全文获取类型
收费全文 | 2128篇 |
免费 | 102篇 |
国内免费 | 523篇 |
专业分类
测绘学 | 62篇 |
大气科学 | 250篇 |
地球物理 | 1084篇 |
地质学 | 710篇 |
海洋学 | 298篇 |
天文学 | 93篇 |
综合类 | 98篇 |
自然地理 | 158篇 |
出版年
2023年 | 18篇 |
2022年 | 19篇 |
2021年 | 29篇 |
2020年 | 25篇 |
2019年 | 19篇 |
2018年 | 24篇 |
2017年 | 7篇 |
2016年 | 33篇 |
2015年 | 23篇 |
2014年 | 49篇 |
2013年 | 46篇 |
2012年 | 118篇 |
2011年 | 164篇 |
2010年 | 41篇 |
2009年 | 59篇 |
2008年 | 141篇 |
2007年 | 141篇 |
2006年 | 140篇 |
2005年 | 145篇 |
2004年 | 133篇 |
2003年 | 88篇 |
2002年 | 102篇 |
2001年 | 78篇 |
2000年 | 96篇 |
1999年 | 43篇 |
1998年 | 37篇 |
1997年 | 44篇 |
1996年 | 58篇 |
1995年 | 63篇 |
1994年 | 46篇 |
1993年 | 82篇 |
1992年 | 66篇 |
1991年 | 88篇 |
1990年 | 80篇 |
1989年 | 56篇 |
1988年 | 59篇 |
1987年 | 42篇 |
1986年 | 35篇 |
1985年 | 30篇 |
1984年 | 24篇 |
1983年 | 15篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 22篇 |
1978年 | 5篇 |
1976年 | 6篇 |
1974年 | 8篇 |
1948年 | 8篇 |
1947年 | 8篇 |
1943年 | 4篇 |
排序方式: 共有2753条查询结果,搜索用时 15 毫秒
991.
Organotin levels in Nazaré canyon (west Iberian Margin, NE Atlantic) and adjacent coastal area 总被引:1,自引:0,他引:1
Sousa AC Oliveira IB Laranjeiro F Takahashi S Tanabe S Cunha MR Barroso CM 《Marine pollution bulletin》2012,64(2):422-426
Organotin compounds (OTs) are ubiquitous in the marine environment and high concentrations (μg g(-1) range) in sediments from different coastal areas around the world have been reported. However, few reports have described the OTs contamination status in the offshore and deep sea environment. This work investigated organotin levels in Nazaré canyon for the first time. Levels of monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT), diphenyltin (DPT), triphenyltin (TPT), dioctyltin (DOT) and trioctyltin (TOT) were quantified in sediment samples from the upper flanks of the canyon and from the adjacent coastal area. TBT levels detected in the canyon flanks are about two to three orders of magnitude lower than those found in the coastal area. Nevertheless, when quantifiable, TBT levels in the canyon samples were higher than the Environmental Assessment Criteria set for TBT in sediments by the OSPAR Commission indicating that at those locations negative ecological impacts are likely to occur. 相似文献
992.
Chang WK Ryu J Yi Y Lee WC Lee CW Kang D Lee CH Hong S Nam J Khim JS 《Marine pollution bulletin》2012,64(2):427-435
The total pollution load management system (TPLMS) was first applied in 2007 to the highly developed Masan Bay watershed, Korea. To evaluate the effect of TPLMS on water quality improvement, we analyzed the water qualities in rivers and bay during 2005-2010, targeting chemical oxygen demand (COD), suspended sediment (SS), total nitrogen (TN), and total phosphorus (TP) loads. Land-based pollutant loading all decreased during this period, with a significant reduction in COD and SS loads (p<0.01). The COD reduction in seawater, following the TPLMS implementation, was also significant (p<0.01). Time-lagged responses in COD and Chl-a supported an estimated seawater residence time of ~1 month. Land-based nutrient loads were also significantly reduced for TN (p<0.01) and TP (p<0.05), however, significant reductions were not observed in the bay, indicating potential alternative nutrient inputs from non-point sources into the bay system. 相似文献
993.
Rowlands G Purkis S Riegl B Metsamaa L Bruckner A Renaud P 《Marine pollution bulletin》2012,64(6):1222-1237
We propose a framework for spatially estimating a proxy for coral reef resilience using remote sensing. Data spanning large areas of coral reef habitat were obtained using the commercial QuickBird satellite, and freely available imagery (NASA, Google Earth). Principles of coral reef ecology, field observation, and remote observations, were combined to devise mapped indices. These capture important and accessible components of coral reef resilience. Indices are divided between factors known to stress corals, and factors incorporating properties of the reef landscape that resist stress or promote coral growth. The first-basis for a remote sensed resilience index (RSRI), an estimate of expected reef resilience, is proposed. Developed for the Red Sea, the framework of our analysis is flexible and with minimal adaptation, could be extended to other reef regions. We aim to stimulate discussion as to use of remote sensing to do more than simply deliver habitat maps of coral reefs. 相似文献
994.
Patterns of bivalve larvae dispersal in the deep Ahe atoll lagoon was studied by using a numerical 3D transport model (MARS3D) coupled with a vertical swimming sub-model, forced mainly by tide and wind-induced currents. The simulations were validated against observations of larval dispersal monitored several days throughout the lagoon. Connectivity matrices describing larval exchanges inside the lagoon were inferred. Larvae displayed a significant dispersal capacity at the lagoon scale, especially with dominant eastern winds. With southeastern winds, larvae mostly remained in their origin sector. The total export rate of the larvae, toward the ocean through the pass and shallow lagoon borders, was independent of the wind conditions, with 1% of the total concentration exported per day. However, the tide-driven currents efficiently flushed larvae in sectors close to the pass. Connectivity matrices suggest that the south and west sectors were more suitable for spat collecting and that central sectors would be efficient sanctuaries if genitors were accumulated. 相似文献
995.
Real-time PCR and NASBA for rapid and sensitive detection of Vibrio cholerae in ballast water 总被引:2,自引:0,他引:2
Fykse EM Nilsen T Nielsen AD Tryland I Delacroix S Blatny JM 《Marine pollution bulletin》2012,64(2):200-206
Transport of ballast water is one major factor in the transmission of aquatic organisms, including pathogenic bacteria. The IMO-guidelines of the Convention for the Control and Management of Ships' Ballast Water and Sediments, states that ships are to discharge <1 CFU per 100 ml ballast water of toxigenic Vibrio cholerae, emphasizing the need to establish test methods. To our knowledge, there are no methods sensitive and rapid enough available for cholera surveillance of ballast water. In this study real-time PCR and NASBA methods have been evaluated to specifically detect 1 CFU/100ml of V. cholerae in ballast water. Ballast water samples spiked with V. cholerae cells were filtered and enriched in alkaline peptone water before PCR or NASBA detection. The entire method, including sample preparation and analysis was performed within 7 h, and has the potential to be used for analysis of ballast water for inspection and enforcement control. 相似文献
996.
Fabricius KE Cooper TF Humphrey C Uthicke S De'ath G Davidson J LeGrand H Thompson A Schaffelke B 《Marine pollution bulletin》2012,65(4-9):320-332
Responses of bioindicator candidates for water quality were quantified in two studies on inshore coral reefs of the Great Barrier Reef (GBR). In Study 1, 33 of the 38 investigated candidate indicators (including coral physiology, benthos composition, coral recruitment, macrobioeroder densities and FORAM index) showed significant relationships with a composite index of 13 water quality variables. These relationships were confirmed in Study 2 along four other water quality gradients (turbidity and chlorophyll). Changes in water quality led to multi-faceted shifts from phototrophic to heterotrophic benthic communities, and from diverse coral dominated communities to low-diversity communities dominated by macroalgae. Turbidity was the best predictor of biota; hence turbidity measurements remain essential to directly monitor water quality on the GBR, potentially complemented by our final calibrated 12 bioindicators. In combination, this bioindicator system may be used to assess changes in water quality, especially where direct water quality data are unavailable. 相似文献
997.
Michotey V Guasco S Boeuf D Morezzi N Durieux B Charpy L Bonin P 《Marine pollution bulletin》2012,65(10-12):525-537
Spatio-temporal variability of prokaryotic water column communities inside and outside a Polynesian tropical lagoon subjected to pearl oysters farming was assessed in terms of abundance by quantitative PCR and diversity by DGGE. Communities and operational taxonomic units (OTUs) were analysed according to dry/rainy seasons and free-living/particle-attached state. Bacterial density was higher in the lagoon compared to ocean and a seasonal trend was observed. No influence of the localisation within lagoon or of the planktonic/attached states was noticed on bacterial abundance and diversity. The OTUs belonged to Cyanobacteria, to heterotrophic groups in Proteobacteria and Flavobacteria. Archaeal abundance showed seasonal tendency and particle-prevalence, but no effect of lagoon or oceanic location was observed. Lagoon and oceanic archaeal diversity were different and Euryarchaeota (MG-II, MBG, and Halobacteria) were detected. During the dry season, planktonic and particle-associated community differed, whereas at rainy season, both communities were similar and included members usually associated with coral. 相似文献
998.
Muhling BA Roffer MA Lamkin JT Ingram GW Upton MA Gawlikowski G Muller-Karger F Habtes S Richards WJ 《Marine pollution bulletin》2012,64(4):679-687
The 2010 Deepwater Horizon oil spill impacted the northern Gulf of Mexico (GOM) during the spring spawning season of Atlantic bluefin tuna (BFT). Overlap between BFT spawning habitat and surface oil in the northern GOM was examined using satellite-derived estimates of oil coverage, and spawning habitat models. Results suggested that although eggs and larvae were likely impacted by oil-contaminated waters in the eastern GOM, high abundances of larvae were located elsewhere, especially in the western GOM. Overall, less than 10% of BFT spawning habitat was predicted to have been covered by surface oil, and less than 12% of larval BFT were predicted to have been located within contaminated waters in the northern GOM, on a weekly basis. Our results provide preliminary but important initial estimates of the effects of the spill on larval BFT mortality, as concern continues over the appropriate management responses to impacts of the spill. 相似文献
999.
Low altitude remote-sensing method to monitor marine and beach litter of various colors using a balloon equipped with a digital camera 总被引:1,自引:0,他引:1
This study aims to establish a low-altitude remote sensing system for surveying litter on a beach or the ocean using a remote-controlled digital camera suspended from a balloon filled with helium gas. The resultant images are processed to identify the litter using projective transformation method and color difference in the CIELUV color space. Low-altitude remote sensing experimental observations were conducted on two locations in Japan. Although the sizes of the litter and the areas covered are distorted in the original photographs taken at various angles and heights, the proposed image process system is capable of identifying object positions with a high degree of accuracy (1-3 m). Furthermore, the color difference approach in the CIELUV color space used in this study is well capable of extracting pixels of litter objects of various colors allowing us to estimate the number of objects from the photographs. 相似文献
1000.
Isotopic and biochemical features of suspended particulate organic matter (POM) in the water column and of sedimentary organic matter (SOM) were investigated seasonally in the Bay of Marseilles. Biochemical compounds (carbohydrates, lipids and proteins) were consistently more concentrated in POM than in SOM, with SOM mainly composed of insoluble carbohydrates. POM displayed lower δ(13)C and higher δ(15)N values than SOM. Phytoplanktonic production represented the major contributor of POM year-round with spatial and seasonal variations. Climatic parameters and wind-induced currents created differences in POM contributions, with more important inputs of terrestrial OM at one sampling site. Spatial and seasonal variations were lower for SOM. The composition of this pool appeared to be linked with the permanent inputs of phytoplankton and Posidonia oceanica detritus. The combined use of biochemical and isotopic analyses was a useful tool to characterize OM pools and would help understanding the trophic functioning of this coastal environment. 相似文献