全文获取类型
收费全文 | 171137篇 |
免费 | 1766篇 |
国内免费 | 507篇 |
专业分类
化学 | 88287篇 |
晶体学 | 3039篇 |
力学 | 7154篇 |
综合类 | 3篇 |
数学 | 19514篇 |
物理学 | 55413篇 |
出版年
2020年 | 1398篇 |
2019年 | 1552篇 |
2018年 | 1980篇 |
2017年 | 2065篇 |
2016年 | 3184篇 |
2015年 | 1889篇 |
2014年 | 3112篇 |
2013年 | 7660篇 |
2012年 | 5748篇 |
2011年 | 6878篇 |
2010年 | 5021篇 |
2009年 | 5002篇 |
2008年 | 6534篇 |
2007年 | 6429篇 |
2006年 | 6076篇 |
2005年 | 5507篇 |
2004年 | 5094篇 |
2003年 | 4596篇 |
2002年 | 4452篇 |
2001年 | 5218篇 |
2000年 | 3861篇 |
1999年 | 2967篇 |
1998年 | 2481篇 |
1997年 | 2385篇 |
1996年 | 2240篇 |
1995年 | 2113篇 |
1994年 | 2091篇 |
1993年 | 2000篇 |
1992年 | 2304篇 |
1991年 | 2246篇 |
1990年 | 2193篇 |
1989年 | 2121篇 |
1988年 | 2119篇 |
1987年 | 2122篇 |
1986年 | 2019篇 |
1985年 | 2629篇 |
1984年 | 2684篇 |
1983年 | 2383篇 |
1982年 | 2492篇 |
1981年 | 2309篇 |
1980年 | 2285篇 |
1979年 | 2427篇 |
1978年 | 2463篇 |
1977年 | 2391篇 |
1976年 | 2436篇 |
1975年 | 2361篇 |
1974年 | 2328篇 |
1973年 | 2505篇 |
1972年 | 1623篇 |
1971年 | 1337篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
891.
892.
G. I. Malofeeva O. M. Petrukhin B. Ya. Spivakov E. V. Poteshkina 《Journal of Analytical Chemistry》2003,58(3):211-216
Conditions of the liquid–liquid and solid-phase extraction of metal chelates are compared. The analogy and differences in the behavior of chelates and the effect of stability and partition constants on the completeness of the extraction of metals are discussed. 相似文献
893.
894.
B. B. Damaskin O. A. Baturina V. A. Safonov N. V. Safonov 《Russian Journal of Electrochemistry》2003,39(6):685-691
Effect of the electrode potential on the coadsorption of two organic substances is studied using a set of two mixed Frumkin isotherms and a model of three parallel capacitors in conditions where in the absence of an electric field this system has seven solutions. It is shown that only four of these solutions may correspond to realizable adsorption states. Effect of the electrode potential on the number of possible solutions of the isotherm set, the number of realizable adsorption states, as well as on the composition and properties of a surface layer is considered. 相似文献
895.
896.
A systematic study of the efficiency of protons, Ni, Pd and Th as chemical modifiers for the determination of cadmium by electrothermal atomic absorption spectrometry (ETAAS) using fast temperature programs was made for platform atomization. A comparison was made in terms of the salt type, absorbance-time profiles and elimination of the sodium chloride interference. The results were adapted to develop a method for the ETAAS determination of cadmium in biological and environmental samples. The highest sensitivity to determine cadmium in biological and environmental samples was obtained using nickel (together with protons) as a chemical modifier. The accuracy of the method was tested by the determination of cadmium in different certified reference materials. The best detection limit and the characteristic mass of Cd were found to be 0.03 ng mL(-1) and 0.35 pg, respectively. 相似文献
897.
898.
The authors give error estimates, a Voronovskaya-type relation, strong converse results and saturation for the weighted approximation of functions on the real line with Freud weights by Bernstein-type operators. 相似文献
899.
V. A. Flyagin V. I. Khizhnyak V. N. Manuilov M. A. Moiseev A. B. Pavelyev V. E. Zapevalov N. A. Zavolsky 《International Journal of Infrared and Millimeter Waves》2003,24(1):1-17
Main results of experimental testing of the 140 GHz/1.5 MW coaxial gyrotron are summarized. High selective properties of the coaxial cavities and a possibility to increase considerably the efficiency of a coaxial gyrotron only by applying independently an appropriate voltage on its electrodes (without any design modification) have been confirmed. Successful uses of the two-potential connection scheme for the frequency step tuning and output power modulation in a coaxial gyrotron has been also demonstrated. 相似文献
900.
Conventionally, surface roughness is predominantly determined through the use of stylus instruments. However, there are certain limitations involved in the method, particularly when a test specimen, such as a silicon wafer, has a smooth mirror-like surface. Hence, it is necessary to explore alternative non-contact techniques. Light scattering has recently been gaining popularity as an optical technique to provide prompt and precise inspection of surface roughness. In this paper, the total integrated scattering (TIS) model is modified to retrieve parameters on surface micro-topography through light scattering. The applicability of the proposed modified TIS model is studied and compared with an atomic force microscope. Experimental results obtained show that the proposed technique is highly accurate for measuring surface roughness in the nanometer range. 相似文献