首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   5951篇
  免费   1112篇
  国内免费   799篇
化学   4369篇
晶体学   102篇
力学   383篇
综合类   44篇
数学   693篇
物理学   2271篇
  2024年   23篇
  2023年   136篇
  2022年   246篇
  2021年   251篇
  2020年   344篇
  2019年   299篇
  2018年   273篇
  2017年   282篇
  2016年   354篇
  2015年   392篇
  2014年   359篇
  2013年   500篇
  2012年   561篇
  2011年   537篇
  2010年   395篇
  2009年   374篇
  2008年   387篇
  2007年   319篇
  2006年   307篇
  2005年   260篇
  2004年   214篇
  2003年   150篇
  2002年   160篇
  2001年   112篇
  2000年   103篇
  1999年   98篇
  1998年   39篇
  1997年   45篇
  1996年   39篇
  1995年   34篇
  1994年   12篇
  1993年   29篇
  1992年   23篇
  1991年   16篇
  1990年   12篇
  1989年   10篇
  1988年   19篇
  1986年   15篇
  1985年   16篇
  1984年   14篇
  1983年   6篇
  1982年   13篇
  1980年   6篇
  1979年   11篇
  1978年   8篇
  1977年   5篇
  1976年   7篇
  1975年   7篇
  1974年   5篇
  1973年   5篇
排序方式: 共有7862条查询结果,搜索用时 15 毫秒
141.
The behavior of water in close proximity to other materials under ambient conditions is of great significance due to its importance in a broad range of daily applications and scientific research. The structure and dynamics of water at an interface or in a nanopore are often significantly different from those of its bulk counterpart. Until recently, experimental access to these interfacial water structures was difficult to realize. The advent of two-dimensional materials, especially graphene, and the availability of various scanning probe microscopies were instrumental to visualize, characterize and provide fundamental knowledge of confined water. This review article summarizes the recent experimental and theoretical progress in a better understanding of water confined between layered Van der Waals materials. These results reveal that the structure and stability of the hydrogen bonded networks are determined by the elegant balance between water-surface and water-water interactions. The water-surface interactions often lead to structures that differ significantly from the conventional bilayer model of natural ice. Here, we review the current knowledge of water adsorption in different environments and intercalation within various confinements. In addition, we extend this review to cover the influence of interfacial water on the two-dimensional material cover and summarize the use of these systems in potential novel applications. Finally, we discuss emerged issues and identify some flaws in the present understanding.  相似文献   
142.
The steady-state behavior of the Anaerobic Digestion Model No. 1 (ADM1) with respect to dilution rate and substrate concentration is analyzed in this study. Thereby, up to ten coexisting steady-state solutions are observed under the same operating conditions. The parameter region of a methane producing operation is limited regarding high dilution rates as well as low or high substrate concentrations. The underlying mechanisms causing those limits are investigated in detail, and the common core is identified, namely a positive feedback loop between growth of acetate degraders and acetate itself. The difference lies in the activation mechanisms of this feedback loop, which differs in the three investigated cases. The comparison of the present results with literature studies of simpler two-step models reveals qualitative differences regarding the substrate concentration. Therefore, an alternative simplified model is suggested, which shows qualitatively the same bifurcation behavior as the ADM1 considering variation of the substrate concentration.  相似文献   
143.
A comprehensive study on Raman spectroscopy with different excitation wavelengths, sample sizes, and sample shapes for optic phonons (OPs) and acoustic phonons (APs) in polar and non-polar nano-semiconductors has been performed. The study affirms that the finite size effect does not appear in the OPs of polar nano-semiconductors, while it exists in all other types of phonons. The absence of the FSE is confirmed to originate from the long-range Fr¨ohlich interaction and the breaking of translation symmetry. The result indicates that the Raman spectra of OPs cannot be used as a method to characterize the scale and crystalline property of polar nano-semiconductors.  相似文献   
144.
A set of numerical experiments has been conducted to study the effect of a precursor fluid layer on the motion of two phase system in a channel. This system is characterized by coupled Cahn-Hillard and Navier-Stokes system together with slip boundary conditions. The solution of the governing equation involves first the solution of Cahn-Hillard equation with semi-implicit and Mixed finite element discritization with a convex splitting scheme. The Navier-Stokes equations are then solved with a P2-P0 mixed finite element method. Three cases have been investigated; in the first the effect of different wettability scenarios with no precursor layer has been investigated. In the second scenario, the effect of the precursor layer for different wettability conditions is investigated. In the third case, the effect of the thickness of the precursor layer is investigated. It is found that, wettability conditions have considerable effect on the flow of the considered two-phase system. Furthermore the existence of the precursor layer has additional influence on the breakthrough of the phases.  相似文献   
145.
146.
147.
148.
149.
150.
Cellulose - Mercury contamination in drinking water is a worldwide problem due to its severely harming effects on the human body. A nanostructured natural bioadsorbent, carboxycellulose nanofiber...  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号