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51.
ABSTRACT Pasteuria penetrans is a bacterial parasite of root-knot nematodes that shows great potential as a biocontrol agent. Scanning and transmission electron microscopy were used to study the ultrastructure, morphology, and sporogenesis of four isolates of P. penetrans. The effects of different Meloidogyne spp. and tobacco cultivars on sporangium size and morphology of endospores attached to the cuticle of second-stage juveniles (J2) of root-knot nematodes also were investigated. The P. penetrans isolates and their origins were P-20 from M. arenaria race 1 in Levy County, FL; P-100 from Meloidogyne sp. in Pasco County, FL; B-4 from Pratylenchus scribneri in Seminole County, FL; and P-120 from Meloidogyne spp. in Alachua County, FL. Sporangia of the four isolates were identical morphologically and similar in their dimensions, ranging from 2.39 to 3.42 mum in diameter and from 1.38 to 2.38 mum in height. Different Meloidogyne spp. and tobacco cultivars had no effect on sporangium size. Endospores attached to J2 were visualized in three forms: endospores retaining the sporangium wall, endospores covered with a thin exosporium, and endospores without covering. Sporogenesis of P. penetrans was similar to that of other gram-positive bacteria and generally matched the seven-stage scheme reported for Bacillus thuringiensis. 相似文献
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T. Ueno S. G. Stevenson K. R. Preston M. J. Nightingale B. M. Marchylo 《Cereal Chemistry》2002,79(1):155-161
A simple, highly efficient and reproducible two‐step extraction procedure using dilute acetic acid without (AN) and then with sonication (AS) has been developed for the fractionation of wheat flour protein. Approximately 97% of total protein was extracted from a Canadian hard red spring wheat flour; an additional 1.2% protein could be recovered by further extraction with 1% DDT and 50% 1‐propanol (AR). Size‐exclusion HPLC (SE‐HPLC) and flow field‐flow fractionation (flow FFF) showed that the AN extract, which accounted for most of the total extractable protein (AN + AS + AR), consisted primarily of monomeric protein. The AS extract was composed primarily of polymeric proteins. Flow FFF showed that AN polymeric protein, including that eluting at the SE‐HPLC void volume, showed smaller Stokes diameters than AS polymeric protein. Flow FFF profiles of AS SE‐HPLC subfractions showed that the void volume subfraction contained monomeric and small polymeric protein in addition to large polymeric protein, indicating formation of larger complexes through interaction between some or all of the components. AN and AS extracts, as well as SE‐HPLC and flow FFF fractions thereof, showed a fairly wide range of values among 12 Canadian hard red and white spring wheat cultivars. The proportion of total protein in the AS extract and in the larger sized polymeric protein fractions from SE‐HPLC and flow FFF were highly positively correlated to farinograph mixing time. 相似文献
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Resistance to the acetyl‐coenzyme A carboxylase (ACCase)‐inhibiting herbicides in Lolium rigidum is widespread in grain cropping areas of South Australia. To better understand the occurrence and spread of resistance to these herbicides and how it has changed with time, the carboxyl transferase (CT) domain of the ACCase gene from resistant L. rigidum plants, collected from both random surveys of the mid‐north of Southern Australia over 10 years as well as stratified surveys in individual fields, was sequenced and target site mutations characterised. Amino acid substitutions occurring as a consequence of these target site mutations, at seven positions in the ACCase gene previously correlated with herbicide resistance, were identified in c. 80% of resistant individuals, indicating target site mutation is a common mechanism of resistance in L. rigidum to this herbicide mode of action. Individuals containing multiple amino acid substitutions (two, and in two cases, three substitutions) were also found. Substitutions at position 2041 occurred at the highest frequency in all years of the large area survey, while substitutions at position 2078 were most common in the single farm analysis. This study has shown that target site mutations leading to amino acid substitutions in ACCase of L. rigidum are widespread across South Australia and that these mutations have likely evolved independently in different locations. The results indicate that seed movement, both within and between fields, may contribute to the spread of resistance in a single field. However, over a large area, the independent appearance and selection of target site mutations conferring resistance through herbicide use is the most important factor. 相似文献
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T. Reg Preston 《Tropical animal health and production》2009,41(7):1071-1080
Responding to the challenges posed by global warming, peak oil and biofuels will require a paradigm shift in the practice
of agriculture and in the role of live stock within the farming system. Farming systems should aim at maximizing plant biomass
production from locally available diversified resources, processing of the biomass on farm to provide food, feed and energy
and recycling of all waste materials. The approach that is the subject of this paper is that the generation of electricity
can be a by-product of food/feed production. The concept is the fractionation of biomass into inedible cell wall material
that can be converted to an inflammable gas by gasification, the gas in turn being the source of fuel for internal combustion
engines driving electrical generators. The cell contents and related structures such as tree leaves are used as human food
or animal feed. As well as providing food and feed the model is highly appropriate for decentralized small scale production
of electricity in rural areas. It also offers opportunities for sequestration of carbon in the form of biochar the solid residue
remaining after gasification of the biomass. 相似文献
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B. Glencross S. Tabrett S. Irvin N. Wade M. Anderson D. Blyth D. Smith G. Coman N. Preston 《Aquaculture Nutrition》2013,19(2):128-138
Selected (G8) and wild‐type (W) genotypes of black tiger shrimp (Penaeus monodon) juveniles (initial weight G8 = 9.14 ± 0.36 g per animal and W = 8.44 ± 0.10 g per animal) were fed either of two diet types in a clear‐water tank trial to examine the effects of diet type and genetics on growth and feed utilization parameters. Animals were fed twice daily at one of the five ration levels from starvation to apparent satiety. All uneaten feed was accounted for and moults removed. Starved animals were measured after 3 weeks; those fed were measured at both three and 6 weeks. Diet type varied by protein content, raw material choice and the presence [high‐specification diet (HSD)] or absence [low‐specification diet (LSD)] of bioactive substances. At the end of the study, faecal samples were also collected to determine the digestible protein and energy content of each diet by each genotype. Whole animal protein and energy content were also assessed from samples from the initial populations and those from each tank. Growth after 6 weeks of those animals fed to satiety showed that the G8 animals fed the HSD diet had grown at a rate of 2.56 g week?1, significantly faster than any other treatment. Those G8 animals fed the LSD diet (1.81 g week?1) had grown significantly faster than the W animals fed the HSD diet (1.25 g week?1), while those W animals fed the LSD diet (0.61 g week?1) grew the slowest. Using the data from the varying ration levels, we were able to define that the growth gains of the G8 animals were achieved not only by a greater appetite, but also through lower maintenance energy costs (29 versus 57 kJ kg?0.8 day?1) and a more efficient energy conversion (19.5% versus 11.6% when fed the HSD diet). Use of a low‐specification diet with the G8 and W shrimps limited their growth and impaired their potential as demonstrated by a curvilinear response of growth to intake. By comparison, those shrimp fed the HSD diet had a relatively linear growth response to intake. 相似文献