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   257篇
  免费   7篇
化学   181篇
晶体学   2篇
力学   4篇
数学   37篇
物理学   40篇
  2023年   1篇
  2022年   11篇
  2021年   17篇
  2020年   10篇
  2019年   5篇
  2018年   6篇
  2017年   4篇
  2016年   4篇
  2015年   11篇
  2014年   9篇
  2013年   20篇
  2012年   19篇
  2011年   23篇
  2010年   15篇
  2009年   14篇
  2008年   24篇
  2007年   11篇
  2006年   13篇
  2005年   10篇
  2004年   9篇
  2003年   5篇
  2002年   6篇
  1999年   1篇
  1998年   2篇
  1997年   1篇
  1995年   3篇
  1994年   2篇
  1993年   1篇
  1992年   1篇
  1991年   1篇
  1990年   1篇
  1983年   2篇
  1982年   1篇
  1979年   1篇
排序方式: 共有264条查询结果,搜索用时 15 毫秒
181.
We indicate a new approach to the deformation of three‐dimensional curved rods with variable cross‐section. The model consists of a system of nine ordinary differential equations for which we prove existence and uniqueness via the coercivity of the association bilinear form. From the geometrical point of view, we are using the Darboux frame or a new local frame requiring just a C1‐parameterization of the curve. Our model also describes the deformation occurring in the cross‐sections of the rod. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
182.
183.
184.
Nonlinear Dynamics - Many natural systems are organized as networks, in which the nodes interact in a time-dependent fashion. The object of our study is to relate connectivity to the temporal...  相似文献   
185.
Suzuki–Miyaura cross coupling reaction was used for access to new macrocycles exhibiting oligoethyleneoxide bridges and embedding bithiophene, terthiophene or 3,7-bis(thiophen-2-yl)-N-ethyl-10H-phenothiazine units. The synthesis was performed under various reaction conditions and different coupling types in order to establish the correlation between yields and employed solvents and bases. The structure of the compounds was supported by single crystal X-ray diffractometry, NMR, and MS experiments.  相似文献   
186.
The synthesis of new 3,7-dibromophenothiazine derivatives bearing bromoalkyl, mercaptoalkyl and alkylthioacetate groups on the N atom at position 10 is reported. The Suzuki coupling reaction of one of these derivatives via the bromine atoms at positions 3 and 7 with bromothiophene derivatives is also discussed.   相似文献   
187.
The gauge covariance of the wave function phase factor in noncommutative quantum mechanics (NCQM) is discussed. We show that the naive path integral formulation and an approach where one shifts the coordinates of NCQM in the presence of a background vector potential leads to the gauge non-covariance of the phase factor. Due to this fact, the Aharonov–Bohm phase in NCQM which is evaluated through the path-integral or by shifting the coordinates is neither gauge invariant nor gauge covariant. We show that the gauge covariant Aharonov–Bohm effect should be described by using the noncommutative Wilson lines, what is consistent with the noncommutative Schrödinger equation. This approach can ultimately be used for deriving an analogue of the Dirac quantization condition for the magnetic monopole.  相似文献   
188.

Background  

Parkinson's disease, for which currently there is no cure, develops as a result of progressive loss of dopamine neurons in the brain; thus, identification of any potential therapeutic intervention for disease management is of a great importance.  相似文献   
189.
In this paper the driven transport of linear polymers through a nanopore is presented. Biopolymer physical behavior in an external electric field is modeled and its motion is simulated using the Langevin impulse integrator method. Within fairly large limits, the polymer translocation time is inversely proportional with the electric field intensity and directly proportional with the polymer chain length.   相似文献   
190.

This paper deals with the study of compatibility between antihyperlipidemic agent atorvastatin calcium trihydrate (ATV) and eight pharmaceutical excipients used in the development of solid dosage forms, namely citric acid, anhydrous lactose, magnesium citrate, magnesium carbonate, sodium carboxymethyl cellulose, polyvinylpyrrolidone K30, colloidal silica and sorbitol. As investigational tools, universal attenuated total reflectance Fourier transform infrared spectroscopy and powder X-ray diffractogram patterns were used for binary mixtures of ATV with each excipient at ambient condition and then completed by subjecting the samples to thermal stress using thermal analysis (TG/DTG/HF), in non-isothermal conditions and in oxidative medium. It was shown the binary mixtures do not present interactions between ATV and excipients when stored under ambient conditions for 2 months, while under thermal stress, ATV presents interactions with sorbitol.

  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