全文获取类型
收费全文 | 1452篇 |
免费 | 32篇 |
国内免费 | 9篇 |
专业分类
化学 | 1086篇 |
晶体学 | 31篇 |
力学 | 28篇 |
数学 | 114篇 |
物理学 | 234篇 |
出版年
2020年 | 4篇 |
2019年 | 15篇 |
2017年 | 8篇 |
2016年 | 22篇 |
2015年 | 20篇 |
2014年 | 33篇 |
2013年 | 89篇 |
2012年 | 72篇 |
2011年 | 75篇 |
2010年 | 44篇 |
2009年 | 57篇 |
2008年 | 88篇 |
2007年 | 83篇 |
2006年 | 96篇 |
2005年 | 93篇 |
2004年 | 80篇 |
2003年 | 64篇 |
2002年 | 74篇 |
2001年 | 19篇 |
2000年 | 31篇 |
1999年 | 20篇 |
1998年 | 18篇 |
1997年 | 11篇 |
1996年 | 16篇 |
1995年 | 8篇 |
1994年 | 20篇 |
1993年 | 12篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 7篇 |
1988年 | 6篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 25篇 |
1984年 | 20篇 |
1983年 | 14篇 |
1982年 | 32篇 |
1981年 | 31篇 |
1980年 | 18篇 |
1979年 | 19篇 |
1978年 | 11篇 |
1977年 | 11篇 |
1976年 | 16篇 |
1975年 | 12篇 |
1974年 | 7篇 |
1973年 | 17篇 |
1972年 | 5篇 |
1970年 | 4篇 |
1968年 | 6篇 |
1967年 | 4篇 |
排序方式: 共有1493条查询结果,搜索用时 203 毫秒
971.
Hideo Fujikake Masashi Kuboki Takeshi Murashige Hiroto Sato Hiroshi Kikuchi Taiichiro Kurita Fumio Sato 《Liquid crystals》2004,31(7):989-992
This paper discusses thermal phase transitions in a nematic liquid crystal material, filling a highly strained porous polyolefin film. Ruptured and aligned polymer fibrils, whose minimum diameter reaches several tens of nm, formed polymer networks in the porous film. From observations of temperature-controlled composite films using a polarizing microscope, it was noted that the isotropic-to-nematic phase transition temperatures of submicron liquid crystal domains, located in or near molecularly aligned streak-like polymer areas, were significantly higher than those located at some distance from these areas. It was assumed that the highly aligned polymer chains in the fine fibrils promote the nematic phase of the liquid crystal. The stretched porous polymer, exhibiting spatial ordering on a submicron scale, is thus suitable for the control of thermal phase transitions in a liquid crystal. 相似文献
972.
A readout function of a reading light supplier (RLS) is demonstrated by reading out images from an optical addressable spatial light modulator (SLM). The RLS supplies reading light to the reading side of the SLM and transmits readout images from the SLM. The RLS consists of a fiber plate and a redirector which has micro conical-hollows. The RLS contrast, which is the intensity ratio of the reading light to the stray light, is 9.2 and the power efficiency of the reading light supply is about 5%. A writing pattern on the SLM is a checkered pattern of 5 mm×5 mm cells, and it is read out successfully using the RLS. The maximum contrast of the readout image is 1.9. 相似文献
973.
Hideo Itoh Tatsuya Yamada Bruno Houssay Seiji Mukal Shin-ichiro Uekusa 《Optical Review》1994,1(2):150-152
System stability of various membership functions and fuzzy control methods are compared by numerical simulations to determine the feasibility of optoelectronic fuzzy inference method. An inverted pendulum is used for the destination system. A Gaussian membership function is better than a triangular one. MIN operations of grade evaluation and modification of consequent membership functions are better than other operations. SUM operation of consequent operation is better than MAX operation. 相似文献
974.
The extraction of nickel chelates with β-diketones containing either alkyl or phenyl groups was examined in the absence and in the presence of ammonia in the aqueous solution, in order to define the effect of substituents and the coordinating effect of ammonia on the extraction. In the extraction of nickel chelates in the presence of ammonia, the extracted species were identified to be [NiA2(NH3)2] (A: β-diketone anion) and ammonia acts both as adduct-forming in the organic phase and as a masking reagent in the aqueous phase. 相似文献
975.
976.
Hideo Matsumura Vassil Neytchev Nelly Terezova Iana Tsoneva 《Colloids and surfaces. B, Biointerfaces》2004,33(3-4):243-249
Phospholipid liposomes that contain Ca ions in inside compartment were subjected to external alternating electric fields of square wave form at several frequencies: 10, 100 Hz, 1, 10, 100 kHz. The leakage of Ca ions from inside to bulk solution caused by the electric fields was detected by the fluorescence change due to Ca-Quin 2 (fluorescent dye) complex formation in the bulk aqueous solution. The temperature increments of the sample solution in the chamber were also measured. The amplitude of the electric field and time interval between application of the electric field were varied. The frequency dependency of both the leakage of Ca ion and the temperature increments was observed. It was observed that the efficiency of the leakage had a minimum at 1 kHz. The origin of the frequency dependency of the leakage is discussed, and it is concluded that the energy consumption on a microscopic scale in the liposome membrane zone can be the reason for membrane permeation in this experimental system. 相似文献
977.
Shin''ichiro Asayama Takashi Noguchi Hideo Ogawa 《International Journal of Infrared and Millimeter Waves》2003,24(7):1091-1099
The design and performance of a fixed-tuned W-band SIS mixer with a wide band IF of 4.0-7.5 GHz is presented. Waveguide-to-stripline transition of the SIS mixer is designed using the lumped-gap-source port provided by HFSSTM. Measured receiver noise temperature is less than 25 K in the frequency range of 95-120 GHz, with a minimum value of around 19 K achieved. Mixer noise temperature is determined to be about 8.5 K, which is around twice the quantum limit (i.e., 2hw/k). In spite of the high IF frequencies (f
0 = 6 GHz), the performance of the SIS receiver is comparable or even superior to those of the best mechanically-tunable waveguide SIS receivers at low IF frequencies (f
0 = 1.5 GHz). This result suggests that it is easy to design waveguide-to-stripline transitions without scale-model measurements. 相似文献
978.
Fuzzy regression analysis using neural networks 总被引:4,自引:0,他引:4
In this paper, we propose simple but powerful methods for fuzzy regression analysis using neural networks. Since neural networks have high capability as an approximator of nonlinear mappings, the proposed methods can be applied to more complex systems than the existing LP based methods. First we propose learning algorithms of neural networks for determining a nonlinear interval model from the given input-output patterns. A nonlinear interval model whose outputs approximately include all the given patterns can be determined by two neural networks. Next we show two methods for deriving nonlinear fuzzy models from the interval model determined by the proposed algorithms. Nonlinear fuzzy models whose h-level sets approximately include all the given patterns can be derived. Last we show an application of the proposed methods to a real problem. 相似文献
979.
980.
Seiichi Uesugi Hiroko Miki Morio Ikehara Hideo Iwahashi Yoshimasa Kyogoku 《Tetrahedron letters》1979,20(42):4073-4076
From the 1H NMR studies of various 2′-substituted 2′-deoxyadenosines, a relationship between electronegativity of substituents and conformation of the sugar moiety was elucidated. 相似文献