全文获取类型
收费全文 | 1034篇 |
免费 | 28篇 |
国内免费 | 6篇 |
专业分类
化学 | 792篇 |
晶体学 | 20篇 |
力学 | 21篇 |
数学 | 34篇 |
物理学 | 201篇 |
出版年
2022年 | 7篇 |
2021年 | 13篇 |
2020年 | 13篇 |
2019年 | 17篇 |
2018年 | 7篇 |
2016年 | 18篇 |
2015年 | 24篇 |
2014年 | 17篇 |
2013年 | 38篇 |
2012年 | 46篇 |
2011年 | 47篇 |
2010年 | 43篇 |
2009年 | 35篇 |
2008年 | 67篇 |
2007年 | 57篇 |
2006年 | 55篇 |
2005年 | 52篇 |
2004年 | 46篇 |
2003年 | 36篇 |
2002年 | 36篇 |
2001年 | 28篇 |
2000年 | 25篇 |
1999年 | 15篇 |
1998年 | 14篇 |
1997年 | 18篇 |
1996年 | 14篇 |
1995年 | 6篇 |
1994年 | 13篇 |
1993年 | 15篇 |
1992年 | 22篇 |
1991年 | 7篇 |
1990年 | 14篇 |
1989年 | 13篇 |
1988年 | 11篇 |
1987年 | 10篇 |
1986年 | 16篇 |
1985年 | 16篇 |
1984年 | 13篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 12篇 |
1980年 | 14篇 |
1979年 | 13篇 |
1977年 | 5篇 |
1976年 | 8篇 |
1975年 | 5篇 |
1974年 | 6篇 |
1973年 | 8篇 |
1970年 | 5篇 |
1965年 | 7篇 |
排序方式: 共有1068条查询结果,搜索用时 19 毫秒
1.
2.
3.
Near-infrared photorefractivity in Cr-doped potassium sodium strontium barium niobate single crystal
J. Bergquist Y. Tomita M. Shibata 《Applied Physics A: Materials Science & Processing》1992,55(1):61-64
We report on the photorefractive properties of a Cr-doped (K1–x
Na
x
)2A–2 (Sr
y
Ba1–y
)2–A
Nb10O30 (x=0.586, y=0.659, A=1.12) single crystal in the near-infrared spectrum. The sample exhibits photorefractivity for wavelengths up to at least 840 nm where the steady-state two-beam coupling gain is found to be larger than 2 cm–1. Photorefractive gain and decay rate are measured as a function of wavelength, grating spacing and intensity. The wavelength dependence of gain fluctuations in two-beam coupling are also measured. 相似文献
4.
5.
Thiraporn Charoenraks Suchada Chuanuwatanakul Kensuke Honda Yoko Yamaguchi Orawon Chailapakul 《Analytical sciences》2005,21(3):241-245
The analysis of tetracycline, oxytetracyline, chlortetracycline and doxycycline by high-performance liquid chromatography with pulsed amperometric detection using an anodized boron-doped diamond thin film (BDD) electrode is originally reported. The analyses were carried out using the mobile phase, phosphate buffer (0.01 M, pH 2.5)-acetonitrile (80:20; v/v), on a C18 column (250 x 4.6 mm i.d., 5 microm) at a flow rate of 1.0 mL/min. The optimal PAD waveform parameters at the anodized BDD were 1.5 V (versus Ag/AgCl) detection potential (E(det)) for 290 ms (200 ms delay time and 90 ms integration time), 2.0 V (versus Ag/AgCl) oxidation potential (E(oxd)) for 200 ms oxidation time (t(oxd)) and 0.4 V (versus Ag/AgCI) reduction potential (E(red)) for 200 ms reduction time (t(red)). The proposed method showed the simultaneous determination of tetracycline, oxytetracyline, chlortetracycline and doxycycline with a linear range of 0.1 - 100 microg/mL, detection limits of 0.05 - 0.1 microg/mL and recoveries of 70.8 - 96.0%. The application of this method to real samples was demonstrated and validated using a shrimp sample. 相似文献
6.
According to the concept of the recognized visual space of illumination (RVSI) the lightness of an object surface is perceived in relation to its conceptualized size. To prove this proposition the lightness of gray test patches was judged when they were located at various positions inside an illuminated space composed of two rooms in the depth direction from a subject. No retinal image arrangement was changed in the test patch and its immediate surroundings, but the front room had walls, floors and furniture lower in lightness by the amount of N1.5 than the back room to make the RVSI of the former smaller despite the illuminance in the entire space being the same. The results showed that the apparent lightness of the patches was perceived higher by amount of about 13 in L units for the N4 test patch and about 20 for N6 when the patches were located in the front room, in accordance with the prediction. It was stressed that the experiment of lightness judgment should be conducted in a three dimensional space rather than two dimensional plane as done by several investigators. 相似文献
7.
8.
The effects of vitamin E (E) deficiency on the formation of aliphatic aldehydes in rat plasma and liver were studied. Three-week-old Wistar male rats were fed either an E supplemented diet (2-ambo-alpha-tocopheryl acetate 20 mg/kg diet, designated as E supplemented diet group) or an E deficient diet (E deficient diet group). After 8 weeks, n-hexanal and (E)-4-hydroxy-2-nonenal (4-HN) in the plasma of the E deficient diet group were found to be 2.0 and 2.5-fold greater than those of the E supplemented diet group, respectively. The contents of aldehydes such as n-pentanal, n-hexanal, 4-HN in the liver were also significantly higher in the E deficient diet group than in the E supplemented diet group. These results indicate that some aldehydes, arising possibly from lipid peroxides, are produced and detected in the plasma and liver of rats under the condition like E deficiency. In this study we further found that the activity of the liver aldehyde dehydrogenase (ALDH, EC 1.2.1.3) was significantly changed; 5 and 8 weeks after the start it was lower in the E deficient diet group when compared to that in the E supplemented diet group. The decrease of enzyme activity was related to the increase of aldehydes such as n-hexanal in the liver. the aldehyde increase in the plasma of the E deficient diet group was thought to raise the injury of cells, namely, a strong hemolysis on erythrocytes prepared from the blood of rats fed the E deficient diet. 相似文献
9.
10.
T. Takahashi S. Uchida H. Hayashi S. Matsuoka K. Tomita N. Kurosawa 《Journal of Radioanalytical and Nuclear Chemistry》2007,272(3):451-454
For the assessment of a public impact caused by radionuclides released from nuclear facilities, a dynamic compartment model
was developed for prediction of behavior of radioiodine in air, paddy field and rice plant system. The transfer coefficients
among compartments were determined by some experimental data and assumptions for each chemical form of iodine. A verification
of the model was carried out by some case studies. 相似文献