全文获取类型
收费全文 | 234095篇 |
免费 | 18672篇 |
国内免费 | 85篇 |
出版年
2021年 | 2219篇 |
2018年 | 2989篇 |
2017年 | 2758篇 |
2016年 | 3855篇 |
2015年 | 4411篇 |
2014年 | 5173篇 |
2013年 | 6990篇 |
2012年 | 8129篇 |
2011年 | 8389篇 |
2010年 | 5600篇 |
2009年 | 5154篇 |
2008年 | 7067篇 |
2007年 | 7305篇 |
2006年 | 6834篇 |
2005年 | 6844篇 |
2004年 | 6968篇 |
2003年 | 6493篇 |
2002年 | 6098篇 |
2001年 | 9690篇 |
2000年 | 9831篇 |
1999年 | 7441篇 |
1998年 | 2526篇 |
1997年 | 2543篇 |
1996年 | 2351篇 |
1995年 | 2097篇 |
1993年 | 2090篇 |
1992年 | 6047篇 |
1991年 | 6125篇 |
1990年 | 5838篇 |
1989年 | 5823篇 |
1988年 | 5440篇 |
1987年 | 5135篇 |
1986年 | 4687篇 |
1985年 | 4837篇 |
1984年 | 3956篇 |
1983年 | 3327篇 |
1982年 | 2253篇 |
1981年 | 2046篇 |
1979年 | 3623篇 |
1978年 | 2905篇 |
1977年 | 2568篇 |
1976年 | 2319篇 |
1975年 | 2830篇 |
1974年 | 3176篇 |
1973年 | 3101篇 |
1972年 | 2862篇 |
1971年 | 2602篇 |
1970年 | 2261篇 |
1969年 | 2198篇 |
1968年 | 2054篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
971.
N. M. Ezhova I. S. Garkushina O. A. Pisarev 《Applied Biochemistry and Microbiology》2011,47(6):635-639
New hydrophilic polymer sorbents comprising reactionary sites which are complementary to a molecule of antibiotic erythromycin
were synthesized by the method of molecular imprinting. A series of similar sorbents without reactionary sites was used for
comparison of sorption characteristics. Sorption of erythromycin on both types of polymer sorbents synthesized was studied
in a wide range of pH and ionic strength. Selectivity of erythromycin sorption on molecularly imprinted cross-linked polymers
was shown to depend on the specific interaction of target molecule with polymer matrix. This type of sorbent is perspective
for the development of antibiotic purification directly from a culture medium Saccharopolyspora erythreus. 相似文献
972.
R. K. Chailakhyan Yu. V. Gerasimov A. I. Kuralesova N. V. Latsinik E. N. Genkina M. R. Chailakhyan 《Biology Bulletin》2001,28(6):575-584
We present the results of a study on the proliferative and differentiation potential of individual clones of stromal fibroblasts growing in monolayer cultures of bone marrow cells. Each precursor cell yielding a large colony in primary culture is capable of up to 34 doublings in vitro. The transplantation of clones or monoclonal strains of stromal fibroblasts into the open system results in the formation of microenvironment consisting of the bone and reticular tissue and is suitable for the differentiation of all three lines of hemopoiesis. Evidence has been obtained that, in a closed system, individual clones are capable of differentiation into the bone, cartilaginous, and reticular tissues. In other words, the adult organism has a common cell precursor for these tissues. 相似文献
973.
974.
Experiments on cyanobacterial cultures showed that initial exposure to copper at concentrations of 0.01–0.05 mg/l not only has a direct toxic effect, but also significantly modifies the copper tolerance of cyanobacteria for repeated exposure. The response to repeated exposure and the mechanism of tolerance depend on the strength of the initial effect of copper and the extent of heterogeneity of the initial cyanobacterial population. 相似文献
975.
976.
V. N. Barai A. I. Zinchenko L. M. Zalashko L. A. Eroshevskaya I. A. Mikhailopulo 《Biotechnology letters》1995,17(6):599-602
Summary The title compound was prepared by a three-stage enzymatic procedure consisting of (i) RNA hydrolysis to a mixture of ribonucleosides using intact mycelium of Spicaria violacea, (ii) transribosylation of exogenous adenine employing whole cells of Escherichia coli as a biocatalyst, and (iii) conversion of formed adenosine into ATP by the enzymes of alcohol fermentation and the kinases extracted from baker's yeast. 相似文献
977.
Biophysics - The relationship between pandemic morbidity and the shared participation of a pandemic variant in epidemic process has been studied based on the example of the first pandemic wave of... 相似文献
978.
Nisin stimulates oxygen consumption by Staphylococcus aureus and Escherichia coli. 总被引:2,自引:2,他引:0
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)
Nisin stimulated oxygen consumption by nongrowing, glucose-metabolizing Staphylococcus aureus and Escherichia coli cells, indicating a protonophore mode of action. A similar stimulation in E. coli cells osmotically stressed to disrupt the outer cell membrane confirmed the cytoplasmic membrane as the site of nisin action and showed that nisin uptake was not prevented by the outer membrane. 相似文献
979.
Immunochemical analysis of the cAMP-dependent protein kinase regulatory subunit type II was performed with the use of two rabbit antisera elicited to a free R-subunit from pig brain and to a RcAMP complex. Quantitative precipitation of the homogeneous antigen revealed six determinants on the R-molecule. Of these at least one is localized in the R-fragment (37 kD), the others--in the N-terminal part of the R-molecule. The antigenic determinants seem to be remoted from the cAMP-binding centers, since the attachment of the affinity purified antibody Fab-fragments to the R-subunit did not influence the cAMP-binding activity of the latter. The antibodies to RcAMP caused dissociation of the holoenzyme. The antibody Fab-fragment binding to the R-subunit prevented its association with the catalytic subunit. The results of immunochemical analysis suggest that the R-subunit adopts different conformations when bound to cAMP or to the catalytic subunit. 相似文献
980.
R D Keynes N G Greeff I C Forster J M Bekkers 《Proceedings. Biological sciences / The Royal Society》1991,246(1316):135-140
The effect of tetrodotoxin (TTX) on the sodium gating current in the squid giant axon was examined by recording the current that flowed at the pulse potential at which the ionic current fell to zero, first in the absence and then in the presence of TTX. The addition of 1 microM TTX to the bathing solution had no consistent effect on the size of the initial peak of the gating current, but resulted in small changes in the timecourse of its subsequent relaxation which were mainly caused by a reduction of about one quarter in the component that has a delayed onset and may possibly arise from changes in the state of ionization of groups in the channel wall when the lumen fills with water. Our findings suggest that the binding of TTX at the outer face of the sodium channel does not interfere with the mechanisms of activation and inactivation by the voltage sensors, but has an allosteric effect on the access of internal cations to the inside of the channel. 相似文献