucoside were the main anthocyanins identified in fresh olives, and they were not detected after 1 month of storage either in brine or in olive. The fruit colors were different when aerobic or anaerobic conditions were used and as a consequence of the different anthocyanin polymerizations that took place. At time zero, the polyphenols observed in the olive juice were hydroxytyrosol-4-beta-glucoside, oleuropein, hydroxytyrosol, tyrosol, salidroside, and verbascoside and, after 12 months, the main phenol was hydroxytyrosol. The polyphenol content in the oil phase of olives was also analyzed. The dialdehydic form of elenolic acid linked to hydroxytyrosol and tyrosol, oleuropein aglycon, and ligstroside aglycon were the main compounds found at the beginning of fermentation but were not detected after 3 months. In contrast, hydroxytyrosol, hydroxytyrosol acetate, tyrosol, and tyrosol acetate were the main polyphenols detected in the oil phase of the final product. The acid hydrolysis of the initial glucosides (in olive juice) and the aglycons (in oil phase) was, therefore, the main reaction that took place during fermentation. 相似文献
999.
Faleiro L Miguel G Gomes S Costa L Venâncio F Teixeira A Figueiredo AC Barroso JG Pedro LG 《Journal of agricultural and food chemistry》2005,53(21):8162-8168
Antilisterial activities of Thymbra capitata and Origanum vulgare essential oils were tested against 41 strains of Listeria monocytogenes. The oil of T. capitata was mainly constituted by one component, carvacrol (79%), whereas for O. vulgare three components constituted 70% of the oil, namely, thymol (33%), gamma-terpinene (26%), and p-cymene (11%). T. capitata essential oil had a significantly higher antilisterial activity in comparison to O. vulgare oil and chloramphenicol. No significant differences in L. monocytogenes susceptibilities to the essential oils tested were registered. The minimum inhibitory concentration values of T. capitata essential oil and of carvacrol were quite similar, ranging between 0.05 and 0.2 microL/mL. Antioxidant activity was also tested, the essential oil of T. capitata showing significantly higher antioxidant activity than that of O. vulgare. Use of T. capitata and O. vulgare essential oils can constitute a powerful tool in the control of L. monocytogenes in food and other industries. 相似文献
1000.
Chun-Lung Su Ian A. Gardner Wesley O. Johnson 《Journal of Agricultural, Biological & Environmental Statistics》2007,12(2):250-271
We develop Bayesian models to estimate cluster-level test characteristics, sensitivity, specificity, prevalence, and predictive
values, based on four different sampling schemes: a single test case and three sequential test cases. The corresponding cluster-level
characteristics are calculated and compared for different sample sizes, sampling schemes, individual-level sensitivities,
specificities, and cut-off values. We compared posterior estimates of individual-level and cluster-level characteristics for
these four sampling schemes with simulated data. Two illustrations, one for Johne’s disease in cattle and another for Salmonella
in pig herds, are used to demonstrate application of the methods. 相似文献