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91.
Matthew J. Nicholson Christopher S. McSweeney Roderick I. Mackie Jayne L. Brookman Michael K. Theodorou 《Anaerobe》2010,16(2):66-73
Gut fungal-specific PCR primers have been used to selectively amplify the ITS1 region of gut fungal rDNA recovered from faeces of domestic and wild animals to investigate population diversity. Two different gel-based methods are described for separating populations of gut fungal rDNA amplicons, namely (1) denaturing gradient gel electrophoresis (DGGE) and (2) separation according to small size differences using Spreadex, a proprietary matrix for electrophoresis. Gut fungal populations were characterised by analysis of rDNA in faeces of seventeen domesticated and ten wild herbivores. Sequences derived from these gel-based characterisations were analysed and classified using a hidden Markov model-based fingerprint matching algorithm. Faecal samples contained a broad spectrum of fungi and sequences from five of the six recognised genera were identified, including Cyllamyces, the most recently described gut fungal genus, which was found to be widely distributed in the samples. Furthermore, four other novel groupings of gut fungal sequences were identified that did not cluster with sequences from any of the previously described genera. Both gel- and sequence- based profiles for gut fungal populations suggested a lack of geographical restriction on occurrence of any individual fungal type. 相似文献
92.
Temperature and oxygen regimes were monitored weekly in a four-year old reservoir and downstream for ten weeks during the
summer (May 15 to July 30, 1979), and monthly in the fall and winter. During the summer discharge levels were changed from
top to bottom in the eighth week, back to top in the ninth, all at 0.71 m3/s (= 25 cfs), and returned to the bottom in the tenth, but at 1.14 m3/s (= 40 cfs).
Changing the discharge level had little or no impact on the thermal regime within the lake or downstream at 1.14 m3/s and only a moderate impact on water in the lake near the dam at 0.71 m3/s bottom discharge by generating double thermoclines. Oxygen depletion rates were greatest near the surface of the lake,
mainly due to temperature effects, but increased greatly at the 3 m depth, the level of the top discharge port, when discharge
was changed from bottom to top. Discharge of anoxic waters through the bottom of the dam caused a drop in oxygen content immediately
downstream but oxygen content returned to inflow values within 1 km downstream of the dam. 相似文献
93.
This study used 16S rRNA-based pyrosequencing to examine the microbial community that is closely associated with the colonic mucosa of five healthy individuals. Spatial heterogeneity in microbiota was measured at right colon, left colon and rectum, and between biopsy duplicates spaced 1 cm apart. The data demonstrate that mucosal-associated microbiota is comprised of Firmicutes (50.9% ± 21.3%), Bacteroidetes (40.2% ± 23.8%) and Proteobacteria (8.6%± 4.7%), and that interindividual differences were apparent. Among the genera, Bacteroides, Leuconostoc and Weissella were present at high abundance (4.6% to 41.2%) in more than 90% of the studied biopsy samples. Lactococcus, Streptococcus, Acidovorax, Acinetobacter, Blautia, Faecalibacterium, Veillonella, and several unclassified bacterial groups were also ubiquitously present at an abundance <7.0% of total microbial community. With the exception of one individual, the mucosal-associated microbiota was relatively homogeneous along the colon (average 61% Bray-Curtis similarity). However, micro-heterogeneity was observed in biopsy duplicates within defined colonic sites for three of the individuals. A weak but significant Mantel correlation of 0.13 was observed between the abundance of acidomucins and mucosal-associated microbiota (P-value = 0.04), indicating that the localized biochemical differences may contribute in part to the micro-heterogeneity. This study provided a detailed insight to the baseline mucosal microbiota along the colon, and revealed the existence of micro-heterogeneity within defined colonic sites for certain individuals. 相似文献
94.
Evolution and ecology of antibiotic resistance genes 总被引:8,自引:0,他引:8
A new perspective on the topic of antibiotic resistance is beginning to emerge based on a broader evolutionary and ecological understanding rather than from the traditional boundaries of clinical research of antibiotic-resistant bacterial pathogens. Phylogenetic insights into the evolution and diversity of several antibiotic resistance genes suggest that at least some of these genes have a long evolutionary history of diversification that began well before the 'antibiotic era'. Besides, there is no indication that lateral gene transfer from antibiotic-producing bacteria has played any significant role in shaping the pool of antibiotic resistance genes in clinically relevant and commensal bacteria. Most likely, the primary antibiotic resistance gene pool originated and diversified within the environmental bacterial communities, from which the genes were mobilized and penetrated into taxonomically and ecologically distant bacterial populations, including pathogens. Dissemination and penetration of antibiotic resistance genes from antibiotic producers were less significant and essentially limited to other high G+C bacteria. Besides direct selection by antibiotics, there is a number of other factors that may contribute to dissemination and maintenance of antibiotic resistance genes in bacterial populations. 相似文献
95.
96.
Wm. J. Mackie 《BMJ (Clinical research ed.)》1889,2(1498):620-621
97.
The relationship between crystallization and the annealing process is well established in the synthetic polymer field. This relationship appears to have been somewhat neglected in studies on biopolymers. Results are presented to show the effect of both humidity and temperature in promoting structural changes in polysaccharide system. Three different polysaccharides have been used as examples of how crystallization may be speeded up by annealing at elevated temperatures. 相似文献
98.
Appetite and growth rate were measured in Sparus aurata fed ad-libitum a basal diet supplemented with either a synthetic mixture of chemicals based upon the analysis of Mylilus edulis , muscle extract, or newly hatched Artemia saline nauplii. These components were tested for their feeding attraction potency, and were added to the basal diet at three concentrations each; 5, 10 and 20 g kg-1 dry diet.
Appetite, which was defined as ad-libitum food intake, was significantly affected by the type and concentration of attractant. When the basal diet was supplemented with 10 or 20 g kg-1 of the synthetic Mytilus edulis muscle extract, it was associated with significantly higher appetite than the basal diet only or the basal diet supplemented with any level of newly hatched Artemia salina nauplii. On the other hand, relative growth rate under the same conditions did not completely conform to the results with appetite. The difference between appetite and growth rate as criteria for the evaluation of food attractants is discussed. 相似文献
Appetite, which was defined as ad-libitum food intake, was significantly affected by the type and concentration of attractant. When the basal diet was supplemented with 10 or 20 g kg
99.
100.
Limestone karst ecosystems in Southeast Asia and Vietnam are important reservoirs for biodiversity and are currently experiencing
habitat loss and degradation due to land use changes and increasing pressure from extractive and tourism industries. Recent
reviews indicate that their biodiversity is poorly known and raise doubts about the extent to which karst can maintain its
biodiversity in the face of ongoing degradation. We investigated this issue by examining the effects of forest degradation
on bat species diversity, composition and abundance. Using mist nets and harp traps, we sampled bat assemblages in karst forests
of differing integrity for a total of 240 net nights and 180 harp trap nights, capturing 694 bats representing 36 species
and five families. Our results confirm that primary forests in Vietnamese karst are exceptionally important for bat diversity,
supporting substantial proportions of the national fauna. Disturbed and heavily degraded karst forests also appear capable
of supporting relatively high numbers of bat species at low abundances, but their ability to do so in the longer term is in
doubt and requires further research. Our findings of bats in relict forests on karst hillsides and ridgetops provide justification
for their protection and raise the possibility that these may provide corridors for the movement of forest-dwelling bats within
anthropogenic landscapes. Since the majority of Vietnamese karst landscapes remain unprotected however, the future of their
biodiversity remains uncertain. 相似文献