全文获取类型
收费全文 | 5054篇 |
免费 | 785篇 |
国内免费 | 540篇 |
专业分类
化学 | 2648篇 |
晶体学 | 54篇 |
力学 | 296篇 |
综合类 | 17篇 |
数学 | 405篇 |
物理学 | 1677篇 |
无线电 | 1282篇 |
出版年
2024年 | 27篇 |
2023年 | 159篇 |
2022年 | 171篇 |
2021年 | 232篇 |
2020年 | 207篇 |
2019年 | 194篇 |
2018年 | 179篇 |
2017年 | 156篇 |
2016年 | 246篇 |
2015年 | 237篇 |
2014年 | 299篇 |
2013年 | 371篇 |
2012年 | 456篇 |
2011年 | 442篇 |
2010年 | 306篇 |
2009年 | 312篇 |
2008年 | 322篇 |
2007年 | 300篇 |
2006年 | 287篇 |
2005年 | 231篇 |
2004年 | 160篇 |
2003年 | 137篇 |
2002年 | 114篇 |
2001年 | 101篇 |
2000年 | 107篇 |
1999年 | 76篇 |
1998年 | 83篇 |
1997年 | 70篇 |
1996年 | 67篇 |
1995年 | 75篇 |
1994年 | 38篇 |
1993年 | 47篇 |
1992年 | 47篇 |
1991年 | 30篇 |
1990年 | 27篇 |
1989年 | 17篇 |
1988年 | 11篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 10篇 |
1984年 | 1篇 |
1983年 | 6篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有6379条查询结果,搜索用时 17 毫秒
201.
Zhu Hai-Liang Huang Pei Duan Chun-Ying Zheng Li-Min Liu Yong-Jiang Wu Mei-Fang Tang Wen-Xia 《Transition Metal Chemistry》1999,24(4):380-383
An azide-bridged polymeric cationic chain complex, [LCu2(N3)2]n(ClO4)2n
·n(H2O)**, where L=the dinucleating macrocyclic ligand bis-p-xylylBISDIEN, has been prepared and characterized by x-ray crystallography, u.v.-vis and i.r. spectra, and by magnetic measurements. The structure consists of cationic azide-bridged [LCu2(N3)2]2+ (unit) chains, non-coordinated perchlorate anions and crystallized water molecules. The azide anion is bound to two copper atoms in neighboring units with an end-to-end bridging mode. In each unit, the copper atoms have a different coordination geometry; Cu(1) is a four-coordinated, distorted square-planar geometry, whereas Cu(2) is a five-coordinated, distorted square-pyramid. The electronic spectra of the title complex differ in anhydrous and in aqueous MeCN solutions, indicating that dissociation and solvation occur in aqueous solutions. The characteristic i.r. absorptions of azides and perchlorates are described. Magnetic moments vary from 2.05 (B.M.) at 300K to2.01 (B.M.) at 80K, which suggests that very weak interactions exist between the metals. 相似文献
202.
以水玻璃、三氯化镓、1,6-己二胺和水为原料,合成了SiO2/Ga2O3为60-38间的含镓ZSM-5型沸石.X-射线谱图表明含镓ZSM-5型沸石与硅铝ZSM-5型沸石相似,电子探针的分析结果表明镓原子进入了沸石骨架。 相似文献
203.
二氧化锰(MnO2)材料具有比容量大、电极电位高、储量丰富以及价格低廉等优势,成为水系锌电池正极最受关注的一类材料,然而其仍然存在着结构稳定性差和电化学储存机理复杂的问题。因此,我们通过两步合成法制备了一种花苞状结构的MnO2负载在Ti3C2Tx表面形成Ti3C2Tx/MnO2复合材料,通过X射线粉末衍射(XRD)、X射线光电子能谱(XPS)、透射电子显微镜(TEM)和高分辨透射电子显微镜(HRTEM)对复合样品的结构、成分和形貌进行表征。通过将Ti3C2Tx/MnO2复合材料作为正极,与锌负极匹配组装成水系锌电池,研究了其分别在2 mol·L-1 ZnSO4、2 mol·L-1 ZnSO4+0.1 mol·L-1 MnSO4、30 mol·L-1三氟甲基磺酸四乙基铵(TEAOTf)+1 mol·L-1三氟甲烷磺酸锌(ZnOTf)和3 mol·L-1 ZnOTf四种电解液中的电化学性能。结果表明,Ti3C2Tx/MnO2在2 mol·L-1 ZnSO4中的比容量较高,但循环稳定性很差。将TEAOTf盐和ZnOTf盐共溶于水中,设计了一种新型的含惰性阳离子的超高浓度盐包水电解液(30 mol·L-1 TEAOTf+1 mol·L-1 ZnOTf),不仅提高了Ti3C2Tx/MnO2材料的可逆性,而且有效抑制了电极材料在循环过程中的溶解。 相似文献
204.
205.
206.
圆偏振发光主要是指手性发光体系激发态的性质。由于其在信息加密、高分辨3D显示和智能传感器等领域的潜在应用而备受关注。圆偏振光除了可以通过物理方法获得,即使用线偏振片和四分之一波片的组合,还可以直接从具有光致发光或电致发光性质的手性材料中获得。目前研究者们已经开发了多种圆偏振发光材料,主要包括手性有机分子、手性金属配合物等小分子发光体系以及手性超分子组装体等复合体系。通过将手性组分与响应性功能基团结合而构筑的响应性自组装发光体系对实现智能圆偏振发光材料的发展起着重要作用。在这篇文章里,我们对手性超分子自组装发光体系对各种外界刺激的响应性能进行了总结和归纳,如光照、pH值、溶剂、温度、金属离子等。本综述通过对各种外部刺激对手性组装体激发态性能影响的总结和讨论,旨在进一步推动智能圆偏振发光材料在多学科领域的应用。 相似文献
207.
Man Duan Dongmei Han Nan Gao Wenbin Shen Kun Chang Xinyu Wang Jianshi Du 《Molecules (Basel, Switzerland)》2022,27(5)
Porous organic polymers have an open architecture, excellent stability, and tunable structural components, revealing great application potential in the field of fluorescence imaging, but this part of the research is still in its infancy. In this study, we aimed to tailor the physical and chemical characteristics of indocyanine green using sulfonic acid groups and conjugated fragments, and prepared amino-grafted porous polymers. The resulting material had excellent solvent and thermal stability, and possessed a relatively large pore structure with a size of 3.4 nm. Based on the synergistic effect of electrostatic bonding and π–π interactions, the fluorescent chromogenic agent, indocyanine green, was tightly incorporated into the pore cavity of POP solids through a one-step immersion method. Accordingly, the fluorescent chromogenic POP demonstrated excellent imaging capabilities in biological experiments. This preparation of fluorescent chromogenic porous organic polymer illustrates a promising application of POP-based solids in both fluorescence imaging and biomedicine applications. 相似文献
208.
本文用热分析、元素分析及溶液吸附三种方法,对不同浓度的γ-GOPS水溶液与硅球表面接枝键合相的系列样品进行接枝度的测定。认为热分析方法是测定硅胶表面接枝度的适用方法。元素分析误差大,数值偏高。溶液吸附法只能作为比较对硅胶表面接枝量大小的相对方法。 相似文献
209.
Li-Wei Wang Songwei Jiang Ying-Hui Yuan Jilong Duan Nian-Dong Mao Zi Hui Renren Bai Tian Xie Xiang-Yang Ye 《Molecules (Basel, Switzerland)》2022,27(8)
As one of the key phosphatidylinositol 3-kinase-related kinases (PIKKs) family members, ataxia telangiectasia and RAD3-related protein kinase (ATR) is crucial in maintaining mammalian cell genomic integrity in DNA damage response (DDR) and repair pathways. Dysregulation of ATR has been found across different cancer types. In recent years, the inhibition of ATR has been proven to be effective in cancer therapy in preclinical and clinical studies. Importantly, tumor-specific alterations such as ATM loss and Cyclin E1 (CCNE1) amplification are more sensitive to ATR inhibition and are being exploited in synthetic lethality (SL) strategy. Besides SL, synergistic anticancer effects involving ATRi have been reported in an increasing number in recent years. This review focuses on the recent advances in different forms of synergistic antitumor effects, summarizes the pharmacological benefits and ongoing clinical trials behind the biological mechanism, and provides perspectives for future challenges and opportunities. The hope is to draw awareness to the community that targeting ATR should have great potential in developing effective anticancer medicines. 相似文献
210.
Cycloparaphenylene (CPP) shows modulated photophysical and electronic properties due to its strained structure and radially oriented π-electron system. Incorporation of CPP into metal-organic frameworks (MOFs) could transfer its extensive properties in solution to porous solids. Moreover, with the unique arrangement of the macrocycles and their interactions with the framework, emerging characteristics are anticipated. As an example of “robust dynamics”, we synthesized the first MOF structure (FDM-1001) with CPP precisely anchored to the ordered framework by employing a [8]CPP-containing linear dicarboxylate linker. Metric relationship between the dynamic macrocycles and the robust backbone creates ideal π-π interactions between them, which leads to an essentially directional arrangement of [8]CPP in the three-dimensional space. Furthermore, the MOF with [8]CPP could be successfully oxidized to generate an infinite array of radicals that show enhanced air stability compared to its molecular analogue. 相似文献