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   3319篇
  免费   139篇
  国内免费   7篇
化学   2242篇
晶体学   49篇
力学   123篇
数学   345篇
物理学   706篇
  2023年   23篇
  2022年   60篇
  2021年   73篇
  2020年   72篇
  2019年   62篇
  2018年   59篇
  2017年   56篇
  2016年   120篇
  2015年   93篇
  2014年   136篇
  2013年   210篇
  2012年   297篇
  2011年   273篇
  2010年   179篇
  2009年   152篇
  2008年   220篇
  2007年   212篇
  2006年   194篇
  2005年   144篇
  2004年   135篇
  2003年   105篇
  2002年   111篇
  2001年   57篇
  2000年   57篇
  1999年   24篇
  1998年   19篇
  1997年   14篇
  1996年   17篇
  1995年   14篇
  1994年   15篇
  1993年   21篇
  1992年   12篇
  1991年   15篇
  1990年   18篇
  1989年   19篇
  1988年   12篇
  1987年   14篇
  1986年   10篇
  1985年   7篇
  1984年   12篇
  1983年   7篇
  1982年   7篇
  1981年   8篇
  1980年   16篇
  1979年   12篇
  1978年   16篇
  1977年   10篇
  1976年   9篇
  1974年   6篇
  1973年   6篇
排序方式: 共有3465条查询结果,搜索用时 15 毫秒
991.
We report the synthesis of a series of novel stilbene‐based (St) Fischer base analogs of leuco‐triarylmethane (LTAM) dyes by treating Fischer base with (E)‐4‐styrylbenzaldehyde derivatives. All St‐LTAM molecules examined herein are characterized by 1D and 2D NMR. They were found to exhibit ZE configuration and isomerize to their diastereomers EE and ZZ in 2–3 h. They exhibit type I behavior of diastereomeric isomerization. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
992.
993.
Recently, shearlet systems were introduced as a means to derive efficient encoding methodologies for anisotropic features in 2-dimensional data with a unified treatment of the continuum and digital setting. However, only very few construction strategies for discrete shearlet systems are known so far.  相似文献   
994.
Thin ZnSe layers were deposited on ZnO nanowires by a novel successive ionic layer adsorption and reaction technique in order to solve recombination problems in ZnO nanowire-based dye-sensitized solar cells (DSSCs). Cell efficiency increased from 0.1 to 1.3–1.4% with the deposition of a 9- to13-nm-thick ZnSe shell on ZnO nanowires due to a large increase in JSC. The dramatic increase in JSC and cell efficiency is due to the facilitation of electron transfer related to ambipolar diffusion by the formation of a type II band alignment and the suppression of recombination in the presence of the ZnSe shell.  相似文献   
995.
Milling is an influential factor that affects the nutritional components in rice. However, the alteration of rice constituents by milling has not been thoroughly examined. In this study, rice with various degrees of milling was analyzed by gas chromatography–mass spectrometry and high-performance liquid chromatography–mass spectrometry. Principal component analysis and partial least square-discriminant analysis were performed to characterize the nutritional components that have significant changes during milling. The concentrations of sugars and sugar alcohols decreased while the phospholipids increased in accordance with the milling degree. These results provide a contrast to the common idea that brown rice is nutritionally superior to white rice. In conclusion, the knowledge of nutritional alterations related to milling may benefit rice production and consumption.  相似文献   
996.
997.
998.
The aim of this study was to determine the anti-osteoarthritic effects of LI73014F2, which consists of Terminalia chebula fruit, Curcuma longa rhizome, and Boswellia serrata gum resin in a 2:1:2 ratio, in the monosodium iodoacetate (MIA)-induced osteoarthritis (OA) rat model. LI73014F2 was orally administered once per day for three weeks. Weight-bearing distribution and arthritis index (AI) were measured once per week to confirm the OA symptoms. Synovial membrane, proteoglycan layer, and cartilage damage were investigated by histological examination, while synovial fluid interleukin-1β level was analyzed using a commercial kit. Levels of pro-inflammatory mediators/cytokines and matrix metalloproteinases (MMPs) in the cartilage tissues were investigated to confirm the anti-osteoarthritic effects of LI73014F2. LI73014F2 significantly inhibited the MIA-induced increase in OA symptoms, synovial fluid cytokine, cartilage damage, and expression levels of pro-inflammatory mediators/cytokines and MMPs in the articular cartilage. These results suggest that LI73014F2 exerts anti-osteoarthritic effects by regulating inflammatory cytokines and MMPs in MIA-induced OA rats.  相似文献   
999.
1000.
We study a new asymptotic invariant of a pair consisting of a group and a subgroup, which we call the commensurator growth. We compute the commensurator growth for several examples, concentrating mainly on the case of a locally compact topological group and a lattice inside it.  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