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101.
Clostridium mayombei sp. nov., a previously undescribed H2-oxidizing CO2-reducing acetogenic bacterium, was isolated from gut contents of the African soilfeeding termite, Cubitermes speciosus. Cells were anaerobic, Gram positive, catalase and oxidase negative, endospore-forming motile rods which measured 1×2 – 6 m and which had a DNA base composition of 25.6 mol% G+C (strain SFC-5). Optimum conditions for growth on H2+CO2 were at 33°C and pH 7.3, and under these conditions cells produced acetate according to the equation: 4 H2+2 CO2CH3COOH+2 H2O. Other substrates supporting good growth included carbohydrates (e.g. glucose, xylose, starch), sugar alcohols, and organic and amino acids, and with these substrates acetate was almost always the principle fermentation product. Comparative analysis of 16S rRNA nucleotide sequences confirmed that C. mayombei was closely related to various members of the genus Clostridium. However, morphological and physiological differences between C. mayombei and other homoacetogenic clostridia were deemed significant enough to warrant creation of a new taxon. Results are discussed in light of the diversity of H2/CO2 acetogens recently isolated from various termites, and in terms of the relative importance of H2/CO2 acetogenesis to termite nutrition. 相似文献
102.
Influences of the salt concentration on the fatty acid composition of Ectothiorhodospira species and other phototrophic purple bacteria have been analysed. Major fatty acids in bacteria of the genera Rhodobacter, Rhodopseudomonas, Chromatium, and Ectothiorhodospira were straight chain saturated and monounsaturated C-16 and C-18 fatty acids. Salt-dependent responses of all investigated bacteria revealed relations to their salt optima. Minimum values of C-16 and saturated fatty acids and maximum values of C-18 and unsaturated fatty acids were found at or close to the salt optima. Responses of Ectothiorhodospira mobilis upon changes in salinity were nearly identical, whether cells were grown in batch culture or in continuous culture with identical dilution rates at all salt concentrations. With increasing temperature, the fatty acid composition of Ectothiorhodospira mobilis and Ectothiorhodospira halophila strains showed decreasing portions of C-18 and of unsaturated fatty acids, while the contents of C-16 and saturated fatty acids increased. The results are discussed with respect to bilayer stabilisation and membrane fluidity.Abbreviations PC
phosphatidylcholine
- PG
phosphatidylglycerol
- CL
cardiolipin
- PE
phosphatidylethanolamine 相似文献
103.
Rolf Altenburger Sibylle Abarzua Rainer Callies L. Horst Grimme Adalbert Mayer Dieter Leibfritz 《Archives of microbiology》1991,156(6):471-476
Cultures of the cyanobacterium Microcystis firma show rhythmic uptake and release of ammonia under conditions of carbon limitation. The massive removal of ammonia from the medium during the first light phase has little impact on the intracellular pH: a pH shift of less than 0.2 U towards the alkaline can be measured by in vivo 31P NMR. Furthermore, the energy status of the cells remains regulated. In vivo 15N NMR of M. firma, cultivated either with labelled nitrate or ammonia as the sole nitrogen source, reveals only gradual differences in the pool of free amino acids. Additionally both cultivation types show -aminobutyric acid, acid amides and yet unassigned secondary metabolites as nitrogen storing compounds. Investigating the incorporation of nitrogen under carbon limitation, however, only the amide nitrogen of glutamine is found permanently labelled in situ. While transamination reactions are blocked, nitrate reduction to ammonia can still proceed. Cation exchange processes in the cell wall are considered regarding the ammonia disappearance in the first phase, and the control of ammonia uptake is discussed with respect to the avoidance of intracellular toxification.Abbreviations GABA
-aminobutyric acid
- GOGAT
glutamate synthase
- GS
glutamine synthetase
- MDP
methylene diphosphonate
- MOPSO
3-(N-morpholino)-2-hydroxy-propanesulfonic acid
- NDPS
nucieoside diphosphosugars
- NOE
nuclear Overhauser effect
- NMR
nuclear magnetic resonance
For convenience, the term ammonia is used throughout to denote ammonia or ammonium ion when there is no good evidence as to which chemical species is involved 相似文献
104.
Antibiotic production by the marine photosynthetic bacterium Chromatium purpuratum NKPB 031704: localization of activity to the chromatophores 总被引:2,自引:0,他引:2
J.Grant Burgess Hideaki Miyashita Hiroaki Sudo Tadashi Matsunaga 《FEMS microbiology letters》1991,84(3):301-306
Abstract Over 200 strains of marine purple photosynthetic bacteria were isolated. Two strains showed antibiotic activity towards Saccharomyces cerevisiae and were tentatively identified as Chromatium purpuratum . Crude antibiotic, prepared by solvent extraction, showed a broad antimicrobial spectrum. The highest activity was found in the chromatophore fraction. Chromatographic separation of purified light harvesting complex from one strain, NKPB 031704, showed the presence of two separate pigmented compounds which were responsible for antimicrobial activity. Our findings reveal the unexpected ability of photosynthetic bacteria to produce broad spectrum antibiotics. In addition, this is the first example of intracellular localization of antibiotic activity in a marine bacterium. 相似文献
105.
Analysis of bacterial populations in a grassland soil according to rates of development on solid media 总被引:3,自引:0,他引:3
Abstract The process of colony formation by bacteria from grassland soil sampled in April, July and September was simulated by a colony-forming curve (CFC). The CFC was a super-imposition of several component curves (cCFC) given theoretically by the first order reaction (FOR) model [3,6]. The pattern of FOR model curves was not influenced by the time of sampling and four cCFCs were always recognized during an incubation period of 160 h. It was considered that the CFC describes an inherent property of the bacterial population of the field. Bacterial isolates were obtained from colonies produced in each of four cCFCs on agar plates. Isolates corresponding to one cCFC were classified as one group. The bacterial isolates were characterized by morphological and physiological tests and subsequently clustered. Few oligotrophic bacteria were obtained among bacteria which produced visible colonies within 63 h of incubation time. On the other hand, approx. 50% of bacteria which produced v colonies after 63 h were oligotrophic bacteria. The time required for the appearance of the first colony, t r of the FOR model, was very similar in the isolates belonging to one group. A close linear relationship was observed between t r value and doubling time of isolates. 相似文献
106.
107.
Urs Uehlinger 《Hydrobiologia》1986,135(3):197-206
The aerobic decomposition of the green alga Chlamydomonas reinhardii by a mixed population of lake bacteria was studied in batch and chemostat cultures. Bacterial chemostats were supplied with continuously heatkilled algae. The dead algae rapidly released most of their phosphorus as SRP. In the batch experiments bacteria acted as consumers of the released algal phosphorus. This phosphorus uptake was dependent on the C:P ratio of the algae. During the death phase of the bacteria most of the bacterial phosphorus itself was released. The continuous supply of energy in form of dead algae in the chemostat experiments prevented the death phase of the bacteria and thus any net regeneration of phosphorus. The influence of the C:P stoichiometry of algae and bacteria on the regeneration of algal phosphorus is discussed. 相似文献
108.
The chlorellavorous bacterium . "Vampirovibrio chlorellavorus" Gromov et Mamkaeva, grows only by killing and consuming the cell contents of species of the green alga Chlorella Beijerinck. Of the 76 algal strains examined in this study, the bacterium attacks all 31 strains of the species C. vulgaris. C. sorokiniana, and C. kessleri, but attacks only two of 39 strains of nine other Chlorella species. Neither of two Prototheca strains was susceptible to attack. This narrow host specificity may be related to cell surface properties . 相似文献
109.
Summary A re-examination of earlier NPK fertilization experiments in Douglas fir stands on sandy soils shows the effects of high nitrogen
input by air pollution during the last 10–15 years on plant nutrition at these sites. In 1960, experimental plots showed a
positive growth reaction to nitrogen, phosphorus, and potassium fertilization. All suffered from severe phosphorus deficiency
in 1984, low phosphorus in the needles was invariably accompanied by a high nitrogen content, with all N/P ratios between
20 and 30. The same conclusion emerges from an independent investigation of nutrient status of a selection of Douglas fir
stands. Hence, if stand productivity and a balanced nutrient status of the trees is to be maintained, the increase in atmospheric
input of nitrogen calls for supplementary fertilization. Given the current N/P ratios in the needles, a positive growth response
to phosphorus fertilization is to be expected. 相似文献
110.
Summary Nitrate fertiliser labelled with15N was applied to a field grown crop of winter wheat. Uptake and assimilation of fertiliser nitrate was studied by monitoring the appearance of labelled nitrate and labelled amino acids in the xylem sap. Shortly after applying15N-nitrate to the soil about 30 per cent of recently absorbed15N was in the reduced form, indicating that roots of cereal crops can make a substantial contribution in reducing nitrate. Seasonal changes in crop growth andin vivo NRA are also described. 相似文献