全文获取类型
收费全文 | 50438篇 |
免费 | 3616篇 |
国内免费 | 24篇 |
出版年
2024年 | 56篇 |
2023年 | 186篇 |
2022年 | 595篇 |
2021年 | 982篇 |
2020年 | 606篇 |
2019年 | 731篇 |
2018年 | 1110篇 |
2017年 | 988篇 |
2016年 | 1618篇 |
2015年 | 2492篇 |
2014年 | 2849篇 |
2013年 | 3198篇 |
2012年 | 4211篇 |
2011年 | 4061篇 |
2010年 | 2549篇 |
2009年 | 2338篇 |
2008年 | 3198篇 |
2007年 | 3101篇 |
2006年 | 2687篇 |
2005年 | 2488篇 |
2004年 | 2273篇 |
2003年 | 1973篇 |
2002年 | 1723篇 |
2001年 | 1354篇 |
2000年 | 1275篇 |
1999年 | 1027篇 |
1998年 | 422篇 |
1997年 | 368篇 |
1996年 | 261篇 |
1995年 | 229篇 |
1994年 | 218篇 |
1993年 | 182篇 |
1992年 | 340篇 |
1991年 | 312篇 |
1990年 | 277篇 |
1989年 | 243篇 |
1988年 | 189篇 |
1987年 | 168篇 |
1986年 | 139篇 |
1985年 | 115篇 |
1984年 | 88篇 |
1983年 | 86篇 |
1982年 | 64篇 |
1981年 | 54篇 |
1980年 | 55篇 |
1979年 | 74篇 |
1978年 | 53篇 |
1977年 | 51篇 |
1975年 | 44篇 |
1974年 | 65篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
The desulfurization activity of the resting cells of Gordona sp. CYKS1 was strongly depended on harvest time and the highest value when the cells had been harvested in the early growth phase (0.12 mg sulfur g–1 cell–1 h–1). For the model oil, hexadecane containing dibenzothiophene, the specific desulfurization rate decreased as the reaction proceeded. Both the specific and the volumetric desulfurization rates were not significantly affected by the aqueous-to-oil phase ratio. The diesel oils, light gas oil and a middle distillate unit feed were desulfurized at higher rates (ca. 0.34 mg sulfur g–1 cell–1 h–1) than the model oil (0.12 mg sulfur g–1 cell–1 h–1). 相似文献
2.
3.
K. H. Jang J. W. Seo K. B. Song C. H. Kim S. K. Rhee 《Bioprocess and biosystems engineering》1999,21(5):453-458
Secretion of levansucrase from Zymomonas mobilis in Escherichiacoli by glycine supplement was investigated. A significant amount of levansucrase (about 25% of total activity) was found in intact whole-cells. Cell fractionation experiments showed that levansucrase was found both in the periplasmic space and in the cytoplasmic fraction of E. coli. None or only trace amounts of levansucrase was detected in the extracellular culture broth at 24 h of cultivation and it accrued with the increasing concentration of glycine in the culture medium and duration of the culture period. Optimal glycine concentration for the maximum secretion of levansucrase was in the range of 0.8-1%, in which approximately 20-50% of levansucrase was released into the extracellular fraction at 24 h of cultivation, although glycine retarded the bacterial growth. 相似文献
4.
5.
6.
Hyun I. Park 《Analytical biochemistry》2010,396(2):262-60
Matrix metalloproteinases (MMPs) are a family of hydrolytic enzymes that play significant roles in development, morphogenesis, inflammation, and cancer invasion. Endometase (matrilysin 2 or MMP-26) is a putative early biomarker for human carcinomas. The effects of the ionic and nonionic detergents on catalytic activity of endometase were investigated. The hydrolytic activity of endometase was detergent concentration dependent, exhibiting a bell-shaped curve with its maximum activity near the critical micelle concentration (CMC) of nonionic detergents tested. The effect of Brij-35 on human gelatinase B (MMP-9), matrilysin (MMP-7), and membrane-type 1 MMP (MT1-MMP) was further explored. Their maximum catalysis was observed near the CMC of Brij-35 (∼ 90 μM). Their IC50 values were above the CMC. The inhibition mechanism of MMP-7, MMP-9, and MT1-MMP by Brij-35 was a mixed type as determined by Dixon’s plot; however, the inhibition mechanism of endometase was noncompetitive with a Ki value of 240 μM. The catalytic activities of MMPs are influenced by detergents. Monomer of detergents may activate and stabilize MMPs to enhance catalysis, but micelle of detergents may sequester enzyme and block the substrate binding site to impede catalysis. Under physiological conditions, a lipid or membrane microenvironment may regulate enzymatic activity. 相似文献
7.
8.
I C Kim 《The Journal of biological chemistry》1982,257(2):1063-1070
Rabbit antiserum produced against rat liver cytochrome H-450 was specific for cytochrome H-450. The antiserum did not react with hemolysate, microsomal and mitochondrial fractions of liver, and tissue extracts from heart, lung skeletal muscle, and testis of rat. With the monospecific antiserum, a rocket immunoelectrophoretic assay method was developed for the quantitation of the antigen with a sensitivity of 25 ng. By using rocket immunoelectrophoresis, the total amounts of the antigen found in liver, kidney, and brain of 20 rats were 33.6, 3.6, and 1.3 mg, respectively. It appears that the antigens in liver, kidney, and brain are immunologically identical. From immunological studies with subcellular fractions of rat liver, the antigen was found only in the postmicrosomal fraction. This indicates that the antigen is not a precursor or a proteolytic product of known cytochromes in mitochondria or microsomes. Therefore, cytochrome H-450 is a unique cytosolic protein found in brain, kidney, and liver. 相似文献
9.
10.
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