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821.
Teresa Hazubska-Przybył Paweł Chmielarz Marcin Michalak Krystyna Bojarczuk 《Plant Cell, Tissue and Organ Culture》2010,102(1):35-44
Two-year-old embryogenic tissues (ET) of Picea omorika (Pančić) Purk. were successfully cryopreserved after preculture with sucrose, air-drying for 2 h, and freezing in liquid
nitrogen (LN). The preculture protocol consisted of passaging the ET onto standard Litvay medium containing increasing concentrations
of sucrose (0.25 M sucrose for 24 h, 0.5 M for 24 h, 0.75 M for 2 days, and 1.0 M for 3 days) for 7 days, at 25°C, and in
the dark. The clumps were subsequently air-dried over silica gel, down to a 20% water content (based on fresh weight), placed
in cryovials, and immersed in liquid nitrogen (LN) for 24 h. These were thawed at 42°C and progressively rehydrated in phytagel-solidified
LM media containing decreasing concentrations of sucrose. After 3 weeks of in vitro culture, surviving clumps were friable
and white in color, similar to their morphology prior to cryostorage. The frequency of bacterial and fungal contamination
was higher if ET was frozen in LN-containing vials than in LN-free vials. This efficient cryopreservation protocol would be
useful for the ex-situ conservation of P. omorika germplasm in gene banks at very low temperatures. 相似文献
822.
Reconstruction of past climate change and ecosystem response is important to correctly assess the impacts of global warming.
In this study, we provide a paleoenvironmental record of in-lake and catchment changes in northern Poland during the Late
Glacial and early Holocene using various biotic proxies (pollen, macrofossils and Cladocera) preserved in the lake sedimentary
record. Chronology was derived from palynological correlation with a well-dated pollen sequence from nearby-lying Lake Ostrowite
and some well-dated events of vegetation history in Central Europe. Pollen analysis provided information on regional climate
change affecting vegetation dynamics, whereas macrofossils supplied substantial information on the response of local flora
and fauna to climatic, geomorphological and limnological changes. Data were supplemented by analysis of Cladocera remains,
which are of special importance because of their quick response to changes in trophic conditions and climate (especially temperature).
The bottom of the sediment core reflects an initial stage of the lake formed during the late Aller?d. The Younger Dryas cooling
apparently resulted in forest recession and presence of cold tolerant Cladocera species. Due to amelioration of climate at
the end of the Younger Dryas and melting of ice, the lake deepened. The beginning of the Holocene was characterised by forest
shrinkage and induced clear changes in local flora and fauna communities. The regional vegetation development deduced from
the lake’s core is generally consistent with the vegetation history of central Europe. Due to the location of the site near
the seashore (oceanic climate and western wind), signals of warming came earlier than inland and in eastern Poland. 相似文献
823.
Inga Markiewicz Joanna Sypecka Krystyna Domanska-Janik Tomasz Wyszomirski Barbara Lukomska 《The journal of histochemistry and cytochemistry》2011,59(3):289-301
Cord blood–derived neural stem cells (NSCs) are proposed as an alternative cell source to repair brain damage upon transplantation. However, there is a lack of data showing how these cells are driven to generate desired phenotypes by recipient nervous tissue. Previous research indicates that local environment provides signals driving the fate of stem cells. To investigate the impact of these local cues interaction, the authors used a model of cord blood–derived NSCs co-cultured with different rat brain–specific primary cultures, creating the neural-like microenvironment conditions in vitro. Neuronal and astro-, oligo-, and microglia cell cultures were obtained by the previously described methods. The CMFDA-labeled neural stem cells originated from, non-transformed human umbilical cord blood cell line (HUCB-NSCs) established in a laboratory. The authors show that the close vicinity of astrocytes and oligodendrocytes promotes neuronal differentiation of HUCB-NSCs, whereas postmitotic neurons induce oligodendrogliogenesis of these cells. In turn, microglia or endothelial cells do not favor any phenotypes of their neural commitment. Studies have confirmed that HUCB-NSCs can read cues from the neurogenic microenvironment, attaining features of neurons, astrocytes, or oligodendrocytes. The specific responses of neurally committed cord blood–derived cells, reported in this work, are very much similar to those described previously for NSCs derived from other “more typical” sources. This further proves their genuine neural nature. Apart from having a better insight into the neurogenesis in the adult brain, these findings might be important when predicting cord blood cell derivative behavior after their transplantation for neurological disorders. 相似文献
824.
825.
The present study is aimed at understanding the effects of DNA sequence, local conformation, and curvature on groove geometry. Energy-optimized structures are obtained by Jumna methodology; groove geometry is analyzed by a recently developed technique that allows an accurate and continuous measurement of width and depth. The mechanics of groove deformations is also studied and analyzed in terms of helicoidal parameters. © 1993 John Wiley & Sons, Inc. 相似文献
826.
Evaluating the 'Labeled Magnitude Scale' for Measuring Sensations of Taste and Smell 总被引:3,自引:2,他引:1
Green Barry G.; Dalton Pamela; Cowart Beverly; Shaffer Greg; Rankin Krystyna; Higgins Jennifer 《Chemical senses》1996,21(3):323-334
The Labeled Magnitude Scale (LMS) is a semantic scale of perceptualintensity characterized by a quasi-logarithmic spacing of itsverbal labels. The LMS had previously been shown to yield psychophysicalfunctions equivalent to magnitude estimation (ME) when gustatory,thermal and nociceptive stimuli were presented and rated together,and the upper bound of the LMS was defined as the strongestimaginable oral sensation. The present study comparedthe LMS to ME within the more limited contexts of taste andsmell. In Experiment 1, subjects used both methods to rate eithertaste intensity produced by sucrose and NaCl or odor intensityproduced by acetic acid and phenyl ethyl alcohol, with the upperbound of the LMS defined as either the strongest imaginabletaste or the strongest imaginable odor.The LMS produced psychophysical functions equivalent to thoseproduced by ME. In Experiment 2 a new group of subjects usedboth methods to rate the intensity of three different tastequalities, with the upper bound of the LMS defined as the strongestimaginable [sweetness, saltiness, or bitterness]. Inall three cases the LMS produced steeper functions than didME. Experiment 3 tested the hypothesis that the LMS yields datacomparable to ME only when the perceptual domain under studyincludes painful sensations. This hypothesis was supported whenthe LMS again produced steeper functions than ME after subjectshad been explicitly instructed to omit painful sensations (e.g.the burn of hot peppers) from the concept of strongestimaginable taste. We conclude that the LMS can be usedto scale sensations of taste and smell when they are broadlydefined, but that it should be modified for use in scaling specifictaste (and probably odor) qualities. The implications of theseresults for theoretical issues related to ME, category-ratioscales and the size of the perceptual range in different sensorymodalities are discussed. Chem. Senses 21: 323334, 1996. 相似文献
827.
828.
Background
MCF-10A, immortalized but non-transformed human breast epithelial cells, are widely used in research examining carcinogenesis. The studies presented here were initiated with the observation that MCF-10A cells left in continuous culture for prolonged periods without re-feeding were prone to the development of transformed foci. We hypothesized that the depletion of labile culture components led to the onset of processes culminating in the observed cell transformation. The purpose of this study was to define the factors which promoted transformation of this cell line. 相似文献829.
The purpose of the present study was to test the taxonomic value of sclerenchyma in distinguishing Pinus sylvestris and P. mugo, P. uncinata, P. rotundata and P. uliginosa, all representing the subsection Sylvestres within the genus Pinus. Thirty-six samples were gathered in natural populations. Every sample was represented with 30 individuals, every individual with 10 brachyblasts. Three types of sclerenchymatic cells surrounding the resin canals and four between vascular bundles were distinguished. Relations among samples and taxa were verified using discriminant analysis and clustering based on Euclidean distances. The types of sclerenchymatic cells surrounding the resin canals and located between the vascular bundles differentiate the compared taxa when used as average frequencies but are extremely variable and do not allow the classification of every individual. The study demonstrated that the type of sclerenchymatic cells surrounding the resin canals and between the vascular bundles in needles could have an important taxonomic value in distinguishing the taxa of two-needle pines of the subsection Sylvestres in Europe at the population level. The distinguishing of individuals was difficult because of very high variation of sclerenchyma characters. 相似文献
830.