全文获取类型
收费全文 | 27348篇 |
免费 | 1029篇 |
国内免费 | 143篇 |
专业分类
化学 | 19917篇 |
晶体学 | 212篇 |
力学 | 500篇 |
数学 | 3317篇 |
物理学 | 4574篇 |
出版年
2023年 | 179篇 |
2021年 | 373篇 |
2020年 | 494篇 |
2019年 | 484篇 |
2018年 | 320篇 |
2017年 | 273篇 |
2016年 | 740篇 |
2015年 | 629篇 |
2014年 | 767篇 |
2013年 | 1241篇 |
2012年 | 1641篇 |
2011年 | 1824篇 |
2010年 | 1052篇 |
2009年 | 877篇 |
2008年 | 1518篇 |
2007年 | 1432篇 |
2006年 | 1404篇 |
2005年 | 1313篇 |
2004年 | 1152篇 |
2003年 | 868篇 |
2002年 | 910篇 |
2001年 | 449篇 |
2000年 | 392篇 |
1999年 | 387篇 |
1998年 | 377篇 |
1997年 | 330篇 |
1996年 | 337篇 |
1995年 | 306篇 |
1994年 | 319篇 |
1993年 | 323篇 |
1992年 | 278篇 |
1991年 | 188篇 |
1990年 | 220篇 |
1989年 | 185篇 |
1988年 | 200篇 |
1987年 | 183篇 |
1986年 | 165篇 |
1985年 | 278篇 |
1984年 | 267篇 |
1983年 | 182篇 |
1982年 | 204篇 |
1981年 | 187篇 |
1980年 | 188篇 |
1979年 | 166篇 |
1978年 | 198篇 |
1977年 | 185篇 |
1974年 | 167篇 |
1966年 | 191篇 |
1964年 | 153篇 |
1961年 | 154篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Thomas M. F. Case G. S. Bland J. Herring A. D. F. Stirling W. G. Tixier S. Boni P. Ward R. C. C. Wells M. R. Langridge S. 《Hyperfine Interactions》2002,141(1-4):471-476
Hyperfine Interactions - Multilayers of Ce/Fe and U/Fe were fabricated by sputtering and studied by X-ray diffraction and reflectivity, Mössbauer spectroscopy and polarised neutron... 相似文献
72.
Shyam K. Singh Oliver S. Fetzer John B. Hynes Thomas C. Williams 《Journal of heterocyclic chemistry》1991,28(5):1459-1461
Nitration of 2-amino-4-oxo-(3H)-5-trifluoromethylquinazoline is shown to occur exclusively at C6 as determined from an analysis of long range 1H and 19F scalar couplings to ring carbons. Nitration of 2-amino-4-oxo-(3H)-5-fluoroquinazoline is found to occur both at C6 and C8 as evident from an analysis of the 19F and 1H couplings of the ring protons. 相似文献
73.
74.
75.
A combined-modality treatment program consisting of botulinum toxin injection (Botox) and voice therapy was used to treat 17 subjects diagnosed with adductor spasmodic dysphonia (ADD SD). Ten subjects with ADD SD served as the control and were given Botox only. Voice therapy after Botox injection was directed toward reducing the hyperfunctional vocal behaviors, primarily glottal overpressure at voice onset and anterior-posterior squeezing. The results indicated that subjects who underwent combined-modality treatment maintained significantly higher mean airflow rates for significantly longer periods. Moreover, there was a carryover effect in these patients when they received Botox only. Adductor spasmodic dysphonia is treated most effectively when intrinsic laryngeal muscle spasms are reduced or eliminated by Botox injection and extrinsic hyperfunctional vocal behaviors are treated with voice therapy 相似文献
76.
As pan of a biomimetic approach towards me marine triterpene teurilene (2), the synthesis of the chiral diepoxide 3 is described. Aiming at the synthesis of the squalene tetraepoxide 1, double Sharpless epoxidation led to the intermediate bisglycidic alcohol 7 being subject to a stereochemical analysis. 相似文献
77.
78.
79.
Simon Thomas 《Archive for Mathematical Logic》1998,37(7):483-493
We study the relationship between the cofinality of the infinite symmetric group and the cardinal invariants and . In particular, we prove the following two results.
Theorem 0.1
It is consistent with
ZFC
that there exists a simple
$P_{\omega_{1}}$
-point and that
$c(Sym(\omega)) = \omega_{2} = 2^{\omega}$
.
Theorem 0.2
If there exist both a simple
$P_{\omega_{1}}$
-point and a
$P_{\omega_{2}}$
-point, then
$c(Sym(\omega)) = \omega_{1}$
.
Received: 7 March 1996 相似文献
80.
We consider a spatially distributed hybrid system consisting of a convection/reaction system in which the reaction switches discontinuously in time between modes, independently at each spatial point on reaching “switching thresholds”. The model involves a novel formulation for evolution of the free boundary between the modal regions. 相似文献