全文获取类型
收费全文 | 83470篇 |
免费 | 1627篇 |
国内免费 | 1455篇 |
专业分类
化学 | 28633篇 |
晶体学 | 953篇 |
力学 | 7082篇 |
综合类 | 67篇 |
数学 | 32568篇 |
物理学 | 17249篇 |
出版年
2023年 | 206篇 |
2022年 | 265篇 |
2021年 | 289篇 |
2020年 | 380篇 |
2019年 | 364篇 |
2018年 | 10670篇 |
2017年 | 10460篇 |
2016年 | 6347篇 |
2015年 | 1200篇 |
2014年 | 665篇 |
2013年 | 774篇 |
2012年 | 4336篇 |
2011年 | 10986篇 |
2010年 | 5961篇 |
2009年 | 6375篇 |
2008年 | 6967篇 |
2007年 | 9094篇 |
2006年 | 516篇 |
2005年 | 1569篇 |
2004年 | 1695篇 |
2003年 | 2132篇 |
2002年 | 1180篇 |
2001年 | 398篇 |
2000年 | 425篇 |
1999年 | 267篇 |
1998年 | 272篇 |
1997年 | 216篇 |
1996年 | 279篇 |
1995年 | 178篇 |
1994年 | 128篇 |
1993年 | 140篇 |
1992年 | 89篇 |
1991年 | 86篇 |
1990年 | 79篇 |
1989年 | 77篇 |
1988年 | 72篇 |
1987年 | 69篇 |
1986年 | 69篇 |
1985年 | 57篇 |
1984年 | 52篇 |
1983年 | 50篇 |
1982年 | 46篇 |
1981年 | 40篇 |
1980年 | 47篇 |
1979年 | 48篇 |
1914年 | 45篇 |
1913年 | 40篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
A numerical model was developed and validated to investigate the fluid–structure interactions between fully developed pipe flow and core–shell-structured microcapsule in a microchannel. Different flow rates and microcapsule shell thicknesses were considered. A sixth-order rotational symmetric distribution of von Mises stress over the microcapsule shell can be observed on the microcapsule with a thinner shell configuration, especially at higher flow rate conditions. It is also observed that when being carried along in a fully developed pipe flow, the microcapsule with a thinner shell tends to accumulate stress at a higher rate compared to that with a thicker shell. In general, for the same microcapsule configuration, higher flow velocity would induce a higher stress level over the microcapsule shell. The deformation gradient was used to capture the microcapsule's deformation in the present study. The effect of Young's modulus on the microcapsule shell on the microcapsule deformation was investigated as well. Our findings will shed light on the understanding of the stability of core–shell-structured microcapsule when subjected to flow-induced shear stress in a microfluidic system, enabling a more exquisite control over the breakup dynamics of drug-loaded microcapsule for biomedical applications. 相似文献
2.
In the paper, the authors establish several integral representations for the generating functions of the large and little Schröder numbers and for the large and little Schröder numbers. 相似文献
3.
4.
Mesoscopic modeling at the pore scale offers great promise in exploring the underlying structure transport performance of flow through porous media. The present work studies the fluid flow subjected to capillarity-induced resonance in porous media characterized by different porous structure and wettability. The effects of porosity and wettability on the displacement behavior of the fluid flow through porous media are discussed. The results are presented in the form of temporal evolution of percentage saturation and displacement of the fluid front through porous media. The present study reveals that the vibration in the form of acoustic excitation could be significant in the mobilization of fluid through the porous media. The dependence of displacement of the fluid on physicochemical parameters like wettability of the surface, frequency along with the porosity is analyzed. It was observed that the mean displacement of the fluid is more in the case of invading fluid with wetting phase where the driving force strength is not so dominant. 相似文献
5.
6.
Sarah Peluse 《Israel Journal of Mathematics》2018,227(1):379-396
We prove that the group of diffeomorphisms of the interval [0, 1] contains surface groups whose action on (0, 1) has no global fix point and such that only countably many points of the interval (0, 1) have non-trivial stabiliser. 相似文献
7.
8.
通常采用以氢氧化物作为造孔剂,过渡金属硝酸盐或氯化物作为石墨化催化剂的传统两步法策略制备多孔石墨化碳材料。然而制备过程中多涉及有毒和腐蚀性试剂,且多步骤的过程耗时较长。本文以双氰胺为原料通过热缩聚反应得到g-C3N4,采用高铁酸钾为催化剂一步法实现g-C3N4的同步碳化-石墨化,并研究其光催化性能。与传统的两步法相比,该方法耗时少、效率高、无污染。与初始的g-C3N4材料相比,石墨化g-C3N4衍生碳质材料不仅显著改善了可见光的吸收,而且大大增强了光催化活性。研究了不同石墨化温度对g-C3N4衍生碳质材料在可见光下降解甲基橙溶液的影响。700 ℃下制备的衍生碳质材料的降解率为12.4 mg/g。光电化学测试结果表明,多孔g-C3N4衍生碳质材料的光生载流子密度、电荷分离和光电流(提高了5.4倍)均得到显著提高。因此,该简便、灵活方法为提高g-C3N4衍生碳质材料的吸附和光催化性能提供了一种有前景的、高效的途径。 相似文献
9.
Hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) have been deemed as clean and sustainable strategies to solve the energy crisis and environmental problems. Various catalysts have been developed to promote the process of HER and OER. Among them, two-dimensional covalent organic frameworks (2D COFs) have received great attention due to their diverse and designable structure. In this minireview, we mainly summarize the diverse linkages of 2D COFs and strategies for enhancing the catalytic performance of 2D COFs for HER and OER, such as introducing active building blocks, metal ions and tailored linkages. Furthermore, a brief outlook for the development directions of COFs in the field of HER and OER is provided, expecting to stimulate new opportunities in future research. 相似文献
10.