全文获取类型
收费全文 | 2248篇 |
免费 | 355篇 |
国内免费 | 226篇 |
专业分类
化学 | 1776篇 |
晶体学 | 15篇 |
力学 | 121篇 |
综合类 | 26篇 |
数学 | 159篇 |
物理学 | 732篇 |
出版年
2024年 | 12篇 |
2023年 | 26篇 |
2022年 | 69篇 |
2021年 | 79篇 |
2020年 | 69篇 |
2019年 | 80篇 |
2018年 | 51篇 |
2017年 | 58篇 |
2016年 | 71篇 |
2015年 | 92篇 |
2014年 | 125篇 |
2013年 | 163篇 |
2012年 | 190篇 |
2011年 | 194篇 |
2010年 | 151篇 |
2009年 | 137篇 |
2008年 | 150篇 |
2007年 | 142篇 |
2006年 | 112篇 |
2005年 | 91篇 |
2004年 | 83篇 |
2003年 | 74篇 |
2002年 | 70篇 |
2001年 | 77篇 |
2000年 | 77篇 |
1999年 | 54篇 |
1998年 | 56篇 |
1997年 | 45篇 |
1996年 | 45篇 |
1995年 | 31篇 |
1994年 | 18篇 |
1993年 | 23篇 |
1992年 | 12篇 |
1991年 | 18篇 |
1990年 | 9篇 |
1989年 | 9篇 |
1988年 | 11篇 |
1987年 | 11篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 6篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1966年 | 2篇 |
1931年 | 1篇 |
1924年 | 1篇 |
1884年 | 1篇 |
排序方式: 共有2829条查询结果,搜索用时 15 毫秒
11.
Hong Bi Qianwang Chen Yonglong Zhuang Shenqiang Zhao 《Journal of magnetism and magnetic materials》2006
Molecular magnet {NBu4[Fe Cr(ox)3]}x (NBu4+=tetra(n-buty1) ammonium ion; ox2−=oxalate ion) was synthesized under an applied low magnetic field of 0.3 T in comparison to that synthesized without a field. Their crystallinities, morphologies and magnetic properties were characterized by using the X-ray diffractionmeter, the transmission electron microscope, and a superconducting quantum interference device. It is found that the average size of particles synthesized under the applied field appears larger than that synthesized without a field. Moreover, its crystallinity, morphology and magnetic susceptibility have also been improved. However, its chemical structure and ferromagnetic phase transition temperature Tc do not change. Possible reasons to explain this effect are also discussed. 相似文献
12.
13.
用统计模拟分光光度法测定复方消咳新片4个组分含量。按均匀设计表制备合成样品,绘制溶液的UV-VIS吸收曲线,获得有限但足够的实验数据,用逐步回归法构造反映该复方制剂组分在灵敏波长的吸光度-组分含量经验关系的“最优”数学模型,用改进单纯形法寻优,求出未知样品的各组分含量。磺胺甲基异恶唑、甲氧苄胺嘧啶、盐酸溴已新、枸橼酸维静宁的回收率分别为1003%、1004%、999%、990%,标准差分别为091%、14%、12%、39%。 相似文献
14.
微波场中甲烷部分氧化制合成气 Ⅱ.Co/ZrO_2催化剂在微波场中的升温行为及催化活性 总被引:4,自引:0,他引:4
近年来,甲烷部分氧化制合成气(POM)的研究一直十分活跃[1,2].前文报道了用于甲烷部分氧化制合成气的镍基催化剂(Ni/La2O3)在微波场中的升温行为和催化活性[3],发现在达到相同的CH4转化率时,微波活化方式下的催化剂床层温度比常规加热低得多... 相似文献
15.
Spectroscopic characterization of effective components anthraquinones in Chinese medicinal herbs binding with serum albumins 总被引:2,自引:0,他引:2
Bi S Song D Kan Y Xu D Tian Y Zhou X Zhang H 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,62(1-3):203-212
The interactions of serum albumins such as human serum albumin (HSA) and bovine serum albumin (BSA) with emodin, rhein, aloe-emodin and aloin were assessed employing fluorescence quenching and absorption spectroscopic techniques. The results obtained revealed that there are relatively strong binding affinity for the four anthraquinones with HSA and BSA and the binding constants for the interactions of anthraquinones with HSA or BSA at 20 degrees C were obtained. Anthraquinone-albumin interactions were studied at different temperatures and in the presence of some metal ions. And the competition binding of anthraquinones with serum albumins was also discussed. The Stern-Volmer curves suggested that the quenching occurring in the reactions was the static quenching process. The binding distances and transfer efficiencies for each binding reactions were calculated according to the F?ster theory of non-radiation energy transfer. Using thermodynamic equations, the main action forces of these reactions were also obtained. The reasons of the different binding affinities for different anthraquinone-albumin reactions were probed from the point of view of molecular structures. 相似文献
16.
冠醚型电极对局部麻醉药响应功能的研究 总被引:3,自引:0,他引:3
用二苯并24-冠-8作为活性物质、邻苯二甲酸二(2-乙基)己酯为增塑剂制得PVC膜电极。电极对局麻药丁卡因、普鲁卡因和利多卡因具有能斯特响应,用于局麻药针剂的测定取得满意的结果。 相似文献
17.
乙醇-盐-水-5-Br-PADAP体系萃取分离测定钯 总被引:3,自引:0,他引:3
研究了在硫酸铵存在下 ,5 Br PADAP乙醇体系中Pd(Ⅱ )、Rh(Ⅲ )、Pt(Ⅳ )的萃取行为及乙醇溶液的分相条件 ,讨论了影响萃取率的各种因素 ,试验表明 ,室温下 ,一定 pH范围内 ,该体系中的Pd(Ⅱ )几乎可完全被乙醇相萃取 ,而Rh(Ⅲ )、Pt(Ⅳ )不被萃取或萃取率很低 ,从而可实现Pd(Ⅱ )、Rh(Ⅲ )、Pt(Ⅳ )混合离子的定量分离 ,同时建立了Pd(Ⅱ )的测定方法。乙醇相中Pd(Ⅱ ) 5 Br PADAP配合物表观摩尔吸光系数为 1.18× 10 5L·mol- 1·cm- 1,钯量在 0~ 9.6 0 μg/10ml范围内符合比耳定律 ,检出限为 0 .0 90 μg/10ml。用该法分离混合样和测定两种活性碳钯催化剂中钯 ,结果满意 相似文献
18.
In this study, we report the design and synthesis of a series of new simplified fumitremorgin C analogues. The preliminary biological study indicated some of these simplified fumitremorgin C might be developed into breast cancer resistance inhibitors. 相似文献
19.
Accreditation and Quality Assurance - 相似文献
20.
Bi HC Zhong GP Zhou S Chen X Huang M 《Rapid communications in mass spectrometry : RCM》2005,19(20):2911-2917
A liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed and validated to determine the concentrations of adefovir [9-(2-phosphonylmethoxyethyl)adenine, PMEA] in human plasma. After one-step protein precipitation of plasma samples by methanol, adefovir was analyzed by LC/MS/MS using positive electrospray ionization. Chromatography was performed on a C18 column. The extraction recoveries of adefovir were found to be 85.1-89.3%. Adefovir was stable under routine laboratory conditions. A minimal matrix effect resulting in a slight ionization enhancement of adefovir (<10.9%) was observed, which did not markedly affect the behavior of the calibrations curves and accuracy and precision data. The method had a chromatographic run time of 7.8 min and a linear calibration curve over the concentration range 1.5-90 ng/mL for adefovir. The lower limit of quantification of the method was 1.5 ng/mL. The intra- and inter-day precision was less than 8.4%. These results indicated that this LC/MS/MS method has high selectivity and efficiency, and acceptable accuracy, precision and sensitivity. The validated LC/MS/MS method has been successfully used in a pharmacokinetic study in healthy volunteers treated with oral adefovir dipivoxil at 10 and 20 mg. 相似文献