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171.
Summary The Castellani's Method for the preservation of Sclerotium rolfsii in sterile distilled water was tested. Culturing on Potato Dextrose Yeast extract (PDY) slants, the current system used, was also evaluated. Preservation of sclerotia according to the Castellani's method allowed the strain survival for more than two years. Comparing with the strain periodically activated, a critical decrease (about 80%) in -glucan synthesizing capacity was detected for mycelium preserved either on PDY slants or in water. Activation of stored sclerotia followed by subculturing in liquid Production Medium (PM) allowed preparation of homogeneous suspensions for batch fermentations, and scleroglucan concentrations achieved were similar to those with the strain periodically activated. 相似文献
172.
Jacqueline S. Knight Francisco Madueño Simon A. Barnes John C. Gray 《Molecular biotechnology》1996,6(3):335-345
The levels of individual photosynthetic proteins can be independently decreased by theAgrobacterium-mediated transformation of plants with antisens RNA constructs. Protocols for the introduction of such constructs intoAgrobacterium, theAgrobacterium-mediated transformation of tobacco leaf disks, and the screening and analysis of the transgenic plants produced are described. 相似文献
173.
174.
Howard J. Williams Isabel Sattler Guillermo Moyna A. Ian Scott Alois A. Bell S. Bradleigh Vinson 《Phytochemistry》1995,40(6):1633-1636
Major sesquiterpene components of oil of Texas Race Stock 810 of Gossypium hirsutum were - and β-selinene. This is the seventh cyclic terpene type found to date in this genus. Both - and β-selinene, along with aromadendrene, were found but only as minor components of extracts of several domestic cultivars of G. hirsutum. 相似文献
175.
176.
The effect of heating and autoclaving on extractable nitrogen, N mineralisation and C metabolism was studied by heating five forest soils in the laboratory, simulating the range of effects of heat due to bushfire. Top soil (0–5 cm) was heated to 60 °C, 120 °C and 250 °C for 30 minutes; unheated soil was taken as a control. Samples of the soil heated to 250 °C were also inoculated with fresh soil to accelerate the recovery of the microbial population. Soil autoclaving was carried out as another heat treatment (moist heat). Soils were analysed immediately after heating and 3 times during seven months of incubation to assess immediate and longer-term effects of heating.Extractable N (organic and mineral forms) increased after heating to 120 °C, but decreased with further heating to 250 °C suggesting the volatilisation of N. N associated with microbial biomass diminished with heating and was barely detectable after the 250 °C treatment. Microbial biomass was an important source of soluble N in heated soils, and only partly recovered during subsequent long incubation. The amount of N mineralised during incubation depended on both soil and temperature. Nitrification did not occur when soils were heated to 250 °C (with or without inoculum), or after autoclaving, demonstrating the high sensitivity of nitrifiers to heat. At the beginning of soil incubation, respiration was enhanced in heated soils (250 °C, 250 °C inoculated) and autoclaved soils, but after 30 days of incubation respiration decreased to values either similar to or lower than those in control. This respiration pattern indicated that a fraction of labile C was released by heating, which was quickly mineralised within 30 days of incubation. These results demonstrate some effects of soil heating on C and N dynamics in forest soils. 相似文献
177.
M. E. Acuña-Argüelles M. Gutiérrez-Rojas G. Viniegra-González E. Favela-Torres 《Applied microbiology and biotechnology》1995,43(5):808-814
Three extracellular pectinases were produced byAspergillus niger CH4 by submerged and solid-state fermentation, and their physicochemical and kinetic properties were studied. The highest
productivities of endo- and exo-pectinase and pectin lyase were obtained with solid-state fermentation. The kinetic and physicochemical
properties of these enzymes were influenced by the type of culture method used. All activities were very different in terms
of pH and temperature optima, stability at different pH and temperature values and affinity for the substrate (K
m values). In solid-state fermentation, all pectinase activities were more stable at extreme pH and temperature values but
theK
m values of endo-pectinase and pectin lyase were higher with respect to those activities obtained by the submerged-culture
technique. The pectin lyase activity obtained by the submerged-culture technique showed substrate inhibition but the enzyme
obtained by solid-state fermentation did not. Electrophoresis, using sodium dodecyl sulphate/polyacrylamide gel with enzymatic
extracts obtained for both culture methods, showed the same number on protein bands but some differences were found in their
electrophoretic position. The results obtained in this work suggest that the culture method (submerged or solid-state) may
be responsible for inducing changes in some of the pectinolytic enzymes produced byA. niger. 相似文献
178.
David Bueno Lluis Espinosa Marc Aureli Soriano Eduard Batlle Jaume Baguñà Rafael Romero 《Hydrobiologia》1995,305(1-3):235-240
We have produced monoclonal antibodies (mAbs) against antigens of the freshwater planarian Dugesia (G.) tigrina (Girard) using standard protocols. One of these mAbs, TCEN-49, detects an antigen (TCEN-49Ag) present in most cells of the central area of the body, including the pharynx. Labelled cells seem more related by position than by lineage, suggesting that TCEN-49Ag is involved somehow in the expression of central body positional identity. The spatial and temporal changes in TCEN-49Ag expression during growth/degrowth and regeneration have been monitored and the implications of these results are discussed. 相似文献
179.
180.
J. L. Santos M. C. Cuadrado M. Díez C. Romero N. Cuñado T. Naranjo M. Martínez 《Chromosoma》1995,104(4):298-307
Chromosomal pairing of one triploid and three tetraploid plants of rye, Secale cereale, was analyzed by electron microscopy in surface-spread prophase I nuclei and compared with light microscopic observations of metaphase I cells. Prophase I is characterized by: (i) the weak alignment showed by the three or four unsynapsed or partially homologous synapsed axes; (ii) the low number ber of pairing partner switches (PPSs) displayed by both trivalents and quadrivalents; and (iii) the existence of complex multivalents in which up to 13 chromosomes in the triploid and 22 chromosomes in the tetraploids were involved. However, only few heterologous chromosomal associations were maintained at metaphase I. The results obtained are discussed under the assumptions of the random end pairing model with some modifications. 相似文献