全文获取类型
收费全文 | 2969篇 |
免费 | 18篇 |
国内免费 | 5篇 |
专业分类
系统科学 | 46篇 |
理论与方法论 | 55篇 |
现状及发展 | 1738篇 |
研究方法 | 223篇 |
综合类 | 870篇 |
自然研究 | 60篇 |
出版年
2020年 | 14篇 |
2018年 | 50篇 |
2017年 | 38篇 |
2016年 | 47篇 |
2015年 | 32篇 |
2014年 | 39篇 |
2013年 | 40篇 |
2012年 | 112篇 |
2011年 | 164篇 |
2010年 | 63篇 |
2009年 | 23篇 |
2008年 | 103篇 |
2007年 | 86篇 |
2006年 | 104篇 |
2005年 | 103篇 |
2004年 | 95篇 |
2003年 | 82篇 |
2002年 | 87篇 |
2001年 | 56篇 |
2000年 | 39篇 |
1999年 | 38篇 |
1992年 | 24篇 |
1991年 | 21篇 |
1990年 | 28篇 |
1989年 | 16篇 |
1988年 | 17篇 |
1987年 | 30篇 |
1986年 | 18篇 |
1985年 | 26篇 |
1984年 | 27篇 |
1982年 | 29篇 |
1981年 | 18篇 |
1980年 | 31篇 |
1979年 | 83篇 |
1978年 | 69篇 |
1977年 | 91篇 |
1976年 | 21篇 |
1975年 | 37篇 |
1974年 | 95篇 |
1973年 | 81篇 |
1972年 | 102篇 |
1971年 | 72篇 |
1970年 | 88篇 |
1969年 | 94篇 |
1968年 | 68篇 |
1967年 | 91篇 |
1966年 | 76篇 |
1965年 | 57篇 |
1964年 | 16篇 |
1960年 | 11篇 |
排序方式: 共有2992条查询结果,搜索用时 15 毫秒
281.
282.
M Székely 《Experientia》1978,34(1):58-59
During the first days of life 10 microgram i.c.v. 5-HT evoked a primary, short-lasting hyperthermia in kittens and hypothermia in guinea-pigs. In both species, a secondary late hyperthermia occurred that could be prevented by indomethacin pretreatment. 相似文献
283.
A review of the literature suggests that the effects of nitric oxide (NO) on skeletal muscles fibers can be classified in
two groups. In the first, the effects of NO are direct, due to nitrosation or metal nitrosylation of target proteins: depression
of isometric force, shortening velocity of loaded or unloaded contractions, glycolysis and mitochondrial respiration. The
effect on calcium release channels varies, being inhibitory at low and stimulatory at high NO concentrations. The general
consequence of the direct effects of NO is to ‘brake’ the contraction and its associated metabolism. In the second group,
the effects of NO are mediated by cGMP: increase of the shortening velocity of loaded or unloaded contractions, maximal mechanical
power, initial rate of force development, frequency of tetanic fusion, glucose uptake, glycolysis and mitochondrial respiration;
decreases of half relaxation time of tetanus and twitch, twitch time-to-peak, force maintained during unfused tetanus and
of stimulus-associated calcium release. There is negligible effect on maximal force of isometric twitch and tetanus. The general
consequence of cGMP-mediated effects of NO is to improve mechanical and metabolic muscle power, similar to a transformation
of slow-twitch to fast-twitch muscle, an effect that we may summarize as a ‘slow-to-fast’ shift. 相似文献
284.
285.
Sandrine Turcotte Thérèse Laferrière Christine Hamel Alain Breuleux 《Systemic Practice and Action Research》2010,23(4):285-299
Small remote rural schools in Quebec face an ongoing challenge to provide similar quality educational services than bigger
schools. Since 2002, the Remote Network Schools (RNS) initiative afforded schools the opportunity to reinvent their practice
by using online tools to experience collaborative learning activities with other remote schools. Teachers and students experienced
quality learning and demonstrated agency by implementing the RNS in their context. Measures include: diversity of learning
activities, quality of online classroom interactions, changes in teacher beliefs, and shifts in teacher and student roles.
Our results show that it is a viable operating method for such schools and that other schools could contemplate implementing
such innovative practices. 相似文献
286.
287.
Antibodies reacting with 3,5,3',5' tetraiodo-l-tyrosyl-l-tyrosine (I2Tyr-I2Tyr) were elicited in rabbits by immunization with an oxidized yeast conjugate coupled with I2Tyr-I2Tyr. Ion-exchange chromatography was used to purify immunoglobulins, in order to improve the specificity in measurement of I2Tyr-I2Tyr level in patient serum. IgG binding capacity versus I2Tyr-I2Tyr was considerably increased after immunoglobulin purification. 相似文献
288.
Summary The distribution of substance P-like immunoreactivity was studied in the thoracic dorsal root ganglia of the frogRana esculenta by immunohistochemistry. Substance P-like immunoreactivity was contained in approximately 50% of primary sensory neurons. The immunoreactive fibers arising from the cell bodies are collected in small bundles within the ganglia neuropil before entering the central and peripheral roots. 相似文献
289.
290.
In rats undergoing unilateral extirpation of the pelvic ganglion, the adrenergic innervation disappeared on the ipsilateral side of the urinary bladder. It had reappeared after 6--9 weeks. 相似文献