全文获取类型
收费全文 | 1417篇 |
免费 | 219篇 |
出版年
2022年 | 14篇 |
2021年 | 24篇 |
2017年 | 12篇 |
2016年 | 22篇 |
2015年 | 43篇 |
2014年 | 41篇 |
2013年 | 45篇 |
2012年 | 70篇 |
2011年 | 68篇 |
2010年 | 41篇 |
2009年 | 45篇 |
2008年 | 42篇 |
2007年 | 55篇 |
2006年 | 68篇 |
2005年 | 46篇 |
2004年 | 55篇 |
2003年 | 55篇 |
2002年 | 42篇 |
2001年 | 37篇 |
2000年 | 49篇 |
1999年 | 32篇 |
1998年 | 27篇 |
1997年 | 14篇 |
1996年 | 15篇 |
1994年 | 15篇 |
1993年 | 11篇 |
1992年 | 34篇 |
1991年 | 33篇 |
1990年 | 21篇 |
1989年 | 22篇 |
1988年 | 26篇 |
1987年 | 29篇 |
1986年 | 28篇 |
1985年 | 29篇 |
1984年 | 19篇 |
1983年 | 21篇 |
1982年 | 18篇 |
1981年 | 20篇 |
1980年 | 15篇 |
1979年 | 32篇 |
1978年 | 12篇 |
1977年 | 14篇 |
1976年 | 13篇 |
1975年 | 15篇 |
1974年 | 19篇 |
1973年 | 34篇 |
1972年 | 24篇 |
1970年 | 16篇 |
1969年 | 11篇 |
1968年 | 15篇 |
排序方式: 共有1636条查询结果,搜索用时 15 毫秒
61.
Analysis of the polypeptides induced by 29 herpes simplex virus type 1/type 2 intertypic recombinants and correlation of the data with the crossover points in the recombinant DNAs have enabled the map positions of many polypeptides to be deduced. These include 25 polypeptides which label with [35S]methionine, 11 which label with [32P]orthophosphate, and 4 which label with [14C]glucosamine. Together with the data of Preston et al. (J. Virol., in press) on the mapping of five immediate-early polypeptides, the results show that representatives of four groups of proteins--immediate-early, late, phosphorylated, and glycosylated--map in both long and short regions. The functional organization of the herpes simplex virus genome does not therefore restrict any of these four groups to either the long or the short region. 相似文献
62.
Axonal transport has been extensively studied for a period of 20–30 years, but there is still no general consensus concerning the mechanism by which this transport process operates. An important development in this regard is the recent studies in the physical biochemistry group in the Department of Biochemistry at Monash University where it has been demonstrated that ordered flows may be generated spontaneously in polymer systems under non-equilibeium conditions. The new phenomenon exhibits many novel features, particularly with respect to polymer transport, which bear marked similarity to the behaviour of components in axonal transport. This article sets out to essentiallybring to the attention of those in the neurosciences some of the properties of ordered structured flows in polymer solutions. These properties may generate a different view in the understanding of the mechanism of axonal transport. 相似文献
63.
S Uchida H M Kwon A S Preston J S Handler 《The Journal of biological chemistry》1991,266(15):9605-9609
Expression of a Madin-Darby canine kidney (MDCK) cell taurine transporter was examined in Xenopus oocytes that had been injected with poly(A)+ RNA extracted from MDCK cells. Compared with water-injected oocytes, injection of total poly(A)+ RNA resulted in an increase in Na(+)-dependent taurine uptake which was directly related to the amount of RNA injected. The magnitude of expression in poly(A)+ RNA-injected oocytes was 5-10-fold higher than that of water-injected oocytes. Since the Vmax of taurine uptake in MDCK cells is increased by culture in hypertonic medium, we compared oocyte taurine uptake after injection with poly(A)+ RNA from MDCK cells cultured in hypertonic medium with uptake in oocytes injected with poly(A)+ RNA from hypertonic cells elicited twice the taurine uptake elicited by poly(A)+ RNA from isotonic cells. The transporter expressed in oocytes was like that in MDCK cells: it was completely dependent on external sodium and was also anion dependent (Cl- greater than or equal to Br- greater than SCN- much greater than gluconate-). Other beta-amino acids, beta-alanine and hypotaurine, inhibited taurine uptake, but L-alanine and 2-(methylamino) isobutyric acid did not. The apparent Km of the transporter was 7.0 microM. After size fractionation on a sucrose density gradient, poly(A)+ RNA encoding for the MDCK taurine transporter was found in the fraction whose average size was 4.4 kilobases. 相似文献
64.
Differential depolymerization mechanisms of pectate lyases secreted by Erwinia chrysanthemi EC16.
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 four pectate lyases (EC 4.2.2.2) secreted by Erwinia chrysanthemi EC16 have been individually produced as recombinant enzymes in Escherichia coli. Oligogalacturonates formed from polygalacturonic acid during reactions catalyzed by each enzyme have been determined by high-performance liquid chromatography analysis. PLa catalyzes the formation of a series of oligomers ranging from dimer to dodecamer through a random endolytic depolarization mechanism. PLb and PLc are trimer- and tetramer-generating enzymes with an identical combination of endolytic and exolytic mechanisms. PLe catalyzes a nonrandom endolytic depolymerization with the formation of dimer as the predominant product. The pectate lyases secreted by E. chrysanthemi EC16 represent a battery of enzymes with three distinct approaches to the depolymerization of plant cell walls. 相似文献
65.
Calcium-dependent inactivation of the calcium current activated upon hyperpolarization of Paramecium tetraurelia
下载免费PDF全文
![点击此处可从《The Journal of general physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The Ca2+ current activated upon hyperpolarization of Paramecium tetraurelia decays over a period of 150-200 ms during sustained steps under voltage clamp. At membrane potentials between -70 and approximately -100 mV, the time course of this inactivation is described by a single exponential function. Steps negative to approximately -100 mV elicit currents that decay biexponentially, however. Three lines of evidence suggest that this current's inactivation is a function of intracellular Ca2+ concentration rather than membrane potential: (a) Comparing currents with similar amplitudes but elicited at widely differing membrane potentials suggests that their time course of decay is a sole function of inward current magnitude. (b) The extent of current inactivation is correlated with the amount of Ca2+ entering the cell during hyperpolarization. (c) The onset and time course of recovery from inactivation can be hastened significantly by injecting cells with EGTA. We suggest that the decay of this current during hyperpolarization involves a Ca(2+)-dependent pathway. 相似文献
66.
Development and application of new positively charged filters for recovery of bacteriophages from water. 总被引:1,自引:1,他引:0
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
J J Borrego R Cornax D R Preston S R Farrah B McElhaney G Bitton 《Applied microbiology》1991,57(4):1218-1222
Electronegative and electropositive filters were compared for the recovery of indigenous bacteriophages from water samples, using the VIRADEL technique. Fiber glass and diatomaceous earth filters displayed low adsorption and recovery, but an important increase of the adsorption percentage was observed when the filters were treated with cationic polymers (about 99% adsorption). A new methodology of virus elution was developed in this study, consisting of the slow passage of the eluent through the filter, thus increasing the contact time between eluent and virus adsorbed on the filters. The use of this technique allows a maximum recovery of 71.2% compared with 46.7% phage recovery obtained by the standard elution procedure. High percentages (over 83%) of phage adsorption were obtained with different filters from 1-liter aliquots of the samples, except for Virosorb 1-MDS filters (between 1.6 and 32% phage adsorption). Phage recovery by using the slow passing of the eluent depended on the filter type, with recovery ranging between 1.6% for Virosorb 1-MDS filters treated with polyethyleneimine and 103.2% for diatomaceous earth filters treated with 0.1% Nalco. 相似文献
67.
Enhanced Mutability Associated with a Temperature-Sensitive Mutant of Vesicular Stomatitis Virus 总被引:5,自引:4,他引:1
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
C. R. Pringle V. Devine M. Wilkie C. M. Preston A. Dolan D. J. McGeoch 《Journal of virology》1981,39(2):377-389
Temperature-sensitive (ts) mutant tsD1 of vesicular stomatitis virus, New Jersey serotype, is the sole representative of complementation group D. Clones derived from this mutant exhibited three different phenotypes with respect to electrophoretic mobility of the G and N polypeptides of the virion in sodium dodecyl sulfate-polyacrylamide gel. Analysis of non-ts pseudorevertants showed that none of the three phenotypes was associated with the temperature sensitivity of mutant tsD1. Additional phenotypes, some also involving the NS polypeptide, appeared during sequential cloning, indicating that mutations were generated at high frequency during replication of tsD1. Furthermore, mutations altering the electrophoretic mobility of the G, N, NS, and M polypeptides were induced in heterologous viruses multiplying in the same cells as tsD1. These heterologous viruses included another complementing ts mutant of vesicular stomatitis virus New Jersey and ts mutants of vesicular stomatitis virus Indiana and Chandipura virus. Complete or incomplete virions of tsD1 appeared to be equally efficient inducers of mutations in heterologous viruses. Analysis of the progeny of a mixed infection of two complementing ts mutants of vesicular stomatitis virus New Jersey with electrophoretically distinguishable G, N, NS, and M proteins yielded no recombinants and excluded recombination as a factor in the generation of the electrophoretic mobility variants. In vitro translation of total cytoplasmic RNA from BHK cells indicated that post-translational processing was not responsible for the aberrant electrophoretic mobility of the N, NS, and M protein mutants. Aberrant glycosylation could account for three of four G protein mutants, however. Some clones of tsD1 had an N polypeptide which migrated faster in sodium dodecyl sulfate-polyacrylamide gel than did the wild type, suggesting that the polypeptide might be shorter by about 10 amino acids. Determination of the nucleotide sequence to about 200 residues from each terminus of the N gene of one of these clones, a revertant, and the wild-type parent revealed no changes compatible with synthesis of a shorter polypeptide by premature termination or late initiation of translation. The sequence data indicated, however, that the N-protein mutant and its revertant differed from the parental wild type in two of the 399 nucleotides determined. These sequencing results and the phenomenon of enhanced mutability associated with mutant tsD1 reveal that rapid and extensive evolution of the viral genome can occur during the course of normal cytolytic infection of cultured cells. 相似文献
68.
Recognition of AeE Ia antigens at the functional level was investigated using T-cell clones. The reactivities of an alloreactive and an antigen-reactive clone, both of which recognized AeE Ia molecules, were compared on a panel of stimulator/antigen-presenting cells of various genotypes. The two clones recognized all tested A
e
b
E
x
Ia molecules, where x is a haplotype capable of expressing an Ia.7-bearing E polypeptide. Ia antigen recognition by either clone could be inhibited by the monoclonal antibody Y-17, which recognizes a combinatorial serologic determinant on certain AeE molecules. There were no differences in the recognition of Ia by the alloreactive versus the antigen-reactive clone, suggesting that Ia antigens are recognized by the two clones in a fundamentally similar way. The recognition of these various Ia molecules by the two cloned T-cell lines provides evidence that the E polypeptides from H-2 haplotypes k, d, r, and u are functionally indistinguishable.Abreviations
MHC
major histocompatibility complex
-
Mb
myoglobin
-
MLR
mixed leukocyte reaction
-
PBS
phosphate buffered saline
-
APC
antigen presenting cell
-
KLH
keyhole limpet hemocyanin
-
GAT
poly (glut60 alai30 tyr10)n
- (TG)-A—L
poly (L-tyr, L-glu)-poly (D, L-ala)—poly L-lys
-
GLPhe
poly (glu55 lys36 phe9)n 相似文献
69.
70.
Cell-substrate interactions between human blood neutrophils moving on a glass substrate in serum-free medium have been investigated using reflexion interference microscopy, high voltage and scanning electron microscopy (SEM). The contact pattern with the substrate differed considerably from that found in fibroblasts and the amoeba Naegleria. Discrete focal contacts could not be detected but large broad areas of very close contact (accounting for about 30% of the total contact area) could be found particularly associated with the uroid. Considerable loss of membrane material occurred as a result of breakdown of the uroid during locomotion. 相似文献