全文获取类型
收费全文 | 1892篇 |
免费 | 203篇 |
国内免费 | 1篇 |
出版年
2023年 | 8篇 |
2021年 | 44篇 |
2020年 | 26篇 |
2019年 | 44篇 |
2018年 | 48篇 |
2017年 | 35篇 |
2016年 | 49篇 |
2015年 | 92篇 |
2014年 | 89篇 |
2013年 | 103篇 |
2012年 | 157篇 |
2011年 | 130篇 |
2010年 | 89篇 |
2009年 | 83篇 |
2008年 | 112篇 |
2007年 | 84篇 |
2006年 | 104篇 |
2005年 | 78篇 |
2004年 | 88篇 |
2003年 | 74篇 |
2002年 | 77篇 |
2001年 | 26篇 |
2000年 | 29篇 |
1999年 | 33篇 |
1998年 | 26篇 |
1997年 | 26篇 |
1996年 | 10篇 |
1995年 | 12篇 |
1994年 | 16篇 |
1993年 | 17篇 |
1992年 | 17篇 |
1991年 | 23篇 |
1990年 | 16篇 |
1989年 | 17篇 |
1988年 | 16篇 |
1987年 | 14篇 |
1986年 | 17篇 |
1985年 | 17篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 9篇 |
1981年 | 11篇 |
1980年 | 10篇 |
1979年 | 15篇 |
1978年 | 10篇 |
1977年 | 7篇 |
1975年 | 8篇 |
1974年 | 10篇 |
1973年 | 9篇 |
1972年 | 10篇 |
排序方式: 共有2096条查询结果,搜索用时 31 毫秒
31.
A Mutation in the D-de Loop of D1 Modifies the Stability of the S2QA- and S2QB- States in Photosystem II 总被引:1,自引:0,他引:1
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)
Maenpaa P Miranda T Tyystjarvi E Tyystjarvi T Govindjee Ducruet JM Etienne AL Kirilovsky D 《Plant physiology》1995,107(1):187-197
Photosystem II electron transfer, charge stabilization, and photoinhibition were studied in three site-specific mutants of the D1 polypeptide of Synechocystis PCC 6803: E243K, E229D, and CA1 (deletion of three glutamates 242-244 and a substitution, glutamine-241 to histidine). The phenotypes of the E229D and E243K mutants were similar to that of the control strain (AR) in all of the studied aspects. The characteristics of CA1 were very different. Formate, which inhibits the QA- to QB- reaction, was severalfold less effective in CA1 than in AR. The S2QA- and S2QB- states were stabilized in CA1. It was previously shown that the electron transfer between QA- and QB was modified in CA1 (P Maenpaa, T. Kallio, P. Mulo, G. Salih, E.-M. Aro, E. Tyystjarvi, C. Jansson [1993] Plant Mol Biol 22: 1-12). A change in the redox potential of the QA/QA- couple, which renders the reoxidation of QA- by back or forward reactions more difficult, could explain the phenotype of CA1. Although the rates of photoinhibition measured as inhibition of oxygen evolution, Chl fluorescence quenching, and decrease of thermoluminescence B and Q bands were similar in AR and CA1, the CA1 strain more quickly reached a state from which the cells were unable to recover their activity. The results described in this paper suggest that a modification in the structure of the D-de loop of D1 could influence the properties of the couple QA/QA- in D2 and the mechanism of recovery from photoinhibition. 相似文献
32.
Etienne H.; Lartaud M.; Carron M.P.; Michaux-Ferrire N. 《Journal of experimental botany》1997,48(1):129-137
In Hevea brasiliensis (Mll. Arg.), increasing the calcium contentof the friable callus maintenance medium from 3 to 9 mM stimulatedregeneration potential through somatic embryogenesis. This stimulationcould be attributed to the homogeneous cytological structureof calluses, which were formed of undifferentiated cells capableof somatic embryogenesis in optimal culture conditions. Thevery marked increase in the active cell population was sufficientto cause a decrease and a stabilization of water and osmoticpotentials of the calluses, whereas their water content increased.The regeneration capacity of calluses cultured on a medium withadditional CaCl2 was greater in terms of both quantity (numberof somatic embryos produced was increased 2-fold) and quality(germination efficiency trebled). High CaCl2 concentrations (9 mM CaCl2) in the embryogenesisinduction medium favoured somatic embryo development when calluseswere maintained 2 months on the same medium. In this case, additionof benzylaminopurine (BAP) and 3,4-dichlorophenoxy- acetic acid(3,4-D) increased the number of embryos produced (243 embryosg1 FW callus) and their germination capacity (27%). These culture conditions were used to determine the optimumembryogenesis induction period. The length of the period affectedboth the intensity of embryogenesis (maximum 5677 d)and somatic embryo quality (maximum 4970 d). The bestresults were obtained with a 70 d embryogenesis induction period,within which 355 embryos g1 FW callus were obtained,with 35% germination. Key words: Calcium, somatic embryogenesis, long-term culture, water status, histology 相似文献
33.
Cees Hol Cees M. Verduin Etienne E.A. Van Dijke Jan Verhoef ré Fleer Hans van Dijk 《FEMS immunology and medical microbiology》1995,11(3):207-211
Abstract The purpose of this study was to investigate complement resistance in Branhamella (Moraxella) catarrhalis isolated from healthy schoolchildren or sputum-producing adult patients. Two techniques were used: a serum bactericidal assay as the gold standard and an easier ‘culture and spot’ test. Children (age 4–13; n = 303) and patients ( n = 1047) showed high colonization/infection rates with B. catarrhalis (31% and 19%, respectively). Complement resistance or intermediate sensitivity occurred frequently in patient isolates (62% and 27%, respectively) and less often in children (33% and 8.5%, respectively; P ⪡ 0.0001). In young children (age 4–5 years), the proportion of complement-resistant strains was around 50%. Complement resistance in B. catarrhalis is associated with illness and may hence be considered a virulence factor. 相似文献
34.
35.
Willy J. Malaisse Kowluru Anjaneyulu Renu Anjaneyulu Etienne Couturier 《Molecular and cellular biochemistry》1980,30(2):67-70
Summary In an artificial system, the ionophore A23187, which transports Ca2+ but not Na+, is able to mediate the uphill translocation of Ca2+ from one aqueous medium to another across an organic immiscible phase, provided that a Na+, Li+ or H+ gradient is imposed on the system. Therefore, in the process known as Na-Ca countertransport, the downhill influx of Na+ may not be necessary for causing Ca2+ extrusion against its electrochemical gradient. 相似文献
36.
The antibiotic ionophore ionomycin translocates Ca from an aqueous medium into or across an organic immiscible phase. At pH 8.0, ionomycin translocates less Ca than A23187, the effects of these ionophores being additive to one another. The capacity of ionomycin to translocate Ca across the organic phase is dramatically decreased when the pH of the aqueous media is reduced from 8.0 to 7.5 or lower values. Ionomycin also mediates Ca exchange-diffusion in liposomes, the magnitude of such a process being greater in fluid than in rigid liposomes. At a physiological pH (7.4), ionomycin is unexpectedly as potent as A23187 in mediating Ca transport in fluid liposomes. These findings suggest that the capacity of ionophores to translocate Ca across model membranes depends on both the transverse and lateral mobility of the ionophoretic molecules. The relative importance of the latter phenomenon itself largely depends on the stoichiometry of the Ca-ionophore complex. 相似文献
37.
38.
Josette Martin-Tanguy Ferdinand Cabanne Etienne Perdrizet Claude Martin 《Phytochemistry》1978,17(11):1927-1928
Hydroxycinnamic acid amides have been identified as the main phenolic constituents in the reproductive organs of a range of flowering plants. 相似文献
39.
Structural and functional relationships between Pasteurella multocida and enterobacterial adenylate cyclases. 总被引:3,自引:2,他引:1
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)
The Pasteurella multocida adenylate cyclase gene has been cloned and expressed in Escherichia coli. The primary structure of the protein (838 amino acids) deduced from the corresponding nucleotide sequence was compared with that of E. coli. The two enzymes have similar molecular sizes and, based on sequence conservation at the protein level, are likely to be organized in two functional domains: the amino-terminal catalytic domain and the carboxy-terminal regulatory domain. It was shown that P. multocida adenylate cyclase synthesizes increased levels of cyclic AMP in E. coli strains deficient in the catabolite gene activator protein compared with wild-type strains. This increase does not occur in strains deficient in both the catabolite gene activator protein and enzyme III-glucose, indicating that a protein similar to E. coli enzyme III-glucose is involved in the regulation of P. multocida adenylate cyclase. It also indicates that the underlying process leading to enterobacterial adenylate cyclase activation has been conserved through evolution. 相似文献
40.
A gene encoding a tyrosine tRNA synthetase is located near sacS in Bacillus subtilis. 总被引:10,自引:0,他引:10
Within the frame of an attempt to sequence the whole Bacillus subtilis genome, a region of 5.5 kbp of the B. subtilis chromosome near the sacS locus has been sequenced. It contains five complete coding sequences, including the sequence of sacY, three unknown CDS and a sequence coding for a tyrosine tRNA synthetase. That the corresponding CDS encodes a functional synthetase has been demonstrated by complementation of an Escherichia coli mutant possessing a thermosensitive tRNA synthetase. Insertion of a kanamycin resistance cassette in the B. subtilis chromosome at the corresponding locus resulted, however, in no apparent phenotype, demonstrating that this synthetase is dispensable. Finally phylogenetic relationships between known tyrosine and tryptophan tRNA synthetases are discussed. 相似文献