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11.
The linear-transfer and lag-Manly models of zooplankton cohortdevelopment were examined using data generated from a thirdmore realistic model. The more realistic multi-transfer modelincluded variance in development rate among individuals. Thelinear-transfer model produced highly biased estimates of developmentrate under conditions of rapidly changing recruitment. Althoughits performance was improved by increasing the number of modeledstages and thus decreasing the rate of change in recruitmentcompared to stage duration, a positive bias remained. The lag-Manlymodel also produced positively biased estimates of stage durationgiven non-zero variance in development rates. A comparison ofthe models' performances under different simulated samplingregimes recommended the multi-transfer model. Use of the multi-transfermodel was illustrated by determining the development and mortalityrates of the brine shrimp, Artemia monica reared under threedifferent conditions of food and temperature corresponding tonatural regimes in Mono Lake, California. The experimental conditionsand sampling regime resulted in high relative standard errors(mean, 33%) in stage abundance estimates not atypical of zooplanktonsampling regimes in lakes. A Monte Carlo analysis was used todetermine the uncertainty in estimated parameters and determinethe level of stage aggregation which maximized the amount ofinformation derived from the experiments. 相似文献
12.
Genetic analysis suggests functional interactions between the N- and C-terminal domains of the TetA(C) efflux pump encoded by pBR322.
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Genetic analysis of the tetA(C) gene of pBR322 indicates the importance of two-cytoplasmic loops in the TetA(C) protein (P. McNicholas, I. Chopra, and D. M. Rothstein, J. Bacteriol. 174:7926-7933, 1992). In this study, we characterized second-site suppressor mutations that suggest a functional interaction between these two cytoplasmic regions of the protein. 相似文献
13.
Since the discovery in 1971 of opiate receptors and later of the opiate-like peptides, there has been widespread interest in determining their exact localization, number and kinds, nature, and physiological and pharmacological functions. Between 1971 and 1978, vast amounts of research investigated these problem areas, but in 1979 alone the literature on the opiate peptides nearly doubled. This review is the second of an annual series and summarizes the highlights of the work published during 1979. 相似文献
14.
Richard D. Olson Abba J. Kastin Thomas K. von Almen David H. Coy Gayle A. Olson 《Peptides》1980,1(4):383-385
Twenty-four male albino rats were given daily intraperitoneal injections of vasoactive intestinal polypeptide (VIP), motilin, human gastrin I (1–17) or the diluent control vehicle at a dose of 100 μg/kg for four consecutive days and food intake, water intake, body weight, and running wheel activity were determined every 24 hours. Animals injected with motilin or human gastrin I (1–17) exhibited decreased food intake relative to those injected with VIP or diluent, which did not differ from each other, although food intake increased reliably over days. The mean water consumption followed the same pattern as that of food intake. As expected from the above results, VIP produced weight gains as compared with rats injected with motilin or gastrin but not reliably more than after diluent. A reliable effect of trials for weight gain was the greatest on day three. Running wheel activity was not affected by injections of human gastrin I (1–17), motilin, or diluent but was reliably decreased by VIP. No significant differences existed across days. Although the results indicate that GI peptides may affect behavior when injected systemically and that like other peptides they have multiple effects, caution is urged in the interpretation of behavioral results at this time. 相似文献
15.
The rate of efflux of L-glutamate from renal brush-border membrane vesicles was enhanced by Na+ and by extravesicular L-glutamate, but not by D-glutamate nor analogs of L-glutamate that do not share the Na+-L-glutamate co-transport system. These results suggest that efflux was mediated by the Na+-L-glutamate carrier. The efflux of L-glutamate was increased by extravesicular K+ or Rb+ but not by Li+, choline+, or Tris+. These findings, together with previous results showing that intravesicular K+ or Rb+ increased L-glutamate uptake and that a K+ gradient energized the concentrative uptake of the acidic amino acid in the absence of other gradients, provide evidence consistent with the hypothesis that the co-transport of Na+-L-glutamate is coupled to the transmembrane flux of K+. 相似文献
16.
Annual egg production was determined for Artemia monica in Mono Lake, California, from 1983 to 1987. Annual oviparous (overwintering cyst) production was 3 and 7 million cysts m–2 yr–1 in 1986 and 1987, respectively, as measured by in situ sediment traps. Cyst production for the entire five year period was calculated using Artemia census data and inter-brood duration derived from mixolimnetic temperature. These estimates ranged from 2 to 5 million cysts m–2 yr–1. This method underestimated annual production by 30%, when compared to estimates using sediment traps. Cyst production was similar during 1983–1986 and showed a significant increase in 1987, which was due primarily to a larger reproductive population later in the year. Recruitment into the adult populations of the following spring ranged between 1.4 to 3.2%. Overall abundance of this generation reflected the patterns in annual cyst production. Compensatory effects must operate on the second generation of each year, since summer populations were similar in all years despite differences in cyst production. 相似文献
17.
Dose/dose-rate responses of shrimp larvae to UV-B radiation 总被引:3,自引:0,他引:3
Summary Previous work indicated dose-rate thresholds in the effects of UV-B on the near-surface larvae of three shrimp species. Additional observations suggest that the total dose response varies with dose-rate. Below 0.002 Wm-2
[DNA] irradiance no significant effect is noted in activity, development, or survival. Beyond that dose-rate threshold, shrimp larvae are significantly affected if the total dose exceeds about 85 Jm-2
[DNA]. Predictions cannot be made without both the dose-rate and the dose.These dose/dose-rate thresholds are compared to four-year mean dose/dose-rate solar UV-B irradiances at the experimental site, measured at the surface and calculated for 1 m depth. The probability that the shrimp larvae would receive lethal irradiance is low for the first half of the season of surface occurrence, even with a 44% increase in damaging UV radiation.Contribution No. 1183 from the Department of Oceanography, University of Washington, Seattle, WA 98195, USA 相似文献
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Thomas M. Harmon Kevin A. Fisher Margaret G. McGlynn John Stover Mitchell J. Warren Yu Teng Arne N?veke 《PloS one》2016,11(1)