全文获取类型
收费全文 | 976篇 |
免费 | 149篇 |
国内免费 | 120篇 |
专业分类
化学 | 696篇 |
晶体学 | 9篇 |
力学 | 58篇 |
综合类 | 4篇 |
数学 | 98篇 |
物理学 | 380篇 |
出版年
2023年 | 28篇 |
2022年 | 27篇 |
2021年 | 46篇 |
2020年 | 50篇 |
2019年 | 33篇 |
2018年 | 27篇 |
2017年 | 20篇 |
2016年 | 51篇 |
2015年 | 56篇 |
2014年 | 33篇 |
2013年 | 65篇 |
2012年 | 78篇 |
2011年 | 104篇 |
2010年 | 58篇 |
2009年 | 71篇 |
2008年 | 72篇 |
2007年 | 59篇 |
2006年 | 54篇 |
2005年 | 43篇 |
2004年 | 25篇 |
2003年 | 19篇 |
2002年 | 15篇 |
2001年 | 15篇 |
2000年 | 14篇 |
1999年 | 18篇 |
1998年 | 18篇 |
1997年 | 13篇 |
1996年 | 9篇 |
1995年 | 21篇 |
1994年 | 9篇 |
1993年 | 18篇 |
1992年 | 14篇 |
1991年 | 12篇 |
1990年 | 6篇 |
1989年 | 8篇 |
1988年 | 8篇 |
1987年 | 5篇 |
1986年 | 1篇 |
1985年 | 5篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1968年 | 2篇 |
排序方式: 共有1245条查询结果,搜索用时 0 毫秒
181.
Yazhen Wang Rifang Li Hongge Jia Guoxing Yang Yutao Di Chenxi Xu Liqun Ma Hui Zhang Yongli Zhou Yu Zang Shuangping Xu Zhaoyang Sun Liwu Zu Chenge Yue Tianyu Lan 《Chemical Papers》2018,72(11):2871-2877
A novel peroxy group-containing silane coupling agent was synthesized and anchored on the surface of titanium dioxide nanoparticles (nano-TiO2) to form an immobilized-initiator-modified nano-TiO2 species. In this study, the kinetic parameters of the peroxy group-containing silane were tested and assessed using DSC. The pre-exponential factor (Ad) was 8.973?×?108 and the activation energy (Ea) was 80.736 kJ mol?1. Moreover, the empirical Arrhenius equation was determined to be ln Kd?=???80.736/RT?+?ln(8.973?×?108). To obtain continuous polymers, acrylonitrile (AN) and methyl methacrylate (MMA) were polymerized using the novel peroxy group-containing silane and FeSO4 as an initiator system. The number average molecular weights (Mn of PAN?=?3×104 and Mn of PMMA?=?1.4?×?105) and polydispersity indexes (PDI of PAN?=?2.76 and PDI of PMMA?=?1.65) were determined by GPC. It was suggested that the redox initiation system can generate highly reactive species on the surfaces of inorganic nanoparticles. The nano-TiO2-grafted polymers were successfully obtained. 相似文献
182.
Let A be a 0 − 1 matrix with precisely two 1’s in each column and let 1 be the all-one vector. We show that the problems of deciding whether the linear system
(1) defines an integral polyhedron,
(2) is totally dual integral (TDI), and
(3) box-totally dual integral (box-TDI)
are all co-NP-complete, thereby confirming the conjecture on NP-hardness of recognizing TDI systems made by Edmonds and Giles
in 1984.
Supported in part by NSA grant H98230-05-1-0081 and NSF grants DMS-0556091 and ITR-0326387.
Supported in part by the Research Grants Council of Hong Kong and Seed Funding for Basic Research of HKU. 相似文献
183.
Zhu K Huang L Zhu J Zhuang Z 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,69(2):566-571
Gold colloids were synthesized via mixing the aqueous solution of HAuCl(4) and Triton X-100 at room temperature. The gold sol samples were quickly obtained during first 2h then the samples were placed for 8h to ensure they were completely stable. The colour of most samples turned to violet red. But the sample with 0.5ml TX-100 remained colorless. During synthesizing, UV-vis absorption spectra were recorded every 10s. By studying the synthesis time-dependent surface plasmon resonance (SPR), we found that the growth of gold colloids presented an exponential increase form. By analyzing the TX-100 concentration dependence of absorption peak, the effect of TX-100 concentration on gold colloid diameter was studied and the gold colloid's final dimension was resulted from competition between reducing speed and coating speed. 相似文献
184.
Alejandro Capap Ming-Dong Zhou Shu-Liang Zang Fritz E. Kühn 《Journal of organometallic chemistry》2008,693(20):3240-3244
Equimolar reactions of the derivatives of ((2-hydroxynapthalen-1-yl)methylene)aniline with methyltrioxorhenium (MTO) lead to complexes 1–4, where MTO is coordinated via the oxygen of the former hydroxyl-group to MTO. The resulting complexes are very stable but not particularly catalytically active if no electron acceptor resides on the Schiff base. The electron withdrawing groups placed on the Schiff base ligand have the effect of increasing the catalytic activity but somewhat decrease the complex stability. 相似文献
185.
Dr. Pengwei Li Linfang Yan Qingli Cao Prof. Chao Liang He Zhu Sihui Peng Yongpeng Yang Yuncai Liang Rudai Zhao Prof. Shuangquan Zang Prof. Yiqiang Zhang Prof. Yanlin Song 《Angewandte Chemie (International ed. in English)》2023,62(13):e202217910
Low-dimensional Ruddlesden-Popper (LDRP) perovskites still suffer from inferior carrier transport properties. Here, we demonstrate that efficient exciton dissociation and charge transfer can be achieved in LDRP perovskite by introducing γ-aminobutyric acid (GABA) as a spacer. The hydrogen bonding links adjacent spacing sheets in (GABA)2MA3Pb4I13 (MA=CH3NH3+), leading to the charges localized in the van der Waals gap, thereby constructing “charged-bridge” for charge transfer through the spacing region. Additionally, the polarized GABA weakens dielectric confinement, decreasing the (GABA)2MA3Pb4I13 exciton binding energy as low as ≈73 meV. Benefiting from these merits, the resultant GABA-based solar cell yields a champion power conversion efficiency (PCE) of 18.73 % with enhanced carrier transport properties. Furthermore, the unencapsulated device maintains 92.8 % of its initial PCE under continuous illumination after 1000 h and only lost 3 % of its initial PCE under 65 °C for 500 h. 相似文献
186.
Yan Jin Qiu-Chen Peng Jing-Wen Xie Prof. Dr. Kai Li Prof. Dr. Shuang-Quan Zang 《Angewandte Chemie (International ed. in English)》2023,62(19):e202301000
In this study, a pair of chiral copper(I) cluster-assembled materials (R/S- 2 ) was prepared, exhibiting unique photo-response characteristics with a concentration-wavelength correlation property in DMSO solution. By the combination of R/S- 2 with a polymethyl methacrylate (PMMA) matrix, the first photo-activated circularly polarized luminescence (CPL) film was developed, the CPL signal (glum=9×10−3) of which could be induced by UV light irradiation. Moreover, the film exhibited a reversible photo-response and extremely good fatigue resistance. Mechanism study revealed that the photo-response properties of the R/S- 2 solution and film are attributed to the aggregation-induced emission (AIE) characteristics of R/S- 2 and a photo-induced deoxygenation process. This study enriches the types of luminescent cluster-assembled molecules and provides a new strategy for the construction of metal cluster-based stimuli-responsive composite materials. 相似文献
187.
Qiu-Chen Peng Dr. Yu-Bing Si Jia-Wang Yuan Qi Yang Zi-Ying Gao Dr. Yuan-Yuan Liu Dr. Zhao-Yang Wang Dr. Kai Li Prof. Shuang-Quan Zang Prof. Ben Zhong Tang 《Angewandte Chemie (International ed. in English)》2023,62(40):e202308194
X-ray imaging technology has achieved important applications in many fields and has attracted extensive attentions. Dynamic X-ray flexible imaging for the real-time observation of the internal structure of complex materials is the most challenging type of X-ray imaging technology, which requires high-performance X-ray scintillators with high X-ray excited luminescence (XEL) efficiency as well as excellent processibility and stability. Here, a macrocyclic bridging ligand with aggregation-induced emission (AIE) feature was introduced for constructing a copper iodide cluster-based metal–organic framework (MOF) scintillator. This strategy endows the scintillator with high XEL efficiency and excellent chemical stability. Moreover, a regular rod-like microcrystal was prepared through the addition of polyvinyl pyrrolidone during the in situ synthesis process, which further enhanced the XEL and processibility of the scintillator. The microcrystal was used for the preparation of a scintillator screen with excellent flexibility and stability, which can be used for high-performance X-ray imaging in extremely humid environments. Furthermore, dynamic X-ray flexible imaging was realized for the first time. The internal structure of flexible objects was observed in real time with an ultrahigh resolution of 20 LP mm−1. 相似文献
188.
Dr. Peng Luo Dr. Xue-Jing Zhai Dr. Sha Bai Dr. Yu-Bing Si Dr. Xi-Yan Dong Prof. Dr. Ying-Feng Han Prof. Dr. Shuang-Quan Zang 《Angewandte Chemie (International ed. in English)》2023,62(22):e202219017
Chiral Au nanoclusters have promising application prospects in chiral sensing, asymmetric catalysis, and chiroptics. However, enantiopure superatomic homogold clusters with crystallographic structures emitting bright circularly polarized luminescence (CPL) remain challenging. In this study, we designed chiral N-heterocyclic carbenes (NHCs), and for the first time enantioselectively synthesized a pair of monovalent cationic superatomic Au13 clusters. This new enantiomeric pair of clusters has a quasi-C2 symmetric core and exhibited CPL with an unprecedent solution-state quantum yield (QY) of 61 % among those of the atomically precise Au nanoclusters. DFT calculations provided insights into the circular dichroism behavior, and revealed the origin of CPL from superatomic Au clusters. This work opens a new avenue for developing novel homochiral nanoclusters using chiral NHC ligands and provides fundamental understanding of the origin of the chiroptics of metal clusters. 相似文献
189.
Qingbin Li Yihan Zhang Junfeng Lin Ye Zou Pu Wang Dr. Zhengsheng Qin Yongshuai Wang Dr. Yang Li Prof. Dr. Yu Zhang Dr. Can Gao Prof. Dr. Yaping Zang Prof. Dr. Wenping Hu Prof. Dr. Huanli Dong 《Angewandte Chemie (International ed. in English)》2023,62(42):e202308146
The development of blue-emissive ambipolar organic semiconductor is an arduous target due to the large energy gap, but is an indispensable part for electroluminescent device, especially for the transformative display technology of simple-structured organic light-emitting transistor (SS-OLET). Herein, we designed and synthesized two new dibenzothiophene sulfone-based high mobility blue-emissive organic semiconductors (DNaDBSOs), which demonstrate superior optical property with solid-state photoluminescent quantum yield of 46–67 % and typical ambipolar-transporting properties in SS-OLETs with symmetric gold electrodes. Comprehensive experimental and theoretical characterizations reveal the natural of ambipolar property for such blue-emissive DNaDBSOs-based materials is ascribed to a synergistic effect on lowering LUMO level and reduced electron injection barrier induced by the interfacial dipoles effect on gold electrodes due to the incorporation of appropriate DBSO unit. Finally, efficient electroluminescence properties with high-quality blue emission (CIE (0.179, 0.119)) and a narrow full-width at half-maximum of 48 nm are achieved for DNaDBSO-based SS-OLET, showing good spatial control of the recombination zone in conducting channel. This work provides a new avenue for designing ambipolar emissive organic semiconductors by incorporating the synergistic effect of energy level regulation and molecular-metal interaction, which would advance the development of superior optoelectronic materials and their high-density integrated optoelectronic devices and circuits. 相似文献
190.
Li-Hua Zang Yan-Ling Liu Jia-Qing Liu Qiang Tian Feng-Ning Xiang 《Chromatographia》2008,68(5-6):351-356
The purge and trap (P&T) technique was improved for measuring the release of organic compounds with weak volatility (weak VOCs) from dry plant materials. Using distilled water as a dispersant, the plant tissues were mulled and placed in the purge tube of a P&T concentrator. Then the sample-containing purge tube was heated to 80 °C with helium as the carrier gas, and the purged volatiles were preconcentrated in the trap prior to analysis with GC-MS. The VOCs in Chinese herbal medicinal plants Swertia tetraptera, Saussurea involucrate and S. lacostei, which had been stored dry for 1–2.5 years were assayed with this improved method and conventional P&T techniques. Our results show this new P&T method had great promise for determining the VOCs in dry plant materials. Using this new technique, we identified 38 weak VOCs with a large peak area from the dry samples. In contrast, less than five VOCs were detected by the conventional P&T method. So the improved heat-purge and trap system showed to be more efficient for measuring the release of the weak VOCs from dry plant materials. 相似文献