全文获取类型
收费全文 | 17781篇 |
免费 | 1789篇 |
国内免费 | 5篇 |
出版年
2022年 | 167篇 |
2021年 | 264篇 |
2020年 | 185篇 |
2019年 | 259篇 |
2018年 | 366篇 |
2017年 | 311篇 |
2016年 | 528篇 |
2015年 | 819篇 |
2014年 | 901篇 |
2013年 | 1053篇 |
2012年 | 1307篇 |
2011年 | 1238篇 |
2010年 | 860篇 |
2009年 | 698篇 |
2008年 | 987篇 |
2007年 | 923篇 |
2006年 | 849篇 |
2005年 | 771篇 |
2004年 | 811篇 |
2003年 | 660篇 |
2002年 | 602篇 |
2001年 | 340篇 |
2000年 | 305篇 |
1999年 | 270篇 |
1998年 | 165篇 |
1997年 | 153篇 |
1996年 | 115篇 |
1995年 | 111篇 |
1994年 | 127篇 |
1993年 | 117篇 |
1992年 | 187篇 |
1991年 | 194篇 |
1990年 | 176篇 |
1989年 | 189篇 |
1988年 | 167篇 |
1987年 | 157篇 |
1986年 | 154篇 |
1985年 | 142篇 |
1984年 | 118篇 |
1983年 | 96篇 |
1982年 | 96篇 |
1981年 | 102篇 |
1980年 | 90篇 |
1979年 | 106篇 |
1978年 | 106篇 |
1976年 | 85篇 |
1975年 | 97篇 |
1974年 | 94篇 |
1973年 | 88篇 |
1972年 | 69篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
The effect of carbohydrate depletion on procoagulant activity and in vivo survival of highly purified human factor VIII 总被引:1,自引:0,他引:1
P J Fay S I Chavin J E Malone D Schroeder F E Young V J Marder 《Biochimica et biophysica acta》1984,800(2):152-158
Human factor VIII procoagulant protein (factor VIII) was purified using a modification of our previously described method, in which Sephacryl S-400 elution, rather than QAE-cellulose chromatography, served as the final purification step. The protein had a specific activity of more than 2500 U/mg and consisted of a single polypeptide (Mr 100 000) when analyzed by SDS-polyacrylamide gel electrophoresis. Factor VIII was shown to be a glycoprotein by staining with periodic acid-Schiff's reagent following electrophoresis. Treatment of factor VIII with a mixture of exo- and endoglycosidases caused a reduction by about 50% in the intensity of periodic acid-Schiff staining, as determined by scanning densitometry, and an increase in electrophoretic mobility (equivalent to a new Mr 95 000). Removal of this portion of the total carbohydrate had no significant effect on factor VIII clotting activity or on thrombin potentiation of clotting activity. The in vivo survival curves of a native and sugar-depleted 125I-labeled factor VIII both showed similar patterns of initial rapid decay to 60 and 40% activity, respectively, followed by a one-half decay time of 4 h for both. These results suggest that the carbohydrate portion of human factor VIII does not contribute significantly to either clotting function in vitro or to biological turnover in vivo. 相似文献
2.
Cristian A. Acevedo Elizabeth Y. Sanchez Juan G. Reyes Manuel E. Young 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2010,878(3-4):449-455
It is known that skin releases volatile organic compounds to the environment, and also that its emission pattern changes with aging of the skin. It could be considered, that these compounds are intermediaries in cell metabolism, since many intermediaries of metabolic pathways have a volatile potential. In this work, a simple and non-destructive method consisting of SPME sampling and GC/MS analysis was developed to identify volatile organic emanations from cell cultures. This technique, applied to skin cells culture, indicates that the cells or cell metabolism produce several skin emissions. Chemometric analysis was performed in order to explore the relationship between a volatile profile and the senescence of cell cultures. Volatile profiles were different for cell cultures in different degrees of senescence, indicating that volatile compound patterns could be used to provide information about the age of skin cells. 相似文献
3.
4.
5.
6.
Surface sediment diatoms from the east coast of Lake Tanganyika were analysed using ordination and classification techniques, and compared with assemblages previously described from the northern part of the lake. Grain-size analyses were performed on subsamples. Four groups of diatom assemblages were recognised. The first group clusters samples taken in the north, far from the Rusizi river mouth. The second group comprises samples taken on silty sediment along the Tanzanian coast, including one sample taken near the mouth of the Malagarazi river and those from the northernmost part of the lake. The third group comprises surface sediments along the Burundian coast (near Ramba and Magara), and the fourth is characterised by epipsammic taxa. A sample taken near the central arm of the Malagarazi river is included in the latter group. The impact of small rivers on the diatom assemblages in the surface sediments is restricted to the mouth area. 相似文献
7.
Novel Method for Detection of Butanolides in Streptomyces coelicolor Culture Broth, Using a His-Tagged Receptor (ScbR) and Mass Spectrometry 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yung-Hun Yang Hwang-Soo Joo Kwangwon Lee Kwang-Kyung Liou Hei-Chan Lee Jae-Kyung Sohng Byung-Gee Kim 《Applied microbiology》2005,71(9):5050-5055
γ-Butyrolactone derivative molecules in Streptomyces play a crucial role in cell density control, secondary metabolism, and cell differentiation. As their synthesis level in the cell is very low compared to those of similar N-acyl homoserine lactone molecules from gram-negative bacteria, it is very hard to analyze them even with several hundredfold concentration of the culture broth. We have developed a very quick and easy detection method using an affinity capture technique with His-tagged receptor proteins and electrospray tandem mass spectrometry. Using Streptomyces coelicolor as a model system, SCB1 was detected from only 100 ml of the culture broth after solvent extraction. This method can be further applied to detection and quantitative analysis of butanolides and inhibitor screening of the receptor molecules. 相似文献
8.
The products of mitochondrial protein synthesis have been investigated in Tetrahymena after labelling with [35S]methionine in the presence of cycloheximide. The labelled proteins were analyzed by sodium dodecyl sulfate slab polyacrylamide gel electrophoresis. We have identified 13 electrophoretically discrete bands as well as 4 other bands with a more variable occurrence. These proteins ranged in apparent molecular weight from 8100 to 57,500. The cycloheximide-resistant incorporation could be blocked with chloramphenicol. The mitochondrial proteins appeared to be in a disaggregated state and were stable to agents such as trichloroacetic acid (hot or cold) and chloroform-methanol. The pattern of proteins was similar following labelling times ranging from 30 min to 3 h. 相似文献
9.
10.
A serum- and glucocorticoid-regulated 4-kilobase mRNA encodes a cyclooxygenase-related protein. 总被引:21,自引:0,他引:21
M K O'Banion H B Sadowski V Winn D A Young 《The Journal of biological chemistry》1991,266(34):23261-23267