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   6692篇
  免费   304篇
  国内免费   61篇
化学   4666篇
晶体学   23篇
力学   154篇
数学   1088篇
物理学   1126篇
  2024年   7篇
  2023年   47篇
  2022年   152篇
  2021年   201篇
  2020年   136篇
  2019年   138篇
  2018年   136篇
  2017年   111篇
  2016年   254篇
  2015年   246篇
  2014年   256篇
  2013年   427篇
  2012年   445篇
  2011年   534篇
  2010年   321篇
  2009年   256篇
  2008年   460篇
  2007年   421篇
  2006年   431篇
  2005年   356篇
  2004年   302篇
  2003年   234篇
  2002年   207篇
  2001年   68篇
  2000年   73篇
  1999年   43篇
  1998年   68篇
  1997年   59篇
  1996年   68篇
  1995年   37篇
  1994年   46篇
  1993年   65篇
  1992年   65篇
  1991年   34篇
  1990年   23篇
  1989年   14篇
  1988年   11篇
  1987年   14篇
  1986年   19篇
  1985年   32篇
  1984年   37篇
  1983年   20篇
  1982年   24篇
  1981年   24篇
  1980年   18篇
  1979年   22篇
  1978年   21篇
  1977年   19篇
  1974年   6篇
  1973年   17篇
排序方式: 共有7057条查询结果,搜索用时 15 毫秒
1.
2.
Meccanica - Fiber reinforced materials are used in assorted engineering application and for this reason, new additive manufacturing technologies have been developed for this type of materials. With...  相似文献   
3.
Journal of Solid State Electrochemistry - In this study, galvanostatic electrolysis, through the use of the platinum supported on Ti (Ti/Pt) and Ti/TiO2-nanotubes/PbO2 anodes, was conducted in an...  相似文献   
4.
5.
Metabolomics is a potential tool for the discovery of new biomarkers in the early diagnosis of diseases. An ultra-fast gas chromatography system equipped to an electronic nose detector (FGC eNose) was used to identify the metabolomic profile of Volatile Organic Compounds (VOCs) in type 2 diabetes (T2D) urine from Mexican population. A cross-sectional, comparative, and clinical study with translational approach was performed. We recruited twenty T2D patients and twenty-one healthy subjects. Urine samples were taken and analyzed by FGC eNose. Eighty-eight compounds were identified through Kovats's indexes. A natural variation of 30% between the metabolites, expressed by study groups, was observed in Principal Component 1 and 2 with a significant difference (p < 0.001). The model, performed through a Canonical Analysis of Principal coordinated (CAP), allowed a correct classification of 84.6% between healthy and T2D patients, with a 15.4% error. The metabolites 2-propenal, 2-propanol, butane- 2,3-dione and 2-methylpropanal, were increased in patients with T2D, and they were strongly correlated with discrimination between clinically healthy people and T2D patients. This study identified metabolites in urine through FGC eNose that can be used as biomarkers in the identification of T2D patients. However, more studies are needed for its implementation in clinical practice.  相似文献   
6.
7.
8.
9.
Condensed matter systems, such as acoustics in flowing fluids, light in moving dielectrics, or quasiparticles in a moving superfluid, can be used to mimic aspects of general relativity. More precisely these systems (and others) provide experimentally accessible models of curved-space quantum field theory. As such they mimic kinematic aspects of general relativity, though typically they do not mimic the dynamics. Although these analogue models are thereby limited in their ability to duplicate all the effects of Einstein gravity they nevertheless are extremely important—they provide black hole analogues (some of which have already been seen experimentally) and lead to tests of basic principles of curved-space quantum field theory. Currently these tests are still in the realm of gedanken-experiments, but there are plausible candidate models that should lead to laboratory experiments in the not too distant future.  相似文献   
10.
We describe a semi-analytical numerical method for coherent isotropic scattering time-dependent radiative transfer problems in slab geometry. This numerical method is based on a combination of two classes of numerical methods: the spectral methods and the Laplace transform (LTSN) methods applied to the radiative transfer equation in the discrete ordinates (SN) formulation. The basic idea is to use the essence of the spectral methods and expand the intensity of radiation in a truncated series of Laguerre polynomials in the time variable and then solve recursively the resulting set of “time-independent” SN problems by using the LTSN method. We show some numerical experiments for a typical model problem.  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