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741.
An improved automatic recording apparatus for determining the filtration rate of Mytilus edulis as a function of size and algal concentration 总被引:1,自引:0,他引:1
An automatic recording apparatus for measuring the filtration rate in suspension-feeding bivalves is described. The concentration of algae in the experimental medium is kept constant throughout each experiment by addition of Phaeodactylum tricornutum from a chemostat. Within the range of body size 5.7 to 283 mg (W=dry weight of tissues), the filtration rate (F=ml min-1) at 15°C in Mytilus edulis L. follows the allometric equation F=0.85 W
0.72. Within the concentrations 0.18 to 0.70 mg algal dry weight l-1, the filtration rate in mussels of 132 mg dry flesh weight ranges from 33.1 to 41.0 ml min-1. At 0.18 mg algal dry weight l-1 the mussels filter continuously for 20 h, with a high constant rate that presumably represents the water transport capacity under optimal laboratory conditions. 相似文献
742.
The increasing amount of UV-B radiation (280 to 320 nm) reaching the earth's surface could endanger transparent fish and
zooplankton in upper water layers. Previous studies on marine fish eggs and larvae focused mainly on the effects of high,
lethal doses of ultraviolet irradiation. Now a sensitive test for accumulated, sublethal impairments of physiological performance
has been established. In developing fish larvae (Pleuronectes platessa L.), the respiratory control responses to hypoxia were evaluated by combining a biocybernetical approach and a novel optical
test system. Before testing respiratory control behavior, the larvae were irradiated with light containing UV-B (test individuals)
or free from it (control individuals). Differences in the physiological reactions of these larvae were detected by biocybernetical
analysis (linear systems analysis) of respiratory control. The analysis was based on the evaluation of changes in ventilatory
rate caused by sinusoidally modulated partial pressures of ambient oxygen. The ventilatory movements of the larvae were recorded,
analyzed and evaluated by video microscopy and digital image processing. After several days of irradiation with moderate UV-B
doses or intensities (8.6 kJ m−2 d−1, corresponding to an irradiance of 0.24 W m−2 for 10 h), sublethal impairments of respiratory control could be detected in plaice larvae by this method; both the linearity
of respiratory control itself and the parameters of linear control behavior were affected by UV-B. Concerning environmental
implications, the results must still be interpreted cautiously, because natural irradiation conditions are more complex than
the artificial regimen. Our biocybernetical approach will be useful for further studies on sublethal impairments of physiological
functions caused by UV-B in fish and other transparent marine or limnic animal groups. In addition, the method could be used
to test the sublethal impact of chemical contaminants.
Received: 4 November 1997 / Accepted: 6 May 1998 相似文献
743.
U. Postel G. Petrausch S. Riestenpatt D. Weihrauch J. Malykh W. Becker D. Siebers 《Marine Biology》1998,130(3):407-416
Inhibition of Na+/K+-ATPase from gill plasma membranes of the shore crab Carcinus maenas by cadmium was investigated and compared with inhibitory effects by known antagonists (ouabain and Ca2+). For comparative considerations the Cd2+-inhibition of the enzyme from dog kidney was also tested. Na+/K+-ATPase from dog kidney and from crab gill differed greatly in sensitivity against ouabain. The inhibition constant K
i of the dog enzyme amounted to 9.1 × 10−7 mol l−1, i.e. more than 300-fold smaller than the K
i of 2.9 × 10−4 mol l−1 determined for the crab enzyme. Ca2+ inhibited the activity of Na+/K+-ATPase from crab gill plasma membranes with a K
i of 4.3 × 10−4 mol l−1. The Na+/K+-ATPase from crab gill was inhibited by Cd2+ with a K
i of 9.1 × 10−5 mol l−1. Cd2+ inhibited the Na+/K+-ATPase from dog kidney with a K
i (6.4 × 10−5 mol l−1) comparable to that observed in the crab gill enzyme. Under experimental conditions Cd2+-inhibition of Na+/K+-ATPase was irreversible. Repeated washing, centrifugation and homogenization of the plasma membranes (four times) with Cd2+-free buffer did not restore any activity lost in the presence of 1 × 10−3 mol l−1 Cd2+. Since ouabain-insensitive (nonspecific) ATPases in the plasma membrane fraction of crab gills were inhibited by Cd2+ in the same way as Na+/K+-ATPase, the heavy metal is considered as an unspecific ATPase inhibitor. Comparing these results with literature data on
Cd2+-binding to electrophoretically separated proteins suggests that Na+/K+-ATPase is a Cd2+-binding enzyme. The results obtained on Na+/K+-ATPase were reflected by Cd2+-inhibition of the branchial ion-transport functions depending on this enzyme. The transepithelial short-circuit current of
isolated gill half lamellae, a direct measure of area-specific active ion uptake, and the transepithelial potential difference
of isolated, perfused whole gills, also indicative of active ion uptake, were inhibited by the heavy metal in a time- and
dose-dependent mode. Remarkably these inhibitions were also irreversible. These findings are ecologically and biomedically
significant: even when the actual environmental or tissue concentrations measured are low, biological microstructures such
as Na+/K+-ATPase may accumulate the heavy metal by tight binding over prolonged periods until the first inhibitory effects occur.
Received: 25 June 1997 / Accepted: 25 August 1997 相似文献
744.
Growth and grazing loss rates of naturalPhaeocystis sp. single cells were measured using a seawater dilution technique. Measurements were performed during an intensePhaeocystis sp. bloom in the North Sea between 19 April and 5 May 1988. Experimental results yielded rapid carbon turnover rates. Population growth rates varied from 0.033 to 0.098 h–1, grazing loss rates from 0.037 to 0.174 h–1. From measured growth rates, average doubling rages of 1.3 doublings d–1 were calculated. The growth rates would have resulted in maximum carbon production rates of 146 mg C m–3 d–1. Grazing rates increased in the course of the bloom and exceeded growth rates at the end. Grazing loss was caused primarily by microzooplankton feeding. Ciliates and heterotrophic dinoflagellates were identified as the major potential consumers of single cells ofPhaeocystis sp. at the beginning of the bloom. The grazing impact of larger microzooplankton species appeared to increase during the progressing bloom. 相似文献
745.
746.
Particle trajectories of 6.4m Latex spheres were recorded by video, both near an isolated blue mussel, Mytilus edulis, gill filament and, in place of an intact interfilamentary canal, in a model canal of width 200, 100 or 70m, formed by a transparent plate positioned next to a gill filament. Each arrangement was placed in a 2 x 10 x 10 cm test vessel filled with seawater. Serotonin (nerve-transmitter) stimulation was used to activate lateral cilia and to either lock latero-frontal cirri at the end of an active stroke (10-5
M), or to activate them (10-6
M), yielding lateral cilia beat frequencies of 19 and 16 Hz, respectively. With latero-frontal cirri locked, image analysis of particle tracks gave maximum velocities of ca. 2.9±0.2mm s-1 close to the tips of lateral cilia, for both isolated filament and model canal cases. Experimental velocity profiles along the 200-m wide model canal were recorded and used as good approximations to the fluid velocity because of the low Reynolds number. A two-dimensional steady model was proposed for the gill pump, assumed to only comprise lateral cilia. This model was solved numerically for the experimental model, canal in the vessel and the results showed satisfactory agreement with experimental volocity profiles from particle tracks. The numerical approach was also applied to a model of a single interfilamentary canal in the vessel. The resulting mean velocity in the canal was 1.70 mm s-1, but the resistance to flow in the model was less than that in an intact mussel gill. Video graphs of particle tracks indicated that active latero-frontal cirri play a role in the transfer of particles from through current to frontal current, probably by means of a strong interaction through the motion of intervening fluid rather than through a direct physical contact. M. edulis specimens used in the present study were collected in 1990 at Helsingør and in 1991 at Kerteminde, Denmark. 相似文献
747.
Sindhe VR Veeresh MU Kulkarni RS 《Journal of environmental biology / Academy of Environmental Biology, India》2002,23(2):137-141
The ovarian and hepatic protein, lipid and cholesterol content were estimated in the fish, N. notopterus after exposing it to heavy metals at sublethal concentrations. The protein, lipid and cholesterol content of ovary and liver got reduced and amongst the three exposures (mercuric chloride, cadmium chloride and their combination) it was significantly reduced in the order of (HgCl2>HgCl2>+CdCl2>CdCl2>control). The above results indicated that HgCl2 is highly toxic and its toxicity gets reduced in combination. 相似文献
748.
749.
750.