全文获取类型
收费全文 | 3508篇 |
免费 | 548篇 |
国内免费 | 511篇 |
专业分类
化学 | 2260篇 |
晶体学 | 78篇 |
力学 | 442篇 |
综合类 | 40篇 |
数学 | 278篇 |
物理学 | 1469篇 |
出版年
2024年 | 8篇 |
2023年 | 57篇 |
2022年 | 139篇 |
2021年 | 118篇 |
2020年 | 123篇 |
2019年 | 98篇 |
2018年 | 119篇 |
2017年 | 159篇 |
2016年 | 158篇 |
2015年 | 166篇 |
2014年 | 200篇 |
2013年 | 319篇 |
2012年 | 211篇 |
2011年 | 238篇 |
2010年 | 160篇 |
2009年 | 207篇 |
2008年 | 213篇 |
2007年 | 185篇 |
2006年 | 212篇 |
2005年 | 190篇 |
2004年 | 176篇 |
2003年 | 139篇 |
2002年 | 103篇 |
2001年 | 106篇 |
2000年 | 89篇 |
1999年 | 72篇 |
1998年 | 73篇 |
1997年 | 79篇 |
1996年 | 68篇 |
1995年 | 68篇 |
1994年 | 47篇 |
1993年 | 48篇 |
1992年 | 33篇 |
1991年 | 22篇 |
1990年 | 25篇 |
1989年 | 19篇 |
1988年 | 18篇 |
1987年 | 13篇 |
1986年 | 15篇 |
1985年 | 15篇 |
1984年 | 6篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1973年 | 2篇 |
1959年 | 1篇 |
1948年 | 1篇 |
排序方式: 共有4567条查询结果,搜索用时 0 毫秒
52.
Karen?Glenn Andrew?van?Bommel Subhash?C.?Bhattacharya Rama?M.?PalepuEmail author 《Colloid and polymer science》2005,283(8):845-853
The mixed micelles of sodium dodecyl sulphate (SDS) with Brij35 and Brij 97 were studied separately by fluorescence measurement using pyrene as fluorescent probe. In the range of 0–1.0 mole fraction (X) of added SDS to Brij solutions, the cmc value of the mixed micelles varies from 0.085 to 8 mmol with Brij 35 and 0.04 to 8 mmol with Brij 97. The aggregation number also changes. A measure of the stability of mixed micelles is also presented. The interaction parameter 12 and the chain–chain contribution parameter (B1) are extracted from the analysis of the results. This parameter B1 is related to the standard free energy change associated with the introduction of one ionic species into a nonionic micelle coupled with the release of one nonionic species from the micelle. The clouding behaviour of Brij 97 in the presence of SDS was investigated and the associated thermodynamic parameters of clouding were generated and discussed. 相似文献
53.
巯基葡聚糖凝胶分离富集光度法测定镉的研究 总被引:2,自引:0,他引:2
研究了在TritonX-100存在下,新显色剂邻羧基苯基重氮氨基偶氮苯(CDAA)与镉的显色体系,在pH10.6的Na2B4O7-NaOH体系中,显色反应灵敏度很高。络合物的最大吸收位于545nm处,其摩尔吸光系数为2.22×10^5L·mol^-1·cm^-1。镉含量在0 ̄12μg/25mL符合比耳定律。将该体系用于巯基葡聚糖凝胶分离富集-光度法测水样中微量镉,结果令人满意。 相似文献
54.
V. G. Berezkin A. A. Korolev I. V. Malyukova R. G. Mardanov 《Russian Chemical Bulletin》1997,46(12):2064-2073
The effects of the carrier gas nature and pressure on the relative retention values of organic compounds were studied using
a series of capillary columns differing in the film thickness of the polar stationary phase (PEG-20M). Relative retention
depends linearly on the carrier gas pressure. This dependence becomes more pronounced in the following order of carrier gases:
helium < nitrogen < carbon dioxide. The limiting relative retention at a carrier gas pressure approaching zero rather than
relative retention values measured experimentally (relative retention time, Kovats retention index,etc.) is an invariant characteristic of a compound subjected to chromatography. For the carrier gases studied, the limiting retention
values almost does not depend on the nature of the carrier gas used. The limiting indicating the complex absorption-adsorption
nature of these parameters. Dissolution of a carrier gas in the stationary liquid phase has an effect on the relative retention.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2177–2186, December, 1997. 相似文献
55.
A new method for cadmium separation and concentration with microcrystalline phenolphthalein modified by crystal violet (CV) was developed in the paper. In the presence of potassium iodide (KI) and CV, cadmium are quantitatively absorbed on microcrystalline phenolphthalein in the pH range 1.0-6.0 as the forms of water-insoluble ion-associated complexes (CdI3−)·(CV+) and (CdI42−)·(CV+)2. Effect of different parameters such as phenolphthalein amount, stirring time, the concentration of CV and KI, various salts and metal ions was studied in detail. During the present study, a significant enhancement of the extraction of cadmium was observed. Cd(II) can be completely separated from Zn(II), Fe(II), Co(II), Ni(II), Mn(II), Cr(III) and Al(III) in this microcrystalline system and well concentrated without the interference of these metal ions at high level. The possible reactive mechanism of cadmium concentration has been discussed. Analytical results obtained by this new method were very gratifying. 相似文献
57.
Suyao?Xiao Xuanming?LiuEmail author Chunyi?Tong Jun?Liu Dongying?Tang Lijian?Zhao 《中国科学B辑(英文版)》2005,48(2):162-166
Anion starch nanoparticle (StNP) with a diameter of 50 nm was prepared in water-in-oil microemulsion, with soluble starch
as raw materials and POCl3 as crosslinking agent. PLL-StNP was prepared by linking poly-L-lysine (PLL) on the surface of StNP. At the same time, the
size of PLL-StNP and its stability in aqueous solution were checked by AFM. The analysis of plasmid DNA binding, DNase I enzymatic
degradation, toxicity and transfection were done. We discovered that PLL-StNP may be used as non-virus nanoparticle gene carrier.
And we developed the method of preparing PLL-StNP gene carrier and used it in cell transfection. As non-virus gene carrier,
PLL-StNP has some advantages, such as large load of DNA, high transfection efficiency, low cell toxicity and biodegradability. 相似文献
58.
溶剂聚合膜pH电极作内电极的气敏电极的研究 总被引:1,自引:0,他引:1
研究了以中性载体为活性物的石墨内导平头溶剂聚合膜(SPM)pH电极作内电极的二氧化碳和氨气敏电极。电极的性能取决于中性载体的特性,其中以菸酸十八酯为内电极膜活性物的二氧化碳气敏电极和以二辛基十八胺为活性物的氨气敏电极性能较佳。二氧化碳气敏电极用作丙酮酸脱羧酶酶电极的原电极,其性能院于传统的以玻璃pH电极作内电极的二氧化碳气敏电极。 相似文献
59.
《Electroanalysis》2003,15(17):1397-1402
A new analytical procedure for the simultaneous determination of aluminum(III) and iron(II) in two kinds of dialysis fluids (peritoneal and hemodialysis fluids) by differential pulse adsorptive stripping voltammetry (DPAdSV) is described. The voltammetric measurements were performed using, as working electrode, a stationary mercury electrode, and a platinum electrode and a Ag|AgCl|KCl(sat.) electrode as auxiliary and reference electrodes, respectively, employing acetate buffer solutions at different pH as supporting electrolyte. As complexing agents, Solochrome Violet RS, Palatine Chrome Black 6BN, Chromazurol S and Eriochrome Black T were employed. For both elements, the accuracy, expressed as relative recovery R%, was very satisfactory being in the range 94–105%, the precision as repeatability, expressed as relative standard deviation sr%, was lower than 6%, while the limits of detection were of the order of a few units of μg/L. The analytical voltammetric procedure has been validated by comparison with spectroscopic (graphite furnace atomic absorption spectroscopy, GFAAS) measurements. 相似文献
60.
S.?K.?MehtaEmail author K.?K.?Bhasin Neena?Mehta Shilpee?Dham 《Colloid and polymer science》2005,283(5):532-538
The behavior of rifampicin (D) with -cyclodextrin (-CyD) in aqueous media (W) has been examined by means of UV-vis spectroscopy and conductivity measurements over the temperature range 15–30 °C. The UV-vis study has been used to characterize the systems. The estimated molar absorption coefficient for D/CyD/W system was 10757±280 M–1 cm–1 in comparison to the value of 6133±99 M–1 cm–1 for D/W system. The conductivity was measured (i) as a function of [D] for binary D/W systems, (ii) as a function of [CyD], keeping the concentration of drug constant, for D/CyD/W system, and (iii) as a function of [D] in the presence of a constant cyclodextrin concentration. Two transition points were observed for D/CyD/W system at constant [CyD], which were assigned as cac-1 and cac-2. The stoichiometry of the association was estimated from the conductivity data. This was obtained from [drug] value at which the change in slope of occurs. The standard free energy change,
of aggregation was also calculated from the critical concentration data. An attempt has also been made to estimate the stoichiometry of -cyclodextrin:rifampicin association. 相似文献