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31.
P. Monneveux M. P. Reynolds J. González Aguilar R. P. Singh W. E. Weber 《Plant Breeding》2003,122(5):379-384
The 7DL.7Ag translocation from Lophopyrum elongatum that carries Lr19, a leaf rust resistance gene, was found to be associated with a significant increase in grain yield under irrigated, disease‐free conditions, but a generally lower yield under moisture stress conditions. These studies, however, involved a limited number of genetic recipients and environments, and the effect of the translocation on physiological traits was not considered. We examined the translocation effect in six different recipient genotypes and under five environmental conditions, including drought and heat stress. The increase in grain yield under irrigated conditions was associated with a higher rate of biomass production in the 7DL.7Ag lines and may be attributed to higher sink strength. Effect of the translocation on physiological traits was noted only under heat stress and was not associated with difference in yield. Under moisture stress conditions, 7DL.7Ag lines yielded less than their corresponding recipients, possibly because of a longer growing cycle. It is concluded that the effect of the 7DL. 7Ag translocation may very much depend on the phenological adaptation of the recipient genotype and the translocation may be useful for enhancing yield, mainly under favourable conditions. 相似文献
32.
Relationship between Carbon Isotope Discrimination, Ash Content and Grain Yield in Wheat in the Peninsular Zone of India 总被引:3,自引:0,他引:3
S. C. Misra R. Randive V. S. Rao M. S. Sheshshayee R. Serraj P. Monneveux 《Journal of Agronomy and Crop Science》2006,192(5):352-362
Carbon isotope discrimination (Δ) and ash content (ma) have been proposed as indirect selection criteria for grain yield in wheat. The associations between Δ, ma and grain yield were found, however, to depend highly on the environmental conditions, the organ sampled and the time of sampling. In this study, carried out in the warm conditions of the Peninsular Zone of India, the relationship between Δ, ma and yield was studied in 30 bread and durum wheat cultivars under residual soil moisture stress (RSMS), post‐anthesis water stress (PAWS) and well‐watered (WW) conditions. Both Δ and ma were analysed in young seedlings (four‐leaf stage), leaves at anthesis and grain at maturity. Ash content was also evaluated in leaves at booting stage and maturity. Grain Δ was lower under PAWS and RSMS than under WW, while seedling and leaf Δ did not significantly differ among water regimes. Grain yield was positively correlated to grain Δ under PAWS and negatively correlated to grain ma under RSMS. A significant positive correlation was noted under RSMS and WW treatments between maLm and grain yield. Ash content in leaf at maturity consequently appears to be a useful indirect selection criterion in environments where Δ does not show any correlation with yield. The results highlight the potential of Δ and ma as indirect selection criteria for wheat yield in the conditions of the Peninsular Zone of India. 相似文献
33.
Five barley genotypes of different origins were used to examine the relationships between carbon isotope discrimination (Δ) and grain yield, yield components, dry aerial biomass and harvest index under rainfed and irrigated Mediterranean conditions. High positive correlations were found between Δ and grain yield and harvest index under both water conditions, suggesting that Δ may represent efficiency of dry matter partitioning to the grain. This hypothesis was also supported by the positive correlation found between Δ and thousand-grain weight when all the data were considered. The two drought-tolerant genotypes LM2887 and Tadmor presented the smallest difference between the two treatments for traits related to productivity as well as the highest Δ values. These results highlight the potential of Δ as a selection criterion in barley breeding in Mediterranean regions. They also encourage the study of the genetics of Δ and the identification of molecular markers linked to its variation in available progenies derived from crosses between the genotypes used in the present paper. 相似文献
34.
Summary Twenty locally-adapted but genetically diverse cowpea genotypes were grown in 17 replicated trials in a range of sites and seasons in the drylands of eastern Kenya, and the discrimination against the heavy isotope of carbon (with a mass of 13) () was determined in grain and straw samples. Most genotypes gave similar, low grain yields in the environments which subjected the plants to drought stress, but high yielding and low yielding genotypes were clearly distinct in the less stressful environments. The converse pattern was found for : the genotypes were all very similar in the non-stressful (high-) environments, but in the stressful environments, low- (drought susceptible) and high- (drought avoiding) genotypes were clearly distinct. This pattern was clearest for straw , but was also apparent for grain . The early-maturing genotypes, which escaped terminal drought, were generally those with the most stable and highest , but in the case of straw there were statistically significant deviations from this relationship. It is concluded that provides a reliable measure of the specific response of cowpea genotypes to drought, which may be of value in breeding programs provided that carbon isotope discrimination can be measured reasonably economically. 相似文献
35.
36.
The present study focuses on the microbial recalcitrance of pyrogenic organic material (PyOM) on a molecular scale. We performed microcosm incubation experiments using 13C- and 15N-enriched grass-derived PyOM mixed with a sub soil material taken from a Haplic Cambisol. Solid-state 13C and 15N NMR studies were conducted to elucidate the humification processes at different stages of PyOM degradation. The chemical structure of the remaining PyOM after incubation was clearly different from the initial pyrogenic material. The proportion of O-containing functional groups was increased, whereas that of aryl C and of N-containing heterocyclic structures had decreased, probably due to mineralisation and conversion to other C and N groups. After 20 months of incubation the aryl C loss reached up to 40% of the initial amount and up to 29% of the remaining PyOM C was assigned to carboxyl/carbonyl C and O-aryl C. These reactions alter the chemical and physical properties of the char residue and make it more available for further microbial attack but also for adsorption processes. Our study presents direct evidence for the degradation of N-heterocyclic domains in charred plant remains adding new aspects to the understanding of the N cycling in fire-affected ecosystems. 相似文献
37.
Owing to the continuously increasing concentration of atmospheric CO2, it has become a priority to understand if soil organic matter (SOM) will behave as a sink or a source of CO2 under future environmental changes. Although many studies have addressed this question, a clear understanding is still missing, particularly with respect to long-term responses. In this study, we quantified soil C stores and dynamics in relationship to soil aggregation and pool composition in a Californian chaparral ecosystem exposed for 6 years to a gradient of atmospheric CO2 concentrations, ranging from pre-industrial levels 250 to 750 μl l−1 CO2. Fossil fuel-derived CO2 depleted in 13C was used for the fumigation, thus providing a tracer of C input from the vegetation to the soil.Long-term CO2 exposure invariably affected soil aggregation, with a significant decrease in the macroaggregate fraction at highest CO2 levels relative to the other two size fractions (i.e. microaggregates and silt and clay). This soil structural change most likely reduced the stability and protection of SOM, and C content generally decreased in most fractions over the CO2 treatments, and induced faster turnover of recently fixed C at high CO2 levels. The strongest response was found in the C content of the microaggregates, which decreased significantly (P<0.05) with rising levels of CO2. We conclude that increasing atmospheric CO2 concentrations will decrease soil C in chaparral ecosystems, and that the microaggregate fraction is the most responsive to increasing concentrations of atmospheric CO2. 相似文献
38.
The origin of carbonate accumulations in termite mounds is a controversial issue. This study is an attempt to elucidate the processes of carbonate precipitation in Macrotermes mounds built on Ferralsols in Upper Katanga, D.R. Congo, whereby a differentiation between pedogenic and inherited carbonates is considered. Carbonate features were investigated for a 9 m deep termite-mound profile, and for an 18 m wide cross-section through a termite mound and the adjacent soil, using field and laboratory techniques. Field evidence for a pedogenic origin includes morphological type (soft powdery materials, nodules, and coatings on ped surfaces) and distribution patterns of the carbonates. Thin-section studies reveal that the carbonates occur predominantly as impregnative orthic nodules and less commonly as coatings, both clearly pedogenic; calcareous pellets are interpreted as locally reworked pedogenic carbonates. X-ray diffraction (XRD), scanning electron microscopy/energy dispersive X-ray spectrometry (SEM-EDS) and stable isotope (δ13C) analyses show that all isolated carbonate features consist of high-Mg calcite (4.9-12.3 mol% MgCO3) with δ13C signatures ranging from − 13.2‰ to − 11.5‰. Weddellite (CaC2O4. 2H2O) is identified in a thin-section and by XRD analysis, and appears to be locally transformed into calcite. The stable isotope composition of carbon suggests that calcite precipitated in equilibrium with soil CO2 generated during decomposition of soil organic matter, and locally most likely during oxidation of oxalate. This study proves that carbonates which accumulated in Macrotermes mounds are pedogenic precipitates, whose deposition is partly related to microbial decay of organic matter, subsequently redistributed to some extent by abiotic dissolution-reprecipitation and termite activity. 相似文献
39.
本试验在实验室模拟土壤淹水条件下,研究微生物对久效磷残留及降解的影响。结果表明:在未经灭菌的土壤中,久效磷及其降解物的消失比在灭菌土壤中快,相应的回归方程为C_WT=5.4502e~(-0.0254)t,C_YT=5.8509—0.0423t,残留半衰期分别为27.3和69.2天。久效磷在淹水土壤中降解为甲醇可抽提态和不可抽提态残留物,对甲醇可抽提态残留物经TLC和红外光谱分析表明,其降解物为磷酸三酯、N-去甲基久效磷、O,O-二甲基乙烯基磷酸酯,0-去甲基久效磷,以及O,C-去甲基久效磷,但主要为磷酸三酯,其含量由母液中的5%增加到28—83%,这种降解过程,在未灭菌土壤中比在灭菌土壤中快。 相似文献
40.