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   333篇
  免费   12篇
  国内免费   2篇
化学   290篇
晶体学   1篇
力学   6篇
数学   20篇
物理学   30篇
  2024年   1篇
  2023年   1篇
  2022年   10篇
  2021年   8篇
  2020年   11篇
  2019年   11篇
  2018年   11篇
  2017年   8篇
  2016年   16篇
  2015年   13篇
  2014年   11篇
  2013年   21篇
  2012年   26篇
  2011年   21篇
  2010年   21篇
  2009年   12篇
  2008年   23篇
  2007年   20篇
  2006年   18篇
  2005年   17篇
  2004年   12篇
  2003年   11篇
  2002年   5篇
  2001年   3篇
  2000年   4篇
  1999年   2篇
  1998年   2篇
  1997年   3篇
  1996年   4篇
  1995年   2篇
  1994年   4篇
  1993年   1篇
  1991年   1篇
  1990年   1篇
  1984年   2篇
  1983年   2篇
  1982年   2篇
  1980年   1篇
  1978年   1篇
  1976年   1篇
  1974年   1篇
  1973年   1篇
  1889年   1篇
排序方式: 共有347条查询结果,搜索用时 15 毫秒
201.
202.
203.
Three Lewis acid–base adducts t‐Bu3Ga–EPh3 (E = P 1 , As 2 , Sb 3 ) were synthesized by reactions of Ph3E and t‐Bu3Ga and characterized by heteronuclear NMR (1H, 13C (31P)) and IR spectroscopy, elemental analysis and single crystal X‐ray diffraction. Their structural parameters are discussed and compared to similar t‐Bu3Ga adducts. The strength of the donor‐acceptor interactions within 1 – 3 was investigated in solution by temperature‐dependent 1H NMR spectroscopy and by quantum chemical calculations.  相似文献   
204.
205.
206.
In this paper, we introduce mathematical models for studying a supernetwork that is comprised of closely connected groups of subnetworks. For several related classes of such supernetworks, we explicitly derive an analytical representation of their Laplacian spectra. This work is motivated by an application of spectral graph theory in cooperative control of multi-agent networked systems. Specifically, we apply our graph-theoretic results to establish bounds on the speed of convergence and the communication time-delay for solving the average-consensus problem by a supernetwork of clusters of integrator agents.  相似文献   
207.
A general approach to a new generation of spirocyclic molecules – oxa-spirocycles – was developed. The key synthetic step was iodocyclization. More than 150 oxa-spirocyclic compounds were prepared. Incorporation of an oxygen atom into the spirocyclic unit dramatically improved water solubility (by up to 40 times) and lowered lipophilicity. More potent oxa-spirocyclic analogues of antihypertensive drug terazosin were synthesized and studied in vivo.

A general practical approach to a new generation of spirocyclic molecules – oxa-spirocycles – is developed.  相似文献   
208.
Summary: Stoichiometric complexes of biotechnological poly(γ-glutamic) acid and poly(β,L -malic) acid with alkyltrimethylammonium surfactants of long alkyl chains could be readily prepared in aqueous medium. They adopt a biphasic layered structures in which the main chain and the side chain alternate with nanometric periodicity. Alkyl side chains show reversible melting that involves generation of mesophases. Complexes degraded by water by different mechanisms depending on the constitution of the main chain; the polymalic complexes underwent surface erosion whereas the polyglutamic ones degraded in bulk. Erythromycin could be homogenously loaded into the paraffinic subphase of the complexes and delivered upon incubation under physiological conditions in parallel to the hydrolysis of the polymer.  相似文献   
209.
210.
Multiplicity of the liquid-liquid phase transitions in supercooled water, first obtained in computer simulations [Brovchenko et al., J. Chem. Phys. 118, 9473 (2003)], has got strong support from the recent experimental observation of the two phase transitions between amorphous ices [Loerting et al., Phys. Rev. Lett. 96, 025702 (2006)]. These experimental results allow assignment of the four amorphous water phases (I-IV) obtained in simulations to the three kinds of amorphous ices. Water phase I (rho approximately 0.90 gcm(3)) corresponds to the low-density amorphous ice, phase III (rho approximately 1.10 gcm(3)) to the high-density amorphous ice, and phase IV (rho approximately 1.20 gcm(3)) to the very-high-density amorphous ice. Phase II of model water with density rho approximately 1.00 gcm(3) corresponds to the normal-density water. Such assignment is confirmed by the comparison of the structural functions of the amorphous phases of model water and real water. In phases I and II the first and second coordination shells are clearly divided. Phase I consists mainly of the four coordinated tetrahedrally ordered water molecules. Phase II is enriched with molecules, which have tetrahedrally ordered four nearest neighbors and up six molecules in the first coordination shell. Majority of the molecules in phase III still have tetrahedrally ordered four nearest neighbors. Transition from phase III to phase IV is characterized by a noticeable drop of tetrahedral order, and phase IV consists mainly of molecules with highly isotropic angular distribution of the nearest neighbors. Relation between the structures of amorphous water phases, crystalline ices, and liquid water is discussed.  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