全文获取类型
收费全文 | 4585篇 |
免费 | 500篇 |
国内免费 | 4篇 |
出版年
2021年 | 74篇 |
2019年 | 47篇 |
2018年 | 70篇 |
2017年 | 54篇 |
2016年 | 100篇 |
2015年 | 115篇 |
2014年 | 161篇 |
2013年 | 195篇 |
2012年 | 250篇 |
2011年 | 255篇 |
2010年 | 190篇 |
2009年 | 132篇 |
2008年 | 267篇 |
2007年 | 241篇 |
2006年 | 175篇 |
2005年 | 180篇 |
2004年 | 180篇 |
2003年 | 161篇 |
2002年 | 165篇 |
2001年 | 98篇 |
2000年 | 85篇 |
1999年 | 90篇 |
1998年 | 64篇 |
1997年 | 54篇 |
1996年 | 56篇 |
1995年 | 48篇 |
1994年 | 41篇 |
1993年 | 46篇 |
1992年 | 81篇 |
1991年 | 86篇 |
1990年 | 69篇 |
1989年 | 73篇 |
1988年 | 85篇 |
1987年 | 53篇 |
1986年 | 59篇 |
1985年 | 51篇 |
1984年 | 59篇 |
1983年 | 49篇 |
1982年 | 36篇 |
1981年 | 39篇 |
1980年 | 48篇 |
1979年 | 49篇 |
1978年 | 48篇 |
1976年 | 45篇 |
1975年 | 33篇 |
1974年 | 34篇 |
1973年 | 42篇 |
1972年 | 33篇 |
1970年 | 33篇 |
1969年 | 33篇 |
排序方式: 共有5089条查询结果,搜索用时 15 毫秒
41.
42.
43.
44.
Summary The inheritance of both the mitochondrial DNA (mtDNA) and the nuclear-encoded extrachromosomal ribosomal DNA (rDNA) has been studied in the myxomycete, Didymium iridis, by DNA-DNA hybridization of labeled probes to total DNA at various stage of the life cycle. Both the mtDNA and rDNA populations rapidly become homogeneous in individuals, but there is a qualitative difference in the patterns of inheritance of these two molecules. One parental rDNA type was preferentially inherited in all crosses; selective replication of this molecule is tentatively proposed as the mechanism of inheritance. In contrast, either parental mtDNA type could be inherited. Since the inherited population of parental mtDNA molecules are not partitioned into cells in this coenocytic organism, no known mechanism of inheritance can explain the rapid and apparently random loss of one parental mtDNA type in individuals. 相似文献
45.
Inhibition of Nitrate Transport by Anti-Nitrate Reductase IgG Fragments and the Identification of Plasma Membrane Associated Nitrate Reductase in Roots of Barley Seedlings 总被引:4,自引:2,他引:2
下载免费PDF全文
![点击此处可从《Plant physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Membrane associated nitrate reductase (NR) was detected in plasma membrane (PM) fractions isolated by aqueous two-phase partitioning from barley (Hordeum vulgare L. var CM 72) roots. The PM associated NR was not removed by washing vesicles with 500 millimolar NaCl and 1 millimolar EDTA and represented up to 4% of the total root NR activity. PM associated NR was stimulated up to 20-fold by Triton X-100 whereas soluble NR was only increased 1.7-fold. The latency was a function of the solubilization of NR from the membrane. NR, solubilized from the PM fraction by Triton X-100 was inactivated by antiserum to Chlorella sorokiniana NR. Anti-NR immunoglobulin G fragments purified from the anti-NR serum inhibited NO3− uptake by more than 90% but had no effect on NO2− uptake. The inhibitory effect was only partially reversible; uptake recovered to 50% of the control after thorough rinsing of roots. Preimmune serum immunoglobulin G fragments inhibited NO3− uptake 36% but the effect was completely reversible by rinsing. Intact NR antiserum had no effect on NO3− uptake. The results present the possibility that NO3− uptake and NO3− reduction in the PM of barley roots may be related. 相似文献
46.
47.
Peter O''Connell G. Mark Lathrop Mark Leppert Yusuke Nakamura Ulrich Müller Jean-Marc Lalouel Ray White 《Genomics》1988,3(4):367-372
We have constructed a primary genetic map of human chromosome 18 consisting of 11 DNA markers and one serological marker (JK). Two of these loci define highly polymorphic VNTR systems. The markers define a continuous genetic linkage map of 97 cM in males and 205 cM in females; female genetic distances in a panel of 59 three-generation families were consistently about twice those observed in males. The high odds in support of the linear order of the markers on this recombination map, and the extent of coverage of chromosome 18, indicate that this map will permit efficient linkage studies of human genetic diseases that may be segregating on chromosome 18 and will provide anchor points for development of high-resolution maps for this chromosome. 相似文献
48.
Purification, characterization and antimicrobial spectrum of a bacteriocin produced by Pediococcus acidilactici 总被引:8,自引:4,他引:4
An antimicrobial peptide designated pediocin AcH was isolated from Pediococcus acidilactici strain H. The pediocin AcH was purified by ion exchange chromatography. The molecular weight of pediocin AcH was determined by SDS-PAGE to be about 2700 daltons. Pediocin AcH was sensitive to proteolytic enzymes, resistant to heat and organic solvents, and active over a wide range of pH. Pediocin AcH exhibited inhibition against several food spoilage bacteria and foodborne pathogens including Staphylococcus aureus, Clostridium perfringens and Listeria monocytogenes. It was bactericidal to sensitive cells and acted very rapidly. The bactericidal effect was not produced by either cell lysis or apparent loss of membrane permeability. 相似文献
49.
Sixty-nine strains of bacteria isolated from murcha and ragi (amylase starters) were studied. These came from 14 different amylase starters from Java, Bali, and Nepal and were isolated from dilution plates incubated under aerobic and anaerobic conditions. Most belonged to Pediococcus , probably P. pentosaceus , and to Streptococcus faecalis. None were able to attack starch although they are used in starch fermentations. When inoculated on rice as pure cultures most of them failed to show visible growth unless yeasts and moulds were added at the same time. The roles of these bacteria are unknown but they may produce secondary products from the glucose formed by the amylolytic yeasts and moulds always found in the starters. 相似文献
50.
Immunization of mice with a synthetic GM3-lactam-BSA (bovine serum albumin) conjugate (designed to emulate the corresponding natural GM3-lactone conjugate), followed by fusion of splenocytes with myeloma cells, gave rise to more than 300 monoclonal hybridomas producing antibodies to GM3-lactam-BSA, which did not react with Glc-BSA and BSA. Eight antibody clones were randomly chosen from the positive 300 hybridomas. The eight clones, all belonging to the IgG class, were unreactive against GM3-ganglioside, whereas two antibodies (P5-1 and P5-3, both IgG1, ) reacted with GM3-ganglioside lactone. Binding of these two antibodies to the GM3-lactam-BSA conjugate was inhibited by soluble glycosides of GM2-, GM3-, and GM4-lactam and by GM3- and GM4-lactam, respectively, but not by Gb3 or asialo-GM1 and GM2-saccharides. A third antibody (P3; IgG2b, ) was inhibited by GM2-, GM3-, and GM4-lactam, but did not recognize GM3-ganglioside lactone. 相似文献