全文获取类型
收费全文 | 4671篇 |
免费 | 72篇 |
国内免费 | 10篇 |
专业分类
化学 | 3229篇 |
晶体学 | 21篇 |
力学 | 77篇 |
数学 | 961篇 |
物理学 | 465篇 |
出版年
2019年 | 36篇 |
2016年 | 73篇 |
2015年 | 52篇 |
2014年 | 35篇 |
2013年 | 130篇 |
2012年 | 96篇 |
2011年 | 150篇 |
2010年 | 108篇 |
2009年 | 120篇 |
2008年 | 154篇 |
2007年 | 153篇 |
2006年 | 163篇 |
2005年 | 141篇 |
2004年 | 122篇 |
2003年 | 121篇 |
2002年 | 109篇 |
2001年 | 65篇 |
2000年 | 81篇 |
1999年 | 65篇 |
1998年 | 62篇 |
1997年 | 59篇 |
1996年 | 72篇 |
1995年 | 79篇 |
1994年 | 61篇 |
1993年 | 68篇 |
1992年 | 100篇 |
1991年 | 99篇 |
1990年 | 81篇 |
1989年 | 78篇 |
1988年 | 61篇 |
1987年 | 69篇 |
1986年 | 71篇 |
1985年 | 93篇 |
1984年 | 94篇 |
1983年 | 90篇 |
1982年 | 89篇 |
1981年 | 109篇 |
1980年 | 64篇 |
1979年 | 83篇 |
1978年 | 77篇 |
1977年 | 95篇 |
1976年 | 69篇 |
1975年 | 84篇 |
1974年 | 89篇 |
1973年 | 68篇 |
1972年 | 58篇 |
1971年 | 48篇 |
1970年 | 39篇 |
1967年 | 32篇 |
1966年 | 30篇 |
排序方式: 共有4753条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Stefan Peterli Dieter Hubmann Urs Squin Helmut Mett Peter Traxler 《Helvetica chimica acta》1994,77(1):59-69
β-Nitrostyrene derivatives of adenosine 5′-glutarates are potent and selective bisubstrate-type inhibitors of the epidermal growth factor receptor protein tyrosine kinase (EGF-R PTK). In an attempt to improve the inhibitory activity, this type of compounds was modified with alkyl spacers of varying length between the nitrostyrene and the glutaryl units. The spacers consisted of 1, 3, 4, and 5 atoms to give compounds of the benzyl, oxyethyl, oxypropyl, and oxybutyl series, respectively (Schemes 1 and 2). Adenosine 5′-esters were prepared in the benzyl and oxypropyl series only. Compared to the compounds in the parent series without spacer (IC50 = 0.7–12 μM ), most of the modified compounds inhibited the EGF-R PTK only marginally or were inactive (IC50 ≥ 100 μM ). The only exceptions were the free acids 19 and 20 with IC50 values of ca. 5 μM . It is noteworthy that esterification of these two hydrogen glutarates with either MeOH or adenosine yielded inactive compounds, which is in contrast to the corresponding substances without spacers. 相似文献
5.
Helmut Schmidhammer Eva Scherb-Bukowiecki Thomas A. Mayer Peter Schnholzer 《Helvetica chimica acta》1994,77(6):1590-1594
The synthesis of benzazepine analogues of the opium alkaloid noscapine ( 1 ) is described. The benzazepines 2 and 3 were prepared starting from nornarceine ethyl ester ( 4 ; readily available from 1 ) in several steps. X-Ray analysis of compound 2 revealed that it is not a diastereosisomer mixture but a racemate of the threo-form and thus has the same configuration as 1 . 相似文献
6.
X-ray diffraction patterns of nanocrystalline Fe-Cu-Nb-Si-B (FINEMET) alloys reveal that bcc α-Fe/α-FeSi crystallites with
the average grain size of 20(5) nm are dispersed in amorphous matrix. Enhanced electron—electron interaction (EEI) and quantum
interference (QI) effects as well as electron-magnon (and/or electron-spin fluctuation) scattering turn out to be the main
mechanisms that govern the temperature dependence of resistivity. Of all the inelastic scattering processes, inelastic electron-phonon
scattering is the most effective mechanism to destroy phase coherence of electron wave functions. The diffusion constant,
density of states at the Fermi level and the inelastic scattering time have been estimated, for the first time, for the alloys
in question
Article presented at the International Symposium on Advances in Superconductivity and Magnetism: Materials, Mechanisms and
Devices, ASMM2D-2001, 25–28 September 2001, Mangalore, India. 相似文献
7.
The ferromagnetic shape memory alloy with nominal composition Ni54Fe19Ga27 is investigated by Ac susceptibility and resistivity measurements. The alloy shows long-range ferromagnetic order below 290 K. The anomaly due to the martensitic transition is observed in the susceptibility and resistivity data in the temperature range around 220 K, which is associated with clear thermal hysteresis. Minor hysteresis loop technique was used to investigate the phase coexistence across the martensitic transition, and our analysis indicate that both martensite and austenite phases mutually coexist in the region of hysteresis. 相似文献
8.
9.
10.
Hong-wei Zhang Shao-ying Zhang Bao-gen Shen Helmut Kronmüller 《Journal of magnetism and magnetic materials》2003,260(3):352-360
The magnetization behavior in nanocrystalline permanent magnets has been investigated using mean field Stoner–Wohlfarth model. The model is comparatively simple but allows the numerical treatment of extended nanostructures. The predominant intergrain exchange coupling is expressed by a mean field constant Nm in spite of no explicit relationship between Nm and the microstructure. By this model, the experimental phenomena, such as the remanence enhancement, the shape of demagnetization curve, the irreversible magnetization, the exchange bias field and their respective temperature dependence, can be well explained. The Nm dependence of magnetic properties has been extensively discussed in the present paper. 相似文献