全文获取类型
收费全文 | 82022篇 |
免费 | 413篇 |
国内免费 | 421篇 |
专业分类
化学 | 26938篇 |
晶体学 | 811篇 |
力学 | 6777篇 |
数学 | 32690篇 |
物理学 | 15640篇 |
出版年
2021年 | 42篇 |
2019年 | 50篇 |
2018年 | 10445篇 |
2017年 | 10283篇 |
2016年 | 6127篇 |
2015年 | 893篇 |
2014年 | 357篇 |
2013年 | 532篇 |
2012年 | 3945篇 |
2011年 | 10691篇 |
2010年 | 5719篇 |
2009年 | 6101篇 |
2008年 | 6842篇 |
2007年 | 9005篇 |
2006年 | 506篇 |
2005年 | 1581篇 |
2004年 | 1738篇 |
2003年 | 2123篇 |
2002年 | 1154篇 |
2001年 | 313篇 |
2000年 | 351篇 |
1999年 | 211篇 |
1998年 | 236篇 |
1997年 | 197篇 |
1996年 | 280篇 |
1995年 | 171篇 |
1994年 | 131篇 |
1993年 | 133篇 |
1992年 | 100篇 |
1991年 | 95篇 |
1990年 | 94篇 |
1989年 | 90篇 |
1988年 | 94篇 |
1987年 | 98篇 |
1986年 | 105篇 |
1985年 | 116篇 |
1984年 | 111篇 |
1983年 | 92篇 |
1982年 | 91篇 |
1981年 | 89篇 |
1980年 | 105篇 |
1979年 | 83篇 |
1978年 | 91篇 |
1977年 | 66篇 |
1976年 | 55篇 |
1975年 | 48篇 |
1973年 | 63篇 |
1914年 | 45篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
981.
K. V. Giri P. N. Bhargava H. Mauban R. J. Bruce und P. G. Denley 《Fresenius' Journal of Analytical Chemistry》1939,118(7-8):279-281
Ohne Zusammenfassung 相似文献
982.
983.
984.
Li-an Bian Peiguo Liu Qihui Zhou Chenxi Liu Hanqing Liu Song Zha 《Optical and Quantum Electronics》2018,50(5):220
Total absorption is realized theoretically in a graphene-outside-cavity resonator. The structure is composed of the FP-Fano hybrid resonance cavity. Changing the thickness of grating exciting Fano resonance, the absorption-mode number can be tuned effectively. For the focused double-mode absorption, the resonances behave insensitively with the variation of chemical potential of graphene. Varying the geometry of grating can control the coupling extent of two modes. Also, by manipulating the period number of two-side multilayers around graphene, the absorption, shift and number of modes are governed. 相似文献
985.
Melek Gul Dincmen Peter J. Hauser Nevin Cigdem Gursoy 《Plasma Chemistry and Plasma Processing》2016,36(5):1377-1391
In this study, three hydrophilic monomers; 2-acrylamido-2-methyl-1-propanesulfonic acid, 2-hydroxyethyl methacrylate, diallyldimethylammonium chloride (DADMAC) were selected and their performance as an antistatic finish on nylon 6,6 fabrics was investigated. A non-thermal, high density atmospheric pressure plasma was used to graft polymerize the monomers on nylon 6,6 fabrics. Fabrics were first treated with solutions of monomer in water, air dried and then treated with helium plasma to graft polymerize the monomer on the fiber surface. Surface resistivity values were measured before and after soxhlet extraction with water. Results showed that the DADMAC monomer provided better antistatic properties to fabrics. Further studies with DADMAC monomer were made; effects of plasma post exposure time, plasma pre-exposure time, plasma power, concentration of the monomer and existence of a crosslinker were investigated. Higher plasma power, higher concentration of the monomer and longer post exposure times all gave better antistatic properties to the nylon 6,6 fabrics. Acid dye staining, UV–Vis and FT-IR measurements were conducted and results confirmed a grafted poly-DADMAC layer on the fabric surface. 相似文献
986.
The chaotic dynamics of a Josephson junction with a ratchet potential and current-modulating damping are studied. Under the first-order approximation, we construct the general solution of the first-order equation whose boundedness condition contains the famous Melnikov chaotic criterion. Based on the general solution, the incomputability and unpredictability of the system’s chaotic behavior are discussed. For the case beyond perturbation conditions, the evolution of stroboscopic Poincaré sections shows that the system undergoes a quasi-periodic transition to chaos with an increasing intensity of the rf-current. Through a suitable feedback controlling strategy, the chaos can be effectively suppressed and the intensity of the controller can vary in a large range. It is also found that the current between the two separated superconductors increases monotonously in some specific parameter spaces. 相似文献
987.
988.
989.
In this paper, we propose a novel all-optical 2R (re-amplification and re-shaping) regenerator based on inducing nonlinear chirp over a continuous wave probe. The regenerator also performs continuous wave to pulsed wavelength conversion. The chirp is induced in a highly nonlinear fiber by the data modulated pulsed signal that is to be regenerated. Offset filtering is employed at the output of the highly nonlinear fiber to extract the frequencies generated as a result of chirping. The regenerator performance has been evaluated with the help of bit-error-rate plots and eye diagrams at different values of optical signal to noise ratios. Apart from re-shaping and re-amplification, inclusion of the regenerator results in better resilience to amplified spontaneous emission noise. 相似文献
990.
Li et al. (2015) claim that it is sufficient to use two harmonic functions to express the general solution of Stokes equations. In this paper, we demonstrate that this is not true in a general case and that we in fact need three scalar harmonic functions to represent the general solution of Stokes equations (Venkatalaxmi et al., 2004). 相似文献