全文获取类型
收费全文 | 3501篇 |
免费 | 301篇 |
国内免费 | 1篇 |
出版年
2023年 | 15篇 |
2022年 | 45篇 |
2021年 | 76篇 |
2020年 | 46篇 |
2019年 | 50篇 |
2018年 | 64篇 |
2017年 | 62篇 |
2016年 | 104篇 |
2015年 | 187篇 |
2014年 | 190篇 |
2013年 | 233篇 |
2012年 | 320篇 |
2011年 | 325篇 |
2010年 | 197篇 |
2009年 | 178篇 |
2008年 | 194篇 |
2007年 | 169篇 |
2006年 | 133篇 |
2005年 | 142篇 |
2004年 | 163篇 |
2003年 | 119篇 |
2002年 | 102篇 |
2001年 | 24篇 |
2000年 | 28篇 |
1999年 | 35篇 |
1998年 | 41篇 |
1997年 | 29篇 |
1996年 | 26篇 |
1995年 | 18篇 |
1994年 | 19篇 |
1993年 | 30篇 |
1992年 | 33篇 |
1991年 | 22篇 |
1990年 | 20篇 |
1989年 | 15篇 |
1988年 | 20篇 |
1986年 | 15篇 |
1985年 | 17篇 |
1984年 | 23篇 |
1983年 | 15篇 |
1982年 | 24篇 |
1981年 | 16篇 |
1979年 | 13篇 |
1978年 | 18篇 |
1977年 | 22篇 |
1976年 | 14篇 |
1975年 | 14篇 |
1974年 | 13篇 |
1973年 | 17篇 |
1972年 | 17篇 |
排序方式: 共有3803条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Detergent soluble extracts of differentiated regions of the Porphyra perforata J. Ag. thallus (holdfast, rhizoidal, vegetative and reproductive cells) were fractionated on sodium dodecyl sulfate polyacrylamide gels. Glycoproteins were identified by their lectin affinity. Extracts from all areas of the thallus contained glycoproteins, but the staining patterns were different for each region with each of the lectins tested: concanavalin A, Ulex europeaus agglutinin, Ricinus communis agglutinin, soybean agglutinin and peanut agglutinin. These data indicate that the morphologically distinct regions of the thallus also differ biochemically. Analysis of the lectin blots revealed the presence of tissue-specific glycoproteins in the five thallus areas. Such unique glycoproteins could be used as markers of differentiation in this species. 相似文献
5.
Tn916-induced mutations in the hemolysin determinant affecting virulence of Listeria monocytogenes. 总被引:80,自引:8,他引:72
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A genetic determinant essential for hemolysin production by Listeria monocytogenes has been inactivated by insertion of transposon Tn916 into L. monocytogenes DNA. The transposon was transferred by means of conjugation of a streptomycin-resistant L. monocytogenes recipient strain with Streptococcus faecalis CG110 on membrane filters. Among the tetracycline-resistant transconjugants, mutants were detected which had lost hemolytic activity. When tested in a mouse model, these mutants appeared to have lost the virulence that characterizes the parental strain. An extracellular protein of 58,000 apparent molecular weight was eliminated in the nonhemolytic mutants. In some of the mutants, the decrease in the production of the 58,000-dalton protein was accompanied by the production of a new protein of 49,000 apparent molecular weight. Hemolytic revertants regained the hemolytic phenotype and virulence and produced the extracellular protein that characterizes the recipient strain. Hybridization studies with Tn916 DNA indicated that the transposon is present in EcoRI and HindIII fragments of the nonhemolytic mutants. Single copies of Tn916 were detected in the chromosomal DNA of two of the three nonhemolytic mutants that were studied in detail. In hemolytic, tetracycline-sensitive revertants Tn916 appeared to be completely excised from the chromosome. 相似文献
6.
7.
A Bacillus cereus cytolytic determinant, cereolysin AB, which comprises the phospholipase C and sphingomyelinase genes: nucleotide sequence and genetic linkage. 总被引:28,自引:6,他引:22
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
M S Gilmore A L Cruz-Rodz M Leimeister-Wchter J Kreft W Goebel 《Journal of bacteriology》1989,171(2):744-753
A cloned cytolytic determinant from the genome of Bacillus cereus GP-4 has been characterized at the molecular level. Nucleotide sequence determination revealed the presence of two open reading frames. Both open reading frames were found by deletion and complementation analysis to be necessary for expression of the hemolytic phenotype by Bacillus subtilis and Escherichia coli hosts. The 5' open reading frame was found to be nearly identical to a recently reported phospholipase C gene derived from a mutant B. cereus strain which overexpresses the respective protein, and it conferred a lecithinase-positive phenotype to the B. subtilis host. The 3' open reading frame encoded a sphingomyelinase. The two tandemly encoded activities, phospholipase C and sphingomyelinase, constitute a biologically functional cytolytic determinant of B. cereus termed cereolysin AB. 相似文献
8.
haemolysin of Escherichia coli: Comparison of pore-forming properties between chromosome and plasmid-encoded haemolysins 总被引:3,自引:0,他引:3
Roland Benz reas Döbereiner Albrecht Ludwig Werner Goebel 《FEMS microbiology letters》1992,105(1-3):55-62
Abstract Lipid bilayer experiments were performed with chromosome-encoded haemolysin of Escherichia coli . The addition of the toxin to the aqueous phase bathing lipid bilayer membranes of asolectin resulted in the formation of transient ion-permeable channels with two states at small transmembrane voltages. One is prestate (single-channel conductance 40 pS in 0.15 M KCl) of the open state, which had a single-channel conductance of 420 pS in 0.15 M KCl and a mean lifetime of 30 s. Membranes formed of pure lipids were rather inactive targets for this haemolysin. Experiments with different salts suggested that the haemolysin channel was highly cation-selective at neutral pH. The mobility sequence of the cations in the channel was similar if not identical to their mobility sequence in the aqueous phase. The single-channel data were consistent with a wide, water-filled channel with an estimated minimal diameter of about 1 nm. The pore-forming properties of chromosome-encoded haemolysin were compared with those of plasmid-encoded haemolysin. Both toxins share common features, oligomerize probably to form pores in lipid bilayer membranes. Both types of haemolysin channels have similar properties but different lifetimes. 相似文献
9.
Valerie J. Horn Paul A. Sheehy Miriam B. Goodman Indu S. Ambudkar 《Molecular and cellular biochemistry》1991,101(1):43-49
Intracellular Ca2+ mobilization events were assessed in mouse L cells, which contain native prostaglandin E1 receptors and transfected human 2 adrenergic receptors. Both Fura2 (single cell measurements) and Quin 2, (cuvette assays) were used to determine [Ca2+]i levels. Our results demonstrate that in the transfected cells there is a dose-dependent increase in [Ca2+]i in response to isoproterenol (0.1 nM–100 nM), which is inhibited by the -adrenergic antagonist, propranolol, and is a result of intracellular Ca2+ release. [Ca2+]1 in these cells was also increased by prostaglandin E1, 8 bromo cyclic AMP, and aluminum fluoride. Both 8 bromo cAMP and isoproterenol induced a rapid increase in the levels of IP1, IP2, and IP3. The data presented demonstrate that the elevation of intracellular cyclic AMP induces an increase in IP3 production which leads to an elevation in [Ca2+];. We propose that this cyclic AMP dependent activation of the IP3 generating system occurs at a post-receptor site.Abbreviations cAMP
Adenosine Cyclic 3-5-Monophosphate
- [Ca2+]i
intracellular [Ca2+]i
- 8 Br cAMP
8 Bromo Adenosine Cyclic 3-5-Monophosphate
- DAG
Diacylglycerol
- EGTA]
[Ethylene Bis (oxyethylenenitrilo)] Tetracetic acid
- BSA
Bovine Serum Albumin
- HBSS-H
Hanks' Balanced Salt Solution buffered with HEPES to pH 7.4
- HEPES
4-(2-Hydroxyethyl)-1-piperazineethanesulfonic acid
- PIP2
Phosphatidylinositol 4,5-bisphosphate
- IP2
Inositol 4 Phosphate
- IP2
Inositol 4,5 Bisphosphate
- IP3
Inositol Trisphosphate
- PGE1
Prostaglandin E1
- PBS
Phosphate Buffered Saline Solution 相似文献
10.
Summary Induction of Epstein-Barr virus (EBV) capsid antigen synthesis in 59.6% of P3HR-1 cells was followed by a decrease to 70% in adenosine deaminase (ADA) activity. In Daudi cells synthesizing EBV early antigen, ADA activity did not decrease. 相似文献