全文获取类型
收费全文 | 4673篇 |
免费 | 575篇 |
国内免费 | 2篇 |
出版年
2021年 | 36篇 |
2016年 | 52篇 |
2015年 | 94篇 |
2014年 | 114篇 |
2013年 | 145篇 |
2012年 | 195篇 |
2011年 | 208篇 |
2010年 | 136篇 |
2009年 | 153篇 |
2008年 | 238篇 |
2007年 | 205篇 |
2006年 | 183篇 |
2005年 | 192篇 |
2004年 | 197篇 |
2003年 | 179篇 |
2002年 | 199篇 |
2001年 | 102篇 |
2000年 | 104篇 |
1999年 | 102篇 |
1998年 | 80篇 |
1997年 | 71篇 |
1996年 | 75篇 |
1995年 | 60篇 |
1994年 | 52篇 |
1993年 | 59篇 |
1992年 | 97篇 |
1991年 | 71篇 |
1990年 | 97篇 |
1989年 | 93篇 |
1988年 | 97篇 |
1987年 | 91篇 |
1986年 | 74篇 |
1985年 | 95篇 |
1984年 | 77篇 |
1983年 | 67篇 |
1982年 | 87篇 |
1981年 | 68篇 |
1980年 | 65篇 |
1979年 | 79篇 |
1978年 | 89篇 |
1977年 | 67篇 |
1976年 | 54篇 |
1975年 | 52篇 |
1974年 | 67篇 |
1973年 | 63篇 |
1972年 | 54篇 |
1971年 | 34篇 |
1970年 | 41篇 |
1968年 | 35篇 |
1967年 | 33篇 |
排序方式: 共有5250条查询结果,搜索用时 15 毫秒
11.
12.
Brigitte Aupetit Alexandre Ghazi Nicole Blanchouin Ren e Toury Emmanuel Shechter Jean-Claude Legrand 《BBA》1988,936(3):325-331
In this study we have measured, under experimental conditions which maintained efficient coupling, respiratory intensity, respiratory control, oxidative phosphorylation capacity and protonmotive force. Succinate cytochrome-c reductase and cytochrome-c oxidase activities were also studied. These investigations were carried out using kidney mitochondria from cyclosporine-treated rats (in vivo studies) and from untreated rats in the presence of cyclosporine (in vitro studies). Inhibition of respiratory intensity by cyclosporine did not exceed 21.1% in vitro and 15.9% in vivo. Since there was no in vitro inhibition of succinate cytochrome-c reductase and cytochrome-c oxidase activities, the slowing of electron flow observed can be interpreted as a consequence of an effect produced by cyclosporine between cytochromes b and c1. Cyclosporine had no effect on respiratory control either in vitro or in vivo. Statistically significant inhibition of the oxidative phosphorylation was observed both in vitro (6.6%) and in vivo (12.1%). Moreover, cyclosporine did not induce any change of membrane potential either in vivo or in vitro. Our findings show that cyclosporine is neither a protonophore, nor a potassium ionophore. In cyclosporine-treated rats we noticed a decrease of protein in subcellular fraction, including the mitochondrial fraction. The role of the inhibition respiratory characteristics by cyclosporine in nephrotoxicity in vivo must take account of these two parameters: inhibition of the respiratory characteristics measured in vitro and diminution of mitochondrial protein in cyclosporine-treated rats. 相似文献
13.
14.
Partial characterization and purification of the glycosylation site recognition component of oligosaccharyltransferase 总被引:3,自引:0,他引:3
Oligosaccharyltransferase, the enzyme catalyzing the co-translational transfer of oligosaccharide from dolichyl-PP-GlcNAc2Man9Glc3 to -Asn-X-Ser/Thr- sequences in nascent polypeptide chains, was studied in hen oviduct microsomes using the active site-directed photoaffinity probe 125I-labeled N alpha-3-(4-hydroxyphenylpropionyl)-Asn-Lys(N epsilon-p-azidobenzoyl)-Thr-NH2. Several lines of evidence established that the tripeptide probe interacted with a 57-kDa protein of the endoplasmic reticulum that was subsequently glycosylated and converted to a 60-kDa form. The 57-kDa protein, isolated by two-dimensional gel electrophoresis, was used as immunogen to prepare polyclonal antisera. The specificity of the antibody was established on the basis of its ability to 1) recognize the 57-kDa protein by immunoblotting and 2) immunoprecipitate the photolabeled protein. The antibody also recognized photolabeled protein from different tissues and organisms. The 57-kDa protein isolated by immunoprecipitation retained its ability to interact with the photoaffinity probe but was inactive in catalyzing glycosylation of peptides. This result suggests that the 57-kDa protein is the component of oligosaccharyltransferase that recognizes the glycosylation site in polypeptides. These results are discussed in terms of possible models for the structure of oligosaccharyltransferase in the endoplasmic reticulum. 相似文献
15.
To see if a Vitamin B6 deficiency is responsible for seizure-proneness in the gerbil, , a diet supplemented with 0.5mg of pyridoxine per gram of Purina Lab Chow was fed to 8 experimental (E) mated pairs and their litters while 8 control (C) pairs and their litters were fed Purina Lab Chow which contains .004mg per gram of pyridoxine. All litters were tested for seizures every 2 weeks from 2 through 7 mos. of age once a month in a standard (SS) test cage and 2 weeks later in a clean home cage (CC) — and again at 1 yr in the SS cage. There were no differences on any of the measures between E and C litters. Significantly more seizures were elicited in the SS than in the CC tests, and the SS test became increasingly more effective with age. It was concluded that gerbil seizures were not due to a Vitamin B6 deficiency and that some age-related process might be a productive area for future investigation. 相似文献
16.
We review the literature on the surgical treatment of necrobiosis lipoidica diabeticorum, and we describe 7 cases treated at Stanford University Medical Center. Experiences with them prompt us to recommend surgical excision of the lesions down to the deep fascia, ligation of the associated perforating blood vessels, and the use of split-skin grafts to cover the defects. There were no recurrences when we did all these things. 相似文献
17.
Hybrid cells formed by the fusion of murine teratocarcinoma and Friend erythroleukemia cells synthesize hemoglobin in the presence of chemical inducers such as dimethylsulfoxide (DMSO). By making use of the fact that the parental teratocarcinoma and Friend cells carried different alleles at the locus coding for the alpha chain of hemoglobin, it was possible to demonstrate that the teratocarcinoma-derived genes for the globin alpha chains are genetically active in hemoglobin-synthesizing hybrid cells. In addition, evidence is presented suggesting that the teratocarcinoma-derived genes for the beta-globin chains may also be expressed in the hybrids. Apparently the teratocarcinoma-derived genome has become reprogrammed to express erythroid functions following fusion of the teratocarcinoma cell to the Friend cell. 相似文献
18.
Michel Fons Brigitte Cami Jean-Claude Patte Marc Chippaux 《Molecular & general genetics : MGG》1987,206(1):141-143
Summary A library of Deusulfovibrio desulfuricans Norway genomic DNA was constructed in Escherichia coli with pBR322 as vector and plasmids able to complement the proA and leuB mutations of the host were screened. It was observed that all the plasmids studied were highly unstable, the insert DNA being rapidely lost under non-selective growth conditions. A 2.75 kb DNA fragment of D. desulfuricans Norway was found to complement E. coli ProA, ProB and ProC deficiencies. From the results of restriction analysis and Southern hybridization, it is proposed that the genes involved in proline and leucine biosynthesis are clustered on the chromosome of D. desulfuricans Norway. 相似文献
19.
Energization and activation of inorganic carbon uptake by light in cyanobacteria 总被引:11,自引:3,他引:8
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)
The requirement of the inorganic carbon (Ci) transport system for light in cyanobacteria was investigated in Anabaena variabilis by the filtering centrifugation technique and in a mutant (E1) isolated from Anacystis nidulans using a gas exchange system. Ci transport capability increased with time of preillumination and decreased following darkening. Full activity could not be obtained by operating either photosystem II (PSII) or photosystem I alone. 3(3,4 Dichlorophenyl)-1,1 dimethylurea strongly inhibited Ci uptake. Very low activity of PSII was sufficient to activate Ci uptake. However, in the presence of dithiothreitol PSII activity was not required. We conclude that light may be required to activate as well as to energize Ci uptake in cyanobacteria. 相似文献
20.