全文获取类型
收费全文 | 8529篇 |
免费 | 1510篇 |
国内免费 | 963篇 |
专业分类
化学 | 6353篇 |
晶体学 | 76篇 |
力学 | 499篇 |
综合类 | 45篇 |
数学 | 1055篇 |
物理学 | 2974篇 |
出版年
2024年 | 18篇 |
2023年 | 208篇 |
2022年 | 310篇 |
2021年 | 330篇 |
2020年 | 464篇 |
2019年 | 394篇 |
2018年 | 346篇 |
2017年 | 277篇 |
2016年 | 408篇 |
2015年 | 420篇 |
2014年 | 511篇 |
2013年 | 628篇 |
2012年 | 769篇 |
2011年 | 823篇 |
2010年 | 546篇 |
2009年 | 489篇 |
2008年 | 482篇 |
2007年 | 456篇 |
2006年 | 469篇 |
2005年 | 355篇 |
2004年 | 277篇 |
2003年 | 226篇 |
2002年 | 278篇 |
2001年 | 160篇 |
2000年 | 169篇 |
1999年 | 179篇 |
1998年 | 130篇 |
1997年 | 127篇 |
1996年 | 139篇 |
1995年 | 108篇 |
1994年 | 97篇 |
1993年 | 64篇 |
1992年 | 66篇 |
1991年 | 57篇 |
1990年 | 47篇 |
1989年 | 42篇 |
1988年 | 37篇 |
1987年 | 18篇 |
1986年 | 25篇 |
1985年 | 21篇 |
1984年 | 12篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 6篇 |
1980年 | 1篇 |
1957年 | 3篇 |
1935年 | 1篇 |
1931年 | 1篇 |
1930年 | 3篇 |
1922年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
二氧化碳多相催化加氢的新进展 总被引:4,自引:0,他引:4
就近年来关于CO2活化、几个重要的CO2多相催化加氢反应及廉价氢的供给的研究进展进行综述。参考文献34篇。 相似文献
73.
This is the second part of a paper which deals with the advantages and disadvantages of relative instrumental neutron activation
analysis concerning traceability and uncertainty, and the current scope and possible future extensions of neutron activation
analysis as a primary ratio method. The first part of this paper has been published in this Journal [1].
Received: 19 March 2001 Accepted: 2 October 2001 相似文献
74.
75.
Electroosmotic flow (EOF) is a phenomenon associated with the movement of an aqueous solution induced by the application of an electric field in microchannels. The characteristics of EOF depend on the nature of the surface potential, i.e., whether it is uniform or nonuniform. In this paper, a lattice Boltzmann model (LBM) combined with the Poisson-Boltzmann equation is used to simulate flow field in a rectangular microchannel with nonuniform (step change) surface potentials. The simulation results indicate that local circulations can occur near a heterogeneous region with nonuniform surface potentials, in agreement with those by other authors. Largest circulations, which imply a highest mixing efficiency due to convection and short-range diffusion, were found when the average surface potential is zero, regardless of whether the distribution of the heterogeneous patches is symmetric or asymmetric. In this work, we have illustrated that there is a trade-off between the mixing and liquid transport in EOF microfluidics. One should not simply focus on mixing and neglect liquid transport, as performed in the literature. Excellent mixing could lead to a poor transport of electroosmotic flow in microchannels. 相似文献
76.
Yu-Peng Tian Ming-Liang Zhang Zhang-Jun Hu Han-Mei Hu Jie-Ying Wu Xuan-Jun Zhang Sheng-Yi Zhang Xu-Tang Tao Min-Hua Jiang He-Ping Chen Suchada Chantrapromma Hoong-Kun Fun 《Transition Metal Chemistry》2005,30(7):778-785
A new Schiff base 4-[N-hydroxyethyl-N-(methyl)amino]benzaldehyde S-methyl dithiocarbazate (HL, where H is a dissociable proton) and the ruthenium complex [Ru(bpy)2L]PF6 (bpy = 2,2′-bipyridine) have been synthesized. The structural determinations of the ligand and its ruthenium complex, by
X-ray crystallography, show that the ligand is coordinated as a monoanionic bidentate N, S-donor, forming a four-member chelate
ring with a bite angle of 65.91°. The complex shows intense MLCT transitions in the visible region. Fluorescent and electrochemical
properties have been also studied. The complex in DMF solution exhibited a strong two-photon absorption (t.p.a.) at 532 nm
nanosecond laser pulses. The t.p.a. coefficient β, t.p.a. cross-section σ and the third-order optical nonlinearity χ(3) of the complex and the ligand have been determined by the Z-scan technique. 相似文献
77.
78.
Hai-Bin Tian Duan-Zhi Yin Lan Zhang Li-Hua Wang Chun-Fu Zhang Jun-Ling Li Wei Zhou Chun-Ying Wu Yong-Xian Wang 《Journal of Radioanalytical and Nuclear Chemistry》2004,262(2):383-389
The compound 3-{[4-(4-[18F]fluorophenyl)methyl]piperazin-1-yl}-methyl-1H-pyrrolo[2,3-b]pyridine ([18F]3), which is an analogue of L-745,870 binding D4
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
79.
通过分子设计,合成了一种新颖的双β-二酮有机配体9-乙基-3,6-二(乙酰基-3-苯甲酰基)咔唑(H2L)及其铕配合物,红外光谱和电子光谱表明Eu^3+与H2L发生配位。配合物的溶液荧光光谱不仅有613 nm处的中心离子Eu^3+的特征红光,属^5D0→^7F2跃迁带,还有445nm处配体的宽带蓝色发光,属H2L^*→H2L跃迁带,而配合物的光致发光光谱只有611 nm处为中心离子Eu^3+的特征红光,属^5D0→^7F2跃迁带,峰形尖锐,半峰宽仅7 nm,单色性好,表明该固体铕双β-二酮配合物是一种潜在的红色发光材料。 相似文献
80.