全文获取类型
收费全文 | 424731篇 |
免费 | 47811篇 |
国内免费 | 164篇 |
专业分类
472706篇 |
出版年
2018年 | 3902篇 |
2016年 | 5279篇 |
2015年 | 6897篇 |
2014年 | 8143篇 |
2013年 | 11230篇 |
2012年 | 12782篇 |
2011年 | 13231篇 |
2010年 | 9073篇 |
2009年 | 8428篇 |
2008年 | 12111篇 |
2007年 | 12606篇 |
2006年 | 11822篇 |
2005年 | 11300篇 |
2004年 | 11342篇 |
2003年 | 10628篇 |
2002年 | 10450篇 |
2001年 | 17417篇 |
2000年 | 17427篇 |
1999年 | 13910篇 |
1998年 | 5020篇 |
1997年 | 5269篇 |
1996年 | 4910篇 |
1995年 | 4616篇 |
1994年 | 4484篇 |
1993年 | 4536篇 |
1992年 | 11606篇 |
1991年 | 11533篇 |
1990年 | 11292篇 |
1989年 | 10906篇 |
1988年 | 10486篇 |
1987年 | 10075篇 |
1986年 | 9362篇 |
1985年 | 9231篇 |
1984年 | 7746篇 |
1983年 | 6703篇 |
1982年 | 5160篇 |
1981年 | 4616篇 |
1980年 | 4462篇 |
1979年 | 7419篇 |
1978年 | 5863篇 |
1977年 | 5396篇 |
1976年 | 5201篇 |
1975年 | 5594篇 |
1974年 | 6300篇 |
1973年 | 6166篇 |
1972年 | 5764篇 |
1971年 | 5226篇 |
1970年 | 4633篇 |
1969年 | 4574篇 |
1968年 | 4421篇 |
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
871.
The nisin resistance determinant and an origin of replication on pNP40, a plasmid of about 60 kilobases that is present in Streptococcus lactis subsp. diacetylactis DRC3, was cloned on a 7.6-kilobase EcoRI fragment. When self-ligated, this fragment existed as an independent replicon (pFM011) and contained a 2.6-kilobase EcoRI-XbaI fragment encoding nisin resistance. 相似文献
872.
Cultured cells from the anterior pituitary glands of adult rats were treated with the tripeptide aldehyde proteinase inhibitor, BOC-DPhe-Phe-Lys-H. The addition of this tripeptide aldehyde decreased the in vitro release of prolactin to 25% of the control value, while the release of growth hormone in the same cultures decreased to 33% of the control value. Prolactin immunostaining was stronger in semithin sections of proteinase-inhibitor-treated cultures than in control sections. After 2 h treatment with the inhibitor, prolactin- and growth hormone-containing secretory granules were numerous, and the number of crinophagic vacuoles had increased. In the presence of the inhibitor, the overall cytoarchitecture of parenchymal cells was well preserved, and the pathway of the uptake of cationic ferritin appeared to be unaffected. 相似文献
873.
874.
Major outer membrane protein in Salmonella typhimurium induced by maltose. 总被引:14,自引:8,他引:6 下载免费PDF全文
E T Palva 《Journal of bacteriology》1978,136(1):286-294
A maltose-induced major outer membrane protein (the 44K protein) is demonstrated in Salmonella typhimurium. This protein resembles the lambda receptor of Escherichia coli in its location, induction properties, apparent molecular weight, and association with the peptidoglycan layer of the cell wall. The 44K protein is missing in certain Salmonella Mal- mutants, which are also missing a protein analogous to the maltose-binding protein of E. coli. Thus, these mutants may be defective in the control of maltose genese in Salmonella. The proteins appear to be closely related, as indicated by cross-reaction of the Salmonella protein with the antiserum raised against the lambda receptor; however, they are not identical, since the peptide patterns obtained after limited proteolysis are completely different. Bacteriophage lambda does not use the 44K protein as a receptor. 相似文献
875.
876.
877.
878.
879.
880.
The development of alatae of the green peach aphid, Myzus persicae, as gynoparae rather than as virginoparae was investigated with regard to the number of exposures to a long-night (LN) regime of 15 h darkness per diem which the aphids experienced before and/or after their birth. The minimum number of exposures to LN that resulted in all of the alatae developing into gynoparae was two prenatal plus one postnatal or one prenatal plus two postnatal, provided the scotophases in these treatments were at least 12 h long. A cumulative effect of several successive exposures to LN was also evident when the presumptive alatae were exposed to LN either from birth or not until several days after birth. Fewer exposures to LN were needed in the former case.
Zusammenfassung Die Entwicklung von Alatae der grünen Pfirsichblattlaus, Myzus persicae, hauptsächlich zu Gynoparae, eher als zu Virginoparae, wurde im Hinblick auf den Einfluss der Anzahl an Langnächten (LN: 15 Studen Dunkelheit pro Tag), denen die Aphiden vor und/oder nach der Geburt ausgesetzt waren, untersucht. Zur ausschliesslichen Entwicklung aller Alatae zu Gynoparae waren mindestens 2 prenatale und eine postnatale LN-Exposition oder eine prenatale und 2 postnatale LN-Expositionen notwendig, vorausgesetzt die Dunkelphasen betrugen mindestens 12 Stunden. Ausserdem zeigte sich ein kumulativer Effect durch mehrere, aufeinanderfolgende LN-Expositionen, wenn die Alatae diesen von Geburt an, oder einige Tage nach der Geburt, ausgesetzt waren. Im ersten Fall waren weniger LN-Expositionen notwendig.相似文献