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131.
Huimin Wang Nobuko Saigusa Susumu Yamamoto Hiroaki Kondo Takashi Hirano Atsushi Toriyama Yasumi Fujinuma 《Atmospheric environment (Oxford, England : 1994)》2004,38(40):7021-7032
Larch forests are distributed extensively in the east Eurasian continent and are expected to play a significant role in the terrestrial ecosystem carbon cycling process. In view of the fact that studies on carbon exchange for this important biome have been very limited, we have initiated a long-term flux observation in a larch forest ecosystem in Hokkaido in northern Japan since 2000. The net ecosystem CO2 exchange (NEE) showed large seasonal and diurnal variation. Generally, the larch forest ecosystem released CO2 in nighttime and assimilated CO2 in daytime during the growing season from May to October. The ecosystem started to become a net carbon sink in May, reaching a maximum carbon uptake as high as 186 g C m−2 month−1 in June. With the yellowing, senescing and leaf fall, the ecosystem turned into a carbon source in November. During the non-growing season, the larch forest ecosystem became a net source of CO2, releasing an average of 16.7 g C m−2 month−1. Overall, the ecosystem sequestered 141–240 g C m−2 yr−1 in 2001. The NEE was significantly influenced by environmental factors. Respiration of the ecosystem, for example, was exponentially dependent on air temperature, while photosynthesis was related to the incident PAR in a manner consistent with the Michaelis–Menten model. Although the vapor pressure deficit (VPD) was scarcely higher than 15 hPa, the CO2 uptake rate was also depressed when VPD surpassed 10 hPa. 相似文献
132.
Mediated electrochemical reduction was applied to the dechlorination of polychlorinated biphenyls (PCBs) in tetra-n-butylammonium perchlorate/dimethylformamide solution. Rapid and complete dechlorination was possible with biphenyl or naphthalene as the mediator, whereas the reaction was much slower with anthracene or 9,10-diphenylanthracene. The reaction rate was so high with naphthalene or biphenyl radical anion that differences in reactivity could not be observed between congeners. Side reactions, other than biphenyl formation, could occur depending upon the mediators and the substrates, but contributed less than 10% of the total products in the case of naphthalene-mediated dechlorination. Almost all chloride ion formed in the dechlorination remained in the cathode solution. The order of the reaction was determined to be 0.5 for the substrate and 1 for the mediator (naphthalene) in the dechlorination of 2-chlorobiphenyl; identical to results for the mediated dechlorination of 1-chloronaphthalene. The reaction rate in practical PCB dechlorination could be estimated with the use of the initial concentration of the mediator and chlorine content of the solution provided that the problem of the deactivation of the electrode surface could be solved. 相似文献
133.
Inoue M Suzuki A Nohara M Kan H Edward A Kawahata H 《Environmental pollution (Barking, Essex : 1987)》2004,129(3):399-407
We present 40 year-long skeletal chronologies of tin (Sn) and copper (Cu) from an annually-banded coral (Porites sp.) collected from Pohnpei Island, Micronesia (western equatorial Pacific). Both the elements are present in antifouling marine paints and are released inadvertently into ambient seawater. Especially, Sn has often been used in the form of tributyltin (TBT). Based on a stepwise pretreatment examination, Sn and Cu both inside and outside the aragonite lattice of the coral skeleton show a potential for providing marine pollution indicators. High values of extra-skeletal Cu/Ca and Sn/Ca atomic ratios were found between late 1960s and late 1980s during a period of active use of TBT-based antifouling paints worldwide. However, a significant decrease in both the ratios in the beginning of 1990s can be attributed to regulation of the use of TBT on cargo ships by countries such as the USA, Japan and Australia. 相似文献
134.
Seasonal change of persistent organic pollutant concentrations in air at Niigata area,Japan 总被引:4,自引:0,他引:4
The concentrations of persistent organic pollutants (POPs), such as HCB, alpha-, beta-, gamma- and delta-HCH, trans- and cis-chlordane (t-CHL, c-CHL), DDE, DDD and DDT, in ambient air have been measured at five sampling points in Niigata area, Japan (Niigata, Maki, Tsubame, Jouzo and Yahiko) during the period from September 1999 to November 2001. HCB, alpha-HCH, t-CHL and c-CHL showed higher concentrations than the other chemicals in all locations. All the POPs except t-CHL and c-CHL collected at urban sites of the Niigata Plain was almost the same in their concentration levels. Higher concentrations of t-CHL and c-CHL in residential areas should be attributed to the past usage of the chemical as a termiticide. At Yahiko (remote site), most of the POPs showed lower concentrations than those measured at the other sampling sites, although alpha-HCH and gamma-HCH were comparable with the concentrations found at the other sampling sites. All POPs except alpha-HCH and gamma-HCH tend to decrease 41-80% in their concentrations from 2000 to 2001. The lower POPs concentrations in winter and the higher POPs concentrations in summer at every sampling point can be partly explained by temperature differences. Applying the equation of the logarithm of the POP partial pressure in air versus reciprocal temperature (lnPa=m/T+b) to our data, linear relations were observed. HCB gave a poor linearity and the smallest slope, while beta-HCH, t-CHL and c-CHL gave good linearities and large slopes in the equation. The results suggest that HCB level is influenced by not only the emission from terrestrial sources but the global-scale background pollution. A peculiar observation is that beta-HCH concentration measured in our study showed large temperature dependence, indicating there could be a source of contamination in the surrounding areas. 相似文献
135.
Nobuo Sugimoto Atsushi Shimizu Ichiro Matsui Itsushi Uno Kimio Arao Xuhui Dong Shuli Zhao Jun Zhou Choo-Hie Lee 《Water, Air, & Soil Pollution: Focus》2005,5(3-6):145-157
We have conducted dust observations at a number of locations including Beijing, Hefei, Suwon, Fukue, Nagasaki, Tsukuba, and
Sapporo using automated two-wavelength polarization lidars o study Asian dust phenomena, including generation, transport,
and change during transport. We developed a method using the depolarization ratio for estimating the contributions of Asian
dust and spherical air-pollution aerosols in observed aerosol mixtures. We analyzed the dust profiles statistically to derive
climatological characteristics and year-on-year variations. We also studied dust source and transport path for each dust event
using the regional chemical transport model CFORS. The statistical analysis clearly demonstrated the year-on-year variation
of dust phenomena and the characteristics depending on the locations of the observational sites. Most major dust events in
2001 and 2002 originated in Inner Mongolia and/or Mongolia at the southern edge of a low-pressure area located in Siberia
and were transported by strong westerlies. In 2003, the typical meteorological pattern for heavy dust cases accompanying a
strong low in Siberia was not seen, except for one case in April. Furthermore, the lidar observation in Beijing suggests that
less dust was generated in the source regions in Inner Mongolia and/or Mongolia, probably due to higher precipitation in 2003. 相似文献
136.
A. Yano M. Ogura A. Sato Y. Sakaki Y. Shimizu N. Baba K. Nagasawa 《Marine Biology》1997,129(3):523-530
To investigate the role of magnetic compass orientation in oceanic migrating chum salmon, Oncorhynchus keta, an ultrasonic telemetry study was carried out in the western North Pacific off the coast of Kushiro, Hokkaido. Four salmon
were fitted with a tag which generated an artificial magnetic field and modified the geomagnetic field around the head of
the fish. Initially, the free-ranging salmon with stomach-implanted ultrasonic transmitters were tracked for a period of several
hours before the magnetic field was altered for a period of 16 h. The generator produced an alternating magnetic field intensity
of about 6 gauss, with polarity which reversed every 11.25 min. There was no observable effect on the horizontal and vertical
movements of the salmon when the magnetic field was modified. However, it was noted that salmon slowed their swimming speed
significantly before changing direction, regardless of whether the fish were swimming under the normal geomagnetic field or
whether they were swimming under the modified field.
Received: 6 April 1997 / Accepted: 29 April 1997 相似文献
137.
Larvae of the marine cheilostomatid bryozoan Bugula neritina (L.) were prevented from settling for 1, 4 and 8 h by mechanical agitation, following which settlement and metamorphosis
success were examined. Settlement rates were significantly affected by swimming time, which decreased from 100% after 2 h
to 93.7 ± 4.3% after 8 h. Similarly, metamorphosis to the feeding ancestrula was significantly impaired following a swimming
time of 8 h, declining from 93.7 ± 4.3% after 1 h to 65.9 ± 7.0% after 8 h. The resultant colonies grew well for the first
3 wk, following which time, growth patterns became erratic. Growth rate was in all cases highly variable, and did not correlate
with enforced swimming times. Larval protein composition was examined after 1, 4 and 8 h swimming time, and post-larval composition
1, 2, 5, 24 and 48 h after settlement using sodium-dodecyl-sulphate polyacrylamide-gel electrophoresis (SDS-PAGE). Individual
protein content was measured using a densitometer. Larvae did not consume protein during swimming, however a protein measuring
170 kdaltons was consumed during metamorphosis. These results are discussed in the context of larval settlement and energetics.
Received: 19 July 1998 / Accepted: 3 December 1998 相似文献
138.
Interval between reproductive events is an important factor for iteroparous animals because it determines the number of clutches
throughout life. This study examined whether female size, clutch size, shell size and prenuptial molting affected the clutch
interval in the hermit crab Pagurus nigrivittatus. Precopulatory guarding pairs of P. nigrivittatus were sampled in the field and kept in the laboratory until the female extruded eggs. The clutch interval of each female was
assessed as one of two types of relatively “short” and “long” intervals by checking whether the guarded female had eggs and/or
egg cases from the preceding brood or not when the guarding pair was collected. The clutch interval was longer in females
with prenuptial molting than those without molting and these females usually grew larger at the prenuptial molt. This suggests
that female P. nigrivittatus with a long interval might allocate energy into growth at the expense of the number of clutches during the current reproductive
season. The allocation to growth is theoretically predicted to decrease with female size. Gastropod shell size is also known
to affect the reproductive activity in hermit crabs. However, female size did not significantly affect the clutch interval
in P. nigrivittatus, and the effect of gastropod shell size on clutch interval was not consistent with previous empirical studies. These results
may be caused by differences in the gastropod species of shell occupied by the females of P. nigrivittatus. 相似文献
139.
Hiroshi Shimizu Manai Tsuzuki Yasuo Yamazaki A. Koichi Hayashi 《Journal of Loss Prevention in the Process Industries》2001,14(6):603-608
The study of extinguishment using water mist has been motivated due to the phase-out of the use of halens and the search for alternative means that preserve all of the benefits of a clean total flooding agent without adverse environmental impact. With the numerical simulation, we analyzed a gas–liquid two-phase problem including water (liquid), air and methane (gas) using Eulerian equations for the liquid phase and the full Navier–Stokes equations for the gas phase. Gaseous mass, momentum and energy equations are integrated simultaneously by a Harten–Yee explicit non-MUSCL modified-flux type TVD scheme for the convective terms and a central difference scheme for the viscous terms. Liquid phase conservation equations are solved with an application of a flux-vector-splitting scheme. In the experiments in an open room (500×500×500 mm) we observed an interaction of the diffusion flame with the water mists. The results show remarkable flame quenching and a good agreement between the numerical and experimental results. 相似文献
140.