全文获取类型
收费全文 | 31106篇 |
免费 | 4996篇 |
国内免费 | 4707篇 |
专业分类
化学 | 23385篇 |
晶体学 | 523篇 |
力学 | 1537篇 |
综合类 | 361篇 |
数学 | 3626篇 |
物理学 | 11377篇 |
出版年
2024年 | 109篇 |
2023年 | 563篇 |
2022年 | 1052篇 |
2021年 | 1157篇 |
2020年 | 1253篇 |
2019年 | 1294篇 |
2018年 | 1117篇 |
2017年 | 1162篇 |
2016年 | 1498篇 |
2015年 | 1530篇 |
2014年 | 1876篇 |
2013年 | 2380篇 |
2012年 | 2885篇 |
2011年 | 2933篇 |
2010年 | 2248篇 |
2009年 | 2136篇 |
2008年 | 2263篇 |
2007年 | 2064篇 |
2006年 | 1921篇 |
2005年 | 1547篇 |
2004年 | 1120篇 |
2003年 | 925篇 |
2002年 | 920篇 |
2001年 | 793篇 |
2000年 | 675篇 |
1999年 | 563篇 |
1998年 | 402篇 |
1997年 | 347篇 |
1996年 | 310篇 |
1995年 | 287篇 |
1994年 | 269篇 |
1993年 | 198篇 |
1992年 | 171篇 |
1991年 | 161篇 |
1990年 | 144篇 |
1989年 | 98篇 |
1988年 | 84篇 |
1987年 | 61篇 |
1986年 | 74篇 |
1985年 | 57篇 |
1984年 | 29篇 |
1983年 | 27篇 |
1982年 | 28篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1977年 | 7篇 |
1973年 | 7篇 |
1971年 | 8篇 |
1936年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
含k-次增生算子的Ishikawa迭代的收敛性问题 总被引:9,自引:0,他引:9
主要研究了非线性方程x Tx=f的Ishikawa迭代解.其中T为k-次增生的或增生的,并在一致光滑和任意的实Banach空间分别研究了上述方程的带误差的Ishikawa迭代解,从而推广了已知的一些结果。 相似文献
62.
Xiaohua He Hailiang Zhang Deyue Yan Xiayu Wang 《Journal of polymer science. Part A, Polymer chemistry》2003,41(18):2854-2864
A series of side‐chain liquid‐crystalline (LC) homopolymers of poly[6‐(4‐methoxy‐4′‐oxy‐azobenzene) hexyl methacrylate] with different degrees of polymerization were synthesized by atom transfer radical polymerization (ATRP), which were prepared with a wide range of number‐average molecular weights from 5.1 × 103 to 20.6 × 103 with narrow polydispersities of around 1.17. Thermal investigation showed that the homopolymers exhibit two mesophases, a smectic phase, and a nematic phase, and the phase‐transition temperatures of the homopolymers increase clearly with increasing molecular weights. A series of novel LC coil triblock copolymers with narrow polydispersities was synthesized by ATRP, and their thermotropic phase behavior was investigated with differential scanning calorimetry and polarized optical microscopy. The LC coil triblocks were designed to have an LC conformation of poly[6‐(4‐methoxy‐4′‐oxy‐azobenzene) hexyl methacrylate] with a wide range of molecular weights from 3.5 × 103 to 1.7 × 104 and the coil conformation of poly(ethylene glycol) (PEG) (number‐average molecular weight: 6000 or 12,000) segment. Their characterization was investigated with 1H NMR, Fourier transform infrared spectra, and gel permeation chromatography. Triblock copolymers exhibited a crystalline phase, a smectic phase, and a nematic phase. The phase‐transition temperatures from the smectic to nematic phase and from the nematic to isotropic phase increased, and the crystallization of PEG depressed with increasing molecular weight of the LC block. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2854–2864, 2003 相似文献
63.
This paper studies a supply chain consisting of two suppliers and one retailer in a spot market, where the retailer uses the
newsvendor solution as its purchase policy, and suppliers compete for the retailer’s purchase. Since each supplier’s bidding
strategy affects the other’s profit, a game theory approach is used to identify optimal bidding strategies. We prove the existence
and uniqueness of a Nash solution. It is also shown that the competition between the supplier leads to a lower market clearing
price, and as a result, the retailer benefits from it. Finally, we demonstrate the applicability of the obtained results by
deriving optimal bidding strategies for power generator plants in the deregulated California energy market.
Supported in part by RGC (Hong Kong) Competitive Earmarked Research Grants (CUHK4167/04E and CUHK4239/03E), a Distinguished
Young Investigator Grant from the National Natural Sciences Foundation of China, and a grant from Hundred Talents Program
of the Chinese Academy of Sciences. 相似文献
64.
Chongyi Wan Shiming Liu Rongqing Tan Jin Wu Jinwen Zhou Yan Lv Yanning Yu Hua Yang 《Optics & Laser Technology》2004,36(8):2389-649
A high average power, high-repetition-rate TEA CO2 laser employing printed-circuit-board preionizer is described. The power scaling of this preionization configuration has been demonstrated. The average output power reaches 3.6 kW at pulse repetition rate of 180 pps. Furthermore, the scaling-up ability of the rotating spark gap as high-voltage switch for high-average-power gas laser has been validated. 相似文献
65.
66.
67.
本文在Q-正则Loewner空间中用环模不等式刻划了拟对称映射.另外,在 Q-维Ahlfors-David正则空间中建立了拟对称映射作用下的Grotzsch-Teichmuller型 模不等式,它是通过伸张系数的积分平均来表示. 相似文献
68.
本文从速率方程出发,讨论了类锂铝复合等离子体的激发态结构,衰减常数,反转率和小信号增益等表征介质增益特性的物理量以及它们随电子温度,电子密度和光子逃逸几率的变化。找到了进行类锂铝离子通过复合机制产生X光激光设计应创造的等离子体状态目标区域。还讨论了这些物理量随原子序数变化的定标律。 相似文献
69.
The purpose of this paper is to present general approaches for bounding some multi-stage stochastic programs from above. The results are based on restricting the solution set, such that the remaining multi-stage stochastic program is easy to solve. An example where the methods can be applied is presented.Supported in part by NATO Collaborative Research Grant No. 0785/87. 相似文献
70.
利用微扰展开技术推导出变参数波振器的小信号增益两个近似求积表达式并将其计算结果与数值模拟结果进行了比较,二者吻合很好。利用近似解析式对小信号增益进行了初步探讨,得到了电子入射能量可低于初始谐振能,能散度允许范围受波振器设计影响以及降低锥度改变率可提高小信号增益等新结论。 相似文献