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331.
The importance of cellular polyamine (PA) levels and the ratio of putrescine (Put) to spermidine (Spd) for plant regeneration ability via somatic embryogenesis in several commercially grown indica rice varieties is reported here. The genotypes namely NDR-624, IR-20, IR-36, BJ-1 (having Put:Spd ratio2.3) showed superior plant regeneration while KL, PB-1 and TN-1 (having Put:Spd ratio3.8) showed moderate plant regeneration ability. The genotypes namely HS, Bindli, DV-85, ACB-72, IR-64 and IR-72 (having Put:Spd ratio5.0) showed poor plant regeneration ability. In contrast KH-7 (Put:Spd ratio10.0) showed no response at all. Favorable modification of cellular PA titers and their Put:Spd ratio by the addition of exogenous PAs (Put, Spd) or their biosynthesis inhibitor, difluoromethylarginine (DFMA) led to the induction/promotion of plant regeneration in poorly responding genotypes. These results showed a close relationship between cellular PA levels and their Put:Spd ratio with in vitro morphogenetic capacity in indica rice and suggest that the cellular PAs and Put:Spd ratios are important determinants (biomarkers) of plant regeneration ability in indica rice, and the improvement/induction of plant regeneration in morphogenetically poor and recalcitrant species could be achieved by modulating PA metabolism. 相似文献
332.
333.
G. Pichan R. K. Gauttam O. S. Tomar A. C. Bajaj 《International journal of biometeorology》1988,32(3):176-180
Physical work capacity (PWC180) was assessed with different levels of hypohydration in 25 heat-acclimatized male volunteers in hot dry (45°C DB, 30% RH) and hot humid (39°C DB, 60% RH) conditions equated to a heat stress level of 34°C on the WBGT scale. Heat acclimatization was carried out by exposing the subjects for 8 consecutive days in a climatic chamber with moderate work for two 50 min work cycles and 10 min intervening rest pauses. Acclimatization resulted in significant decreases in heart rate (27 bpm), oral temperature (0.8°C), mean skin temperature (1.2°C) and a significant increase in sweating rate (120 g h–1 m–2). Day-to-day variations in body hypohydration levels during heat acclimatization were not significantly different, although water intake was found to increase significantly from day 3 onwards when the subjects were in ad lib water intake state. The heat acclimatized subjects were then hypohydrated to varying degrees, viz. 1%, 2% and 3% body weight deficit, with moderate work in heat in the climatic chamber and after successful recovery from the effects of thermal stress and exercise; their physical work capacity was assessed individually. Physical work capacity was found to decrease significantly with hypohydration as compared to controls. The decrease was of the order of 9%, 11% and 22% in the hot dry condition and 6%, 8% and 20% in the hot humid condition with hypohydration levels of 1%, 2% and 3% respectively. The decrease was more pronounced during 3% hypohydration level under both heat stress conditions. This decrease was in spite of significant increases in maximal ventilation. However, the PWC180 under the two heat stress conditions, when compared, did not reveal any significant difference. It was concluded that the heat stress vehicle did not adversely affect the physical work capacity. On the other hand, the decreases in physical work capacity were found to be closely related to the primary hypohydration level in heat-acclimatized tropical subjects.Abbreviations
WBGT
wet bulb globe temperature
-
bam
beats per minute
-
YSI
Yellow Springs Instrument
-
EKG
electrocardiogram 相似文献
334.
335.
Widespread distribution of deletions of the bgl operon in natural isolates of Escherichia coli 总被引:2,自引:0,他引:2
A deletion that includes the bgl (beta-glucoside utilization) operon of
Escherichia coli was originally detected in several rarely occurring
natural isolates that utilize cellobiose. Here I show that bgl deletions
are present in 95% of the Cel+ isolates obtained from diverse sources. They
are also present in 29% of the Cel- strains in two different collections of
natural isolates of E. coli. At least three versions of bgl deletions are
present in E. coli populations. In the most common version approximately 8
kb of DNA around the bgl region of E. coli K12 is replaced by a specific
6.5-kb DNA fragment. In another version a deletion of similar length is not
replaced by the same sequence. A third version involves deletion of
approximately 14 kb without the replacement fragment being present. The
distribution of these deletions suggests that the version 1 deletion
occurred very early in the history of E coli. It also appears likely that
there is selection for bgl deletions in Cel+ strains of E. coli. The
presence of the version 1 deletion within distantly related phylogenetic
groups of E. coli provides evidence for recombination within natural
populations of E coli.
相似文献
336.
Hadi N Yehia Rockford K Draper Carole Mikoryak Erin Kate Walker Pooja Bajaj Inga H Musselman Meredith C Daigrepont Gregg R Dieckmann Paul Pantano 《Journal of nanobiotechnology》2007,5(1):8-17
This work concerns exposing cultured human epithelial-like HeLa cells to single-walled carbon nanotubes (SWNTs) dispersed
in cell culture media supplemented with serum. First, the as-received CoMoCAT SWNT-containing powder was characterized using
scanning electron microscopy and thermal gravimetric analyses. Characterizations of the purified dispersions, termed DM-SWNTs,
involved atomic force microscopy, inductively coupled plasma – mass spectrometry, and absorption and Raman spectroscopies.
Confocal microRaman spectroscopy was used to demonstrate that DM-SWNTs were taken up by HeLa cells in a time- and temperature-dependent
fashion. Transmission electron microscopy revealed SWNT-like material in intracellular vacuoles. The morphologies and growth
rates of HeLa cells exposed to DM-SWNTs were statistically similar to control cells over the course of 4 d. Finally, flow
cytometry was used to show that the fluorescence from MitoSOX™ Red, a selective indicator of superoxide in mitochondria, was
statistically similar in both control cells and cells incubated in DM-SWNTs. The combined results indicate that under our
sample preparation protocols and assay conditions, CoMoCAT DM-SWNT dispersions are not inherently cytotoxic to HeLa cells.
We conclude with recommendations for improving the accuracy and comparability of carbon nanotube (CNT) cytotoxicity reports. 相似文献
337.