全文获取类型
收费全文 | 33438篇 |
免费 | 144篇 |
国内免费 | 112篇 |
专业分类
系统科学 | 306篇 |
丛书文集 | 526篇 |
教育与普及 | 71篇 |
理论与方法论 | 155篇 |
现状及发展 | 14933篇 |
研究方法 | 1309篇 |
综合类 | 15976篇 |
自然研究 | 418篇 |
出版年
2013年 | 206篇 |
2012年 | 539篇 |
2011年 | 971篇 |
2010年 | 162篇 |
2008年 | 492篇 |
2007年 | 535篇 |
2006年 | 596篇 |
2005年 | 754篇 |
2004年 | 1149篇 |
2003年 | 979篇 |
2002年 | 654篇 |
2001年 | 978篇 |
2000年 | 999篇 |
1999年 | 669篇 |
1992年 | 540篇 |
1991年 | 443篇 |
1990年 | 474篇 |
1989年 | 465篇 |
1988年 | 412篇 |
1987年 | 449篇 |
1986年 | 521篇 |
1985年 | 595篇 |
1984年 | 482篇 |
1983年 | 410篇 |
1982年 | 364篇 |
1981年 | 383篇 |
1980年 | 438篇 |
1979年 | 1069篇 |
1978年 | 849篇 |
1977年 | 816篇 |
1976年 | 621篇 |
1975年 | 716篇 |
1974年 | 1001篇 |
1973年 | 844篇 |
1972年 | 868篇 |
1971年 | 1035篇 |
1970年 | 1314篇 |
1969年 | 997篇 |
1968年 | 905篇 |
1967年 | 980篇 |
1966年 | 812篇 |
1965年 | 635篇 |
1964年 | 179篇 |
1959年 | 324篇 |
1958年 | 554篇 |
1957年 | 418篇 |
1956年 | 347篇 |
1955年 | 319篇 |
1954年 | 321篇 |
1948年 | 239篇 |
排序方式: 共有10000条查询结果,搜索用时 758 毫秒
201.
In vivo studies indicated that the primary effects of E. coli endotoxin on hepatic clearance of sulfobromophthalein were at the excretory level. Newborns were more sensitive to the LPS than older animals. 相似文献
202.
The influence from carotid baroreceptors on portal immuno-reactive glucagon and insulin levels and on arterial plasma glucose concentration was studied in vagotomized cats by sectioning of the sinus nerves. Such a complete elimination of the afferent baroreceptor discharge caused a prompt and pronounced increase in the glucose and glucagon levels, whereas the insulin concentration significantly decreased. The role of vascular barorecptors in the hyperglycemic response to hemorrhage is discussed. 相似文献
203.
Incorporation of 32P into adrenal mitochondrial phospholipids (PL) incrased in ACTH-treated rats, but it decreased in diabetics, inspite of the fact that these animals showed adrenal overacity. Since diabetics did not show increased 11 beta-hydroxylation. as opposed to ACTH-treated rats, it is suggested that the stimulation of this enzyme activity by exogenous ACTH is related to an increased turnover of PL at the mitochondrial membrane. The process is impaired in diabetics and prevents the stimulation of 11 beta-hydroxylation. 相似文献
204.
205.
C. Hegyvary 《Cellular and molecular life sciences : CMLS》1977,33(10):1280-1281
Summary Aldosterone (15 g BID) and methylprednisolone (8 mg QD) administration to female guinea-pigs augmented both the total and the specific activity of NaK-ATPase but not the activity of adenylate cyclase in the cardiac sarcolemma. The rise in NaK-ATPase was due to increase in the number of enzyme molecules; catalytic activity and ouabain-sensitivity of individual molecules did not change.Acknowledgments. This work was supported by grant 1 R01 HL16611 from the National Heart and Lung Institute of the National Institutes of Health, United States Public Health Service. I thank Mr Kooil Kang for his excellent technical assistance. 相似文献
206.
Summary A convenient one-step procedure, based upon the tyrosinase co-oxidation of dopa and cysteine, is reported for the synthesis of 5-S-cysteinyldopa (I) in 74% yield. Secondary products of the reaction turned out to be 2-S-cysteinyldopa (II, 14%), 2,5-S, S-dicysteinyldopa (IV, 5%), and the hitherto unknown 6-S-cysteinyldopa (III, 1%).The generic term cysteinyldopa is proposed to designate the various cotechol amino-acids arising from addition of cysteine to dopaquinone.This work was supported in part by a grant from Consiglio Nazionale delle Ricerche, Roma. 相似文献
207.
Summary N-(5-Phosphopyridoxyl)-4-aminobutyric acid, a stable adduct of pyridoxal phosphate and 4-aminobutyric acid, has been shown to be a potent inhibitor of rat brain 4-aminobutyric acid aminotransferase (GABA-T) with a Ki of 1.4 M.Acknowledgments. This work was supported in part by the United Parkinson Foundation, l'Association Canadienne l'Ataxie de Friedreich, and the Medical Research Council of Canada. 相似文献
208.
C. Petter 《Cellular and molecular life sciences : CMLS》1977,33(10):1384-1386
Summary Mouse foetuses were treated by Thalidomide on days 11–12 in order to verify whether the drug would induce blood abnormalities leading to circulatory troubles. About 18% of the treated foetuses showed both severe limb haemorrhages on day 14, and obvious alterations of the nucleated red blood cells of vitelline origin. These blood abnormalities, occurring suddenly during the well-known critical stage of foetal development, could be responsible for circulatory blocks leading to necrosis. 相似文献
209.
Summary Unambiguous assignment of the1H-NMR. resonances due to the hydrogen atoms in the -position of homoserine indicates that the hydrogen which is exchanged and removed in the cystathionine--synthase catalyzed reactions holds the pro-R configuration. 相似文献
210.
Summary RIA of ecdysones are made on nymphal extracts ofPisaura mirabilis during the intermoulting cycle. The hormone level is low during exuviation and the greatest part of the intermoulting period but increases notably before and after ecdysis. The main hormonal peak or pre-ecdysial peak is due to -ecdysone, characterized by combined TLC/RIA.Acknowledgment. We wish to thank Dr M. Hirn for his help during the manipulations and J. Britton who has translated the text into English. 相似文献