全文获取类型
收费全文 | 15497篇 |
免费 | 34篇 |
国内免费 | 46篇 |
专业分类
系统科学 | 91篇 |
丛书文集 | 254篇 |
教育与普及 | 32篇 |
理论与方法论 | 73篇 |
现状及发展 | 6286篇 |
研究方法 | 786篇 |
综合类 | 7770篇 |
自然研究 | 285篇 |
出版年
2013年 | 105篇 |
2012年 | 264篇 |
2011年 | 545篇 |
2010年 | 105篇 |
2008年 | 321篇 |
2007年 | 305篇 |
2006年 | 322篇 |
2005年 | 329篇 |
2004年 | 323篇 |
2003年 | 281篇 |
2002年 | 263篇 |
2001年 | 458篇 |
2000年 | 442篇 |
1999年 | 310篇 |
1992年 | 267篇 |
1991年 | 197篇 |
1990年 | 224篇 |
1989年 | 219篇 |
1988年 | 223篇 |
1987年 | 218篇 |
1986年 | 205篇 |
1985年 | 293篇 |
1984年 | 229篇 |
1983年 | 158篇 |
1982年 | 167篇 |
1981年 | 152篇 |
1980年 | 181篇 |
1979年 | 418篇 |
1978年 | 309篇 |
1977年 | 307篇 |
1976年 | 289篇 |
1975年 | 323篇 |
1974年 | 385篇 |
1973年 | 363篇 |
1972年 | 379篇 |
1971年 | 434篇 |
1970年 | 550篇 |
1969年 | 462篇 |
1968年 | 469篇 |
1967年 | 431篇 |
1966年 | 383篇 |
1965年 | 285篇 |
1964年 | 87篇 |
1959年 | 169篇 |
1958年 | 297篇 |
1957年 | 199篇 |
1956年 | 185篇 |
1955年 | 150篇 |
1954年 | 185篇 |
1948年 | 138篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
F. Ramaekers H. Rigter B. E. Leonard 《Cellular and molecular life sciences : CMLS》1977,33(10):1326-1327
Summary Rats homozygous for hypothalamic diabetes insipidus were found to have a significantly higher concentration of membrane-bound polyribosomes thant their heterozygous littermates. There was no difference in the concentration of free polyribosomes. 相似文献
992.
E Ramon-Moliner 《Experientia》1977,33(10):1342-1344
Images with apparently gemmulofugal polarity in the EPL of the olfactory bulb are the result of sectioning, along misleading planes, gemmulopetal synapses containing postsynaptic vesicles. Unless one accepts a bidirectional conduction for chemical synapses, the internal granule cells lack actual gemmulofugal synapses and the neurotransmitter contained on their vesicles must act at non-synaptic membranes. 相似文献
993.
J. A. Izquierdo G. Rabiller E. Borghi S. Costas C. Savini E. Justel 《Cellular and molecular life sciences : CMLS》1979,35(1):73-74
Summary Tryptophan, 5-HT, MAO and 5-HIAA were determined in the first 5 segments of earthworms (Oligochaetae) where the brain and subesophagic ganglions are located. Tranylcypromine (IMAO) decreased MAO activity increasing 5-HT and decreasing 5-HIAA. Motility and survival of worms were disturbed. InAllolobophora species (young worms), parathion fumigation decreased acetylcholinesterase (AChE) activity and increased Trp, 5-HT and 5-HIAA. Motility was diminished after 24 h: it worsened after 72, but returned to normal levels 40/50 days later.Publication of the National Institute of Agrarian Technology (INTA), Argentina.Acknowledgments. We are most grateful to Prof. Zlatko Tomsic (from the Lillo Institute, Tucumán) and to Leticia Alvarado (from INTA) and to Prof. Mirta P. de Matosian for earthworm classification. 相似文献
994.
Summary A simple and inexpensive modification of the Kopf model 900 small animal stereotaxic instrument allows it to be used temporarily as a precision polyacrylamide slab gel slicer.Supported by the Alfred P. Sloan Foundation. 相似文献
995.
E. Ch. Herrmann 《Cellular and molecular life sciences : CMLS》1979,35(9):1263-1264
Summary The simple theoretical criterion for chemical carcinogenicity based on the average quasi-valence number is discussed and shown to be inappropriate as a reliable indicator of carcinogenicity of any organic compound.I thank very much Dr R. Gordon for reading the English text and also for a stimulating discussion. 相似文献
996.
A comparison has been made between the separation of nucleated cells from human bone marrow aspirates by high mol. wt polymers and the buffy coat techniques. 相似文献
997.
Modification of polymorphonuclear neutrophils by a series of maleimide derivatives with various degrees of lipophilicity and hydrophilicity indicated that hydrophilic reagents had little effect on chemotaxis, whereas the degree of the inhibitory effect of lipophilic reagents on the chemotaxis was parallel to the degree of their lipophilicity. 相似文献
998.
In the isolated perfused rat pancreas, omission of extracellular phosphate (H2PO-4) significantly reduces the insulin secretion in response to 16.7 mM glucose. 相似文献
999.
Riassunto Il metodo autografico è stato impiegato per la valutazione della distribuzione dei germi. Sezioni sagittali complete di topi precedentemente infettati sono state incubate e i germi vivi sono stati rivelati mediante colorazione vitale con trifeniltetrazolio. Le risultanti mappe dettagliate della distribuzione batterica permettono di penetrare il meccanismo dei processi difensivi dell'ospite e le proprietà invasive del germe. 相似文献
1000.
E. Kovács 《Cellular and molecular life sciences : CMLS》1970,26(12):1396-1397
Zusammenfassung Die Infektion von Schimmelpilzen,C. albicans, durch Polyomavirus mit isolierter Polyoma-DNS und die aktivierende Wirkung von DMSO werden beschrieben.
Supported by a grant of the National Cancer Institute of Canada.
The assistance of Mr. G.Kolompár and B.Bucz during these assays is gratefully acknowledged. 相似文献
Supported by a grant of the National Cancer Institute of Canada.
The assistance of Mr. G.Kolompár and B.Bucz during these assays is gratefully acknowledged. 相似文献