全文获取类型
收费全文 | 25508篇 |
免费 | 4334篇 |
国内免费 | 3829篇 |
专业分类
化学 | 19450篇 |
晶体学 | 382篇 |
力学 | 1432篇 |
综合类 | 283篇 |
数学 | 2749篇 |
物理学 | 9375篇 |
出版年
2024年 | 81篇 |
2023年 | 438篇 |
2022年 | 798篇 |
2021年 | 855篇 |
2020年 | 923篇 |
2019年 | 1021篇 |
2018年 | 841篇 |
2017年 | 778篇 |
2016年 | 1241篇 |
2015年 | 1246篇 |
2014年 | 1567篇 |
2013年 | 1992篇 |
2012年 | 2248篇 |
2011年 | 2460篇 |
2010年 | 1756篇 |
2009年 | 1760篇 |
2008年 | 1888篇 |
2007年 | 1723篇 |
2006年 | 1453篇 |
2005年 | 1234篇 |
2004年 | 1077篇 |
2003年 | 837篇 |
2002年 | 955篇 |
2001年 | 783篇 |
2000年 | 689篇 |
1999年 | 466篇 |
1998年 | 365篇 |
1997年 | 277篇 |
1996年 | 304篇 |
1995年 | 241篇 |
1994年 | 237篇 |
1993年 | 203篇 |
1992年 | 162篇 |
1991年 | 138篇 |
1990年 | 112篇 |
1989年 | 97篇 |
1988年 | 67篇 |
1987年 | 60篇 |
1986年 | 55篇 |
1985年 | 55篇 |
1984年 | 38篇 |
1983年 | 28篇 |
1982年 | 9篇 |
1981年 | 18篇 |
1980年 | 9篇 |
1979年 | 20篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1976年 | 9篇 |
1975年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
This study describes the preparation of polypyrrole (PPy)/multiwalled carbon nanotube (MWNT) composites by in situ chemical oxidative polymerization. Various ratios of MWNTs, which served as hard templates, were first dispersed in aqueous solutions with the surfactant cetyltrimethylammonium bromide to form micelle/MWNT templates and overcome the difficulty of MWNTs dispersing into insoluble solutions of pyrrole monomer, and PPy was then synthesized via in situ chemical oxidative polymerization on the surface of the templates. Raman spectroscopy, Fourier transform infrared (FTIR), field‐emission scanning electron microscopy (FESEM), and high‐resolution transmission electron microscopy (HRTEM) were used to characterize the structure and morphology of the fabricated composites. Structural analysis using FESEM and HRTEM showed that the PPy/MWNT composites were core (MWNT)–shell (PPy) tubular structures. Raman and FTIR spectra of the composites were almost identical to those of PPy, supporting the idea that MWNTs served as the core in the formation of a coaxial nanostructure for the composites. The conductivities of these PPy/MWNT composites were about 150% higher than those of PPy without MWNTs. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1413–1418, 2006 相似文献
82.
The electrochemical behavior of gatifloxacin (GTFX) and its interaction with natural calf thymus DNA (ctDNA) is investigated by differential pulse voltammetry (DPV) on a carbon paraffined electrode. According to the suggested electrochemical equation, a binding constant of 1.7058 x 10(5) (mol L(-1))(-1) and binding sizes s = 3.09 (base pairs) of GTFX with ctDNA are obtained by nonlinear fit analysis of electrochemical data. The results demonstrate that GTFX has the properties of an intercalative binder. 相似文献
83.
A new Co–Fe-based ferromagnetic bulk metallic glass (BMG) was synthesized by copper mould casting method. The thermal stability and crystallization processes were investigated by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The soft magnetic behavior was studied by DC magnetic measurements. The high glass formation ability was interpreted in terms of the effective suppression of nucleation and growth of the intermetallic compounds which appear in the multicomponent system during solidification. The high thermal stability indicates that the new Co–Fe-based BMG could be used as high-temperature magnetic material. The low coercivity which was as low as 8 A/m for the as-cast sample was found in the Co–Fe-based metallic glass cylinder with a diameter of 1.5 mm. 相似文献
84.
85.
86.
XinMeiZHENG YanXingQI XiaoMingZHANG JiShuanSUO 《中国化学快报》2004,15(6):655-658
Jacobsen‘s catalyst was immobilized onto SBA-15 by multi-step grafting, and this heterogenized catalyst exhibited comparable catalytic performance with the corresponding homogeneous counterpart for the epoxidation of alkenes, and the catalyst could be recycled effectively several times. 相似文献
87.
α—甲基苯乙烯离子聚合体分子量分布 总被引:1,自引:0,他引:1
聚α-甲基苯乙烯-丁二烯-α-甲基苯乙烯嵌段共聚物是一种性能优异的热塑性弹性体。常温下,α-甲基苯乙烯的聚合是在极性添加剂存在下进行的,添加剂的种类,用量及聚合温度不仅影响聚合动力学,尚且影响聚合物分子量及其分布,控制α-甲基苯乙烯聚合速率、 相似文献
88.
89.
The utility of ring-fused 2,3-oxazolidinone derivatives of 2-amino-2-deoxy-thioglycosides in the synthesis of glycopeptide intermediates and building blocks for the synthesis of heparan sulfate oligosaccharides is reported. These unique ring-fused monosaccharides afford a novel and efficient route to alpha-O-linked 2-amino-2-deoxy amino acid derivatives and heparan sulfate oligosaccharide intermediates. 相似文献
90.
HanMingDING LiPingWANG YongKuiSHAN MingYuanHE 《中国化学快报》2003,14(8):852-855
Deposition of inorganic-organic nano-hybrid ultrathin films onto mesoporous silicate materials has been proven possible by using layer-by-layer assembly method. In combination with sol-gel method, titania, subsequently dye molecules (or polymer) were successfully fabricated onto the inner wall of SBA-15. Their structures were preliminarily characterized by FTIR and solid-state UV-Vis spectroscopy, thermal analysis, and BET surface area measurements,respectively. 相似文献