全文获取类型
收费全文 | 31622篇 |
免费 | 5059篇 |
国内免费 | 4585篇 |
专业分类
化学 | 24235篇 |
晶体学 | 465篇 |
力学 | 1507篇 |
综合类 | 273篇 |
数学 | 3048篇 |
物理学 | 11738篇 |
出版年
2024年 | 109篇 |
2023年 | 615篇 |
2022年 | 1185篇 |
2021年 | 1220篇 |
2020年 | 1300篇 |
2019年 | 1311篇 |
2018年 | 1156篇 |
2017年 | 1145篇 |
2016年 | 1577篇 |
2015年 | 1682篇 |
2014年 | 2079篇 |
2013年 | 2565篇 |
2012年 | 3023篇 |
2011年 | 3110篇 |
2010年 | 2287篇 |
2009年 | 2035篇 |
2008年 | 2252篇 |
2007年 | 2038篇 |
2006年 | 1829篇 |
2005年 | 1456篇 |
2004年 | 1069篇 |
2003年 | 867篇 |
2002年 | 884篇 |
2001年 | 721篇 |
2000年 | 589篇 |
1999年 | 529篇 |
1998年 | 382篇 |
1997年 | 334篇 |
1996年 | 276篇 |
1995年 | 239篇 |
1994年 | 255篇 |
1993年 | 207篇 |
1992年 | 180篇 |
1991年 | 139篇 |
1990年 | 115篇 |
1989年 | 121篇 |
1988年 | 63篇 |
1987年 | 56篇 |
1986年 | 56篇 |
1985年 | 42篇 |
1984年 | 26篇 |
1983年 | 15篇 |
1982年 | 19篇 |
1981年 | 10篇 |
1980年 | 19篇 |
1979年 | 8篇 |
1976年 | 11篇 |
1974年 | 9篇 |
1973年 | 7篇 |
1957年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
355nm Nd∶YAG激光在H_2中的高效一级斯托克斯转换 总被引:1,自引:1,他引:0
对脉冲Nd∶YAG激光(355 nm)在H2和H2∶He-Ar混合气体中的受激拉曼散射(SRS)进行了研究。在0.5 MPa的氢气中,同时测量到从二级反斯托克斯到三级斯托克斯的多波长输出,其总转化效率达88%;而高压下只剩下一级和二级斯托克斯输出,其中二级斯托克斯最大能量转化效率达44%(对应量子效率为63%)。由于高级斯托克斯的竞争,纯氢气中一级斯托克斯的最大能量转换效率不超过43%。通过向3 MPa氢气中掺入2 MPaAr气后,很好地抑制了二级斯托克斯的产生,从而获得了能量转换效率高达71%(对应量子效率为83%)的一级斯托克斯输出。对四波混频和级联受激拉曼散射在氢气多级斯托克斯产生中的作用以及惰性气体对它们的影响进行了讨论。 相似文献
3.
GAO Jing ZHOU Xiaohua CHEN Xun Chongqing University Chemical Engineering Department Chongqing China 《Chinese Journal of Reactive Polymers》2006,(2)
1. INTRODUCTION In the process of coking plant, about 30%~35% sulfur is transformed to H2S and some other sulfide, which form impurity in coal gas together with NH3 and HCN. Only 0.1% H2S containing in air can lead to die, so it is very important to carry on desulphurization and decyanation with coal gas [1~3]. Currently desulphurization and decyanation craft technique have Dry Oxidation Technology, Wet Oxidation Technology and Liquid Absorption Technology [2] three main kinds. The… 相似文献
4.
Theoretical and experimental investigations on the performance of micro-perforated -panel absorbers are reviewed in this paper. By reviewing recent research work, this paper reveals a relationship between the maximum absorption coefficient and the limit of the absorption frequency bandwidth. It has been demonstrated that the absorption frequency bandwidth can be extended up to 3 or 4 octaves as the diameters of the micro-holes decrease. This has become possible with the development of the technologies for manufacturing micro-perforated panels, such as laser drilling, powder metallurgy, welded meshing and electro-etching to form micrometer order holes. In this paper, absorption characteristics of such absorbers in random fields and in high sound intensity are discussed both theoretically and experimentally. A new absorbing structure based on micro-perforated-panel absorbers demonstrate experimentally high sound absorption capability. This review shows that the micro-perforated-panel absorber has potentials to be one of ideal absorbing materials in the 21st century. 相似文献
5.
Solitary waves and their bifurcations of KdV like equation with higher order nonlinearity 总被引:3,自引:1,他引:2
We investigate the KdV like equation with higher order nonlinearity ut + a(1 +bun)unux + uxxx = 0with n ≥ 1, a, b ∈ R and α≠ 0. The bifurcations and explicit expressions of solitary wave solutions for theequation are discussed by using the bifurcation method and qualitative theory of dynamical systems. Thebifurcation diagrams, existence and number of the solitary waves are given. 相似文献
6.
7.
Fei Chang Dongheng Zhang Haijian Yang Haibin Song 《Journal of organometallic chemistry》2004,689(5):936-946
The synthesized 1-aryliminomethylenylnaphthalen-2-ol derivatives reacted with nickel chloride to form bis(1-aryliminomethylenylnaphthalen-2-oxy)nickel complexes. All resultant compounds were structurally characterized by elemental analyses, IR and H NMR, and the structures of the formed complexes were elucidated by X-ray crystal structure analysis. The complexes show high catalytic activities for the vinyl polymerization of norbornene in the presence of methylaluminoxane. The catalytic activity variations have been followed by gas chromatography through monitoring the conversion of norbornene. 相似文献
8.
9.
10.
Nickel complexes 1–4 ligated with 2,9-disubstituted-1,10-phenanthroline were synthesized and characterized by FT-IR spectra and elemental analysis.
The molecular structure of complex 2 was confirmed by X-ray crystal diffraction analysis. Activated with methylaluminoxane (MAO), those complexes showed moderate
activities for ethylene oligomerization.
Published in Kinetika i Kataliz, 2007, Vol. 48, No. 5, pp. 710–714.
This article was submitted by the authors in English. 相似文献