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91.
高围压下冻土强度弱化的机理分析 总被引:7,自引:5,他引:2
围压作用下,影响冻结砂土强度弱化的主要原因是孔隙冰的压融,矿物颗粒细化的微裂隙的发育。影响冻结粉质粘土强度弱化的主要原因是孔隙冰的压融和微裂隙的发育,这些过程是不独立存在的,而是共同影响,共同作用,从而导致了冻土强度的弱化。 相似文献
92.
Transport of water in frozen soil IV. Analysis of experimental results on the effects of ice content
Effects of ice content on the transport of water in frozen soil are studied experimentally and theoretically under isothermal conditions. A physical law, that the flux of water in unsaturated frozen soil is proportional to the gradient of total water content is proposed. Theoretical justification is made by the use of the two-phase flow theory. The experimental results are shown to support the proposed physical law. The results of this study are presented in two parts and this is the second paper describing the theoretical aspects of the study. 相似文献
93.
Development and testing of a serially multiplexed fiber optic sensor system is described. The sensor differs from conventional
fiber optic acoustic systems, as it is capable of sensing AE emissions at several points along the length of a single fiber.
Multiplexing provides for single channel detection of cracks and their locations in large structural systems. An algorithm
was developed for signal recognition and tagging of the AE waveforms for detection of crack locations. Laboratory experiments
on plain concrete beams and post-tensioned FRP tendons were performed to evaluate the crack detection capability of the sensor
system. The acoustic emission sensor was able to detect initiation, growth and location of the cracks in concrete as well
as in the FRP tendons. The AE system is potentially suitable for applications involving health monitoring of structures following
an earthquake
Supported by: National Science Foundation, Grant number CMS-9900338 相似文献
94.
2004年3月至2005年7月对古尔班通古特沙漠南部典型半固定沙垄土壤水分进行了系统监测,结合气象资料,特别是对冬季积雪和冻土资料的分析,认为该沙漠沙丘土壤水分时空变化规律在很大程度上受积雪融化和季节性冻土的影响.由于冬季稳定存在20~30 cm的积雪于春季融化,使得春季沙丘土壤含水率成为全年最高的季节,从而为早春植物的萌发生长创造了有利的条件.冬季1 m多深的冻土于早春时节由表及里开始消融,沙丘表面融化的雪水在坡面重力作用下,沿难以透水的冻土层上界自坡上向坡下发生迁移,在春夏季形成了垄间最高、坡部次之和垄顶最少的土壤水分空间格局.该研究具有生态学意义,可为古尔班通古特沙漠特殊环境条件下植被恢复与重建提供依据. 相似文献
95.
房产测量中面积测算问题探讨 总被引:3,自引:0,他引:3
房产测量成果是为产权产籍管理、开发管理、交易管理和拆迁管理服务,是为城市规划和城市建设等提供基础数据和资料的重要基础性工作,得到全社会的关注。本文对房产测量中房屋面积测算过程经常遇到的问题进行了探讨,并提出了一些解决的建议。 相似文献
96.
Apparent fracture toughness in Mode I of microcracking materials such as rocks under confining pressure is analyzed based
on a cohesive crack model. In rocks, the apparent fracture toughness for crack propagation varies with the confining pressure.
This study provides analytical solutions for the apparent fracture toughness using a cohesive crack model, which is a model
for the fracture process zone. The problem analyzed in this study is a fluid-driven fracture of a two-dimensional crack with
a cohesive zone under confining pressure. The size of the cohesive zone is assumed to be negligibly small in comparison to
the crack length. The analyses are performed for two types of cohesive stress distribution, namely the constant cohesive stress
(Dugdale model) and the linearly decreasing cohesive stress. Furthermore, the problem for a more general cohesive stress distribution
is analyzed based on the fracture energy concept. The analytical solutions are confirmed by comparing them with the results
of numerical computations performed using the body force method. The analytical solution suggests a substantial increase in
the apparent fracture toughness due to increased confining pressures, even if the size of the fracture process zone is small. 相似文献
97.
K. B. Broberg 《Pure and Applied Geophysics》2006,163(9):1867-1879
Although mode I and mode II crack propagation show many similarities, in particular when analysed by linear elastic fracture
mechanics, they differ significantly in the micro-structural behaviour. These differences, which are clearly noticeable in
the fracture surface morphology, lead to fundamental differences in the macroscopic behaviour. Thus, mode II crack expansion
under remote loading, appears to obey micro-structural scaling laws, implying that the dimensions of the process region stay
essentially constant during crack expansion, rather than increasing with crack length. Therefore, expanding mode II cracks
can almost reach the Rayleigh velocity, and actually also intersonic velocities. An expanding mode I crack, on the other hand,
seems to obey continuum scaling laws, implying that the dimensions of the process region increase in proportion to crack length,
leading to self-similar crack expansion at a velocity significantly below the Rayleigh speed and dependent on the remote load. 相似文献
98.
LIU ZhiQiang LAI YuanMing ZHANG MingYi & ZHANG XueFu State Key Laboratory of Frozen Soil Engineering Cold Arid Regions Environmental Engineering Research Institute Chi- nese Academy of Sciences Lanzhou China School of Civil Engineering Lanzhou Jiao Tong University Lanzhou China Chongqing Jiao Tong University Chongqing China 《中国科学D辑(英文版)》2007,50(3):404-410
The stochastic finite element equations for random temperature are obtained using the first-order per-turbation technique taking into account the random thermal properties and boundary condition, based on heat transfer variational principle. The local average method for 2-D is used to discretize random fields. Then, the random temperature fields of embankment in cold regions are investigated on condi-tion that the thermal properties and boundary condition are taken as random fields, respectively, by using the program, which is written by the methods. The expected value of temperature field and the standard deviation of the temperature field of embankment in cold regions are obtained and analyzed. 相似文献
99.
100.
“醉汉林”一般被当做滑坡存在的一种标志。在陕西宝鸡地区进行地质灾害详细调查的过程中,发现变形边坡也有“醉汉林”分布。对陕西陇县郭家庄变形边坡“醉汉林”的树木倾斜角与边坡的倾角进行了测量,并结合几何学分析,认为树木倾斜角反映了边坡倾角的变化,并得出边坡倾角不断变陡是该地区边坡变形的一种主要方式的结论。研究结果表明,“醉汉林”有着多样而具体的指示意义:“醉汉林”记录了边坡变形的历史,可以作为区分滑坡与变形边坡的标志,“醉汉林”可以指示滑坡及边坡的状态,还可以判断滑坡剪出口是否存在。 相似文献