首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2251篇
  免费   20篇
  国内免费   8篇
安全科学   57篇
废物处理   155篇
环保管理   156篇
综合类   260篇
基础理论   483篇
环境理论   1篇
污染及防治   781篇
评价与监测   222篇
社会与环境   161篇
灾害及防治   3篇
  2023年   24篇
  2022年   58篇
  2021年   64篇
  2020年   30篇
  2019年   37篇
  2018年   65篇
  2017年   77篇
  2016年   115篇
  2015年   68篇
  2014年   120篇
  2013年   223篇
  2012年   137篇
  2011年   174篇
  2010年   97篇
  2009年   70篇
  2008年   155篇
  2007年   154篇
  2006年   113篇
  2005年   89篇
  2004年   60篇
  2003年   50篇
  2002年   62篇
  2001年   36篇
  2000年   20篇
  1999年   18篇
  1998年   7篇
  1997年   8篇
  1996年   6篇
  1995年   14篇
  1994年   8篇
  1993年   12篇
  1992年   3篇
  1991年   7篇
  1990年   10篇
  1989年   3篇
  1988年   6篇
  1983年   3篇
  1975年   2篇
  1967年   4篇
  1966年   2篇
  1964年   8篇
  1963年   7篇
  1962年   7篇
  1960年   5篇
  1959年   2篇
  1958年   8篇
  1957年   3篇
  1956年   4篇
  1955年   2篇
  1943年   2篇
排序方式: 共有2279条查询结果,搜索用时 31 毫秒
311.
Cadmium contents of cultivated soils exposed to contamination in Poland   总被引:2,自引:0,他引:2  
Cadmium was measured in soils limed with industrial solid wastes, in cultivated lands located near waste yards and in soils of allotment gardens exposed to contamination. The median level and range of cadmium in soils of varying exposure to contamination was respectively: 0.3 mg kg–1 and 0.01–107 mg kg–1, 0.2 mg kg–1 and 0.02–2,198 mg kg–1, 0.4 mg kg–1 and 0.05–161 mg kg 1. Cadmium levels exceeded the value of 3 mg kg–1 considered permissible for arable soils in the samples of soils limed with wastes from the chemical industry (2.4%), the mining industry and metallurgy sites (2.1 %), in 12.4% samples of soils located in the neighbourhood of industrial waste storage yards and in 17.2% samples of soils from allotment gardens located on lands formerly used for waste storage.  相似文献   
312.
Population genetic structure of the thorny skate (Amblyraja radiata) was surveyed in >300 individuals sampled from Newfoundland, Iceland, Norway, the Kattegat and the central North Sea. A 290-bp fragment of the mt cytochrome-b gene was first screened by SSCP. Sequences of SSCP haplotypes revealed 34 haplotypes, 14 of which were unique to Iceland, 3 to Newfoundland, 1 to Norway and 3 to the Kattegat. The global F ST was weak but significant. Removal of the two Kattegat locations, which were the most differentiated, resulted in no significant genetic differentiation. Haplotype diversity was high and evenly distributed across the entire Atlantic (h = 0.8) with the exception of the North Sea (h = 0.48). Statistical parsimony revealed a star-like genealogy with a central widespread haplotype. A subsequent nested clade analysis led to the inference of contiguous expansion with evidence for long distance dispersal between Newfoundland and Iceland. Historical demographic analysis showed that thorny skates have undergone exponential population expansion that started between 1.1 million and 690,000 years ago; and that the Last Glacial Maximum apparently had little effect. These results strongly differ from those of a parallel study of the thornback ray (Raja clavata) in which clear structure and former refugial areas could be identified. Although both species have similar life history traits and overlapping ranges, the continental shelf edge apparently does not present a barrier to migration in A. radiata, as it does for R. clavata.  相似文献   
313.
Summary. We report field and laboratory evidence indicating that the defensive compounds secreted by the millipedes Amplinus bitumidus (Diplopoda: Polydesmida) and Anadenobolus putealis (Diplopoda: Spirobolida) attract the carrion scarab Canthon morsei (Scarabaeidae: Scarabaeinae). In a Mexican tropical rain forest, C. morsei was mostly caught in pitfall traps baited with the carcasses of both millipede species. Only a few beetles were attracted to fish carrion. Experimental evidence indicates that C. morsei is attracted to freshly dead millipedes. Benzaldehyde and HCN were identified from Amplinus bitumidus; but 2-methyl-1,4-benzoquinone (toluquinone) and 2-methoxy- 3-methyl-1,4-benzoquinone from Anadenobolus putealis. Benzaldehyde attracted significantly more C. morsei individuals than fish meat, or millipedes of both species did after rinsing in hexane. This is the first report of Polydesmida attracting dung beetles.  相似文献   
314.
Egg production and hatching success of the copepod Temora longicornis were measured in laboratory experiments and in the field (North Sea). In the laboratory, ingestion of four algal species (Thalassiosira weissflogii, Phaeocystis globosa, Isochrysis sp. and Dunaliella tertiolecta) was followed and the content of fatty acids in the algae was determined. The two food types (T. weissflogii and Isochrysis sp.) that provided the highest ingestion of carbon and long chain fatty acids also resulted in the highest egg production rate (Er) and hatching success (H%). In contrast, D. tertiolecta led to both low ingestion of carbon and long chain fatty acids, resulting in low reproductive success. There was a positive relationship between the amount of eicosapentaenoic fatty acid [20:5(n-3), EPA] ingested and Er and H%, and of the ratio between docosahexaenoic and eicosapentaenoic fatty acid [22:6(n-3)/20:5(n-3), DHA/EPA] in the ingested food and H%. In the field, chlorophyll a and specific fatty acids were measured and protists were enumerated, in order to investigate the link between these factors and the reproductive success of T. longicornis. Hatching time was found to be related to temperature and exceeded 120 h at 6°C. No relationship was found between chlorophyll a and reproductive success (Er or H%). Er correlated with the concentration of diatoms and ciliates, which were the dominating protists in early spring, indicating that food quantity was the limiting factor for Er. As in the laboratory experiments, H% was dependent on the fatty acid DHA and the ratio of DHA/EPA, which indicates that the quality of eggs (H%) is linked to the quality of food.Communicated by M. Kühl, Helsingør  相似文献   
315.
One of the limitations of the biodegradation of hydrophobic chemical compounds, like lignins, is their low solubility in the aqueous solution where this process takes place. To resolve this problem, surfactants have been used to improve the solubility of these hydrophobic compounds. In this investigation, we studied the effect of surfactants (anionic, cationic, and non-ionic) on the treatment of Kraft black liquor with Fenton's reagent. In the Fenton reaction, H2O2 (two different concentrations, 10 mM and 20 mM), FeCl2 (1 mM) and surfactant solution (10%) were used. Black liquor degradation was determined by UV/Visible spectrophotometry and by measuring phenolic groups. In the presence of Fenton's reagent, the optimum conditions for the oxidative degradation of black liquor were 10 mM H2O2, 1 microL of 10% solution of anionic surfactant (SDS). The importance of the use of surfactants for preparing black liquor for subsequent Fenton's reagent-mediated degradation was discussed.  相似文献   
316.
Elie Gaget  Diego Pavón-Jordán  Alison Johnston  Aleksi Lehikoinen  Wesley M. Hochachka  Brett K. Sandercock  Alaaeldin Soultan  Hichem Azafzaf  Nadjiba Bendjedda  Taulant Bino  Luka Božič  Preben Clausen  Mohamed Dakki  Koen Devos  Cristi Domsa  Vitor Encarnação  Kiraz Erciyas-Yavuz  Sándor Faragó  Teresa Frost  Clemence Gaudard  Lívia Gosztonyi  Fredrik Haas  Menno Hornman  Tom Langendoen  Christina Ieronymidou  Vasiliy A. Kostyushin  Lesley J. Lewis  Svein-Håkon Lorentsen  Leho Luigujõe  Włodzimierz Meissner  Tibor Mikuska  Blas Molina  Zuzana Musilová  Viktor Natykanets  Jean-Yves Paquet  Nicky Petkov  Danae Portolou  Jozef Ridzoň  Samir Sayoud  Marko Šćiban  Laimonas Sniauksta  Antra Stīpniece  Nicolas Strebel  Norbert Teufelbauer  Goran Topić  Danka Uzunova  Andrej Vizi  Johannes Wahl  Marco Zenatello  Jon E. Brommer 《Conservation biology》2021,35(3):834-845
Climate warming is driving changes in species distributions and community composition. Many species have a so-called climatic debt, that is, shifts in range lag behind shifts in temperature isoclines. Inside protected areas (PAs), community changes in response to climate warming can be facilitated by greater colonization rates by warm-dwelling species, but also mitigated by lowering extirpation rates of cold-dwelling species. An evaluation of the relative importance of colonization-extirpation processes is important to inform conservation strategies that aim for both climate debt reduction and species conservation. We assessed the colonization-extirpation dynamics involved in community changes in response to climate inside and outside PAs. To do so, we used 25 years of occurrence data of nonbreeding waterbirds in the western Palearctic (97 species, 7071 sites, 39 countries, 1993–2017). We used a community temperature index (CTI) framework based on species thermal affinities to investigate species turnover induced by temperature increase. We determined whether thermal community adjustment was associated with colonization by warm-dwelling species or extirpation of cold-dwelling species by modeling change in standard deviation of the CTI (CTISD). Using linear mixed-effects models, we investigated whether communities in PAs had lower climatic debt and different patterns of community change than communities outside PAs. For CTI and CTISD combined, communities inside PAs had more species, higher colonization, lower extirpation, and lower climatic debt (16%) than communities outside PAs. Thus, our results suggest that PAs facilitate 2 independent processes that shape community dynamics and maintain biodiversity. The community adjustment was, however, not sufficiently fast to keep pace with the large temperature increases in the central and northeastern western Palearctic. Our results underline the potential of combining CTI and CTISD metrics to improve understanding of the colonization-extirpation patterns driven by climate warming.  相似文献   
317.
The increase of intensive bovine production systems in Argentina involves the use of therapeutic agents and growth promoters that reach the environment through animal excreta. The growth promoter most widely used in Argentina is monensin, an ionophore polyether antibiotic produced by Streptomyces cinnamoniensis. Here, the behavior of monensin in different solid environmental matrices is analyzed, and preliminary results that suggest a strong dependence of monensin retention with the organic matter content of the matrix are discussed.  相似文献   
318.
To investigate copepod nauplii ingestion rates on phytoplankton, we have adapted the traditional gut fluorescence technique as it can be used with lower gut pigment concentrations. With the improved technique, laboratory experiments were performed to estimate functional responses for nauplii of Calanus helgolandicus and Centropages typicus. Nauplii were raised from eggs to copepodites and the experiments were performed with stages NIV-NV. Gut evacuation rates and ingestion rates were measured on Isochrysis galbana at different concentrations. Specific ingestion rates ranged between 0.038–0.244 μg C μg−1 nauplii C d−1 for C. typicus and 0.041–1.412 μg C μg−1 nauplii C d−1 for C. helgolandicus. Both species showed a type III functional response, reaching a saturation concentration at around 600 μgC l−1 for C. typicus and 800 μgC l−1 for C. helgolandicus. An erratum to this article can be found at  相似文献   
319.
Allograft reactions of the sponge Hymeniacidon heliophila Parker, 1910 have been studied and quantified at the cellular level in vitro. Cell-layer assays were used to record the timing of rejection between allogeneic individuals and to investigate changes in the cellular subpopulations of primmorphs belonging to different individuals and placed in direct contact. The initial contact on both cell layers and primmorphs was followed by partial fusion and ended by their isolation with formation of a defined barrier but without marked collagen deposition. Using cytospins, cellular subpopulations from primmorphs were morphologically distinguished based on overall shape and on nuclear and cytoplasmic characteristics. In the beginning of the cultures up to 17 cell types could be recognized. Within 5 days, following reaggregation and primmorph formation, populations of eight of these types suffered marked reduction, whereas nine other cell types were either maintained or reduced at a slower pace. When submitted to allogeneic contact, the cellular dynamics of the four remaining types were altered. Surprisingly, the percentage of archeocytes is reduced, probably depleted by differentiation into other, differentiated cell populations. Cellular responses to allogeneic contact were characterized mainly by a transient increase in globoferous cells, a larger participation of presumed collagen-secreting cells, and by a remarkable expansion of the collencyte population. The collencyte population remained altered after the isolation of the individuals by a collagen barrier, and this can represent a mechanism of short-term immune memory.Communicated by O. Kinne, Oldendorf/Luhe  相似文献   
320.
We examined the preference of Atlantic molly females (Poecilia mexicana) to associate with a well-fed or a starved male in simultaneous choice tests. Females from three different populations were tested in three treatments: (1) the females could choose on the basis of multiple cues from the males (visual plus non-visual); (2) only non-visual cues could be perceived in darkness, (3) only visual cues were presented. The three tested populations differ clearly in their ecology: one population occurs in a typical river habitat, the second one in a milky sulfur creek outside a cave, and the third population occurs in a cave habitat (cave molly). In the river-dwelling population, females never showed a preference. In the population from the sulfur creek, females preferred to associate with the well-nourished male when visual cues from the males were available. Only cave molly females exhibited a strong preference for well-nourished males in all treatments. A morphological comparison demonstrated that wild-caught males from river habitats are typically in a good nutritional state. In the sulfur creek, males showed signs of starvation. Cave molly males were in an even worse nutritional state. In the cave population, saturated males probably indicate high fitness, thereby driving the evolution of the preference for good male nutritional state.Communicated by K. Lindström  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号