全文获取类型
| 收费全文 | 4914篇 |
| 免费 | 465篇 |
| 国内免费 | 427篇 |
专业分类
| 化学 | 2382篇 |
| 晶体学 | 35篇 |
| 力学 | 238篇 |
| 综合类 | 47篇 |
| 数学 | 320篇 |
| 物理学 | 1253篇 |
| 综合类 | 1531篇 |
出版年
| 2025年 | 9篇 |
| 2024年 | 65篇 |
| 2023年 | 89篇 |
| 2022年 | 143篇 |
| 2021年 | 170篇 |
| 2020年 | 179篇 |
| 2019年 | 142篇 |
| 2018年 | 133篇 |
| 2017年 | 150篇 |
| 2016年 | 171篇 |
| 2015年 | 156篇 |
| 2014年 | 238篇 |
| 2013年 | 271篇 |
| 2012年 | 272篇 |
| 2011年 | 352篇 |
| 2010年 | 258篇 |
| 2009年 | 259篇 |
| 2008年 | 293篇 |
| 2007年 | 255篇 |
| 2006年 | 214篇 |
| 2005年 | 175篇 |
| 2004年 | 150篇 |
| 2003年 | 101篇 |
| 2002年 | 113篇 |
| 2001年 | 109篇 |
| 2000年 | 91篇 |
| 1999年 | 128篇 |
| 1998年 | 109篇 |
| 1997年 | 119篇 |
| 1996年 | 120篇 |
| 1995年 | 111篇 |
| 1994年 | 90篇 |
| 1993年 | 89篇 |
| 1992年 | 84篇 |
| 1991年 | 67篇 |
| 1990年 | 68篇 |
| 1989年 | 60篇 |
| 1988年 | 46篇 |
| 1987年 | 42篇 |
| 1986年 | 32篇 |
| 1985年 | 18篇 |
| 1984年 | 9篇 |
| 1983年 | 12篇 |
| 1982年 | 11篇 |
| 1981年 | 5篇 |
| 1980年 | 7篇 |
| 1979年 | 5篇 |
| 1977年 | 3篇 |
| 1975年 | 2篇 |
| 1957年 | 4篇 |
排序方式： 共有5806条查询结果，搜索用时 0 毫秒
21.
实验获得了激光照射红细胞悬液的荧光光谱,并分别监测不同荧光峰值波长处强度随时间的衰变过程,测试了其相应的荧光寿命.结果表明,在波长为407 nm的激光照射下,红细胞悬液向外发射中心波长分别位于596,628,692 nm的荧光光谱,各荧光峰对应衰变过程的平均荧光寿命分别为1.97,13.31,14.58 ns.利用荧光强度和吸收率的加和性表示了混合物的总吸收率和总荧光发射强度,通过理论计算获得了红细胞悬液中锌卟啉、原卟啉和其他游离物参与荧光发射的相对含量和相对强度在不同荧光峰位的变化关系,进一步解释了不同峰位处荧光发射强度和平均荧光寿命的变化原因. 相似文献
22.
含油脂的食品中常需加入一定量的抗氧化剂,以防止在储存或运输过程中变质,但食用过量的抗氧化剂会影响人体的健康,造成不良后果,因此对食品中的抗氧化剂含量进行分析测定是有实际意义的,本文采用模糊线性规划法解析抗氧化剂的重叠紫外吸收光谱,实现了对食品抗氧化剂多组分,包括丁基羟基茴香醚（ＢＨＡ）,二丁基羟基甲苯（ＢＨＴ）及没食子酸丙酯（ＰＧ）的同时测定。 相似文献
23.
采用高温固态反应和均衡热压方法相结合,我们制备了一系列Gd掺杂的Chevrel相GdxPb1-xMo6S8超导样品.为了研究掺入的磁性Gd3+离子对于磁通线的钉扎作用和对临界电流及其它性质的影响,我们系统地测量了样品的电阻率,热电势,比热和临界电流密度.同时,我们计算了磁性Gd3+离子与磁通线之间的相互作用和这种作用可能导致的磁通钉扎及对临界电流的影响,并与实验结果进行了比较.结果显示除非Gd3+离子的分布是非常不均匀的,Gd3+离子所引起的钉扎是不重要的.另一方面,热电势和电阻率等输运性质及比热的结果显示由于Gd3+取代了Pb2+使载流子浓度降低了.载流子浓度的降低进而引起其它超导参数如热力学临界场Bc的变化,导致钉扎势的减小,最终降低了临界电流. 相似文献
24.
多传感器远距离目标跟踪精度分析 总被引：2，自引：0，他引：2
该文主要研究了非线性系统中多传感器远距离目标跟踪问题,提出了分布的转换坐标卡尔曼滤波算法,给出了当多传感器不在同一位置时融合中心的状态估计组合公式。 相似文献
25.
Minčenko V. V. Ničiporenko S. P. Miščenko S. F. Škljarskaja I. N. 《Colloid and polymer science》1976,254(8):754-754
Ohne Zusammenfassung 相似文献
26.
Ｓｏｌｉｄ－ｓｔａｔｅＳｙｎｔｈｅｓｉｓａｔＬｏｗ－ｈｅａｔｉｎｇＴｅｍｐｅｒａｔｕｒｅａｎｄＣｒｙｓｔａｌＳｔｒｕｃｔｕｒｅｏｆａＤｉｎｕｃｌｅａｒＭｏｌｙｂｄｅｎｕｍＣｏｍｐｌｅｘｗｉｔｈＯｘａｌａｔｅＬｉｇａｎｄ［Ｂｕ_４Ｎ］_２［Ｍｏ_２Ｏ_２（... 相似文献
27.
Yi Han Zibo Xue Dr. Guangwu Li Dr. Yanwei Gu Dr. Yong Ni Dr. Shaoqiang Dong Prof. Chunyan Chi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(23):9111-9116
Incorporation of a non-hexagonal ring into a nanographene framework can lead to new electronic properties. During the attempted synthesis of naphthalene-bridged double [6]helicene and heptagon-containing nanographene by the Scholl reaction, an unexpected azulene-embedded nanographene and its triflyloxylated product were obtained, as confirmed by X-ray crystallographic analysis and 2D NMR spectroscopy. A 5/7/7/5 ring-fused substructure containing two formal azulene units is formed, but only one of them shows an azulene-like electronic structure. The formation of this unique structure is explained by arenium ion mediated 1,2-phenyl migration and a naphthalene to azulene rearrangement reaction according to an in-silico study. This report represents the first experimental example of the thermodynamically unfavorable naphthalene to azulene rearrangement and may lead to new azulene-based molecular materials. 相似文献
28.
Prof. Jen-Shyang Ni Tianliang Min Yaxi Li Menglei Zha Dr. Pengfei Zhang Prof. Chun Loong Ho Prof. Kai Li 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(25):10265-10271
Planar luminogens have encountered difficulties in overcoming intrinsic aggregation-caused emission quenching by intermolecular π-π stacking interactions. Although excited-state double-bond reorganization (ESDBR) can guide us on designing planar aggregation-induced emission (AIE) luminogens (AIEgens), its mechanism has yet been elucidated. Major challenges in the field include methods to efficiently restrict ESDBR and enhance AIE performance without using bulky substituents (e.g., tetraphenylethylene and triphenylamine). In this study, we rationally developed fluoro-substituent AIEgens with stronger intermolecular H-bonding interaction for restricted molecular motions and increased crystal density, leading to decreased nonradiative decay rate by one order of magnitude. The adjusted ESDBR properties also show a corresponding response to variation in viscosity. Furthermore, their aggregation-induced reactive oxygen species (ROS) generations have been discovered. The application of such planar AIEgen in treating multidrug-resistant bacteria has been demonstrated in a mouse model. The relationship between ROS generation and distinct E/Z-configurational stacking behaviors have been further understood, providing a design principle for synthesizing planar AIEgen-based photosensitizers. 相似文献
29.
Yuni RETNANINGTYAS Ganden SUPRIYANTO Ni NYOMAN TRI PUSPANINGSIH Roedi IRAWAN Siswandono SISWODIHARDJO 《Turkish Journal of Chemistry》2020,44(5):1265
In this research, molecular imprinting polymers (MIPs) for D-arabinitol were synthesized using a bulk polymerization method through a noncovalent approach. The MIPs were prepared by using D-arabinitol as a template, acrylamide as a functional monomer, ethylene glycol dimethacrylateas cross-linker, benzoyl peroxide as an initiator and dimethyl sulfoxideas a porogen. MIPS was synthesized in several formulas with a different molar ratio of template to functional monomers and cross-linker. Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) were used to characterize the MIPs produced. A batch rebinding assay was used to test the binding efficiency of each formula. Batch rebinding test results revealed that MIPsF3 with a molar ratio of the template: monomer and crosslinker ratio respectively (1: 4: 25) had the highest binding capacity at 1.56 mgg -1 . The results of isotherm adsorption showed that the MIPs produced followed the Freundlich equation with an R-value of 0.97. The MIPs produced was also selective toward its isomeric compounds (i.e. L-arabinitol, adonitol, xylitol, and glucose). The extraction efficiency of the MIPs against D-arabinitol was 88.98%. 相似文献
30.
Yan-Cong Chen Yan Meng Yan-Jie Dong Xiao-Wei Song Guo-Zhang Huang Chuan-Lei Zhang Zhao-Ping Ni Jakub Nava&#x;ík Ond&#x;ej Malina Radek Zbo&#x;il Ming-Liang Tong 《Chemical science》2020,11(12):3281
Among responsive multistable materials, spin crossover (SCO) systems are of particular interest for stabilizing multiple spin states with various stimulus inputs and physical outputs. Here, in a 2D Hofmann-type coordination polymer, [Fe(isoq)2{Au(CN)2}2] (isoq = isoquinoline), a medium-temperature annealing process is introduced after light/temperature stimulation, which accesses the hidden multistability of the spin state. With the combined effort of magnetic, crystallographic and Mössbauer spectral investigation, these distinct spin states are identified and the light- and temperature-assisted transition pathways are clarified. Such excitation-relaxation and trapping-relaxation joint mechanisms, as ingenious interplays between the kinetic and thermodynamic effects, uncover hidden possibilities for the discovery of multistable materials and the development of multistate intelligent devices.Two new two-stage manipulation protocols, namely light- and temperature-assisted spin state annealing (LASSA/TASSA), are applied to a spin crossover coordination polymer, [Fe(isoq)2{Au(CN)2}2], revealing the hidden multistability of spin states. 相似文献