全文获取类型
收费全文 | 29086篇 |
免费 | 3948篇 |
国内免费 | 3973篇 |
专业分类
化学 | 10916篇 |
晶体学 | 193篇 |
力学 | 1589篇 |
综合类 | 169篇 |
数学 | 1495篇 |
物理学 | 10522篇 |
综合类 | 12123篇 |
出版年
2024年 | 130篇 |
2023年 | 378篇 |
2022年 | 812篇 |
2021年 | 894篇 |
2020年 | 1059篇 |
2019年 | 846篇 |
2018年 | 840篇 |
2017年 | 936篇 |
2016年 | 1085篇 |
2015年 | 1084篇 |
2014年 | 1586篇 |
2013年 | 1987篇 |
2012年 | 1769篇 |
2011年 | 1903篇 |
2010年 | 1524篇 |
2009年 | 1800篇 |
2008年 | 1756篇 |
2007年 | 2019篇 |
2006年 | 1880篇 |
2005年 | 1537篇 |
2004年 | 1341篇 |
2003年 | 1277篇 |
2002年 | 1116篇 |
2001年 | 961篇 |
2000年 | 892篇 |
1999年 | 792篇 |
1998年 | 673篇 |
1997年 | 597篇 |
1996年 | 487篇 |
1995年 | 436篇 |
1994年 | 417篇 |
1993年 | 325篇 |
1992年 | 321篇 |
1991年 | 282篇 |
1990年 | 252篇 |
1989年 | 222篇 |
1988年 | 182篇 |
1987年 | 143篇 |
1986年 | 96篇 |
1985年 | 71篇 |
1984年 | 47篇 |
1983年 | 22篇 |
1982年 | 39篇 |
1981年 | 35篇 |
1980年 | 31篇 |
1979年 | 28篇 |
1978年 | 13篇 |
1977年 | 22篇 |
1976年 | 14篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
The pollution source and pollution state of surface water is respectively assessed with equal-standard-pollution-load index and Nemero index, and the habitans' health is assessed as well by comparison with pre-development of geothermal field. Results show that: 1 ) Three pollutive factors obviously fail to attain the required standards and their order sorted by impact degree is As>F- >S2-. 2) The Nemero index of Donggua cross section of Duilongqu River is 0. 725and the water quality is at mildly-polluted level. 3) In Lhasa River, the Nemero indexes of cross sections affected by geothermal fields are much higher than that of the unaffected one, which shows the present and potential impacts of geothermal development. 4) Much more inhabitants nearby got trichomadesis sickness after geothermal development, which shows that the surface water pollution in this area has threatened the inhabitants' health. In addition, other environmental issues caused by Yangbajing geothermal development are analyzed and some countermeasures are proposed. 相似文献
142.
T. Beda 《Journal of Polymer Science.Polymer Physics》2007,45(13):1713-1732
A constitutive phenomenological model completing the Gent‐Thomas concept is carried out to formulate laws governing the hyperelastic behavior of incompressible rubber materials. It is shown that the phenomenological Gent‐Thomas model (1958) and the constrained chain model (1992) give similar precise results at small to moderate deformation. On the other hand, comparisons of the outcome of the proposed model with that of the molecular model from the combined concepts of Flory‐Erman and Boyce‐Arruda (2000), and with those of the phenomenological models of Ogden (1982), Yeoh‐Fleming (1997), Pucci‐Saccomandi (2002) and Beda (2005) are made. Residual inconveniences raised by attractive continuum models in rubber elasticity literature have been successfully overcome. Results from both the statistical and phenomenological mechanics concepts are compared with the data of some useful classical materials (rubbers of Treloar, Rivlin‐Saunders, Pak‐Flory and Yeoh‐Fleming). The results permit one to see salient equivalence of the two theories for a more reliable prediction of stress‐stretch response for all states of any mode of deformation. A complete and exhaustive analysis of the Mooney plot that combines small and very large extension‐compression has been quite essential in assessing the validity of models. A method of identification of material parameters is presented and data of the simple tension suffice for the determination of the parameter values. It is shown that the ordinary identification procedures, such as the usual least squares, a very much used numerical method in materials investigation, can be unsuitable in some cases of hyperelastic modeling. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1713–1732, 2007 相似文献
143.
144.
Regularity of Harmonic Functions in Cheeger-Type Sobolev Spaces 总被引:3,自引:0,他引:3
We give a geometric approach to the study of the regularity of harmonic functions in Cheeger-type Sobolev spaces, and prove the Hölder continuity of such functions. In the proof, we give a definition of an upper curvature bound of the unit sphere of a Banach space, which seems to be of independent interest. 相似文献
145.
146.
147.
Gu-Qiang Li 《Theoretical and Mathematical Physics》2007,151(1):586-589
We use the Parikh-Wilczek method to treat Hawking radiation as a tunneling process across the event horizon and calculate
the emission rate of a Gibbons-Maeda dilaton black hole. We show that if self-gravitation is taken into account, then the
radiation deviates from the purely thermal spectrum, and the corrected spectrum is consistent with an underlying unitary theory.
__________
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 151, No. 1, pp. 172–175, April, 2007. 相似文献
148.
用玻色子组态混合和玻色子表面δ相互作用研究核谱 总被引:2,自引:0,他引:2
用玻色子组态混合波函数和玻色子表面δ相互作用研究了三玻色子核46Ti和54Cr的sdgIBMI的能谱和E2跃迁概率,理论计算结果令人满意,比sdIBMI能拟合出更多的能级和E2跃迁概率,而且它们的误差更小. 说明g玻色子在振动区也起着重要的作用,同时进一步证明了这种玻色子组态混合模型是成功的. 相似文献
149.
叶世勇 《安徽师范大学学报(自然科学版)》1995,18(1):43-49
本文提出了最大成键能原理。由此出发,求出相应的最大成键能分子轨道及成键能,并得到了分子中各原子间的成键能,这些可以很好说明分子的成键和分子吸原子间键强度的性质,与实验事实吻合。同时,还可以得到分子的Mulliken's布居数,与通常的LCAO-MO方法一致。 相似文献
150.
V. L. Bratman G. G. Denisov A. V. Savilov 《International Journal of Infrared and Millimeter Waves》1995,16(3):459-471
A relatively high level of the minimal electron energy at the gyrotron output even at very large spread in pitch factor is explained. An estimation of the recuperation efficiency, which can be obtained due to this effect, is given. 相似文献