全文获取类型
收费全文 | 1699篇 |
免费 | 333篇 |
国内免费 | 474篇 |
专业分类
测绘学 | 45篇 |
大气科学 | 144篇 |
地球物理 | 570篇 |
地质学 | 1051篇 |
海洋学 | 322篇 |
天文学 | 48篇 |
综合类 | 65篇 |
自然地理 | 261篇 |
出版年
2024年 | 5篇 |
2023年 | 25篇 |
2022年 | 58篇 |
2021年 | 57篇 |
2020年 | 65篇 |
2019年 | 99篇 |
2018年 | 76篇 |
2017年 | 65篇 |
2016年 | 75篇 |
2015年 | 91篇 |
2014年 | 126篇 |
2013年 | 137篇 |
2012年 | 90篇 |
2011年 | 125篇 |
2010年 | 98篇 |
2009年 | 129篇 |
2008年 | 118篇 |
2007年 | 115篇 |
2006年 | 129篇 |
2005年 | 105篇 |
2004年 | 86篇 |
2003年 | 70篇 |
2002年 | 80篇 |
2001年 | 71篇 |
2000年 | 48篇 |
1999年 | 55篇 |
1998年 | 46篇 |
1997年 | 39篇 |
1996年 | 39篇 |
1995年 | 37篇 |
1994年 | 39篇 |
1993年 | 21篇 |
1992年 | 16篇 |
1991年 | 11篇 |
1990年 | 13篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1954年 | 4篇 |
排序方式: 共有2506条查询结果,搜索用时 15 毫秒
141.
142.
线性石蜡基钻井液的试验研究 总被引:3,自引:0,他引:3
近期在室内研制成功了新型的第二代合成基钻井液的代表——线性石蜡基钻井液。首先从大量的试验结果中优选出了线性石蜡基钻井液配方 ,在此基础上 ,对线性石蜡基钻井液的性能进行了系统的评价。研究结果表明 ,优选出的线性石蜡基钻井液配方简单。和柴油基钻井液相比 ,线性石蜡基钻井液具有优良的热稳定性、页岩抑制性、润滑性能和储层保护性能 ,可用作深井复杂地层的钻井液 相似文献
143.
144.
A thermoelastic model for calculating the high-pressure and high-temperature properties of isotropic solids is presented
by extending the formalism by Thomsen and combining the resulting one with the Vinet model for static lattice and the Debye
model for lattice vibration. Applying it to polycrystalline corundum, we have shown that the calculated values of entropy
and heat capacity at constant pressure are in agreement with literature values to 2325 K at zero pressure and that the calculated
values of thermal expansivity agree reasonably with experimental data to 1100 K at zero pressure. The model reproduces experimental
data of sound velocities v
p
and v
s
of compressional and shear waves to 1825 K at zero pressure and those to 62 GPa at room temperature, and it reproduces also
experimental shock-wave equation of state to 150 GPa. The velocity correlation (∂ln v
s
/∂ln v
p
)
S
was found to have weak pressure and temperature dependences and the results under lower mantle conditions are compared with
those of magnesian and calcium silicate perovskites and magnesiowüstite, and the PREM values of the Earth's lower mantle.
Received: 12 February 2000 / Accepted: 15 July 2000 相似文献
145.
Synchrotron X-ray powder diffraction experiments at high pressure conditions (0.0001–13 GPa) were performed at ESRF (Grenoble-F),
on the beamline ID9, to investigate the bulk elastic properties of natural P2/n-omphacites, with quasi-ideal composition. The monoclinic cell parameters a, b, c and β were determined as a function of pressure, and their compressibility coefficients are 0.00277(7), 0.00313(8), 0.00292(5)
and 0.00116(4) GPa−1, respectively. The third-order Birch-Murnaghan equation of state was used to interpolate the experimental P−V data, obtaining K
0=116.6(±2.5) GPa and K′0=6.03(±0.60). K
0 was also determined by means of the axial and angular compressibilities [122.5(±1.7) GPa], and of the finite Lagrangian strain
theory [121.5(±1.0) GPa]. The discrepancies on K
0 are discussed in the light of a comparison between techniques to determine the bulk modulus of crystalline materials from
static compression diffraction data.
Received: 22 February 2000 / Accepted: 10 July 2000 相似文献
146.
P. M. Nikolić S. Ðurić D. M. Todorović D. Vasiljević-Radović V. Blagojević P. Mihajlović J. Elazar K. T. Radulović A. I. Bojičić D. Urošević 《Physics and Chemistry of Minerals》2001,28(1):44-51
Electron transport properties of single crystal and polycrystalline natural mineral galena (PbS) samples from the Trep?a mine, Yugoslavia, were determined using the photoacoustic frequency transmission technique. Their thermal diffusivity (D T≈0.16 × 10?5 m2 s?1), the coefficient of diffusion (D between 0.15×10?2 0.16×10?2 m2 s?1) and lifetime of the excess carrier (τ≈35 μs and the front and rear recombination velocity (s g≈65.5 m s?1 and s b≈66.4 m s?1, respectively), were calculated by comparing the experimental results and the theoretical photoacoustic amplitude and phase signals. The lattice parameter obtained by X-ray work was a?=5.936?Å. The free carrier concentration of these single-crystal samples was measured using the Hall method (N?=?3×1018 cm?3). Measurements of the optical reflectivity of the same samples, as a function of wavelength, in the infrared and far infrared ranges, were performed. In the far infrared range a free electron plasma frequency was observed and numerically analyzed, using the least-squares fitting procedure. The values of optical parameters were calculated and the value of the free carrier concentration obtained by the Hall method was confirmed. 相似文献
147.
Mushtak Talib Jabbar Faculty of Earth Resources China University of Geosciences Wuhan 《中国地质大学学报(英文版)》2001,12(2)
INTRODUCTIONLargeareasofaridandsemiaridregionsoftheworldareaf fectedbywinderosion .Approximately 2 8.4%ofthisareaareaffectedbysevereandveryseverewinderosion (Katesetal.,1977) .InIraq ,thearidandsemiaridregionsrepresentnearly 75%ofthetotalland .5 0 %ofthislandissubjec… 相似文献
148.
真实的TID一类大尺度电离层扰动是非平稳和色散的,而且是统计非单一的.本文首先给出了描述这种真实扰动场的数学模型,进而导出了联系台阵探测可测量与扰动场传播参量的观测方程,在此基础上提出了求解观测方程的时频分析方法.这一台阵探测数据分析的新方法,既能分离出非单一电离层扰动场中各种准单一扰动成分,又能获得准单一扰动成分传播参量随时间的演变和随频率的色散.分析实例表明,本文方法分辨率好,精度高,结果可靠,是适用于TID一类大尺度电离层扰动台阵探测数据分析的有效方法. 相似文献
149.
This paper deals with the electrical double layer and the related properties of porous media. In particular, the electrical conductivity, the streaming potential, and the membrane potential are described in a self-consistent set of equations. All these properties are shown to be governed by fluid-matrix interface properties, as well as four geometrical parameters. 相似文献
150.
刘晓红 《地震学报(英文版)》1996,9(2):345-349
Themanufactureofathree-dimensionaltransducerusedinlaboratoryXIAO-HONGLIU(刘晓红)(InstituteofGeophysics,StateSeismologicalBureau,... 相似文献