全文获取类型
收费全文 | 3563篇 |
免费 | 280篇 |
国内免费 | 12篇 |
专业分类
化学 | 1969篇 |
晶体学 | 18篇 |
力学 | 79篇 |
数学 | 173篇 |
物理学 | 619篇 |
无线电 | 997篇 |
出版年
2024年 | 5篇 |
2023年 | 43篇 |
2022年 | 66篇 |
2021年 | 84篇 |
2020年 | 79篇 |
2019年 | 100篇 |
2018年 | 66篇 |
2017年 | 70篇 |
2016年 | 150篇 |
2015年 | 116篇 |
2014年 | 143篇 |
2013年 | 258篇 |
2012年 | 271篇 |
2011年 | 272篇 |
2010年 | 188篇 |
2009年 | 173篇 |
2008年 | 248篇 |
2007年 | 227篇 |
2006年 | 218篇 |
2005年 | 178篇 |
2004年 | 143篇 |
2003年 | 136篇 |
2002年 | 140篇 |
2001年 | 75篇 |
2000年 | 75篇 |
1999年 | 39篇 |
1998年 | 43篇 |
1997年 | 35篇 |
1996年 | 44篇 |
1995年 | 35篇 |
1994年 | 19篇 |
1993年 | 21篇 |
1992年 | 17篇 |
1991年 | 13篇 |
1990年 | 10篇 |
1989年 | 6篇 |
1988年 | 2篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1981年 | 3篇 |
1979年 | 2篇 |
1976年 | 5篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1969年 | 1篇 |
1968年 | 2篇 |
1963年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有3855条查询结果,搜索用时 15 毫秒
1.
2.
Sung Hwan Koo Dong Jun Li Taeyeong Yun Dong Sung Choi Kyung Eun Lee Gil Yong Lee Youngtak Oh Joonwon Lim Suchithra Padmajan Sasikala Ho Jin Lee In Ho Kim Hong Ju Jung Rishabh Jain Sang Ouk Kim 《Particle & Particle Systems Characterization》2019,36(7)
Efficient water electrolysis catalyst is highly demanded for the production of hydrogen as a sustainable energy fuel. It is reported that cobalt derived nanoparticle (CoS2, CoP, CoS|P) decorated reduced graphene oxide (rGO) composite aerogel catalysts for highly active and reliable hydrogen evolution reaction electrocatalysts. 7 nm level cobalt derived nanoparticles are synthesized over graphene aerogel surfaces with excellent surface coverage and maximal expose of active sites. CoS|P/rGO hybrid aerogel composites show an excellent catalytic activity with overpotential of ≈169 mV at a current density of ≈10 mA cm?2. Accordingly, efficient charge transfer is attained with Tafel slope of ≈52 mV dec?1 and a charge transfer resistance (Rct) of ≈12 Ω. This work suggests a viable route toward ultrasmall, uniform nanoparticles decorated graphene surfaces with well‐controlled chemical compositions, which can be generally useful for various applications commonly requiring large exposure of active surface area as well as robust interparticle charger transfer. 相似文献
3.
Ahn Jaeshin Stromsmoe Keith A. Lawson Ronald P. W. 《Industrial Electronics, IEEE Transactions on》1985,(4):405-409
A microprocessor-based system with 32 A/D, 24 D/A, and 16 ac load controllers, has been designed and built to monitor and control an ion beam thin-film deposition system. The A/D and D/A channels have electrical isolation of 7.5 kV between channels and between input and output. The microprocessor system keeps the ion beam deposition parameters stable for extended periods of operation and it is proposed as a means to greatly simplify switching from one deposition species to another to grow thin multilayer or alloy films. 相似文献
4.
In this paper, we shall find the uniquerational price associated with the exchange option. Also, we find the decomposition of Snell envelope and value function of the American exchange option. 相似文献
5.
A 0.9 V 92 dB Double-Sampled Switched-RC Delta-Sigma Audio ADC 总被引:1,自引:0,他引:1
Min Gyu Kim Gil-Cho Ahn Hanumolu P.K. Sang-Hyeon Lee Sang-Ho Kim Seung-Bin You Jae-Whui Kim Temes G.C. Un-Ku Moon 《Solid-State Circuits, IEEE Journal of》2008,43(5):1195-1206
A 0.9 V third-order double-sampled delta-sigma audio ADC is presented. A new method using a combination of a switched-RC technique and a floating switched-capacitor double-sampling configuration enabled low-voltage operation without clock boosting or bootstrapping. A three-level quantizer with simple dynamic element matching was used to improve linearity. The prototype IC implemented in a 0.13 CMOS process achieves 92 dB DR, 91 dB SNR and 89 dB SNDR in a 24 kHz audio signal bandwidth, while consuming 1.5 mW from a 0.9 V supply. The prototype operates from 0.65 V to 1.5 V supply with minimal performance degradation. 相似文献
6.
Burn‐in is a widely used method to improve the quality of products or systems after they have been produced. In this paper, we consider the problem of determining the optimal burn‐in time and optimal work size maximizing the long‐run average amount of work saved per time unit in the computer applications. Assuming that the underlying lifetime distribution of the computer has an initially decreasing or/and eventually increasing failure rate function, an upper bound for the optimal burn‐in time is derived for each fixed work size and a uniform (with respect to the burn‐in time) upper bound for the optimal work size is also obtained. Furthermore, it is shown that a non‐trivial lower bound for the optimal burn‐in time can be derived if the underlying lifetime distribution has a large initial failure rate. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
7.
In this paper, by extending Kucera's idea to the function field case, we obtain several determinant formulas involving the real class number and the relative class number of any subfield of cyclotomic function fields. We also provide several examples using these determinant formulas.
8.
We examine several interesting relationships and expressions involving Fourier-Feynman transform, convolution product and
first variation for functionals in the Fresnel class F(B) of an abstract Wiener space B. We also prove a translation theorem and Parseval's identity for the analytic Feynman integral.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
9.
Jun‐Hwan Ahn Choon‐Hwa Lee Yeong‐Deuk Shin Jae‐Suk Lee 《Journal of polymer science. Part A, Polymer chemistry》2004,42(4):933-940
To study living anionic polymerization, 3‐(triethylsilyl)propyl isocyanate (TEtSPI) monomer was synthesized by hydrosilylation of allylamine with triethylsilane and treatment of the resulting amine with triphosgene. The polymerization of TEtSPI was performed with sodium naphthalenide (Na‐Naph) as an initiator and in the absence and presence of sodium tetraphenylborate (NaBPh4) as an additive in tetrahydrofuran (THF) at ?78 and at ?98 °C. A highly stabilized amidate anion for living polymerization of isocyanates was generated for the first time with the combined effect of the bulky substituent and the shielding action of the additive NaBPh4, extending the living character at least up to 120 min at ?98 °C. Even the anion could exist at ?78 °C for 10 min. A block copolymer, poly(n‐hexyl isocyanate)‐b‐poly[(3‐triethylsilyl)propyl isocyanate]‐b‐poly(n‐hexyl isocyanate), was synthesized with quantitative yields and controlled molecular weights via living anionic polymerization in THF at ?78 °C for TEtSPI and ?98 °C for n‐hexyl isocyanate, respectively, with Na‐Naph with three times of NaBPh4 as a common ion salt. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 933–940, 2004 相似文献
10.