全文获取类型
收费全文 | 278篇 |
免费 | 18篇 |
出版年
2022年 | 2篇 |
2021年 | 8篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 5篇 |
2016年 | 10篇 |
2015年 | 16篇 |
2014年 | 10篇 |
2013年 | 10篇 |
2012年 | 6篇 |
2011年 | 9篇 |
2010年 | 8篇 |
2009年 | 9篇 |
2008年 | 8篇 |
2007年 | 7篇 |
2006年 | 6篇 |
2005年 | 4篇 |
2004年 | 9篇 |
2003年 | 4篇 |
2002年 | 5篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 10篇 |
1997年 | 9篇 |
1996年 | 9篇 |
1995年 | 5篇 |
1993年 | 4篇 |
1992年 | 11篇 |
1991年 | 6篇 |
1990年 | 10篇 |
1989年 | 8篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 13篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1971年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有296条查询结果,搜索用时 31 毫秒
1.
Richard B. Pouw Mieke C. Brouwer Judy Geissler Laurens V. van Herpen Sacha S. Zeerleder Walter A. Wuillemin Diana Wouters Taco W. Kuijpers 《PloS one》2016,11(3)
The major human complement regulator in blood, complement factor H (FH), has several closely related proteins, called FH-related (FHR) proteins. As all FHRs lack relevant complement regulatory activity, their physiological role is not well understood. FHR protein 3 (FHR-3) has been suggested to compete with FH for binding to Neisseria meningitidis, thereby affecting complement-mediated clearance. Clearly, the in vivo outcome of such competition greatly depends on the FH and FHR-3 concentrations. While FH levels have been established, accurate FHR-3 levels were never unequivocally reported to date. Moreover, CFHR3 gene copy numbers commonly vary, which may impact the FHR-3 concentration. Hence, we generated five anti-FHR-3 mAbs to specifically measure FHR-3 in human healthy donors of which we determined the gene copy number variation at the CFH/CFHR locus. Finally, we examined the acute-phase response characteristics of FHR-3 in a small sepsis cohort. We determined FHR-3 levels to have a mean of 19 nM and that under normal conditions the copy number of CFHR3 correlates to a very large extent with the FHR-3 serum levels. On average, FHR-3 was 132-fold lower compared to the FH concentration in the same serum samples and FHR-3 did not behave as a major acute phase response protein. 相似文献
2.
J. L. V. Broers Barbie M. Machiels Helma J. H. Kuijpers Frank Smedts Ronald van den Kieboom Yves Raymond Frans C. S. Ramaekers 《Histochemistry and cell biology》1997,107(6):505-517
A selection of normal human tissues was investigated for the presence of lamins B1, B2, and A-type lamins, using a panel
of antibodies specific for the individual lamin subtypes. By use of immunoprecipitation and two-dimensional immunoblotting
techniques we demonstrated that these antibodies do not cross-react with other lamin subtypes and that a range of different
phosphorylation isoforms is recognized by each antibody. The lamin B2 antibodies appeared to decorate the nuclear lamina in
all tissues examined, except hepatocytes, in which very little lamin B2 expression was observed. In contrast to previous studies,
which suggested the ubiquitous expression of lamin B1 in mammalian tissues, we show that lamin B1 is not as universally distributed
throughout normal human tissues as was to be expected from previous studies. Muscle and connective tissues are negative, while
in epithelial cells lamin B1 seemed to be preferentially detected in proliferating cells. These results correspond well with
those obtained for lamin B1 in chicken tissues. The expression of A-type lamins is most prominent in well-differentiated epithelial
cells. Relatively undifferentiated and proliferating cells in epithelia showed a clearly reduced expression of A-type lamins.
Furthermore, most cells of neuroendocrine origin as well as most hematopoietic cells were negative for A-type lamin antibodies.
Accepted: 4 February 1997 相似文献
3.
J H Heuijerjans F R Pieper F C Ramaekers L J Timmermans H Kuijpers H Bloemendal W J Van Venrooij 《Experimental cell research》1989,181(2):317-330
The human bladder carcinoma cell lines RT4 and T24 and the human breast adenocarcinoma cell line MCF-7 were found to be negative for vimentin when studied by means of immunofluorescence and immunoblotting. Northern blot analysis revealed that these cells lacked detectable levels of vimentin mRNA with the exception of T24, which contains trace amounts of vimentin mRNA compared to the RNA level in vimentin-containing HeLa cells. CAT assays performed on these cells showed that a hamster vimentin promoter is inactive in RT4 and MCF-7 cells. In the vimentin-lacking cells, the binding of polyribosomes, specific mRNAs, and translation factor eIF-2 alpha to the cytoskeletal fraction was examined. Our results indicate that the presence of a vimentin network is not crucial for the association of the translation machinery with the cytoskeleton. Furthermore, in these vimentin-negative cell lines the immunofluorescence staining pattern of eIF-2 alpha shows a fibro-granular structure that has no resemblance to the cytokeratin or actin cytoskeleton present in these cells. 相似文献
4.
Synthesis of well-defined phosphate-methylated DNA fragments: the application of potassium carbonate in methanol as deprotecting reagent. 总被引:4,自引:4,他引:0
下载免费PDF全文
![点击此处可从《Nucleic acids research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A new deprotection procedure in the synthesis of (partially) phosphate-methylated oligodeoxynucleotides has been developed, involving treatment of fully protected DNA fragments with methanolic potassium carbonate. It is shown that base deprotection can be accomplished in potassium carbonate/methanol without affecting the methyl phosphotriesters. This methodology enables us to synthesize, both in solution and on a solid support, DNA fragments which are phosphate-methylated at defined positions. The solid phase synthesis, however, turns out to be accompanied by considerable demethylation of the phosphotriesters. It is demonstrated that this demethylation does not occur during the deprotection or work-up procedure. Furthermore, it was found that the latter side-reaction is suppressed when the standard capping procedure with acetic anhydride is included. 相似文献
5.
6.
The elemental and water content of cultured bovine adrenal chromaffin cells and their secretory chromaffin granules have been measured and compared with isolated chromaffin granules using quick freezing, ultracryomicrotomy, and electron microprobe analysis methods. In units of millimole/kilogram dry weight (+/- S.E.) granules in situ contained: P, 523 +/- 32; K+, 124 +/- 9; S, 82 +/- 3; Cl-, 74 +/- 9; Ca2+, 13 +/- 2; Mg2+, 6 +/- 2; and Na+, -2 +/- 2. Following routine isolation in isotonic sucrose buffer, granule K and Cl- had decreased while granule Na+ increased. Cl- exhibited a consistent decrease to 35-40 mmol/kg dry weight. Granule Na+ and K+ concentrations ranged from 43 to 12 mmol/kg and 28 to 60 mmol/kg dry weight, respectively, depending on the Na+ and K+ content of the buffer. Despite the redistribution of monovalent ions, granule Ca2+, granule P, being in the form of ATP, and granule S, being in the form of protein, were not significantly changed. The stability of these elements is consistent with the existence of a stable storage complex for Ca2+, ATP, and protein. Using the granule as an internal standard with a water content of 66%, the water contents of external space, nucleus, cytoplasm, and mitochondria were estimated to be 89, 88, 82, and 70%, respectively. Wet weight concentrations for each element were calculated for granules and cytoplasm from which the transgranular concentration gradients for K+, Cl-, and Na+ were determined. Cl-, a permeant anion, was 2-fold higher in the granule than in the cytoplasm while K+, a slightly permeant cation, had an opposite distribution ratio slightly less than two. Together, the K+ and Cl- data suggest the presence of an inside-positive granule membrane potential of approximately 10-16 mV. The surprising lack of Na+ from the granule matrix suggests a hugh inward gradient for Na+ even though the Na+ content of chromaffin cell cytoplasm is low at 5 mmol/kg water. The lack of an outward Na+ gradient is important in that it indicates that the previously described electroneutral Na+-Ca2+ exchange system, by which isolated granules accumulate Ca2+, does not operate in mature granules in situ. Consequently, if chromaffin granules regulate internal calcium during stimulus secretion coupling, a mechanism other that Na+-Ca2+ exchange is necessary. 相似文献
7.
Ouabain increases the enzyme secretion from the isolated rabbit pancreas and pancreatic fragments, but not from isolated pancreatic acini. The increase occurs after a delay of 45-60 min and is not accompanied by an increase in lactate dehydrogenase release. The stimulatory effect of ouabain (10(-5) M) is dependent on the presence of extracellular calcium, and is not antagonized by 10(-4) M atropin, 10(-4) M propranolol, 10(-5) M phentolamine, 10(-3) M dibutyryl-cyclic GMP, 10(-6) M tetrodotoxin, 10(-4) M verapamil or 10(-4) M D-600. Elevation of the extracellular potassium concentration to 120 mM in the presence of 10(-4) M atropin also increases the enzyme secretion from rabbit pancreatic fragments. The increase is again dependent on the presence of extracellular calcium and is resistant to adrenergic blockade and to tetrodotoxin, verapamil or D-600. Forskolin also stimulates a Ca2+-dependent release of amylase from pancreatic fragments but not from pancreatic acini. In the presence of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IMX), ouabain (10(-5) M) and K+ (120 mM) cause an immediate increase in the cyclic AMP content of pancreatic fragments which does not occur in the absence of extracellular calcium. In pancreatic acini, the cAMP production is only slightly increased by ouabain. In the absence of IMX, the cAMP levels in fragments or acini are not detectably altered by ouabain or K+. The results suggest that the stimulation of enzyme secretion by ouabain and high K+ is an indirect effect, mediated by the release of an endogenous transmitter from non-cholinergic, non-adrenergic nerves in the intact preparations. The release and/or the effect of the transmitter appears to be mediated primarily by Ca2+ and secondarily by cyclic AMP. 相似文献
8.
H. E. van de Baan L. A. M. Kuijpers W. P. J. Overmeer F. J. Oppenoorth 《Experimental & applied acarology》1985,1(1):3-10
The cause of parathion and propoxur resistance inTyphlodromus pyri was studied in a Dutch strain in which resistance was dependent on a semi-dominant gene. Activity of glutathione S-transferase and acetylcholinesterase and reaction rate of acetylcholinesterase with paraoxon and propoxur were measured in this resistant (R) and in a susceptible (S) strain. The R strain was 100-fold resistant to parathion and 2300-fold resistant to propoxur. A 36-fold reduction was found in rate of inhibition of acetylcholinesterase in the R strain for paraoxon, and a 14-fold reduction for propoxur. In combination with the monogenic nature of the resistance, this proves that the insensitivity of acetylcholinesterase is the cause of resistance. The rate constant of acetylcholinesterase inhibition at 25°C in the S and R strains was 1.5×105 and 4.2×103
M
–1 min–1 respectively for paraoxon, and 5.1×104 and 3.6×103
M
–1 min–1 for propoxur. There was no significant difference between the R and S strains in glutathione S-transferase activity. The R strain had a somewhat lower acetylcholinesterase activity than the S strain. 相似文献
9.
A comparative description of mitochondrial DNA differentiation in selected avian and other vertebrate genera 总被引:14,自引:1,他引:13
Levels of mitochondrial DNA (mtDNA) sequence divergence between species
within each of several avian (Anas, Aythya, Dendroica, Melospiza, and
Zonotrichia) and nonavian (Lepomis and Hyla) vertebrate genera were
compared. An analysis of digestion profiles generated by 13-18 restriction
endonucleases indicates little overlap in magnitude of mtDNA divergence for
the avian versus nonavian taxa examined. In 55 interspecific comparisons
among the avian congeners, the fraction of identical fragment lengths (F)
ranged from 0.26 to 0.96 (F = 0.46), and, given certain assumptions, these
translate into estimates of nucleotide sequence divergence (p) ranging from
0.007 to 0.088; in 46 comparisons among the fish and amphibian congeners, F
values ranged from 0.00 to 0.36 (F = 0.09), yielding estimates of P greater
than 0.070. The small mtDNA distances among avian congeners are associated
with protein-electrophoretic distances (D values) less than approximately
0.2, while the mtDNA distances among assayed fish and amphibian congeners
are associated with D values usually greater than 0.4. Since the
conservative pattern of protein differentiation previously reported for
many avian versus nonavian taxa now appears to be paralleled by a
conservative pattern of mtDNA divergence, it seems increasingly likely that
many avian species have shared more recent common ancestors than have their
nonavian taxonomic counterparts. However, estimates of avian divergence
times derived from mtDNA- and protein-calibrated clocks cannot readily be
reconciled with some published dates based on limited fossil remains. If
the earlier paleontological interpretations are valid, then protein and
mtDNA evolution must be somewhat decelerated in birds. The empirical and
conceptual issues raised by these findings are highly analogous to those in
the long-standing debate about rates of molecular evolution and times of
separation of ancestral hominids from African apes.
相似文献
10.
Methods for computing the standard errors of branching points in an evolutionary tree and their application to molecular data from humans and apes 总被引:23,自引:2,他引:21
Statistical methods for computing the standard errors of the branching
points of an evolutionary tree are developed. These methods are for the
unweighted pair-group method-determined (UPGMA) trees reconstructed from
molecular data such as amino acid sequences, nucleotide sequences,
restriction-sites data, and electrophoretic distances. They were applied to
data for the human, chimpanzee, gorilla, orangutan, and gibbon species.
Among the four different sets of data used, DNA sequences for an
895-nucleotide segment of mitochondrial DNA (Brown et al. 1982) gave the
most reliable tree, whereas electrophoretic data (Bruce and Ayala 1979)
gave the least reliable one. The DNA sequence data suggested that the
chimpanzee is the closest and that the gorilla is the next closest to the
human species. The orangutan and gibbon are more distantly related to man
than is the gorilla. This topology of the tree is in agreement with that
for the tree obtained from chromosomal studies and DNA-hybridization
experiments. However, the difference between the branching point for the
human and the chimpanzee species and that for the gorilla species and the
human-chimpanzee group is not statistically significant. In addition to
this analysis, various factors that affect the accuracy of an estimated
tree are discussed.
相似文献