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101.
Water use efficiency of twenty-five co-existing Patagonian species growing under different soil water availability 总被引:2,自引:0,他引:2
The variation of plant water use efficiency (WUE) with water availability has two interacting components: a plastic response,
evident when individuals of the same genotype are compared (e.g. wet versus dry years), and an interspecific response, evident
when different species living in habitats with different water availability are compared. We analysed the WUE of 25 Patagonian
species that belong to four life forms (grasses, shrubs, annual herbs and perennial herbs) in relation to the climatic conditions
of 2 years and the mean historic water availability experienced by each species. To estimate water availability, we calculated
the effective soil water potential (EWP) of each species, based on available information about soil water dynamics, phenology
and root system structure. To estimate WUE, we used isotopic discrimination of leaf C (Δ13C) and mean annual water vapour difference between leaves and atmosphere (Δe) measured in situ. For the plastic response, for every species and life form, WUE increased from the dry to the wet year.
We hypothesize that photosynthesis was less nutrient limited in the wet than in the dry year, facilitating higher net photosynthesis
rates per unit of stomatal conductance in the wet year. For the interspecific response, WUE was lower in species native to
drier habitats than in species native to wetter habitats. This response was mostly accounted for by a decrease in Δe with EWP. Annual herbs, which avoid drought in time (they have the earliest growth cycle), and shrubs, which avoid drought
in space (they have the deepest roots), showed the highest EWP and WUE. We conclude that the conventional wisdom which states
that the highest WUE occurs within a species during the driest years, and among species in the driest habitats, does not always
hold true, and that co-existing life forms drastically differ in water availability and water economy. 相似文献
102.
Many herbivores elicit biochemical, physiological, or morphological changes in their host plants that render them more resistant
to co-occurring herbivores. Yet, despite the large number of studies that investigate how induced resistance affects herbivore
preference and performance, very few have simultaneously explored the cascading effects of induction on higher trophic levels
and consequences for prey suppression. In our study system, early-season herbivory by leafhoppers elevated plant resistance
to subsequent attack by chrysomelid beetles sharing the same host plant. Notably, beetles feeding on leafhopper-damaged plants
incurred developmental penalties (e.g., prolonged time in early larval instars) that rendered them more susceptible to predation
by natural enemies. As a result, the combined bottom-up effect of leafhopper-induced resistance and the top-down effect of
enhanced predation resulted in the synergistic suppression of beetle populations. These results emphasize that higher trophic
level dynamics should be considered in conjunction with induced resistance to better understand how plants mediate interspecific
interactions in phytophagous insect communities. 相似文献
103.
Based on universal thermodynamic principles (Schwarz in Biophys Chem 86:119–129, 2000) it is shown how measured enthalpy changes can be utilized to determine the relevant binding isotherm as well as the variation
of the molar enthalpy change. This is carried out in a novel way involving multiple titration experiments whose evaluation
requires no beforehand assumptions or models whatever. An appropriate specific model mechanism may be discussed afterwards
and developed in view of the given experimental results. The pertinent procedure is demonstrated using micro-calorimetric
data obtained in the case of the local anesthetic dibucaine as it associates with POPC liposomes. Mutual interactions of the
bound ligand molecules could be described in terms of repulsive enthalpic and entropic activity coefficients. Apparently these
are induced by electrostatic forces and by the finite size of binding sites, respectively. 相似文献
104.
Alexandra Leitão Raquel Chaves Sara Santos Henrique Guedes-Pinto Pierre Boudry 《Journal of experimental marine biology and ecology》2007,343(2):253-260
The taxonomic status of the two commercially important cupped oysters, Crassostrea angulata, the Portuguese oyster (Lamarck, 1819) and Crassostrea gigas, the Japanese oyster (Thunberg, 1793) has long been in question. The recent observation of the hybridization between C. gigas and C. angulata and the production of fertile F1s led us to search for cytogenetic evidence of both parental genomes in the interspecific hybrids. The cytogenetic characterization of the hybrids was performed by the use of restriction endonuclease treatments. This technique has recently shown the potential for individual chromosome identification by banding in oysters. Chromosomes of C. gigas, C. angulata and their hybrids were treated with two different restriction enzymes (ApaI and HaeIII), stained with Giemsa, and examined for banding patterns. These chromosome markers allowed the parental haploid sets to be identified in the hybrids. The analysis of the banded karyotypes of the interspecific hybrids showed that for each chromosome pair, one of the homologues presented a banding pattern consistent with that of C. gigas and the other homologue presented a banding pattern consistent with that of C. angulata. These cytogenetic results substantiate the reported interspecific hybridization between C. gigas and C. angulata. In view of these results and taking into account the present expansion of C. gigas aquaculture in southern Europe, the question of the need for preservation of pure C. angulata stocks should be raised as only a few populations remain in the south of Spain and Portugal. Recently, changes in the genetic composition of populations in southern Portugal have indeed been observed, showing that human activities have created contact zones between the two taxa while no natural sympatric zones exist in Europe. 相似文献
105.
Daniela M. Simeonovska-Nikolova 《Journal of Ethology》2007,25(1):41-48
The social interactions between Apodemus agrarius and A. flavicollis, and their behavioral responses to conspecific and heterospecific odors, were studied in male–male and female–female interspecific
dyadic encounters, and an attraction–avoidance test was used in order to clarify the behavioral mechanisms which control their
relationships in wild populations. The experiments were carried out at the beginning and at the end of the breeding season—in
spring and in autumn. In spring the aggressiveness was higher than in autumn. Males of both species showed attraction to conspecific
odors from the opposite sex, while the females were indifferent. In autumn both males and females displayed attraction to
conspecific odors from the same sex. However, mice of both species showed avoidance to heterospecific odors from the same
and the opposite sex in spring, and indifference to heterospecific odors from the same and the opposite sex in autumn. Based
on these findings, it could be assumed that the patterns of social interactions and responses to conspecific and heterospecific
odors undergo seasonal changes in their life cycle. Probably the avoidance response to heterospecific odors could serve as
a spacing mechanism to avoid aggressive encounters between A. agrarius and A. flavicollis in syntopic habitats during the breeding period. 相似文献
106.
Low dissolved oxygen (DO) levels often occur during summer in tidal creeks along the southeastern coast of the USA. We analyzed rates of oxygen loss as water-column biochemical oxygen demand (BOD5) and sediment oxygen flux (SOF) at selected tidal creek sites monthly over a 1-year period. Ancillary physical, chemical and biological data were collected to identify factors related to oxygen loss. BOD5 rates ranged from 0.0 mg l?1 to 7.6 mg l?1 and were correlated positively with organic suspended solids, total suspended solids, chlorophyll a concentrations, temperature, and dissolved oxygen, and negatively with pH and nitrate + nitrite. SOF rates ranged from 0.0 to 9.3 g O2 m?2 d?1, and were positively correlated with temperature, chlorophyll a, and total suspended solids, but negatively with dissolved oxygen. Both forms of oxygen uptake were seasonally dependent, with BOD5 elevated in spring and summer and SOF elevated in summer and fall. Average oxygen loss to sediments was greater and more variable than oxygen loss in the water column. Oxygen deficits at three of five locations were significantly related to BOD5 and SOF, but not at two sites where ground water discharges were observed. Correlation and principal component analyses suggested that BOD5 and SOF responded to somewhat different suites of environmental variables. BOD5 was driven by a set of parameters linked to warm season storm water inputs that stimulated organic seston loads, especially chlorophyll a, while SOF behaved less strongly so. Runoff processes that increase loads of organic material and nutrients and ground water discharges low in dissolved oxygen contribute to occurrences of low dissolved oxygen in tidal creeks. 相似文献
107.
Morten Skage Anders Hobæk Štĕpánka Ruthová Barbara Keller Adam Petrusek Jaromír Sed’a Piet Spaak 《Hydrobiologia》2007,594(1):19-32
A collaborative research effort was undertaken to evaluate the robustness of a recently developed genetic tool for species
identification of members in the morphologically variable Daphnia longispina species complex. This genetic method, based on restriction fragment length polymorphism (RFLP) of the internal transcribed
spacer region (ITS) of nuclear ribosomal DNA (rDNA) with restriction enzymes Mwo I and Sau96 I [Billiones et al., 2004. Hydrobiologia 526: 43–53], was applied to many different European populations. Results were
compared with two or more independently obtained characters (morphology, allozymes, mitochondrial DNA (mtDNA), or cloned rDNA-ITS
sequences). Individuals of most taxa were readily identified, but unexpected ITS-RFLP patterns were found in many individuals
indicated by other markers to be D. galeata or one of its hybrids. Among 43 investigated D. galeata populations (902 specimen analysed by ITS-RFLP), deviant RFLP fragment patterns occurred in 26 (i.e., more than half) of
the populations. The deviant patterns could be attributed to the loss of one single restriction site in the ITS2 region. This
loss made the distinction of D. galeata from other species unreliable, and F1 hybrids could not be identified. Future users should be aware of this shortcoming of
the Billions et al. [2004. Hydrobiologia 526: 43–53] protocol. As a solution to this problem, we present an improved genetic
identification protocol based on a simple double digestion of the rDNA-ITS region with the restriction enzymes BsrB I and EagI. Sequence analyses of rDNA-ITS clones and preliminary testing indicate that the new protocol is unaffected by the rDNA variation
which troubled the Mwo I/Sau96 I protocol. Further, the new protocol identifies all European species of the D. longispina complex, as well as their F1 hybrids. However, a wider screening is required to verify its general utility for all species,
since yet unknown variation may occur.
Guest editor: Piet Spaak
Cladocera: Proceedings of the 7th International Symposium on Cladocera 相似文献
108.
Tommy J. Rauch 《Environmental Biology of Fishes》2007,78(4):347-351
Interspecific interactions can determine the abundance and distributions of animals. Seaweed blennies, Parablennius marmoreus, and tesselated blennies, Hypsoblennius invemar, are found in barnacle cavities on offshore petroleum platforms in the northern Gulf of Mexico. I measured the interspecific
resource defense interactions between these fishes in aquaria. Seaweed blennies were dominant over tesselated blennies when
equal-sized fishes were tested. No difference in dominance was found when tesselated blennies had a 10% advantage in size.
However, tesselated blennies were able to successfully defend cavities against equal-sized competitors when given the advantage
of prior residence. This prior residence advantage persisted despite seaweed blennies having the advantage of past experience.
Seaweed blennies attain a larger size on petroleum platforms, but empty barnacle cavities are common in this environment.
Tesselated blennies are able to colonize and successfully spawn because they can enter an empty barnacle cavity, gain the
advantage of prior residence, and successfully defend this cavity. 相似文献
109.
Associations between certain odors and for instance health effects may lead to positive or negative attitudes toward these odors. However, in experiments we conducted using the Implicit Association Test (IAT), we encountered attitudes even to odor "words." The IAT is based on the principle that reaction times measuring the association between words from a target dimension (in this case, odor vs. a neutral reference category) and an attribute dimension (i.e., positive or negative words) reflect the attitude to the target, where attitude-congruent associations between target and attribute are reflected by shorter reaction times. In a first experiment, we found distinctly positive attitudes to the concept odor in a student sample, which was replicated in a second experiment. In the main experiment, subjects in the aromatherapy group, who prefer using scented consumer products for relaxation purposes, showed a significantly more positive attitude toward odor words in the IAT than a control group, who did not have such a preference. The fact that results from the implicit test were not always associated with explicitly stated attitudes toward the odor words attests to the fact that the IAT measures the attitude of interest in a different way. As such, the IAT has added value in circumstances where explicit tests can be biased. 相似文献
110.
Question: How can the U.S. National Vegetation Classification (USNVC) serve as an effective tool for classifying and mapping vegetation, and inform assessments and monitoring? Location: Voyageurs National Park, northern Minnesota, U.S.A and environs. The park contains 54 243 ha of terrestrial habitat in the sub-boreal region of North America. Methods: We classified and mapped the natural vegetation using the USNVC, with ‘alliance’and ‘association’as base units. We compiled 259 classification plots and 1251 accuracy assessment test plots. Both plot and type ordinations were used to analyse vegetation and environmental patterns. Color infrared aerial photography (1:15840 scale) was used for mapping. Polygons were manually drawn, then transferred into digital form. Classification and mapping products are stored in publicly available databases. Past fire and logging events were used to assess distribution of forest types. Results and Discussion: Ordination and cluster analyses confirmed 49 associations and 42 alliances, with three associations ranked as globally vulnerable to extirpation. Ordination provided a useful summary of vegetation and ecological gradients. Overall map accuracy was 82.4%. Pinus banksiana - Picea mariana forests were less frequent in areas unburned since the 1930s. Conclusion: The USNVC provides a consistent ecological tool for summarizing and mapping vegetation. The products provide a baseline for assessing forests and wetlands, including fire management. The standardized classification and map units provide local to continental perspectives on park resources through linkages to state, provincial, and national classifications in the U.S. and Canada, and to NatureServe's Ecological Systems classification. 相似文献