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101.
Hilary Glover 《Journal of phycology》1977,13(3):208-212
Cultures of Isochrysis galbana Parks and Phaeodactylum tricornutum Bohlin were grown in iron-limited chemostats. With increasing iron deficiency, photosynthetic rate per cell and assimilation number decreased. The pattern of photosynthesis was also altered; in Fe deficient cells the proportion of 14C fixed in glycine and serine decreased with an accompanying increase into alanine after 3 min assimilation. Although there was no significant effect of Fe deficiency on the proportion of 14C incorporated into total amino acids and amides, the percentage of total 14C fixed in protein increased with increasing Fe deficiency. Cellular levels of chlorophyll a, carotenoids, cytochromes and protein also decreased with increasing Fe deficiency. However, the reduction in chlorophyll a/cell was not as great as that of cytochrorne f1 and Fe deficient cells therefore showed a marked increase in chlorophyll a:cytochrorne f1 ratio. 相似文献
102.
Summary Application of a granular formulation of hexachlorocyclohexane (HCH) to the potted soil at flooding decreased the concentration
of iron and. to some extent, manganese in rice plants, especially at concentrations above 3 ppm active ingredient (a.i.) Likewise,
HCH, applied to rice fields at transplanting (several days after submergence) caused a significant decrease in the concentration
of iron, and not manganese, in the rice plant but only at concentrations above 12.5 kg a.i./ha despite high levels of reduced
iron in the soil. Inhibition of iron reduction by HCH was more pronounced when applied at flooding than at several days after
flooding. 相似文献
103.
Johannes F. Imhoff Brian J. Tindall William D. Grant Hans G. Trüper 《Archives of microbiology》1981,130(3):238-242
A new phototrophic bacterium was isolated from Jordanian and Kenyan alkaline salt lakes. Cells are rod shaped, 1.5 m wide and 2–4 m long, and motile by polar flagella. They divide by binary fission, and possess photosynthetic membranes as lamellar stacks similar to those in the other species of the genus Ectothiorhodospira and the brown colored Rhodospirillum species. The presence of bacteriochlorophyll a and carotenoids of the normal spirilloxanthin series is indicated by the absorption spectra of living cells. Under certain growth conditions the cells form gas vacuoles, may become immotile and float to the top of the culture medium. Sulfide and thiosulfate are used as photosynthetic electron donors. During the oxidation of sulfide to sulfate, elemental sulfur is formed, which is accumulated outside the cells. The organisms are strictly anaerobic, do not require vitamins, are moderately halophilic and need alkaline pH-values for growth. The new species Ectothiorhodospira vacuolata is proposed. 相似文献
104.
The influence of light and nutrient addition upon the sediment chemistry of iron in an arctic lake 总被引:1,自引:1,他引:0
The geochemical response of sediments to increased nutrient input to an Alaskan, arctic lake was examined using direct measurements
of sediment-water chemical fluxes. An unexpected increase in Fe flux occurred when sediments were exposed to high incident
radiation and nutrient concentrations. Correlation between light and acid-soluble Fe concentrations suggests that photoreduction
of Fe(III) oxides may occur, but nutrient addition enhanced the effect indicating that primary productivity was also important.
The processes controlling the flux of Fe from sediments in this lake were complex and included the redox potential (dissolved
oxygen concentration) of the water, quality of organic matter present in the sediment, light, and nutrients supplied from
the sediments and/or water column. These four factors together with the possibility of direct uptake of Fe by phytoplankton
and the possible release of algal reductants may contribute to Fe cycling in this lake. 相似文献
105.
Effect of hydrogen sulfide on growth of sulfate reducing bacteria 总被引:20,自引:0,他引:20
A culture of sulfate reducing bacteria (SRB) growing on lactate and sulfate was incubated at different pH values in the range of 5.8-7.0. The effect of pH on growth rate was determined in this pH range; the highest growth rate was observed at pH 6.7. Hydrogen sulfide produced from sulfate reduction was found to have a direct and reversible toxicity effect on the SRB. A hydrogen sulfide Concentration of 547 mg/L (16.1 mM) completely inhibited the culture growth. Comparison between acetic acid and hydrogen sulfide inhibition is presented and the concomitant inhibition kinetics are mathematically described. (c) 1992 John Wiley & Sons, Inc. 相似文献
106.
Collaborative experiments were conducted to determine whether microbial populations associated with plant roots may artifactually
affect the rates of Fe uptake and translocation from microbial siderophores and phytosiderophores. Results showed nonaxenic
maize to have 2 to 34-fold higher Fe-uptake rates than axenically grown plants when supplied with 1 μM Fe as either the microbial siderophore, ferrioxamine B (FOB), or the barley phytosiderophore, epi-hydroxymugineic acid (HMA).
In experiments with nonsterile plants, inoculation of maize or oat seedlings with soil microorganisms and amendment of the
hydroponic nutrient solutions with sucrose resulted in an 8-fold increase in FOB-mediated Fe-uptake rates by Fe-stressed maize
and a 150-fold increase in FOB iron uptake rates by Fe-stressed oat, but had no effect on iron uptake by Fe-sufficient plants.
Conversely, Fe-stressed maize and oat plants supplied with HMA showed decreased uptake and translocation in response to microbial
inoculation and sucrose amendment. The ability of root-associated microorganisms to affect Fe-uptake rates from siderophores
and phytosiderophores, even in short-term uptake experiments, indicates that microorganisms can be an unpredictable confounding
factor in experiments examining mechanisms for utilization of microbial siderophores or phytosiderophores under nonsterile
conditions. 相似文献
107.
Roles of iron in neoplasia 总被引:5,自引:0,他引:5
Eugene D. Weinberg 《Biological trace element research》1992,34(2):123-140
Research and clinical observations during the past six decades have shown that: 1. Iron promotes cancer cell growth; 2. Hosts attempt to withhold or withdraw iron from cancer cells; and 3. Iron is a factor in prevention and in therapy of neoplastic disease. Although normal and neoplastic cells have similar qualitative requirements for iron, the neoplastic cells have more flexibility in acquisition of the metal. Excessive iron levels in animals and humans are associated with enhanced neoplastic cell growth. In invaded hosts, cytokine-activated macrophages increase intracellular ferritin retention of the metal, scavenge iron in areas of tumor growth, and secrete reactive nitrogen intermediates to effect efflux of nonheme iron from tumor cells. Procedures associated with lowering host intake of excess iron can assist in prevention and in management of neoplastic disease. Chemical methods for prevention of iron assimilation by neoplastic cells are being developed in experimental and clinical protocols. The antineoplastic activity of a considerable variety of chemicals, as well as of radiation, is modulated by iron. The present article focuses on recent findings and suggests directions for further cancer-iron research. 相似文献
108.
A. M. Rofe J. C. Philcox D. R. Haynes M. W. Whitehouse P. Coyle 《Biological trace element research》1992,34(3):237-248
The early changes in hepatic metallothionein (MT) and plasma zinc (Zn), copper (Cu), and iron (Fe) were investigated during
the induction of adjuvant (AJ) arthritis in rats in conjunction with cyclosporin (CSA) treatment. Plasma Zn decreased after
AJ injection (60% of control values at 8 h), and this was associated with a 4.5-fold increase in hepatic MT at 8 h. Plasma
Zn was lowest at 16 h (40% of control), whereas hepatic MT concentrations increased to a maximum of 20-fold at 16 h. Changes
in plasma Fe paralleled those of Zn, whereas plasma Cu levels were increased. Plasma metal and hepatic MT concentrations returned
toward normal from d 1–7. At d 14, when marked paw swelling was apparent, hepatic MT and plasma Cu were again increased and
plasma Zn decreased.
Administration of CsA decreased MT induction in rats injected with AJ and also caused a marked recovery in plasma Zn and Fe
levels. These changes were small but significant even in the early stages (up to 24 h) after AJ injection and were followed
by a sustained improvement in all parameters, corresponding to the nonappearance of clinical arthropathy in CsA-treated rats.
TNF-α and IL-6 production by peritoneal macrophages isolated from AJ-injected rats was significantly decreased by CsA treatment
at d 7 and 14. The inhibition of hepatic MT induction during acute and chronic inflammation by cyclosporin emphasizes the
role of the immune system in altered metal homeostasis in inflammation. 相似文献
109.
Pilar Galan Helene Thibault Paul Preziosi Serge Hercberg 《Biological trace element research》1992,32(1-3):421-426
The relationship between iron status and capacity for IL-2 production by lymphocytes was assessed in 81 children from 6 mo
to 3 yr of age selected at random from a population with low socioeconomic status, undergoing free systematic examination
in four children's health centers in the Paris area. Iron deficiency was defined by the existence of at least two abnormal
values among the three indicators of iron status: serum ferritin level ≤12 μg/L, transferrin saturation <12%, and erythrocyte
protoporphyrin concentration >3 μg/g hemoglobin. According to this definition, 53 children were classified as iron deficient
and 28 as iron sufficient. No differences were observed between the iron-deficient and iron-sufficient groups in terms of
the IL-2 concentration without stimulation by PHA. IL-2 production by lymphocytes stimulated with PHA, as well as the stimulation
index (ratio of IL-2 concentration following stimulation by PHA to that of IL-2 concentration without stimulation by PHA)
were significantly lower in iron-deficient children. The reduction in IL-2 production by activated lymphocytes observed in
our study of iron-deficient children may be responsible for impairments in immunity found by other authors, particularly in
cell-mediated immunity. 相似文献
110.