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761.
Non-parametric statistical tests are commonly used in the behavioral sciences. Researchers need to be aware that non-parameteric
methods involving ranks can perform unreliably as a result of very small amounts of noise added in the storage and manipulation
of values by computers, causing spurious reduction in the number of ties. In order to avoid this problem, researchers should
round values to an appropriate number of decimal places prior to the ranking procedure to ensure that data points whose values
cannot be separated according to the precision of their measurement are recorded as having identical rank. We also recommend
exact rather than asymptotic evaluation of p values in non-parametric statistical tests. 相似文献
762.
Different uptake routes of contaminants were analysed with focus on particle-bound pollutants. Bioavailability of cadmium was determined with quantitative mRNA-analysis using the expression of the “cadmium responsive gene” cdr- in Caenorhabditis elegans. Comparable experiments were performed with fluoranthene as organic pollutant. The exposure in medium was compared with and without bacteria as food particles. Both bioaccumulation and toxic effects were most influenced via the food exposure. Inorganic particles increased also the uptake of cadmium, but significantly less than food or mixtures of food and inorganic particles. The exposure of fluoranthene reduced the reproduction of the nematodes, if a gene expression threshold was exceeded. However, bioavailabilty of fluoranthene via food particles caused a faster response of the cyp-expression. Thus means, the internal availability is crucial influenced by the uptake route. 相似文献
763.
The genetic structure of benthic marine invertebrates is often described as “chaotic” when genetic structure cannot be explained and barriers to dispersal and gene flow cannot be identified. Here, chaotic patterns of genetic structure for the polychaete Pygospio elegans (Claparède) sampled at 16 locations from the heterogeneous Isefjord–Roskilde Fjord estuary complex in Denmark were found. There was no isolation by distance, and the geography of the estuary complex did not seem to pose a barrier to dispersal and gene flow in this species. We investigated whether characteristics of the environment could be related to the genetic structure and possibly restrict gene flow in this species. Additionally, since P. elegans is poecilogonous, producing larvae with different pelagic developmental periods, we investigated whether observed developmental modes in the samples might clarify the genetic patterns. None of the tested factors explained the population genetic structure. However, a high degree of relatedness among individuals in almost all samples was found. Samples with a larger percentage of young individuals had more related individuals, suggesting that different cohorts could be comprised of individuals with different degrees of relatedness. Relatedness within a site could be increased by limited larval dispersal, collective dispersal of related larvae, sweepstakes reproductive success, or asexual reproduction, but distinguishing between these requires further study. Using a “seascape genetics” approach allowed us to investigate some of the numerous potential factors that could influence population genetic structure in a poecilogonous species. 相似文献
764.
Häring Ivo Fehling-Kaschek Mirjam Miller Natalie Faist Katja Ganter Sebastian Srivastava Kushal Jain Aishvarya Kumar Fischer Georg Fischer Kai Finger Jörg Stolz Alexander Leismann Tobias Hiermaier Stefan Carli Marco Battisti Federica Makri Rodoula Celozzi Giuseppe Belesioti Maria Sfakianakis Evangelos Agrafioti Evita Chalkidou Anastasia Papadakis George Fuggini Clemente Bolletta Fabio Neri Alberto Giunta Guiseppe Scheithauer Hermann Höflinger Fabian Schott Dominik J. Schindelhauer Christian Köhler Sven Linkov Igor 《The Environmentalist》2021,41(2):286-329
Environment Systems and Decisions - Organizational and technical approaches have proven successful in increasing the performance and preventing risks at socio-technical systems at all scales.... 相似文献
765.
Stephan Jänsch Johannes Bauer David Leube Mathias Otto Jörg Römbke Hanka Teichmann Karolina Waszak 《Environmental Sciences Europe》2018,30(1):38
Background
Few suitable and standardized test methods are currently available to test the effects of genetically modified plants (GMP) on non-target organisms. To fill this gap and improve ecotoxicological testing for GMP, we developed a new soil ecotoxicological test method using sciarid larvae as test organisms.Results
Bradysia impatiens was identified as a candidate species. Species of the genus Bradysia occur in high numbers in European agroecosystems and B. impatiens can be reared in the laboratory in continuous culture. A functional basic test design was successfully developed. Newly hatched larvae were used as the initial life stage to cover most of the life cycle of the species during the test. Azadirachtin was identified as a suitable reference substance. In several tests, the effects of this substance on development time and emergence rate varied for different temperatures and test substrates. The toxicity was higher at 25 °C compared to 20 °C and in tropical artificial soil compared to coconut fiber substrate.Conclusions and outlook
Results suggest that the developed test system is suitable to enter a full standardization process, e.g., via the Organisation for Economic Co-operation and Development. Such a standardization would not only assist the risk assessment of GMP, but could include other stressors such as systemic pesticides or veterinary pharmaceuticals reaching the soil, e.g., via spreading manure. The use of sciarid flies as test organisms supports recommendations of EFSA, which stressed the ecological role of flies and encouraged including Diptera into test batteries.766.
All chemicals form non-extractable residues (NER) to various extents in environmental media like soil, sediment, plants and animals. NER can be quantified in environmental fate studies using isotope-labeled (such as 14C or 13C) tracer compounds. Previous NER definitions have led to a mismatch of legislation and state of knowledge in research: the residues are assumed to be either irreversibly bound degradation products or at least parts of these residues can be released. In the latter assumption, soils and sediments are a long-term source of slowly released residues. We here present a conceptual experimental and modeling approach to characterize non-extractable residues and provide guidance how they should be considered in the persistence assessment of chemicals and pesticides. Three types of NER can be experimentally discriminated: sequestered and entrapped residues (type I), containing either the parent substance or xenobiotic transformation products or both and having the potential to be released, which has indeed been observed. Type II NER are residues that are covalently bound to organic matter in soils or sediments or to biological tissue in organisms and that are considered being strongly bound with very low remobilization rates like that of humic matter degradation rates. Type III NER comprises biogenic NER (bioNER) after degradation of the xenobiotic chemical and anabolic formation of natural biomolecules like amino acids and phospholipids, and other biomass compounds. We developed the microbial turnover to biomass (MTB) model to predict the formation of bioNER based on the structural properties of chemicals. Further, we proposed an extraction sequence to obtain a matrix containing only NER. Finally, we summarized experimental methods to distinguish the three NER types. Type I NER and type II NER should be considered as potentially remobilizable residues in persistence assessment but the probability of type II release is much lower than that of type I NER, i.e., type II NER in soil are “operationally spoken” irreversibly bound and can be released only in minute amounts and at very slow rates, if at all. The potential of remobilization can be evaluated by chemical, physical and biological methods. BioNER are of no environmental concern and, therefore, can be assessed as such in persistence assessment. The general concept presented is to consider the total amount of NER minus potential bioNER as the amount of xenoNER, type I?+?II. If a clear differentiation of type I and type II is possible, for the calculation of half-life type I NER are considered as not degraded parent substance or transformation product(s). On the contrary, type II NER may generally be considered as (at least temporarily) removed. Providing proof for type II NER is the most critical issue in NER assessment and requires additional research. If no characterization and additional information on NER are available, it is recommended to assess the total amount as potentially remobilizable. We propose our unified approach of NER characterization and evaluation to be implemented into the persistence and environmental hazard assessment strategies for REACH chemicals and biocides, human and veterinary pharmaceuticals, and pesticides, irrespective of the different regulatory frameworks. 相似文献
767.
768.
769.
Marie-Lise Schläppy Sandra I. Schöttner Gaute Lavik Marcel M. M. Kuypers Dirk de Beer Friederike Hoffmann 《Marine Biology》2010,157(3):593-602
Aerobic and anaerobic microbial key processes were quantified and compared to microbial numbers and morphological structure
in Mediterranean sponges. Direct counts on histological sections stained with DAPI showed that sponges with high microbial
abundances (HMA sponges) have a denser morphological structure with a reduced aquiferous system compared to low microbial
abundance (LMA) sponges. In Dysidea avara, the LMA sponge, rates of nitrification and denitrification were higher than in the HMA sponge Chondrosia reniformis, while anaerobic ammonium oxidation and sulfate reduction were below detection in both species. This study shows that LMA
sponges may host physiologically similar microbes with comparable or even higher metabolic rates than HMA sponges, and that
anaerobic processes such as denitrification can be found both in HMA and LMA sponges. A higher concentration of microorganisms
in the mesohyl of HMA compared to LMA sponges may indicate a stronger retention of and, hence, a possible benefit from associated
microbes. 相似文献
770.
Investigations of factors affecting feeding success in fish larvae require knowledge of the scales of variability of the
feeding process itself and the indices used to assess this variability. In this study, we measured short-term (diel) variability
in feeding rates of wild haddock (Melanogrammus aeglifinus) larvae four times per day during a 10-d cruise in the northern North Sea. Feeding activity was evaluated using indices of
gut fullness, prey digestive state and biochemical measurements (tryptic enzyme activity). The gut fullness and the enzyme
activity indices indicated moderate to high rates of food consumption throughout the cruise. Time series analysis of the three
indices showed significant diel variability in all indices and enabled identification of significant lags between food uptake
and peak digestive enzyme activity. The typical pattern of food consumption and digestion was characterized by maximal ingestion
of prey early in the evening (19:00 hrs) and peak digestive enzyme activity at 01:00 hrs. The time scale over which enzyme
activities reacted to prey ingestion was ca. 6 h, and is consistent with expectations from controlled laboratory experiments
with other larval fish species. Significant diel variability in tryptic enzyme activity suggests that attempts to relate this
measure of feeding success to other variables (e.g. food concentrations) should take care to accommodate natural cycles in
feeding activity before making statistical comparisons.
Received: 29 October 1998 / Accepted: 18 June 1999 相似文献