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991.
The use of silvopasture systems on farms in the Northeastern United States has never been documented. Our objective was to gather baseline data to describe silvopasture practices and perspectives in the Northeastern United States. To accomplish this, we investigated the structure, management of, and reasons for use of silvopastures in New York state and New England through a series of interviews and inventories on 20 farms purposefully chosen as practicing silvopasture. Thematic content analysis was conducted to summarize interview results and identify trends related to silvopasture practices. Three farmers in this study had been practicing silvopasture on their farms over 30 years; the rest were new to silvopasture in the past 10 years. Only three of 20 farmers interviewed in this study had experience practicing silvopasture prior to implementing it on their farms. Forest conversion to silvopasture was the primary starting point for silvopastures observed on regional farms. Orchard, open field edge, outdoor living barn, and plantation silvopastures were also documented on multiple farms. Shade and a desire to maximize use of farm woodlands were primary reasons for silvopasture utilization. This research provides evidence that silvopastures are being used to diversify regional farms. For the practice to be advanced in the region further research is needed on the topic.  相似文献   
992.
Cadmium (Cd) contamination in soil and its movement into food chain through vegetable dietary poses a risk to human health. A pot experiment was conducted to investigate the effect of humic acid (HA) and two cultivars of Brassica rapa ssp. chinensis L. (pak choi) with differing Cd accumulation abilities on Cd accumulation in different Cd contaminated Ferralsol, Histosol and Luvisol soils. The results showed that HA significantly increased soil pH and cation exchange capacity in Ferralsol (acidic) and Histosol (neutral) soils. HA was more effective in Ferralsol and Histosol soil in reducing bioavailable Cd and its accumulation in both cultivars. Low and high Cd accumulating cultivars combined with HA effectively reduced shoot Cd concentration by 7–34% and 19–35% in Histosol soil, whereas 22–34% and 11–26% in Ferralsol soil, respectively. However, no such reduction was observed for Cd accumulation and bioavailability in Cd-contaminated Luvisol (alkaline) soil. Application of HA enhanced shoot dry biomass in both cultivars grown in Histosol and Ferralsol soils. Therefore, the HA amendment combination with low Cd accumulating cultivars of pak choi could be an effective method for phytostabilization and reduce health risks associated with consuming this vegetable grown in Cd-contaminated acidic and neutral pH soils.  相似文献   
993.
The present study aims at identifying potentially high-yielding testcross maize hybrids using different selection indices that consider agronomic traits other than grain yield alone. Forty-one (41) testcross hybrids developed from 20 elite drought-tolerant maize inbred lines and two inbred testers plus three hybrid checks were evaluated in the rainy seasons of 2013 and 2014 in Ogbomoso in the derived savanna agroecological zone of Nigeria. Hybrids were planted in each year in 11 × 4 lattices with two replications. Testcross hybrids and checks exhibited significant differences for all measured traits except ear height, husk cover and number of ears per plant. Grain yield of hybrids and checks averaged over the 2 years varied from 3117 to 8393 kg ha?1 with a mean of 5935 kg ha?1. Top 11 hybrids produced vigorous plants, each yielding >7000 kg ha?1. Base index and multivariate index methods identified EXL11 × 9071 whereas base index and Smith–Hazel selection index methods identified EXL18 × 9071 as superior hybrids at 5% selection intensity. These hybrids will be considered for advanced breeding program and release to farmers as high-yielding drought-tolerant hybrid maize varieties in the increasingly drought-prone derived savanna agroecology of Nigeria.  相似文献   
994.
Titanium oxide (TiO2) and zinc oxide (ZnO) composite structured nanoparticles were prepared by combining a sol-gel process and a solvothermal method. Titanium (IV) isoproxide (TTIP), used as a TiO2 precursor, was dissolved in a colloidal ZnO nanoparticle solution synthesized by the sol-gel method, and TiO2 was synthesized via solvothermal synthesis onto the ZnO nanoparticles. The effects of reaction conditions such as pH, reaction temperature, and reaction time on the morphology of the composite nanoparticles and the ultraviolet (UV) absorbance of their polymer composite films were investigated. The UV absorption of the poly(vinyl alcohol) (PVA) composite film with TiO2-coated ZnO nanoparticles was higher than that of the TiO2, ZnO, and ZnO-coated TiO2 composite films. The reaction pH was found to have the strongest influence on the UV absorbance of the PVA/(TiO2/ZnO) composite film. A pH of 7.0, reaction temperature of 250 °C, and reaction time of 24 h were the optimum conditions for UV absorption.  相似文献   
995.
Past investigations have suggested that both UGPase and AcInv activities can be used as markers to screen genetically diverse potato clones for cold induced sweetening resistance (CIS-R). The goal of this study was to define their cooperative interaction in regulating sweetening. Inter- and intra-ploidy hybridizations of good (G) and poor (P) processing 24 or 48 chromosome potato clones were used to create 24 potato families. Potatoes were field grown and 460 progeny (≤20 each family) were stored for five months in the cold (4 C). Tubers from each progeny plant were evaluated for cold induced sweetening resistance (CIS-R) and correlated with the percentage of A-II isozymes of UDP-glucose pyrophosphorylase (UGPase; EC 2.7.7.9); and acid invertase activity (AcInv; EC 3.2.1.26). Each progeny was given a CIS-R score of 1–10 (1-most resistance, 10 least resistance). The families were grouped into four classes based on (1) high or low AcInv activity (low being a SA of 0.30 or less) (2) high or low percentage of A-II isozymes (low being 50% or less), and (3) CIS-R score. In high AcInv families, CIS-R was low regardless of the percentage of A-II isozymes present. In low AcInv activity families, there was a trend for average chip color to improve as the percentage of A-II isozymes increased from 0% to 40%. This increase in CIS-R in low AcInv families is likely due to the kinetic properties unique to the A-II forms of UGPase (principally UGP5) which limit the formation of sucrose via sucrose-6-phosphate synthase (SPS; EC 2.4.1.14). Lower concentrations of sucrose can lead to a decrease in reducing sugar production via vacuolar AcInv and lighter chip and fry colors. In selecting tetraploid parents, for the development of processing potato clones with improved CIS-R, it is recommended they have a basal AcInv SA of 0.30 or less and have A-II isozymes of UGPase.  相似文献   
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999.
Anthropogenic changes to the Great Plains rivers of North America have had a large, negative effect on a reproductive guild of pelagic‐broadcast spawning (PBS) cyprinid fishes. The group is phylogenetically diverse, with multiple origins of the PBS mode. However, because of incomplete life‐history information, PBS designation often relies only on habitat and egg characteristics. We identified 17 known or candidate PBS fishes and systematically synthesized the literature on their biology and ecology in relation to major threats to persistence. Research output on an individual species was unrelated to conservation status, but positively correlated with breadth of distribution. The PBS species have opportunistic life‐history strategies and are typically short‐lived (generally 1–3 years) fishes. Many PBS species have truncated ranges showing declines in both distribution and abundance, especially those endemic to the Rio Grande catchment. Fundamental habitat associations are unknown for many species, particularly regarding seasonal shifts and early life stages. Critical thermal tolerances have been quantified for five PBS species and are generally >35°C. Turbidity and salinity changes are linked to responses at multiple life stages, but information is lacking on interactions between water quality and quantity. Hydrologic alteration appears to be a primary threat to PBS species, through complex interactions with landscape fragmentation, and habitat change. We highlight areas where scientific and management communities are lacking information and underline areas of potential conservation gain.  相似文献   
1000.
Buried horizons and lenses in riparian soil profiles harbor large amounts of carbon relative to the surrounding soil horizons. Because these buried soil horizons, as well as deep surface horizons, frequently lie beneath the water table, their impact on nitrogen transport across the terrestrial–aquatic interface depends upon their frequency and spatial distribution, and upon the lability of associated organic matter. We collected samples of 51 soil horizons from 14 riparian zones Rhode Island, USA, where soil profiles are characterized by glacial outwash and alluvial deposits. These soil samples came from as deep as 2 m and ranged in carbon content from <1% to 44% in a buried O horizon 54–74 cm deep. We used these samples to: (1) determine the extent to which carbon in buried horizons, and deep surface horizons, is potentially microbially available; (2) identify spatial patterns of carbon mineralization associated with surface and buried horizons; and (3) evaluate likely relationships between soil horizon types, chemical characteristics and carbon mineralization. Carbon mineralization rates associated with buried horizons during anaerobic incubations ranged from 0.0001 to 0.0175 μmol C kg soil?1 s?1 and correlated positively with microbial biomass (R=0.89, P<0.0001, n=21). Excluding surface O horizons from the analysis, carbon mineralization varied systematically with horizon type (surface A, buried A, buried O, lenses, A/C, B, C) (P<0.05) but not with depth or depth x horizon interaction (overall R2=0.59, P<0.0005, n=47). In contrast to this result and to most published data sets, 13C-to-12C and 15N-to-14N ratios of organic matter declined with depth (13C?26.9 to ?29.3 per mil, 15N+5.6 to ?0.8 per mil). The absence of a relationship between horizon depth and C availability suggests that carbon availability in these buried horizons may be determined by the abundance and quality of organic matter at the time of horizon formation or burial, rather than by duration since burial, and implies that subsurface microbial activity is largely disconnected from surface ecosystems. Our results contribute to the emerging view that buried horizons harbor microbially available C in quantities relevant to ecosystem processes, and suggest that buried C-rich soil horizons need to be incorporated into assessments of the depth of the biologically active zone in near-stream subsurface soils.  相似文献   
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