全文获取类型
收费全文 | 390篇 |
免费 | 19篇 |
出版年
2022年 | 3篇 |
2021年 | 6篇 |
2020年 | 3篇 |
2019年 | 7篇 |
2018年 | 8篇 |
2016年 | 7篇 |
2015年 | 16篇 |
2014年 | 20篇 |
2013年 | 17篇 |
2012年 | 37篇 |
2011年 | 27篇 |
2010年 | 14篇 |
2009年 | 16篇 |
2008年 | 19篇 |
2007年 | 19篇 |
2006年 | 21篇 |
2005年 | 13篇 |
2004年 | 20篇 |
2003年 | 8篇 |
2002年 | 11篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1998年 | 5篇 |
1997年 | 8篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1992年 | 3篇 |
1990年 | 3篇 |
1988年 | 6篇 |
1981年 | 4篇 |
1979年 | 4篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1975年 | 7篇 |
1973年 | 2篇 |
1966年 | 2篇 |
1958年 | 2篇 |
1942年 | 2篇 |
1938年 | 2篇 |
1936年 | 2篇 |
1935年 | 2篇 |
1934年 | 3篇 |
1933年 | 3篇 |
1924年 | 1篇 |
1916年 | 1篇 |
1914年 | 1篇 |
1910年 | 1篇 |
1907年 | 2篇 |
1906年 | 2篇 |
排序方式: 共有409条查询结果,搜索用时 57 毫秒
1.
Summary Genomic clones encoding two Volvox -tubulin genes have been isolated and shown to represent the only two -tubulin genes in the genome. Restriction fragment length polymorphism analysis was used to demonstrate that the two genes are genetically linked. One of these genes was sequenced and the mRNA start site(s) determined by primer extension. A comparison of its sequence to those of the two -tubulin genes of Chlamydomonas revealed: (1) a high degree of conservation of the coding region, with the predicted amino acid sequence differing only in the C-terminal residue; (2) extensive sequence conservation in the 5 untranslated leader region and a 16 bp (putative regulatory) sequence in the promoter region; (3) the same number and location of introns, with a short region of homology in intron 1, but little significant homology in introns 2 and 3. 相似文献
2.
3.
Zusammenfassung Werden Keimlinge vonHelianthus annuus undVicia faba mittels einer Wasserstrahlpumpe mit Wasser infiltriert, so führt dies sofort in allen Organen der Pflanze zu einer sehr starken und mitunter völligen Hemmung des Wachstums. Wirkt der Unterdruck in Luft ein, so daß es hernach zu keiner Wasserfüllung der Interzellularen kommt, so unterbleibt jede Wachstumshemmung.Die Frage nach der Kausalbeziehung zwischen Infiltration und Wachstumshemmung konnte nicht geklärt werden, da die nächstiliegende Annahme, Infiltration führe zu einer Atmungshemmung, durch das Experiment nicht bestätigt werden konnte.Es wird darauf hingewiesen, daß die Zufuhr von Wirk- oder Nährstoffen durch Infiltration eine Methode ist, die in wachsenden Organen nur mit großem Vorbehalt angewendet werden darf, da eine im Wachstum weitgehend gehemmte Pflanze sich in einem anomalen Zustand befindet.Mit 8 Textabbildungen. 相似文献
4.
Margarete Traiser Bernd Diener Dietmar Utesch Franz Oesch 《In vitro cellular & developmental biology. Animal》1995,31(4):266-273
Summary In primary monocultures of adult rat liver parenchymal cells (PC), the activities of the xenobiotic metabolizing enzymes microsomal
epoxide hydrolase (mEHb), soluble epoxide hydrolase (sEH), glutathione S-transferases (GST), and phenolsulfotransferase (ST) were reduced after 7
d to values below 33% of the initial activities. Furthermore, the gap junctional intercellular communication (GJIC), measured
after microinjection by dye transfer, decreased from 90% on Day 1 to undetectable values after 5 d in monoculture. Co-culture
of PC with nonparenchymal rat liver epithelial cells (NEC) increased (98% on Day 1) and stabilized (82% on Day 7) the homotypic
GJIC of PC. Additionally, most of the measured xenobiotic metabolizing enzyme activities were well stabilized over 1 wk in
co-culture. Because GJIC is one of several mechanisms playing an important role in cell differentiation, the importance of
GJIC for the stabilization of xenobiotic metabolizing enzymes in PC was investigated. PC in monoculture were, therefore, treated
with 2% dimethyl sulfoxide (DMSO), a differentiation promoting factor, and 1,1,1-trichloro-2,2,-bis (p-chlorophenyl) ethane
(DDT) (10 μg/ml), a liver tumor promotor and inhibitor of GJIC, was given to co-cultures of PC with NEC. DMSO significantly
stabilized (68% on Day 7), while DDT significantly inhibited (8% on Day 7) homotypic GJIC of PC in the respective culture
systems. In contrast, the activities of mEHb, sEH, GST, and ST were not affected in the presence of DMSO or DDT. These results lead to the assumption that the differentiation
parameters measured in this study (i.e., homotypic GJIC and the activities of xenobiotic metabolizing enzymes) are independently
regulated in adult rat liver PC. 相似文献
5.
Fritz Thümmler Margarete Kirchner Raphael Teuber Peter Dittrich 《Plant molecular biology》1995,29(3):551-565
22 novel members of the Arabidopsis thaliana protein kinase family (AKs) were identified by using degenerate oligonucleotide primers directed to highly conserved amino acid sequences of the protein kinase (PK) catalytic domain. Of these 22 genes, 16 turned out to carry intron sequences. Homologies of AK sequences were detected to S-locus receptor protein kinases (SRKs) from Brassica spp., to SRK-like PKs from maize and A. thaliana and to several other receptor PKs from A. thaliana. Sequence similarity was also detected to Ca2+-dependent PKs (CDPKs) from rape and soybean, to SNF1 and to CDC2 homologues. The genomic organization and the accumulation of the mRNAs from these 22 AK genes were investigated. 相似文献
6.
ADENOSINE REGULATES VIA TWO DIFFERENT TYPES OF RECEPTORS, THE ACCUMULATION OF CYCLIC AMP IN CULTURED BRAIN CELLS 总被引:24,自引:2,他引:22
Abstract— In cell cultures of glial character derived from perinatal mouse brain adenosine elicits two effects. (a) At submicromolar concentrations It inhibits the increase in the intracellular level of cyclic AMP caused by β-adrenoceptor agonists. (b) At concentrations above micromolar it increases the level of cyclic AMP in the cultures. These two effects are mediated by two different adenosine receptors present on the outer surface of the cells. This is concluded from the following evidence. (a) Both effects are antagonized by methylxanthines but not by blockage of adenosine uptake or inhibition of phosphodiesterase activity. (b) In both cases activity depends on the integrity of the ribose moiety of the nucleotide. Substituents of the purine system are tolerated comparatively well. (c) The order of potency of adenosine analogues is different for the two effects. We suggest the name A1 receptors for those that mediate the inhibition and A2 for those that mediate the stimulation of cyclic AMP accumulation. 相似文献
7.
Gray R. Kunkel Margarete Mehrabian Harold G. Martinson 《Molecular and cellular biochemistry》1981,34(1):3-13
Summary Contact-site cross-linking agents comprise a heterogeneous grouping of cross-linkers which share the common property of being
able to cross-link only very closely juxtaposed residues in macromolecular complexes. We have defined contact-site cross-linking
arbitrarily as the covalent joining of residues such that they are constrained to a distance which is equivalent to or less
than their closest possible steric approach prior to becoming linked (1). We recognize two classes of contact-site cross-linkers,
bridge type and zero-length type. The former, such as formaldehyde, become incorporated during cross-linking as one-atom bridges.
The latter, such as the carbodiimides, operate as condensing agents with the result that the cross-linked residues become
interjoined directly.
Contact-site cross-linkers have been used in several ways as specific probes of both the static and dynamic aspects of macromolecular
structure. They can yield precise structural information about macromolecular contacts when actual sites of cross-linking
are determined by peptide or nucleotide mapping techniques. In this way exact contacs between histones in the nucleosome,
between protein and RNA in the ribosome, and between RNA polymerase and DNA have been determined. Contact-site cross-linkers
have also been used to probe the perturbation of contacts following macromolecular conformational changes. Certain histonehistone
‘cross-linkable’ sites are rendered unreactive after induction of chromatin conformational changes thus serving to localize
sites of perturbation. 相似文献
8.
9.
10.
Brooke W. Bullington Katherine Klemperer Keith Mages Andrea Chalem Humphrey D. Mazigo John Changalucha Saidi Kapiga Peter F. Wright Maria M. Yazdanbakhsh Jennifer A. Downs 《PLoS pathogens》2021,17(5)
Although a growing number of studies suggest interactions between Schistosoma parasites and viral infections, the effects of schistosome infections on the host response to viruses have not been evaluated comprehensively. In this systematic review, we investigated how schistosomes impact incidence, virulence, and prevention of viral infections in humans and animals. We also evaluated immune effects of schistosomes in those coinfected with viruses. We screened 4,730 studies and included 103. Schistosomes may increase susceptibility to some viruses, including HIV and Kaposi’s sarcoma-associated herpesvirus, and virulence of hepatitis B and C viruses. In contrast, schistosome infection may be protective in chronic HIV, Human T-cell Lymphotropic Virus-Type 1, and respiratory viruses, though further research is needed. Schistosome infections were consistently reported to impair immune responses to hepatitis B and possibly measles vaccines. Understanding the interplay between schistosomes and viruses has ramifications for anti-viral vaccination strategies and global control of viral infections. 相似文献