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971.
Mitochondrial 16S rRNA sequences from morphological validated grouper (Epinephelus aeneus, E. caninus, E. costae, and E. marginatus; Mycteroperca fusca and M. rubra), Nile perch (Lates niloticus), and wreck fish (Polyprion americanus) were used to develop an analytical system for group diagnosis based on two alternative Polymerase Chain Reaction (PCR) approaches. The first includes conventional multiplex PCR in which electrophoretic migration of different sizes of bands allowed identification of the fish species. The second approach, involving real-time PCR, produced a single amplicon from each species that showed different Tm values allowing the fish groups to be directly identified. Real-time PCR allows the quick differential diagnosis of the three groups of species and high-throughput screening of multiple samples. Neither PCR system cross-reacted with DNA samples from 41 common marketed fish species, thus conforming to standards for species validation. The use of these two PCR-based methods makes it now possible to discriminate grouper from substitute fish species.  相似文献   
972.
Olive oil mill wastewaters (OMWs) show significant polluting properties due to their content of organic substances, and because of their high toxicity toward several biological systems. Wastewaters' toxicity has been attributed to their phenolic constituents. A chemical study of wastewaters from a Ligurian oil mill characterized phenolic products such as 1,2-dihydroxybenzene (catechol), derivatives of benzoic acid, phenylacetic acid, phenylethanol, and cinnamic acid. The OMWs were fractioned by ultrafiltration and reverse osmosis techniques and tested for toxicity on aquatic organisms from different trophic levels: the alga Pseudokirchneriella subcapitata (formerly known as Selenastrum capricornutum); the rotifer Brachionus calyciflorus; and two crustaceans, the cladoceran Daphnia magna and the anostracan Thamnocephalus platyurus. The fraction most toxic to the test organisms was that from reverse osmosis containing compounds of low molecular weight (<350 Da), and this was especially due to the presence of catechol and hydroxytyrosol, the most abundant components of the fraction.  相似文献   
973.
The free volatiles, as well as those released from the glycosidically bound forms by enzyme hydrolysis, have been analyzed to chracterize young Tannat wines from two successive vintages. The Tannat wine showed some aroma profile peculiarities detected in the free forms but, above all, in the bound fraction for the level and profile of the norisoprenoidic fraction. Among the free volatile compunds, a rather low content of C(6) alcohols with a prevalence of cis-3-hexen-1-ol on the trans form and sometimes a remarkable level of trans-2-hexen-1-ol seem to be typical for the variety. C(13)-norisoprenoidic and monoterpenic volatiles made up approximately 42% of the total level of the volatiles observed in the glycosidase enzyme-released fraction. The other volatiles were C(6) alcohols (6%) and benzenoid compounds (51%). The dominating monoterpene alcohols were the cis and trans isomers of 3,7-dimethyl-1,6-octadiene-3,8-diol (8-hydroxylinalool). The C(13)-norisoprenoid pattern was composed by 3-hydroxy-beta-damascone, 3-oxo-alpha-ionol, vomifoliol, 4-oxo-beta-ionol, 3-oxo-7,8-dihydro-alpha-ionol, 4-oxo-7,8-dihydro-beta-ionol, grasshopper ketone, and 7,8-dihydrovomifoliol.  相似文献   
974.
Seasonal variation of biomass, photosynthetic pigments and C and N contents of the cyanobacterial blooms developed during the crop cycles of 1998, 1999 and 2000 at two locations in Valencian rice fields (Spain) were studied to find their potential contribution to soil fertility. Blooms of Gloeotrichia sp., Gloeocapsa sp., Microchaete sp., and Nostoc sp. were small and dispersed and appeared only for a few weeks in the experimental fields of the Tancat de Malta location during the crop season of 1998. The biomass of these blooms ranged from 4.4 to 12.8 mg dry wt cm–2. A bloom of Anabaena sp. was found in the same location during most of the crop cycles of 1998 and 1999, covering up to 80% of the experimental fields. The biomass of this bloom ranged from 2.7 to 11.4 mg dry wt cm–2. In the moment of its maximal extension (July 1998) we estimate a total biomass of 2,100 kg dry wt for this bloom, equivalent to 420 kg dry wt ha–1. In the Sueca location a bloom of Microchaete sp. was observed in August 1999 and during most of the crop cycle of 2000, when it covered a wide area (60–70%) of the experimental field. The biomass of this bloom ranged from 0.9 to 5.6 mg dry wt cm–2. Carbon contents of the blooms ranged from 150 to 310 g mg–1 dry wt and N contents ranged from 11 to 30.2 g mg–1 dry wt. Taking into account their N content and their extension we estimate that the incorporation of cyanobacterial blooms could add 4–12 kg N ha–1 to soil. From an agronomical point of view this means that, in spite of their impressive aspect, cyanobacterial blooms can only fulfill a small proportion of the N requirements of rice plants.  相似文献   
975.
The genetic diversity of 10 commercial cultivars of common beans, developed in Northern Argentina was analyzed based on RAPD markers. Sixteen primers were assayed and among them only 4 showed polymorphisms. A similarity matrix was generated by applying three different association coefficients, Simple Matching, Jaccard and Dice. By the UPGMA method dendrograms were generated and also the principal coordinate analysis was performed. The similarity values found were higher than 40% suggesting that genetic diversity is low. Both cluster analysis and principal coordinates analysis associated commercial cultivars either to the Andean or the Mesoamerican gene pool.  相似文献   
976.
The volumetric ring and the computerized tomography (CT) techniques were applied to study soil bulk density, in order to understand the compaction of an Albaqualf soil (Planosol) of the Rio Grande do Sul State, Southern Brazil (latitude 31°52′00″S and Longitude 52°21′24″W). Among six different tillage systems and crop rotations the greatest soil bulk density was measured for the continuous irrigated rice crop system and the lowest for the no-tillage treatment under rye grass straw. The CT method enabled the measurement of bulk density variations in the soil profile and indicated critical zones not observed by the volumetric ring method that measures only the mean sample soil bulk densities. A meaningful correlation between soil bulk densities measured by both methods was found, although the CT method presented more reliable results in comparison to the volumetric ring method. A 3% variation in bulk density was observed due to method intrinsic errors, probably also correlated to different samples sizes.  相似文献   
977.
Biological [dynamic respiration index (DRI); chemical humification indexes: humification index (HI), degree of humification (DH) and humification rate (HR); and thermoanalytical (thermostability index, R1 and a labile fraction)] indexes were used to assess compost stability of 15 end products. By use of these three techniques independent assessment of compost stability was made possible. Evidence of unstable materials was found where labile, easily biodegradable, and non-humified organic fractions were present. The DRI was used as a reference index for biological stability, and no significant correlation was observed between DRI and the humification indices (HI, DH, HR) and the thermogravimetry index (R1). On the other hand, significant correlation was observed for DRI vs. non-humified carbon (NHC), which was determined using the chemical method and the labile fraction determined by thermogravimetry, as well as for NHC vs. “labile fraction”. These fractions represent labile, easily biodegradable, and non-humified organic matter. Significant correlations were also observed between the three above mentioned measurements and TEC, suggesting that this fraction is mainly formed of the easily degradable organic fraction. These results suggest that the integrated use of biological, chemical, and thermoanalytical methods could represent a useful tool in differentiating stabilized composts from non-stabilized ones, and it could provide more reliable information for both managerial and sanitary health aspects involved in good agricultural practice.  相似文献   
978.
There is no generally accepted method for determination of the amounts of iron and manganese in table olives. Application of flame atomic absorption spectrometry to the analysis of both elements has been examined to validate a method that may be used by the industry's quality control laboratory as well as by the laboratories of regulatory agencies. The method has detection limits of 0.106 and 0.022 mg/L and quantification limits of 0.271 and 0.057 mg/L, for Fe and Mn, respectively, referred to the solution to be measured. There was no significant effect due to the matrix, but a slight bias due to the presence of Ca has been detected. Recoveries were excellent, and the method was robust. Influence of operator, HCl and Mg salt compounds, calcination equipment, or dates on results was not found. Relative errors were, in general, below 4% for both cations, and repeatability was below 3.43 and 0.38 mg/kg of olive paste for Fe and Mn, respectively. The method is proposed for the analysis of Fe and Mn in ripe olives and table olives in general.  相似文献   
979.
Effect of emergent vegetation on the population dynamics of phytoplankton community in Matsumi-ike Bog, a typical bog at the climax stage of limnological succession, was studied. The emergent vegetation grew until August and then withered and collapsed mainly during December and January, supplying the debris of emergent plants into the water column. Population density of the predominant phytoplankton showed sinusoidal fluctuation affected primarily by the water temperature, with various lag phases due to the function of other environmental factors. Shading by the emergent vegetation shifted the initiation of phytoplankton fluctuation earlier. This fluctuation patterns was most obvious among those phytoplankton contain chlorophyll-a and -b, but non -a and-c. The population dynamics were also compared with that of Matsumi-ike Bog at premature stages without (8 yr ago) or with littoral vegetations (3 yr ago). The population density of phytoplankton with chlorophyll-b decreased but those with chlorophyll-c increased, due to the shading effect of the emergent vegetation with the limnological succession of the bog. At the climax of succession, the dynamic state of phytoplankton community has become more stable.  相似文献   
980.
Under a Mediterranean climate, denitrification losses were quantified for 2 years on a sandy loam soil with an irrigated maize crop. The effect of pig slurry application at two different rates (165 and 495 kg N ha–1, respectively, for PS1 and PS3) was compared with that of urea (U) applied at 165 kg N ha–1 and with a control treatment (P0) without fertilizer. After application, the denitrification rate (DR) increased in PS1 and PS3 respect to P0 and decreased to the levels of the control treatment after 5 days. In July and August (the irrigation period) the DR increased considerably in all treatments with maximum values for the PS3 treatment (0.134 g N m–2 day–1 in the first year and 0.147 g N m–2 day–1 in the second year). The differences in DRs between each treatment could be explained by the pattern of water filled pore space, NO3 concentration of the soil solution and the soil temperature during the maize growing season. In the first year denitrification losses in the 0–10 cm layer were 1.90, 2.49, 2.87 and 4.00 g N m–2 for P0, U, PS1 and PS3, respectively, while in the second year the losses were 1.21, 2.28, 2.47 and 3.42 g N m–2. Finally, a simple predictive model (SOILN) was evaluated and found to give acceptable results.  相似文献   
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