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   147篇
  免费   9篇
测绘学   6篇
大气科学   10篇
地球物理   45篇
地质学   73篇
海洋学   7篇
天文学   4篇
综合类   2篇
自然地理   9篇
  2023年   1篇
  2021年   4篇
  2020年   2篇
  2019年   3篇
  2018年   14篇
  2017年   6篇
  2016年   12篇
  2015年   8篇
  2014年   9篇
  2013年   8篇
  2012年   6篇
  2011年   9篇
  2010年   7篇
  2009年   11篇
  2008年   14篇
  2007年   10篇
  2006年   5篇
  2005年   3篇
  2004年   3篇
  2003年   6篇
  2002年   4篇
  2001年   2篇
  2000年   3篇
  1999年   1篇
  1998年   1篇
  1995年   3篇
  1983年   1篇
排序方式: 共有156条查询结果,搜索用时 421 毫秒
121.
 Curuksu is a low temperature hydrothermal system located within the upper sector of the B. Menderes Graben. The hydrologic structure of the Curuksu hydrothermal system is largely controlled by major graben faults where it is characterized by the presence of two thermal reservoirs. One is formed by Paleozoic quartzite, schist and marble units, and the second consists of Pliocene limestone-travertine units. The thermal conditions in the Curuksu region indicate that the regional tectonics and resulting local stress field control low temperatures activity. Temperatures of 30 springs emerging in the study area range between 15 and 55  °C. These springs are classified as cold fresh, warm mineral and thermal waters. Pamukkale, Karahayıt and Honaz springs are steam condensate waters, whereas Curuksu springs are commonly steam-heated waters with respect to the major anion concentrations. The reservoir temperatures have been estimated from chemical compositions by utilizing simultaneously, geothermometers and mixing models. According to these thermometric methods, the most probable subsurface temperature is in the range of 62–90  °C. However, the mixing models suggest a temperature level of 80  °C for the parent water. The system has low total dissolved solid (TDS) of ∼1000–1500 mg/l, which indicate that these waters undergo conductive cooling within the reservoir. Received: 9 September 1999 · Accepted: 14 February 2000  相似文献   
122.
We use teleseismic three-component digital data from the Trabzon, Turkey broadband seismic station TBZ to model the crustal structure by the receiver function method. The station is located at a structural transition from continental northeastern Anatolia to the oceanic Black Sea basin. Rocks in the region are of volcanic origin covered by young sediments. By forward modelling the radial receiver functions, we construct 1-D crustal shear velocity models that include a lower crustal low-velocity zone, indicating a partial melt mechanism which may be the source of surfacing magmatic rocks and regional volcanism. Within the top 5 km, velocities increase sharply from about 1.5 to 3.5 km s−1. Such near-surface low velocities are caused by sedimentation, extending from the Black Sea basin. Velocities at around 20 km depth have mantle-like values (about 4.25 km s−1 ), which easily correlate to magmatic rocks cropping out on the surface. At 25 km depth there is a thin low-velocity layer of about 4.0 km s−1. The average Moho velocity is about 4.6 km s−1, and its depth changes from 32 to 40 km. Arrivals on the tangential components indicate that the Moho discontinuity dips approximately southwards, in agreement with the crustal thickening to the south. We searched for the solution of receiver functions around the regional surface wave group velocity inversion results, which helped alleviate the multiple solution problem frequently encountered in receiver function modelling.
Station TBZ is a recently deployed broadband seismic station, and the aim of this study is to report on the analysis of new receiver function data. The analysis of new data in such a structurally complex region provides constraining starting models for future structural studies in the region.  相似文献   
123.
We have explored 1D S-wave velocity profiles of shallow and deep soil layers over a basement at strong motion stations in Eskisehir Province, Turkey. Microtremor array explorations were conducted at eight strong motion stations in the area to know shallow 1D S-wave velocity models. Rayleigh wave phase velocity at a frequency range from 3 to 30 Hz was estimated with the spatial autocorrelation analysis of array records of vertical microtremors at each station. Individual phase velocity was inverted to a shallow S-wave velocity profile. Low-velocity layers were identified at the stations in the basin. Site amplification factors from S-wave parts of earthquake records that had been estimated at the strong motion stations by Yamanaka et al. (2017) were inverted to the S-wave velocities and Q-values of the sedimentary layers. The depths to the basement with an S-wave velocity of 2.2 km/s are about 1 km in the central part of the basin, while the basement becomes shallow as 0.3 km in the marginal part of the basin. We finally discussed the effects of the shallow and deep sedimentary layers on the 1D S-wave amplification characteristics using the revealed profiles. It is found that the shallow soil layers have no significant effects in the amplification at a frequency range lower than 3 Hz in the area.  相似文献   
124.
In this study, a new sorbent is synthesized using surface imprinting technique. Cu(II)‐imprinted multiwalled carbon nanotube sorbent (Cu(II)‐IMWCNT) is used as the solid phase in the solid‐phase extraction method. After the preconcentration procedure, Cu(II) ions are determined by high‐resolution continuum source atomic absorption spectrometry. A total of 0.1 mol L?1 ethylenediaminetetraacetic acid (EDTA) is used to remove Cu(II) ions from the sorbent surface. The optimum experimental conditions for effective preconcentration of Cu(II), parameters such as pH, eluent type and concentration, flow rate, sample volume, sorbent capacity, and selectivity are investigated. The synthesized solid phase is characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The maximum adsorption capacities of Cu(II)‐IMWCNT and non‐imprinted solid phases are 270.3 and 14.3 mg g?1 at pH 5, respectively. Under optimum experimental conditions for Cu(II) ions, the limit of detection is 0.07 μg L?1 and preconcentration factor is 40. In addition, it is determined to be reusable without significant decrease in recovery values up to 100 adsorption–desorption cycles. Cu(II)‐IMWCNT have a high stability. To check the accuracy of the developed method, certified reference materials, and water samples are analyzed with satisfactory analytical results.  相似文献   
125.
In this study, pre-seismic and post-seismic total electron content (TEC) anomalies of 63 Mw?≥?5.0 earthquakes in Turkey (36°–42°N, 26°–45°E) were statistically investigated. The largest earthquake that occurred in Turkey during 2003–2016 is the Mw 7.1 Van earthquake on October 23, 2011. The TEC data of epicenters is obtained from CODE-GIM using a simple 4-point bivariate interpolation. The anomalies of TEC variations were determined by using a quartile-based running median process. In order to validate GIM results, we used the GPS-TEC data of available four IGS stations within the size of the Van earthquake preparation area. The anomalies that are detected by GIM and GPS-TEC show a similar pattern. Accordingly, the results obtained with CODE-GIM are reliable. The statistical results show that there are not prominent earthquake precursors for Mw?≤?6.0 earthquakes in Turkey.  相似文献   
126.
127.
In this study, closed form equations as functions of the isolator, bridge and ground motion properties are formulated to calculate the optimum characteristic strength, Qd and post-elastic stiffness, kd, of the isolator to minimize the maximum isolator displacement (MID) and force (MIF) for seismic isolated bridges (SIBs). For this purpose, first, sensitivity analyses are conducted to identify the bridge, isolator and ground motion parameters that affect the optimum values of Qd and kd. Next, for the identified parameters, nonlinear time history analyses of typical SIBs are conducted to determine the optimum values of Qd and kd for a wide range of values of the parameters. Next, nonlinear regression analyses of the available data are conducted to obtain closed form equations for the optimum values of Qd and kd, to minimize the MID and MIF. The equations are then simplified for various site soil conditions. It is observed that the optimum Qd and kd are highly dependent on the site soil condition. Furthermore, the optimum Qd is found to be a linear function of the peak ground acceleration.  相似文献   
128.
The aim of this paper was to investigate a novel method of polyelectrolyte injection into deep bed filter media. The raw water and the filter media used in the pilot filters were obtained from the Omerli Reservoir that supplies one million m3/day of water to the greater city of Istanbul. A cationic polyelectrolyte was injected at the entrance of the filter and at different depths of the sand bed. The effect of polyelectrolyte injection location and method was evaluated by measuring the effluent turbidity, effluent particle count, and the head losses at different locations of the sand media. It was observed that the simultaneous injection of the polyelectrolyte on top of the filter bed and at the center can lengthen the filter run time while achieving an effluent turbidity as low as 0.06 NTU (nephelometric turbidity unit) and 4 log (99.99%) particle removal.  相似文献   
129.
The study investigated the particle size distribution of major organic pollutants in black water and gray water fractions of domestic sewage. Particle size distribution was assessed by means of a filtration/ultrafiltration sequence together with laser diffraction. Emphasis was placed upon the correlation between the size distribution of chemical oxygen demand (COD) and its biodegradation characteristics obtained by respirometric analysis. Particle size distribution analysis provided specific fingerprints for COD, total organic carbon (TOC), carbohydrates, proteins, and color for black water and gray water: Aside from significant difference between COD contents, the more concentrated COD was predominantly in particulate form in black water, whereas soluble COD accounted for nearly 60% of the total in gray water. TOC and carbohydrate exhibited a similar pattern. Size distribution of particulate matter yielded different characteristics for the two fractions and indicated that settleable matter should be considered as a significant portion in assessing biodegradation. Particle size distribution of COD, although not directly related, gave an accurate image of biodegradation, indicating that particle size was basically the main parameter for differentiating and predicting major COD fractions with different biodegradation characteristics. It explained the dual hydrolysis mechanism associated with the black water based on the existence of a significant settleable COD fraction.  相似文献   
130.
This study aims to carry out a seismic risk assessment for a typical mid-size city based on building inventory from a field study. Contributions were made to existing loss estimation methods for buildings. In particular, a procedure was introduced to estimate the seismic quality of buildings using a scoring scheme for the effective parameters in seismic behavior. Denizli, a typical mid-size city in Turkey, was used as a case study. The building inventory was conducted by trained observers in a selected region of Denizli that had the potential to be damaged from expected future earthquakes according to geological and geotechnical studies. Parameters that are known to have some effect on the seismic performance of the buildings during past earthquakes were collected during the inventory studies. The inventory includes data of about 3,466 buildings on 4,226 parcels. The evaluation of inventory data provided information about the distribution of building stock according to structural system, construction year, and vertical and plan irregularities. The inventory data and the proposed procedure were used to assess the building damage, and to determine casualty and shelter needs during the M6.3 and 7.0 scenario earthquakes, representing the most probable and maximum earthquakes in Denizli, respectively. The damage assessment and loss studies showed that significant casualties and economic losses can be expected in future earthquakes. Seismic risk assessment of reinforced concrete buildings also revealed the priorities among building groups. The vulnerability in decreasing order is: (1) buildings with 6 or more stories, (2) pre-1975 constructed buildings, and (3) buildings with 3–5 stories. The future studies for evaluating and reducing seismic risk for buildings should follow this priority order. All data of inventory, damage, and loss estimates were assembled in a Geographical Information System (GIS) database.  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