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   8523篇
  免费   200篇
  国内免费   2篇
化学   5144篇
晶体学   171篇
力学   158篇
数学   1187篇
物理学   2065篇
  2023年   50篇
  2022年   259篇
  2021年   247篇
  2020年   132篇
  2019年   156篇
  2018年   165篇
  2017年   160篇
  2016年   296篇
  2015年   215篇
  2014年   299篇
  2013年   679篇
  2012年   431篇
  2011年   492篇
  2010年   375篇
  2009年   338篇
  2008年   398篇
  2007年   386篇
  2006年   322篇
  2005年   272篇
  2004年   257篇
  2003年   247篇
  2002年   186篇
  2001年   149篇
  2000年   136篇
  1999年   95篇
  1998年   103篇
  1997年   78篇
  1996年   78篇
  1995年   101篇
  1994年   63篇
  1992年   74篇
  1991年   48篇
  1990年   69篇
  1989年   58篇
  1988年   78篇
  1987年   56篇
  1986年   66篇
  1985年   98篇
  1984年   107篇
  1983年   67篇
  1982年   65篇
  1981年   70篇
  1980年   84篇
  1979年   58篇
  1978年   64篇
  1977年   67篇
  1976年   66篇
  1975年   51篇
  1974年   47篇
  1973年   44篇
排序方式: 共有8725条查询结果,搜索用时 15 毫秒
821.
In this note we state the accurate formulas of convexity and concavity constants in Lorentz spaces, correcting the formulas from Kamińska and Parrish (2008) [2].  相似文献   
822.
Ionic liquids with herbicidal anions (named herbicidal ionic liquids—HILs) were synthesized and characterized. The combination of two active chemicals as the [cation][anion] form in a single moiety reduced the number of additional chemicals required per application. HILs ([cation][MCPA]) exhibited higher biological activity than currently used salts of MCPA, and involved pesticides of a multidirectional activity ([plant growth regulator][MCPA]). Acute toxicity of HILs could be controlled by appropriate selection of cation type. These salts had chemical and thermal stability, and showed substantially lower water solubility than starting herbicides, thus reducing soil and groundwater mobility.  相似文献   
823.
In this paper, we present experimental results of target current (TCS) and LEED investigation of well-oriented InSb(1 1 0) and InSb(1 1 1)-A and InSb(1 1 1)-B crystals. TCS results are interpreted in terms of very low electron diffraction (VLEED) and empty band signatures. To examine to which extent the TCS spectra reflect the bulk or surface electronic properties of InSb(1 1 0), thin layers of indium have been evaporated and the corresponding spectrum changes have been investigated.  相似文献   
824.
Sempervirine analogues 13a–c with different E rings have been obtained via inverse electron demand Diels–Alder reactions of 5-acetyl-3-(methylsulfanyl)-1,2,4-triazine with cyclic enamines (formation of D and E rings) followed by Fischer indole synthesis under microwave irradiation on solid support (formation of A and B rings) and subsequent annulation of indole derivatives 10a–c via a directed metallation route (formation of C rings).  相似文献   
825.
Summary Contact angles for water and diiodomethane drops were measured on the surface of thermally and chemically (by Carbowax 20M bonding) modified porous glasses and on the surface of naphthalene, diphenyl and anthracene. Using the obtained results to a modified Young equation, dispersion and nondispersion components of the surface free energy of these glasses and organic substances were calculated. The work of adhesion (WA) for benzene, naphthalene, diphenyl, anthracene, nitrobenzene was estimated and correlated with the capacity factors, (k′) of these substances. On the basis of experimental and calculated data it can be stated that the thermal treatment of porous glasses increases, their hydrophobicity but the Carbowax layer causes hydrophilicity. There is a linear relationship between k′ and WA which can be helpful for predicting retention data of chromatographed substances on the base of surface free energy which can be calculated from contact angle measurements.  相似文献   
826.
For each monothetic unitary group without proper co-compact subgroups, we show the existence of a compact semitopological semigroup (affine) compactification in which the set of idempotents is not closed answering a question of Berglund.  相似文献   
827.
The shadowing corrections to gluon and quark distributions in nuclei in the region of small values ofx are discussed. They are related to parton distributions in a pomeron which are in principle measurable in hard diffractive processes on the nucleon target. Multiple scattering corrections to shadowing are considered in a model dependent way. The perturbative QCD evolution of shadowing is also taken into account. Various possibilities of the partonic content of a pomeron are considered. It is shown in particular that the conventional parametrizations of parton distributions in a pomeron which are based on the assumption that it consists mostly of gluons imply substantial nuclear shadowing in gluon distributions in heavy nuclei. Possible phenomenological implications of shadowing corrections in nuclear parton distributions for various semi-hard processes with nuclear targets are briefly discussed.  相似文献   
828.
ESR studies in the GdT2Sn2 (T = 3d or 4d transition metals) powdered samples were performed. All investigated compounds are bottlenecked systems. The thermal broadening of the linewidth increases when the number of transition metal d electrons decreases. The Δg shift is equal to zero for T = 3d and is negative for T = 4d metals.  相似文献   
829.
830.
Organometallic compounds are widely spread in the human environment sometimes, causing a substantial health risk. Their amphiphilic character enables them to intercalate and penetrate cell membranes, potentially affecting various vital cell functions. Compound adsorption onto the membrane depends on the compound properties, as well as on the membrane composition and state. When adsorbing onto the lipidic surface, phenyltins localize at areas where lipid bilayer organization is compatible with compound spatial requirements. The lipid bilayer is a dynamic and laterally nonuniform structure with complex local and global architecture correlated with a variety of cell functions. The selective binding of a toxic compound to selected membrane areas may, therefore, interfere with some types of cellular process. We present experimental results concerning phenyltin adsorption onto the lipid bilayer surface measured with the fluorescent probe fluorescein‐PE. Model lipid bilayers were formed from lipid mixtures mimicking various plasma membrane regions. The adsorption of Ph3SnCl and P2SnCl2 onto the phosphatidylcholine–cholesterol bilayer was qualitatively different from sphingomyelin–cholesterol. The results presented indicate that phenyltins are likely to accumulate in areas containing phosphatidylcholine, outside of lipid rafts. Copyright © 2004 John Wiley & Sons, Ltd.  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