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101.
Zhen-Yu Wang Feng-Min Li You-Cai Xiong Bing-Cheng Xu 《Journal of Plant Growth Regulation》2008,27(4):309-319
The soil-water threshold range of chemical signals and reactive oxygen species (ROS) homeostasis could have a profound impact
on drought tolerance in wheat. A pot experiment was used to investigate the homeostasis between ROS and antioxidant defense
at five harvest dates, and its role in the correlation between soil-water threshold range of chemical signals and drought
tolerance in three wheat (Triticum aestivum) cultivars during progressive soil drying. The cultivars were bred at different periods, cv. BM1 (old), cv. Xiaoyan6 (recent),
and cv. Shan229 (modern). They were treated with progressive soil drying. Shoot biomass was affected by drought imposed by
two water treatments (90% and 55% field water capacity). The modern wheat cultivar had a lower ROS content and higher ROS-scavenging
antioxidant capacity with greater soil drying (68–25% soil water content) compared with the older cultivar. The modern cultivar
also had excellent adaptation to drought, with a longer survival of 22.7 days and less reduction in shoot biomass of 20.9%
due to early chemical signals and better balance between ROS production and antioxidants. The older cultivar had survival
of 15.3 days and 37.3% reduction of shoot biomass. A wider soil-water threshold range of chemical signals was positively correlated
with improved drought tolerance and better ROS homeostasis. These results suggest that ROS homeostasis acts as a regulator
in relationships between the soil-water threshold range of chemical signals and drought tolerance. 相似文献
102.
Hanamura S Kiyono M Lukasik-Braum M Mlengeya T Fujimoto M Nakamura M Nishida T 《Primates; journal of primatology》2008,49(1):77-80
A flu-like disease spread among chimpanzees (Pan troglodytes schweinfurthii) of the M group at Mahale Mountains National Park, Tanzania, from June to July 2006. This epizootic or epidemic killed up
to 12 chimpanzees. The obvious evidence of their deaths came from finding the bodies of three infants who had previously shown
some symptoms of the disease. At least one of these infants died of pneumonia. In addition, nine chimpanzees were missing
after the outbreak. These individuals were assumed to have been killed by this epizootic because most of them had contact
with the infected individuals on the last days they were observed. We also found two dead bodies during this period, which
were thought to be those of two missing individuals. We confirmed 23 (35.4%) of 65 individuals of the M group showed some
symptoms of the disease, although most of them (20/23) did not die. More than half of them (14/23) had kin showing symptoms.
Since this epizootic may have been caused by contact with humans, it will be necessary to establish and follow appropriate
protocols for researchers, tourists, and park staff to observe chimpanzees, and to explore the mechanism of disease transmission
from humans to chimpanzees and among chimpanzees. 相似文献
103.
Nitrogen fertiliser rate and post-anthesis waterlogging effects on carbohydrate and nitrogen dynamics in wheat 总被引:1,自引:0,他引:1
Waterlogging is predicted to increase in both magnitude and frequency along with global warming, and will become one of the
most severe adversities for crop production in many regions. Nitrogen is considered to be an effective up-regulatory nutrient
for crops grown under stress and non-stress conditions. In this study, we try to evaluate N fertiliser effects on contents
of carbohydrate and N dynamics, dry matter accumulation in shoot, yield under post-anthesis waterlogging. Waterlogging after
anthesis significantly reduced grain yield due to decrease in thousand-kernel-weight and in grain number per spike. High N
fertiliser application aggravated grain yield loss due to post-anthesis waterlogging. These yield losses were related to the
decreases in dry matter accumulation, redistribution of stored photosynthate to the grain, and the conversion capacity from
carbohydrate to starch in grain. The decrease in dry matter accumulation could be attributed to the reduced activities of
Pn (photosynthesis) and SPS (sucrose phosphate synthase) in the flag leaf, while the low capacity in starch synthesis could
be explained by the reduced activities of sucrose synthase (SS) and soluble starch synthase (SSS) in grain. Total N uptake
in shoot was also reduced, which could contribute to the losses in biomass and yield by waterlogging. The decrease in Pn was
inconsistent with the increase in N content in the flag leaf at high N fertiliser application under post-anthesis waterlogging. 相似文献
104.
Larger Triticum aestivum plants do not preempt nutrient-rich patches in a glasshouse experiment 总被引:4,自引:0,他引:4
Plant competition belowground generally appears to be size-symmetric, i.e. larger plants only obtain a share of belowground
resources proportional to their size, and therefore do not suppress smaller individuals. The experimental evidence for size-symmetric
belowground competition comes primarily from experiments with homogenous soil conditions. It has been hypothesized that the
presence of high nutrient patches that can be pre-empted by larger plants can make competition belowground size-asymmetric.
We tested this hypothesis by growing Triticum aestivum individuals singly and in pairs in containers with aboveground dividers so that competition occurred only belowground. Plants
grew in either a homogenous soil mixture, or in the same mixture with a band of enriched soil between them. Initial size differences
were generated by a seven day difference in sowing date. There was no evidence of size-asymmetric competition with or without
soil heterogeneity. Large plants did not have a disproportionate effect on smaller plants, nor did they perform disproportionately
better when paired with a small neighbor. Our results suggest that in heterogeneous soil conditions, roots of larger plants
that reach nutrient patches first are not able to prevent roots of smaller plants that arrive later from obtaining resources
from the patch.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
105.
We examined frugivore visitation and seed dispersal of five large-seeded (≥ 5 mm) tree species in tropical montane forest based on their occurrence in frugivorous primate diets: Ekebergia capensis, Olea capensis, Parinari excelsa, Prunus africana , and Syzygium guineense. A total of 21 frugivores in five assemblages ( i.e. , chimpanzees, cercopithecines, large-bodied birds, small-bodied birds, and squirrels) were observed over the study period (August 2006 and October–April 2007). We observed seed dispersal in four of five tree species studied; no dispersal was observed for P. excelsa . Frugivore assemblages did not visit tree species equally. Primates spent the most time in trees and had the largest group size. Large-bodied birds (LB) and chimpanzees dispersed the highest number of seeds per minute. LB and cercopithecines potentially dispersed the greatest number of seeds for E. capensis , and chimpanzees for S. guineense . Our analyses indicated that the mean fruiting duration of the focal tree, time in the tree, and number of species present are important predictor variables for seed dispersal by small- and large-bodied birds, and cercopithecines. The number of fruiting trees in the immediate vicinity of the focal tree further predicted seed dispersal for small-bodied birds (SB). Large-bodied birdseed dispersal also was predicted by time in tree by SB, and the number of individuals for SB and cercopithecines. Cercopithecines (CS) were further explained by the time in tree and number of species (SB & LB), and number of individuals for CS. Our study highlights the complexity of describing the relative importance of a frugivore assemblage to the dispersal of a tree species seeds. 相似文献
106.
107.
Erick S. Van Dyke Dennis L. Scarnecchia Brian C. Jonasson Richard W. Carmichael 《Hydrobiologia》2009,625(1):27-42
Winter concealment habitat quality was assessed and its use by juvenile spring Chinook salmon (Oncorhynchus tshawytscha) quantified in three hatching areas of the Grande Ronde River Basin, Oregon USA. Fish densities were significantly higher
in pools with a higher winter concealment habitat index than pools with a lower index. The mean fork length and mean growth
rate of fish did not differ between pools with a higher or lower winter concealment habitat index, even though residual fish
were significantly larger than fish that emigrated. Biomass–density was significantly higher in pools with a higher winter
concealment habitat index than pools with a lower index in all three hatching areas. Biomass–density was positively associated
with the amount of cobble substrate (10–24.9 cm/m2) in all three hatching areas, and inversely associated with embeddedness in two of the hatching areas. Results of this study
indicate that enhancing winter concealment habitat could improve habitat quality resulting in increased carrying capacity
and winter usage by juvenile spring Chinook salmon.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Handling editor: J. A. Cambray 相似文献
108.
Deborah M. Buehler Anita Koolhaas Thomas J. Van’t Hof Ingrid Schwabl Anne Dekinga Theunis Piersma B. Irene Tieleman 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2009,195(5):445-451
The winter immunoenhancement hypothesis associates long nights and increased exposure to melatonin with enhanced immune function
in winter when resource availability is low and the chances of becoming ill are high. Thus, increased exposure to melatonin
in the winter could be adaptive for species facing difficult winter conditions. This idea has found some support in studies
of resident mammals. In birds, the link between day length and melatonin over the annual cycle is weaker, and contributions
of melatonin to seasonal timing are unclear. Furthermore, many species, especially migrants, do not experience the most difficult
conditions of their annual cycle in winter. In this study, we tested whether the winter immunoenhancement hypothesis holds
in an avian species, the red knot Calidris canutus. We found that melatonin duration and amplitude varied significantly over the annual cycle with the highest values occurring
in winter. However, peaks did not correspond to the winter solstice or with annual variation in immune function. Our findings
do not support the winter immunoenhancement hypothesis in knots and question whether the idea that immune function should
be bolstered in winter can be generalized to systems where winter is not the most difficult time of the year. 相似文献
109.
Voituron Y Paaschburg L Holmstrup M Barré H Ramløv H 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2009,179(2):223-230
Freeze tolerance and changes in metabolism during freezing were investigated in the moor frog (Rana arvalis) under laboratory conditions. The data show for the first time a well-developed freeze tolerance in juveniles of a European
frog capable of surviving a freezing exposure of about 72 h with a final body temperature of −3°C. A biochemical analysis
showed an increase in liver and muscle glucose in response to freezing (respectively, 14-fold and 4-fold between 4 and −1°C).
Lactate accumulation was only observed in the liver (4.1 ± 0.8 against 16.6 ± 2.4 μmol g−1 fresh weight (FW) between 4 and −1°C). The quantification of the respiratory metabolism of frozen frogs showed that the aerobic
metabolism persists under freezing conditions (1.4 ± 0.7 μl O2 g−1 FW h−1 at −4°C) and decreases with body temperature. After thawing, the oxygen consumption rose rapidly during the first hour (6-fold
to 16-fold) and continued to increase for 24 h, but at a lower rate. In early winter, juvenile R. arvalis held in an outdoor enclosure were observed to emerge from ponds and hibernate in the upper soil and litter layers. Temperature
recordings in the substratum of the enclosure suggested that the hibernacula of these juvenile frogs provided sheltering from
sub-zero air temperatures and reduced the time spent in a frozen state corresponding well with the observed freeze tolerance
of the juveniles. This study strongly suggests that freeze tolerance of R. arvalis is an adaptive trait necessary for winter survival. 相似文献
110.
Several populations of wild chimpanzees use tools to raid bee nests, but preliminary observations of chimpanzees in the Congo
Basin indicate that they may have developed sophisticated technical solutions to gather honey that differ from those of apes
in other regions. Despite the lack of habituated groups within the range of the central subspecies, there have been several
reports of different types of tools used by chimpanzees to open beehives and gather honey. Researchers have observed some
of these behaviors (honey dipping) in populations of western and eastern chimpanzees, whereas others (hive pounding) may be
limited to this region. Toward evaluating hypotheses of regional tool using patterns, we provide the first repeated direct
observations and systematic documentation of tool use in honey-gathering by a population of Pan troglodytes troglodytes. Between 2002 and 2006, we observed 40 episodes of tool use in honey-gathering by chimpanzees in the Goualougo Triangle,
Republic of Congo. Pounding was the most common and successful strategy to open beehives. Chimpanzees at this site used several
tools in a single tool-using episode and could also attribute multiple functions to a single tool. They exhibited flexibility
in responses toward progress in opening a hive and hierarchical structuring of tool sequences. Our results support suggestions
of regional tool using traditions in honey-gathering, which could be shaped by variation in bee ecology across the chimpanzee
range. Further, we suggest that these chimpanzees may have an enhanced propensity to use tool sets that could be related to
other aspects of their tool repertoire. Clearly, there is still much to be learned about the behavioral diversity of chimpanzees
residing within the Congo Basin. 相似文献