全文获取类型
收费全文 | 4180篇 |
免费 | 372篇 |
国内免费 | 2篇 |
出版年
2022年 | 16篇 |
2021年 | 58篇 |
2020年 | 41篇 |
2019年 | 58篇 |
2018年 | 94篇 |
2017年 | 65篇 |
2016年 | 135篇 |
2015年 | 203篇 |
2014年 | 210篇 |
2013年 | 245篇 |
2012年 | 356篇 |
2011年 | 317篇 |
2010年 | 202篇 |
2009年 | 196篇 |
2008年 | 240篇 |
2007年 | 278篇 |
2006年 | 220篇 |
2005年 | 211篇 |
2004年 | 179篇 |
2003年 | 167篇 |
2002年 | 177篇 |
2001年 | 67篇 |
2000年 | 47篇 |
1999年 | 47篇 |
1998年 | 37篇 |
1997年 | 39篇 |
1996年 | 27篇 |
1995年 | 22篇 |
1994年 | 25篇 |
1993年 | 31篇 |
1992年 | 41篇 |
1991年 | 40篇 |
1990年 | 26篇 |
1989年 | 20篇 |
1988年 | 18篇 |
1987年 | 13篇 |
1985年 | 25篇 |
1984年 | 25篇 |
1983年 | 13篇 |
1982年 | 19篇 |
1980年 | 14篇 |
1978年 | 12篇 |
1977年 | 12篇 |
1976年 | 14篇 |
1975年 | 16篇 |
1974年 | 16篇 |
1973年 | 18篇 |
1972年 | 17篇 |
1971年 | 14篇 |
1968年 | 15篇 |
排序方式: 共有4554条查询结果,搜索用时 31 毫秒
1.
2.
T. Friedel F. G. Barth 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(3):223-233
Spiders can use air particle movements to localize moving prey. We studied the responses of 32 wind-sensitive interneurones
in the hunting spider Cupiennius salei to prey stimuli.
Stimulation with a tethered flying fly or with artificial air pulses activated plurisegmental interneurones that responded
to changes in air movement velocity and were thus well suited to represent the highly fluctuating air stream typical of prey
stimuli. In most interneurones (n = 18) the responses to the stimulation of different legs were not significantly different from each other.
Different interneurones had different response characteristics and their latencies largely overlapped suggesting that there
is parallel processing of the signals by populations of interneurones with different response characteristics.
In two interneurones the number of spikes and the spiking pattern elicited by stimulation of each of the eight legs markedly
differed depending on the leg stimulated. These neurones may play an important role in directional information processing.
Stimulation of the adjacent legs from front to back or from back to front revealed two interneurones sensitive to the direction
of successive stimulation of the legs. These neurones may be able to detect the motion of an air movement source in a preferred
direction and thus act as nearfield motion detectors to localize a moving prey item.
Accepted: 28 September 1996 相似文献
3.
The energetics of middle-distance running 总被引:2,自引:0,他引:2
J. R. Lacour S. Padilla-Magunacelaya J. C. Barthélémy D. Dormois 《European journal of applied physiology and occupational physiology》1990,60(1):38-43
In order to assess the relative contribution of aerobic processes to running velocity (v), 27 male athletes were selected on the basis of their middle-distance performances over 800, 1500, 3000 or 5000 m, during the 1987 track season. To be selected for study, the average running velocity (v) corresponding to their performances had to be superior to 90% of the best French v of the season. Maximum O2 consumption (VO2max) and energy cost of running (C) had been measured within the 2 months preceding the track season, which, together with oxygen consumption at rest (VO2rest) allowed us to calculate the maximal v that could be sustained under aerobic conditions: vamax = (VO2max - VO2rest) x C-1. The treadmill running v corresponding to a blood lactate of 4 mmol.l-1 (vla4), was also calculated. In the whole group, C was significantly related to height (r = -0.43; P less than 0.03). Neither C nor VO2max (with, in this case, the exception of the 3000 m athletes) were correlated to v. On the other hand, vamax was significantly correlated to v over distances longer than 800 m. These v were also correlated to vla4. However vla4 occurred at 87.5% SD 3.3% of vamax, this relationship was interpreted as being an expression of the correlation between vamax and v. Calculation of vamax provided a useful means of analysing the performances. At the level of achievement studied, v sustained over 3000 m corresponded to vamax.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
4.
Esther Jiménez Susana Delgado Antonio Maldonado Rebeca Arroyo Mar Albújar Natalia García Manel Jariod Leonides Fernández Adolfo Gómez Juan M Rodríguez 《BMC microbiology》2008,8(1):143
Background
Breast milk is an important source of staphylococci and other bacterial groups to the infant gut. The objective of this work was to analyse the bacterial diversity in feces of breast-fed infants and to compare it with that of formula-fed ones. A total of 23 women and their respective infants (16 breast-fed and 7 formula-fed) participated in the study. The 16 women and their infants provided a sample of breast milk and feces, respectively, at days 7, 14, and 35. The samples were plated onto different culture media. Staphylococcal and enterococcal isolates were submitted to genetic profiling and to a characterization scheme, including detection of potential virulence traits and sensitivity to antibiotics. 相似文献5.
6.
7.
A simple radioassay of acetate thiokinase 总被引:2,自引:0,他引:2
8.
9.
Fredrik Barth 《American anthropologist》1995,97(4):806-807
Book reviewed in this article:
Images of Power: Balinese Paintings Made for Gregory Bateson and Margaret Mead . Hildred Geertz. 相似文献
Images of Power: Balinese Paintings Made for Gregory Bateson and Margaret Mead . Hildred Geertz. 相似文献
10.
Electrocardiogram (ECG) analysis was performed in three human divers studied at 21 and 23.5 ATA while they breathed various gas mixtures containing H2 and/or He (COMEX HYDRA IX experiment) and in five dogs exposed to 91 ATA of He-O2 or He-N2-O2. In all cases, the O2 partial pressure was slightly higher than its physiological value. These human and animal studies reveal that elevated pressure of different inert gases did not change the resting heart rate or its respiratory fluctuation. However, the T wave amplitude increased in proportion to the gas density in the three divers; this was also found in four of the five dogs studied. Changes in peak T wave configurations were also observed in the dog experiments. Positional changes in QRS or T vectors cannot explain these T wave changes. 相似文献