全文获取类型
收费全文 | 39144篇 |
免费 | 5412篇 |
国内免费 | 4335篇 |
专业分类
化学 | 28251篇 |
晶体学 | 504篇 |
力学 | 1988篇 |
综合类 | 293篇 |
数学 | 4843篇 |
物理学 | 13012篇 |
出版年
2024年 | 110篇 |
2023年 | 701篇 |
2022年 | 1207篇 |
2021年 | 1320篇 |
2020年 | 1448篇 |
2019年 | 1397篇 |
2018年 | 1217篇 |
2017年 | 1120篇 |
2016年 | 1650篇 |
2015年 | 1685篇 |
2014年 | 2035篇 |
2013年 | 2718篇 |
2012年 | 3228篇 |
2011年 | 3476篇 |
2010年 | 2373篇 |
2009年 | 2302篇 |
2008年 | 2514篇 |
2007年 | 2291篇 |
2006年 | 2098篇 |
2005年 | 1798篇 |
2004年 | 1425篇 |
2003年 | 1152篇 |
2002年 | 1186篇 |
2001年 | 917篇 |
2000年 | 818篇 |
1999年 | 777篇 |
1998年 | 635篇 |
1997年 | 583篇 |
1996年 | 615篇 |
1995年 | 497篇 |
1994年 | 470篇 |
1993年 | 408篇 |
1992年 | 389篇 |
1991年 | 338篇 |
1990年 | 280篇 |
1989年 | 236篇 |
1988年 | 204篇 |
1987年 | 154篇 |
1986年 | 169篇 |
1985年 | 182篇 |
1984年 | 115篇 |
1983年 | 70篇 |
1982年 | 74篇 |
1981年 | 60篇 |
1980年 | 54篇 |
1979年 | 60篇 |
1978年 | 40篇 |
1976年 | 37篇 |
1974年 | 40篇 |
1973年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
31.
Lin Zhengyan 《数学学报(英文版)》1989,5(4):289-296
In the paper, we give the almost sure limiting behaviour of the increments of partial sums of a-mixing sequence when the moment generating functions do not exist. The results obtained are close to those for an independent sequence provided that the mixing coefficients tend to zero rapidly enough.The Project Supported by National Natural Science Foundation of China. 相似文献
32.
Poly(ethylene terephthalate) film was used as supporter for preparation of polyamide layer. The most convenient method of preparation was described. This layer can be cut into any size and its sensitivity is higher than the glass plate supported layer. Twenty aromatic nitro compounds were used to show the behavior of polyester film based polyamide layer. 相似文献
33.
Chang-Shou Lin 《Communications in Mathematical Physics》1987,111(2):161-166
A conjecture about the nodal line of a second eigenfunction states that the nodal line of a second eigenfunction divides the domain by intersecting with the boundary of transversely, where is a bounded convex domain ofR
2. We prove this conjecture provided has a symmetry. Also, we prove the multiplicity of the second eigenvalue is two at most provided is a bounded convex domain ofR
2.Supported in part by NSF DMS 84-09447Home Institution: Department of Mathematics, University of California, San Diego, La Jolla, CA 92093, USA 相似文献
34.
35.
36.
FFC-1离子交换纤维对酸碱有害气体吸附性能的研究 总被引:8,自引:0,他引:8
系统考察了不同直径及反离子形式的FFC-1聚羧酸离子交换纤维对酸碱有害气体的穿透吸附,各种温、湿度条件下的吸水率,以及作为有害气体吸附滤除材料的重复使用与再生性能。研究表明:FFC-1纤维直径的减小有利于提高对有害气体的动态吸附容量。在体系温度、相对湿度分别为15℃、50%时,以3D腈纶为起始原料的钠型FFC-1离子交换纤维的吸水率≥350mg/g.纤维;对SO2的穿透吸附容量可达200mg/g.纤维。FFC-1离子交换纤维具有良好的重复使用与再生能力,经20次再生循环使用后,纤维交换容量未见明显变化。 相似文献
37.
Lin Z 《Chemical Society reviews》2002,31(4):239-245
Transition metal-silane complexes containing metal-eta 2-H-Si coordination display different structural and bonding characteristics in comparison to other sigma-complexes, such as dihydrogen and alkane (agostic) complexes. The different characteristics can be related to the strong sigma*-accepting properties of the eta 2-silane ligand(s) because of the weaker H-Si sigma bond. Various examples of metal-silane complexes have been reviewed and their structural stabilities have been systematically discussed. Silyl-hydride complexes having substantial silyl-hydrido interactions have also been emphasized. 相似文献
38.
The vibrational distribution of CO produced from the following two electronic-to-vibrational energy transfer reactions: have been determined by means of infrared resonance absorption measurements employing a cw CO laser. The CO molecules formed in both reactions were found to be vibrationally excited up to the limits of available electronic energies carried by the excited atoms. A similar result was also observed in the Br(42P) + CO reaction, in which absorption occurred only in the 1 → 2 band. For the O* + CO reaction the efficiency of E → V energy transfer was determined to be 16%. Our present results were found to be inconsistent with the impulsive (half-collision) model. 相似文献
39.
[reaction: see text] A molecular shuttle containing an alpha-CD macrocycle, an azobenzene unit, and two different fluorescent naphthalimide units was synthesized. The cis-trans photoisomerization of the azobenzene unit resulted in the motion of the CD macrocycle on the track. Because of the easy regulation and full reversibility of the fluorescence change of the two stopper units, the molecular shuttle could be used as a molecular storage medium or switch with all-optical inputs and outputs. 相似文献
40.
Novel chiral bisbinaphthyl compounds have been synthesized for the enantioselective fluorescent recognition of mandelic acid. By introducing dendritic branches to the chiral receptor unit, the fluorescence signals of the receptors are significantly amplified because of the light-harvesting effect of the dendritic structure. This has greatly increased the sensitivity of the sensors in the fluorescent recognition. Study of the three generation sensors demonstrates that the generation zero sensor is the best choice for the recognition of mandelic acid because of its greatly increased fluorescence signal over the core and its high enantioselectivity. This sensor is potentially useful for the high throughput screening of chiral catalysts for the asymmetric synthesis of alpha-hydroxycarboxylic acids. 相似文献