全文获取类型
收费全文 | 124155篇 |
免费 | 9260篇 |
国内免费 | 7439篇 |
专业分类
化学 | 58172篇 |
晶体学 | 1453篇 |
力学 | 9671篇 |
综合类 | 480篇 |
数学 | 37083篇 |
物理学 | 33995篇 |
出版年
2024年 | 146篇 |
2023年 | 905篇 |
2022年 | 1721篇 |
2021年 | 1851篇 |
2020年 | 1952篇 |
2019年 | 1958篇 |
2018年 | 11795篇 |
2017年 | 11639篇 |
2016年 | 8164篇 |
2015年 | 3356篇 |
2014年 | 3348篇 |
2013年 | 4173篇 |
2012年 | 8164篇 |
2011年 | 14818篇 |
2010年 | 8842篇 |
2009年 | 9227篇 |
2008年 | 10061篇 |
2007年 | 11688篇 |
2006年 | 3068篇 |
2005年 | 3585篇 |
2004年 | 3230篇 |
2003年 | 3382篇 |
2002年 | 2434篇 |
2001年 | 1434篇 |
2000年 | 1250篇 |
1999年 | 1036篇 |
1998年 | 889篇 |
1997年 | 725篇 |
1996年 | 755篇 |
1995年 | 610篇 |
1994年 | 545篇 |
1993年 | 471篇 |
1992年 | 355篇 |
1991年 | 347篇 |
1990年 | 328篇 |
1989年 | 252篇 |
1988年 | 227篇 |
1987年 | 195篇 |
1986年 | 185篇 |
1985年 | 154篇 |
1984年 | 94篇 |
1983年 | 97篇 |
1982年 | 80篇 |
1981年 | 72篇 |
1980年 | 67篇 |
1979年 | 71篇 |
1978年 | 49篇 |
1914年 | 46篇 |
1912年 | 41篇 |
1909年 | 42篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Synchrotron radiation X-ray fluorescence (SRXRF) spectroscopy is an advanced method of quantitative multielemental analysis with space resolution of several microm and sensitivities in the microg g(-1) range. It can be used for keeping track of trace elements after an electrophoretic separation of biological samples. In this paper, proteins in human liver cytosol were separated with gel filtration chromatography and thin layer isoelectric focusing (IEF). The contents of metal ions in protein bands were determined by SRXRF. The results showed that in the molecular weight (MW) range of 10 approximately 25 kDa, there were at least 2 Zn-containing bands with isoelectric point (pI) of 5 approximately 6 and 6.2 approximately 7, respectively and about 11 Fe-containing proteins with pI of 4.4, 4.6, 4.8, 5.0, 5.2, 5.3, 5.5, 5.6, 6.6, 6.8, and 7.2, respectively, present in human liver cytosol. The Zn-containing band with pI of 5-6 is the dominant species of zinc in this MW range. In addition, the Cu-containing bands with pI of 5.0 and below 4.8 were also detected. It is demonstrated that the procedure could be widely used in further investigations of the chemical species of trace elements in biological samples. 相似文献
992.
993.
Spectrophotometric determination of procaine hydrochloride is described. The procaine hydrochloride reacts with p-dimethylaminobenzalhyde in glacial acetic acid to form an Schiff base which is a yellow compound, and its maximum absorption wavelength is at 455nm, 455=3.46×104. The absorbance for procaine hydrochloride from 0.2 to 15 μg ml−1 obeys Beer's law. The linear regression equation of the calibration graph is C=5.866A−0.02, with a linear regression correlative coefficient is 0.9994 and relative standard deviation (RSD) of 1.7%; the detection limit is 0.1 μg ml−1; recovery is from 92.0 to 110.0%. Effects of reaction medium, temperature, gentamycin, beneylpenicillin, kanamycin, streptomycin, foreign ions, and stand for time on the determination of procaine hydrochloride have been examined. The results obtained by this method agreed with those by the official method (dead-stop titration). This method is rapid and simple, and can be used for the determination of procaine hydrochloride in injection solution of procaine hydrochloride. 相似文献
994.
995.
运用HREELS技术对甲醇在预吸附氯的Ag(111)表面上的吸附氧化行为进行了较细致的研究.结果证明Cl对甲醇氧化的影响缘于它在Ag(111)上的吸附所引起的表面结构的改变进而改变表面氧吸附物种,从而使得甲醇氧化的中间产物发生变化.实验结果说明甲醇在Ag(111)和低暴露量氯吸附的Ag(111)表面上的氧化行为是相似的,检测到了中间产物Ⅰ和Ⅲ;在高暴露量氯吸附的Ag(111)上甲醇氧化时则产生中间产物Ⅰ、Ⅳ和甲醛物种.对上述不同的甲醇氧化行为作了分析,并指出了以前人们在考察甲醇氧化机理时只考虑原子氧作用的片面性. 相似文献
996.
Wei ZL Sakamuri S Petukhov PA George C Lewin NE Blumberg PM Kozikowski AP 《Organic letters》2002,4(13):2169-2172
[structures: see text] Both (2S,5R,6R)- and (2S,5R,6S)-6-hydroxy-8-(1-decynyl)benzolactam-V8 were designed and synthesized as PKC modulators. Biological assays reveal the (6R)-ligand to be 20-fold more potent than its (6S)-counterpart in binding to PKC alpha. 相似文献
997.
998.
999.
Upon the electrochemical oxidation of tris(2,2′-bipyridyl) ruthenium(II) [Ru(bpy)2+3] and hydroxyl carboxylic acids, for instance, citric acid, tartaric acid, malic acid, and
-gluconic acid, bright electrochemiluminescences (ECLs) were observed. Different luminescent reactions were presented depending on the applied potential. The light emission was mainly caused by the reaction between alkoxide radical ion and Ru(bpy)3+3below the potential +1.80 V (vs Ag/AgCl). The luminescence intensity obviously increased because of the more complex reaction process. The luminescence wavelength of 608 nm, which could be found either at higher potential than +1.80 V or in the potential range from +1.30 to +1.80 V, confirmed that ECL was caused by Ru(bpy)2+3*. The factors which affect the determination and HPLC separation of the four acids were also investigated. 相似文献
1000.