全文获取类型
收费全文 | 1645篇 |
免费 | 357篇 |
国内免费 | 319篇 |
专业分类
化学 | 1419篇 |
晶体学 | 32篇 |
力学 | 85篇 |
综合类 | 21篇 |
数学 | 92篇 |
物理学 | 672篇 |
出版年
2024年 | 3篇 |
2023年 | 30篇 |
2022年 | 64篇 |
2021年 | 66篇 |
2020年 | 71篇 |
2019年 | 76篇 |
2018年 | 50篇 |
2017年 | 66篇 |
2016年 | 84篇 |
2015年 | 91篇 |
2014年 | 131篇 |
2013年 | 121篇 |
2012年 | 170篇 |
2011年 | 182篇 |
2010年 | 132篇 |
2009年 | 148篇 |
2008年 | 126篇 |
2007年 | 84篇 |
2006年 | 94篇 |
2005年 | 69篇 |
2004年 | 58篇 |
2003年 | 52篇 |
2002年 | 52篇 |
2001年 | 32篇 |
2000年 | 25篇 |
1999年 | 45篇 |
1998年 | 32篇 |
1997年 | 25篇 |
1996年 | 23篇 |
1995年 | 20篇 |
1994年 | 17篇 |
1993年 | 13篇 |
1992年 | 8篇 |
1991年 | 5篇 |
1990年 | 14篇 |
1989年 | 12篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1936年 | 2篇 |
排序方式: 共有2321条查询结果,搜索用时 15 毫秒
81.
以二茂铁、二甲苯为前驱体,石英为衬底,在850 oC的管式炉内采用化学气相沉积法制备出了定向碳纳米管阵列. 高分辨透射电子显微镜和拉曼光谱的结果表明:碳纳米管阵列具有良好的定向性和多壁管状结构,石墨化程度高,并且只在表面存在少量单壁碳纳米管.定向多壁碳纳米管阵列的生长模式为“底部”生长模式,即在生长的初期,当催化剂颗粒较小时,析出的碳原子生成了单壁碳纳米管或与其性质类似的多壁碳纳米管(一般层数小于5层);催化剂颗粒逐渐长大后,大量的碳原子析出后生成了普通的多壁碳纳米管,从而形成了单壁碳纳米管只存在于碳纳米管阵列膜表面和多层碳纳米管膜表面与界面的现象. 相似文献
82.
Li Yong-Feng Zhang Jie-Qiu Qu Shao-Bo Wang Jia-Fu Zheng Lin Zhou Hang Xu Zhuo Zhang An-Xue 《中国物理 B》2015,24(1):14202-014202
In this paper,we show that circular polarization-keeping reflection can be achieved using reflective metasurfaces.The underlying physical mechanism of the polarization-keeping reflection is analyzed using a reflection matrix.A wideband circular polarization-keeping reflector is demonstrated using N-shaped resonators.Both the simulation and experiment results show that the polarization-keeping reflection can be achieved with a high efficiency larger than 98%over the frequency range from 9.2 GHz to 17.7 GHz for both incident left-and right-handed circularly polarized waves.Under oblique incidence,the bandwidth increases as the incident angle varies from 0°to 80°. Moreover,the co-polarization reflection is independent of the incident azimuth angles. 相似文献
83.
Cellulosic nanocomposite membranes from hydroxypropyl cellulose reinforced by cellulose nanocrystals 总被引:1,自引:0,他引:1
Lin Ma Lili Wang Lixin Wu Dongxian Zhuo Zixiang Weng Rongrong Ren 《Cellulose (London, England)》2014,21(6):4443-4454
Cellulosic nanocomposite membranes were prepared by incorporation of cellulose nanocrystals (CNCs) into a hydroxypropyl cellulose (HPC) matrix using a mixing/evaporation technique. CNCs were obtained from filter paper using the sulfuric acid hydrolysis method with the aid of ultrasonication. The relationship between the microstructure and mechanical properties of the CNCs/HPC nanocomposite membranes was studied. Scanning electron microscopy showed that the CNCs were well dispersed in the HPC matrix, and the fracture surface demonstrated a fibrous characteristic. With increasing CNCs content, the tensile strength and Young’s modulus of the CNCs/HPC nanocomposite membranes gradually increased. At 5 wt% content of CNCs, the strength was increased by 525 % and the Young’s modulus by 124 % compared with pure HPC membrane. Moreover, the effect of the phase change of HPC on the mechanical properties of the CNCs5wt%/HPC nanocomposite membranes and the corresponding mechanism were also studied. 相似文献
84.
HUA Wei-Bo ZHENG Zhuo LI Long-Yan GUO Xiao-Dong LIU Heng SHEN Chong-Heng WU Zhen-Guo ZHONG Ben-He HUANG Ling 《物理化学学报》2014,30(8):1481-1486
采用氨蒸发诱导法成功制备出纳米结构LiNi1/3Co1/3Mn1/3O2正极材料,借助X射线衍射(XRD)分析、扫描电镜(SEM)、透射电镜(TEM)、高分辨率透射电镜(HRTEM)、能量分散谱(EDS)和比表面测试等表征手段及恒电流充放电测试研究了其晶体结构、微观形貌和电化学性能.研究表明该方法制备出的材料具有良好的α-NaFeO2层状结构,阳离子混排程度低.纳米片交错堆积而成核桃仁状形貌,片与片之间形成许多纳米孔,而且纳米片的侧面属于{010}活性面,能够提供较多的锂离子的脱嵌通道.在室温下及3.0-4.6 V充放电范围内,该材料在电流密度为0.5C、1C、3C、5C和10C时放电比容量分别为172.90、153.95、147.09、142.16和131.23mAh?g-1.说明其具有优异的电化学性能,非常有潜力用于动力汽车等高功率密度锂离子电池中. 相似文献
85.
Zhi-Xiang Han Bo-Song Zhu Tong-Liang Wua Qing-Qing Yang Yong-Lai Xue Zhen Zhang Xiang-Yang Wua 《中国化学快报》2014,25(1):73-76
In this paper, 2-carboxybenzaldehyde rhodamine B thiohydrazine(1) was synthesized and developed as a fluorescent probe to recognize Hg2+in DMF/H2 O(1:9, v/v) solution with high selectivity. The probe can be applied to the quanti?cation of Hg2+with a linear concentration range covering from 1.0×10-7mol/L to 1.0×10-5mol/L(R2= 0.9985) and a detection limit of 4.2×10-8mol/L. The experiment results show that the response of probe 1 to Hg2+is pH-independent in a wide range from 4.0 to 9.0. Moreover, the probe 1 exhibits excellent selectivity toward Hg2+over other common metal cations. Most importantly, the probe can be employed to monitor Hg2+in living cells using fluorescent imaging technique with satisfied results. 相似文献
86.
Zhuo Li Yang Zhang Fang-Hong Tong Ting-Ting Jiang Hui-Ping Zheng Jian-Nong Ye Qing-Cui Chu 《中国化学快报》2014,25(4):640-644
A hollow-fiber liquid-phase microextraction (HF-LPME) method has been developed for the purification and preconcentration of biogenic polyamines and their precursor amino acids in human saliva. Putrescine (Put), cadaverine (Cad), spermidine (Spe), ornithine (Orn), lysine (Lys), and arginine (Arg) were determined by the CE-LIF detection after microextraction. Several factors that affect extraction efficiency, separation, and detection were investigated. Under the optimum conditions, six analytes could achieve baseline separation within 30 min, exhibiting a linear calibration at three orders of magnitude (r2 〉 0.998); the obtained enrichment factors of HF-LPME were between 19 (for Orn) and 2] 8 (for Cad), and the LODs were in the range of 0.0072-0.26 nmol/L. The proposed HF-LPME/CE-LIF method has been successfully applied for the sensitive analyses of the real-world saliva samples collected from healthy volunteers and different patients with oral diseases, providing a potential method for primary non-invasive diagnosis of some oral diseases. 相似文献
87.
Liqing Zhu Bijun Liu Xia Yang Liangang Zhuo Wanjun Mu Yue Chen Yuchuan Yang Hongyuan Wei Xingliang Li 《Journal of solution chemistry》2020,49(2):166-178
Thermodynamic equilibria of complexes of 1,3-diamino-2-hydroxypropane-N,N,N',N'-tetraacetic acid (DHPTA) with heavy lanthanides (Tb3+, Ho3+ and Lu3+) in aqueous solution have been investigated with potentiometry, spectrophotometry, luminescence spectroscopy and nuclear magnetic resonance spectroscopy (NMR). The results identified three 1:1 Ln/DHPTA (Ln: Tb3+, Ho3+ and Lu3+) complexes with different degrees of deprotonation, LnL−, Ln(H−1L)2−, and Ln(OH)(H−1L)3−, where H−1 represents the deprotonation of the hydroxyl group between two methyliminodiacetate groups in the DHPTA structure. The alkoxide form of the DHPTA hydroxyl group directly binds to the lanthanide atom, forming highly strong chelation. The complex of Ln(H−1L)2− could be present as a dimeric or polymeric complex in solution. 相似文献
88.
由于抗生素的不当使用和细菌多药耐药的出现, 迫切需要开发新的抗菌剂. 本文制备了具有光热转换性能的正电荷半导体高分子材料及具有协同抗菌活性的半导体聚合物纳米粒子(SP-PPh3 NPs). SP-PPh3 NPs的光热转化效率为43.8%. 带正电荷的SP-PPh3 NPs可以附着在细菌上, 有助于将热量有效传递给细菌. 在热和正电荷的协同作用下, SP-PPh3 NPs对革兰氏阴性大肠杆菌(E. coli)和革兰氏阳性金黄色葡萄球菌(S. aureus)均具有抗菌活性, 其对二者的体外抑菌率分别为99.9%和98.6%. 此外, SP-PPh3 NPs具有良好的生物相容性, 对小鼠的主要器官几乎无副作用. 对细菌感染的小鼠皮肤伤口用SP-PPh3 NPs治疗12 d后, 伤口可以很好地愈合. 相似文献
89.
Peng‐Ju Xia Dan Song Zhi‐Peng Ye Yuan‐Zhuo Hu Jun‐An Xiao Hao‐Yue Xiang Xiao‐Qing Chen Hua Yang 《Angewandte Chemie (International ed. in English)》2020,59(17):6706-6710
A photoinduced SET process enables the direct B?H bond activation of NHC–boranes. In contrast to common hydrogen atom transfer (HAT) strategies, this photoinduced reaction simply takes advantage of the beneficial redox potentials of NHC–boranes, thus obviating the need for extra radical initiators. The resulting NHC–boryl radical was used for the borylation of a wide range of α‐trifluoromethylalkenes and alkenes with diverse electronic and structural features, providing facile access to highly functionalized borylated molecules. Labeling and photoquenching experiments provide insight into the mechanism of this photoinduced SET pathway. 相似文献
90.
Dongfeng Du Shuo Zhao Zhuo Zhu Fujun Li Jun Chen 《Angewandte Chemie (International ed. in English)》2020,59(41):18140-18144
The storage of solar energy in battery systems is pivotal for a sustainable society, which faces many challenges. Herein, a Zn–air battery is constructed with two cathodes of poly(1,4‐di(2‐thienyl))benzene (PDTB) and TiO2 grown on carbon papers to sandwich a Zn anode. The PDTB cathode is illuminated in a discharging process, in which photoelectrons are excited into the conduction band of PDTB to promote oxygen reduction reaction (ORR) and raise the output voltage. In a reverse process, holes in the valence band of the illuminated TiO2 cathode are driven for the oxygen evolution reaction (OER) by an applied voltage. A record‐high discharge voltage of 1.90 V and an unprecedented low charge voltage of 0.59 V are achieved in the photo‐involved Zn–air battery, regardless of the equilibrium voltage. This work offers an innovative pathway for photo‐energy utilization in rechargeable batteries. 相似文献