全文获取类型
收费全文 | 2407篇 |
免费 | 287篇 |
国内免费 | 4篇 |
出版年
2023年 | 14篇 |
2022年 | 24篇 |
2021年 | 57篇 |
2020年 | 33篇 |
2019年 | 56篇 |
2018年 | 64篇 |
2017年 | 42篇 |
2016年 | 60篇 |
2015年 | 115篇 |
2014年 | 101篇 |
2013年 | 128篇 |
2012年 | 167篇 |
2011年 | 191篇 |
2010年 | 124篇 |
2009年 | 89篇 |
2008年 | 137篇 |
2007年 | 123篇 |
2006年 | 128篇 |
2005年 | 125篇 |
2004年 | 110篇 |
2003年 | 136篇 |
2002年 | 107篇 |
2001年 | 26篇 |
2000年 | 25篇 |
1999年 | 27篇 |
1998年 | 21篇 |
1997年 | 26篇 |
1996年 | 13篇 |
1995年 | 16篇 |
1994年 | 23篇 |
1993年 | 30篇 |
1992年 | 21篇 |
1991年 | 12篇 |
1990年 | 20篇 |
1989年 | 18篇 |
1988年 | 22篇 |
1987年 | 17篇 |
1986年 | 21篇 |
1985年 | 16篇 |
1984年 | 19篇 |
1983年 | 29篇 |
1982年 | 25篇 |
1981年 | 17篇 |
1980年 | 14篇 |
1979年 | 16篇 |
1978年 | 9篇 |
1977年 | 10篇 |
1975年 | 15篇 |
1974年 | 12篇 |
1973年 | 10篇 |
排序方式: 共有2698条查询结果,搜索用时 15 毫秒
61.
Yeong-Biau Yu Shang Fa Yang Joseph Corse Judy A. Kuhnle Sui-Sheng Hua 《Phytochemistry》1981,20(6):1191-1195
Twenty-five naturally occurring cytokinins and structurally related compounds were tested for their ability to promote ethylene production synergistica 相似文献
62.
Judy M. Goddard Jeffrey N. Masters Suzan S. Jones William D. Ashworth Jr. David R. Wolstenholme 《Chromosoma》1981,82(5):595-609
The mitochondrial DNA (mtDNA) molecules of different albino, domesticated rats (Rattus norvegicus) of the SASCO colony are of two kinds (SASCO-1 and SASCO-2) in regard to their sensitivity at certain sites to a number of restriction enzymes. MtDNA molecules from Utah wild R. norvegicus (Wild-UT) have sensitivities to restriction enzymes which differ at some sites from either SASCO-1 or SASCO-2 mtDNA molecules. Four single nucleotide differences were found among the HindIII F fragments (169 nucleotides) of SASCO-1, SASCO-2, and Wild-UT mtDNAs. Arguments are presented in favor of the interpretation that each variant nucleotide is the third nucleotide of the codon containing it, and that none of the four differences would result in a difference in the respective amino acid translated.Dedicated to Professor W. Beermann on the occasion of his 60th birthday 相似文献
63.
E W Kraegen R Whiteside D Bell Y O Chia L Lazarus 《Hormone and metabolic research. Supplement series》1979,(8):38-42
A closed-loop glucose controlled insulin infusion system was developed, consisting of elements for continuous blood glucose analysis, a computer control system, and infusion systems. Improvements include decreased size, cost reduction and better performance. The algorithm used was a piecewise linear representation of the sigmoidal curve commonly employed. The apparatus has been applied to simulation of the healthy beta cell and glucose clamp studies. 相似文献
64.
W K Chia 《Developmental biology》1975,44(2):239-252
The P-4 variant of Dictyostelium discoideum (DdH) was found to produce a great excess of stalk cells compared to the wild type DdH. If the vegetative cells of P-4 were repeatedly washed, the variant changed back to the wild type phenotype, and if cyclic-AMP was added to the washed P-4 cells, the variant character was restored. Furthermore, if the concentration of added cyclic-AMP was increased, it was possible to induce 100% stalk cells in P-4. Phosphodiesterase would cause the variant to change to the wild type, while 5-AMP and cyclic-nucleotides other than cyclic-AMP have no effect at all. Therefore it was concluded that cyclic-AMP plays a key role in stalk cell differentiation.A comparison between wild type DdH and the variant P-4 showed that DdH is ten times less sensitive to cyclic-AMP induction. They both produce the same amount of cyclic-AMP and extracellular phosphodiesterase, but the specific activity of P-4 cell-bound phosphodiesterase during development is significantly less than that in the DdH. One hypothesis that accounts for the P-4-DdH difference is that because of the lack of cell-bound phosphodiesterase, more cyclic-AMP enters the variant cells and hence more stalk cell differentiation. 相似文献
65.
In the use of low-level intravenous insulin infusion for treating diabetic hyperglycaemia and ketoacidosis adsorption of insulin to containers or plastic infusion apparatus results in significant losses of 60-80% of insulin in dilute physiological saline solution (40 U/l). It is therefore necessary to add protein to the carrier solution to minimize losses and maintain a constant delivery rate. Recovery studies showed that 3.5% w/v polygeline solution (polymer of degraded gelatin) was a suitable medium for this purpose, offering some advantages over human serum albumin. A minimum concentration of 0.5% polygeline was required to ensure adequate delivery of insulin to the patient. 相似文献
66.
67.
Mafalda C. O. Figueiredo Susana A. L. Lobo Sara H. Sousa Fábio P. Pereira Judy D. Wall Lígia S. Nobre Lígia M. Saraiva 《Journal of bacteriology》2013,195(11):2684-2690
Desulfovibrio species are Gram-negative anaerobic sulfate-reducing bacteria that colonize the human gut. Recently, Desulfovibrio spp. have been implicated in gastrointestinal diseases and shown to stimulate the epithelial immune response, leading to increased production of inflammatory cytokines by macrophages. Activated macrophages are key cells of the immune system that impose nitrosative stress during phagocytosis. Hence, we have analyzed the in vitro and in vivo responses of Desulfovibrio vulgaris Hildenborough to nitric oxide (NO) and the role of the hybrid cluster proteins (HCP1 and HCP2) and rubredoxin oxygen oxidoreductases (ROO1 and ROO2) in NO protection. Among the four genes, hcp2 was the gene most highly induced by NO, and the hcp2 transposon mutant exhibited the lowest viability under conditions of NO stress. Studies in murine macrophages revealed that D. vulgaris survives incubation with these phagocytes and triggers NO production at levels similar to those stimulated by the cytokine gamma interferon (IFN-γ). Furthermore, D. vulgaris
hcp and roo mutants exhibited reduced viability when incubated with macrophages, revealing that these gene products contribute to the survival of D. vulgaris during macrophage infection. 相似文献
68.
69.
70.
A simple technique is described for the detection of membrane-associated antigens on lymphoid cells. It is based on the observation that the protein A component of staphylococci binds to the Fc pieces of IgG molecules. Lymphocytes from various sources (mouse, rat, and human tissues) were incubated with hyperimmune antisera directed against surface determinants. Subsequent treatment with a suspension of staphylococci containing protein A permitted visualization of both the presence and distribution of determinants on the cell membrane. The method had comparable sensitivity to the fluorescent sandwich technique and could be used to detect a variety of membrane antigens on both T cells and B cells. 相似文献