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521.
S. C. Srivastava 《Biology and Fertility of Soils》1997,26(1):31-34
The microbial contribution to extractable N and P after the air-drying of eight Indian dry tropical Ultisols was quantified.
Air-drying of the soils decreased microbial biomass C by 25–53% but increased extractable N and P by 14–34% and 24–121%, respectively.
This increase in the extractable N and P was accounted for, to some extent, by microbial biomass killed due to air-drying.
Microbial biomass contributes 17–36% and 19–82% to the extractable N and P, respectively, possibly due to air-drying of the
soils. I conclude that due to contamination of microbial biomass with the available nutrients in air-dried soils, measurements
of extractable nutrients should be made on field-moist soils.
Received: 22 October 1996 相似文献
522.
The physical properties of okra seed were evaluated as a function of moisture content (m.c.). The average length, breadth and thickness of the seed varied from 5·92 to 7·30, 4·71 to 5·40 and 4·59 to 5·36 mm, respectively, as the moisture content increased from 8·16 to 87·57% d.b. The roundness and sphericity increased from 77·76 to 79·35% and 74·48 to 76·52%, respectively, with increase in moisture content from 8·16 to 19·56% d.b. and then decreased to 72·39 and 70·63%, respectively, with further increase of moisture content. In the moisture range of 8·16–87·57%, the seed volume increased from 0·067 to 0·124 cm3, 1000 seed weight, W1000 from 65·78 to 129·75 g and the angle of repose from 27·60 to 39·47°. The bulk density, true density and porosity decreased from 0·592 to 0·558 g cm−3, 1·107 to 0·986 g cm−3 and 46·34 to 43·20%, respectively, in the moisture range from 8·16 to 87·57% d.b. The static coefficient of friction increased on four structural surfaces namely, aluminium (0·390–0·484), bakelite (0·345–0·480), galvanised iron (0·368–0·493) and mild steel (0·389–0·480) as the moisture content increased from 8·16 to 87·57% d.b. 相似文献
523.
Five polymeric black tea polyphenol fractions (PBP-1-5) were isolated from a popular brand of black tea. The effect of these PBPs and epigallocatechin gallate (EGCG), a major green tea polyphenol, was studied on the formation of [(3)H]-B(a)P-derived DNA adducts in vitro, employing rat liver microsomes. PBP-1-3 inhibited microsome-catalyzed [(3)H]-B(a)P-derived DNA adduct formation in vitro in a dose-dependent manner. This inhibition was further enhanced on preincubation of microsomes with each of the PBPs. PBP-4 was not effective per se and required preincubation with microsomes to exhibit its inhibitory effect, whereas PBP-5 remained ineffective with or without preincubation with microsomes. Further investigations revealed that the observed decrease in [(3)H]-B(a)P-DNA adduct formation was due to inhibition of isozymes of CYP450s by PBPs. Overall, results suggest that polymeric black tea polyphenol fractions retain one of the chemopreventive effects exhibited by the monomeric green tea polyphenol EGCG in vitro. 相似文献
524.
Periodic variations in the concentration, deposition and canopy impact of different forms of N on annual N deposition through rainfall, throughfall and stemflow in 5 and 8 year old stands of Casuarina equisetifolia were studied. Throughfall and stemflow ranged from 70 to 76% and 5–6% of annual precipitation respectively. The total N deposition by rainfall was 11.1 kg ha−1 year−1, and by throughfall was 13.6 kg ha−1 year−1 and 16.5 kg ha−1 year−1 in 5-year-old and 8-year old plantations, respectively. The quantities of N deposited through stemflow in the two plantations were nearly identical, accounting for 1.6 kg ha−1 year−1. Observations of the monthly deposition of NH4,N, NO3-N, Kjeldahl-N and organic-N revealed that maximum deposition occurred in July and the minimum in September. Organic-N deposition was 17% less (5-year) than the rainwater content. Net deposition of N, as an effect of canopy, was 7–8.7 kg ha−1 year−1, which was added directly to the available nutrient pool of soil. 相似文献
525.
We present here a quantum Carnot engine in which the atoms in the heat bath are given a small bit of quantum coherence. The induced quantum coherence becomes vanishingly small in the high-temperature limit at which we operate and the heat bath is essentially thermal. However, the phase phi, associated with the atomic coherence, provides a new control parameter that can be varied to increase the temperature of the radiation field and to extract work from a single heat bath. The deep physics behind the second law of thermodynamics is not violated; nevertheless, the quantum Carnot engine has certain features that are not possible in a classical engine. 相似文献
526.
Haydon DJ Stokes NR Ure R Galbraith G Bennett JM Brown DR Baker PJ Barynin VV Rice DW Sedelnikova SE Heal JR Sheridan JM Aiwale ST Chauhan PK Srivastava A Taneja A Collins I Errington J Czaplewski LG 《Science (New York, N.Y.)》2008,321(5896):1673-1675
FtsZ is an essential bacterial guanosine triphosphatase and homolog of mammalian beta-tubulin that polymerizes and assembles into a ring to initiate cell division. We have created a class of small synthetic antibacterials, exemplified by PC190723, which inhibits FtsZ and prevents cell division. PC190723 has potent and selective in vitro bactericidal activity against staphylococci, including methicillin- and multi-drug-resistant Staphylococcus aureus. The putative inhibitor-binding site of PC190723 was mapped to a region of FtsZ that is analogous to the Taxol-binding site of tubulin. PC190723 was efficacious in an in vivo model of infection, curing mice infected with a lethal dose of S. aureus. The data validate FtsZ as a target for antibacterial intervention and identify PC190723 as suitable for optimization into a new anti-staphylococcal therapy. 相似文献
527.
528.
We examined dendritic protein synthesis after a prolonged blockade of action potentials alone and after a blockade of both action potentials and miniature excitatory synaptic events (minis). Relative to controls, dendrites exposed to a prolonged blockade of action potentials showed diminished protein synthesis. Dendrites in which both action potentials and minis were blocked showed enhanced protein synthesis, suggesting that minis inhibit dendritic translation. When minis were acutely blocked or stimulated, an immediate increase or decrease, respectively, in dendritic translation was observed. Taken together, these results reveal a role for miniature synaptic events in the acute regulation of dendritic protein synthesis in neurons. 相似文献
529.
V. N. Pandey A. K. Srivastava 《Plant foods for human nutrition (Dordrecht, Netherlands)》1993,43(3):241-245
A simple method for coagulating proteins in aqueous leaf extract, through microbial fermentation, has been reported. The Leaf Protein Concentrate (LPC) obtained through this fermentation has been compared with those obtained through conventional heat coagulation methods to show that the former improves the yield and nutritional quality of LPC. 相似文献
530.
V. N. Pandey A. K. Srivastava 《Plant foods for human nutrition (Dordrecht, Netherlands)》1991,41(3):247-251
Seed protein concentrates (SPC) were extracted from 4 leguminous species and the extractabilities of total N (nitrogen), protein N and SPC determined. In addition, composition, calorie value andin vitro enzymatic digestibility of these SPCs was analysed. Results indicate the promising nutritional potential of these SPCs. 相似文献