全文获取类型
收费全文 | 8589篇 |
免费 | 254篇 |
国内免费 | 62篇 |
专业分类
化学 | 5817篇 |
晶体学 | 89篇 |
力学 | 250篇 |
综合类 | 1篇 |
数学 | 1331篇 |
物理学 | 1417篇 |
出版年
2022年 | 69篇 |
2021年 | 81篇 |
2020年 | 155篇 |
2019年 | 113篇 |
2018年 | 84篇 |
2017年 | 95篇 |
2016年 | 187篇 |
2015年 | 151篇 |
2014年 | 194篇 |
2013年 | 403篇 |
2012年 | 456篇 |
2011年 | 556篇 |
2010年 | 281篇 |
2009年 | 223篇 |
2008年 | 497篇 |
2007年 | 460篇 |
2006年 | 443篇 |
2005年 | 450篇 |
2004年 | 428篇 |
2003年 | 288篇 |
2002年 | 310篇 |
2001年 | 89篇 |
2000年 | 87篇 |
1999年 | 67篇 |
1998年 | 83篇 |
1997年 | 99篇 |
1996年 | 141篇 |
1995年 | 86篇 |
1994年 | 70篇 |
1993年 | 96篇 |
1992年 | 68篇 |
1991年 | 81篇 |
1990年 | 80篇 |
1989年 | 58篇 |
1988年 | 72篇 |
1987年 | 64篇 |
1986年 | 55篇 |
1985年 | 117篇 |
1984年 | 132篇 |
1983年 | 92篇 |
1982年 | 114篇 |
1981年 | 108篇 |
1980年 | 93篇 |
1979年 | 83篇 |
1978年 | 110篇 |
1977年 | 94篇 |
1976年 | 81篇 |
1975年 | 68篇 |
1974年 | 67篇 |
1973年 | 58篇 |
排序方式: 共有8905条查询结果,搜索用时 62 毫秒
31.
The synthesis of indole ring-fused benzazepinone series as latonduine derivatives has been developed via an intramolecular Heck reaction. The scope has been enlarged not only to indole moiety but also to pyrrolo and benzo[b]thiophene nuclei. Several derivatives prepared have been evaluated in vitro for their antiproliferative activities on breast cancer cell lines. Some of them showed promising cytotoxic activities. 相似文献
32.
33.
Hua Zhang Nabil A. Amro Robert Elghanian Joseph Fragala 《Applied Surface Science》2006,253(4):1960-1963
A method, combining micro-contact printing (μCP), wet chemical etching and reactive ion etching (RIE), is reported to fabricate microstructures on Si and SiOx. Positive and negative structures were generated based on different stamps used for μCP. The reproducibility of the obtained microstructures shows the methodology reported herein could be useful in Micro-Electro-Mechanical Systems (MEMS), optical and biological sensing applications. 相似文献
34.
The synthesis and characterization of a collagen mimetic dendrimer composed of the Gly-Pro-Nleu sequence is described. The dendrimer is built on a ‘first generation’ poly(amidoamine) core and is synthesized in 38% yield. This dendrimer exhibits a melting temperature of 25 °C, which is in between previously studied analogous molecules of identical sequence and length. 相似文献
35.
The incidence of the cutaneous malignant melanoma is increasing rapidly in the world [Ferlay J, Bray F, Pisani P, et al. GLOBOCAN 2000: Cancer incidence, mortality and prevalence worldwide, Version 1.0 IARC Cancer Base no. 5. Lyon: IARC Press, 2001]. The therapeutic address requires a method having high sensitivity and capability to diagnose such disease at an early stage. We introduce a new diagnostic method based on non-linear methodologies. In detail we suggest that fractal as well as noise and chaos dynamics are the most important components responsible for genetic instability of melanocytes. As consequence we introduce the new technique of the variogram and of fractal analysis extended to the whole regions of interest of skin in order to obtain parameters able to identify the malignant lesion. In a preliminary analysis, satisfactory results are reached. 相似文献
36.
37.
38.
39.
Joseph B. Schlenoff W. Jack Rink Lawrence Seger 《Physica C: Superconductivity and its Applications》1991,180(5-6):387-393
Single crystals and polycrystalline pellets of the high-temperature cuprate superconductor Bi2Sr2Ca1Cu2O8 were doped at room temperature by electrochemical reduction at > 95% Coulombic efficiency using lithium dopant ions in propylene carbonate electrolyte. Cyclic voltammetry and potential step measurements on single crystals suggest an unusual reduction mechanism, with a diffusion coefficient for Li+ in the c-axis direction of bulk superconductor of ca. 3 × 10−11 cm2s−1. Sintered pellets of polycrystalline powder could be doped more rapidly, with an apparent diffusion coefficient of 7 × 10−8 cm2s−1. X-ray susceptibility analysis show extensive disordering occurs on heavy Li doping, with a first-order transition from a crystalline/superconducting to an amorphous/non-superconducting phase. Single, crystals of Bi2Sr2Ca1Cu2O8 exhibited a color change on reduction from metallic gray to golden bronze. The reduced material was highly air-sensitive, forming a hydroxide surface film on exposure to ambient atmosphere. 相似文献
40.