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61.
62.
Patterns of genetic variation in gas-exchange physiology were analyzed in a 15-year-old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) plantation that contains 25 populations grown from seed collected from across the natural distribution of the species. Seed was collected from 33°30 to 53°12 north latitude and from 170 m to 2930 m above sea level, and from the coastal and interior (Rocky Mountain) varieties of the species. Carbon isotope discrimination () ranged from 19.70() to 22.43() and was closely related to geographic location of the seed source. The coastal variety (20.50 (SE=0.21)) was not significantly different from the interior variety (20.91 (0.15)). Instead, most variation was found within the interior variety; populations from the southern Rockies had the highest discrimination (21.53 (0.20)) (lowest water-use efficiency). Carbon isotope discrimination (), stomatal conductance to water vapor (g), the ratio of intercellular to ambient CO2 concentration (ci/ca), and intrinsic water-use efficiency (A/g) were all correlated with altitude of origin (r=0.76, 0.73, 0.74, and –0.63 respectively); all were statistically significant at the 0.01 level. The same variables were correlated with both height and diameter at age 15 (all at P0.0005). Observed patterns in the common garden did not conform to our expectation of higher WUE, measured by both A/g and , in trees from the drier habitats of the interior, nor did they agree with published in situ observations of decreasing g and with altitude. The genetic effect opposes the altitudinal one, leading to some degree of homeostasis in physiological characteri tics in situ. 相似文献
63.
Effects of fire on water and salinity relations of riparian woody taxa 总被引:12,自引:0,他引:12
Water and salinity relations were evaluated in recovering burned individuals of the dominant woody taxa from low-elevation riparian plant communities of the southwestern U.S. Soil elemental analyses indicated that concentrations of most nutrients increased following fire, contributing to a potential nutrient abundance but also elevated alluvium salinity. Boron, to which naturalized Tamarix ramosissima is tolerant, was also elevated in soils following fire. Lower moisture in the upper 30 cm of burned site soil profiles was attributed to shifts in evapotranspiration following fire. Higher leaf stomatal conductance occurred in all taxa on burned sites. This is apparently due to higher photosynthetic photon flux density at the midcanopy level and may be partially mitigated by reduced unit growth in resprouting burned individuals. Predawn water potentials varied little among sites, as was expected for plants exhibiting largely phreatophytic water uptake. Midday water potentials in recovering Salix gooddingii growing in the Colorado River floodplain reached levels which are considered stressful. Decreased hydraulic efficiency was also indicated for this species by examining transpiration-water potential regressions. Recovering, burned Tamarix and Tessaria sericea had enriched leaf tissue 13C relative to unburned controls. Higher water use efficiency following fire in these taxa may be attributed to halophytic adaptations, and to elevated foliar nitrogen in Tessaria. Consequently, mechanisms are proposed which would facilitate increased community dominance of Tamarix and Tessaria in association with fire. The theory that whole ecosystem processes are altered by invading species may thus be extended to include those processes related to disturbance. 相似文献
64.
Strong-Gunderson Janet M. Palumbo Anthony V. 《Journal of industrial microbiology & biotechnology》1994,13(6):361-366
Summary A method is described for rapidly screening the metabolic potential of bacteria to oxidize semivolatile and volatile compounds as a sole carbon source. The method is based on automated system that utilizes MicroplatesTM manufactured by Biolog, Inc. (Hayward, CA, USA). This system detects bacterial respiratory activity from the oxidation of a carbon source introduced in volatile form. This is in contrast to the original design, which is based on inoculating a carbon source directly into each well. The 96-well (MT) microtiter plates contain nutrients and a tetrazolium dye. When a bacterial species is capable of oxidizing a volatile carbon substrate, the dye turns purple, and a spectrophotometric plate reader quantifies the response. As a test of this method 150 isolates, including isolates known to degrade some of the test compounds and negative controls were evaluated for their potential to oxidize carbon tetrachloride, toluene, ando-xylene. Thirty-seven isolates (25%) were qualitatively identified as contaminant oxidizers, and thirteen of these (35%) showed significant degradation capabilities for both toluene ando-xylene.Environmental Sciences Division Publication Number 4277. 相似文献
65.
Diel (24 h) courses of net CO2 exchange of leaves were determined in eight species of tropical rainforest plants on Barro Colorado Island, Panama, during 1990 and 1991. The species included three canopy trees, one liana, two epiphytes and one hemiepiphyte. One of the species studied was growing in a rain-forest gap. Daily carbon gain varied considerably across species, leaf age, and season. The analysis of data for all plants from 64 complete day/night cycles revealed a linear relationship between the diurnal carbon gain and the maximum rate of net CO2 uptake, Amax. Nocturnal net carbon loss was about 10% of diurnal carbon gain and was positively related to Amax. We conclude that short-term measurements of light-saturated photosynthesis, performed at periodic intervals throughout the season, allow the annual leaf carbon balance in these rain-forest plants to be predicted. 相似文献
66.
A. K. McConnell E. S. G. Semple C. T. M. Davies 《European journal of applied physiology and occupational physiology》1993,66(4):332-337
The present investigation examined the relationship between CO2 sensitivity [at rest (S
R) and during exercise (S
E)] and the ventilatory response to exercise in ten elderly (61–79 years) and ten younger (17–26 years) subjects. The gradient of the relationship between minute ventilation and CO2 production (
E/
CO2) of the elderly subjects was greater than that of the younger subjects [mean (SEM); 32.8 (1.6) vs 27.3 (0.4); P<0.01]. At rest, S
R was lower for the elderly than for the younger group [10.77 (1.72) vs 16.95 (2.13) 1 · min–1 · kPa–1; 1.44 (0.23) vs 2.26 (0.28) 1 · min–1 · mmHg–1; P<0.05], but S
E was not significantly different between the two groups [17.85 (2.49) vs 19.17 (1.62) l · min–1 · kPa–1; 2.38 (0.33) vs 2.56 (0.21) 1 · min–1 · mmHg–1]. There were significant correlations between both S
R and S
E, and
E/
CO2 (P<0.05; P<0.001) for the younger group, bot none for the elderly. The absence of a correlation for the elderly supports the suggestion that
E/
CO2 is not an appropriate index of the ventilatory response to exercise for elderly humans. 相似文献
67.
The increase in frequency and intensity of wildfires is seriously affecting forest ecosystems, especially in drought-prone areas. Trees’ recovery after fire is related to direct tree damage and is influenced by climate conditions, such as warm temperature and water shortage. In this study, we evaluate the post-fire effects on a Pinus pinaster Aiton forest growing in a hot and dry area of the Mediterranean region by comparing burned trees with severe crown reduction against unburned and not-defoliated trees. Inter-annual analyses of dendrochronology and stable isotopes in tree rings were combined with xylogenesis monitoring to investigate the effects of fire on tree growth, ecophysiological processes and wood formation. Tree-ring and isotope data showed a growth reduction and a decrease in photosynthetic activity in the burned trees, compared to control individuals, in the three years after fire. Further, the monitoring of cambial activity demonstrated a negative influence of warm and dry periods on wood formation, low xylem production, a delay in phenology and a reduction in xylem plasticity in burned trees. Our findings suggest that substantial photosynthetic limitations caused by crown defoliation and recurrent drought events could lead to severe growth decrease and reduction of trees ability to regain the pre-disturbance productivity rates. 相似文献
68.
69.
Carbon dioxide is rising in the global atmosphere, and this increase can be expected to continue into the foreseeable future. This compound is an essential input to plant life. Crop function is affected across all scales from biochemical to agro-ecosystem. An array of methods (leaf cuvettes, field chambers, free-air release systems) are available for experimental studies of CO2 effects. Carbon dioxide enrichment of the air in which crops grow usually stimulates their growth and yield. Plant structure and physiology are markedly altered. Interactions between CO2 and environmental factors that influence plants are known to occur. Implications for crop growth and yield are enormous. Strategies designed to assure future global food security must include a consideration of crop responses to elevated atmospheric CO2. Future research should include these targets: search for new insights, development of new techniques, construction of better simulation models, investigation of belowground processes, study of interactions, and the elimination of major discrepancies in the scientific knowledge base. 相似文献
70.
Marion Baur A.J. Meyer H.-G. Heumann M. Lützelschwab W. Michalke 《Plant biology (Stuttgart, Germany)》1996,109(5):382-387
The proton pumping ATPase in the plasma membrane of Elodea canadensis is believed to play a major role in inorganic carbon acquisition. To investigate potentially different carbon uptake strategies within the same plant, plasma membrane H+-ATPase distribution and polar current patterns were investigated in Elodea leaves and stems. Specific activity of plasma membrane H+-ATPase in leaf microsomal fractions was tenfold higher than in stem derived microsomes. Probing western blots with a monoclonal antibody specific for plasma membrane H+-ATPase, yielded strongly visible double bands at 100 kDa in leaf microsome preparations, whereas little antigen was detected in analogous stem microsome preparations. Using the same plasma membrane H+-ATPase specific antibody on tissue sections, the enzyme was found almost exclusively localized at the border of cells at the lower leaf surface. A positive ion current leaving the lower leaf surface was measured, using a vibrating probe device. Part of this current entered the upper leaf surface and part of it the internodes of the stem. The experimental results support the view, that Elodea leaves have different means of inorganic carbon uptake than stem internodes. 相似文献