全文获取类型
收费全文 | 4303篇 |
免费 | 330篇 |
国内免费 | 4篇 |
出版年
2022年 | 20篇 |
2021年 | 49篇 |
2020年 | 29篇 |
2019年 | 46篇 |
2018年 | 47篇 |
2017年 | 55篇 |
2016年 | 102篇 |
2015年 | 155篇 |
2014年 | 193篇 |
2013年 | 266篇 |
2012年 | 317篇 |
2011年 | 303篇 |
2010年 | 176篇 |
2009年 | 183篇 |
2008年 | 266篇 |
2007年 | 284篇 |
2006年 | 250篇 |
2005年 | 258篇 |
2004年 | 246篇 |
2003年 | 239篇 |
2002年 | 218篇 |
2001年 | 37篇 |
2000年 | 30篇 |
1999年 | 53篇 |
1998年 | 62篇 |
1997年 | 38篇 |
1996年 | 41篇 |
1995年 | 42篇 |
1994年 | 32篇 |
1993年 | 33篇 |
1992年 | 43篇 |
1991年 | 30篇 |
1990年 | 32篇 |
1989年 | 21篇 |
1988年 | 25篇 |
1987年 | 26篇 |
1986年 | 19篇 |
1985年 | 24篇 |
1984年 | 38篇 |
1983年 | 17篇 |
1982年 | 34篇 |
1981年 | 17篇 |
1980年 | 11篇 |
1979年 | 15篇 |
1978年 | 17篇 |
1977年 | 12篇 |
1976年 | 13篇 |
1975年 | 18篇 |
1974年 | 11篇 |
1969年 | 10篇 |
排序方式: 共有4637条查询结果,搜索用时 953 毫秒
81.
Dimitrios Tsikas Joachim Fauler Jürgen C. Frlich 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1992,574(2)
A simple and rapid method is described for the preparation of a stable isotope oxygen-18 labelled leukotriene E4 (LTE4). Oxygen-18 labelling of LTE4 methyl ester in oxygen-18 water catalysed by a pig liver esterase resulted in the incorporation of two oxygen-18 atoms in the carboxylic group of LTE4 to the extent of 89.8% ([18O2]LTE4) and one oxygen-18 atom to the extent of 9.4% ([16O18O]LTE4), with only 0.7% remaining unchanged ([16O2]LTE4). [18O2]LTE4 was found not to back-exchange following incubation in acidified urine (pH 4.0) at 4°C for up to 20 h. [18O2]LTE4 was demonstrated to be a useful internal standard in a method for the quantitative determination of LTE4 in human urine involving high-performance liquid chromatography and gas chromatography with negative-ion chemical ionization tandem mass spectrometry: the concentration of LTE4 in a 24-h urine sample of a healthy subject was determined to be 68.1 pg/ml. 相似文献
82.
83.
Thermal Denaturation of Native Striatal Tyrosine Hydroxylase: Increased Thermolability of the Phosphorylated Form of the Enzyme 总被引:5,自引:5,他引:0
Mitchell A. Lazar Roger J. W. Truscott Joachim D. Raese Jack D. Barchas 《Journal of neurochemistry》1981,36(2):677-682
Tyrosine hydroxylase was purified from bovine corpus striatum. The native enzyme had a half-life of 15 +/- 3 min at 50 degrees C. Phosphorylation of tyrosine hydroxylase with protein kinase purified from both corpus striatum and heart activated the enzyme, but activity was rapidly lost with additional preincubation of the enzyme at 30 degrees C. Thermal denaturation studies indicated that phosphorylated tyrosine hydroxylase had a half-life of 5 +/- 2 min at 50 degrees C 相似文献
84.
85.
The genetic variability of membrane proteins (structure-bound proteins) and cytosol proteins (water-soluble proteins) was investigated in two inbred strains of the mouse, C57BL/6J and DBA/2J. Membrane proteins and cytosol were isolated from the brain and liver of the mouse. The proteins were separated by two-dimensional electrophoresis. A high number of genetic variant proteins (brain, 30; liver, 72) was found in the cytosol. Most of these variants represented changes in the amount of proteins. Electrophoretic mobility changes occurred only in about 1% (brain, 6; liver, 9) of all protein spots of a two-dimensional pattern. In contrast to the cytosol proteins, no genetic variation was detected among the membrane proteins, not even for the quantitative characteristics of the protein spots. The results obtained for the two classes of proteins suggest that the degree of variability in the amount of proteins is related to the degree of variability in the structure of proteins. 相似文献
86.
A facile chemical synthesis of 1,2-dioleoyl and 1,2-dimyristoyl-sn-glycero-3-phospho-L-serine as well as the synthesis of several deuterated derivatives of phosphatidylserine (2 and 3 positions of serine and in the 3-glycerol position) are described. 360 MHz 1H NMR spectra of phosphatidylserine and the optical activity of various phosphatidylserine diastereomers were measured. 相似文献
87.
l-(+)-Bornesitol was detected in 23 of 33 genera of Gentianaceae investigated. The only subtribe without l-(+)-bornesitol (3 species tested) was Exacinae. None of the five genera of Menyanthaceae examined were found to contain l-(+)-bornesitol. 相似文献
88.
A novel reaction of S-adenosyl-L-methionine correlated with the activation of pyruvate formate-lyase
Joachim Knappe Thomas Schmitt 《Biochemical and biophysical research communications》1976,71(4):1110-1117
Conversion of the inactive form of pyruvate formate-lyase to the catalytically active enzyme is accomplished by the Fe-dependent ‘enzyme II’; reduced flavodoxin, S-adenosyl-L-methionine and the effector pyruvate are required. It was found that adenosylmethionine is reductively processed during activation of pyruvate formate-lyase to yield methionine, adenine and 5-deoxyribose. We suggest that transient adenosylation of enzyme II is required for its function as a converter enzyme. 相似文献
89.
Joachim Pohlmann 《Phytochemistry》1975,14(7):1587-1589
The cucurbitacins in roots of Bryonia dioica and B. alba have been investigated. Both species contain the cucurbitacins E, B, I, D, J, K and L, the dihydrocucurbitacins E and B, and tetrahydrocucurbitacin I. The detection of certain cucurbitacin aglycones depends upon the date of harvest, the duration of storage and the methods used for extraction. 相似文献
90.