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41.
Ecological indicators are often collected to detect and monitor environmental change. Statistical models are used to estimate natural variability, pre-existing trends, and environmental predictors of baseline indicator conditions. Establishing standard models for baseline characterization is critical to the effective design and implementation of environmental monitoring programs. An anthropogenic activity that requires monitoring is the development of Marine Renewable Energy sites. Currently, there are no standards for the analysis of environmental monitoring data for these development sites. Marine Renewable Energy monitoring data are used as a case study to develop and apply a model evaluation to establish best practices for characterizing baseline ecological indicator data. We examined a range of models, including six generalized regression models, four time series models, and three nonparametric models. Because monitoring data are not always normally distributed, we evaluated model ability to characterize normal and non-normal data using hydroacoustic metrics that serve as proxies for ecological indicator data. The nonparametric support vector regression and random forest models, and parametric state-space time series models generally were the most accurate in interpolating the normal metric data. Support vector regression and state-space models best interpolated the non-normally distributed data. If parametric results are preferred, then state-space models are the most robust for baseline characterization. Evaluation of a wide range of models provides a comprehensive characterization of the case study data, and highlights advantages of models rarely used in Marine Renewable Energy environmental monitoring. Our model findings are relevant for any ecological indicator data with similar properties, and the evaluation approach is applicable to any monitoring program. 相似文献
42.
B. Canguilhem A. Malan M. Masson-Pévet P. Nobelis R. Kirsch P. Pévet J. Le Minor 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,163(8):690-698
Temporal patterns of hibernation were studied by continuous monitoring of body temperature by radiotelemetry over 6 months in European hamsters, Cricetus cricetus, at constant temperature and photoperiod. Entrances into hibernation occurred mostly at the end of the night (0000–0800 hours), while arousals were randomly distributed between day and night. This is at variance with a control of bout duration by a clock with a period of 24 h. Consequently, the timing of entrances implies a phase-resetting of the circadian clock on each arousal. Persistence of circadian rhythmicity with a period different from 24 h during deep hibernation was investigated examining whether the durations of torpor bouts were integer multiples of a constant period. A non-parametric version of the classical contingency test of periodicity was developed for this purpose. Periods ranging from 21 to 29 h were tested. Nine animals out of ten showed at least one significant period in this range (P<0.01), either below 24 h (21.8±0.5 h, n=4) or above (27.3±0.5 h, n=7). However, we have found a theoretical model of bout durations for which the contingency test of periodicity sometimes gives false significant results. This indicates that the power of the test is weak. With this reservation our results suggest that a circadian oscillator controls the duration of a bout of hibernation, which would occur after an integer, but variable and possibly temperature-dependent number of cycles.Abbreviations b
a contingency test (see Appendix)
- SCN
suprachiasmatic nuclei
-
period
-
T
b
body temperature 相似文献
43.
Least absolute deviations estimation for ARCH and GARCH models 总被引:4,自引:0,他引:4
44.
C. Uluoglu D. B. Durakoglugil C. Karasu G. Ozbey A. Gunes H. Zengil 《Chronobiology international》2013,30(6):1081-1094
The aim of this study was to investigate whether time‐dependent variations in the relaxant effect of acetylcholine, an endothelium‐dependent vasorelaxant via muscarinic receptors, and isoprenaline, a nonselective β‐adrenoceptor agonist in rat aorta, are influenced by streptozotocin (STZ)‐induced experimental diabetes. Adult male rats were divided randomly into two groups: control and STZ‐induced (STZ, 55 mg/kg, intraperitoneal) diabetes. The animals were synchronized to a 12∶12 h light‐dark cycle (lights on 08∶00 h) and sacrificed at six different times of day (1, 5, 9, 13, 17, and 21 hours after lights on; HALO) eight weeks after STZ injection. The in vitro responsiveness of thoracic aorta rings obtained from control and diabetic rats to acetylcholine (10?9–10?5 M) and isoprenaline (10?10–10?3 M) was determined in six different times. EC50 (the concentration inducing half of the maximum response) values and maximum responses were calculated from cumulative concentration‐response curves of the agonists and were analyzed with respect to time and STZ treatment. Treatment, time, and interactions between treatment and time were tested by two‐way analysis of variance (ANOVA). To analyze differences due to biological time, one‐way ANOVA was used. STZ treatment did not significantly change EC50 values or maximum responses for both agonists. There were statistically significant time‐dependent variations in the EC50 values for isoprenaline and maximum responses for both acetylcholine and isoprenaline in control groups by one‐way ANOVA, but significant time‐dependent variations disappeared in the aortas isolated from STZ‐induced diabetic rats. The vasodilator responses to acetylcholine and isoprenaline failed to show any significant interaction (treatment×time of study) between STZ treatment and time of sacrifice in both EC50 values and maximum responses by two‐way ANOVA. These results indicate there is a basic temporal pattern in the responses to acetylcholine and isoprenaline in rat aorta which continues in diabetes. It is shown for the first time that experimental diabetes does not change the 24 h pattern of responses to acetylcholine and isoprenaline, and that time‐dependent variations in the responses to these agonists disappear in diabetic animals. Although further studies are required to define the underlying mechanism(s) of these findings, results suggest that experimental diabetes can modify the time‐dependent vasorelaxant responses of rat aorta. This may help to understand the circadian rhythms in cardiovascular physiology and pathology or in drug effects in diabetes. 相似文献
45.
Jørgen Berge Paul E. Renaud Ketil Eiane Bjørn Gulliksen Finlo R. Cottier Øystein Varpe Torleiv Brattegard 《Polar Biology》2009,32(7):953-961
Whereas Arctic benthic decapods are not a species-rich group, they can dominate the local epifauna and play important roles
in the ecosystem. We studied the decapod fauna from Isfjorden (Svalbard, Norway, 78°N) by sampling from 22 stations and comparing
with 50 and 100-year-old data from the same localities. Our data provide no evidence of changes in the species composition
of decapods during the last 50 years. Hence, we do not observe the poleward shift of species found in several pelagic communities
in the North Atlantic. However, there is statistical evidence for changes in the community structure between 1908 and both
1958 and 2007. The main change is a shift towards communities more dominated by the spider crab Hyas araneus and the hermit crab Pagurus pubescens in 2007, and with a corresponding decrease in the two shrimp species Lebbeus polaris and Spirontocaris spinus. These shrimps are specialist predators compared to the more opportunistic, scavenging crabs. We argue that increased disturbance
levels may be a causal factor behind the observed community change, with likely sources of disturbance including trawling
and climatic fluctuations. 相似文献
46.
Fabian Alperth Božena Mitić Stefanie Mayer Željan Maleš Olaf Kunert Dario Hruševar 《Plant biosystems》2019,153(2):317-324
Iris adriatica Trinajsti? ex Miti? (Iridaceae L.) is a strictly endemic taxon from Croatia. It is a rhizomatous dwarf plant from the I. pumila complex with a distribution area limited to the Croatian part of the Mediterranean area, mainly central Dalmatia. The genus Iris is known for its richness in isoflavonoids which also play a significant role in chemotaxonomy and biological activity. Hence, in the current study, different plant batches of I. adriatica collected in early spring of 2016 were analysed for their phytochemical profiles and qualitatively compared. UHPLC-PDA-ESI-MS analyses of methanolic rhizome extracts were performed. Altogether, 36 compounds, representing isoflavonoids (including 6,7-methylendioxy derivatives), benzophenones and xanthones were found as aglycones or in glycosidically bound form to be the main constituent groups of I. adriatica rhizomes. Qualitative results were identical between different batches of plant material from collection sites in central Dalmatia, they differed only in quantity. For some phenolic compounds of I. adriatica, chemotaxonomic relevance was detected. 相似文献
47.
48.
Chisholm James S. Quinlivan Julie A. Petersen Rodney W. Coall David A. 《Human nature (Hawthorne, N.Y.)》2005,16(3):233-265
Life history theory suggests that in risky and uncertain environments the optimal reproductive strategy is to reproduce early
in order to maximize the probability of leaving any descendants at all. The fact that early menarche facilitates early reproduction
provides an adaptationist rationale for our first two hypotheses: that women who experience more risky and uncertain environments
early in life would have (1) earlier menarche and (2) earlier first births than women who experience less stress at an early
age. Attachment theory and research provide the rationale for our second two hypotheses: that the subjective early experience
of risky and uncertain environments (insecurity) is (3) part of an evolved mechanism for entraining alternative reproductive
strategies contingent on environmental risk and uncertainty and (4) reflected in expected lifespan. Evidence from our pilot
study of 100 women attending antenatal clinics at a large metropolitan hospital is consistent with all four hypotheses: Women
reporting more troubled family relations early in life had earlier menarche, earlier first birth, were more likely to identify
with insecure adult attachment styles, and expected shorter lifespans. Multivariate analyses show that early stress directly
affected age at menarche and first birth, affected adult attachment in interaction with expected lifespan, but had no effect
on expected lifespan, where its original effect was taken over by interactions between age at menarche and adult attachment
as well as age at first birth and adult attachment. We discuss our results in terms of the need to combine evolutionary and
developmental perspectives and the relation between early stress in general and father absence in particular.
This work was supported by The University of Melbourne Department of Obstetrics and Gynaecology.
James S. Chisholm is Professor in the School of Anatomy and Human Biology at the University of Western Australia. He is an
anthropologist whose interests lie in the fields of human behavioral biology, evolutionary ecology, life history theory, and
parental investment theory, where he focuses on infant social-emotional development, the development of reproductive strategies,
and the integration of evolutionary, developmental, and cultural psychology and public health.
Julie A. Quinlivan is Associate Professor in Obstetrics and Gynaecology at the University of Melbourne and Head of the Maternity
Care Program at the Royal Women’s Hospital, Melbourne. Her interests are teenage pregnancy, domestic violence, child abuse
prevention, and high-risk pregnancy.
Rodney W. Petersen is Senior Lecturer in Obstetrics and Gynaecology at the University of Melbourne and Senior Consultant in
Obstetrics and Gynaecology at the Royal Women’s Hospital and Sunshine Hospital in Melbourne. His interests are in psychosocial
aspects of women’s health and cancer.
David A. Coall is a Ph.D. student in the School of Anatomy and Human Biology at the University of Western Australia. His main
interest lies in the application of evolutionary theory within an epidemiological framework. He is currently working on the
synthesis of life history theory, parental investment theory, and parent-offspring conflict theory in exploring factors that
influence variation in human birth weight and placental weight. 相似文献
49.
Stephanie Jane Peacock Martin Krkošek Mark Alun Lewis Subhash Lele 《Ecology and evolution》2017,7(2):762-770
The statistical tools available to ecologists are becoming increasingly sophisticated, allowing more complex, mechanistic models to be fit to ecological data. Such models have the potential to provide new insights into the processes underlying ecological patterns, but the inferences made are limited by the information in the data. Statistical nonestimability of model parameters due to insufficient information in the data is a problem too‐often ignored by ecologists employing complex models. Here, we show how a new statistical computing method called data cloning can be used to inform study design by assessing the estimability of parameters under different spatial and temporal scales of sampling. A case study of parasite transmission from farmed to wild salmon highlights that assessing the estimability of ecologically relevant parameters should be a key step when designing studies in which fitting complex mechanistic models is the end goal. 相似文献
50.