全文获取类型
收费全文 | 5828篇 |
免费 | 1161篇 |
国内免费 | 836篇 |
专业分类
化学 | 2805篇 |
晶体学 | 70篇 |
力学 | 304篇 |
综合类 | 125篇 |
数学 | 611篇 |
物理学 | 1463篇 |
无线电 | 2447篇 |
出版年
2024年 | 41篇 |
2023年 | 135篇 |
2022年 | 254篇 |
2021年 | 282篇 |
2020年 | 259篇 |
2019年 | 244篇 |
2018年 | 221篇 |
2017年 | 287篇 |
2016年 | 273篇 |
2015年 | 350篇 |
2014年 | 396篇 |
2013年 | 457篇 |
2012年 | 510篇 |
2011年 | 467篇 |
2010年 | 430篇 |
2009年 | 437篇 |
2008年 | 439篇 |
2007年 | 404篇 |
2006年 | 336篇 |
2005年 | 282篇 |
2004年 | 172篇 |
2003年 | 143篇 |
2002年 | 139篇 |
2001年 | 127篇 |
2000年 | 135篇 |
1999年 | 95篇 |
1998年 | 59篇 |
1997年 | 53篇 |
1996年 | 51篇 |
1995年 | 38篇 |
1994年 | 26篇 |
1993年 | 30篇 |
1992年 | 33篇 |
1991年 | 32篇 |
1990年 | 30篇 |
1989年 | 22篇 |
1988年 | 6篇 |
1987年 | 12篇 |
1986年 | 17篇 |
1985年 | 15篇 |
1984年 | 12篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1981年 | 10篇 |
1980年 | 18篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1973年 | 4篇 |
排序方式: 共有7825条查询结果,搜索用时 15 毫秒
991.
The mechanism is investigated for CptBuRh(OH)2-catalyzed annulation of 2-biphenylboronic acid with three activated alkenes using M06-2X functional. The reaction comprises transmetalation via two steps and following C-H activation producing reactive Rh-biphenyl complex with two Rh—C σ bonds. After the coordination/insertion of alkenes, respective fused or bridged cyclic products are yielded depending on different alkenes accompanied by the release of CptBuRh. The promotion of CptBuRh(OH)2 lies in the barrier decrease of transmetalation and C-H activation ready for coordination/insertion ensuring the smooth progress of common rate-limiting reductive elimination. The stereoselective transfer and ring rotation are specific for benzoquinone and cyclopropenone. The role of Rh(III) catalyst and release of Rh(I) is supported by Multiwfn analysis on frontier molecular orbital(FMO) of specific transiton states(TSs) and Mayer bond order(MBO) value of vital bonding, breaking. 相似文献
992.
Dr. Peng Zhang Qian-Cheng Luo Dr. Zhenhua Zhu Wanrong He Nan Song Junting Lv Xuning Wang Prof. Quan-Guo Zhai Prof. Yan-Zhen Zheng Prof. Jinkui Tang 《Angewandte Chemie (International ed. in English)》2023,62(12):e202218540
The syntheses and magnetic properties of organometallic heterometallic compounds [K(THF)6]{CoI[(μ3-HAN)RE2Cp*4]2} ( 1-RE ) and [K(Crypt)]2{CoI[(μ3-HAN)RE2Cp*4]2} ( 2-RE ) containing hexaazatrinaphthylene radicals (HAN⋅3−) and four rare earth (RE) ions are reported. 1-RE shows isolable species with ligand-based mixed valency as revealed by cyclic voltammetry (CV) thus leading to the isolation of 2-RE via one-electron chemical reduction. Strong electronic communication in mixed-valency supports stronger overall ferromagnetic behaviors in 2-RE than 1-RE containing Gd and Dy ions. Ac magnetic susceptibility data reveal 1-Dy and 2-Dy both exhibit slow magnetic relaxation. Importantly, larger coercive field was observed in the hysteresis of 2-Dy at 2.0 K, indicating the enhanced SMM behavior compared with 1-Dy . Ligand-based mixed-valency strategy has been used for the first time to improve the magnetic coupling in lanthanide (Ln) SMMs, thus opening up new ways to construct strongly coupled Ln-SMMs. 相似文献
993.
Shuai Zhang Hancheng Qin Shuwen Cheng Yue Zhang Nan Gao Prof. Meining Zhang 《Angewandte Chemie (International ed. in English)》2023,62(16):e202300083
Reactive oxygen species (ROS)-based therapeutic strategies play an important role in cancer treatment. However, in situ, real-time and quantitative analysis of intracellular ROS in cancer treatment for drug screening is still a challenge. Herein we report one selective hydrogen peroxide (H2O2) electrochemical nanosensor, which is prepared by electrodeposition of Prussian blue (PB) and polyethylenedioxythiophene (PEDOT) onto carbon fiber nanoelectrode. With the nanosensor, we find that the level of intracellular H2O2 increases with NADH treatment and that increase is dose-dependent to the concentration of NADH. High-dose of NADH (above 10 mM) can induce cell death and intratumoral injection of NADH is validated for inhibiting tumor growth in mice. This study highlights the potential of electrochemical nanosensor for tracking and understanding the role of H2O2 in screening new anticancer drug. 相似文献
994.
Isothermal oxidation behavior of chromium with and without nanometric sol-gel CeO2 coating is studied at 1000℃ in air. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are used to examine the surface morphology and microstructure of their oxide films. It is found that ceria coating greatly improves the anti-oxidation property of chromium. Laser Raman spectrometer and X-ray diffraction spectrometer (XRD) are also used to study the stress level in oxide films formed on ceria-coated and ceria-free Cr. The difference in oxidation behavior is mainly attributed to the fact that ceria greatly reduces the growth speed and grain size of Cr2O3 film, and this fine grain-sized Cr2O3 film probably has better high temperature plasticity, i.e. oxide film can relieve parts of compressive stress by means of creeping. XRD and Raman testing results both show the stress declination due to nano-CeO2 application, and their deviation is analyzed conceming to the rare earth effect. 相似文献
995.
Sheng Jun Luo ;Wan Long Pan ;Ying Nan Chi ;Yan Qing Xu ;Kun Lin Huang ;Chang Wen Hu 《中国化学快报》2008,19(10):1147-1150
1-(1-Adamantylamino)-2,4,6-trinitrobenzene (1) as a potential energy material has been synthesized in excellent yield and characterized by FT-IR, 1H NMR and single crystallographic methods, and is thermally stable, decomposed in the range of 215- 72℃. 相似文献
996.
997.
Littlewood-Paley算子交换子在加权Herz型Hardy空间上的有界性 总被引:2,自引:1,他引:1
研究了Littlewood-Paley算子交换子gψ,b在加权Herz型Hardy空间上的性质,并证明了gψ,b在某些条件下是HKa,pq(ω1,ω2)到Ka,pq(ω1,ω2)和HKa,pq(ω1,ω2)到WKa,pq(ω1,ω2)上的有界算子. 相似文献
998.
Yu-Xing Yao Dr. Xiang Chen Nan Yao Jin-Hui Gao Dr. Gang Xu Jun-Fan Ding Chun-Liang Song Dr. Wen-Long Cai Prof. Chong Yan Prof. Qiang Zhang 《Angewandte Chemie (International ed. in English)》2023,62(4):e202214828
Extreme fast charging (XFC) of high-energy Li-ion batteries is a key enabler of electrified transportation. While previous studies mainly focused on improving Li ion mass transport in electrodes and electrolytes, the limitations of charge transfer across electrode–electrolyte interfaces remain underexplored. Herein we unravel how charge transfer kinetics dictates the fast rechargeability of Li-ion cells. Li ion transfer across the cathode–electrolyte interface is found to be rate-limiting during XFC, but the charge transfer energy barrier at both the cathode and anode have to be reduced simultaneously to prevent Li plating, which is achieved through electrolyte engineering. By unlocking charge transfer limitations, 184 Wh kg−1 pouch cells demonstrate stable XFC (10-min charge to 80 %) which is otherwise unachievable, and the lifetime of 245 Wh kg−1 21700 cells is quintupled during fast charging (25-min charge to 80 %). 相似文献
999.
Xiao-Yu Li Dr. Tao Wang Yu-Chen Cai Zhao-Dong Meng Jing-Wen Nan Dr. Jin-Yu Ye Prof. Dr. Jun Yi Prof. Dr. Dong-Ping Zhan Prof. Dr. Na Tian Prof. Dr. Zhi-You Zhou Prof. Dr. Shi-Gang Sun 《Angewandte Chemie (International ed. in English)》2023,62(14):e202218669
Proton transfer is crucial for electrocatalysis. Accumulating cations at electrochemical interfaces can alter the proton transfer rate and then tune electrocatalytic performance. However, the mechanism for regulating proton transfer remains ambiguous. Here, we quantify the cation effect on proton diffusion in solution by hydrogen evolution on microelectrodes, revealing the rate can be suppressed by more than 10 times. Different from the prevalent opinions that proton transport is slowed down by modified electric field, we found water structure imposes a more evident effect on kinetics. FTIR test and path integral molecular dynamics simulation indicate that proton prefers to wander within the hydration shell of cations rather than to hop rapidly along water wires. Low connectivity of water networks disrupted by cations corrupts the fast-moving path in bulk water. This study highlights the promising way for regulating proton kinetics via a modified water structure. 相似文献
1000.
Nan Zhang Ying Li Dr. Sanyang Han Dr. Ying Wei Huan Hu Ran Huo Dr. Chunbo Duan Dr. Jing Zhang Dr. Chunmiao Han Prof. Guohua Xie Prof. Hui Xu 《Angewandte Chemie (International ed. in English)》2023,62(27):e202305018
Clusters combine the advantages of organic molecules and inorganic nanomaterials, which are promising alternatives for optoelectronic applications. Nonetheless, recently emerged cluster light-emitting diodes require further excited state optimization of cluster emitters, especially to reduce population of the cluster-centered triplet quenching state (3CC). Here we report that redox-active ligands enhance reverse intersystem crossing (RISC) of Cu4I4 cluster for triplet-to-singlet conversion, and thermally activated delayed fluorescence (TADF) host can provide an external RISC channel. It indicates that the complementarity between TADF host and cluster in RISC transitions gives rise to 100 % triplet conversion efficiency and complete singlet exciton convergence, rendering 100-fold increased singlet radiation rate constant and tenfold decreased triplet non-radiation rate constant. We achieve a photoluminescence quantum yield of 99 % and a record external quantum efficiency of 29.4 %. 相似文献