Author Keywords: behaviour; Colubridae; ecology; Masticophis flagellum; radiotelemetry; Reptilia; Serpentes; temperature; thermoregulation 相似文献
全文获取类型
收费全文 | 10704篇 |
免费 | 1073篇 |
国内免费 | 1540篇 |
出版年
2024年 | 34篇 |
2023年 | 163篇 |
2022年 | 156篇 |
2021年 | 254篇 |
2020年 | 411篇 |
2019年 | 418篇 |
2018年 | 355篇 |
2017年 | 418篇 |
2016年 | 407篇 |
2015年 | 466篇 |
2014年 | 509篇 |
2013年 | 777篇 |
2012年 | 479篇 |
2011年 | 459篇 |
2010年 | 431篇 |
2009年 | 539篇 |
2008年 | 567篇 |
2007年 | 575篇 |
2006年 | 512篇 |
2005年 | 443篇 |
2004年 | 397篇 |
2003年 | 333篇 |
2002年 | 322篇 |
2001年 | 313篇 |
2000年 | 300篇 |
1999年 | 255篇 |
1998年 | 214篇 |
1997年 | 229篇 |
1996年 | 211篇 |
1995年 | 195篇 |
1994年 | 193篇 |
1993年 | 209篇 |
1992年 | 164篇 |
1991年 | 142篇 |
1990年 | 118篇 |
1989年 | 145篇 |
1988年 | 111篇 |
1987年 | 107篇 |
1986年 | 104篇 |
1985年 | 134篇 |
1984年 | 128篇 |
1983年 | 106篇 |
1982年 | 91篇 |
1981年 | 86篇 |
1980年 | 95篇 |
1979年 | 66篇 |
1978年 | 51篇 |
1977年 | 39篇 |
1976年 | 32篇 |
1973年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
131.
Notonecta unifasciata Guerin eggs maintained at different stages of embryonic development in water at variable temperatures (2.2–25.6 °C) and for
periods of 4–12 weeks revealed maximum viability (>80 %) at the highest temperature. However, optimum nondevelopmental viability
was at 14.4 °C with eight-day-old embryos (>35 %). Short term (4 weeks) storage at 14.4 °C significantly increased egg viability.
Survival was poor (<20 %) at the 2 lowest temperatures. Eggs held at 14.4 °C for 12 weeks and sustainingca. 50 % mortality, may be a practical procedure for biological control.
相似文献
132.
133.
Simon Folkard 《Chronobiology international》1989,6(1):55-64
This paper advocates the use of a pragmatic approach to the problem of masking in real-life situations involving an abrupt change in the timing of sleep, i.e. shiftwork and “jet-lag” situations. Although “pure” chronobiological research has pointed to the importance of taking masking effects into account, the techniques that it has provided for doing so are extremely difficult to apply in real-life situations. The approach advocated here is based on Wever's pioneering work, and involves estimating the normative endogenous and exogenous components of the circadian rhythm in body temperature. These estimates are then used to: (a) simulate the results of shiftwork studies; and (b) to “remove” the exogenous component in “jet-lag” studies to allow analysis of the estimated endogenous component. The simulated curves obtained cross-correlated extremely highly with published night-shift temperature curves, while the “removal” of the exogenous component resulted in very similar findings to those obtained in temporal isolation studies. It is concluded that this pragmatic approach to masking may prove extremely useful in interpreting the results of field studies of shiftwork and “jet-lag”. 相似文献
134.
The influence of soil temperature and moisture on Meloidogyne incognita (Kofoid and White) Chitwood was examined in relation to hatching and survival of second-stage juveniles (J2). Nematodes were cultured on cotton (Gossypium hirsutum L. cv. Acala SJ2) under field conditions to provide populations similar to those found in the field in late autumn. Egg masses were placed in a temperature range (9-12 C and 21 C), and hatch was measured over a period equivalent to 20 degree days > 10 C (DD10). Hatch occurred below the reported 18 C activity threshold, was restricted below 12 C, and was inhibited below 10 C. Soil moisture influence on hatch was measured by placing egg masses in Hesperia sandy loam and subjecting them to suction pressures ranging from -1.1 bars to -4 .5 bars. Suction potentials of less than -2 bars reduced hatch and less than -3 bars inhibited hatch. J2 were placed in sandy loam soil with soil moisture near field capacity, and their motility was measured over a period of 500 DD10. In the absence of a host, more than 90% of J2 became nonmotile over this period. 相似文献
135.
In laboratory thermal gradients, newly hatched infective juveniles of the plant-parasitic root-knot nematode Meloidogyne incognita migrated toward a preferred temperature that was several degrees above the temperature to which they were acclimated. After shifting egg masses to a new temperature, the preferred temperature was reset in less than a day. Possible functions of this type of thermotaxis are discussed, including the use of thermal gradients around plant roots to locate hosts and to maintain a relatively straight path while ranging in the absence of other cues (a collimating stimulus). 相似文献
136.
Geoffrey A. Hammerson 《Journal of thermal biology》1989,14(4):219-224
1. 1.|Body temperature (Tb) and activity of the snake Masticophis flagellum were studied by radiotelemetry in an outdoor enclosure.
2. 2.|Mean diurnal Tb varied little over a wide range of weather conditions, but weather variation was accompanied by major changes in sun exposure and in the timing and duration of activity.
3. 3.|Recently fed snakes reduced activity and exhibited neither a thermophilic response nor increased precision of thermoregulation compared to fasting snakes.
137.
Storage of apple fruits ( Pyrus malus L. cv. Golden Delicious) at different temperatures (0, 12 and 35°C) markedly altered the pattern of water freezing in the seeds. Higher temperatures of storage brought about a shift from the sequential to the discontinuous type of freezing in seeds, the low temperature exotherm (LTE) being much more pronounced than the high temperature one (HTE). The occurrence of LTE was highly correlated with embryo death. Fruit storage at higher temperatures also caused a decrease in the threshold super cooling temperature of seeds and of naked embryos, removed from the seed coat and endosperm. The decrease was less pronounced in naked embryos than in intact seeds. The results presented show that the frost resistance of apple seeds relies mainly on the supercooling ability of the embryos and is increased by the presence of seed coat and endosperm. The broad peak of the LTE indicates that, in contrast with other seeds and many super cooling organs, massive ice nucleation in apple seeds occurs within the embryo tissues and that extra organ freezing seems to be of less importance. Therefore, the increased super cooling ability of apple seeds, isolated from fruits stored at higher temperatures, seems to rely on those seed properties that protect embryo cells against heterogeneous ice nucleation. 相似文献
138.
Copper deficiency in wheat ( Triticum aestivum L. cv. Nazareno Stramppeli) markedly affects photosynthetic activity. Flag leaves of copper-deficient plants showed a 50% reduction of the photosynthetic rate expressed as mg CO2 dm−2 h−1 . The activities of PSI and PSII, determined for isolated chloroplasts, as well as fluorescence measurements on intact leaves of copper-deficient plants, indicated a low activity of photosynthetic electron transport. Ribulose bisphosphate carboxylase/oxygenase (Rubisco) activity was not affected by copper deficiency but copper deficiency affected the chloroplast ultrastructure, especially at the level of grana, where a disorganization of thylakoids is evident. 相似文献
139.
Instantaneous rates of (soil + root) respiration were measured periodically during grain filling in sunflower crops that were i) irrigated at weekly intervals and ii) subjected to water stress for the last 25 days of the 40-day grain filling period. Daily (soil + root) respiration was calculated using instantaneous respiration rates, an empirically determined temperature response function, and diurnal records of soil temperature. Daily soil respiration was estimated using empirically determined functions linking soil respiration to soil temperature and water content. Between anthesis and maturity, daily root respiration of the irrigated crop dropped by about one half from ca. 1.8 g C m-2 d-1, exhibiting a strong association with daily crop gross photosynthesis. Water stress brought about a rapid decrease in root respiration, which fell to about 0.1 g C m-2 d-1 at maturity. Root respiration during grain filling was 46 and 30 g C m-2 for irrigated and stressed crops, respectively. 相似文献
140.
Tryptophan (Trp) surface topography of the red- and far-red-absorbing forms of phytochrome (Pr, Pfr) ofAvena sativa L. has been investigated by analyzing quenching of the two components of Trp fluorescence decay, in order to understand the
differences in the two forms at the molecular level. Stern-Volmer kinetic analysis of the quenching data for two cationic
surface quenchers, Cs+ and Tl+, showed strong quenching of the short component of the Pr fluorescence (Stern-Volmer constants,K
sv
, 27.2 and 21.4 M−1, respectively) relative to that of Pfr fluorescenceK
sv
, 10.4 and 12.3 M−1, respectively). The long component of the Trp fluorescence was quenched differentially by Cs+ and Tl+, withK
sv
of 9.0 and 19.8 M−1, respectively, for the Pr fluorescence andK
sv
of 13.7 and 8.7 M−1, respectively, for the Pfr fluorescence. The results indicate that the phytochrome Trp residues with short fluorescence lifetime
are more accessible to the cationic surface quenchers than those with long fluorescence lifetime. The data, taken together
with our earlier study (Singh et al. 1988, Biochim, Biophys. Acta936, 395–405), indicate that most, if not all the ten Trp residues of phytochrome, are fluorescent and exist in distinct groups
differing in their topography and microenvironment, and the peptide segment containing Trp-774 and Trp-778 within the 55-kilodalton
C-terminal domain of phytochrome also undergoes a subtle alteration in its surface topography during Pr→Pfr phototransformation.
This paper is dedicated to Professor Hans Mohr in commemoration of his 60th birthday 相似文献