全文获取类型
收费全文 | 53376篇 |
免费 | 8507篇 |
国内免费 | 5680篇 |
专业分类
化学 | 37476篇 |
晶体学 | 642篇 |
力学 | 3092篇 |
综合类 | 329篇 |
数学 | 5963篇 |
物理学 | 20061篇 |
出版年
2024年 | 182篇 |
2023年 | 1124篇 |
2022年 | 2081篇 |
2021年 | 2217篇 |
2020年 | 2273篇 |
2019年 | 2151篇 |
2018年 | 1837篇 |
2017年 | 1780篇 |
2016年 | 2612篇 |
2015年 | 2641篇 |
2014年 | 3103篇 |
2013年 | 3962篇 |
2012年 | 4855篇 |
2011年 | 4793篇 |
2010年 | 3327篇 |
2009年 | 3116篇 |
2008年 | 3349篇 |
2007年 | 2961篇 |
2006年 | 2659篇 |
2005年 | 2279篇 |
2004年 | 1742篇 |
2003年 | 1395篇 |
2002年 | 1279篇 |
2001年 | 1021篇 |
2000年 | 898篇 |
1999年 | 1047篇 |
1998年 | 859篇 |
1997年 | 809篇 |
1996年 | 797篇 |
1995年 | 728篇 |
1994年 | 614篇 |
1993年 | 519篇 |
1992年 | 430篇 |
1991年 | 393篇 |
1990年 | 335篇 |
1989年 | 241篇 |
1988年 | 180篇 |
1987年 | 164篇 |
1986年 | 162篇 |
1985年 | 140篇 |
1984年 | 89篇 |
1983年 | 94篇 |
1982年 | 55篇 |
1981年 | 39篇 |
1980年 | 29篇 |
1979年 | 19篇 |
1977年 | 18篇 |
1976年 | 20篇 |
1975年 | 21篇 |
1972年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
951.
Xiaodong Si Yuanyuan Jia Xinqi Luan Luo Yang Yong Pei Wang Zhou 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(9):2686-2690
A variety of benzofuranone‐based spiroisochromenes were originally designed and synthesized to gain insight into the oxa‐6π electrocyclic reaction of cis,cis‐1,8‐dioxatetraene for the first time. The stability of the 1,8‐dioxatetraene intermediate is governed by its steric congestion and can be fine‐tuned through modification of the backbone structure, leading to the reactivity differences in the 6π electrocyclic reaction and the emergence of photochromic properties. 相似文献
952.
Shaoxuan Yang Yihuan Yu Meiling Dou Zhengping Zhang Liming Dai Feng Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(41):14866-14872
Two‐dimensional conjugated aromatic networks (CAN) with ultra‐thin conjugated layers (ca. 3.5 nm) and high single‐metal‐atom‐site density (mass content of 10.7 wt %, and 0.73 metal atoms per nm2) are prepared via a facile pyrolysis‐free route involving a one‐step ball milling of the solid‐phase‐synthesized polyphthalocyanine. These materials display outstanding oxygen reduction reaction (ORR) mass activity of 47 mA mgcat.?1 represents 1.3‐ and 6.4‐fold enhancements compared to Pt and Pt/C in benchmark Pt/C, respectively. Moreover, the primary Zn‐air batteries constructed with CAN as an air electrode demonstrate a mass/volume power density of 880 W gcat.?1/615 W cmcat.?3 and stable long‐term operation for 100 h. This strategy offers a new way to design high‐performance electrocatalysts with atomic precision for use in other energy‐storage and conversion applications. 相似文献
953.
Yan Zhan Yang Wang Qunfeng Cheng Chang Li Kaixuan Li Huizeng Li Jingsong Peng Bo Lu Yu Wang Yanlin Song Lei Jiang Mingzhu Li 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(46):16608-16614
Extensive applications for photodetectors have led to demand for high‐responsivity polarization‐sensitive light detection. Inspired by the elaborate architecture of butterfly Papilio paris, a 1D nanograting bonded porous 2D photonic crystal perovskite photodetector (G‐PC‐PD) using a commercial DVD master and 2D crystalline colloidal arrays template was fabricated. The coupling effect from grating diffraction and reflection of the PC stopband renders the enhanced light harvesting of G‐PC‐PD. The porous scaffold and nanoimprinting process afford a highly crystalline perovskite film. White light responsivity and detectivity of G‐PC‐PD are up to 12.67 A W?1 and 3.22×1013 Jones (6~7 times that of a pristine perovskite photodetector). The highly ordered nanograting arrays of G‐PC‐PD enable polarization‐sensitive light detection with a rate of ?0.72 nA deg?1. This hierarchical perovskite integrated nanograting and 2D PC architecture opens a new avenue to high‐performance optoelectronic devices. 相似文献
954.
Zuqiang Xu Hanyan Wu Yang Tang Wei Xu Yanbing Zhai 《Journal of mass spectrometry : JMS》2019,54(7):583-591
A better understanding of nanoelectrospray ionization (nano‐ESI) would be beneficial in further improving the performances of nano‐ESI. In this work, the pulsed high‐voltage (HV) nano‐ESI has been electrically modeled and then systematically characterized by both voltage‐current and mass spectrometry measurements. First, the equivalent resistance of a nano‐ESI source changes with respect to both emitter tip diameter and the HV applied. Increased voltage could improve both spray current and ionization efficiency of the pulsed HV nano‐ESI. Compared with conventional DC HV method, a pulsed HV has less heating effect on the capillary tip and thus allowing the application of a much higher voltage onto a nano‐ESI source. As a result, a pulsed HV nano‐ESI could further boost the ionization efficiency of nano‐ESI by employing even higher voltages than conventional DC nano‐ESI sources. 相似文献
955.
Lingjuan Chen Jun Zhang Yueting Wei Zhen Yang Ping Liu Jie Zhang Bin Dai 《Tetrahedron》2019,75(46):130664
An efficient synthesis of N-heterocyclic aryl sulfides via NH4I/1,10-phenanthroline-catalyzed direct sulfenylation reactions was reported. In this reaction, heteroarenes such as indoles, and pyrroles serve as nucleophiles by installing a arylthio group at the C3 and C2 position of heterocycles, respectively. With readily accessible and free of unpleasant odor ethyl arylsulfinates as sulfur reagents, the metal-free-catalyzed direct sulfenylation of N-heteroarenes has been developed. 3-Arylthio-indoles and 2-arylthio-pyrroles derivatives were obtained in moderate to excellent yields, even on gram scale. The reaction was general for a broad scope of substrates and demonstrated good tolerance to a variety of functional groups. 相似文献
956.
Fangling Lu Zengzhuan Yang Tao Wang Tianhao Wang Yuying Zhang Yong Yuan Aiwen Lei 《中国化学》2019,37(6):538-538
The inside cover picture shows an electrochemical oxidative Csp3‐H/S‐H activation with hydrogen evolution for the synthesis of tetrasubstituted olefins. This method features very high atom economy, besides hydrogen gas, under the base‐free, transition met‐al‐free, and oxidants‐free conditions, no other by‐products were generated. More details are discussed in the article by Lei et al. on page 547–551.
957.
Xianhao Lv Mizhen Sun Lei Xu Runzhe Wang Huayi Zhou Yuyu Pan Shitong Zhang Qikun Sun Shanfeng Xue Wenjun Yang 《Chemical science》2020,11(19):5058
Designing a donor–acceptor (D–A) molecule with a hybridized local and charge transfer (HLCT) excited state is a very effective strategy for producing an organic light-emitting diode (OLED) with a high exciton utilization efficiency and external quantum efficiency. Herein, a novel twisting D–π–A fluorescent molecule (triphenylamine–anthracene–phenanthroimidazole; TPAAnPI) is designed and synthesized. The excited state properties of the TPAAnPI investigated through photophysical experiments and density functional theory (DFT) analysis reveal that its fluorescence is due to the HLCT excited state. The optimized non-doped blue OLED using TPAAnPI as a light-emitting layer exhibits a novel blue emission with an electroluminescence (EL) peak at 470 nm, corresponding to the Commission International de L''Eclairage (CIE) coordinates of (0.15, 0.22). A fabricated device termed Device II exhibits a maximum current efficiency of 18.09 cd A−1, power efficiency of 12.35 lm W−1, luminescence of ≈29 900 cd cm−2, and external quantum efficiency (EQE) of 11.47%, corresponding to a high exciton utilization efficiency of 91%. Its EQE remains as high as 9.70% at a luminescence of 1000 cd m−2 with a low efficiency roll-off of 15%. These results are among the best for HLCT blue-emitting materials involved in non-doped blue fluorescent OLEDs. The performance of Device II highlights a great industrial application potential for the TPAAnPI molecule.A new pure fluorescent blue HLCT-emitter was designed and synthesized. Highly efficient non-doped blue OLEDs with low efficiency roll-off were achieved. 相似文献
958.
Shuangshuang Ji Xiuzhu Yang Xiaolong Chen Ang Li Doudou Yan Haiyan Xu Hao Fei 《Chemical science》2020,11(34):9126
The development of chemotherapy, an important cancer treatment modality, is hindered by the frequently found drug-resistance phenomenon. Meanwhile, researchers have been enthused lately by the synergistic use of chemotherapy with emerging immunotherapeutic treatments. In an effort to address both of the two unmet needs, reported herein is a study on a series of membrane active iridium(iii) complexed oligoarginine peptides with a new cell death mechanism capable of overcoming drug resistance as well as stimulating immunological responses. A systematic structure–activity relationship study elucidated the interdependent effects of three structural factors, i.e., hydrophobicity, topology and cationicity, on the regulation of the cytotoxicity of the Ir(iii)-oligoarginine peptides. With the most prominent toxicities, Ir-complexed octaarginines (R8) were found to display a progressive oncotic cell death featuring cell membrane-penetration and eruptive cytoplasmic content release. Consequently, this membrane-centric death mechanism showed promising potential in overcoming multiple chemical drug-resistance of cancer cells. More interestingly, the eruptive mode of cell death proved to be immunogenic by stimulating the dendritic cell maturation and inflammatory factor accumulation in mice tumours. Taking these mechanisms together, this work demonstrates that membrane active compounds may become the next generation chemotherapeutics because of their combined advantages.Structure optimized Ir-complexed cyclic octa-arginine shows a potential of “one-drug two-effects” for cancer treatment. 相似文献
959.
Jiancheng Rao Liuqing Yang Xuefei Li Dr. Lei Zhao Dr. Shumeng Wang Prof. Junqiao Ding Prof. Lixiang Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(41):18059-18065
The meta junction is proposed to realize efficient thermally activated delayed fluorescence (TADF) in donor–acceptor (D-A) conjugated polymers. Based on triphenylamine as D and dicyanobenzene as A, as a proof of concept, a series of D-A conjugated polymers has been developed by changing their connection sites. When the junction between D and A is tuned from para to meta, the singlet–triplet energy splitting (ΔEST) is found to be significantly decreased from 0.44 to 0.10 eV because of the increasing hole–electron separation. Unlike the para-linked analogue with no TADF, consequently, the meta-linked polymer shows a strong delayed fluorescence. Its corresponding solution-processed organic light-emitting diodes (OLEDs) achieve a promising external quantum efficiency (EQE) of 15.4 % (51.9 cd A−1, 50.9 lm W−1) and CIE coordinates of (0.34, 0.57). The results highlight the bright future of D-A conjugated polymers used for TADF OLEDs. 相似文献
960.
Dr. Heyong Cheng Shuli Tang Tingyuan Yang Prof. Shiqing Xu Prof. Xin Yan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(45):20034-20039
Microdroplet chemistry is attracting increasing attention for accelerated reactions at the solution–air interface. We report herein a voltage-controlled interfacial microreactor that enables acceleration of electrochemical reactions which are not observed in bulk or conventional electrochemical cells. The microreactor is formed at the interface of the Taylor cone in an electrospray emitter with a large orifice, thus allowing continuous contact of the electrode and the reactants at/near the interface. As a proof-of-concept, electrooxidative C−H/N−H coupling and electrooxidation of benzyl alcohol were shown to be accelerated by more than an order of magnitude as compared to the corresponding bulk reactions. The new electrochemical microreactor has unique features that allow i) voltage-controlled acceleration of electrochemical reactions by voltage-dependent formation of the interfacial microreactor; ii) “reversible” electrochemical derivatization; and iii) in situ mechanistic study and capture of key radical intermediates when coupled with mass spectrometry. 相似文献