全文获取类型
收费全文 | 4635篇 |
免费 | 339篇 |
国内免费 | 335篇 |
专业分类
化学 | 2601篇 |
晶体学 | 25篇 |
力学 | 883篇 |
综合类 | 31篇 |
数学 | 812篇 |
物理学 | 957篇 |
出版年
2023年 | 25篇 |
2022年 | 61篇 |
2021年 | 63篇 |
2020年 | 82篇 |
2019年 | 74篇 |
2018年 | 81篇 |
2017年 | 98篇 |
2016年 | 125篇 |
2015年 | 163篇 |
2014年 | 154篇 |
2013年 | 305篇 |
2012年 | 293篇 |
2011年 | 273篇 |
2010年 | 219篇 |
2009年 | 262篇 |
2008年 | 291篇 |
2007年 | 298篇 |
2006年 | 250篇 |
2005年 | 255篇 |
2004年 | 214篇 |
2003年 | 205篇 |
2002年 | 166篇 |
2001年 | 126篇 |
2000年 | 137篇 |
1999年 | 98篇 |
1998年 | 123篇 |
1997年 | 109篇 |
1996年 | 85篇 |
1995年 | 92篇 |
1994年 | 66篇 |
1993年 | 75篇 |
1992年 | 56篇 |
1991年 | 37篇 |
1990年 | 50篇 |
1989年 | 34篇 |
1988年 | 29篇 |
1987年 | 35篇 |
1986年 | 20篇 |
1985年 | 16篇 |
1984年 | 22篇 |
1983年 | 7篇 |
1982年 | 27篇 |
1981年 | 24篇 |
1980年 | 15篇 |
1979年 | 11篇 |
1978年 | 16篇 |
1977年 | 7篇 |
1976年 | 9篇 |
1974年 | 5篇 |
1972年 | 7篇 |
排序方式: 共有5309条查询结果,搜索用时 0 毫秒
981.
This work aims at developing/combining numerical tools adapted to the simulation of the near field of highly underexpanded jets. An overview of the challenging numerical problems related to the complex shock/expansion structure encountered in these flows is given and an efficient and low‐cost numerical strategy is proposed to overcome these, even on short computational domains. Based on common upwinding algorithms used on unstructured meshes in a mixed finite‐volume/finite‐element approach, it relies on an appropriate utilization of zonal anisotropic remeshing algorithms. This methodology is validated for the whole near field of cold air jets issuing from axisymmetric convergent nozzles and yielding various underexpansion ratios. In addition, the most usual corrections of the k–ε model used to take into account the compressibility effects on turbulence are precisely assessed. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
982.
The finite volume effect of baryons in strange hadronic matter (SHM) is studied within the framework of relativistic mean-field theory. As this effect is concerned, the saturation density of SHM turns lower, and the binding energy per baryon decreases.
Its influence to the compression modulus of SHM is also discussed. 相似文献
983.
984.
Extreme properties of quermassintegrals of convex bodies 总被引:3,自引:0,他引:3
In this paper, we establish two theorems for the quermassintegrals of convex bodies, which are the generalizations of the
well-known Aleksandrov’ s projection theorem and Loomis-Whitney’ s inequality, respectively. Applying these two theorems,
we obtain a number of inequalities for the volumes of projections of convex bodies. Besides, we introduce the concept of the
perturbation element of a convex body, and prove an extreme property of it. 相似文献
985.
In this study we revisit Schardin's problem by investigating experimentally shock waves diffracting over a finite wedge and
interacting with the tip vortices in a complicated manner. Holographic interferometry and shadowgraphy were used in a shock
tube for a shock Mach number . Numerical simulations were carried out to obtain complementary flow data. The experimental results show that diverging acoustic
waves are generated due to the interaction between shock waves and vortexlets along the slip layer. By means of the computational
results obtained for short time intervals, and the corresponding optical images, analysis of the shock-vortex interactions
became possible for extended time periods.
Received 18 May 1998 / Accepted 4 March 1999 相似文献
986.
987.
测量了不同组分比的聚氨酯/丙烯酸酯类树脂(PU/VERH)的化学计量和化学不计量同时互穿网络聚合物SINs(Simultaneous
interpenetrating polymer networks)的正电子湮没寿命参数.研究结果表明两种SINs随组分变化存在相转变过程;而且化学计量PU/VERH
SIN两组分间存在的较强化学键作用减小SINs平均自由体积孔洞尺寸,分子链段堆砌紧密,分子链段间相互作用增强.从而增强了互穿效果、极大地改善了SINs两组分之间的相溶性,从微观上改善了互穿网络聚合物的力学性能,为分子水平设计新型材料提供了实验依据. 相似文献
988.
Yu-Feng Hu 《Journal of solution chemistry》2000,29(12):1229-1236
An empirical approach is presented for the density of aqueous multicomponentsolutions conforming to the linear isopiestic relation. This approach can be usedto estimate the densities of multicomponent systems from data on the constituentbinary subsystems at the same water activity. Predicted and measured densitiesfor 22 mixtures have been compared, using the simple Young's rule, theisopycnotic mixing rule of Teng and Lenzi, and the present method. The present methodand Young's rule give the most accurate predictions for strong electrolyte mixtureswithout common ions and for the mixtures with strong ion complexes, respectively.There is no universal best method for the strong electrolyte mixtures with commonions. An extensive comparison has also been given between apparent molarvolume predictions by Young's rule and by the new method. The two rules arerelatively better for the strong electrolyte mixtures without common ions andmixtures containing the transition metal chlorides, respectively. However, neitheris universally better for mixtures of strong common-ion electrolytes. 相似文献
989.
MAIO Hong GAO Chong-Shou ZHUANG Peng-Fei 《理论物理通讯》2006,46(6):1040-1046
Bound states, such as qq and q^-q, may exist the volume of the bound states may evoke a reduction in investigate qualitatively the volume effect on the properties states start to be completely melted. 相似文献
990.
Vladimir Zakharov Mikhail Matsko Ludmila Echevskaya Tatiana Mikenas 《Macromolecular Symposia》2007,260(1):184-188
New experimental approach was used for analysis of molecular weight distribution (MWD) of polymers produced over titanium-magnesium catalysts (TMC). Polymers were fractionated on to fractions with narrow MWD (polydispersity (PD) values Mw/Mn ≤ 2). Then some of these fractions were combined to get the minimal quantity of fractions with PD values close to 2 (Flory components). It was found that three fractions corresponding to three groups of active centers are sufficient for proper fitting experimental MWD curve for PE obtained over TMC with different Ti content and with different hydrogen concentration in polymerization. 相似文献