全文获取类型
收费全文 | 577748篇 |
免费 | 63216篇 |
国内免费 | 426篇 |
专业分类
641390篇 |
出版年
2018年 | 4833篇 |
2016年 | 6578篇 |
2015年 | 9143篇 |
2014年 | 10507篇 |
2013年 | 15392篇 |
2012年 | 17058篇 |
2011年 | 17271篇 |
2010年 | 11633篇 |
2009年 | 10651篇 |
2008年 | 15474篇 |
2007年 | 15998篇 |
2006年 | 15013篇 |
2005年 | 14438篇 |
2004年 | 14092篇 |
2003年 | 13672篇 |
2002年 | 13544篇 |
2001年 | 27808篇 |
2000年 | 28110篇 |
1999年 | 21893篇 |
1998年 | 7254篇 |
1997年 | 7663篇 |
1996年 | 7350篇 |
1995年 | 6716篇 |
1994年 | 6655篇 |
1993年 | 6497篇 |
1992年 | 18127篇 |
1991年 | 17764篇 |
1990年 | 17061篇 |
1989年 | 16626篇 |
1988年 | 15375篇 |
1987年 | 14532篇 |
1986年 | 13317篇 |
1985年 | 13400篇 |
1984年 | 10917篇 |
1983年 | 9440篇 |
1982年 | 7093篇 |
1981年 | 6423篇 |
1980年 | 6021篇 |
1979年 | 10472篇 |
1978年 | 7973篇 |
1977年 | 7458篇 |
1976年 | 6838篇 |
1975年 | 7734篇 |
1974年 | 8269篇 |
1973年 | 8092篇 |
1972年 | 7454篇 |
1971年 | 6623篇 |
1970年 | 5979篇 |
1969年 | 5687篇 |
1968年 | 5197篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
The clinical and laboratory findings in seven children with Kawasaki disease are reviewed. Four of the patients had the more complicated course that has characterized the cases diagnosed in North America. This suggests that the benign forms are often mistaken for other febrile illnesses. The patients were two girls and five boys ranging in age from 4 months to 7 years; six were Caucasian and one was a North American Indian. Fever, redness of the oral mucosa, an erythematous or scarlatiniform rash and cervical adenopathy were seen in all; six patients had the characteristic fingertip desquamation and nonexudative conjunctivitis. Cardiac involvement occurred in four patients, two of whom had coronary artery aneurysm or thrombosis. Arthritis or arthralgia was seen in six patients, and aseptic meningitis occurred in four. Of the three patients with jaundice two underwent laparotomy and excision of a hydropic gallbladder; one of them died from Klebsiella pneumoniae sepsis and disseminated intravascular coagulopathy. 相似文献
982.
983.
Subnuclear localization and antitransforming activity of N-myc:beta-galactosidase fusion proteins. 总被引:3,自引:2,他引:1
N-myc expression is under stage- and tissue-specific regulation in mammalian development, but its function is totally unknown. We sought agents to block N-myc activity in order to infer from the effect the possible function of N-myc in the apparently complex processes. As candidates for such agents, we tested fusion genes encoding N-myc:beta-galactosidase fusion proteins for their effects on the formation of transformed foci of rat embryo primary fibroblasts as the result of transfection with N-myc and activated H-ras. One of the gene constructs very efficiently antagonized N-myc activity, as assessed by its effect on focus formation, but did not appreciably affect cell viability. The product of this gene was not only targeted to the nucleus but also accumulated in subnuclear loci which may represent the sites where normal N-myc proteins reside. The occurrence of antagonistic effect at a low stoichiometric ratio suggested that the fusion protein gene competed with the N-myc gene in a fashion analogous to a dominant negative mutation. 相似文献
984.
Urease was immobilized on O-alkylated nylon tubes coated with polyaminated derivatives of starch or dextran. The specific activity of the enzyme coil and the relative stability of the immobilized enzyme, compared with immobilized urease derived from other nylon tube modifications, were enhanced. Also, the nonspecific binding of urease to O-alkylated nylon tubes was virtually eliminated by the coating process. 相似文献
985.
Isolation of Temperature-Sensitive Membrane Mutants of Escherichia coli K-12 总被引:1,自引:1,他引:0 下载免费PDF全文
Johan F. Steenbakkers J. H. F. F. Broekman A. Kerkenaar P. G. De Haan 《Journal of bacteriology》1973,116(2):535-540
Mutants with impaired biosynthesis of unsaturated fatty acids or altered metabolism of the phospholipids were isolated at a rather high frequency from a set of temperature-sensitive lysis mutants. It is suggested that preselection for the lysis phenotype makes it possible to isolate several kinds of mutants affected in the integrity of the cytoplasmic membrane. 相似文献
986.
987.
988.
989.
990.