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991.
992.
Up-regulation of NPY gene expression in hypothalamus of rats with experimental chronic renal failure
Sucajtys-Szulc E Karbowska J Kochan Z Wolyniec W Chmielewski M Rutkowski B Swierczynski J 《Biochimica et biophysica acta》2007,1772(1):26-31
Anorexia is possibly one of the most important causes of malnutrition in uremic patients. The cause of this abnormality is still unknown. Considering that: (a) NPY is one of the most important stimulants of food intake; (b) eating is a central nervous system regulated process and (c) NPY is expressed in hypothalamus, we hypothesized that the decrease of NPY gene expression in the hypothalamus could be an important factor contributing to anorexia associated with uremic state. In contrast to the prediction, the results presented in this paper indicate that the NPY gene expression in the hypothalamus of chronic renal failure (CRF) rats was significantly higher than in the hypothalamus of control (pair-fed) rats. Moreover, we found that serum NPY concentration in CRF rats was higher than in control (pair-fed) animals. The increase of plasma NPY concentration in CRF rats may be due to the greater synthesis of the neuropeptide in liver, since higher level of NPY mRNA was found in liver of CRF rats. The results obtained revealed that experimental chronic renal failure is associated with the increase of NPY gene expression in hypothalamus and liver of rats. 相似文献
993.
We applied the Cocktail method to a large data set of 4 117 relevés of all Slovak vegetation types with the aim to create
formalised definitions of all Slovakian mire plant associations. We defined 21 groups of species with the statistical tendency
of joint occurrences in vegetation. These groups differed substantially in their position along the pH/calcium gradient. We
further defined 24 plant associations according to presence and/or absence of certain groups and/or strong dominance of some
species. Only six traditional plant associations were not possible to be reproduced this way. We applied our formalised definitions
to the regional data set of mires from the surrounding of the Vysoké Tatry Mts. Combined with frequency-positive fidelity
index this method has led to the classification of the majority of vegetation plots into ten associations. When the vegetation
types obtained from Cocktail-based classification and from cluster analysis were compared with respect to measured pH and
conductivity in the study region, 82% of pairs differed significantly either in pH or in water conductivity in the former
classification and 69% in the latter one. 相似文献
994.
995.
Calli were induced from mature caryopses of timothy grass (Phleum pratense L.) on MS medium (Murashige and Skoog 1962) supplemented with 500 mg·dm−3 casein hydrolysate and 5 mg·dm−3 2,4-D (2,4-dicholorophenoxyacetic acid) or 2 mg·dm−3 dicamba (3,6-dichloro-o-anisic acid). Twelve-week-old calli were passaged on media with reduced levels of auxins (2 mg·dm−3 2,4-D or 1 mg·dm−3 dicamba). Tissues induced on medium with 2,4-D were transferred on medium with 2,4-D and on medium with dicamba; parallely
calli initiated on medium with dicamba were passaged on medium with 2,4-D or dicamba. Calli from various media sequences were
used to establish cell suspension cultures in media containing 2 mg·dm−3 2,4-D or 1 mg·dm−3 dicamba. An assessment of regeneration ability of calli was made on MS medium containing 0.2 mg·dm−3 kinetin. Callus tissue induced and/or subcultured on any of the media with 2,4-D did not regenerate plants while dicamba
added to the media was the effective stimulator of regenerability. In the presence of 2,4-D calli and suspensions produced
a jelly-like extracellular matrix. In cell suspension this phenomenon was observed 4–5 days after each passage. The measurements
of electric potential of calli, growing on MS medium with kinetin were performed. Non-regenerating callus areas had an electric
potential close to 0 mV while parts of tissue with meristematic centres were characterized by lower values of electric potential. 相似文献
996.
Havránek Vladimír Kučera Jan Horáková Jitka Voseček Václav Smolík JiŘí Schwarz Jaroslav Sýkorová Ivana 《Biological trace element research》1999,(1):431-442
A comparison of instrumental neutron activation analysis (INAA) and proton-induced X-ray emission (PIXE) results for sizefractionated
atmospheric aerosols (“coarse” and “fine” fractions with an equivalent aerodynamic diameter of 2–10 Μm and < 2 Μm, respectively,
or the PM10 fraction) showed that PIXE yielded significantly lower results for the PM10 and coarse fractions, especially for
elements with a low Z resulting from a particle size effect. Somewhat lower PIXE results were also obtained for the fine fraction
of atmospheric aerosols. A correction is also needed for irregularly shaped deposits of combustion aerosols collected by a
cascade impactor in 11 size fractions ranging from 0.016 to 14.3 Μm, as well as for thick samples of fly and bottom ashes.
An equivalent layer thickness (ELT) model is proposed to correct the matrix effects in PIXE. The approaches for the calculation
of ELT using a comparison of PIXE and INAA results or by comparing PIXE results obtained using two different incident proton
beam energies (1.31 and 2.35 MeV) are described. The correction for the ash pellets and irregular deposits are also discussed. 相似文献
997.
Mira Horv’athov’a Eva Jahnov’a František Gazd’ik 《Biological trace element research》1999,69(1):15-26
Endothelial cells play a major role in immunologic reactions, in which cellular adhesion molecules P-selectin, ICAM-1, VCAM-1,
and ELAM-1 are important mediators in the recruitment of leukocytes in pulmonary inflammation. Selenium (Se) is known to modulate
immunological mechanisms of asthma. The aim of our investigation was to examine whether Se supplementation in cortico-dependent
asthmatic patients may modulate adhesion molecule expression in cultured endothelium. Our findings indicated that P-selectin,
VCAM-1, and ELAM-1 expression on human umbilical vein endothelial cells stimulated with peripheral blood mononuclear cells
obtained from asthmatics before supplementation with Se was significantly higher than from healthy donors (p < 0.05). The production of ICAM-1 showed only slight augmentation. The levels of VCAM-1 and ELAM-1 expression were significantly
decreased after 3 mo of Se supplementation (p < 0.05). After 6 mo of intervention period the intensity of P-selectin and ICAM-1 expression was also significantly reduced
(p < 0.05 andp < 0.01, respectively). The inhibitory effect of Se on the adhesion molecule expression was studied in cultured endothelial
cells after interferon-γ stimulation. Our data suggest that Se affects the expression of P-selectin, ICAM-1, VCAM-1, and ELAM-1
in a dosedependent manner and the half-maximal inhibitory concentrations were 3.4, 0.5, 4, and 3.8 μg/mL, respectively. The
maximal inhibitions (greater than 80%) were observed in vitro with 10 μg/mL Se (p < 0.01). Regulation of adhesion molecule expression may be an important mechanism through which the inflammation may be controlled. 相似文献
998.
Atriplex sagittata is a heterocarpic species producing three types of fruits which differ in morphology and ecological properties. This study
focused on variation in biomass allocation into particular fruit types under different density and fertilization levels. The
reduction in total weight under stressful conditions was accompanied by a reduction of reproductive structures in terms of
both total fruit production and mean fruit weight. Allocation of biomass to particular fruit types under different density-fertilization
treatments showed considerable variation. The non-dormant, bracteolate fruit type (termed C) contributed 80–90% to the total
fecundity and its production was not affected by density-fertilization treatments. The production of this fruit type is higher
in the upper part of the maternal plant stem. Production of the very dormant ebracteate fruit type (termed A) increased under
favourable conditions and was greater on the lower part of the stem, whereas more of the so-called type B fruit (covered by
bracteoles and exhibiting dispersal and dormancy characteristics intermediate between types A and C) was produced under suboptimal
conditions and was concentrated in the middle part of the plant body. This pattern contradicts to some extent the theory that
deeply dormant and less dispersible fruits will be produced under stressful conditions and may be considered a new model for
the behaviour of plants with more than two heterocarpic fruits. The type B fruit, intermediate in both morphology and ecological
behaviour, provides a continuum between extreme strategies.
Received: 8 February 1998 / Accepted: 19 November 1998 相似文献
999.
Horst Walter J. Schmohl Nicole Kollmeier Malte Balu ka Franti ek Sivaguru Mayandi 《Plant and Soil》1999,215(2):163-174
The mechanism of aluminium-induced inhibition of root elongation is still not well understood. It is a matter of debate whether
the primary lesions of Al toxicity are apoplastic or symplastic. The present paper summarises experimental evidence which
offers new avenues in the understanding of Al toxicity and resistance in maize. Application of Al for 1 h to individual 1
mm sections of the root apex only inhibited root elongation if applied to the first 3 apical mm. The most Al-sensitive apical
root zone appeared to be the 1–2 mm segment. Aluminium-induced prominent alterations in both the microtubular (disintegration)
and the actin cytoskeleton (altered polymerisation patterns) were found especially in the apical 1–2 mm zone using monoclonal
antibodies. Since accumulation of Al in the root apoplast is dependent on the properties of the pectic matrix, we investigated
whether Al uptake and toxicity could be modulated by changing the pectin content of the cell walls through pre-treatment of
intact maize plants with 150 mM NaCl for 5 days. NaCl-adapted plants with higher pectin content accumulated more Al in their
root apices and they were more Al-sensitive as indicated by more severe inhibition of root elongation and enhanced callose
induction by Al. This special role of the pectic matrix of the cell walls in the modulation of Al toxicity is also indicated
by a close positive correlation between pectin, Al, and Al-induced callose contents of 1 mm root segments along the 5 mm root
apex. On the basis of the presented data we suggest that the rapid disorganisation of the cytoskeleton leading to root growth
inhibition may be mediated by interaction of Al with the apoplastic side of the cell wall – plasma membrane – cytoskeleton
continuum.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
1000.
Jiří Masojídek Giuseppe Torzillo Michal Koblížek Jiří Kopecký Paola Bernardini Angelo Sacchi Josef Komenda 《Planta》1999,209(1):126-135
The role of the xanthophyll cycle in the adaptation of two chlorococcal algae Scenedesmus quadricauda and Chlorella sorokiniana to high irradiance was studied under laboratory and outdoor conditions. We wished to elucidate whether the xanthophyll cycle
plays a key role in dissipating the excesses of absorbed light, as in higher plants, and to characterise the relationship
between chlorophyll fluorescence parameters and the content of xanthophyll-cycle pigments. The xanthophyll cycle was found
to be operative in both species; however, its contribution to overall non-photochemical quenching (NPQ) could only be distinguished
in Scenedesmus (15–20% of total NPQ). The Scenedesmus cultures showed a larger pool of xanthophyll-cycle pigments than Chlorella, and lower sensitivity to photoinhibition as judged from the reduction of maximum quantum yield of photosystem II. In general,
both algae had a larger xanthophyll-cycle pool when grown outdoors than in laboratory cultures. Comparing the two species,
Scenedesmus exhibited a higher capacity to adapt to high irradiance, due to an effective quenching mechanism and high photosynthetic
capacity; in contrast, Chlorella represents a species with a larger antennae system, less-efficient quenching and lower photosynthetic performance. Non-photochemical
quenching (NPQ) induced through the xanthophyll cycle can, to a limited extent, represent a regulatory factor in diluted algal
cultures grown in outdoor solar photobioreactors, as well as in natural algal phytoplankton populations exposed transiently
to high irradiance. However, it does not play an appreciable role in dense, well-mixed microalgal suspensions.
Received: 6 August 1998 / Accepted: 12 February 1999 相似文献