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   439032篇
  免费   5748篇
  国内免费   1283篇
化学   236008篇
晶体学   6520篇
力学   18879篇
综合类   13篇
数学   50878篇
物理学   133765篇
  2021年   3868篇
  2020年   4285篇
  2019年   4605篇
  2018年   5943篇
  2017年   5822篇
  2016年   9000篇
  2015年   5727篇
  2014年   8752篇
  2013年   20530篇
  2012年   15942篇
  2011年   19624篇
  2010年   13729篇
  2009年   13551篇
  2008年   17908篇
  2007年   17805篇
  2006年   16481篇
  2005年   14740篇
  2004年   13713篇
  2003年   12040篇
  2002年   11889篇
  2001年   13502篇
  2000年   10123篇
  1999年   7962篇
  1998年   6602篇
  1997年   6352篇
  1996年   6124篇
  1995年   5501篇
  1994年   5417篇
  1993年   5220篇
  1992年   5855篇
  1991年   5939篇
  1990年   5675篇
  1989年   5489篇
  1988年   5502篇
  1987年   5393篇
  1986年   5106篇
  1985年   6583篇
  1984年   6720篇
  1983年   5317篇
  1982年   5397篇
  1981年   5386篇
  1980年   4958篇
  1979年   5364篇
  1978年   5503篇
  1977年   5393篇
  1976年   5333篇
  1975年   4921篇
  1974年   4891篇
  1973年   4891篇
  1972年   3463篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
Journal of Solid State Electrochemistry - Oxygen transport in ceramic oxide materials has been actively explored over the past decades. This is due to the desire to design high-temperature...  相似文献   
152.
A fully quantitative theory of the relationship between protein conformation and optical spectroscopy would facilitate deeper insights into biophysical and simulation studies of protein dynamics and folding. In contrast to intense bands in the far-ultraviolet, near-UV bands are much weaker and have been challenging to compute theoretically. We report some advances in the accuracy of calculations in the near-UV, which were realised through the consideration of the vibrational structure of the electronic transitions of aromatic side chains.  相似文献   
153.
Russian Journal of General Chemistry - The technical legal acts that regulate the quality and safety parameters of mineral waters out were analyzed. Seven samples of mineral waters produced in...  相似文献   
154.
Stozharov  V. M. 《Technical Physics》2020,65(7):1071-1075
Technical Physics - Glasslike dielectrics are investigated by methods of plasmon dispersion and asymmetry of the number of localized electrons in the region in which total external reflection of...  相似文献   
155.
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   
156.
157.
158.
159.
Galkina  E. G.  Zaspel  C. E.  Ivanov  B. A.  Kulagin  N. E.  Lerman  L. M. 《JETP Letters》2019,110(7):481-486
JETP Letters - The motion of domain walls in GdFeCo-type ferrimagnets near the point of compensation of sublattice spins s1 and s2, when the effects of the exchange increase in the limiting wall...  相似文献   
160.
Let F be a field of characteristic 2. In this paper we give a complete computation of the kernel of the homomorphism H2m+1(F)?H2m+1(L) induced by scalar extension, where L/F is a purely inseparable extension (of any degree), H2m+1(F) is the cokernel of the Artin–Schreier operator ?:ΩFm?ΩFm/dΩFm?1 given by: xdx1x1?dxmxm?(x2?x)dx1x1?dxmxm+dΩFm?1, where ΩFm is the space of absolute m-differential forms over F and d is the differential operator. Other related results are included.  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