全文获取类型
收费全文 | 22358篇 |
免费 | 2769篇 |
国内免费 | 2188篇 |
专业分类
化学 | 16865篇 |
晶体学 | 322篇 |
力学 | 1032篇 |
综合类 | 187篇 |
数学 | 2107篇 |
物理学 | 6802篇 |
出版年
2024年 | 36篇 |
2023年 | 299篇 |
2022年 | 604篇 |
2021年 | 662篇 |
2020年 | 692篇 |
2019年 | 703篇 |
2018年 | 560篇 |
2017年 | 567篇 |
2016年 | 969篇 |
2015年 | 914篇 |
2014年 | 1103篇 |
2013年 | 1562篇 |
2012年 | 1878篇 |
2011年 | 1991篇 |
2010年 | 1372篇 |
2009年 | 1209篇 |
2008年 | 1462篇 |
2007年 | 1232篇 |
2006年 | 1234篇 |
2005年 | 1115篇 |
2004年 | 912篇 |
2003年 | 804篇 |
2002年 | 904篇 |
2001年 | 574篇 |
2000年 | 533篇 |
1999年 | 442篇 |
1998年 | 325篇 |
1997年 | 310篇 |
1996年 | 297篇 |
1995年 | 272篇 |
1994年 | 215篇 |
1993年 | 201篇 |
1992年 | 199篇 |
1991年 | 159篇 |
1990年 | 150篇 |
1989年 | 129篇 |
1988年 | 100篇 |
1987年 | 73篇 |
1986年 | 75篇 |
1985年 | 90篇 |
1984年 | 56篇 |
1983年 | 45篇 |
1982年 | 39篇 |
1981年 | 31篇 |
1980年 | 22篇 |
1979年 | 16篇 |
1978年 | 16篇 |
1977年 | 19篇 |
1975年 | 12篇 |
1970年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
The selectivity of intermolecular force is caused by the special interaction between two adaptable groups on the molecules. π bond and conjugated π bonds such as benzene ring are negative charged groups,which may attract stongly positively charged H groups such as 3H in β-C_6H_6Cl_6, and repulse other ne- gatively charged groups such as-C=O(Q). Our experiments show that the reduced retention time tr of benzene on non- polar β-C_6H_6Cl_6 is much greater than that on polar fixed phases such as CH_3— —NO_2 in gas chromatography and that the het of solvation of β-C_6H_6Cl_6 in benzene is also much greater than that of the polar α-C_6H_6Cl_6 and γ-C_6H_6Cl_6. This can′t be explained by the usual Van de Waals′ force. It results from the selective intermoleccular force.... 相似文献
72.
73.
用裂解气相色谱法研究PMR型聚酰亚胺前体在反应中的化学变化过程,以裂解产物醇和环戊二烯的生成率表示酰胺化或酰亚胺化及交联的程度,结果表明,酰胺化或酰亚胺化在50℃以下不发生,在180~220℃完成,降冰片烯端基在150℃以下不发生交联反应,在280℃,10~18小时可完成交联反应。 相似文献
74.
Yun SH Sohn BH Jung JC Zin WC Lee JK Song O 《Langmuir : the ACS journal of surfaces and colloids》2005,21(14):6548-6552
Hexagonal arrangement of iron oxide nanoparticles was fabricated by utilizing a single-layered film of diblock copolymer micelles. The synthesis was directly performed on the solid substrate by oxygen plasma with preserving the dimensional order of micelles so that separate procedures for synthesis and deposition of nanoparticles were not necessary. Since the oxygen plasma treatment also eliminated polymers, pure patterns of iron oxide nanoparticles were obtained. Moreover, easy control over the size of nanoparticles enabled us to selectively create a ferrimagnetic or a superparamagnetic pattern of iron oxide nanoparticles without altering the fabrication process. 相似文献
75.
76.
77.
78.
Fabrication of hexaphenylsilole nanowires and their morphology-tunable photoluminescence. 总被引:1,自引:0,他引:1
Liping Heng Jin Zhai Anjun Qin Yuqi Zhang Yongqiang Dong Ben Zhong Tang Lei Jiang 《Chemphyschem》2007,8(10):1513-1518
Immersion of nanoporous alumina membranes into saturated solutions of hexaphenylsilole with subsequent solvent evaporation affords aligned organic nanowires. The luminescent properties of the hexaphenylsilole nanowires can be manipulated by varying their morphologies, which were controlled by changing the channel sizes of the alumina templates. 相似文献
79.
Immobilized polysiloxane-anchored permethyl-β-cyclodextrin (Chirasil-Dex) with a cyclodextrin content of approximately 30 % by weight, previously employed as a versatile chiral stationary phase for the separation of enantiomers by GC, has been used for the separation of enantiomers by capillary supercritical fluid chromatography (SFC). A considerable number of racemates could be resolved, e.g. aromatic alcohols, amino alcohols (TFA derivatives), and underivatized acids. Many pharmaceutical compounds were among those analyzed, including several NSAIDs (e.g. ibuprofen and ketoprofen), a steroidal drug (nor-gestrel), a barbiturate (hexobarbital), and others. Among the racemates resolved were many which cannot be analyzed by GC owing to low volatility or decomposition at elevated temperatures. For two racemates, analysis temperature and mobile phase density were systematically varied to give constant analysis times or capacity factors k. Low temperatures (ca 60 °C) yielded the best separation in term of separation factor, α, or resolution, Rs, even though higher densities had to be used. In comparison with GC, capillary SFC was able to furnish higher separation factors and similar resolution. The applicability of capillary SFC for the analysis of mixtures of cyclodextrin derivatives, e.g. those used in the synthesis of Chirasil-Dex, was, furthermore, demonstrated. 相似文献
80.
采用火焰原子吸收法对30例男性型秃发患者及38例毛发健康男性对照者发中宏量元素K、Na、Ca、Mg的含量进行了测定。结果表明,男性型秃发患者发K含量明显高于对照组,具有统计学上的显著差异(P〈0.01)。发Na、Ca、Mg含量在两组间未见显著差异(P〉0.05)。本文提示,体内某些宏量元素变化对男性型秃发可能产生一定影响。 相似文献