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991.
This paper analyzes the interactions between land use and forest cover in the Upper Midwest, USA from 1970 to 1990. New data
are presented and interpreted to evaluate the effects of land-use changes, especially abandonment of agriculture and dispersed
development, on forest cover throughout the region. Forest-cover data were collected from Landsat satellite imagery and land
use was interpreted from aerial photographs for land parcels, based on archival maps of land ownership. In general, forest
cover increased throughout the region and throughout the period. Simultaneously, the area used for agriculture declined, much
of it being converted to natural uses, and the area of land in low density residential development increased. Forest cover
increased most rapidly on low density residential lands and in counties in which a large percentage of homes were for seasonal
use (i.e., vacation homes). The data suggest that the transformation of the region from an extractive (i.e., forestry and
agriculture) to a recreation-based service economy has played a significant role in the increasing forest cover observed throughout
the region.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
992.
We analyzed forest clearing and regrowth over a 23-year time period for 21 forest concession and management units within the
Maya Biosphere Reserve(MBR), Guatemala. The study area as a whole experienced a clearing rate of0.16%/year from 1974 through
1997. The overall clearing rate appears rather low when averaged over the entire study area over 23 years because most of
the reserve was inaccessible. However, despite the granting of legal protection to the MBR in 1990, clearing rates continued
to rise, with the highest rates occurring in the most recent time period in the analysis, 1995 to1997. Higher rates of clearing
relative to regrowth occurred in newly established communities and in the Reserve's buffer zone, where the clearing of high
forest was preferred for pasture development. Exploratory models were built and analyzed to examine the effects of various
landscape variables on forest clearing. The different units in the analysis showed different relationships of forest clearing
with variables such as forest cover type and distance to access(roads and river corridors). Where available, socio-economic
household survey data helped to explain patterns and trends observed in the time series Landsat imagery. A strong relationship
between forest clearing and distance to access was demonstrated. More clearing occurred further from roads during later time
periods as farmers moved deeper into the forest to find land to clear. Communities inside the MBR that were less dependent
on farming had forest clearing to regrowth ratios of one:one or less. These communities used fallow fields in greater proportions
than communities in the Reserve's buffer zone. General trends in clearing by forest cover type suggest a preference for clearing
high forest (bosque alto) types found on the higher elevation, better-drained soils, and fallow fields,and an avoidance of low-lying, seasonally flooded
terrain(bajos). Satellite remote sensing observations of forest clearing and regrowth patterns can provide an objective source of information
to complement socio-economic studies of the human driving forces in land cover and land use change.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
993.
Joyner PH Jones MP Ward D Gompf RE Zagaya N Sleeman JM 《American journal of veterinary research》2008,69(1):13-22
OBJECTIVE: To compare induction and recovery characteristics and cardiopulmonary effects of isoflurane and sevoflurane in bald eagles. Animals-17 healthy adult bald eagles. PROCEDURES: Anesthesia was induced with isoflurane or sevoflurane delivered in oxygen via a facemask in a crossover design with 4 weeks between treatments. Eagles were intubated, allowed to breathe spontaneously, and instrumented for cardiopulmonary measurements. Time to induction, extubation, and recovery, as well as smoothness of recovery, were recorded. RESULTS: Administration of sevoflurane resulted in a significantly quicker recovery, compared with isoflurane. Temperature, heart rate, and respiratory rate significantly decreased over time, whereas systolic (SAP), diastolic (DAP), and mean arterial blood pressure (MAP) significantly increased over time with each treatment. Temperature, heart rate, SAP, DAP, and MAP were significantly higher with isoflurane. Blood pH significantly decreased, whereas PaCO(2) significantly increased over time with each treatment. Bicarbonate and total carbon dioxide concentrations significantly increased over time with each treatment; however, there was a significant time-treatment interaction. The PaO(2) and arterial oxygen saturation increased over time with isoflurane and decreased over time with sevoflurane with a significant time-treatment interaction. Six eagles developed cardiac arrhythmias with isoflurane, as did 4 with sevoflurane anesthesia. CONCLUSIONS AND CLINICAL RELEVANCE: Isoflurane and sevoflurane administration resulted in smooth, rapid induction of and recovery from anesthesia similar to other species. Isoflurane administration resulted in tachycardia, hypertension, and more arrhythmias, compared with sevoflurane. Sevoflurane was associated with fewer adverse effects and may be particularly beneficial in compromised bald eagles. 相似文献
994.
Ulcerative enteritis is a disease that typically responds well to medication. An outbreak of ulcerative enteritis that was persistent and unresponsive to treatment is described. The outbreak started in semimature birds and progressively spread to younger birds. Confounding factors leading to this persistence were a significant coccidosis problem, a feed mixing error, and suspected antibiotic resistance. Although Clostridium colinum was never isolated, a bacitracin-resistant Clostridium perfringens was cultured from affected birds. Only the combined treatment of the flocks with an anticoccidial and tylosin was effective in controlling clinical disease. Numerous other management and treatment strategies were unsuccessful in lowering the severe mortality. 相似文献
995.
996.
Christensen J McNab B Stryhn H Dohoo I Hurnik D Kellar J 《Preventive veterinary medicine》2008,83(2):170-185
We report the methods and findings of a survey of Canadian swine producers summarizing farm-types at-risk of foreign animal disease (FAD) and the routine movement of animals, semen and workers among swine farms, as observed during a 42-day period. Of the 311 producers who returned completed questionnaires, 17% represented swine-herds with no swine or semen movement on or off the farm during the 42 days, 57% were sow herds or farrow-to-finish herds with limited movement onto the farm but movement off the farm, and 26% were swine-herds with movements on and off the farm. A substantial number of premises (>50% in some provinces) with swine also kept other animal species on the same premises. We applied the empirical movement data from the survey in a stochastic simulation model to estimate the number of herds infected and the basic regional distribution of infection that could be expected to occur if the FAD was not detected and routine movements were permitted to occur up to 42 days after infection with a FAD of a single randomly selected herd. Forty-five percent of the simulations did not involve spread beyond the index farm, whereas 34.8% involved spread among five or more farms after 42 days of routine movement. 相似文献
997.
Lucas A Rodrigues Michael O Wellington J Caroline Gonzlez-Vega John K Htoo Andrew G Van Kessel Daniel A Columbus 《Journal of animal science》2021,99(2)
High dietary protein may increase susceptibility of weaned pigs to enteric pathogens. Dietary supplementation with functional amino acids (FAA) may improve growth performance of pigs during disease challenge. The objective of this study was to evaluate the interactive effects of dietary protein content and FAA supplementation above requirements for growth on performance and immune response of weaned pigs challenged with Salmonella. Sixty-four mixed-sex weanling pigs (13.9 ± 0.82 kg) were randomly assigned to dietary treatments in a 2 × 2 factorial arrangement with low (LP) or high protein (HP) content and basal (AA–) or FAA profile (AA+; Thr, Met, and Trp at 120% of requirements) as factors. After a 7-d adaptation period, pigs were inoculated with either a sterile saline solution (CT) or saline solution containing Salmonella Typhimurium (ST; 3.3 × 109 CFU/mL). Growth performance, body temperature, fecal score, acute-phase proteins, oxidant/antioxidant balance, ST shedding score in feces and intestinal colonization, fecal and digesta myeloperoxidase (MPO), and plasma urea nitrogen (PUN) were measured pre- and postinoculation. There were no dietary effects on any measures pre-inoculation or post-CT inoculation (P > 0.05). Inoculation with ST increased body temperature and fecal score (P < 0.05), serum haptoglobin, plasma superoxide dismutase (SOD), malondialdehyde (MDA), PUN, and fecal MPO, and decreased serum albumin and plasma reduced glutathione (GSH):oxidized glutathione (GSSG) compared with CT pigs (P < 0.05). ST-inoculation reduced average daily gain (ADG) and feed intake (ADFI) vs. CT pigs (P < 0.05) but was increased by AA+ vs. AA– in ST pigs (P < 0.05). Serum albumin and GSH:GSSG were increased while haptoglobin and SOD were decreased in ST-inoculated pigs fed AA+ vs. AA– (P < 0.05). PUN was higher in HP vs. LP-fed pigs postinoculation (P < 0.05). Fecal ST score was increased in ST-inoculated pigs on days 1 and 2 postinoculation and declined by day 6 (P < 0.05) in all pigs while the overall score was reduced in AA+ vs. AA– pigs (P < 0.05). Cecal digesta ST score was higher in HP vs. LP-fed pigs and were lower in AA+ compared with AA– fed pigs in the colon (P < 0.05). Fecal and digesta MPO were reduced in ST pigs fed AA+ vs. AA– (P < 0.05). These results demonstrate a positive effect of FAA supplementation, with minimal effects of dietary protein, on performance and immune status in weaned pigs challenged with Salmonella. 相似文献
998.
Daniel J. Van Rooijen Trent W. Biggs Ian Smout Pay Drechsel 《Irrigation and Drainage Systems》2010,24(1-2):53-64
The relationships between urban development, water resources management and wastewater use for irrigation have been studied in the cities of Accra in Ghana, Addis Ababa in Ethiopia and Hyderabad in India. Large volumes of water are extracted from water sources often increasingly far away from the city, while investments in wastewater management are often lagging behind. The resulting environmental degradation within and downstream of cities has multiple consequences for public health, in particular through the use of untreated wastewater in irrigated agriculture. Despite significant efforts to increase wastewater treatment, options for safeguarding public health via conventional wastewater treatment alone remain limited to smaller inner-urban watersheds. The new WHO guidelines for wastewater irrigation recognize this situation and emphasize the potential of post- or non-treatment options. Controlling potential health risks will allow urban water managers in all three cities to build on the benefits from the already existing (but largely informal) wastewater reuse, those being the contribution to food security and reduction of fresh water demands. 相似文献
999.
Tobacco anionic peroxidase often increases resistance to insects in different dicotyledonous species
Different species and strains of tobacco (Nicotiana spp), tomato (Lycopersicon esculentum) and sweetgum (Liquidambar styraciflua) that had total peroxidase activity enhanced by a few- to over 100-fold through the expression of a tobacco anionic peroxidase gene driven by a cauliflower mosaic promoter were compared with wild-type plants for resistance to relevant insects. Reduced levels of feeding were generally noticed for leaves, stems and fruit, but the age of tissues and insects influenced the response. Enhanced resistance to Helicoverpa zea and Manduca sexta were noted for tobacco and tomato, and resistance to Hyphantria cunea and Lymantria dispar were noted for sweetgum. In several cases increased mortality and/or reduced growth rates were noted for the high-peroxidase plants. Although many modes of action are possible, indirect comparisons and gravitational nutritional studies suggest peroxidase-enhanced rates of production of compounds toxic to the insects are the most important. 相似文献
1000.
Vallentin Claudia Dobers Eike Stefan Itzerott Sibylle Kleinschmit Birgit Spengler Daniel 《Precision Agriculture》2020,21(4):802-830
Precision Agriculture - Precision agriculture, as part of modern agriculture, thrives on an enormously growing amount of information and data for processing and application. The spatial data used... 相似文献