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Fitting generalised linear models (GLMs) with more than one predictor has become the standard method of analysis in evolutionary
and behavioural research. Often, GLMs are used for exploratory data analysis, where one starts with a complex full model including
interaction terms and then simplifies by removing non-significant terms. While this approach can be useful, it is problematic
if significant effects are interpreted as if they arose from a single a priori hypothesis test. This is because model selection
involves cryptic multiple hypothesis testing, a fact that has only rarely been acknowledged or quantified. We show that the
probability of finding at least one ‘significant’ effect is high, even if all null hypotheses are true (e.g. 40% when starting
with four predictors and their two-way interactions). This probability is close to theoretical expectations when the sample
size (N) is large relative to the number of predictors including interactions (k). In contrast, type I error rates strongly exceed even those expectations when model simplification is applied to models
that are over-fitted before simplification (low N/k ratio). The increase in false-positive results arises primarily from an overestimation of effect sizes among significant
predictors, leading to upward-biased effect sizes that often cannot be reproduced in follow-up studies (‘the winner's curse’).
Despite having their own problems, full model tests and P value adjustments can be used as a guide to how frequently type I errors arise by sampling variation alone. We favour the
presentation of full models, since they best reflect the range of predictors investigated and ensure a balanced representation
also of non-significant results. 相似文献
375.
Alexandra Houssaye Renaud Boistel Wolfgang Böhme Anthony Herrel 《Die Naturwissenschaften》2013,100(11):997-1006
Snakes are a very speciose group of squamates that adapted to various habitats and ecological niches. Their ecological diversity is of particular interest and functional demands associated with their various styles of locomotion are expected to result in anatomical specializations. In order to explore the potential adaptation of snakes to their environment we here analyze variation in vertebral structure at the microanatomical level in species with different locomotor adaptations. Vertebrae, being a major element of the snake body, are expected to display adaptations to the physical constraints associated with the different locomotor modes and environments. Our results revealed a rather homogenous vertebral microanatomy in contrast to what has been observed for other squamates and amniotes more generally. We here suggest that the near-absence of microanatomical specializations in snake vertebrae might be correlated to their rather homogeneous overall morphology and reduced range of morphological diversity, as compared to lizards. Thus, snakes appear to retain a generalist inner morphology that allows them to move efficiently in different environments. Only a few ecologically highly specialized taxa appear to display some microanatomical specializations that remain to be studied in greater detail. 相似文献
376.
Clara Illi Josefine Koenigbauer Wolfgang Henrich Laura Fangmann Charlotte Reinhardt Sophia Ossmann Alexander Weichert 《黑龙江环境通报》2023,43(11):1459-1462
Germline pathogenic variants in isocitrate dehydrogenase 1 (IDH1) can lead to a rare neurodevelopmental disorder called metaphyseal chondromatosis with D-2-hydroxyglutaric aciduria, including severe skeletal and cerebral anomalies. To the best of our knowledge, no prenatal case of an IDH1 pathogenic variant has been reported in literature. Somatic sequence variants in IDH1/2 genes are described in distinct cancers, premalignant diseases and rare inherited metabolic disorders. Amniocentesis and further genetic testing including trio exome sequencing were performed due to suspicious findings on a second trimester routine prenatal ultrasound examination. The fetus was found to have growth restriction, cerebral abnormalities (ex vacuo hydrocephalus, cerebellar and vermian hypoplasia, corpus callosum dysgenesis), brachycephaly, narrow chest, persistent left superior vena cava, liver calcifications, hyperechogenic bowel, short tubular bones and joint contractures. A de novo heterozygous variant in the IDH1 gene was detected via trio exome sequencing. The prenatal diagnosis of a de novo pathogenic variant in IDH1 in a fetus with the described phenotype, obtained through trio exome sequencing, helped parents and providers with an informed decision making about pregnancy management. 相似文献
377.
Human exposure to polycyclic aromatic hydrocarbons (PAH) via daily liquid consumption (primarily through the intake of drinking water) is estimated using model calculations based on the indicator substance benzo(a)pyrene. The additional contribution to oral exposure by a consumption of solid nutrients, and by soil and dust ingestion, are evaluated using typical background conditions in Germany (conurbations of North-Rhine-Westphalia). A series of further scenarios is then applied to examine the influence of elevated PAH concentrations in the daily intake of liquid. The degree of PAH exposure via liquid only equals or exceeds the exposure via the solid fraction of the diet under very specific conditions. The contribution via liquid consumption to a total lifelong exposure of both BAP and PAH caused by dietary intake may be estimated as approximately 4 %. It increases to 56 % under a level equivalent to the Dutch intervention value for groundwater and reaches 90 % under a level equivalent to the WHO guideline for drinking water. Considering occupants who live on PAH contaminated garden allotments with private wells, the highest degree of exposure is caused by vegetables followed by house dust, then liquid diet and finally by soil. Finally, the model approach is used for evaluating the success of potential remedial treatments with respect to exposure reduction. In addition to the application of average values, conservative estimates of exposure in terms of 95 % values are set out in this publication based on sumulation methodologies. 相似文献
378.
379.
Schröder HC Brandt D Schlossmacher U Wang X Tahir MN Tremel W Belikov SI Müller WE 《Die Naturwissenschaften》2007,94(5):339-359
Biomineralization, biosilicification in particular (i.e. the formation of biogenic silica, SiO2), has become an exciting source of inspiration for the development of novel bionic approaches following “nature as model”.
Siliceous sponges are unique among silica forming organisms in their ability to catalyze silica formation using a specific
enzyme termed silicatein. In this study, we review the present state of knowledge on silicatein-mediated “biosilica” formation
in marine sponges, the involvement of further molecules in silica metabolism and their potential application in nanobiotechnology
and medicine.
Werner E. G. Müller dedicated this study to Prof. Vera Gamulin (Rudjer Boskovic Institute, Zagreb, Croatia) in honour of her
unique contributions in molecular evolution. 相似文献
380.
Tim Ruploh Hans-Joachim Bischof Nikolaus von Engelhardt 《Behavioral ecology and sociobiology》2013,67(2):175-184
Adolescence is the pivotal transitional phase during which animals become sexually and socially mature and acquire the skills to cope with a variety of environmental challenges on their own. We investigated in a bird species, the zebra finch, how the social environment experienced during this period influences their behaviour in a sexual context. Zebra finches were kept in pairs (male–female or male–male) or larger mixed-sex groups (three males and three females) during adolescence and the long-term consequences were studied on courtship behaviour, aggressiveness and attractiveness in 42 males. To investigate the stability of the observed effects over time, all behavioural tests were repeated approximately 4 months after the initial recordings. Males that grew up with a single female showed the most intense courtship and highest aggressiveness and were most attractive to females, while group-reared males had the lowest courtship and aggressiveness and were the least attractive. The observed differences in courtship and aggressiveness were stable, while the differences in attractiveness disappeared over time. These findings are very similar to earlier studies on guinea pigs, indicating that the observed effects represent a general phenomenon, not restricted to mammals with a similar function and presumably also similar underlying mechanisms. 相似文献