全文获取类型
收费全文 | 1903篇 |
免费 | 13篇 |
国内免费 | 2篇 |
专业分类
系统科学 | 49篇 |
理论与方法论 | 23篇 |
现状及发展 | 1221篇 |
研究方法 | 99篇 |
综合类 | 448篇 |
自然研究 | 78篇 |
出版年
2020年 | 14篇 |
2018年 | 34篇 |
2017年 | 28篇 |
2016年 | 38篇 |
2015年 | 31篇 |
2014年 | 19篇 |
2013年 | 26篇 |
2012年 | 58篇 |
2011年 | 98篇 |
2010年 | 23篇 |
2009年 | 17篇 |
2008年 | 46篇 |
2007年 | 41篇 |
2006年 | 67篇 |
2005年 | 59篇 |
2004年 | 38篇 |
2003年 | 47篇 |
2002年 | 47篇 |
2001年 | 30篇 |
2000年 | 16篇 |
1999年 | 19篇 |
1992年 | 19篇 |
1991年 | 17篇 |
1985年 | 14篇 |
1984年 | 27篇 |
1983年 | 14篇 |
1982年 | 16篇 |
1981年 | 21篇 |
1979年 | 36篇 |
1978年 | 31篇 |
1977年 | 40篇 |
1976年 | 36篇 |
1975年 | 29篇 |
1974年 | 36篇 |
1973年 | 46篇 |
1972年 | 42篇 |
1971年 | 39篇 |
1970年 | 65篇 |
1969年 | 57篇 |
1968年 | 86篇 |
1967年 | 66篇 |
1966年 | 47篇 |
1965年 | 46篇 |
1964年 | 43篇 |
1963年 | 20篇 |
1962年 | 24篇 |
1961年 | 17篇 |
1959年 | 15篇 |
1958年 | 12篇 |
1957年 | 13篇 |
排序方式: 共有1918条查询结果,搜索用时 31 毫秒
191.
Safety of patients in anesthesia has always been one of the major concerns of the anesthetist. It is clear from studies of safety in general that many accidents and critical incidents occur as the result of latent systemic failures to which a great number of factors contribute (Reason, 1990). An ideal way to approach this problem would be within a systemic framework, such as teleonics, developed by Járos and his co-workers (Cloete, 1999; Járos and Cloete, 1987, 1993). In this framework the events and procedures in anesthesia are considered to be part of a very complex network of process systems (teleons). It is postulated that teleonic uncertainty (telentropy) in this complex network is a factor that might lead to accidents. In a previous paper presented to the World Congress at Toronto in 2000, the principles of teleonics were described in a mathematico symbolic way (Horváth et al., 2000). This paper contains selected examples of application of these principles to the identification of possible systemic causes of accidents in anesthesia. 相似文献
192.
Diana Cholico-González NoemíOrtiz Lara Mario Alberto Sánchez Miranda Ricardo Morales Es-trella Ramiro Escudero García Carlos A.León Patiño 《矿物冶金与材料学报》2021,28(4):603-611
The reduction behavior and metallization degree of magnetite concentrate with agave bagasse were investigated in an inert atmosphere. The effects of temperature, biomass content, and residence time on reduction experiments and metallization degree were investigated by X-ray diffraction and scanning electron microscopy. Compared with other types of biomass, agave bagasse had lower contents of nitrogen, sulfur, and ash. X-ray diffraction analysis showed that the metallization degree improved with increasing temperature and biomass content. Complete metallization was achieved at 1100°C for 30 min with 65:35 and 50:50 ratios of the magnetite concentrate to the agave bagasse. These results demonstrate that agave bagasse promotes the efficient metallization of magnetite concentrate without the external addition of a reducing agent. Therefore, this biomass is a technical suitable alternative to replace fossil fuels in steelmaking. 相似文献
193.
D. Lamošová M. Zeman M. Macková E. Gwinner 《Cellular and molecular life sciences : CMLS》1995,51(9-10):970-975
The chick pineal gland exhibits circadian rhythms in melatonin synthesis under in vivo and in vitro conditions. A daily rhythm of melatonin production was first detectable in pineal glands isolated from chick embryos at embryonic day 16 and incubated under a LD cycle. All pineal glands isolated from 17-day-old and older embryos were rhythmic while no gland isolated at embryonic day 14 and 15 exhibited a daily rhythm in melatonin synthesis. Melatonin production in static cultures of embryonic pineal cells was rhythmic over 48 h if the cells were kept under a LD cycle. When embryonic pineal cells were incubated in constant darkness the rhythm in melatonin production was damped within 48 h. These results suggest that chick pineal cells from embryonic day 16 onwards are photosensitive but that the endogenous component of the melatonin rhythm is not completely developed at that age. A soluble analogue of cAMP stimulated and norepinephrine inhibited melatonin synthesis in cultured embryonic pineal cells. These findings indicate that the stimulatory and inhibitory pathways controlling melatonin synthesis in the mature pineal gland are effective in pineal cells isolated from chick embryos at least 2 days before hatching. 相似文献
194.
A. Komárková I. Bilyk Z. Záhoř V. Czabanova 《Cellular and molecular life sciences : CMLS》1972,28(4):474-476
Zusammenfassung Es wurde festgestellt, dass Calciferol die Stauung von Calcium, Phosphor und Zitronensäure in allen Teilen der Niere verursacht. Parathormon erhöht den Gehalt von Calcium und Zitronensäure in der Niere während einer Stunde. Nach Verabreichung von Calcitonin wurde Verminderung von Calcium in der Cortical-und Medullarzone beobachtet. 相似文献
195.
K. Barnet J. Pekárek J. Švejcar J. Johanovský 《Cellular and molecular life sciences : CMLS》1971,27(2):206-207
Zusammenfassung Supernatanten aus Kulturen überempfindlicher Lymphozyten und dem spezifischen Antigen mit MIF-Aktivität können die Entstehung der Pseudopodien normaler Makrophagen verhindern und zeigen nach längerem Kultivieren zuweilen toxische Eigenschaften. 相似文献
196.
197.
198.
199.
The immunoadjuvant activity of muramyl dipeptide seems to be critically dependent on the type of substitution of the gamma-carboxyl group of the D-isoglutamine residue. Moreover the nonapeptide L-Ala-D-isoGlu-L-lys-D-Ala-(Gly)5-OME also shows a definite effect. 相似文献
200.
C. -H. Becker V. Kolařík Bohumila Lencová 《Cellular and molecular life sciences : CMLS》1982,38(7):856-857
Summary With FESEM the X-ray microanalysis of unstained ultrathin sections (600 Å) free of osmium is possible. Deposits in smooth muscle cells of arteriosclerotic aortae show high calcium-peaks already after 80 sec of measurement. No contamination spots were seen after 11 min of measurement on the same point. 相似文献