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   10941篇
  免费   1497篇
  国内免费   2633篇
化学   10741篇
晶体学   121篇
力学   139篇
综合类   100篇
数学   41篇
物理学   3929篇
  2023年   247篇
  2022年   337篇
  2021年   446篇
  2020年   518篇
  2019年   451篇
  2018年   371篇
  2017年   409篇
  2016年   469篇
  2015年   437篇
  2014年   615篇
  2013年   1084篇
  2012年   797篇
  2011年   720篇
  2010年   534篇
  2009年   702篇
  2008年   661篇
  2007年   743篇
  2006年   738篇
  2005年   618篇
  2004年   626篇
  2003年   513篇
  2002年   438篇
  2001年   324篇
  2000年   301篇
  1999年   256篇
  1998年   207篇
  1997年   215篇
  1996年   173篇
  1995年   177篇
  1994年   136篇
  1993年   139篇
  1992年   123篇
  1991年   86篇
  1990年   59篇
  1989年   59篇
  1988年   70篇
  1987年   39篇
  1986年   30篇
  1985年   24篇
  1984年   20篇
  1983年   16篇
  1982年   22篇
  1981年   12篇
  1980年   17篇
  1979年   18篇
  1978年   17篇
  1977年   14篇
  1976年   18篇
  1975年   5篇
  1973年   5篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Proton acceleration using high-intensity laser pulses, at 1016 W/cm2 was studied irradiating different types of thin metal and plastic targets having 1-micron thickness. The maximization of the proton energy process was investigated optimizing the laser parameters, the irradiation conditions and the target properties. Employing 600–700 J laser pulse energy, a focalization inducing self-focusing effects and using targets with optimized thickness, it was possible to accelerate protons up to energies of above 8 MeV. The time-of-flight diagnostics has allowed to monitor the plasma properties and to control the ion acceleration process.  相似文献   
2.
Metal-sulfur batteries are a promising next-generation energy storage technology, offering high theoretical energy densities with low cost and good sustainability. An active area of research is the development of electrolytes that address unwanted migration of sulfur and intermediate species known as polysulfides during operation of metal-sulfur batteries, a phenomenon that leads to low energy efficiency and short life-spans. A particular class of electrolytes, gel polymer electrolytes, are especially attractive for their ability to repel polysulfides on the basis of structure, electrostatics, and other polymer properties. Herein, within the context of magnesium- and lithium-sulfur batteries, we investigate the impact of gel polymer electrolyte cation solvation capacity, a property related to network dielectric constant and chemistry, on sulfur/polysulfide-polymer interactions, an understudied property-performance relationship. Polymers with lower cation solvation capacity are found to permanently absorb less polysulfide active material, which increases sulfur utilization for Li−S batteries and significantly increases charge efficiency and life-span for Li−S and Mg−S batteries.  相似文献   
3.
采用基于密度泛函理论的第一性原理平面波赝势方法,计算不同数量的锂离子引起的硅材料晶体结构的变化以及在嵌锂过程中形成LixSi(x=1、2、2.4、4.4)合金相的形成能与电子结构.采用LST/QST方法计算过渡态,模拟合金体相中的锂离子迁移过程.计算结果表明,随着嵌锂数量的增加,硅晶胞的体积在不断增大;LixSi合金相的形成能为负值,表明在嵌锂过程中锂离子和硅原子可以自发形成这些合金相,其中Li7Si3合金最容易形成;随着嵌锂量的增加,锂离子在费米能级处s轨道提供的电子数逐渐增加,锂硅合金在费米能级处的电子数量呈增大趋势,表明锂硅合金的导电性越来越优;常温下Li2Si体相中很难直接形成锂离子空位,但锂离子空位的迁移过程很容易发生.  相似文献   
4.
5.
In recent years, individual control of one’s personal environment has been drawing increasing attention due to the growing interest in health care. Wearable devices are especially useful because of their controllability regardless of location. Humidity is one of the inevitable factors in the personal environment as a preventive against infectious diseases. Although atomization devices are commonly used as a method of humidity control, at present, there are no wearable humidity control devices. Vibration of a lithium niobate (LN) device in the thickness mode is a promising piezoelectric method for miniaturization of atomization devices for humidity control. To miniaturize the atomization device, the transducer size needs to be small not so much as to decrease the atomization efficiency. However, the effect of the device area on the atomization efficiency of LN at a size suitable for mounting in wearable devices has not been studied. Here, we conducted an atomization demonstration of LN devices with different sizes to evaluate particle size and atomization efficiency. Furthermore, to reveal the relationship between vibration behavior and atomization efficiency, resonance vibration in the MHz frequency band was evaluated by the finite element method and an impedance analyzer. The results showed that the peak size of water particles atomized by each device was in the range of 3.2 to 4.2 µm, which is smaller than particles produced by typical piezoelectric ceramics. Moreover, the best LN size for efficient atomization was found to be 8 mm × 10 mm among the five LN device sizes used in experiments. From the relationship between vibration behavior and atomization efficiency, the size of the transducer was suggested to affect the vibration mode. The obtained result suggested that the LN device is suitable for small wearable nebulizer devices.  相似文献   
6.
设计、合成了3种新型席夫碱Zn2+荧光探针:水杨醛缩三羟甲基氨基甲烷(L1)、5-氯水杨醛缩三羟甲基氨基甲烷(L2)和4-甲氧基水杨醛缩三羟甲基氨基甲烷(L3),并用1H NMR、13C NMR、元素分析和HRMS进行了表征。光谱分析实验结果表明,相比于探针L1和L3,探针L2对Zn2+具有更好的选择性和灵敏度,检出限为11.96 nmol·L-1,远低于国标GB5749—2006规定的饮水中Zn2+的限量值1.0 mg·L-1(约15 μmol·L-1)。在0~10 μmol·L-1范围内,探针L2的荧光强度与Zn2+浓度可呈良好的线性关系。同时,配合物[Zn (C11H13ClNO4)2](L2-Zn2+)的单晶结构和Job曲线证实探针L2与Zn2+以物质的量之比2∶1配位。另外,探针L2能够对实际水样中的Zn2+进行有效检测。  相似文献   
7.
通过溶剂热反应-水热处理的途径,制备了无定形碳包覆的ZnS纳米晶体(ZnS@C)与还原氧化石墨烯(rGO)复合的ZnS@C/rGO复合材料,并用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和X射线光电子能谱(XPS)对复合材料进行了形貌和微观结构的表征。电化学测试结果表明,与ZnS@C和ZnS/rGO相比,所制备的ZnS@C/rGO复合材料显示了显著增强的电化学储锂性能,在100 mA·g-1电流密度下,其电化学储锂的首次可逆比容量为1 101 mAh·g-1,充放电循环100次后其可逆比容量为1 569 mAh·g-1。在不同电流密度下循环1 200次后,仍保持在2.0 A·g-1电流密度下有1 096 mAh·g-1的可逆比容量,显示了其稳定的长循环性能。  相似文献   
8.
朱振威  邱景义  王莉  曹高萍  何向明  王京  张浩 《电化学》2022,28(12):2219003
锂离子电池已成为解决现代社会储能问题的最佳解决方案之一。然而,电池材料和器件开发都是复杂的多变量问题,传统的依赖研究人员进行实验的试错法在电池性能提升方面遇到了瓶颈。人工智能(AI)具有强大的高速、海量数据处理能力,是上述突破研究瓶颈的最具潜力的技术。其中,机器学习 (ML) 算法在评估多维数据变量和集合之间的组合关联方面的独特优势有望帮助研究人员发现不同因素之间的相互作用规律并阐明材料合成和设备制造的机制。本综述总结了锂离子电池传统研究方法遇到的各种挑战,并详细介绍了人工智能在电池材料研究、电池器件设计与制造、材料与器件表征、电池循环寿命与安全性评估等方面的应用。最重要的是,我们介绍了AI和ML在电池研究中面临的挑战,并讨论了它们应用的缺点和前景。我们相信,未来实验科学家、数学建模专家和AI专家之间更紧密的合作将极大地促进AI和ML方法用以解决传统方法难以克服的电池和材料问题。  相似文献   
9.
In this work, the isolation step in the linear ion trap was performed using different “q values” conditions at a low collision-induced dissociation (CID) energy leading to the parent ion resolution improvements, reasonably due to better ion energy distribution. According to the results, we obtained a greater resolution and mass accuracy operating in both traditional electrospray and low voltage ionization near the q value = 0.778 and with a CID energy of 10%. This effect was evaluated with low-molecular-mass compounds (skatole and arginine). The proposed optimization yielded a superior instrument performance without adding technological complexity to mass spectrometry analyses.  相似文献   
10.
《印度化学会志》2022,99(11):100754
Naked-eye colored chemo dosimeter based on vanilline based conjugated sensor was synthesized and characterized. The main point of this paper is that the solvent also affects on selectivity of metals. Vanilline based conjugate sensor exhibited high selectivity and sensitivity for detection of Ferric ions (Fe+3) in all (both polar and nonpolar) solvents according to absorbance which can be observed by naked eye. The selectivity was more prominent in nonpolar or less polar solvent due to solubility factor of ions and sensor but not for polar. The detection of limit of the synthesized probes was shown up to 0.84 ppm. The dielectric constant of solvents affected on the complex formation of ligand with transition metal ions. A filter paper strip system was used for rapid monitoring of detection by color variation.  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