全文获取类型
收费全文 | 1817篇 |
免费 | 94篇 |
国内免费 | 5篇 |
专业分类
1916篇 |
出版年
2024年 | 6篇 |
2023年 | 24篇 |
2022年 | 60篇 |
2021年 | 116篇 |
2020年 | 44篇 |
2019年 | 60篇 |
2018年 | 80篇 |
2017年 | 58篇 |
2016年 | 60篇 |
2015年 | 82篇 |
2014年 | 107篇 |
2013年 | 126篇 |
2012年 | 121篇 |
2011年 | 132篇 |
2010年 | 51篇 |
2009年 | 51篇 |
2008年 | 73篇 |
2007年 | 60篇 |
2006年 | 74篇 |
2005年 | 50篇 |
2004年 | 30篇 |
2003年 | 37篇 |
2002年 | 28篇 |
2001年 | 30篇 |
2000年 | 29篇 |
1999年 | 29篇 |
1998年 | 8篇 |
1997年 | 8篇 |
1994年 | 18篇 |
1993年 | 10篇 |
1992年 | 19篇 |
1991年 | 16篇 |
1990年 | 20篇 |
1989年 | 18篇 |
1988年 | 12篇 |
1987年 | 17篇 |
1986年 | 14篇 |
1985年 | 21篇 |
1984年 | 12篇 |
1983年 | 9篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1979年 | 6篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1974年 | 8篇 |
1973年 | 6篇 |
1972年 | 8篇 |
1971年 | 8篇 |
1970年 | 7篇 |
排序方式: 共有1916条查询结果,搜索用时 0 毫秒
1.
2.
Eliot C. Bush Anne E. Clark Chris M. DeBoever Lillian E. Haynes Sidra Hussain Singer Ma Matthew M. McDermott Adam M. Novak John S. Wentworth 《PloS one》2012,7(11)
A significant proportion of enzymes display cooperativity in binding ligand molecules, and such effects have an important impact on metabolic regulation. This is easiest to understand in the case of positive cooperativity. Sharp responses to changes in metabolite concentrations can allow organisms to better respond to environmental changes and maintain metabolic homeostasis. However, despite the fact that negative cooperativity is almost as common as positive, it has been harder to imagine what advantages it provides. Here we use computational models to explore the utility of negative cooperativity in one particular context: that of an inhibitor binding to an enzyme. We identify several factors which may contribute, and show that acting together they can make negative cooperativity advantageous. 相似文献
3.
4.
M. Zamirul Hussain John C. Belton Rajendra S. Bhatnagar 《In vitro cellular & developmental biology. Plant》1978,14(9):740-745
Organ cultures of newborn rat lungs synthesize and accumulate DNA, RNA, collagen and noncollagenous proteins almost at a linear
rate for at least 5 days. During this period the synthesis of collagen consistently exceeds the synthesis of noncollagenous
proteins in a pattern similar to neonatal lung growth in vivo. Although some morphological characteristics of lung architecture
are distorted after culture, fundamental structural similarities to lungs growing in intact animals are retained. When these
cultures are maintained in atmospheres rich in oxygen, increased collagen synthesis is observed, a response similar to that
of lungs in intact animals exposed to high oxygen concentrations in vivo. Our studies suggest that lung organ cultures may
be a suitable system for investigating the biochemical aspects of lung tissue-environmental interaction.
These studies were supported in parts by NIH Grant HL-19668, a contract (68-03-2005) from the U.S. Environmental Protection
Agency, and grants from the California Lung Association. 相似文献
5.
6.
7.
Replication of cauliflower mosaic virus DNA in leaves and suspension culture protoplasts of cotton 总被引:3,自引:2,他引:1 下载免费PDF全文
Hussain MM Melcher U Whittle T Williams A Brannan CM Mitchell ED 《Plant physiology》1987,84(3):633-639
Cauliflower mosaic virus (CaMV) replicated in protoplasts and in inoculated leaves of the non-host, cotton (Gossypium hirsutum, L.). Protoplasts prepared from suspension-cultured cotton cells were infected by incubation with liposome-encapsulated CaMV virions. During a 1-week culture period the amount of CaMV nucleic acid as detected by nucleic acid hybridization in the protoplasts increased significantly regardless of whether or not the protoplasts contained vacuoles. In leaves inoculated with CaMV virions or CaMV DNA, viral DNA sequences were found by leaf skeleton hybridization to be located in small circular areas. DNA extracted from ultracentrifugal pellets of homogenates of inoculated leaves contained circular, gapped CaMV DNA only when inocula contained CaMV virions, CaMV DNA, or partial nested dimer CaMV plasmid DNA. When plants had been heavily watered, the CaMV DNA recovered contained degraded CaMV DNA. The results suggest that the host range limitation for CaMV is not due to an inability to replicate or spread locally in inoculated leaves. 相似文献
8.
Norma J. Greenfield Mussadeq Hussain John Lenard 《Biochimica et Biophysica Acta (BBA)/General Subjects》1987,926(3)
The vacuoles of logarithmic and stationary stage cells were compared by 31P-NMR with regard to pH, orthophosphate (Pi) content and average size of polyphosphate. The vacuoles of stationary cells had lower pH higher Pi content, and polyphosphates of longer average chain lenght, although total polyphosphate content was about the same as in logarithmic cells. The lower vacuolar pH in stationary cells was the major cause of a larger cytoplasmic-vacuolar pH gradient. Addition of NH4Cl, (NH4)2SO4, methylamine or amantadine at pH 8 to cells in either stage caused an icnrease in both cytoplasmic and vacuolar pH, with little or no change in the cytoplasmic-vacuolar pH gradient. However, the administration of ammonium salts to the cells at pH 8.0 resulted in rapid hydrolysis of the intravacuolar polyphosphate to tripolyphosphate and Pi, with attendant redistribution of Pi between the vacuolar and cytoplasmic compartments. 相似文献
9.
Infection by Macrophonina phaseolina was substantially reduced following treatment of sunflower and mungbean seeds with Trichoderma harzianum, Gliocladium virens, Paecilomyces lilacinus or Streptomyces sp. which gave promising control of charcoal rot disease. Treatment of mungbean seeds with Rhizobium meliloti also gave good disease control. 相似文献
10.
Electric shock-mediated transfection of cells. Characterization and optimization of electrical parameters. 总被引:4,自引:0,他引:4 下载免费PDF全文
D J Winterbourne S Thomas J Hermon-Taylor I Hussain A P Johnstone 《The Biochemical journal》1988,251(2):427-434
The effect of various parameters on the electric shock-mediated permeabilization and transfection of CHO cells has been investigated. Up to 70% of the cells can be maintained transiently permeable to erythrosin B for periods of at least 1 h at 20 degrees C. Electrical conditions optimal for transient permeabilization were also optimal for efficient DNA transfection by pSV2neo. However, the DNA must be present during exposure to the electric field for efficient transformation. The same requirement existed for voltage-induced DNA toxicity. The results suggest that DNA moves into the cells by electrophoresis, not by simple diffusion. Based on these observations a simple, rapid procedure for optimizing the conditions for electric shock-mediated DNA transfer into cells has been developed. 相似文献