全文获取类型
收费全文 | 10532篇 |
免费 | 126篇 |
国内免费 | 99篇 |
专业分类
安全科学 | 310篇 |
废物处理 | 488篇 |
环保管理 | 1406篇 |
综合类 | 1274篇 |
基础理论 | 2831篇 |
环境理论 | 2篇 |
污染及防治 | 2923篇 |
评价与监测 | 751篇 |
社会与环境 | 718篇 |
灾害及防治 | 54篇 |
出版年
2022年 | 104篇 |
2021年 | 89篇 |
2020年 | 73篇 |
2019年 | 83篇 |
2018年 | 164篇 |
2017年 | 157篇 |
2016年 | 246篇 |
2015年 | 184篇 |
2014年 | 252篇 |
2013年 | 817篇 |
2012年 | 323篇 |
2011年 | 481篇 |
2010年 | 386篇 |
2009年 | 414篇 |
2008年 | 510篇 |
2007年 | 521篇 |
2006年 | 455篇 |
2005年 | 383篇 |
2004年 | 342篇 |
2003年 | 409篇 |
2002年 | 347篇 |
2001年 | 512篇 |
2000年 | 342篇 |
1999年 | 197篇 |
1998年 | 147篇 |
1997年 | 142篇 |
1996年 | 147篇 |
1995年 | 170篇 |
1994年 | 143篇 |
1993年 | 112篇 |
1992年 | 127篇 |
1991年 | 124篇 |
1990年 | 139篇 |
1989年 | 134篇 |
1988年 | 99篇 |
1987年 | 87篇 |
1986年 | 70篇 |
1985年 | 99篇 |
1984年 | 95篇 |
1983年 | 98篇 |
1982年 | 92篇 |
1981年 | 80篇 |
1980年 | 68篇 |
1979年 | 74篇 |
1978年 | 50篇 |
1977年 | 57篇 |
1976年 | 49篇 |
1975年 | 53篇 |
1974年 | 53篇 |
1973年 | 54篇 |
排序方式: 共有10000条查询结果,搜索用时 390 毫秒
991.
C. T. Achuthankutty Y. Shrivastava G. G. Mahambre S. C. Goswami M. Madhupratap 《Marine Biology》2000,137(1):19-22
Effect of salinity on the feeding rate and parthenogenetic reproduction of asexual females of the cladoceran Diaphanosoma celebensis Stingelin was studied. Short-term (10 h) grazing experiments were conducted using Isochrysis galbana as feed at 5, 17, 25 and 30 psu salinity. Gut pigment concentration showed a significantly higher rate of feeding at lower
salinities. Survival, growth, maturity attainment and neonate production of asexual females reared in the above four test
salinities indicated preference for lower salinities (5 and 17 psu). The mean size of adult females decreased from 909 to
593 μm, mean life span from 24 to 5 d, mean neonate production from 12 to 2 and mean size of neonates from 434 to 400 μm as
the salinity increased from 5 to 30 psu. Salinity variations also affected the size and age of primiparous females. Resting
egg formation and sexual reproduction did not occur at the tested salinities. The results indicate that D. celebensis is adapted to low saline, estuarine environments.
Received: 14 January 2000 / Accepted: 24 March 2000 相似文献
992.
B. Miller # R. Reading J. Hoogland † T. Clark ‡ G. Ceballos § R. List S. Forrest †† L. Hanebury ‡‡ P. Manzano § J. Pacheco § and D. Uresk§§ 《Conservation biology》2000,14(1):318-321
993.
Western sandpiper (Calidris mauri) predation was examined by concurrent experiments and direct observations of foraging behaviour on high intertidal mudflats
of the Fraser River estuary, British Columbia. Western sandpipers foraged by either “pecking” on the surface (64% of observational
time) or probing into sediment (29%). The first experiment (probe-mark method) consisted of collecting small-volume cores
(21.2 cm3) of probed (experimental) and non-probed (control) sediment on the tidal flat, following a 22.5-min feeding period. The second
experiment (exclosure method) involved deploying exclosures immediately prior to the feeding period and subsequent collection
of cores from inside (control) and outside (experimental) the exclosures. Sediment cores were analysed for both macrofaunal
and meiofaunal size fractions. Comparisons between macro- and meiofaunal invertebrate densities in experimental and control
sediments revealed significant differences, attributed to shorebird predation, for both experiments. The probe-mark experiment
detected the removal of large infaunal polychaetes (∼ 20 mm), while the exclosure experiment showed depletion of epifaunal
harpacticoid copepods (0.063–0.5 mm). Predation on macrofaunal cumaceans was detected in both experiments. Invertebrates selected
by western sandpipers neither fell within traditional infaunal size classifications (macro- vs. meiofauna; 500 μm delineation)
nor corresponded to the highest densities of taxa. Rather, inference from experimental results and observations is that western
sandpipers forage in two modes, by: (1) surface gleaning of epibenthic copepods and cumaceans in the macro- and meiofaunal
size ranges and (2) selective probing for larger infauna, such as polychaetes. These findings were facilitated by the combination
of methodologies employed.
Received: 29 December 1999 / Accepted: 11 September 2000 相似文献
994.
K. Bruce Jones Daniel T. Heggem Timothy G. Wade Anne C. Neale Donald W. Ebert Maliha S. Nash Megan H. Mehaffey Karl A. Hermann Anthony R. Selle Scott Augustine Iris A. Goodman Joel Pedersen David Bolgrien J. Max Viger Dean Chiang Cindy J. Lin Yehong Zhong Joan Baker Rick D. Van Remortel 《Environmental monitoring and assessment》2000,64(1):227-245
The Environmental Monitoring and Assessment Program (EMAP) is proposing an ambitious agenda to assess the status of streams and estuaries in a 12-State area of the western United States by the end of 2003. Additionally, EMAP is proposing to access landscape conditions as they relate to stream and estuary conditions across the west. The goal of this landscape project is to develop a landscape model that can be used to identify the relative risks of streams and estuaries to potential declines due to watershed-scale, landscape conditions across the west. To do so, requires an understanding of quantitative relationships between landscape composition and pattern metrics and parameters of stream and estuary conditions. This paper describes a strategic approach for evaluating the degree to which landscape composition and pattern influence stream and estuary condition, and the development and implementation of a spatially-distributed, landscape analysis approach. 相似文献
995.
L. Zane L. Ostellari L. Maccatrozzo L. Bargelloni J. Cuzin-Roudy F. Buchholz T. Patarnello 《Marine Biology》2000,136(2):191-199
Meganyctiphanes norvegica (M. Sars)is a pelagic crustacean that plays a key role in marine food webs of North Atlantic Ocean and marginal seas. We
studied eight population samples collected in the European Atlantic and Mediterranean Sea. By means of single strand conformation
polymorphism analysis (SSCP) and direct sequencing, we investigated a segment of 158 base pairs of the mitochondrial gene
coding for the subunit 1 of NADH dehydrogenase. We found 12 sequence variants among the 385 individuals studied. Analysis
of molecular variance (AMOVA) showed that 14.75% of the total genetic variability was explained by differences between populations,
thus indicating absence of panmixia for these populations. Pairwise comparisons revealed three distinct genetic pools: the
first one represented by Cadiz Bay, the second one by the Ligurian Sea, and the third one included all the NE Atlantic samples.
We also investigated one population from the Alboran Sea (within the Mediterranean basin, east of the Strait of Gibraltar).
This population was found to be genetically intermediate between the NE Atlantic samples and the Ligurian sample, suggesting
that the restriction to the gene flow is not associated with the Strait of Gibraltar, but possibly with the Oran–Almeria oceanographic
front. The present work indicates that M. norvegica, although endowed with a high dispersal capacity because of its pelagic habit, can develop separate breeding units inside
the same oceanic basin (the Atlantic). Furthermore, the Ligurian sample should be considered as a distinct evolutionary entity,
separated from the Atlantic population.
Received: 2 May 1999 / Accepted: 26 November 1999 相似文献
996.
This research used a justice perspective to investigate the effects of outcome favorability, opportunity for voice, and interpersonal treatment in a service context. Results suggest that all three variables influenced customer reactions to bank loan decisions. Weak‐tie customers were more sensitive to outcome favorability than strong‐tie customers. Strong‐tie customers were more sensitive to opportunity for voice than weak‐tie customers. Implications for improving customer reactions to service transactions are discussed. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
997.
The influence of wave exposure and of tidal height on mussel (Perna perna Linnaeus) population structure (size, density, biomass and adult/juvenile correlations) was examined at 18 sites along the
south coast of South Africa. Sites were classified as exposed or sheltered prior to sampling, without reference to the biota,
on the basis of aspect, topography and wave regime. A single set of samples was collected from each site during three spring
tide cycles. Adult mussels on these shores almost always attach directly to the rocks, and layering of mussels is virtually
absent. Shore height always had a strong influence on population structure, but exposure had significant effects only lower
on the shore, and almost exclusively on mussel sizes. Principal component analysis (PCA), based on size distribution data
for each population, revealed a general upshore decrease in the modal size of the adult cohort. The effects of exposure on
size distribution, however, varied with tidal height. PCA separated exposed zones, with larger mussels, from sheltered zones
on the low-shore. Farther upshore the two shore types were increasingly confounded. The maximum size of mussels showed a similar
pattern, with significant differences (ANOVA, p < 0.05) between exposed and sheltered sites only on the low- and mid-shores. Density was calculated from randomly placed
quadrats (i.e. not necessarily from areas of 100% cover) and showed a different pattern. Adult (>15 mm) densities decreased
up the shore, with low-, mid- and high-shore zones being significantly different from one another (ANOVA, p < 0.0001; followed by multiple range tests). However, exposure had no significant effect on density, nor was there a significant
interaction with zone. Recruit (<15 mm) densities were positively correlated with adult (>15 mm) densities in all zones and
for both exposure regimes ( p < 0.05 in all cases), but there was considerable variability and extremely low predictability in these relationships (r
2 generally <0.2). Predictability tended to be greater towards the high-shore, where adults were more clumped. As with density,
biomass was not affected by exposure, but decreased upshore as mean size and density decreased. A reduction in the influence
of exposure farther upshore may be caused by greater emersion overriding the effects of exposure. The presence of free space
within mussel beds and significant correlations between recruit and adult densities suggest that these mussel populations
are recruit limited.
Received: 7 January 2000 / Accepted: 6 July 2000 相似文献
998.
T. Lubjuhn Wolfgang Winkel Jörg Thomas Epplen Jörg Brün 《Behavioral ecology and sociobiology》2000,48(1):12-17
One of the most interesting aspects of the mating system of pied flycatchers is the regular occurrence of polygyny. Here we
present data on the reproductive success of polygynously paired pied flycatcher males compared to monogamous males based on
paternity analyses through DNA fingerprinting. Males paired with two females suffered a higher loss in reproductive output
per female compared to monogamous males due to (1) a greater proportion of unhatched eggs in their broods, (2) greater nestling
mortality and (3) a greater probability of being cuckolded. Nevertheless, the number of fledglings was significantly greater
for polygynous males. Based on the number of nestlings that returned for subsequent breeding seasons, however, the reproductive
success of monogamous and polygynous males did not differ significantly. These data raise the question as to why males attempt
polygyny.
Received: 16 August 1999 / Received in revised form: 15 March 2000 / Accepted: 18 March 2000 相似文献
999.
Early development of the Antarctic sea urchin Sterechinus neumayeri was examined under two differ-ent culture regimes: one to simulate development near-bottom (“demersal development”) and the
other to simulate the development of embryos in the water column (“pelagic development”). When embryos of both treatments
reached the hatching blastula stage at 5 d post-fertilization (−1.5 °C), the blastulae that had undergone demersal development
evidenced significant differences (by ANOVA or suitable non-parametric comparison) in the following: a thicker blastoderm
layer (12%, P < 0.001), higher ash-free dry weights (19%, P < 0.01), lower mass-specific respiration rates (50%, P < 0.001), higher incorporation rates of 35S-methionine into protein (23%, P < 0.003), and a differential pattern of protein synthesis. When embryos developed demersally, they remained in the jelly-coat
material released with the eggs at spawning. Quantitative isolation of this jelly-coat material in S. neumayeri demonstrated that it contained a significant amount of organic matter, 115 ng ash-free dry mass per egg, equivalent to 17%
of the egg's initial organic mass. Uptake of external nutrients during embryogenesis may be a significant component of the
physiological energetics of this polar invertebrate by allowing the utilization of jelly-coat material released by a female
during spawning.
Received: 21 April 1999 / Accepted: 5 June 2000 相似文献
1000.
H. T. Schreuder R. Czaplewski R. G. Bailey 《Environmental monitoring and assessment》1999,56(3):269-291
A forest ecological inventory and monitoring system combining information derived from maps and samples is proposed based on ecosystem regions (Bailey, 1994). The system extends the design of the USDA Forest Service Region 6 Inventory and Monitoring System (R6IMS) in the Pacific Northwest of the United States. The key uses of the information are briefly discussed and expected results are illustrated with examples. The system is flexible, allowing regions based on ecological considerations to be modified. Sampling intensities that are affordable are likely to be insufficient to provide meaningful estimates for key parameters relating to rare and endangered species, watersheds, and other ecological units. Methods are proposed for collecting additional information in follow-up surveys and combining it with relevant information obtained in R6IMS. Near-continuous information on weather and possible pollution variables recorded by instruments at sampling sites is needed to develop meaningful models to understand what is happening in the ecoregions. R6IMS and the proposed additions constitute a dynamic system which will be modified further as data are analyzed. 相似文献