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961.
A rapid, simple, selective and sensitive method for the spectrophotometric determination of nitrite in water has been developed and optimum reaction conditions along with other analytical parameters have been evaluated. Nitrite reacts with barbituric acid in acidic solution to give the nitroso derivative, violuric acid. At analytical wavelength of 310 nm, Beer's law is obeyed over the concentration range 0.00–3.22 ppm of nitrite. The molar absorptivity is 15330 ± 259.7 (95%) with pooled standard deviation of 355.57 and R.S.D. of 2.32%. As well as the method is sensitive (2.99 × 10−3 μg NO2 cm−2) and selective, it tolerates most of the potential interferents. It has been successfully applied to nitrite determination in natural waters by use of a calibration graph with determination limit of 1.66 μg NO2 in 100 mL working solution corresponding to minimum 9.5 ppb NO2–N in water samples. Lower concentrations of nitrite (3.0 μg NO2/L sample) is precisely analyzed by using the method of dilution with sample, with R.S.D. of lower than 0.5%. The results were compared with standard N-(1-naphtyl)ethylenediamine dihydrochloride method and very good agreement between the data was observed. The method can easily be applied in the field. 相似文献
962.
963.
964.
重量法测定环戊烷在silicalite-1分子筛上的吸附特性 总被引:4,自引:0,他引:4
用智能重量分析技术 (IGA)研究了环戊烷在silicalite 1分子筛上的吸附特性。结果表明 ,随着温度的降低 ,环戊烷的吸附等温线从第一类型过渡为第四类型 ,在 2 5 4K和 2 74K温度下吸附等温线呈现滞后环 ,为第四类型 ,而吸附等温线在 30 4K、32 3K下为阶梯形 ,在 35 4K、42 3K温度下呈第一类型 ,其中 42 3K温度下的吸附等温线可准确的用Langmuir方程来描述。本文同时讨论了吸附质分子间以及吸附质和吸附剂间的相互作用、分子结构特性、分子筛对吸附质分子的空间位阻、分子筛的能量不均匀表面等对环戊烷在silicalite 1分子筛上吸附性能的影响 相似文献
965.
966.
阻抑催化光度法测定茶叶中的微量氟化物 总被引:5,自引:0,他引:5
在氨基乙酸 HCl缓冲溶液中 ,Fe3+对H2 O2 氧化 2 ,4 二氨基苯酚 (DAP)褪色具有催化作用 ,游离F- 离子与Fe3+形成的稳定络离子 [FeF6]3- 可抑制褪色 ,抑制程度与F- 量线性相关。基于此建立了测定微量F- 的阻抑催化光度分析的新方法。结果表明 ,有色溶液的最大吸收波长为 5 0 0nm ,测定的线性范围为 0~ 9.0mg/L ;摩尔吸光系数为 2 .1× 1 0 5L/mol/cm ;RSD(n =6)为 5 0 %。已应用于茶叶中微量F- 的测定 相似文献
967.
D. P. Scherrer A. W. Kälin R. Kesselring F. K. Kneubühl 《Applied physics. B, Lasers and optics》1991,53(4):250-252
We investigate the generation of superradiant far-infrared 496 m CH3F pulses and produce for the first time smooth and reproducible 373 m CH3CN superradiant pulses by pumping with pulses from a hybrid 10 m CO2 laser truncated within 10 ps by a plasma shutter of new design. Superradiance is confirmed by measurement of the pressure dependence of the intensity, the width and the delay versus the pump pulse. We observe pulse durations considerably under the limit of the inverse linewidth of the transition. Thus, we demonstrate for the first time that rapid truncation of the pump pulse is essential for reducing pulse duration of superradiant far-infrared emissions. 相似文献
968.
969.
Sergent N. Gélin P. Périer-Camby L. Praliaud H. Thomas G. 《Journal of Thermal Analysis and Calorimetry》2003,72(3):1117-1126
The interactions of CO with a high specific surface area tin dioxide was investigated by FTIR spectroscopy and thermogravimetric
analysis. FTIR study of CO interactions have shown that CO can adsorb on cus (coordinatively unsaturated sites) Sn4+ cation sites (band at 2201 cm-1). In addition, CO reacts with surface oxygen atoms. This leads to the partial reduction of SnO2 surface and to the formation of ionised oxygen vacancies together with the release of free electrons, which are responsible
for the loss of transmission. Formed CO2 can chemisorb on specific surface sites: on basic sites to form carbonates species and on acidic sites (Sn4+-CO2 species) which is in competition with the formation of Sn4+-CO species. TG experiment have shown that the reduction of SnO2 by CO at 400°C occurs in two steps. First, the reduction of SnO2 surface, which is a quick phenomenon. This has allowed to evaluate that more than 12% of reducible surface oxygens can react
with CO, essentially because of the presence of a large amount of surface hydroxyl groups. The second step of the reduction
of SnO2 would be the progressive reduction of SnO2 bulk by the slow diffusion of oxygen atoms from the bulk to the surface.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
970.
A simple multi-residue analysis method for the quantitative determination of eprinomectin, abamectin, doramectin and ivermectin
in bovine tissues was developed. The tissue sample was extracted with acetonitrile, followed by clean-up on a C18 solid phase extraction cartridge. The eluate was derivatised before being analyzed by HPLC coupled to a fluorescence detector.
The method was validated using bovine liver and muscle fortified with the drugs at 0, 5, 10 and 50 ng g−1. The mean recoveries of the four drugs were 70.31–87.11% in liver and 79.57–93.65% in muscle, with relative standard deviations
below 17.84% in liver and 14.68% in muscle. The limits of detection were between 0.5 and 1.0 ng g−1 and the limits of quantification were 1–2 ng g−1 in bovine tissues for the four drugs. 相似文献