全文获取类型
收费全文 | 6669篇 |
免费 | 1115篇 |
国内免费 | 733篇 |
专业分类
化学 | 4645篇 |
晶体学 | 72篇 |
力学 | 390篇 |
综合类 | 38篇 |
数学 | 778篇 |
物理学 | 2594篇 |
出版年
2024年 | 24篇 |
2023年 | 135篇 |
2022年 | 247篇 |
2021年 | 232篇 |
2020年 | 240篇 |
2019年 | 273篇 |
2018年 | 214篇 |
2017年 | 207篇 |
2016年 | 299篇 |
2015年 | 333篇 |
2014年 | 361篇 |
2013年 | 435篇 |
2012年 | 585篇 |
2011年 | 626篇 |
2010年 | 390篇 |
2009年 | 336篇 |
2008年 | 395篇 |
2007年 | 369篇 |
2006年 | 371篇 |
2005年 | 290篇 |
2004年 | 227篇 |
2003年 | 207篇 |
2002年 | 153篇 |
2001年 | 153篇 |
2000年 | 155篇 |
1999年 | 175篇 |
1998年 | 144篇 |
1997年 | 129篇 |
1996年 | 122篇 |
1995年 | 116篇 |
1994年 | 110篇 |
1993年 | 74篇 |
1992年 | 75篇 |
1991年 | 85篇 |
1990年 | 55篇 |
1989年 | 34篇 |
1988年 | 33篇 |
1987年 | 30篇 |
1986年 | 19篇 |
1985年 | 19篇 |
1984年 | 9篇 |
1983年 | 19篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有8517条查询结果,搜索用时 31 毫秒
991.
Jin‐Yue Zeng Xiao‐Shuang Wang Yong‐Dan Qi Yun Yu Xuan Zeng Xian‐Zheng Zhang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(17):5748-5752
Polycyclic aromatic derivatives can trap 1O2 to form endoperoxides (EPOs) for O2 storage and as sources of reactive oxygen species. However, these materials suffer from structural amorphism, which limit both practical applications and fundamental studies on their structural optimization for O2 capture and release. Metal–organic frameworks (MOFs) offer advantages in O2 binding, such as clear structure–performance relationships and precise controllability. Herein, we report the reversible binding of O2 is realized via the chemical transformation between anthracene‐based and the corresponding EPO‐based MOF. It is shown that anthracene‐based MOF, the framework featuring linkers with polycyclic aromatic structure, can rapidly trap 1O2 to form EPOs and can be restored upon UV irradiation or heating to release O2. Furthermore, we confirm that photosensitizer‐incorporated anthracene‐based MOF are promising candidates for reversible O2 carriers controlled by switching Vis/UV irradiation. 相似文献
992.
Zhenghui Luo Fei Wu Teng Zhang Xuan Zeng Yiqun Xiao Tao Liu Cheng Zhong Xinhui Lu Linna Zhu Shihe Yang Chuluo Yang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(25):8608-8613
Electron transport materials (ETM) play an important role in the improvement of efficiency and stability for inverted perovskite solar cells (PSCs). This work reports an efficient ETM, named PDI‐C60, by the combination of perylene diimide (PDI) and fullerene. Compared to the traditional PCBM, this strategy endows PDI‐C60 with slightly shallower energy level and higher electron mobility. As a result, the device based on PDI‐C60 as electron transport layer (ETL) achieves high power conversion efficiency (PCE) of 18.6 %, which is significantly higher than those of the control devices of PCBM (16.6 %) and PDI (13.8 %). The high PCE of the PDI‐C60‐based device can be attributed to the more matching energy level with the perovskite, more efficient charge extraction, transport, and reduced recombination rate. To the best of our knowledge, the PCE of 18.6 % is the highest value in the PSCs using PDI derivatives as ETLs. Moreover, the device with PDI‐C60 as ETL exhibits better device stability due to the stronger hydrophobic properties of PDI‐C60. The strategy using the PDI/fullerene hybrid provides insights for future molecular design of the efficient ETM for the inverted PSCs. 相似文献
993.
Zhipeng Jiang Liu Jin Zhilong Han Wei Hu Ziqi Zeng Yulong Sun Jia Xie 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(33):11496-11500
Lithium‐metal anodes are recognized as the most promising next‐generation anodes for high‐energy‐storage batteries. However, lithium dendrites lead to irreversible capacity decay in lithium‐metal batteries (LMBs). Besides, the strict assembly‐environment conditions of LMBs are regarded as a challenge for practical applications. In this study, a workable lithium‐metal anode with an artificial hybrid layer composed of a polymer and an alloy was designed and prepared by a simple chemical‐modification strategy. Treated lithium anodes remained dendrite‐free for over 1000 h in a Li–Li symmetric cell and exhibited outstanding cycle performance in high‐areal‐loading Li–S and Li–LiFePO4 full cells. Moreover, the treated lithium showed improved moisture stability that benefits from the hydrophobicity of the polymer, thus retaining good electrochemical performance after exposure to humid air. 相似文献
994.
Xiaofang Zhao Xianxu Chu Guntram Rauhut Changyun Chen Chao Song Bo Lu Xiaoqing Zeng 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(35):12292-12297
Methoxyphosphinidene oxide (CH3OPO) and isomeric methyldioxophosphorane (CH3PO2) are key intermediates in the degradation of organophosphorus compounds (OPCs). Unlike the nitrogen analogues CH3ONO and CH3NO2, the experimental data for these two prototypical OPCs are scarce. By high‐vacuum flash pyrolysis (HVFP) of the diazide CH3OP(O)(N3)2 at 1000 K, the cis and trans conformers of CH3OPO have been generated in the gas phase and subsequently isolated in cryogenic Ar and N2 matrices for IR spectroscopic characterization. Upon 266 nm laser irradiation of CH3OPO, cis→trans conformational conversion occurs with concurrent isomerization to CH3PO2. The spectroscopic identification of CH3OPO and CH3PO2 is supported by D‐, 13C‐, and 18O‐isotope labeling and quantum chemical calculations at the CCSD(T)‐F12a/cc‐pVTZ‐F12 level using configuration‐selective vibrational configuration interaction (VCI). 相似文献
995.
Zichun Wang Luke A. O'Dell Xin Zeng Can Liu Shufang Zhao Wenwen Zhang Marianne Gaborieau Yijiao Jiang Jun Huang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(50):18229-18236
Commercial bioethanol can be readily converted into ethylene by a dehydration process using solid acids, such as Brønsted acidic H‐ZSM‐5 zeolites, and thus, it is an ideal candidate to replace petroleum and coal for the sustainable production of ethylene. Now, strong Lewis acidic extra‐framework three‐coordinate Al3+ species were introduced into H‐ZSM‐5 zeolites to improve their catalytic activity. Remarkably, Al3+ species working with Brønsted acid sites can accelerate ethanol dehydration at a much lower reaction temperature and shorten the unsteady‐state period within 1–2 h, compared to >9 h for those without Al3+ species, which can significantly enhance the ethanol dehydration efficiency and reduce the cost. The reaction mechanism, studied by solid‐state NMR, shows that strong Lewis acidic EFAl‐Al3+ species can collaborate with Brønsted acid sites and promote ethanol dehydration either directly or indirectly via an aromatics‐based cycle to produce ethylene. 相似文献
996.
Shuaifei Guo Cuihong Sun Lingpeng Meng Yanli Zeng 《Journal of computational chemistry》2019,40(32):2827-2833
The mechanism of ring-opening polymerization of L-lactide by iodine trichloride (ICl3) catalyst has been explored by using density functional theory (DFT) calculations and three catalytic pathways were proposed. The first and second pathways belong to the halogen bond catalysis, and the third pathway involves the ICl3 catalysts participating in reactions. When the carbonyl group was maintained involved in the reaction and activated catalytically by the halogen bond, there are two possible pathways. The first pathway involves only one transition state, and the second pathway requires two transition states. There is another pathway in which ICl3 directly participates in the reaction, it is named the third pathway. Two different transition states of the four-membered rings are generated successively, the transfer of I─O bonds determined the progress of the reaction. Theoretical calculations in this work provide the most basic understanding of ring-opening polymerization of L-lactide by ICl3 catalysts. © 2019 Wiley Periodicals, Inc. 相似文献
997.
Research on Chemical Intermediates - MoFe-N, MoFe/c–CeO2, MoFe/p1–CeO2, and MoFe/p2–CeO2 (where N, c, and p stand for non-supported, nanocube, and nanoparticle) oxide catalysts... 相似文献
998.
合成了孔道平行于短轴方向的W原位掺杂的介孔SBA-15分子筛(W-s-SBA-15), 以其为载体制备了Pt/W-s-SBA-15催化剂, 考察了催化剂中Pt、W负载量变化对甘油氢解制1,3-丙二醇(1,3-PDO)性能的影响. 采用多种手段对催化剂的形貌、活性组分Pt和W的存在状态、催化剂的酸性等性质进行了系统的表征. 催化剂评价结果表明, 随着Pt、W负载量的增加, 甘油的总转化率和液相转化率(CTL)提高, 而1,3-PDO选择性呈先升高后降低的火山型变化趋势. 在Pt负载量为4.0 wt%、W/Si物质的量比为1/480的4Pt/W-s-SBA-15(1/480)催化剂上, 在433 K、H2压力4.0 MPa、反应时间24 h的条件下, 甘油氢解制1,3-PDO的得率可达49.0%. 根据表征结果, 我们发现在Pt/W-s-SBA-15催化剂上的甘油转化率与Pt活性比表面积直接相关, 而小的Pt粒径、Pt与单分散WO4之间密切的协同作用, 则有助于提高1,3-PDO的选择性. 相似文献
999.
JPC – Journal of Planar Chromatography – Modern TLC - The aim of this work was to establish qualitative and quantitative methods for studying Guyinye residue extracts and Turkish gall... 相似文献
1000.
This review supplied direct insight of host-guest molecule system by using COR as the guest molecule. 相似文献