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   848篇
  免费   25篇
  国内免费   1篇
化学   679篇
晶体学   13篇
力学   15篇
数学   15篇
物理学   152篇
  2020年   9篇
  2019年   9篇
  2018年   12篇
  2016年   14篇
  2015年   8篇
  2014年   19篇
  2013年   36篇
  2012年   38篇
  2011年   33篇
  2010年   24篇
  2009年   20篇
  2008年   35篇
  2007年   41篇
  2006年   26篇
  2005年   41篇
  2004年   37篇
  2003年   31篇
  2002年   29篇
  2001年   24篇
  2000年   22篇
  1999年   12篇
  1998年   9篇
  1997年   9篇
  1996年   4篇
  1995年   5篇
  1994年   8篇
  1993年   6篇
  1992年   15篇
  1991年   15篇
  1990年   12篇
  1989年   10篇
  1988年   10篇
  1987年   14篇
  1986年   8篇
  1985年   22篇
  1984年   21篇
  1983年   9篇
  1982年   19篇
  1981年   20篇
  1980年   19篇
  1979年   16篇
  1978年   13篇
  1977年   11篇
  1976年   10篇
  1975年   5篇
  1974年   12篇
  1973年   9篇
  1972年   3篇
  1970年   3篇
  1968年   8篇
排序方式: 共有874条查询结果,搜索用时 19 毫秒
61.
Eguchi M  Tsuji Y 《Optics letters》2007,32(15):2112-2114
We present the single-mode single-polarization regime of a circular-hole holey fiber consisting of a core with large elliptical holes. The elliptical holes in the core, which produce large anisotropies, split the fundamental mode into two orthogonally polarized fundamental modes, often referred to as slow and fast modes. This fiber can guide only one polarization state of the fundamental mode when a fundamental space-filling mode index of the cladding region is designed to lie between these indices of the slow and fast modes of the core region. We demonstrate one design example of this fiber and show that the single-polarization regime can be achieved over a wide wavelength range.  相似文献   
62.
There is limited information on the mechanism for platinum oxidation and dissolution in Pt/C cathode catalyst layers of polymer electrolyte fuel cells (PEFCs) under the operating conditions though these issues should be uncovered for the development of next‐generation PEFCs. Pt species in Pt/C cathode catalyst layers are mapped by a XAFS (X‐ray absorption fine structure) method and by a quick‐XAFS(QXAFS) method. Information on the site‐preferential oxidation and leaching of Pt cathode nanoparticles around the cathode boundary and the micro‐crack in degraded PEFCs is provided, which is relevant to the origin and mechanism of PEFC degradation.  相似文献   
63.
A new method for the synthesis of an insulated π-conjugated molecule was developed via the sequential self-inclusion of π-conjugated guest branched permethylated α-cyclodextrin followed by the elongation of the π-conjugated unit. Covering a single π-conjugated wire by an α-cyclodextrin derivatives can suppress conductance fluctuation. The insulated π-conjugated molecules were utilized in the synthesis of highly conductive zigzag- and functionalized-insulated molecular wires.  相似文献   
64.
Although macromolecules on cell surfaces are predominantly targeted and drugged with antibodies, they harbor pockets that are only accessible to small molecules and constitutes a rich subset of binding sites with immense potential diagnostic and therapeutic utility. Compared to antibodies, however, small molecules are disadvantaged by a less confined biodistribution, shorter circulatory half-life, and inability to communicate with the immune system. Presented herein is a method that endows small molecules with the ability to recruit and activate chimeric antigen receptor T cells (CAR-Ts). It is based on a CAR-T platform that uses a chemically programmed antibody fragment (cp-Fab) as on/off switch. In proof-of-concept studies, this cp-Fab/CAR-T system targeting folate binding proteins on the cell surface mediated potent and specific eradication of folate-receptor-expressing cancer cells in vitro and in vivo.  相似文献   
65.
66.
67.
ABSTRACT

We present a new fabrication approach to achieve a high birefringence film by means of photopolymerization based on an alkylthio-containing rod-like liquid crystalline molecule exhibiting large temperature dependence of birefringence. We designed a new reactive mesogen having alkylthio linkages (BPM–S). It was found that BPM–S had a larger increment of birefringence with decreasing temperature, relative to commercially available alkoxy analog LC242. This result could be thought to be due to enhanced intermolecular attractive interaction for an alkylthio mesogen implied by the proximity of laterally neighboring molecules and cybotactic nematic tendency based on wide-angle X-ray measurement. The uniaxially-aligned photo-polymerized film for BPM–S showed higher birefringence than that for LC 242.  相似文献   
68.
69.
The crystallization of 2,4,6-triethynyl-1,3,5-triazine (2) leads to a pi-stacked layered structure of a C(sp)-H...N hydrogen-bonded unique hexagonal network structure, which may be regarded as a supramolecular analogue of a hitherto unknown graphyne network: in-plane intermolecular interactions are short and linear H...N contacts (2.31 and 2.34 A) and the interlayer separation is 3.23 A.  相似文献   
70.
The synthesis of MoVNbTe(Sb)O(x)() composite oxide catalysts based on the self-organization of polyoxometalates (POMs) was investigated. The catalysts which were synthesized via reduction of POMs by using reducing agents under mild conditions and/followed by calcination in an O(2)-excluded atmosphere which superior performance for propane (amm)oxidation. It was suggested that the metastable phase formed at an elevated temperature with a specific oxidation state corresponds to the catalytic activity.  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