全文获取类型
收费全文 | 1728篇 |
免费 | 69篇 |
国内免费 | 36篇 |
专业分类
化学 | 826篇 |
晶体学 | 1篇 |
力学 | 557篇 |
综合类 | 72篇 |
数学 | 60篇 |
物理学 | 317篇 |
出版年
2024年 | 4篇 |
2023年 | 37篇 |
2022年 | 44篇 |
2021年 | 63篇 |
2020年 | 52篇 |
2019年 | 43篇 |
2018年 | 46篇 |
2017年 | 75篇 |
2016年 | 56篇 |
2015年 | 49篇 |
2014年 | 61篇 |
2013年 | 199篇 |
2012年 | 79篇 |
2011年 | 61篇 |
2010年 | 61篇 |
2009年 | 72篇 |
2008年 | 84篇 |
2007年 | 89篇 |
2006年 | 106篇 |
2005年 | 68篇 |
2004年 | 69篇 |
2003年 | 52篇 |
2002年 | 62篇 |
2001年 | 43篇 |
2000年 | 36篇 |
1999年 | 29篇 |
1998年 | 20篇 |
1997年 | 24篇 |
1996年 | 23篇 |
1995年 | 19篇 |
1994年 | 24篇 |
1993年 | 18篇 |
1992年 | 11篇 |
1991年 | 10篇 |
1990年 | 5篇 |
1989年 | 13篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有1833条查询结果,搜索用时 15 毫秒
111.
V. F. Nesterenko 《高压研究》2013,33(5-6):767-772
Abstract The properties of high Tc-ceramics (Y-123, Bi-1112, Bi-4334, Bi-4457, (Bi-Pb)-4457) under shock loading and subsequent heat treatment were investigated. The peculiarities of their structure, tecture creation, changes of superconductivity parameters depending on loading conditions at P~ 10GPa Were revealed, and regimes of heat treatment were determined. The possibilities of obtaining crack-free cylindrical superconducting shields as well as strong metal high-Tcceramic joints were demonstrated. 相似文献
112.
Radon exhalation rate from fly ash samples and from the homogeneous mixture of fly ash of different proportions additive in soil and cement samples to study the effect of the addition was measured by cup dosimeter using SSNTDs. Radon activities were found to vary from (1018±38) to ( whereas the radon exhalation rate varied from (366±14) to . A gradual increase has been observed in samples having fly ash as an additive in cement samples whereas a gradual decrease was observed in soil samples after the addition of fly ash. 238U in fly ash was measured by a low-level NaI (Tl)-based gamma ray spectrometer. The results show enhancement in U concentration in fly ash as compared to coal samples, whereas radon exhalation rate is less in fly ash samples. 相似文献
113.
殷志刚 《新疆大学学报(理工版)》2002,19(2):144-147
在田间利用盐分传感器对土壤溶液电导率连续观测表明,施用美地那可在灌水期间增加表层,10cm,30cm,深土壤溶液盐分淋洗量,在未灌水期间抑制这些土层土壤溶液中盐分累积,60cm深土壤液电导率变化较以上土层缓和,田间施用美地那对该层土壤液含盐量影响不大。 相似文献
114.
The present study investigated the modification of mesoscale inhomogeneous distribu-tion of soil wetness, resulting from mesoscale irrigation over arid or semiarid lands in mid-latitude in the later summer or early autumn, on mesoscale climate under conditions withand without synoptic flow influence, using an interactive model between soil and atmo-sphere. The simulations indicated that after a mesoscale irrgation, a wet soil breeze circu-lation was thermally forced, which was, in many features, similar to that of the sea breezecirculation. The influence of synoptic flows on the structure of thermally--induced wet soilbreeze circulation was also discussed. 相似文献
115.
116.
Pournin L Ramaioli M Folly P Liebling TM 《The European physical journal. E, Soft matter》2007,23(2):229-235
We study the jamming of bead assemblies placed in a
cylindrical container whose bottom is pierced with a circular
hole. Their jamming behavior is quantified here by the median
jamming diameter, that is the diameter of the hole for which the
jamming probability is 0.5. Median jamming diameters of
monodisperse assemblies are obtained numerically using the
Distinct Element Method and experimentally with steel beads. We
obtain good agreement between numerical and experimental results.
The influence of friction is then investigated. In particular, the
formation of concentric bead rings is observed for low frictions.
We identify this phenomenon as a boundary effect and study its
influence on jamming. Relying on measures obtained from
simulation runs, the median jamming diameter of bidisperse bead
assemblies is finally found to depend only on the volume-average
diameter of their constituting beads. We formulate this as a
tentative law and validate it using bidisperse assemblies of
steel beads. 相似文献
117.
Vandewalle N Lumay G Gerasimov O Ludewig F 《The European physical journal. E, Soft matter》2007,22(3):241-248
This article is a review of our recent and new experimental works on granular compaction. The effects of various microscopic
parameters on the
compaction dynamics are addressed, in particular the influence
of the grain shape, the friction and the cohesion between the grains. Two
dimensionnal and three dimensionnal systems are analysed. And the role of
dimensionality will be emphasized. Theoretical and numerical investigations provide additional informations about that phenomenon.
Indeed numerical models permit us to study the influence of some parameters not easily accessible experimentally. Our results
show that the above mentioned parameters have a deep impact on the compaction dynamics. Anisotropic grains lead to two different
compaction regimes separated by a “burst" of the packing fraction. Friction is observed to modify how the grains are arranged
in the pile. This is confirmed by numerical simulations. Cohesive forces between particles inhibit compaction and lead to
extremely low values of the packing fraction. 相似文献
118.
香港花岗岩风化分级化学指标体系与风化壳分带 总被引:5,自引:1,他引:5
火成岩的化学风化过程实质上就是碱、碱土金属组分水解淋失与脱硅富铁铝化的地球化学过程。不同风化程度的岩石处于整个化学风化过程的不同阶段,因而具有不同的化学成分和风化度指标。笔者在对香港九龙两个地方5个钻孔共计150件不同深度、不同风化程度的样品化学全分析结果与岩土风化程度宏观判别结果的相互对比、选择和确认的基础上,建立了香港地区花岗岩风化岩土风化程度工程分级的化学指标体系。这一研究成果的提出不仅有利于提高花岗岩风化岩土工程分类的科。学性、可靠性和实用性,而且可以为风化岩土工程特性与风化作用关系研究提供理论依据。 相似文献
119.
运用可拓学的基本理论,建立了膨胀土可拓评价模型。以此模型为基础,对荆门热电厂的膨胀土进行了可拓综合评价,并将判别结果与分级膨胀量评价法的判别结果进行了对比,其结果是一致的,说明该方法是可行的。 相似文献
120.