全文获取类型
收费全文 | 14207篇 |
免费 | 2662篇 |
国内免费 | 2491篇 |
专业分类
化学 | 11469篇 |
晶体学 | 192篇 |
力学 | 631篇 |
综合类 | 256篇 |
数学 | 1569篇 |
物理学 | 5243篇 |
出版年
2024年 | 19篇 |
2023年 | 259篇 |
2022年 | 318篇 |
2021年 | 399篇 |
2020年 | 589篇 |
2019年 | 623篇 |
2018年 | 512篇 |
2017年 | 492篇 |
2016年 | 757篇 |
2015年 | 793篇 |
2014年 | 853篇 |
2013年 | 1138篇 |
2012年 | 1280篇 |
2011年 | 1383篇 |
2010年 | 990篇 |
2009年 | 1005篇 |
2008年 | 1070篇 |
2007年 | 945篇 |
2006年 | 929篇 |
2005年 | 837篇 |
2004年 | 660篇 |
2003年 | 570篇 |
2002年 | 583篇 |
2001年 | 442篇 |
2000年 | 393篇 |
1999年 | 304篇 |
1998年 | 193篇 |
1997年 | 174篇 |
1996年 | 164篇 |
1995年 | 133篇 |
1994年 | 114篇 |
1993年 | 97篇 |
1992年 | 67篇 |
1991年 | 49篇 |
1990年 | 42篇 |
1989年 | 35篇 |
1988年 | 23篇 |
1987年 | 26篇 |
1986年 | 23篇 |
1985年 | 19篇 |
1984年 | 8篇 |
1983年 | 9篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1957年 | 5篇 |
1936年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
991.
992.
The unresolved debate on the active reaction interface of electrochemical oxidation of lithium peroxide (Li2O2) prevents rational electrode and catalyst design for lithium‐oxygen (Li‐O2) batteries. The reaction interface is studied by using isotope‐labeling techniques combined with time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) and on‐line electrochemical mass spectroscopy (OEMS) under practical cell operation conditions. Isotopically labelled microsized Li2O2 particles with an Li216O2/electrode interface and an Li218O2/electrolyte interface were fabricated. Upon oxidation, 18O2 was evolved for the first quarter of the charge capacity followed by 16O2. These observations unambiguously demonstrate that oxygen loss starts from the Li2O2/electrolyte interface instead of the Li2O2/electrode interface. The Li2O2 particles are in continuous contact with the catalyst/electrode, explaining why the solid catalyst is effective in oxidizing solid Li2O2 without losing contact. 相似文献
993.
Mahmoud Elsayed Hafez Hui Ma Wei Ma Yi‐Tao Long 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(19):6393-6398
Gold nanoparticles (AuNPs) have been demonstrated to serve as effective nanomaterial‐based enzyme mimetics (nanozymes) for a number of enzymatic reactions under mild conditions. The intrinsic glucose oxidase and peroxidase activities of single AuNPs and Ag–Au nanohybrids, respectively, were investigated by single NP collision electrochemical measurements. A significantly high turnover number of nanozymes was obtained from individual catalytic events compared with the results from the classical, ensemble‐averaged measurements. The unusual enhancement of catalytic activity of single nanozymes is believed to originate from the high accessible surface area of monodispersed NPs and the high activities of carbon‐supported NPs during single‐particle collision at a carbon ultramicroelectrode. This work introduces a new method for the precise characterization of the intrinsic catalytic activities of nanozymes, giving further insights to the design of high‐efficiency nanomaterial catalysts. 相似文献
994.
Wan Chengwei Li Kai Shen Sichen Gibson J. J. Ji Kaifang Yi Peng Yu Zhongbo 《Journal of Radioanalytical and Nuclear Chemistry》2019,322(2):561-578
Journal of Radioanalytical and Nuclear Chemistry - On the Qinghai-Tibet Plateau, permafrost degradation and associated release of permafrost meltwater has undoubtedly modified the annual and... 相似文献
995.
以L-苯丙氨酸衍生物(L-18Phe6PyBr)的自组装体为模板, 在0.30 mmol/L的浓度下, 研究了pH值、 老化时间和四乙氧基硅烷(TEOS)浓度对二氧化硅形貌的影响. 通过扫描电子显微镜和透射电子显微镜对样品进行表征. 结果表明, 在pH=10.01的条件下可以得到左手扭转的纳米带, 而pH=7.15和12.34时, 得到直线的纳米带. 遵循动态模板的方法, 老化时间的延长有利于直线纳米带的形成. 随着TEOS和L-18Phe6PyBr的质量比由2:1增加到15:1, 扭转纳米带的宽度增加, 螺距变长. 通过煅烧除去有机模板后, 得到带状二氧化硅纳米管. 将TEOS与L-18Phe6PyBr质量比为2:1制备得到的二氧化硅作为气相色谱固定相, 涂渍到毛细管色谱柱中进行对映体拆分. 结果表明, 该气相色谱柱可以拆分1-苯基-1-丙醇、 1-(4-氯苯基)乙醇和2-甲基戊酸3种外消旋化合物, 手性超分子印迹是拆分对映体的主要作用力. 对二氧化硅低聚物与小分子凝胶的协同组装行为以及将无机材料作为手性固定相有了一个更好的认识. 相似文献
996.
以K2PdCl4/K2Ni(CN)4为前驱体制备了具有凝胶特性的氰胶(Cyanogels), 利用硼氢化钠还原氰胶得到三维多孔珊瑚状PdNi合金前驱体, 在此基础上通过原位Galvanic置换反应, 制备得到内核为PdNi合金、 表面具有不同厚度Au层的三维多孔PdNi@Au催化剂. X射线衍射(XRD)分析和透射电子显微镜(TEM)观测结果显示, 该三维网状结构由粒径约7 nm的纳米颗粒相互连接形成; 能量分散光谱(EDX)线性扫描和元素分布(Mapping)分析显示该催化剂具有典型的核壳结构. 电化学测试结果表明, 表面Au层的厚度影响PdNi@Au催化剂的性能, 当Au的含量(摩尔分数)为5.6%时, 催化剂显示出对甲酸最佳的电催化活性, 对甲酸电催化氧化的峰电流密度达到商业化铂黑催化剂的7.2倍. 相似文献
997.
Extending Seventh-Order Dissipative Compact Scheme Satisfying Geometric Conservation Law to Large Eddy Simulation on Curvilinear Grids 下载免费PDF全文
Yi Jiang Meiliang Mao Xiaogang Deng & Huayong Liu 《advances in applied mathematics and mechanics.》2015,7(4):407-429
Seventh-order hybrid cell-edge and cell-node dissipative compact scheme
(HDCS-E8T7) is extended to a new implicit large eddy simulation named HILES on
stretched and curvilinear meshes. Although the conception of HILES is similar to that
of monotone integrated LES (MILES), i.e., truncation error of the discretization scheme
itself is employed to model the effects of unresolved scales, HDCS-E8T7 is a new high-order
finite difference scheme, which can eliminate the surface conservation law (SCL)
errors and has inherent dissipation. The capability of HILES is tested by solving several
benchmark cases. In the case of flow past a circular cylinder, the solutions of HILES
fulfilling the SCL have good agreement with the corresponding experiment data, however,
the flow field is gradually contaminated when the SCL error is enlarged. With the
help of fulling the SCL, ability of HILES for handling complex geometry has been enhanced.
The numerical solutions of flow over delta wing demonstrate the potential of
HILES in simulating turbulent flow on complex configuration. 相似文献
998.
In current paper we study the so-called “complete condensation” of zero range process on the fitness network. It is found that under the high temperature limit, the condensation behavior on the fitness model converges to that of the scale-free network, as expected. However, at some temperatures below the critical temprature of Bose- Einstein condensate phase on the fitness network, the complete condensation occurs as well for some values of δ> δc, which is impossible on scale-free network according to the criterion. 相似文献
999.
XIAO Yi CHEN Fang ZHU Xixi QIN Hongling HUANG Hongmei ZHANG Youyu YIN Dulin HE Xiaoxiao WANG Kemin 《高等学校化学研究》2015,31(6):899-903
New lanthanide metal-organic framework(MOF) nano/microrods, [C4mim]Cl-Eu-MOF, [C8mim]Cl-Eu- MOF and [C12mim]Cl-Eu-MOF, were conveniently synthesized via an ionic liquid-assisted hydrothermal method and characterized by means of powder X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR), thermogravimetric analysis(TG) and transmission electron microscopy(TEM). The obtained nano/microrods with low surface areas were efficient for the removal of Congo red(CR) from aqueous solutions. Under the optimum conditions, [C4mim]Cl-Eu-MOF with a specific surface area of 5.1 m2/g exhibited an ultrahigh adsorption capacity of 2606 mg/g toward CR. Notably, the adsorption efficiency of [C4mim]Cl-Eu-MOF for CR via nano/microscale stacking can be directly demonstrated by TEM. In-depth understanding of CR removal by [C4mim]Cl-Eu-MOF nano/microrods was also supported by FTIR, Raman spectroscopy and zeta potential analyses. 相似文献
1000.
针对高稳定度遥感器在轨相对定标监测系统关键技术进行研究,阐述了工作原理和关键技术。研制了基于可见/短波红外双波段陷阱结构的高稳定度定标探测器组件,通过选择高灵敏度单元可见和短波红外光电探测器,一方面使探测器组件工作在线性更好、暗电流更低的零偏置光伏电路模式,另一方面使探测器组合成为复合型陷阱光机探测模式,并在模拟前放电路和数据采集环节进行了关键参数设计,完成了星载定标辐射源输出辐射的高稳定度相对定标监测系统设计。通过实验室内积分球以及国家计量技术机构提供的标准灯的辐射测试结果表明,系统获取的码值相对标准方差达到0.030%~0.046%(可见通道)和0.040%~0.059%(短波红外通道),实现了相对定标系统的高稳定度监测,为未来遥感器在轨相对定标提供一种优良的解决方案。 相似文献