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201.
Jrg Hhfeld Thomas Benzing Wilhelm Bloch Dieter O Fürst Sebastian Gehlert Michael Hesse Bernd Hoffmann Thorsten Hoppe Pitter F Huesgen Maja Khn Waldemar Kolanus Rudolf Merkel Carien M Niessen Wojciech Pokrzywa Markus M Rinschen Dagmar Wachten Bettina Warscheid 《EMBO reports》2021,22(8)
Cell survival, tissue integrity and organismal health depend on the ability to maintain functional protein networks even under conditions that threaten protein integrity. Protection against such stress conditions involves the adaptation of folding and degradation machineries, which help to preserve the protein network by facilitating the refolding or disposal of damaged proteins. In multicellular organisms, cells are permanently exposed to stress resulting from mechanical forces. Yet, for long time mechanical stress was not recognized as a primary stressor that perturbs protein structure and threatens proteome integrity. The identification and characterization of protein folding and degradation systems, which handle force‐unfolded proteins, marks a turning point in this regard. It has become apparent that mechanical stress protection operates during cell differentiation, adhesion and migration and is essential for maintaining tissues such as skeletal muscle, heart and kidney as well as the immune system. Here, we provide an overview of recent advances in our understanding of mechanical stress protection. 相似文献
202.
Alan W. Schwartz J. Visscher C. G. Bakker J. Niessen 《Origins of life and evolution of the biosphere》1987,17(3-4):351-357
Activated derivatives of purine-containing deoxynucleoside- diphosphates spontaneously oligomerize to produce pyrophosphate-
linked oligodeoxynucleotide analogues. These analogues are of potential interest as models of primitive, polynucleotide precursors.
The efficiency of oligomerization (ImpdGpIm and ImpdApIm much greater than ImpdIpIm) appears to reflect a combination of stacking
forces and the specific geometric orientations of the stacked units. Under favorable conditions, chain lengths greater than
20 have been obtained for oligomers containing pdGp in the absence of a template. In the presence of a complementary template,
the activated derivatives of pdGp and pdAp oligomerize much more extensively. An acyclo-analogue of G has also been shown
to undergo template-directed oligomerization on poly(C). These observations suggest the possibility that primitive information
transfer might have evolved in much simpler systems and that this function was taken over by polynucleotides at a later stage
in evolution.
For the previous paper in this series see Schwartz and Orgel, 1985a. 相似文献
203.
Basolateral K channels in an insect epithelium. Channel density, conductance, and block by barium 下载免费PDF全文
K channels in the basolateral membrane of insect hindgut were studied using current fluctuation analysis and microelectrodes. Locust recta were mounted in Ussing-type chambers containing Cl-free saline and cyclic AMP (cAMP). A transepithelial K current was induced by raising serosal [K] under short-circuit conditions. Adding Ba to the mucosal (luminal) side under these conditions had no effect; however, serosal Ba reversibly inhibited the short-circuit current (Isc), increased transepithelial resistance (Rt), and added a Lorentzian component to power density spectra of the Isc. A nonlinear relationship between corner frequency and serosal [Ba] was observed, which suggests that the rate constant for Ba association with basolateral channels increased as [Ba] was elevated. Microelectrode experiments revealed that the basolateral membrane hyperpolarized when Ba was added: this change in membrane potential could explain the nonlinearity of the 2 pi fc vs. [Ba] relationship if external Ba sensed about three-quarters of the basolateral membrane field. Conventional microelectrodes were used to determine the correspondence between transepithelially measured current noise and basolateral membrane conductance fluctuations, and ion-sensitive microelectrodes were used to measure intracellular K activity (acK). From the relationship between the net electrochemical potential for K across the basolateral membrane and the single channel current calculated from noise analysis, we estimate that the conductance of basolateral K channels is approximately 60 pS, and that there are approximately 180 million channels per square centimeter of tissue area. 相似文献
204.
Restriction-map variation with the yellow-achaete-scute region in five populations of Drosophila melanogaster 总被引:9,自引:0,他引:9
It has been proposed that the degree of recombination for a genomic region
will affect the level of both nucleotide heterozygosity and the density of
transposable elements. Both features of genomic diversity have been
examined in a number of recent reports for regions undergoing relatively
normal levels of recombination in Drosophila melanogaster. In this study
the genomic variation associated with yellow-achaete- scute loci located at
the tip of the X chromosome is examined by six- cutter restriction mapping.
In this region, as usual for regions adjacent to telomeres, crossing-over
is dramatically reduced, and published studies of visible mutants indicate
extremely little restriction-map variation. Eight six-cutter restriction
endonucleases were used to locate sequence variation in 14- and 16.5-kb
regions in 109 lines sampled from North America, Africa, and Europe. The
overall level of heterozygosity is estimated as 0.29%. Nine large
insertions, all presumed to be transposable elements, were observed.
Base-pair heterozygosity appears to be reduced compared with regions having
normal levels of recombination. The estimated heterozygosity is much higher
than reported in earlier studies of restriction-map variation among visible
mutations in the complex. The incidence of large insertions is not elevated
compared with that in other regions of the genome. This suggests that
asymmetric synapsis and exchange is not an important mechanism for the
elimination of transposable elements.
相似文献
205.
Hans W. M. Niessen Taco W. Kuijpers Dirk Roos Arthur J. Verhoeven 《Cellular signalling》1991,3(6):625-633
We have used a continuous spectrofluorimetric method to analyse the role of cytosolic free Ca2+ ([Ca2+]i) in the lysosomal enzyme release from the azurophilic granules in human neutrophils stimulated with f-Met-Leu-Phe (fMLP) in the presence of cytochalasin B. Measurements were performed with the β-glucuronidase substrate 4-methylumbelliferyl-β-
-glucuronide. We found that the transient rise in [Ca2+]i induced by fMLP is a necessary signal to obtain to obtain maximal degranulation. When this Ca2+ transient is prevented by the Ca2+ chelator BAPTA, degranulation can still be induced by a stimulated Ca2+ influx, albeit to a lower extent. We also studied the degranulation process in the neutrophils of a patient with a generalized chemotactic defect. Release of β-glucuronidase from the patient's neutrophils could not be induced despite the occurrence of a normal Ca2+ response and normal degranulation of specific granules. We conclude that, besides an increase in [Ca2+]i], an additional signal is required for the fusion of azurophilic granules with the plasma membrane in human neutrophils. 相似文献
206.
Monika Hediger Markus Niessen Jutta Müller-Navia Rolf Nöthiger Andreas Dübendorfer 《Chromosoma》1998,107(4):267-271
In the housefly, male sex is determined by a dominant factor, M, located either on the Y, on the X, or on any of the five autosomes. M factors on autosome I and on fragments of the Y chromosome show incomplete expressivity, whereas M factors on the other autosomes are fully expressive. To test whether these differences might be caused by heterochromatin-dependent
position effects, we studied the distribution of heterochromatin on the mitotic chromosomes by C-banding and by fluorescence
in situ hybridization of DNA fragments amplified from microdissected mitotic chromosomes. Our results show a correlation between
the chromosomal position of M and the strength of its male-determining activity: weakly masculinizing M factors are exclusively located on chromosomes with extensive heterochromatic regions, i.e., on autosome I and on the Y chromosome.
The Y is known to contain at least two copies of the M factor, which ensures a strong masculinizing effect despite the heterochromatic environment. The heterochromatic regions
of the sex chromosomes consist of repetitive sequences that are unique to the X and the Y, whereas their euchromatic parts
contain sequences that are ubiquitously found in the euchromatin of all chromosomes of the complement.
Received: 20 February 1998; in revised form: 11 May 1998 / Accepted: 23 May 1998 相似文献
207.
208.
Overview of microbial biofilms 总被引:13,自引:0,他引:13
Dr JW Costerton 《Journal of industrial microbiology & biotechnology》1995,15(3):137-140
As the success of this two-issue special section of the Journal of Industrial Microbiology attests, the study of microbial biofilms is truly burgeoning as the uniqueness and the importance of this mode of growth is increasingly recognized. Because of its universality the biofilm concept impacts virtually all of the subdivisions of Microbiology (including Medical, Dental, Agricultural, Industrial and Environmental) and these two issues incorporate contributions from authors in all of these disciplines. Some time ago we reasoned that bacteria cannot possibly be aware (sic) of their precise location, in terms of this spectrum of anthrocentric subspecialties, and that their behavior must be dictated by a standard set of phenotypic responses to environmental conditions in what must seem to them (sic) to be a continuum of very similar aquatic ecosystems. In this overview I will, therefore, stress the common features of microbial biofilms that we should bear in mind as we use this simple universal concept to seek to understand bacterial behavior in literally hundreds of aquatic ecosystems traditionally studied by dozens of subspecies of microbiologists reared in sharply different scientific and academic conventions. 相似文献
209.
Toxigenic and non-toxigenic black aspergilli belonging to theAspergillus niger aggregate and toA. carbonarius were compared to each other and to strains of other species by DNA fingerprinting. AFLPs showed a clear separation ofA. niger andA. carbonarius. However, no clear correlation between the genetic similarity of the strains and the ability to produce ochratoxin A (OTA)
was detected. Based on AFLP, marker sequences were chosen for the construction of SCAR-PCR primers for the detection ofA. carbonarius. A similar approach was used forA. ochraceus, another fungus of concern regarding ochratoxin A contamination of coffee. Cluster analysis ofA. ochraceus isolates mainly from Brazilian coffee showed a very close genetic similarity. Three species specific primer pairs were developed
and one of these was used for the PCR and realtime PCR (RT-PCR) based detection of the mould in green coffee.A. ochraceus was specifically and rapidly detected and quantified in green coffee. A positive correlation between the amount of DNA and
OTA content was established. 相似文献
210.
Meischl C Buermans HP Hazes T Zuidwijk MJ Musters RJ Boer C van Lingen A Simonides WS Blankenstein MA Dupuy C Paulus WJ Hack CE Ris-Stalpers C Roos D Niessen HW 《American journal of physiology. Cell physiology》2008,294(5):C1227-C1233
Thyroid hormone acts on a wide range of tissues. In the cardiovascular system, thyroid hormone is an important regulator of cardiac function and cardiovascular hemodynamics. Although some early reports in the literature suggested an unknown extrathyroidal source of thyroid hormone, it is currently thought to be produced exclusively in the thyroid gland, a highly specialized organ with the sole function of generating, storing, and secreting thyroid hormone. Whereas most of the proteins necessary for thyroid hormone synthesis are thought to be expressed exclusively in the thyroid gland, we now have found evidence that all of these proteins, i.e., thyroglobulin, DUOX1, DUOX2, the sodium-iodide symporter, pendrin, thyroid peroxidase, and thyroid-stimulating hormone receptor, are also expressed in cardiomyocytes. Furthermore, we found thyroglobulin to be transiently upregulated in an in vitro model of ischemia. When performing these experiments in the presence of 125 I, we found that 125 I was integrated into thyroglobulin and that under ischemia-like conditions the radioactive signal in thyroglobulin was reduced. Concomitantly we observed an increase of intracellularly produced, 125 I-labeled thyroid hormone. In conclusion, our findings demonstrate for the first time that cardiomyocytes produce thyroid hormone in a manner adapted to the cell's environment. 相似文献