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   1030篇
  免费   105篇
  国内免费   137篇
化学   803篇
晶体学   19篇
力学   53篇
综合类   7篇
数学   140篇
物理学   250篇
  2024年   6篇
  2023年   21篇
  2022年   38篇
  2021年   37篇
  2020年   55篇
  2019年   45篇
  2018年   26篇
  2017年   38篇
  2016年   47篇
  2015年   50篇
  2014年   53篇
  2013年   77篇
  2012年   83篇
  2011年   101篇
  2010年   65篇
  2009年   57篇
  2008年   50篇
  2007年   44篇
  2006年   39篇
  2005年   51篇
  2004年   32篇
  2003年   28篇
  2002年   18篇
  2001年   18篇
  2000年   17篇
  1999年   17篇
  1998年   15篇
  1997年   21篇
  1996年   18篇
  1995年   22篇
  1994年   13篇
  1993年   9篇
  1992年   16篇
  1991年   4篇
  1990年   6篇
  1989年   4篇
  1988年   3篇
  1987年   4篇
  1986年   3篇
  1985年   2篇
  1984年   1篇
  1983年   2篇
  1982年   3篇
  1979年   1篇
  1976年   2篇
  1974年   4篇
  1973年   1篇
  1971年   2篇
  1957年   2篇
  1945年   1篇
排序方式: 共有1272条查询结果,搜索用时 15 毫秒
1.
Wang  Rong  Li  Xu  Zhou  Youshi  Cao  Shuxuan  Xu  Honghao  Han  Wenjuan  Zhang  Yuxia  Liu  Junhai 《Journal of Russian Laser Research》2022,43(4):476-481
Journal of Russian Laser Research - We demonstrate a passively-mode-locked Pr3+: LuLiF4 laser operated at the 604 nm orange wave-length, using monolayer graphene as a saturable absorber. The...  相似文献   
2.
The discharge of diverse pollutants has led to a complex water environment and posed a huge health threat to humans and animals. Self-propelled micromotors have recently attracted considerable attention for efficient water remediation due to their strong localized mass transfer effect. However, a single functionalized component is difficult to tackle with multiple contaminants and requires to combine different decontamination effects together. Here, we introduced a multifunctional micromotor to implement the adsorption and degradation roles simultaneously by integrating the poly(aspartic acid) (PASP) adsorbent with a MnO2-based catalyst. The as-prepared micromotors are well propelled in contaminated waters by MnO2 catalyzing hydrogen peroxide. In addition, the catalytic ramsdellite MnO2(R-MnO2) inner layer is decorated with Fe2O3 nanoparticles to improve their catalytic performance, contributing to an excellent degradation ability with 90% tetracycline (TC) removal in 50 minutes by enhanced Fenton-like reactions. Combining the attractive adsorption capability of poly (aspartic acid) (PASP), the composite micromotors offer an efficient removal of heavy metal ions in short time. Moreover, the designed micromotors are able to simultaneously remove antibiotic and heavy metals in mixed contaminants circumstance just in single treatment. This multifunctional micromotor with distinctive decontamination ability exhibits a promising prospective in treating multiple pollutants in the future.  相似文献   
3.
本文以二苯基甲酮的KBr压片为标样,在Bruker IFS 120HR付里叶变换红外光谱仪上系统考察了该仪器折一些重要操作参数(光源光栏、切趾函数、扫描速度)对光谱质量(信噪比,分辨率)的影响。从而获得了测样时的优化操作条件。  相似文献   
4.
关新新  赵维君 《分子催化》1992,6(4):303-307
众所周知,铑催化剂是醇类羰基化的有效催化剂,但是铑价格昂贵且对设备有腐蚀性,因此,寻找出对醇类羰基化催化活性好的非贵金属催化剂,对醇类羰化的工业化有十分重要的意义。 本文在温和条件下,合成了四种含有相同配体(Ph_2PPy)不同金属的有机配合物(金属基分别为Ni、Co、Pd、Fe),并探索了它们对乙醇羰基化反应的催化活性。  相似文献   
5.
Absorption and Capture of Methane into Ionic Liquid   总被引:1,自引:0,他引:1       下载免费PDF全文
A reversible storage-release process switched by a temperature difference of 10℃around room temperature can be realized. This fast, recyclable, energy efficient, low cost and green system within a wide range of temperature and pressure is reported here for the first time. The system is believed to open up a new route for the storage and homogeneous utilization of methane.  相似文献   
6.
硅胶担载四核羰基钴催化剂的EXAFS和IR研究   总被引:1,自引:0,他引:1  
本文以透射法EXAFS和IR等手段研究了四核羰基钴金属簇Co_4(CO)_(10)(PPh)_2担载在SiO_2上以后及用于烯烃醛化反应前后的变化,确定了相应的结构参数并探讨了催化活性与结构的关系。  相似文献   
7.
A novel hyperbranched polyester acrylate (HPEA) was synthesized based upon ethylenediamine tetraacetic acid as a “core” molecule, 5‐hydroxyisophthalic acid as an AB2 monomer, and 2‐hydroxyethyl acrylate as an endcapping reagent. The obtained oligomer has an unsaturation concentration of 4.10 mmolC?C g?1 measured by nuclear magnetic resonance and a wide molecular weight distribution of 1.64 measured by gel permeation chromatography. The two‐photon absorption (TPA) photopolymerization of HPEA under the exposure of a Ti : sapphire femtosecond laser with a wavelength of 800 nm was investigated through laser exposure dose‐dependant spatial resolutions of its resins. The TPA photopolymerization thresholds at the range 1.6–4.3 × 107 mJ cm?2, and exposure dose windows at the range 3.4–4.3 for three formulations were determined. A spatial resolution of 0.85 μm was obtained through the TPA photopolymerization of the formulation containing 1 wt% photoinitiator and 0.3 wt% photoinhibitor. A diffraction grating and real three‐dimensional coupled gear wheel created by TPA photopolymerization were described to demonstrate the unique capability of HPEA in microfabrications. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   
8.
Summary A method for preparing selective phases for reversed phase and normal phase liquid chromatography is described. Two different polymeric modified silica gel phases were prepared by simultaneously bonding with -methacryloxypropyltrimethoxysilane as coupling agent. Modification of these polymer phases was achieved by treatment with poly(1-vinyl-2-pyrrolidone) or poly(1-vinylimidazole). By eluting a number of standard mixtures containing polyaromatics and haloaromatics, the selectivity of each phase was evaluated. In reversed phase mode, the partition of sample components between mobile phase and stationary phase was found to be similar for polymer phases and -methacryloxypropylsilyl phase. In normal phase mode, only the poly(1-vinyl-2-pyrrolidone) phase or the poly(1-vinylimidazole) phase could interact electronically with aromatic nuclei.Part 22: see [1]  相似文献   
9.
Summary A flow-through two electrode wall-jet cell with a platinum measuring electrode and a cell volume of 20 nl has been designed and evaluated. It has been used to detect phenols by reversed phase liquid chromatography using short micro bore columns. The linear dynamic range between the measured current and the concentration is greater than 103 (1.5×10–7–5×10–4 mol/l) and the minimum analyzable amount was found to be 10 pg for pyrocatechol. A negligible broadening in the detector permits the use of micro columns down to 0.5 mm internal diameter, packed with 5 m particles, without any substantial distortion of eluted zones.Presented at the 14th International Symposium on Chromatography London, September, 1982  相似文献   
10.
2,2'-Biphenanthroline (2,2'-biphen) formed from 1,10-phenanthroline when a new two-dimensional layered vanadium oxide metal coordination complex, [(2,2'-biphen)Co]V3O8.5, which contains novel 4,8,10-net sheets, was hydrothermally synthesized.  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