全文获取类型
收费全文 | 8353篇 |
免费 | 1332篇 |
国内免费 | 1291篇 |
专业分类
化学 | 6201篇 |
晶体学 | 99篇 |
力学 | 665篇 |
综合类 | 94篇 |
数学 | 1127篇 |
物理学 | 2790篇 |
出版年
2024年 | 19篇 |
2023年 | 161篇 |
2022年 | 183篇 |
2021年 | 252篇 |
2020年 | 313篇 |
2019年 | 299篇 |
2018年 | 230篇 |
2017年 | 245篇 |
2016年 | 419篇 |
2015年 | 340篇 |
2014年 | 424篇 |
2013年 | 581篇 |
2012年 | 716篇 |
2011年 | 689篇 |
2010年 | 566篇 |
2009年 | 480篇 |
2008年 | 531篇 |
2007年 | 453篇 |
2006年 | 440篇 |
2005年 | 421篇 |
2004年 | 362篇 |
2003年 | 338篇 |
2002年 | 390篇 |
2001年 | 351篇 |
2000年 | 244篇 |
1999年 | 249篇 |
1998年 | 188篇 |
1997年 | 174篇 |
1996年 | 182篇 |
1995年 | 142篇 |
1994年 | 131篇 |
1993年 | 96篇 |
1992年 | 72篇 |
1991年 | 70篇 |
1990年 | 43篇 |
1989年 | 26篇 |
1988年 | 34篇 |
1987年 | 19篇 |
1986年 | 29篇 |
1985年 | 20篇 |
1984年 | 10篇 |
1983年 | 15篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1974年 | 1篇 |
1957年 | 3篇 |
1936年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
Cheng‐Shou Zhao Li Chen Yu‐Zhong Wang 《Journal of polymer science. Part A, Polymer chemistry》2008,46(17):5752-5759
A novel phosphorus‐containing thermotropic liquid crystalline copolyester with flexible spacers (P‐TLCP‐FS) was synthesized by melt transesterification from p‐acetoxybenzoic acid (p‐ABA), terephthalic acid (TPA), ethylene glycol, and acetylated 2‐(6‐oxid‐6H‐dibenz(c,e) (1,2) oxaphosphorin 6‐yl) 1,4‐benzenediol (AODOPB). The chemical structure and properties of the obtained P‐TLCP‐FS were characterized by Fourier‐transform infrared spectroscopy (FT‐IR), proton nuclear magnetic resonance spectroscopy (1H‐NMR), inherent viscosity measurements, differential scanning calorimetry (DSC), thermogravimetry (TGA), polarizing light microscopy (PLM), and X‐ray diffraction (XRD) analysis. P‐TLCP‐FS had inherent viscosities of 0.92–1.12 dL/g and exhibited low and wide mesophase temperatures, ranging from 185 to 330 °C, which can match with the processing temperatures of most conventional polymers and high flame retardancy with a limiting oxygen index value of 70% and UL‐94 V‐0 rating. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5752–5759, 2008 相似文献
942.
Summary Moment analysis is used to study two component perturbation chromatography with linear non-equilibrium adsorption. The interference between components is included through the adsorption equilibrium. In this work, the expressions for the first and second moments of two component pertubations have been obtained for the first time. They are just the vectorization of those for the single component system, and they clearly show the interference between components. These results could be applied to establish an experimental procedure to measure adsorption equilibrium and kinetic data. 相似文献
943.
A new method and corresponding numerical procedure are introduced to estimate scaling exponents of power-law degree distribution and hierarchical clustering func tion for complex networks. This method can overcome the biased and inaccurate faults of graphical linear fitting methods commonly used in current network research. Furthermore, it is verified to have higher goodness-of-fit than graphical methods by comparing the KS (Kolmogorov-Smirnov) test statistics for 10 CNN (Connecting Nearest-Neighbor)networks. 相似文献
944.
945.
946.
Yong Wang Qiang Fu Qijun Li Gong Zhang Kaizhi Shen Yu‐Zhong Wang 《Journal of Polymer Science.Polymer Physics》2002,40(18):2086-2097
For a more complete understanding of the toughening mechanism of polypropylene (PP)/ethylene‐propylene‐diene rubber (EPDM) blends, dynamic packing injection molding was used to control the phase morphology and rubber particle orientation in the matrix. The relative impact strength of the blends increased at low EPDM contents, and then a definite ductile–brittle (D–B) transition was observed when the EPDM content reached 25 wt %, at which point blends should fail in the ductile mode with conventional molding. Wide‐angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) were used to investigate the shear‐induced crystal structure, morphology, orientation, and phase separation of the blends. WAXD results showed that the observed D–B transition took place mainly for a constant crystal structure (α form). Also, no remarkable changes in the crystallinity and melting point of PP were observed by DSC. The highly oriented and elongated rubber particles were seen via SEM at high EPDM contents. Our results suggest that Wu's criterion is no longer valid when dispersed rubber particles are elongated and oriented. The possible fracture mechanism is discussed on the basis of the stress concentration in a filler‐dispersed matrix. It can be concluded that not only the interparticle distance but also the stress fields around individual particles play an important role in polymer toughening. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2086–2097, 2002 相似文献
947.
948.
949.
FuLinYAN AiXiaWANG ZhongJianJIA LeiHE 《中国化学快报》2003,14(12):1253-1254
A new isopropenyl benzofuran-type tetramer was isolated from the roots of ligularia stenocephala and its structure was established by spectroscopic methods. 相似文献
950.
Zhong‐Lu You 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(7):m339-m341
The title complex, [Cu(C11H14BrN2O)(N3)]n, is an interesting azide‐bridged polynuclear copper(II) compound. The CuII atom is five‐coordinated in a square‐pyramidal configuration, with one O and two N atoms of one Schiff base and one terminal N atom of a bridging azide ligand defining the basal plane, and another terminal N atom of another bridging azide ligand occupying the axial position. The {4‐bromo‐2‐[2‐(dimethylamino)ethyliminomethyl]phenolato}copper(II) moieties are linked by the bridging azide ligands, forming polymeric chains running along the b axis. Adjacent chains are further linked by weak Br⋯Br interactions into a sheet. 相似文献