全文获取类型
收费全文 | 14647篇 |
免费 | 2827篇 |
国内免费 | 2584篇 |
专业分类
化学 | 11084篇 |
晶体学 | 356篇 |
力学 | 776篇 |
综合类 | 168篇 |
数学 | 1388篇 |
物理学 | 6286篇 |
出版年
2024年 | 60篇 |
2023年 | 314篇 |
2022年 | 629篇 |
2021年 | 719篇 |
2020年 | 760篇 |
2019年 | 762篇 |
2018年 | 628篇 |
2017年 | 654篇 |
2016年 | 804篇 |
2015年 | 888篇 |
2014年 | 1076篇 |
2013年 | 1356篇 |
2012年 | 1520篇 |
2011年 | 1513篇 |
2010年 | 1105篇 |
2009年 | 1031篇 |
2008年 | 1143篇 |
2007年 | 921篇 |
2006年 | 830篇 |
2005年 | 643篇 |
2004年 | 499篇 |
2003年 | 345篇 |
2002年 | 301篇 |
2001年 | 248篇 |
2000年 | 222篇 |
1999年 | 192篇 |
1998年 | 130篇 |
1997年 | 98篇 |
1996年 | 122篇 |
1995年 | 80篇 |
1994年 | 79篇 |
1993年 | 73篇 |
1992年 | 56篇 |
1991年 | 53篇 |
1990年 | 39篇 |
1989年 | 38篇 |
1988年 | 20篇 |
1987年 | 17篇 |
1986年 | 30篇 |
1985年 | 22篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1957年 | 5篇 |
1937年 | 1篇 |
1936年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
Zhitian Liu Lei Wang Junwu Chen Feng Wang Xiaoying Ouyang Yong Cao 《Journal of polymer science. Part A, Polymer chemistry》2007,45(5):756-767
2,5‐Bis(2‐bromofluorene‐7‐yl)silole was prepared by a modified one‐pot synthesis with a reverse addition procedure, from which novel silole‐containing polyfluorenes with binary random and alternating structures (silole contents between 4.5 and 25% and high Mw up to 509 kDa were successfully synthesized. The well‐defined repeating unit of the alternating copolymer comprises a terfluorene and a silole ring. Optoelectronic properties including UV absorption, electrochemistry, photoluminescence (PL), and electroluminescence (EL) of the copolymers were examined. The different excitation energy transfers from fluorene to silole of the copolymers in solution and in the solid state were compared. The films of the copolymers showed silole‐dominant green emissions with high absolute PL quantum yields up to 83%. EL devices of the copolymers with a configuration of ITO/PEDOT/copolymer/Ba/Al displayed exclusive silole emissions peaked at around 543 nm and the highest EL efficiency was achieved with the alternating copolymer. Using the alternating copolymer and poly(9,9‐dioctylfluorene) as the blend‐type emissive layer, a maximum external quantum efficiency of 1.99% (four times to that of the neat film) was realized, which was a high efficiency so far reported for silole‐containing polymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 756–767, 2007 相似文献
12.
13.
14.
15.
The fission barrier for ^240pu is investigated beyond the second saddle point in the potentiM energy surface by the constrained relativistic mean field method with the newly proposed parameter set PK1. The microscopic correction for the centre-of-mass motion is essentiM to provide the correct potential energy surface. The shell effects that stabilize the nuclei against the fission is also investigated by the Strutinsky method. The shapes for the ground state, fission isomer and saddle-points, etc, are studied in detail. 相似文献
16.
17.
18.
YBa2Cu3O7-δ and Tl2Ba2CaCu2O8 thin films for microwave filters were synthesized by pulsed laser deposition and the two-step thalliation process. Substrate
quality requirements and the relation of thin film morphology, microstructure with microwave surface resistance were discussed. 相似文献
19.
ZhengBin Zhang Chunying Liu Peifeng Li Zhenzhen Wu Cai Lin Huawei Huang Lei Xing Liansheng Liu 《Frontiers of Chemistry in China》2006,1(1):86-97
Many food algae and red tide algae were cultivated in the f/2 medium, and the nitric oxide (NO) concentration of the medium
and the cell density were determined. The experiments on algae were conducted when different concentrations of NO were added
into the medium using two methods. The results show that low concentrations of NO were self-produced by marine algae during
the exponential growth period and were about nmol/L level. But at the end of the period, i.e., 2 or 3 days before the cell
density reaches the maximum, an NO peak appeared, with the NO concentration reaching 10 nmol/L. The NO threshold concentration
exists according to the influence of exogenous NO on the marine phytoplankton growth. One type is the threshold concentration
that can promote algae growth, and its value is between 10 and 1 nmol level, or even lower. The other type can inhibit the
phytoplankton growth, which is about μmol level or higher. The results indicate that red tide algae are far more sensitive
to NO than are food algae. The fundamental experimental outcome above may provide a new clue for red tide chemical forecast
by inspecting the NO change. 相似文献
20.