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排序方式: 共有825条查询结果,搜索用时 46 毫秒
51.
用 732型强酸性阳离子交换树脂分离富集 ,并与改进的流动注射 (双流路 )相结合 ,建立了新型、高效的流动注射 -阳离子交换预富集 - ICP- AES在线分析体系。研究了酸度、流速、淋洗剂浓度等的选择、共存离子的干扰情况并应用于矿样的分析。 Ca,Mg,Al,Fe各元素的检出限分别为 0 .9μg/ L,0 .6 μg/ L,5.5μg/ L,1 .4μg/ L;1 0次测量的相对标准偏差分别为 3.4 4% ,1 .53% ,1 .6 0 % ,2 .58%。回收率在 93.0 %~ 1 0 1 .4 %之间。分析速度可达每小时 4 0个样品。 相似文献
52.
李任伟 《中国科学B辑(英文版)》1990,(3)
Not only the mudstones and carbonates deposited in hypersaline environments, but also evaporites can be source rocks of petroleum. They all have a peculiar composition of hydrocarbon such as the strong predominance of phytane, the richness in gammacerane, the frequent preference of even carbon number n-alkanes, and have a generative potential for less mature oils in diagenesis of organic matter. 相似文献
53.
54.
将材料的破坏归结为剪切破坏,每种材料对应于特定的剪切滑动面,抗剪强度为滑动面上正应力的函数,基于不同材料的强度特性将一系列的剪切滑动面统一起来,建立了岩土材料的非线性统一强度模型.非线性统一强度模型的滑动面为β应力空间内的等倾面,在β应力空间内的强度面为圆锥面;在普通应力空间内的强度面为一系列连续光滑、外凸的锥面,在偏平面上强度曲线涵盖了从下限Matsuoka-Nakai曲线到上限Drucker-Prager圆之间的所有区域,子午面上强度线为直线.非线性统一强度模型只有3个材料参数,参数都具有明确的物理意义,通过与国内外学者已取得的岩土类材料真三轴强度试验结果的比较,表明模型可适用于多种类型的材料,并合理描述其非线性强度特性. 相似文献
55.
Burst event detection in wall turbulence by WVITA method 总被引:2,自引:0,他引:2
Wavelet Variable Interval Time Average (WVITA) is introduced as a method incorporating burst event detection in wall turbulence.
Wavelet transform is performed to unfold the longitudinal fluctuating velocity time series measured in the near wall region
of a turbulent boundary layer using hot-film anemometer. This unfolding is both in time and in space simultaneously. The splitted
kinetic of the longitudinal fluctuating velocity time series among different scales is obtained by integrating the square
of wavelet coefficient modulus over temporal space. The time scale that related to burst events in wall turbulence passing
through the fixed probe is ascertained by maximum criterion of the kinetic energy evolution across scales. Wavelet transformed
localized variance of the fluctuating velocity time series at the maximum kinetic scale is put forward instead of localized
short time average variance in Variable Interval Time Average (VITA) scheme. The burst event detection result shows that WVITA
scheme can avoid erroneous judgement and solve the grouping problem more effectively which is caused by VITA scheme itself
and can not be avoided by adjusting the threshold level or changing the short time average interval.
The project supported by the National Natural Science Foundation of China (19732005) and the National Climbing Project of
China 相似文献
56.
57.
Ahmad Pouya 《European Journal of Mechanics - A/Solids》2000,19(6):1015
Rock salt is considered as a pure aggregate of halite (mineral NaCl) crystals and its behaviour is investigated by a micro–macro approach. The behaviour of the polycrystalline aggregate is deduced from the properties of the constituent halite crystals. A model for the elastoplastic behaviour of halite crystal has been deduced from experimental data available in the literature. The basic equations of the micro–macro model for the polycrystalline medium and the calculation method are then presented and the elastoplastic behaviour of rock salt is investigated by this method. The hardening effects obtained for the polycrystal are found to be very different from those obtained for FCC metal polycrystals. The differences are explained as a consequence of differences of families of glide systems in these crystals. Finally, the internal stresses in the polycrystal are studied in order to elucidate the origin of cracking and damage of the rock salt. 相似文献
58.
59.
A split Hopkinson pressure bar technique to determine compressive stress-strain data for rock materials 总被引:14,自引:0,他引:14
This paper presents a split Hopkinson pressure bar technique to obtain compressive stress-strain data for rock materials.
This technique modifies the conventional split Hopkinson bar apparatus by placing a thin copper disk on the impact surface
of the incident bar. When the striker bar impacts the copper disk, a nondispersive ramp pulse propagates in the incident bar
and produces a nearly constant strain rate in a rock sample. Data from experiments with limestone show that the samples are
in dynamic stress equilibrium and have constant strain rates over most of the test durations. In addition, the ramp pulse
durations can be controlled such that samples are unloaded just prior to failure. Thus, intact samples that experience strains
beyond the elastic region and postpeak stresses can be retrieved for microstructural evaluations. The paper also presents
analytical models that predict the time durations for sample equilibrium and constant strain rate. Model predictions are in
good agreement with measurements. 相似文献
60.
爆生气体作用下岩石裂纹的扩展机理 总被引:29,自引:0,他引:29
在爆生气体作用下 ,爆破近区的裂纹在气体驱动压力下扩展 ,而爆破中区的裂纹扩展是在气体膨胀压力场和原岩应力共同作用下发生的。基于岩石细观损伤断裂理论 ,认为裂纹扩展的过程就是裂纹尖端到周围岩石的逐渐损伤引起的损伤区移动过程 ;建立了这两个区域的损伤断裂准则和裂纹尖端的损伤局部化模型 ,可以更好地反映爆生气体作用下裂纹扩展的实际过程。 相似文献