全文获取类型
收费全文 | 22298篇 |
免费 | 111篇 |
国内免费 | 252篇 |
专业分类
系统科学 | 413篇 |
丛书文集 | 426篇 |
教育与普及 | 75篇 |
理论与方法论 | 78篇 |
现状及发展 | 8511篇 |
研究方法 | 928篇 |
综合类 | 11647篇 |
自然研究 | 583篇 |
出版年
2014年 | 156篇 |
2013年 | 297篇 |
2012年 | 533篇 |
2011年 | 1118篇 |
2010年 | 385篇 |
2009年 | 370篇 |
2008年 | 607篇 |
2007年 | 712篇 |
2006年 | 688篇 |
2005年 | 614篇 |
2004年 | 482篇 |
2003年 | 375篇 |
2002年 | 407篇 |
2001年 | 612篇 |
2000年 | 687篇 |
1999年 | 472篇 |
1992年 | 351篇 |
1991年 | 303篇 |
1990年 | 301篇 |
1989年 | 280篇 |
1988年 | 248篇 |
1987年 | 284篇 |
1986年 | 254篇 |
1985年 | 340篇 |
1984年 | 297篇 |
1983年 | 214篇 |
1982年 | 222篇 |
1981年 | 207篇 |
1980年 | 254篇 |
1979年 | 558篇 |
1978年 | 450篇 |
1977年 | 481篇 |
1976年 | 364篇 |
1975年 | 435篇 |
1974年 | 574篇 |
1973年 | 473篇 |
1972年 | 451篇 |
1971年 | 552篇 |
1970年 | 693篇 |
1969年 | 555篇 |
1968年 | 527篇 |
1967年 | 579篇 |
1966年 | 493篇 |
1965年 | 366篇 |
1959年 | 219篇 |
1958年 | 306篇 |
1957年 | 250篇 |
1956年 | 178篇 |
1955年 | 195篇 |
1954年 | 182篇 |
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
151.
Summary The biochemical changes in the hemolymph and tissues were followed during regeneration of the optic tentacles of the snailCryptozona ligulata (Pulmonata-Stylommatophora). There is a remarkable increase in total carbohydrates in hemolymph and tissues and glycogen in tissues at the expense of free amino acids and fatty acids. It is clear that ablation of the optic tentacles stimulates carbohydrate synthesis through glyconeogenic routes. The optic tentacles regenerate completely in 18–21 days. 相似文献
152.
V. Lattanzio V. V. Bianco D. Lafiandra 《Cellular and molecular life sciences : CMLS》1982,38(7):789-790
Summary A HPLC assay for L-Dopa, convicine, and vicine in broad-bean extracts has been developed. The distribution of these compounds in the different organs of the plant has been studied, especially in the seeds, where their presence may cause favism if the beans are used as food.Work supported by C.N.R. through Progetto Finalizzato Miglioramento delle produzioni vegetali per fini alimentari ed industriali mediante interventi genetici. Sottogrogetto leguminose da granella. Paper No. 200. 相似文献
153.
Summary Synthetic 3-methylcyclohex-3-en-1-one, or 3,3-MCH, decreased by 77% the flight aggregation ofDendroctonus pseudotsugae (Scolytidae) to sticky traps containing attractant (frontalin, -pinene, and resin). However, windthrown trees were protected by 3,3-MCH much less than is known to occur with the isomer 3,2-MCH.This research was supported in part by NSF grants BMS 72-02522 and DEB 77-11361 and the O.S.U. School of Forestry. We thank the administration of the Siuslaw National Forest for study sites, and Dr L.M. Libbey for GC/MS of 3,3-MCH. Oregon State University Ag. Exp. Sta. Tech. Paper No. 4313. 相似文献
154.
Three acidic polysaccharide (AP) fractions and the prostaglandin-like substances (PLS) isolated from P. acnes were investigated regarding their chemotactic activities on polymorphonuclear leukocytes. Both AP's and PLS induced a significant chemotatic response, which suggests their involvement in inflammatory acne vulgaris. 相似文献
155.
Suppressor cell induction can be demonstrated during antigen specific blastogenesis by using the same methods which have shown induction of suppressor cells by Con A. Since suppressor cells are rapidly generated during antigen specific blastogenesis, they must regulate the final level of blastogenesis induced during the seven day in vitro incubation. 相似文献
156.
Summary A rotator culture method is described which provides a continuous flow of oxygenating gas to cultures in rotating bottles. The system maintains constant O2 and CO2 levels in the culture medium throughout the incubation period. It also provides a more stable pH than systems with sealed culture bottles.Acknowledgments. We would like to thank Mr B. Secker, Mr C. Hellon and Mr S. J. Ellis, of the Physiological Laboratory workshop, for constructing the rotator apparatus. We also thank the Medical Research Council, London, for financial support for the project. 相似文献
157.
158.
159.
K. Mašek M. Zaoral J. Ježek V. Krchňák 《Cellular and molecular life sciences : CMLS》1979,35(10):1397-1398
Summary The immunoadjuvant activity of muramyl dipeptide seems to be critically dependent on the type of substitution of the -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
160.
Rat pituitary MAO activity was reduced by constant darkness and by additions of melatonin in vitro and was increased by constant light and by pinealectomy. Hypothalamic MAO activity followed the same pattern but was less dramatically affected. The data suggest that MAO may be a target enzyme for melatonin. 相似文献