全文获取类型
收费全文 | 30512篇 |
免费 | 5100篇 |
国内免费 | 5318篇 |
专业分类
化学 | 23104篇 |
晶体学 | 591篇 |
力学 | 1599篇 |
综合类 | 463篇 |
数学 | 3614篇 |
物理学 | 11559篇 |
出版年
2024年 | 106篇 |
2023年 | 522篇 |
2022年 | 1051篇 |
2021年 | 1128篇 |
2020年 | 1198篇 |
2019年 | 1254篇 |
2018年 | 1039篇 |
2017年 | 1158篇 |
2016年 | 1404篇 |
2015年 | 1515篇 |
2014年 | 1861篇 |
2013年 | 2337篇 |
2012年 | 2753篇 |
2011年 | 2819篇 |
2010年 | 2272篇 |
2009年 | 2187篇 |
2008年 | 2356篇 |
2007年 | 2192篇 |
2006年 | 2037篇 |
2005年 | 1637篇 |
2004年 | 1175篇 |
2003年 | 918篇 |
2002年 | 917篇 |
2001年 | 845篇 |
2000年 | 730篇 |
1999年 | 582篇 |
1998年 | 410篇 |
1997年 | 354篇 |
1996年 | 317篇 |
1995年 | 298篇 |
1994年 | 283篇 |
1993年 | 213篇 |
1992年 | 191篇 |
1991年 | 160篇 |
1990年 | 154篇 |
1989年 | 116篇 |
1988年 | 98篇 |
1987年 | 66篇 |
1986年 | 70篇 |
1985年 | 64篇 |
1984年 | 26篇 |
1983年 | 24篇 |
1982年 | 25篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 13篇 |
1978年 | 8篇 |
1971年 | 5篇 |
1957年 | 4篇 |
1936年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Odd/even effect in the chain length on the enthalpy of micellization of gemini surfactants in aqueous solution 总被引:1,自引:0,他引:1
Li Y Li P Wang J Wang Y Yan H Thomas RK 《Langmuir : the ACS journal of surfaces and colloids》2005,21(15):6703-6706
The micellization properties of cationic symmetric gemini surfactants, [CmH(2m+1)(CH3)2N(CH2)6N(CH3)2CmH(2m+1)]Br2 (designated as CmC6CmBr2, with m = 7, 8, 9, 10, 11, 12, and 16), has been investigated by isothermal titration microcalorimetry. The critical micelle concentration (CMC) and enthalpy of micellization (DeltaHmic) were determined from calorimetric titration curves. The linear decreasing of log CMC with increasing the length of the hydrophobic chain is consistent with an increase in the hydrophobicity of the alkyl chain. Interestingly, with increasing the length of the alkyl chain, the DeltaHmic values of the surfactants with even numbered alkyl chains vary from endothermic to exothermic, whereas the DeltaHmic values of the surfactants with odd numbered alkyl chains are all endothermic and tend to become more endothermic. The pronounced even/odd effect in DeltaHmic is discussed with respect to the "donor-acceptor" interaction. 相似文献
22.
Using simple physical arguments, a local spin-polarized exchange potential, Vxσ, is constructed from the single-particle Hartree–Fock (HF ) potentials (generalized Slater method) that reduces to the usual Kohn–Sham (KS ) result in the uniform gas limit. Numerical results for 10 closed subshell atoms demonstrate that the total energy calculated employing this Vxσ is closer to the exact KS results than those of other standard exchange approximations with electron densities and highest occupied orbital eigenvalues that closely approximate the HF results. 相似文献
23.
X. Y. Li G. J. Wang J. G. Sun Y. T. Zheng B. Yan H. T. Xie X. Wang 《Chromatographia》2007,65(1-2):13-18
To support preclinical pharmacokinetic investigation of 1-[4-[2-(4-bromobenzene-sulfonaminoethyl)phenylsufonyl]-3-(trans-4-methylcyclohexyl)urea
(G004), a rapid, sensitive and specific high-performance liquid chromatography–electrospray ionization mass spectrometry (LC–ESI-MS)
method was developed and validated. Glibenclamide was employed as internal standard. After liquid–liquid extraction the analyte
was analyzed on a Kromasil C18 column (150 × 2.0 mm i.d.) with a mobile phase consisted of acetonitrile–water (0.05% acetic acid), 30:70 (v/v). The flow
rate was 0.2 mL min−1. Detection was performed on a quadrupole mass spectrometer using an electrospray ionization interface and the selected-ion
monitoring (SIM) mode. The retention time was about 3.5 and 4.2 min for Glibenclamide and G004, respectively. The assay was
linear over the concentration range of 2.0–500.0 ng mL−1. Extraction Recovery of G004 in rat plasma was more than 87%. The intra- and inter-assay precision was lower than 11.5% (CV).
This validated method was successfully applied to the pharmacokinetics of G004 in rats. 相似文献
24.
25.
26.
27.
We investigate classical electronic collisions with a He(+) ion. Scattering functions, such as the scattering angle, collisional time, or energy of the outgoing electron, all exhibit an interesting hierarchial self-similar structure, which can be interpreted in terms of the indefinite number of electronic returns to the vicinity of the nucleus, encounters between electrons, and Keplerian excursions of electrons during the collisional processes. Based on this mechanism a binary coding is introduced to organize the dynamics of this three-body system and to provide an understanding of the self-similarity among generations of scale magnification, which yields escape rates that vary with the sectional cut into the parameter space. The self-similarity displayed within a single generation, on the other hand, can be simply tied to the periods of the two independent electronic excursions. The physical interpretation and the symbolic dynamics introduced here are generally useful for three-body collisional systems, including atomic, molecular, or stellar collisions. 相似文献
28.
Seifert N Liu D Barnes A Albridge R Yan Q Tolk N Husinsky W Betz G 《Physical review. B, Condensed matter》1993,47(13):7653-7658
29.
一种新型的表面声波阻抗传感器及其在液相体系中的应用姚守拙,陈康,刘德忠,聂利华(湖南大学化学化工系,长沙,410082)关键词表面声波,阻抗传感器,液相应用表面声波传感器(SAWS)具有较高的灵敏度和检测精度,已广泛应用于气体微量组分分析、色谱检测和... 相似文献
30.
PiezoelectricFiber-opticSpectroelectrochemistry──ANewTechniqueofSpectroelectrochemistryinCombinationWithPiezoelectricQuartzCr... 相似文献