全文获取类型
收费全文 | 495篇 |
免费 | 47篇 |
出版年
2023年 | 3篇 |
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 6篇 |
2019年 | 11篇 |
2018年 | 9篇 |
2017年 | 3篇 |
2016年 | 11篇 |
2015年 | 15篇 |
2014年 | 21篇 |
2013年 | 38篇 |
2012年 | 37篇 |
2011年 | 45篇 |
2010年 | 18篇 |
2009年 | 15篇 |
2008年 | 28篇 |
2007年 | 30篇 |
2006年 | 25篇 |
2005年 | 22篇 |
2004年 | 21篇 |
2003年 | 15篇 |
2002年 | 18篇 |
2001年 | 12篇 |
2000年 | 15篇 |
1999年 | 10篇 |
1998年 | 6篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 9篇 |
1989年 | 4篇 |
1988年 | 12篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1982年 | 2篇 |
1980年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1970年 | 4篇 |
1960年 | 2篇 |
1958年 | 2篇 |
1955年 | 1篇 |
1927年 | 1篇 |
1897年 | 1篇 |
排序方式: 共有542条查询结果,搜索用时 15 毫秒
1.
2.
This study used monoclonal antibodies to sheep MHC class II molecules as well as an L cell transfectant (T8.1) which expresses DRA and DRB genes to show that two distinct DRβ chains are expressed in the sheep. Two anti-β chain specific monoclonal antibodies VPM37 and VPM43 react with DR antigen but not DQ antigen by ELISA. These two antibodies do not react with the DRβ chain expressed in the T8.1 cell line. Two-dimensional immunoblotting shows that these antibodies recognize a subgroup of the spots recognized by the DR-specific monoclonal antibody VPM57 which does react with the T8.1 β chain. Amino-terminal sequence analysis of the α chain associated with VPM37β chain shows that this α chain is homologous to the human DRα chain strongly indicating that the β chain is DR-like. VPM37 and VPM43 are shown to be directed against different epitopes on sheep MHC class II molecules so it is highly unlikely that the data can be explained by the presence of posttranslational modifications or the existence of a very common allele. These data provide clear evidence for the expression of two distinct DRP chains in the sheep. 相似文献
3.
4.
DNA hybridization assay for detection of gypsy moth nuclear polyhedrosis virus in infected gypsy moth (Lymantria dispar L.) larvae.
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)
Radiolabeled Lymantria dispar nuclear polyhedrosis virus DNA probes were used in a DNA hybridization assay to detect the presence of viral DNA in extracts from infected larvae. Total DNA was extracted from larvae, bound to nitrocellulose filters, and assayed for the presence of viral DNA by two methods: slot-blot vacuum filtration and whole-larval squashes. To test the assays, neonate larvae were fed droplets containing a known concentration of L. dispar nuclear polyhedrosis virus and observed for up to 10 days to determine the percentage of infected larvae. The average percent mortalities were 88.0, 60.7, 26.0, and 5.3% for larvae fed droplets containing 4.0 x 10(4), 1.0 x 10(4), 2.5 x 10(3), and 6.25 x 10(2) polyhedral inclusion bodies (PIBs) per ml, respectively. Other larvae treated with the same virus concentrations were frozen at 2, 4, and 6 days postinoculation and examined by the hybridization techniques. The average percentage of slot blots containing viral DNA equaled 81.0, 58.0, 18.0, and 6.0% for larvae blotted 4 days after treatment with 4.0 x 10(4), 1.0 x 10(4), 2.5 x 10(3), and 6.25 x 10(2) PIBs per ml, respectively, and 89.9, 52.1, 26.6, and 6.0%, respectively at 6 days postinoculation. Thus, the hybridization results were closely correlated with mortality observed in reared larvae. Hybridization of squashes of larvae frozen 4 days after receiving the above virus treatments also produced accurate measures of the incidence of virus infection. 相似文献
5.
As we have seen, natural antibodies first emerged as an experimental phenomenon without a plausible theoretical explanation. They were originally denied the status of antibody; then, adjustments to the side-chain theory transformed them from a curiosity into a foundation of the theory. However, in accommodating natural antibodies, Ehrlich had opened several holes in his mechanism of antibody formation.Thus, by 1905, natural antibodies were clearly established as problematic. From the practical standpoint, it seemed unwise to maintain an identity between normal and immune antibodies, given the therapeutic differences in their avidity. With the decline of Ehrlich's theory of antibody formation and the spread of Landsteiner's hapten technique for the production of antibodies against artificial antigens after World War I, the theoretical possibility of their existence as other than anomaly seemed more remote than ever. However, outside the theory and despite clinical considerations, natural antibodies remained a perplexing experimental phenomenon.49 相似文献
6.
Evidence from morphology and anatomy (including embryology), as well as from palynology, chemistry and cytology, indicates
thatHydrastis is quite divergent from Ranunculaceae (in which the genus has been most often included) as well as from both Glaucidiaceae
and Berberidaceae. Distinctive features ofHydrastis, which demarcate it from Ranunculaceae but which are sometimes shared by Berberidaceae, are: the unique mode of origin of
the vascular supply to stamens and carpels; the micropyle being formed by both integuments; the xylem not V-shaped in cross
section; scalariform vessel perforations present; haploid chromosome number 13; pollen tectum consisting of a compound layer
of striae; leaf mesophyll not differentiated; the unique course of stem medullary bundles; D-galactose present. Its distinctive
higher haploid chromosome number, as well as its many less-specialized character states (in floral structure, leaf anatomy,
and xylem and vessel morphology), suggest thatHydrastis is a relictual primitive group which diverged early from a common ancestral stock of Ranunculaceae, Berberidaceae and probably
of Circaeasteraceae; at least some of the features shared byHydrastis and one or another of the families concerned seem to be a heritage from their common ancestor. We propose a reestablishment
of a monotypic family, Hydrastidaceae. 相似文献
7.
8.
We have broadly defined the DNA regions regulating esterase6 activity in
several life stages and tissue types of D. melanogaster using P-
element-mediated transformation of constructs that contain the esterase6
coding region and deletions or substitutions in 5' or 3' flanking DNA.
Hemolymph is a conserved ancestral site of EST6 activity in Drosophila and
the primary sequences regulating its activity lie between -171 and -25 bp
relative to the translation initiation site: deletion of these sequences
decrease activity approximately 20-fold. Hemolymph activity is also
modulated by four other DNA regions, three of which lie 5' and one of which
lies 3' of the coding region. Of these, two have positive and two have
negative effects, each of approximately twofold. Esterase6 activity is
present also in two male reproductive tract tissues; the ejaculatory bulb,
which is another ancestral activity site, and the ejaculatory duct, which
is a recently acquired site within the melanogaster species subgroup.
Activities in these tissues are at least in part independently regulated:
activity in the ejaculatory bulb is conferred by sequences between -273 and
-172 bp (threefold decrease when deleted), while activity in the
ejaculatory duct is conferred by more distal sequences between -844 and
-614 bp (fourfold decrease when deleted). The reproductive tract activity
is further modulated by two additional DNA regions, one in 5' DNA (-613 to
-284 bp; threefold decrease when deleted) and the other in 3' DNA (+1860 to
+2731 bp; threefold decrease when deleted) that probably overlaps the
adjacent esteraseP gene. Collating these data with previous studies
suggests that expression of EST6 in the ancestral sites is mainly regulated
by conserved proximal sequences while more variable distal sequences
regulate expression in the acquired ejaculatory duct site.
相似文献
9.
J. Keating L. Dratcu M. Lader R.A. Sherwood 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1993,615(2)
A reversed-phase high-performance liquid chromatographic method is described for the measurement of plasma serotonin concentrations. Sample preparation is by a simple solid-phase extraction using C18 columns. An isocratic separation is used with electrochemical detection. The application of the method to the measurement of plasma serotonin concentrations following the administration of fluvoxamine (a serotonin re-uptake inhibitor), maprotiline (a noradrenaline re-uptake inhibitor) and placebo to normal subjects for a seven-day period is reported. Fluvoxamine significantly decreases plasma serotonin over this time period in a linear fashion. No effect on plasma serotonin was seen for maprotiline or placebo. Plasma serotonin concentrations can be used to monitor compliance with fluvoxamine therapy. 相似文献
10.
C Möller G Weber MM Dreyfuss 《Journal of industrial microbiology & biotechnology》1996,17(5-6):359-372
Intraspecific variation among 84 isolates of the anamorphic fungusChaunopycnis alba from 26 different geographical locations was analyzed by investigating optimal growth temperatures, differences in the production of secondary metabolites and presence or absence of the cyclosporin synthetase gene. The genetic diversity was assessed using random amplified polymorphic DNA (RAPD). Analysis of these data showed high genetic, metabolic and physiological diversity within this species. Isolates from the Antarctic represented the most homogeneous group withinC. alba and together with isolates from the Arctic these polar strains differed from alpine, temperate and tropical strains by low optimal growth temperatures and by low production of secondary metabolites. Isolates from tropical climes were characterized by high optimal growth temperatures and by the production of comparatively diverse metabolite spectra. Most of the isolates that were similar in the combination of their physiological and metabolic characters were also genetically related. Isolates from different geographical origins did not show many similarities, with the exception of the cyclosporin A-producing isolates, and large diversity could be observed even within a single habitat. This leads us to the suggestion that for pharmaceutical screening programs samples should be collected from a diversity of different geographical and climatic locations. For the selection of strains for screening the RAPD assay seems to be the most powerful tool. It reflected the highest intraspecific diversity and the results corresponded well with the other characteristics. 相似文献