全文获取类型
收费全文 | 453332篇 |
免费 | 16857篇 |
国内免费 | 9918篇 |
专业分类
化学 | 215333篇 |
晶体学 | 5022篇 |
力学 | 17402篇 |
综合类 | 521篇 |
数学 | 44444篇 |
物理学 | 118151篇 |
无线电 | 79234篇 |
出版年
2022年 | 3817篇 |
2021年 | 5022篇 |
2020年 | 5195篇 |
2019年 | 4973篇 |
2018年 | 4721篇 |
2017年 | 4444篇 |
2016年 | 7660篇 |
2015年 | 7198篇 |
2014年 | 9315篇 |
2013年 | 20622篇 |
2012年 | 18053篇 |
2011年 | 20926篇 |
2010年 | 14063篇 |
2009年 | 14656篇 |
2008年 | 19458篇 |
2007年 | 19684篇 |
2006年 | 19004篇 |
2005年 | 17488篇 |
2004年 | 15278篇 |
2003年 | 13410篇 |
2002年 | 12942篇 |
2001年 | 14105篇 |
2000年 | 11603篇 |
1999年 | 10012篇 |
1998年 | 8601篇 |
1997年 | 8105篇 |
1996年 | 8105篇 |
1995年 | 7553篇 |
1994年 | 7090篇 |
1993年 | 6763篇 |
1992年 | 7057篇 |
1991年 | 6784篇 |
1990年 | 6195篇 |
1989年 | 5699篇 |
1988年 | 5794篇 |
1987年 | 4782篇 |
1986年 | 4602篇 |
1985年 | 6252篇 |
1984年 | 6219篇 |
1983年 | 5127篇 |
1982年 | 5439篇 |
1981年 | 5377篇 |
1980年 | 5099篇 |
1979年 | 5120篇 |
1978年 | 5116篇 |
1977年 | 5081篇 |
1976年 | 5009篇 |
1975年 | 4896篇 |
1974年 | 4749篇 |
1973年 | 4896篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
We summarize the results of our recent work on Bäcklund transformations (BTs), particularly focusing on the relation between BTs and infinitesimal symmetries. We present a BT for an associated Degasperis–Procesi (aDP) equation and its superposition principle and investigate the solutions generated by applying this BT. Following our general methodology, we use the superposition principle of the BT to generate the infinitesimal symmetries of the aDP equation. 相似文献
64.
A first‐principles‐based effective Hamiltonian is developed and employed to investigate finite‐temperature structural properties of a prototype of perovskite halides, that is CsPbI3. Such simulations, when using first‐principles‐extracted coefficients, successfully reproduce the existence of an orthorhombic Pnma state and its iodine octahedral tilting angles around room temperature. However, they also yield a direct transformation from Pnma to cubic upon heating, unlike measurements that reported the occurrence of an intermediate long‐range‐tilted tetragonal P4/mbm phase in‐between the orthorhombic and cubic phases. Such disagreement, which may cast some doubts about the extent to which first‐principle methods can be trusted to mimic hybrid perovskites, can be resolved by “only” changing one short‐range tilting parameter in the whole set of effective Hamiltonian coefficients. In such a case, some reasonable values of this specific parameter result in the predictions that i) the intermediate P4/mbm state originates from fluctuations over many different tilted states; and ii) the cubic phase is highly locally distorted and develops strong transverse antiphase correlation between first‐nearest neighbor iodine octahedral tiltings, before undergoing a phase transition to P4/mbm under cooling. 相似文献
65.
66.
Wenshu Chen Jiajun Gu Yongping Du Fang Song Fanxing Bu Jinghan Li Yang Yuan Ruichun Luo Qinglei Liu Di Zhang 《Advanced functional materials》2020,30(25)
Large‐scale production of hydrogen from water‐alkali electrolyzers is impeded by the sluggish kinetics of hydrogen evolution reaction (HER) electrocatalysts. The hybridization of an acid‐active HER catalyst with a cocatalyst at the nanoscale helps boost HER kinetics in alkaline media. Here, it is demonstrated that 1T–MoS2 nanosheet edges (instead of basal planes) decorated by metal hydroxides form highly active / heterostructures, which significantly enhance HER performance in alkaline media. Featured with rich / sites, the fabricated 1T–MoS2 QS/Ni(OH)2 hybrid (quantum sized 1T–MoS2 sheets decorated with Ni(OH)2 via interface engineering) only requires overpotentials of 57 and 112 mV to drive HER current densities of 10 and 100 mA cm?2, respectively, and has a low Tafel slope of 30 mV dec?1 in 1 m KOH. So far, this is the best performance for MoS2‐based electrocatalysts and the 1T–MoS2 QS/Ni(OH)2 hybrid is among the best‐performing non‐Pt alkaline HER electrocatalysts known. The HER process is durable for 100 h at current densities up to 500 mA cm?2. This work not only provides an active, cost‐effective, and robust alkaline HER electrocatalyst, but also demonstrates a design strategy for preparing high‐performance catalysts based on edge‐rich 2D quantum sheets for other catalytic reactions. 相似文献
67.
Wireless Personal Communications - The traditional simultaneous wireless information and power transfer (SWIPT) system uses a part of signals to decode information, and the other part is used for... 相似文献
68.
69.
70.