全文获取类型
收费全文 | 836721篇 |
免费 | 99557篇 |
国内免费 | 333篇 |
出版年
2016年 | 9201篇 |
2015年 | 12713篇 |
2014年 | 15052篇 |
2013年 | 21889篇 |
2012年 | 24359篇 |
2011年 | 24561篇 |
2010年 | 16358篇 |
2009年 | 15314篇 |
2008年 | 22013篇 |
2007年 | 22827篇 |
2006年 | 21614篇 |
2005年 | 20793篇 |
2004年 | 20617篇 |
2003年 | 19855篇 |
2002年 | 19302篇 |
2001年 | 36047篇 |
2000年 | 36667篇 |
1999年 | 29401篇 |
1998年 | 10750篇 |
1997年 | 11327篇 |
1996年 | 10900篇 |
1995年 | 10240篇 |
1994年 | 10286篇 |
1993年 | 10172篇 |
1992年 | 25448篇 |
1991年 | 25023篇 |
1990年 | 24671篇 |
1989年 | 24232篇 |
1988年 | 22326篇 |
1987年 | 21482篇 |
1986年 | 20050篇 |
1985年 | 20293篇 |
1984年 | 16891篇 |
1983年 | 14850篇 |
1982年 | 11436篇 |
1981年 | 10521篇 |
1980年 | 10014篇 |
1979年 | 16665篇 |
1978年 | 12986篇 |
1977年 | 11845篇 |
1976年 | 11339篇 |
1975年 | 12455篇 |
1974年 | 13053篇 |
1973年 | 12854篇 |
1972年 | 11999篇 |
1971年 | 10549篇 |
1970年 | 9265篇 |
1969年 | 8700篇 |
1968年 | 7956篇 |
1967年 | 7016篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
891.
Ole Didrik Laerum Walter R. Paukovits 《Differentiation; research in biological diversity》1984,27(1-3):106-112
Abstract. Degeneration of the archenteron in middle gastrulae occurred in the presence of α,α'-dipyridyl or Zn2+ , inhibitors of prolyl hydroxylase. In the presence of these substances the archenteron degenerated and was eventually destroyed. Adding Fe2+ to the embryo culture containing α,α'-dipyridyl protected the archenteron from further degeneration, but the collapsed archenteron was not restored to the upright position. At the late gastrula stage, α,α'-dipyridyl did not cause the degeneration of the archenteron. Treatment of the embryos by α,α'-dipyridyl, starting at the swimming blastula stage, resulted in the production of many mesenchyme-like cells but archenteron was not produced in the embryos. Addition of Fe2+ to α,α'-dipyridyl culture, just before the beginning of gastrulation of normal embryos, resulted in the formation of normal archenteron. α,α'-Dipyridyl inhibited hydroxylation of proline residues of collagen in sea urchin embryos and Fe2+ prevented the inhibition by α,α'-dipyridyl. Respiration was not inhibited by α,α'-dipyridyl. 相似文献
892.
893.
Interaction of some polyhexamethylene biguanides and membrane phospholipids in Escherichia coli 总被引:6,自引:0,他引:6
The interaction between some polyhexamethylene biguanides and the cell envelope of Escherichia coli has been investigated. An amine-ended dimer, (AED, n = 2), a polydisperse mixture (ICI plc) available as the active ingredient of Vantocil IB, (PHMB, n = 5.5), and a high molecular weight fraction, (HMW, n = greater than or equal to 10) of PHMB were used. The sensitivity of batch cultures depleted of magnesium (M-dep), phosphorus (P-dep) or glycerol (C-dep) towards the biocides was assessed by monitoring the rate and extent of potassium ion leakage. P-dep suspensions were particularly resistant to all these agents and possessed less than half the quantity of phospholipid of other cell types. This was compensated for by a proportionate increase in fatty acid and neutral lipid content of the cells. The reduction in phospholipid content was accounted for by decreases in phosphatidylglycerol (PG) and phosphatidylethanolamine (PE). Diphosphatidylglycerol (DPG) and phosphatidylserine (PS) content of the cultures remained unaffected by the depleting nutrient. Fourier-transform n.m.r. spectroscopy was used to study proton nuclei during the interaction of HMW, AED and PHMB with various phospholipid-vesicle preparations. The results strongly suggest that the biocides acted preferentially on the acidic phospholipids PG and DPG, rather than towards PE or PS. Resistance of P-dep cultures therefore reflected reductions in PG content. A molecular basis for the interaction of these compounds and membranes is proposed. 相似文献
894.
895.
896.
Olsvik Ørjan Myhre Stein Berdal Bjorn P. Fossum Kåre 《Acta veterinaria Scandinavica》1982,23(2):204-210
Enterotoxigenic reference strains of Staphylococcus aureus were cultivated in sterile whole and skim milk for 18 h at 37°G. Staphylococcal enterotoxin A, B, and C were detected directly in the milk by an enzyme linked immunosorbent assay (ELISA), sensitive down to 1 ng/ml. Enterotoxins in the range of 1 ng–20 µg/ml milk were detected without any concentration or extraction. Skim and whole milk were almost identical as medium for enterotoxin production. 相似文献
897.
W.M.F. Jongen P.H.M. Lohman M.J. Kottenhagen G.M. Alink F. Berends J.H. Koeman 《Mutation research》1981,81(2):203-213
Several short-term mammalian test systems were used for mutagenicity testing of the organic solvent dichloromethane. The compound was negative in the forward mutation test on the HGPRT locus in Chinese hamster cells and the unscheduled DNA synthesis test in both human and hamster cells. In the test on DNA synthesis inhibition, dichloromethane caused an aspecific inhibition in both human and hamster cells, but in this test the effect did not indicate a DNA-damaging action. A weak positive effect was found in the test on sister-chromatid exchanges in hamster cells. 相似文献
898.
899.
900.