全文获取类型
收费全文 | 1113篇 |
免费 | 133篇 |
国内免费 | 228篇 |
专业分类
化学 | 937篇 |
晶体学 | 11篇 |
力学 | 49篇 |
综合类 | 12篇 |
数学 | 145篇 |
物理学 | 320篇 |
出版年
2024年 | 5篇 |
2023年 | 17篇 |
2022年 | 48篇 |
2021年 | 34篇 |
2020年 | 41篇 |
2019年 | 56篇 |
2018年 | 34篇 |
2017年 | 37篇 |
2016年 | 65篇 |
2015年 | 42篇 |
2014年 | 45篇 |
2013年 | 92篇 |
2012年 | 77篇 |
2011年 | 106篇 |
2010年 | 60篇 |
2009年 | 51篇 |
2008年 | 71篇 |
2007年 | 48篇 |
2006年 | 57篇 |
2005年 | 65篇 |
2004年 | 42篇 |
2003年 | 51篇 |
2002年 | 69篇 |
2001年 | 71篇 |
2000年 | 37篇 |
1999年 | 32篇 |
1998年 | 18篇 |
1997年 | 22篇 |
1996年 | 15篇 |
1995年 | 16篇 |
1994年 | 10篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1990年 | 11篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有1474条查询结果,搜索用时 0 毫秒
141.
Bao‐Zong Li Xun‐Gao Liu Yan‐Fen Peng Bao‐Long Li Yong Zhang 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(2):m41-m44
In the title complex, poly[cadmium(II)‐μ2‐1,4‐bis(1,2,4‐triazol‐1‐ylmethyl)benzene‐di‐μ2‐thiocyanato], [Cd(NCS)2(C12H12N6)]n, the CdII atom lies on an inversion centre in a distorted octahedral environment. Four N atoms from the thiocyanate and 1,4‐bis(1,2,4‐triazol‐1‐ylmethyl)benzene (bbtz) ligands occupy the equatorial positions, and two S atoms from symmetry‐related thiocyanate ligands occupy the axial positions. The benzene ring of the bbtz ligand lies about an inversion centre. Single thiocyanate bridges link the CdII atoms into two‐dimensional sheets containing novel 16‐membered [Cd4(μ‐NCS‐N:S)4] rings. The bbtz ligands further link these two‐dimensional sheets into an unprecedented covalent three‐dimensional network for the cadmium–thiocyanate system. 相似文献
142.
143.
本文通过对不同晶体结构Re_3W样品的点接触测量和对比研究,证实具有中心对称结构和非中心对称结构的Re_3W都是弱耦合Bardeen-Cooper-Schrieffer超导体,同时发现在两个相表面都可以形成很理想的点接触结,即电子通过界面时受到的非弹性散射很弱.将Re_3W样品置于大气环境近六个月后重新进行测量,仍然能够得到类似的结果,表明Re_3W具有很好的稳定性. Re_3W的这种优良特性,不仅可通过点接触实验得到的参数推算出Re_3W两个相的费米速度,而且提供了一种简单的方法,可以在点接触实验中利用Re_3W来印证针尖材料的费米速度和测量其自旋极化率等.作为尝试,本文用Re_3W/Ni点接触结测量了铁磁性金属Ni的自旋极化率,得到了与前人报道一致的结果. 相似文献
144.
The effects of toxicants on the populations for ann-dimensional food chain model in a polluted environment are studied. The thresholds between persistence and extinction of the populations are obtained as functions of model parameters and a time-varying chemical concentration. 相似文献
145.
Norman Lu Wen‐Han Tu Zong‐Wei Wu Yuh‐Sheng Wen Ling‐Kang Liu 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(6):o289-o291
As part of a homologous series of novel polyfluorinated bipyridyl (bpy) ligands, the title compound, C16H14F6N2O2, contains the smallest fluorinated group, viz. CF3. The molecule resides on a crystallographic inversion centre at the mid‐point of the pyridine Cipso—Cipso bond. Therefore, the bpy skeleton lies in an anti conformation to avoid repulsion between the two pyridyl N atoms. Weak intramolecular C—H...N and C—H...O interactions are observed, similar to those in related polyfluorinated bpy–metal complexes. A π–π interaction is observed between the bpy rings of adjacent molecules and this is probably a primary driving force in crystallization. Weak intermolecular C—H...N hydrogen bonding is present between one of the CF3CH2– methylene H atoms and a pyridyl N atom related by translation along the [010] direction, in addition to weak benzyl‐type C—H...F interactions to atoms of the terminal CF3 group. It is of note that the O—CH2CF3 bond is almost perpendicular to the bpy plane. 相似文献
146.
Kyukwan Zong Seung Il Shin Dong Ju Jeon Jung No Lee Eung K. Ryu 《Journal of heterocyclic chemistry》2000,37(1):75-78
3‐Aryl‐4‐methoxycarbonylisoxazoles were prepared from the reaction of a variety of substituted benzonitrile oxides with methyl 3‐(p‐nitrobenzoyloxy)acrylate in moderate to good yields. 相似文献
147.
Highly Effective Detection of Amitraz in Honey by Using Surface-Enhanced Raman Scattering Spectroscopy Coupled with Chemometric Methods 下载免费PDF全文
Xin-ming Nie Jing Wang Xun Wang Ya-ping Tian Si Chen Zhou-yang Long Cheng-hua Zong 《化学物理学报(中文版)》2019,32(4):444-450
As an effective and universal acaricide, amitraz is widely used on beehives against varroasis caused by the mite Varroa jacobsoni. Its residues in honey pose a great danger to human health. In this study, a sensitive, rapid, and environmentally friendly surface-enhanced Raman spectroscopy method (SERS) was developed for the determination of trace amount of amitraz in honey with the use of silver nanorod (AgNR) array substrate. The AgNR array substrate fabricated by an oblique angle deposition technique exhibited an excellent SERS activity with an enhancement factor of ∽107. Density function theory was employed to assign the characteristic peak of amitraz. The detection of amitraz was further explored and amitraz in honey at concentrations as low as 0.08 mg/kg can be identified. Specifically, partial least square regression analysis was employed to correlate the SERS spectra in full-wavelength with Camitraz to afford a multiple-quantitative amitraz predicting model. Preliminary results show that the predicted concentrations of amitraz in honey samples are in good agreement with their real concentrations. Compared with the conventional univariate quantitative model based on single peak’s intensity, the proposed multiple-quantitative predicting model integrates all the characteristic peaks of amitraz, thus offering an improved detecting accuracy and anti-interference ability. 相似文献
148.
149.
150.
A Biodegradable Polydopamine‐Derived Electrode Material for High‐Capacity and Long‐Life Lithium‐Ion and Sodium‐Ion Batteries 下载免费PDF全文
Tao Sun Zong‐jun Li Heng‐guo Wang Di Bao Fan‐lu Meng Prof. Xin‐bo Zhang 《Angewandte Chemie (International ed. in English)》2016,55(36):10662-10666
Polydopamine (PDA), which is biodegradable and is derived from naturally occurring products, can be employed as an electrode material, wherein controllable partial oxidization plays a key role in balancing the proportion of redox‐active carbonyl groups and the structural stability and conductivity. Unexpectedly, the optimized PDA derivative endows lithium‐ion batteries (LIBs) or sodium‐ion batteries (SIBs) with superior electrochemical performances, including high capacities (1818 mAh g?1 for LIBs and 500 mAh g?1 for SIBs) and good stable cyclabilities (93 % capacity retention after 580 cycles for LIBs; 100 % capacity retention after 1024 cycles for SIBs), which are much better than those of their counterparts with conventional binders. 相似文献