全文获取类型
收费全文 | 402篇 |
免费 | 42篇 |
出版年
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 5篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 11篇 |
2017年 | 10篇 |
2016年 | 13篇 |
2015年 | 9篇 |
2014年 | 8篇 |
2013年 | 21篇 |
2012年 | 17篇 |
2011年 | 31篇 |
2010年 | 26篇 |
2009年 | 22篇 |
2008年 | 23篇 |
2007年 | 26篇 |
2006年 | 17篇 |
2005年 | 18篇 |
2004年 | 3篇 |
2003年 | 6篇 |
2002年 | 7篇 |
2001年 | 8篇 |
2000年 | 11篇 |
1999年 | 7篇 |
1997年 | 7篇 |
1996年 | 12篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 8篇 |
1991年 | 5篇 |
1990年 | 8篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 10篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1972年 | 3篇 |
1970年 | 2篇 |
1967年 | 3篇 |
1966年 | 2篇 |
1960年 | 1篇 |
排序方式: 共有444条查询结果,搜索用时 15 毫秒
81.
The comparative morphological study in different Acipenseriform species demonstrates that there are only two morphological features combining the kaluga and the great sturgeon and separating them from other sturgeons, namely the shape of a mouth and the manner attaching of gill membranes to isthmus in adult specimens; whereas many morphological characters are different in these species. The relations of morphological similarity/distinction among different sturgeon species and polyphyletic origin of genus Huso revealed by both molecular and cytogenetic studies presume the restoration of initial taxonomic states for the great sturgeon and kaluga as members of the same genus Acipenser, namely A. huso and A. dauricus. 相似文献
82.
L. A. Vasil’ev E. V. Dzyubinskaya R. A. Zinovkin D. B. Kiselevsky N. V. Lobysheva V. D. Samuilov 《Biochemistry. Biokhimii?a》2009,74(9):1035-1043
Chitosan, CN−, or H2O2 caused the death of epidermal cells (EC) in the epidermis of pea leaves that was detected by monitoring the destruction of
cell nuclei; chitosan induced chromatin condensation and marginalization followed by the destruction of EC nuclei and subsequent
internucleosomal DNA fragmentation. Chitosan did not affect stoma guard cells (GC). Anaerobic conditions prevented the chitosan-induced
destruction of EC nuclei. The antioxidants nitroblue tetrazolium or mannitol suppressed the effects of chitosan, H2O2, or chitosan + H2O2 on EC. H2O2 formation in EC and GC mitochondria that was determined from 2′,7′-dichlorofluorescein fluorescence was inhibited by CN− and the protonophoric uncoupler carbonyl cyanide m-chlorophenylhydrazone but was stimulated by these agents in GC chloroplasts. The alternative oxidase inhibitors propyl gallate
and salicylhydroxamate prevented chitosan- but not CN−-induced destruction of EC nuclei; the plasma membrane NADPH oxidase inhibitors diphenylene iodonium and quinacrine abolished
chitosan- but not CN−-induced destruction of EC nuclei. The mitochondrial protein synthesis inhibitor lincomycin removed the destructive effect
of chitosan or H2O2 on EC nuclei. The effect of cycloheximide, an inhibitor of protein synthesis in the cytoplasm, was insignificant; however,
it was enhanced if cycloheximide was added in combination with lincomycin. The autophagy inhibitor 3-methyladenine removed
the chitosan effect but exerted no influence on the effect of H2O2 as an inducer of EC death. The internucleosome DNA fragmentation in conjunction with the data on the 3-methyladenine effect
provides evidence that chitosan induces programmed cell death that follows a combined scenario including apoptosis and autophagy.
Based on the results of an inhibitor assay, chitosan-induced EC death involves reactive oxygen species generated by the NADPH
oxidase of the plasma membrane. 相似文献
83.
Background
Solving a task with insight has been associated with occipital and right-hemisphere activations. The present study tested the hypothesis if sleep-related alterations in functional activation states modulate the probability of insight into a hidden abstract regularity of a task.Methodology
State-dependent functional activation was measured by beta and alpha electroencephalographic (EEG) activity and spatial synchronization. Task-dependent functional activation was assessed by slow cortical potentials (SPs). EEG parameters during the performance of the Number Reduction Task (NRT) were compared between before sleep and after sleep sessions. In two different groups, the relevant sleep occurred either in the first or in the second half of the night, dominated by slow wave sleep (SWS) or by rapid eye movement (REM) sleep.Principal Findings
Changes in EEG parameters only occurred in the early-night group, not in the late-night group and indicated occipital and right-hemisphere functional alterations. These changes were associated with off-line consolidation of implicit task representations and with the amount of SWS but they did not predict subsequent insight. The gain of insight was, however, independently associated with changes of spectral beta and alpha measures only in those subjects from the two sleep groups who would subsequently comprehend the hidden regularity of the task. Insight-related enhancement of right frontal asymmetry after sleep did not depend on sleep stages.Significance
It is concluded that off-line restructuring of implicit information during sleep is accompanied by alterations of functional activation states after sleep. This mechanism is promoted by SWS but not by REM sleep and may contribute to attaining insight after sleep. Original neurophysiologic evidence is provided for alterations of the functional activation brain states after sleep. These alterations are associated with a decrease in controlled processing within the visual system and with an increase in the functional connectivity of the right hemisphere, and are supported by SWS in the first half of the night. 相似文献84.
E. S. Chermnykh N. V. Radyukhina P. N. Rutkevich A. Ya. Shevelev T. N. Vlasik E. A. Vorotelyak A. V. Vasil’ev V. V. Terskikh 《Cell and Tissue Biology》2010,4(3):245-250
In the present work, we labeled human epidermal keratinocytes and dermal papilla cells in order to study their behavior after
intradermal transplantation. The cells were transduced by lentiviral vectors that bore a marker gene that encodes green fluorescent
protein (copGFP) or red fluorescent protein (DsRed). A portion of the transgene expressing cells was evaluated by flow cytometry.
The proposed genetic constructions have allowed one to achieve high efficiency (>95%) of the transduction of hair follicle
cells. The in vitro transduced cells were injected under epidermis of human skin fragments, after which these fragments were
transplanted under the skin of immunodeficient mice. The injected epidermal keratinocytes were found mainly in hair follicles
and partially in the zone of interfollicular epidermis, while dermal papilla cells were found in the papilla of the derma.
The results of the present study have shown that the chosen genetic constructions obtained based on human immunodeficiency
lentivirus are capable of the effective and stable transduction of human skin cells. The injected cells survived and were
found in the corresponding skin structures. 相似文献
85.
Study of structural and rheological properties of starch isolated from genetically modified potato 总被引:1,自引:0,他引:1
A. V. Kanarskii Z. A. Kanarskaya D. Sh. Yagofarov L. A. Wasserman V. G. Vasil’ev K. G. Skryabin A. M. Kamionskaya 《Applied Biochemistry and Microbiology》2011,47(9):827-832
It has been found in this work that the starchiness and starch content in tubers of GM potato and tubers of initial Lugovskoi
potato variety are identical. No differences and difficulties were observed upon starch preparation from GM and common potato.
Starch samples isolated from GM potato conform to the current standard for potato starch. The starch isolated from GM potato
has a higher melting point, i.e., it is more thermally stable as compared with the starch isolated from a control sample.
The bulk modulus of gels obtained from starch isolated from GM potato is higher in comparison with that of gels prepared from
starch isolated from the control sample. Thermodynamic and rheological properties of starch from GM potato provide a possibility
to predict its application in the manufacture of thermostable and strong polymeric materials. 相似文献
86.
Nina Stancheva Jost Weber Josef Schulze Kalina Alipieva Jutta Ludwig-Müller Christiane Haas Vasil Georgiev Thomas Bley Milen Georgiev 《Plant Cell, Tissue and Organ Culture》2011,105(1):79-84
A cell suspension culture of Devil’s claw (Harpagophytum procumbens), a South African plant with high medicinal value, cultivated under submerged conditions showed stable growth and accumulated
high amounts of biomass (18.2 g l−1). Flow cytometry analyses of the suspension’s cell cycle kinetics showed that proportions of cells in G0/G1 and S phases varied insignificantly (between 69–76% and 9–13%, respectively) during the cultivation, while the proportion
of G2/M-phase cells increased until day 8 of cultivation, when the exponential phase of cell growth ended. Metabolite production
in the culture was studied through simultaneous determination of three bioactive phenylethanoid glycosides (verbascoside,
β-OH-verbascoside and leucosceptoside A) by high performance liquid chromatography. It was found that suspended Devil’s claw
cells accumulated mainly verbascoside (517.3 mg l−1), followed by leucosceptoside A (107.1 mg l−1) and β-OH-verbascoside (80.3 mg l−1). In addition, several fatty acids and β-sitosterol were identified in the cell suspension by gas chromatographic-mass spectrometry
analysis. Comparison of the results with previously acquired data for Harpagophytum procumbens transformed roots indicate that cell suspensions cultures are more promising as potential commercial sources of metabolites
such as phenylethanoid glycosides. 相似文献
87.
Understanding biological processes assumes a detailed understanding of the interaction of all involved molecules. Here the
effect of the peptide hormone angiotensin II (Ang II), an agonist of the angiotensin receptors, on the structure of unilamellar
and multilamellar dimyristoyl phosphatidylcholine vesicles was studied by small angle neutron scattering, dynamic light scattering
and differential scanning calorimetry. The calorimetry data indicate a weak interaction of Ang II with the surface of the
membrane bilayer, as the pretransition persists during all experiments, and the main transition is only slightly shifted towards
higher temperatures. From the SANS data we were able to confirm the calorimetric data and verify the interaction of the hormone
with the membrane surface. At low temperatures, when the lipid molecules are in the gel phase, more precisely in the ripple
phase, the peptide penetrates in the head group core, but due to the close packing of the acyl chains, the hydrophobic region
is not affected. In a temperature region below but close to the region of the phase transition, the hydrophibic core starts
to be affected by the peptide, and the same is true for the fluid phase. Upon binding of the peptide, the thickness of the
head group increases, and the scattering length density of the head group starts to rise with increasing peptide concentrations.
This interaction and binding to the membrane surface may be relevant for the relocation, binding and reconstitution of the
angiotensin receptors into the membrane. Second, the peptide adsorption to the membrane surface may contribute to the binding
of Ang II in the active site of the receptor. 相似文献
88.
M. Yu. Dyakov O. V. Kamzolkina O. V. Shtaer N. A. Bis’ko N. L. Poedinok O. B. Mikhailova O. V. Tikhonova T. E. Tolstikhina B. F. Vasil’eva O. V. Efremenkova 《Microbiology》2011,80(2):274-285
Twenty-one strains belonging to 18 species of basidiomycetes from different ecological groups of fungi were isolated from
natural sources. Light and electron microscopy was used to determine the morphological properties of the cultures, which confirmed
their classification as basidiomycetes and facilitated their identification in monocultures. The capacity of the fungal strains
for biosynthesis of antibiotics was determined by one- or two-stage cultivation on seven nutrient media. It was established
that, under submerged cultivation, antimicrobial substances were formed by 13 strains (81.25%) of 12 fungal species (Armillaria sp., Coprinus comatus, Flammulina velutipes, Hypsizygus ulmarius, Lentinus tigrinus, Lycoperdon pyriforme, Macrolepiota procera,
Panellus serotinus, Pholiota aurivella, Pholiota lenta, Rhodocollybia maculate, and Sparassis crispa). The antibiotics formed were efficacious against bacterial test strains, including the methicillin-resistant strain Staphylococcus aureus (MRSA) and the strain Leuconostoc mesenteroides VKPM B-4177 that is resistant to the glycopeptide antibiotics. No antibiotic activity was revealed against fungal test cultures
(Aspergillus niger INA 00760 and Saccharomyces cerevisiae RIA 259). 相似文献
89.
Andrey Marchev Christiane Haas Sibylle Schulz Vasil Georgiev Juliane Steingroewer Thomas Bley Atanas Pavlov 《Biotechnology letters》2014,36(2):211-221
Extracts of Salvia species are used in traditional medicine to treat various diseases. The economic importance of this genus has increased in recent years due to evidence that some of its secondary metabolites have valuable pharmaceutical and nutraceutical properties.The bioactivity of sage extracts is mainly due to their content of terpenes and polyphenols. The increasing demand for sage products combined with environmental, ecological and climatic limitations on the production of sage metabolites from field-grown plants have led to extensive investigations into biotechnological approaches for the production of Salvia phytochemicals. The purpose of this review is to evaluate recent progress in investigations of sage in vitro systems as tools for producing important terpenoids and polyphenols and in development of methods for manipulating regulatory processes to enhance secondary metabolite production in such systems. 相似文献
90.
Yordanka G. Gluhcheva Vasil N. Atanasov Juliana M. Ivanova Ekaterina H. Pavlova 《Central European Journal of Biology》2014,9(10):973-981
An in vivo experimental model for testing the effects of long-term chronic treatment with cobalt(II) compounds — cobalt chloride (CoCl2) and cobalt-EDTA (Co-EDTA) on mice at different stages of development was optimized. Pregnant mice and their progeny were treated with daily doses of 75 or 125 mg kg?1 body weight until postnatal day 90. The compounds were dissolved in regular tap water. Mice were sacrificed on days 18, 25, 30, 45, 60 and 90 after birth, which correspond to different stages of their development. Altered organ weight indices (calculated as a ratio of organ weight to body weight) of spleen, liver and kidneys, were found depending on the type of compound used, dose, duration of treatment, and the age of the animals. The results also showed significant accumulation of cobalt ions in blood plasma, spleen, liver and kidneys of the exposed mice. More Co(II) was measured in the organs of the immature mice (day 18, 25 and 30 pnd) indicating that they were more sensitive to treatment. 相似文献