全文获取类型
收费全文 | 1061338篇 |
免费 | 107479篇 |
国内免费 | 471篇 |
出版年
2018年 | 13274篇 |
2017年 | 12696篇 |
2016年 | 15579篇 |
2015年 | 17250篇 |
2014年 | 20317篇 |
2013年 | 29264篇 |
2012年 | 34183篇 |
2011年 | 37868篇 |
2010年 | 26373篇 |
2009年 | 24622篇 |
2008年 | 33435篇 |
2007年 | 35733篇 |
2006年 | 29292篇 |
2005年 | 28591篇 |
2004年 | 28017篇 |
2003年 | 27310篇 |
2002年 | 26809篇 |
2001年 | 45943篇 |
2000年 | 45798篇 |
1999年 | 36439篇 |
1998年 | 13098篇 |
1997年 | 13302篇 |
1996年 | 12716篇 |
1995年 | 11736篇 |
1994年 | 11435篇 |
1993年 | 11335篇 |
1992年 | 30039篇 |
1991年 | 29371篇 |
1990年 | 28595篇 |
1989年 | 27760篇 |
1988年 | 25606篇 |
1987年 | 24325篇 |
1986年 | 22669篇 |
1985年 | 22522篇 |
1984年 | 18582篇 |
1983年 | 16173篇 |
1982年 | 12274篇 |
1981年 | 11090篇 |
1980年 | 10302篇 |
1979年 | 17498篇 |
1978年 | 13656篇 |
1977年 | 12316篇 |
1976年 | 11648篇 |
1975年 | 13110篇 |
1974年 | 13967篇 |
1973年 | 13734篇 |
1972年 | 13024篇 |
1971年 | 11495篇 |
1970年 | 9820篇 |
1969年 | 9574篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
211.
An isoleucine arrest point in G1 was determined by two methods for CHO and 3T3 cells. In the first method the fraction of cells entering S after isoleucine deprivation was assessed by [3H]thymidine labelling and autoradiography. In the second method cells entering S after isoleucine deprivation were identified by double-label autoradiography using [3H] and [14C]thymidine. From the fraction of cells entering S, determined by the two methods, the arrest point in G1 (and entry into G0) is located within the last 40 min of G1. 相似文献
212.
213.
214.
Conditions for breaking various medically important yeasts using glass beads, 30 ml Corex centrifuge tubes, and a Vortex mixer were determined. From 75–95% ofCandida hyphal cells and all species of yeasts exceptSporothrix schenckii were broken when 10 g of 0.45–0.50 mm glass beads, 50–300 mg of wet cells in 5 ml of buffer, and 90 s of vortexing were employed. Yeasts ofSporothrix schenckii broke more efficiently when 0.25–0.30 mm beads were used. 相似文献
215.
216.
217.
218.
The time and dose dependence of the relationship between uptake of labelled precursors into protein and RNA and production of testosterone by rabbit follicles was examined. Although testosterone production was stimulated by luteinizing hormone at concentrations between 0.1 and 10 microgram/ml, the uptake of [3H]leucine into protein was significant only when the concentration of luteinizing hormone was greater than 2.5 microgram/ml. Increased production of testosterone was observed within 15 min of stimulation with luteinizing hormone whereas uptake of [3H]leucine was only significant at 90 min. Puromycin (40 microgram/ml) and cycloheximide (10 microgram/ml) in the presence of luteinizing hormone inhibited the synthesis of both testosterone and protein. However, lower concentrations of puromycin (0.1, 1 and 10 microgram/ml) and cycloheximide (1 microgram/ml) had no effect on luteinizing hormone-induced testosterone production but significantly inhibited protein synthesis by 58, 37, 31 and 71%, respectively. Actinomycin D (20, 80 and 160 microgram/ml) alone and in combination with 5 microgram luteinizing hormone/ml severely inhibited uptake of [3H]uridine into RNA without affecting testosterone production. However, with 1 microgram actinomycin/ml, testosterone production was significantly (P less than 0.01) greater than in the presence of luteinizing hormone alone. These results cast doubt on the obligatory role of RNA and protein synthesis in rabbit ovarian follicular steroidogenesis. 相似文献
219.
beta-lactamase has been purified to a homogeneous state from Mycobacterium butyricum ATCC 19979. The molecular weight (Mr = 29,000) and the isoelectric point (4,0) of the enzyme have been determined. The enzyme showed both penicillinase and cephalosporinase activity, but had relatively more of the former. With respect to substrate-profile the enzyme resembled the plasmid specified TEM-type beta-lactamases commonly encountered in Gram-negative bacteria. The enzyme was insensitive to p-chloromercuribenzoate, sodium chloride, or iodine inhibition. 相似文献
220.