全文获取类型
收费全文 | 100254篇 |
免费 | 17951篇 |
国内免费 | 10557篇 |
专业分类
化学 | 68739篇 |
晶体学 | 1037篇 |
力学 | 6253篇 |
综合类 | 643篇 |
数学 | 11279篇 |
物理学 | 40811篇 |
出版年
2024年 | 370篇 |
2023年 | 2193篇 |
2022年 | 3595篇 |
2021年 | 3845篇 |
2020年 | 4281篇 |
2019年 | 3920篇 |
2018年 | 3586篇 |
2017年 | 3203篇 |
2016年 | 5086篇 |
2015年 | 4882篇 |
2014年 | 5890篇 |
2013年 | 7480篇 |
2012年 | 9060篇 |
2011年 | 9263篇 |
2010年 | 6213篇 |
2009年 | 5973篇 |
2008年 | 6456篇 |
2007年 | 5694篇 |
2006年 | 5313篇 |
2005年 | 4270篇 |
2004年 | 3298篇 |
2003年 | 2646篇 |
2002年 | 2562篇 |
2001年 | 2224篇 |
2000年 | 1831篇 |
1999年 | 2072篇 |
1998年 | 1736篇 |
1997年 | 1668篇 |
1996年 | 1644篇 |
1995年 | 1385篇 |
1994年 | 1209篇 |
1993年 | 1059篇 |
1992年 | 905篇 |
1991年 | 832篇 |
1990年 | 682篇 |
1989年 | 534篇 |
1988年 | 397篇 |
1987年 | 327篇 |
1986年 | 338篇 |
1985年 | 275篇 |
1984年 | 160篇 |
1983年 | 126篇 |
1982年 | 104篇 |
1981年 | 60篇 |
1980年 | 49篇 |
1979年 | 17篇 |
1975年 | 2篇 |
1959年 | 2篇 |
1957年 | 31篇 |
1936年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
103.
Because of package, a single FBG has dual Bragg wavelength. One is sensitive to stress and the other is sensitive to temperature. By using the special mechanism, the wavelengths can be tuned by stress and temperature respectively. 相似文献
104.
The effects of partial substitution of Mn for Co on the thermoelectric properties of Ca3MnxCo4−xO9 (x=0, 0.03, 0.9), prepared by sol-gel process, were investigated at the temperatures from 380 K down to 5 K. The results indicate that the substitution of Mn for Co results in increase in thermopower at temperatures >∼80 K, and substantial (23-31% at 300 K) decrease in lattice thermal conductivity in the whole temperature range investigated. The temperature behavior of ZT suggests that Ca3MnxCo4−xO9 with light Mn substitution would be a promising candidate for high-temperature thermoelectric applications. 相似文献
105.
106.
HaiHuiXIE XiaoYiWEI JiDongWANG MeiFangLIU RenZhouYANG 《中国化学快报》2003,14(6):588-590
A New Annonaceous acetogenin,squamostolide(1),was isolated from the seeds of Annona squamosa.Its structure was elucidated based on spectroscopic methods and comparison with known compounds.It is the first example of Annonaceous acetogenin with each of the two ends of the aliphatic chain bearing a γ-lactone.Thenew compound exhibited cytotoxic activity in vitro against bel-7402 and CNE2 human tumor cell lines. 相似文献
107.
ChunXiaLI YingXiaLI LingBoYU HuaZHANG SiftDongCHU HuaShiGUAN 《中国化学快报》2003,14(8):776-778
A convenient synthetic route was developed for the synthesis of the novel glycolipids: 1,2-di-O-acyl-3-O-(2‘-acylamide-2‘-denxy-ct-D-glucopyranosyl)-sn-glycerols. 10 new compounds of glycolipids with different acyl groups were obtained. 相似文献
108.
Summary Our purpose is to extend results due to P. Chandra and L. Leindler concerning the order of approximation by means of Fourier series for functions belonging to generalized Lipschitz-classes. 相似文献
109.
A facile, rapid and regioselective method for the 1-O-deacylation of peracylated glycopyranoses is described which occurs under mild conditions by absorption onto alumina using microwave irradiation. 相似文献
110.
This work is devoted to near-optimal controls of large-scale discrete-time nonlinear dynamic systems driven by Markov chains; the underlying problem is to minimize an expected cost function. Our main goal is to reduce the complexity of the underlying systems. To achieve this goal, discrete-time control models under singularly-perturbed Markov chains are introduced. Using a relaxed control representation, our effort is devoted to finding near-optimal controls. Lumping the states in each irreducible class into a single state gives rise to a limit system. Applying near-optimal controls of the limit system to the original system, near-optimal controls of the original system are derived. 相似文献