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891.
Djungarian hamsters (Phodopus sungorus) are not susceptible to stimulating effects of 6-methoxy-2-benzoxazolinone on reproductive organs 总被引:1,自引:0,他引:1
Victoria Diedrich Frank Scherbarth Susanne Jähnig Sabine Kastens Stephan Steinlechner 《Die Naturwissenschaften》2014,101(2):115-121
The secondary plant metabolite 6-methoxy-2-benzoxazolinone (6-MBOA) is abundant in vegetative parts of monocotyledons emerging in spring. This grazing protective has been shown to promote gonadal growth and, thus enable precise alignment of reproductive activity with favorable environmental conditions in a variety of seasonally breeding rodent species. Feeding and breeding ecology make the Djungarian hamster (Phodopus sungorus) a potential candidate using 6-MBOA as an acute environmental cue to optimize reproductive timing when photorefractoriness induces reproductive recrudescence. Therefore, four different experiments were designed to examine whether the hamsters’ reproductive organs are responsive to oral 6-MBOA administration under different photoperiodic conditions. Only under a long photoperiod, we found a slight increase in uterine weights. In a short photoperiod, 6-MBOA-treated hamsters showed a slight body weight gain without a change in uterine weights. However, these marginal effects are likely not to be of ecophysiological significance for reproductive timing. The results are in agreement with the common view that the annual changes in photoperiod length are not only the predominant environmental cue for Djungarian hamsters, but are also sufficient to synchronize reproductive efforts with favorable breeding conditions in highly predictable climates like the continental Asian steppes. 相似文献
892.
Since the announcement by Fleischmann and Pons that the excess enthalpy generated in the negatively polarized Pd–D-D2O system was attributable to nuclear reactions occurring inside the Pd lattice, there have been reports of other manifestations
of nuclear activities in this system. In particular, there have been reports of tritium and helium-4 production; emission
of energetic particles, gamma or X-rays, and neutrons; as well as the transmutation of elements. In this communication, the
results of Pd–D co-deposition experiments conducted with the cathode in close contact with CR-39, a solid-state nuclear etch
detector, are reported. Among the solitary tracks due to individual energetic particles, triple tracks are observed. Microscopic
examination of the bottom of the triple track pit shows that the three lobes of the track are splitting apart from a center
point. The presence of three α-particle tracks outgoing from a single point is diagnostic of the 12C(n,n′)3α carbon breakup reaction and suggests that DT reactions that produce ≥9.6 MeV neutrons are occurring inside the Pd
lattice. To our knowledge, this is the first report of the production of energetic (≥9.6 MeV) neutrons in the Pd–D system.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
893.
Remodeling the clock: coactivators and signal transduction in the circadian clockworks 总被引:1,自引:0,他引:1
Frank Weber 《Die Naturwissenschaften》2009,96(3):321-337
894.
895.
Johanna Christian Lee M. Frank Rob Olivier Ghislain Stphane Teresa Pinto Nadine Irina 《Environmental Science & Policy》2009,12(5):562-572
The goal oriented framework (GOF) for indicators has been developed as part of a comprehensive research project developing computerised tools for integrated assessment of the effects of new policies or technologies on agricultural systems (SEAMLESS-IF). The ambition has therefore been to create an indicator framework where the environmental, economic and social dimensions of sustainable development can be related to each other in a consistent way. Integrated assessment tools rely on such frameworks to capture and visualise trade-offs (antagonisms or synergies) among indicators between and within the three dimensions of sustainable development. The specific aims of this paper are to (i) present the GOF (ii) present how the GOF can be used to select indicators within the integrated assessment framework SEAMLESS-IF and (iii) discuss the advantages and limitations with the proposed approach. We show that the GOF has several advantages. Its major rewards are its relative simplicity and the possibility to link indicators to policy goals of each dimension of sustainability and thereby facilitate the comparison of the impacts of the new policy on the different dimensions. Another important feature of the GOF is its multi-scale perspective, which will enable the comparison of effects of a new policy between scales. Yet, as typical for all indicator frameworks, the GOF has also biases either instigated by the issues the included models cover or by the stakeholders’ selection of indicators. However, due to the way the GOF and its indicators are technically implemented in SEAMLESS-IF, it can easily be extended and include new indicators to increase and update its policy relevance. 相似文献
896.
The objective of this work is to characterize the heat transfer in micro end mill tools during machining operations. This analysis will aid in the design of heat dissipation strategies that could potentially increase tool life and machining precision. Tool temperatures, above the unmachined workpiece surface, have been measured using an infrared camera during slot milling of aluminum (6061-T6) and steel (1018) with 300 μm-diameter two-flute tungsten carbide end mills. The measured temperatures compare favorably with temperature distributions predicted by a two-dimensional, transient, heat transfer model of the tool. The heat input is estimated by applying Loewen and Shaw’s heat partitioning analysis. Analysis of heat transfer in the tool found that 46 s into a cut conduction through the length of the tool, storage in the tool, and convection from the surface account for 41.5%, 45%, and 13.5% of the heat generated during machining. Thermal expansion and cooling strategies are discussed. 相似文献
897.
The Mojave Desert is characterized by hot dry summers and cold winters. The red-spotted toad (Bufo (Anaxyrus) punctatus) is the predominant anuran species; yet little is known of their thermal histories and strategies to avoid temperature extremes. We measured body temperature (T(b)) in free-ranging adult toads across all four seasons of a year using implanted data loggers. There is marked individual variation in the temperatures experienced by these toads. As expected, toads generally escape extreme seasonal and diel temperature fluctuations. However, our data demonstrate a much wider estimated T(b) range than was previously assumed. Though often for short periods, red-spotted toads do experience T(b) as low as 3.1 degrees C and as high as 39.1 degrees C. All animals showed periods of prolonged thermal stability in cooler months and wider diel oscillations in warmer months. Red-spotted toad thermal history is likely a function of site choice; the exploitation of different refuges results in diverse thermal experiences. These data represent the most complete record of thermal experiences for a desert anuran and reveal greater extremes in body temperature than previously suggested. 相似文献
898.
899.
Ghosh Soumya Al-Sharify Zainab T. Maleka Mathabatha Frank Onyeaka Helen Maleke Maleke Maolloum Alhaji Godoy Liliana Meskini Maryam Rami Mina Rezghi Ahmadi Shabnam Al-Najjar Shahad Z. Al-Sharify Noor T. Ahmed Sura M. Dehghani Mohammad Hadi 《Environmental science and pollution research international》2022,29(39):58628-58647
Environmental Science and Pollution Research - This current study review provides a brief review of a natural bee product known as propolis and its relevance toward combating SARS-CoV viruses.... 相似文献
900.
Climate change is a key threat to biodiversity. To conserve species under climate change, ecologists and conservation scientists suggest 2 main conservation strategies regarding land use: supporting species’ range shifts to enable it to follow its climatic requirements by creating migration pathways, such as corridors and stepping stones, and conserving climate refugia (i.e., existing habitat areas that are somewhat buffered from climate change). The policy instruments that could be used to implement these conservation strategies have yet to be evaluated comprehensively from an economic perspective. The economic analyses of environmental policy instruments are often based on ecological effectiveness and cost-effectiveness criteria. We adapted these general criteria to evaluate policy instruments for species’ conservation under climate change and applied them to a conceptual analysis of land purchases, offsets, and conservation payments. Depending on whether the strategy supporting species’ range shifts or conserving climate refugia is selected, the evaluation of the policy instruments differed substantially. For example, to ensure ecological effectiveness, habitat persistence over time was especially important for climate refugia and was best achieved by a land-purchase policy instrument. In contrast, for the strategy supporting range shifts to be ecologically effective, a high degree of flexibility in the location of conserved sites was required to ensure that new habitat sites can be created in the species’ new range. Offset programs were best suited for that because the location of conservation sites can be chosen comparatively freely and may also be adapted over time. 相似文献