全文获取类型
收费全文 | 19453篇 |
免费 | 45篇 |
国内免费 | 48篇 |
专业分类
系统科学 | 144篇 |
丛书文集 | 285篇 |
教育与普及 | 36篇 |
理论与方法论 | 76篇 |
现状及发展 | 9334篇 |
研究方法 | 781篇 |
综合类 | 8693篇 |
自然研究 | 197篇 |
出版年
2012年 | 219篇 |
2011年 | 427篇 |
2009年 | 88篇 |
2008年 | 268篇 |
2007年 | 290篇 |
2006年 | 323篇 |
2005年 | 314篇 |
2004年 | 437篇 |
2003年 | 304篇 |
2002年 | 300篇 |
2001年 | 554篇 |
2000年 | 507篇 |
1999年 | 367篇 |
1994年 | 87篇 |
1992年 | 350篇 |
1991年 | 255篇 |
1990年 | 274篇 |
1989年 | 265篇 |
1988年 | 222篇 |
1987年 | 262篇 |
1986年 | 310篇 |
1985年 | 370篇 |
1984年 | 283篇 |
1983年 | 249篇 |
1982年 | 233篇 |
1981年 | 240篇 |
1980年 | 259篇 |
1979年 | 648篇 |
1978年 | 532篇 |
1977年 | 508篇 |
1976年 | 390篇 |
1975年 | 456篇 |
1974年 | 649篇 |
1973年 | 523篇 |
1972年 | 538篇 |
1971年 | 632篇 |
1970年 | 802篇 |
1969年 | 623篇 |
1968年 | 625篇 |
1967年 | 622篇 |
1966年 | 523篇 |
1965年 | 437篇 |
1964年 | 146篇 |
1959年 | 214篇 |
1958年 | 373篇 |
1957年 | 280篇 |
1956年 | 226篇 |
1955年 | 218篇 |
1954年 | 213篇 |
1948年 | 156篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
141.
G. D. Ledney H. M. Gelston Jr S. R. Weinberg E. D. Exum 《Cellular and molecular life sciences : CMLS》1982,38(10):1228-1230
Summary Wound trauma-induced survival from radiation may be related to increased mitosis in hematopoietic cells. This is supported by the cell cycle-dependent drug hydroxyurea, which 1. blocked survival of wounded mice injected 2 or 3 days after 900 rad and 2. reduced the number of endogenous CFU-s in wounded mice injected shortly before 700 rad.Supported by the Armed Forces Radiobiology Research Institute, Defense Nuclear Agency, under Research Work Unit MJ00018. Views presented in this paper are those of the authors; no endorsement by the Defense Nuclear Agency has been given or should be inferred.Research was conducted according to the principles enunciated in the Guide for the Care and Use of Laboratory Animals prepared by the Institute of Laboratory Research, National Research Council. 相似文献
142.
Structure,biosynthesis and functions of glycoprotein glycans 总被引:14,自引:0,他引:14
Eric G. Berger Eckhart Buddecke Johannis P. Kamerling Akira Kobata James C. Paulson Johannes F. G. Vliegenthart 《Cellular and molecular life sciences : CMLS》1982,38(10):1129-1162
Since the pioneering work on structure and function of heteroglycans compiled in the classical books edited by A. Gottschalk in 19721, there have been several promising developments in glycoconjugate research, as reviewed in this article.In Part 1, contributed by A. Kobata, current knowledge on heteroglycan structures is presented and representative examples taken from higher organisms are given. Part 2, written by J. F. G. Vliegenthart and J. P. Kamerling, covers the most important achievements in methodology: procedures to obtain pure glycans and to analyze their structures. Part 3, contributed by J. Paulson, is devoted to biosynthesis of glycans now describable as pathways since several of the glycosyltransferases have been isolated and analyzed for specificity. In Part 4, contributed by E. Buddecke, current knowledge on functional roles of glycans is presented. It will become apparent that the prerequisite for valid work either in biosynthetic or functional context depends on solid structural information. This is particularly true whenever glycosyltransferase reaction products are being analyzed, or glycans involved in biological functions are investigated. Although in past years, a great deal of important knowledge has been gathered by use of crude glycosidase or glycosyltransferase activities (a notable example is found in reference 2), one may now postulate that glycans implicated in biological reactions should be thoroughly analyzed.This review may familiarize newcomers with the field of glycoconjugate research with special emphasis on glycoprotein glycans. Glycolipids are not included in this article as they have recently been reviewed by S. I. Hakomori3. The reader is also referred to several excellent monographs4,5 and the Proceedings of the Glycoconjugate Symposia held biannually6–8. 相似文献
143.
Summary The flavoprotein ferredoxin reductase catalyzed the oxidation of styrene to styrene oxide in the presence of NADPH. This reaction was inhibited by the addition of catalase and superoxide dismutase. The addition of the nonheme iron protein ferredoxin partially inhibited styrene oxidation. H2O2 was also able to catalyze this reaction when added to the enzyme in the absence of NADPH.Acknowledgments. This work was supported by C.N.R. (National Research Council), Rome, Italy contract No. 79.03197.04. 相似文献
144.
G. Zamboni E. Perez P. L. Parmeggiani 《Cellular and molecular life sciences : CMLS》1982,38(10):1188-1189
Summary In rats adapted to a 1212 h light-dark (LD) schedule, cyclic AMP concentration in the preoptic region showed a L minimum and D maximum. No significant fluctuations were observed in the parietal cortex.Supported by grant No. 79.01946.04 awarded by the National Research Council (CNR), Rome, Italy. 相似文献
145.
146.
Summary Spectroscopic evidence shows that the flavylium cation (1) undergoes hydroxylation to form the carbinol base (2) and can also deprotonate to form the anhydro (quinonemethane) bases (3a and3b). The anhydro bases hydrate to the carbinol base. The carbinol base above pH 6, or the ionzed carbinol base (2a), undergoes diring fission to produce the cischalcone (4).The editors do not hold themselves responsible for the opinions expressed in the authors' brief reports. — Les auteurs sont seuls responsables des opinions exprimées das ces brèves communications. — Für die Kurzmitteilungen ist ausschliesslich der Autor verantwortlich. — Per le brevi comunicazioni è responsabile solo l'autore. — ë . — Solo los autores son responsables de las opiniones expresadas en estas comunicationes breves.Acknowledgment. This research was supported by a grant from the Welch Food Co., Westfield, NY. 相似文献
147.
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
148.
T. Nakajima T. Yasuhara G. Falconieri Erspamer J. Visser 《Cellular and molecular life sciences : CMLS》1979,35(9):1133-1133
Summary Methanol extracts of the skin of the South African amphibians belonging to the genusHeleophryne (H. purcelli purcelli, H. purcelli depressa, H. purcelli orientalis, H. natalensis) contain large amounts (20–500 g/g fresh tissue) of Hyp3-bradykinin.Supported by grants from the Consiglio Nazionale delle Ricerche, Italy, and from the Ministry of Education, Japan. 相似文献
149.
Summary Roots ofVicia faba L. immersed in a buffer solution were found to release esterases into the environment. The substrate -naphthylacetate was taken up by the roots and degraded, the hydrolysis products being released back into the surrounding medium. 相似文献
150.
Summary In a group of 5 women taking oral contraceptives, the concentration of polymorphonuclear leucocytes along the gingival margin and the activities of cathepsin D, -glucuronidase and elastase were found to increase significantly during the intermenstrual phases.Supported by grant 3.604.075 of the Swiss National Fund for scientific Research. The authors thank Dr M. Baggiolini and Prof. A. Linder for the helpful advices. 相似文献