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   1235篇
  免费   157篇
  国内免费   331篇
化学   1289篇
晶体学   41篇
力学   5篇
综合类   9篇
数学   27篇
物理学   352篇
  2023年   21篇
  2022年   34篇
  2021年   48篇
  2020年   59篇
  2019年   45篇
  2018年   48篇
  2017年   39篇
  2016年   42篇
  2015年   37篇
  2014年   53篇
  2013年   99篇
  2012年   134篇
  2011年   71篇
  2010年   65篇
  2009年   84篇
  2008年   81篇
  2007年   77篇
  2006年   77篇
  2005年   66篇
  2004年   60篇
  2003年   61篇
  2002年   68篇
  2001年   40篇
  2000年   33篇
  1999年   43篇
  1998年   18篇
  1997年   25篇
  1996年   28篇
  1995年   23篇
  1994年   19篇
  1993年   19篇
  1992年   15篇
  1991年   14篇
  1990年   8篇
  1989年   3篇
  1988年   4篇
  1987年   2篇
  1986年   3篇
  1985年   12篇
  1984年   2篇
  1982年   4篇
  1981年   11篇
  1980年   3篇
  1979年   3篇
  1977年   2篇
  1976年   3篇
  1975年   5篇
  1974年   4篇
  1973年   2篇
  1972年   2篇
排序方式: 共有1723条查询结果,搜索用时 46 毫秒
951.
本文综述了各种形貌的纳米Co3O4的制备及其应用。制备纳米Co3O4的方法有很多,包括热分解、水热法、溶剂热法、化学喷雾热分解、化学气相沉积和溶胶-凝胶法。各种形貌的Co3O4被制备,如纳米球、纳米立方体、纳米管、纳米棒、纳米片、纳米纤维和介孔结构。Co3O4是一种重要的磁性P-型半导体,在锂离子电池、超级电容器、电致变色、磁性材料、气体传感器和催化剂等诸多领域有比较广泛的应用。  相似文献   
952.
953.
Arnebinol, a new ansa-type prenylated phenol, was synthesized in 12 steps from geraniol and p-benzoquinone in 5.1 % overall yield.  相似文献   
954.
The cherry red-coloured solid state product obtained by the reaction ofcis-σ diaquo Co (III) triethylene tetramine with ferrocyanide was examined by thermogravimetric, infrared and M?ssbauer techniques. Its electronic spectrum in aqueous medium was interpreted to consist of charge transfer IT transition at 440 nm and a ligand field transition around 330 nm. The kinetics of formation of this 1:1 product in solution was also studied.  相似文献   
955.
The voltammetric determination of cobalt carried out by adsorbing cobalt dimethylglyoxime onto a mercury electrode and subsequently measuring the current for the reduction of the adsorbed species is subject to interference by zinc. If this interference is neglected and the determination carried out by standard additions large errors may result. The interference can be eliminated by adding iminodiacetic acid.  相似文献   
956.
There is growing evidence in recent years that the pristine fullerene may be endowed with strong pro-oxidant capacity to biological samples. In this investigation we tested the hypothesis that water-soluble fullerene-C60 (nano-C60) may interact with ionizing radiation enhancing its antiproliferative effects. The two tumor cell lines with different radiosensitivity B16 and SMMU-7721 were treated by a combination of pristine fullerene and 60Co γ irradiation. We measured cell survival rates, apoptotic characteristics, reactive oxygen species (ROS) production and alteration of cell diameter with or without γ-irradiation. There was reduced survival with B16 and SMMU-7721 cells exposed to nano-C60, with the inhibitory concentrations reducing the viability by 50% to 65 part per billion (ppb) and 150 ppb respectively. For cells exposed to nano-C60 prior to γ-irradiation, damage to cell membranes and increased numbers of apoptotic cells were detected by morphologic Hoechst-staining analysis and Annexin V/propidium iodide double-staining. In cells exposed to nano-C60, there were increased levels of ROS, as measured by fluorescence detection under laser confocal microscopy. Preincubation with non-toxic pristine C60 before γ-ray caused enlargement of cells with increased diameter. The results show that nano-C60 inhibits the growth of tumor cells at certain concentrations and increases the effects of 60Co γ-irradiation, possibly through the elevated production of cellular ROS and the membrane disruption. Data in this study indicates a possible consideration of using C60 as a candidate of sensitization modifier in tumor radiation biology.  相似文献   
957.
We have evaporated Co on the pentagonal surface of an icosahedral Al-Pd-Mn quasicrystal kept at room temperature. For submonolayer Co deposits, five AlCo domains are formed exposing their (1 1 0) faces parallel to the surface and rotated by 72° with respect to each other. The orientational relationship between these domains and the substrate is determined by the optimum matching of the average quasicrystal structure and the CsCl structure with a lattice constant of about 2.88 Å. For further deposition, body-centred cubic Co domains grow epitaxially on the AlCo domains.  相似文献   
958.
We report on the magnetic properties of single crystalline thin films of Zn1−xCoxO (x=0.003–0.14) grown by plasma-assisted molecular beam epitaxy. In order to understand the role of intermediate charge carriers in the magnetic properties of this material two types of films were fabricated, with and without Ga-codoping. Magnetic measurements were made between 2 and 300 K in fields up to 5 T with a Quantum Design SQUID magnetometer. We found that all the tested films exhibit paramagnetic behavior following the Curie–Weiss law, χ=C/(Tθ), with negative Curie–Weiss temperatures and that this behavior holds even under strong n-doping. We show that the magnetization data, M(H), in function of the Co content provide additional evidence in favor of the antiferromagnetic CoCo interaction in this material. We also observe that these data exhibit an ‘easy plane’ magnetic anisotropy for all the studied Co concentrations. Finally, we develop a simple cluster model, in order to describe the magnetic properties of ZnCoO, which is found to be in good agreement with our experiments.  相似文献   
959.
960.
A novel complex [Co(NO3)2(APTY)2H2O] (1) is synthesized based on 1,5-dimethyl-2-phenyl-4-{[(1E)-pyridine-4-ylmethylene]amino}-1,2-dihydro-3H-pyrazol-3-one) antipyrine (APTY) and the structure of complex (1) is characterized via PXRD, SEM, FTIR and X-ray single crystal diffraction technique. It is found that the complex (1) has a good response to Fe3+ ion with colorimetric yellow change. In addition, we demonstrate that the sensing mechanism of complex (1) could is due to the disruption of complex (1) framework and the formation of complex Fe-APTY. The stability, rapid response and low detection limit enable this complex (1) to be a good Fe3+ ion chemical sensor for biological and environmental sensing applications.  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