全文获取类型
收费全文 | 379篇 |
免费 | 41篇 |
出版年
2023年 | 3篇 |
2019年 | 12篇 |
2018年 | 12篇 |
2017年 | 11篇 |
2016年 | 16篇 |
2015年 | 9篇 |
2014年 | 12篇 |
2013年 | 15篇 |
2012年 | 20篇 |
2011年 | 10篇 |
2010年 | 11篇 |
2009年 | 18篇 |
2008年 | 16篇 |
2007年 | 18篇 |
2006年 | 9篇 |
2005年 | 8篇 |
2004年 | 9篇 |
2003年 | 14篇 |
2002年 | 10篇 |
2001年 | 10篇 |
2000年 | 13篇 |
1999年 | 4篇 |
1997年 | 8篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 8篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 6篇 |
1979年 | 11篇 |
1978年 | 6篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 7篇 |
1973年 | 5篇 |
1972年 | 3篇 |
1971年 | 7篇 |
1970年 | 5篇 |
1969年 | 4篇 |
1968年 | 10篇 |
1967年 | 3篇 |
1966年 | 2篇 |
排序方式: 共有420条查询结果,搜索用时 15 毫秒
1.
The kinetics of the electrostatically induced phase transition of dimyristoyl phosphatidic acid bilayers was followed using the stopped-flow technique. The phase transition was triggered by a fast change in the pH or the magnesium ion concentration and followed by recording the time dependence of the absorbance. When the phase transition was induced by a pH jump the time course of the absorbance could be described by two exponentials, their time constants displaying the for cooperative processes characteristic maximum at the transition midpoint. The time constants are in the 10 and 100 ms range for the H+ triggered transition from the fluid to the ordered state. A third slower process shows no appreciable temperature dependence and is probably caused by vesicle aggregation. For the OH--induced transition fron the ordered to the fluid state the time constants are in the 100 and 1000 ms range. The fluid-ordered transition could also be triggered by addition of magnesium ions. Of the several observed processes only the fastest in the 10–100 ms time range could definitely be assigned to the fluid-ordered transition while the others are due to aggregation phenomena. The experimental data were compared with results obtained from pressure jump experiments and could be interpreted on the basis of theories for non-equilibrium relaxation. 相似文献
2.
P Blume 《Cytometry》1989,10(3):351-353
A simple, rapid, and accurate method is described for the determination of flow cytometer stream sample core diameters. A precisely formulated solution of potassium dichromate is introduced as a sample, the stream is collected, and its absorbance is measured using a spectrophotometer. This permits the calculation of the factor by which the original solution was diluted and, given the stream diameter, the sample core diameter. 相似文献
3.
4.
Two different cDNA clones denoted pTO270-6 and pTO270-11 represent two mRNAs that are developmentally regulated during spore germination in Dictyostelium discoideum. The respective mRNAs are found only during early germination and are not present in other stages of growth or multicellular development. Four different genomic clones that hybridize to sequences that are common to both of the 270 cDNA clones were isolated from Dictyostelium libraries and sequenced. Two are the genes for the two cDNAs, and the other two represent genes that do not seem to be transcribed. All four genomic sequences possess a very unusual internal feature in the deduced protein sequences composed of a monotonous repeat of the tetrapeptide threonine-glutamic acid-threonine-proline. The other portions of the proteins have no homology among themselves. The deduced protein corresponding to the 270-6 gene is very similar to avocado (Persea americana) cellulase. Since cellulose in the spore wall has to be digested during spore germination this suggests that this protein may function as an endo-(1,4)-beta-D-glucanase during germination. 相似文献
5.
H. -W. Helb H. -H. Bergmann E. Bezzel D. S. Peters K. Witt D. Blume und R. Prinzinger 《Journal of Ornithology》1985,126(4):449-460
Ohne Zusammenfassung 相似文献
6.
Summary In 214 healthy young Germans the activity of Pyruvatekinase from red blood cells has been determined. Three persons had values in the heterozygote range between 10.0 and 20.0 U. Suggesting a 2-allele-model the frequency of the three phenotypes in the German population can be calculated as followed: PK(A)=98.6%, PK(AB)=1.4%, PK(B)=0.005%.No correlation could be found between the distribution of blood-and serum-groups and the enzyme-activity.
Direktor: Prof. Dr. med. G. W. Löhr
Direktor: Prof. Dr. med. G. G. Wendt
Mit dankenswerter Unterstützung durch die Deutsche Volkswagen-Stiftung.
Herrn Professor Dr.H. E. Bock, Tübingen, zum 65. Geburtstag gewidmet. Wesentliche Teile dieser Arbeit werden von Olaf Praetsch der Medizinischen Fakultät als Dissertation vorgelegt. 相似文献
Direktor: Prof. Dr. med. G. W. Löhr
Direktor: Prof. Dr. med. G. G. Wendt
Mit dankenswerter Unterstützung durch die Deutsche Volkswagen-Stiftung.
Herrn Professor Dr.H. E. Bock, Tübingen, zum 65. Geburtstag gewidmet. Wesentliche Teile dieser Arbeit werden von Olaf Praetsch der Medizinischen Fakultät als Dissertation vorgelegt. 相似文献
7.
8.
Isoniazid inactivation was studied in a sample of 100 subjects from Central Thailand. The frequency of the allele AcS (resulting in slow inactivation in the homozygous state) was calculated as 0.755. There is evidence for a simply additive dosage effect of the two genes AcR and AcS. The results are discussed with regard to other population studies and to recent findings concerning isoniazid inactivation and the activity of the involved enzymes in nonhuman primates. 相似文献
9.
Evidence for RNA-Oligonucleotides in Plant Vacuoles Isolated from Cultured Tomato Cells 总被引:5,自引:4,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)
We have shown that highly purified vacuoles of suspension-cultured tomato (Lycopersicon esculentum) cells contain RNA-oligonucleotides, using two different approaches to label and detect RNA: (a) in vivo labeling of cellular RNA with [5-3H]uridine, followed by preparation of vacuoles from protoplasts and by quantification of radioactively labeled material; and (b) in vitro labeling and analysis on sequencing gels of nucleic acids prepared from tomato vacuoles and their identification as RNA. The intravacuolar location of the RNA found in vacuolar preparations was concluded from analyzing for RNA intact organelles after repeated flotation steps as well as ribonuclease A treatment. About 3% of the RNA in protoplasts was localized within vacuoles, exceeding by severalfold the contribution made by contamination with unlysed protoplasts and subcellular organelles. Investigation of the size distribution of vacuolar RNA revealed an oligonucleotide pattern strikingly different from that which would arise from contaminating protoplasts; vacuolar RNA fragments are considerably shorter than 80 nucleotides. Characterization of these oligoribonucleotides (3′-phosphorylated termini; relatively rich in pyrimidines) as possible products of tomato vacuolar ribonuclease I action, and, in addition, enzymatic hydrolysis of vacuolar RNA by inherent enzyme activities in lysed vacuole preparations support the hypothesis that plant vacuoles are involved in cellular nucleolytic processes. 相似文献
10.
The binding of t-[35S]butylbicyclophosphorothionate [( 35S]TBPS) to a site on the GABAA receptor complex is ion dependent. This study was conducted to determine the effects of ion species and concentration on the time course, affinity, and number of sites of [35S]TBPS binding. At a concentration of 200 mM ion, the time to equilibrium for [35S]TBPS binding was shortest for I-, followed by Br- less than Cl- less than F-. A similar rank order was observed for the concentration of ion required to produce half-maximal [35S]TBPS binding. Saturation binding experiments were conducted to evaluate the effect of increasing ion concentration on the KD and Bmax of [35S]TBPS binding. The Bmax was independent of both ion species and concentration. The receptor affinity, however, increased with increasing concentration for each ion. Calculated maximal affinity values were not different between ions; however, the EC50 to produce those values was different among ions and ranked in the same order as that for time course and maximal binding data. Association and dissociation rates for [35S]TBPS binding were greater in I- than in Cl-. These data emphasize the importance of ion selection and incubation times on [35S]TBPS binding. 相似文献