全文获取类型
收费全文 | 2499篇 |
免费 | 148篇 |
国内免费 | 139篇 |
出版年
2023年 | 44篇 |
2022年 | 55篇 |
2021年 | 76篇 |
2020年 | 76篇 |
2019年 | 90篇 |
2018年 | 70篇 |
2017年 | 68篇 |
2016年 | 88篇 |
2015年 | 94篇 |
2014年 | 112篇 |
2013年 | 163篇 |
2012年 | 74篇 |
2011年 | 107篇 |
2010年 | 70篇 |
2009年 | 112篇 |
2008年 | 130篇 |
2007年 | 125篇 |
2006年 | 111篇 |
2005年 | 88篇 |
2004年 | 73篇 |
2003年 | 61篇 |
2002年 | 68篇 |
2001年 | 67篇 |
2000年 | 43篇 |
1999年 | 51篇 |
1998年 | 58篇 |
1997年 | 33篇 |
1996年 | 41篇 |
1995年 | 36篇 |
1994年 | 34篇 |
1993年 | 21篇 |
1992年 | 35篇 |
1991年 | 40篇 |
1990年 | 34篇 |
1989年 | 28篇 |
1988年 | 30篇 |
1987年 | 21篇 |
1986年 | 30篇 |
1985年 | 42篇 |
1984年 | 23篇 |
1983年 | 29篇 |
1982年 | 24篇 |
1981年 | 19篇 |
1980年 | 28篇 |
1979年 | 12篇 |
1978年 | 9篇 |
1977年 | 6篇 |
1976年 | 11篇 |
1975年 | 7篇 |
1974年 | 7篇 |
排序方式: 共有2786条查询结果,搜索用时 312 毫秒
1.
Sequential medical trials involving paired data 总被引:2,自引:0,他引:2
2.
Sophie J. Milward Natalie Sebanz 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2016,371(1686)
This opinion piece offers a commentary on the four papers that address the theme of the development of self and other understanding with a view to highlighting the important contribution of developmental research to understanding of mechanisms of social cognition. We discuss potential mechanisms linking self–other distinction and empathy, implications for grouping motor, affective and cognitive domains under a single mechanism, applications of these accounts for joint action and finally consider self–other distinction in group versus dyadic settings. 相似文献
3.
《Current biology : CB》2022,32(3):645-653.e8
Download : Download video (10MB) 相似文献
4.
A robust method for selection of variables with the greatest discriminatory power is presented in the paper. The method deals with the two groups of data problem. An application of the method to some respiratory disease data and comparisons with classical procedures are given, also. 相似文献
5.
6.
《Developmental cell》2023,58(15):1399-1413.e5
- Download : Download high-res image (260KB)
- Download : Download full-size image
7.
Ethylene treatment (approx. 20 l ·1-1 in air for 2 d) of tobacco (Nicotiana tabacum L. cv. Havana 425) plants markedly increases the endo--1,3-glucanase (EC 3.2.1.39) content of leaves. The antigenic form of the enzyme induced is the same one whose production is blocked by treating cultured cells with combinations of auxin (1.1 · 10-5 M -naphthaleneacetic acid) and cytokinin (1.4 · 10-6 M kinetin). Evidence is presented that cultured tobacco cells require ethylene for -1,3-glucanase accumulation: i) ethylene treatment increased the accumulation of \-1,3-glucanase in callus tissues >10 d after subculturing and in cell-suspension cultures; ii) callus tissues can produce ethylene; iii) conditions known to inhibit ethylene production (1 mM CoCl2; 33° C treatment) or ethylene action (approx. 1.6 mmol · 1-1 norbornadiene in air) inhibited -1,3-glucanase accumulation by callus tissues treated for 4 d following subculturing; and, these inhibitory effects were prevented by exogenous ethylene. Combinations of auxin and cytokinin blocked ethylene-induced accumulation of -1,3-glucanase by cell-suspension cultures. The results favor a model in which ethylene induces results favor a model in which ethylene induces 1,3-glucanase accumulation, and auxin and cytokinin inhibit this induction process.Abbreviations NAA
-naphthaleneacetic acid
- NDE
norbornadiene 相似文献
8.
Voltage-dependent depolarization of bacterial membranes and artificial lipid bilayers by the peptide antibiotic nisin 总被引:24,自引:0,他引:24
The peptide antibiotic nisin is shown to disrupt valinomycin-induced potassium diffusion potentials imposed on intact cells of Staphylococcus cohnii 22. Membrane depolarization occurred rapidly at high diffusion potentials while at low potentials nisin-induced depolarization was slower suggesting that nisin requires a membrane potential for activity. This assumption was proven in experiments with planar lipid bilayers (black lipid membranes). Macroscopic conductivity measurements indicated a voltage-dependent action of nisin. The potential must have a trans-negative orientation with respect to the addition of nisin (added to the cis-side) and a sufficient magnitude (ca. -100 mV). With intact cells the threshold potential was lower (-50 to -80 mV at pH 7.5 and below -50 mV at pH 5.5). Single channel recordings resolved transient multistate pores, strongly resembling those introduced by melittin into artificial bilayers. The pores had diameters in the range of 0.2–1 nm, and lifetimes of few to several hundred milliseconds. The results indicate that nisin has to be regarded as a membrane-depolarizing agent which acts in a voltage-dependent fashion.Abbreviations BLM
Black lipid membranes
- CCCP
carbonyl cyanide m-chlorophenylhydrazone
- DOPC
dioleoyl phosphatidylcholine
- PS
phosphatidylserine
- TPP+
tetraphenylphosphonium cation 相似文献
9.
The role of allelopathy in citrus replant problems was investigated in Iraq. The failure of citrus seedlings to grow normally in old citrus orchards was not caused by differences between old and non-citrus soils in electrical conductivity, pH, organic matter, soil texture and those minerals tested. Extracts of soil collected from old citrus orchards significantly reduced the growth of sour orange seedlings. Extracts and decaying sour orange roots reduced the growth of sour orange seedlings as did extracts of non-senescent sour orange leaves and decaying senescent leaves. Thus it appears that allelopathy is at least partly involved in the citrus replant problem. 相似文献
10.
The relative ability of ovine follicle stimulating hormone and itsβ-subunit, two potential candidates for male contraceptive vaccine, to generate antibodies in monkeys capable of bioneutralizing
follicle stimulating hormone was assessed usingin vitro model systems. Antiserum against native ovine follicle stimulating hormone was found to be highly specific to the intact
form with no cross-reactivity with either of the two subunits while the antiserum againstβ-subunit of follicle stimulating hormone could bind to theβ-subunit in its free form as well as when it is combined withα-subunit to form the intact hormone. Both antisera could block the binding of the hormone to the receptor if the hormone was
preincubated with the antibody. However, the follicle stimulating hormoneβ-antisera could only inhibit the binding of the hormone partially (33% inhibition) if the antibody and receptor were mixed
prior to the addition of the hormone, while antisera to the native follicle stimulating hormone could block the binding completely
(100% inhibition) in the same experiment. Similarly antisera to the native follicle stimulating hormone was significantly
effective in blocking (100%) response to follicle stimulating hormone but not theβ-subunit antisera (0%) as checked using anin vitro granulosa cell system. Thus the probability of obtaining antibodies of greater bioneutralization potential is much higher
if intact hormone is used as an antigen rather than itsβ-subunit as a vaccine.
Majority of the work reported here was carried out during the tenure of Visiting Scientist fellowship awarded by the MRC Canada
to the first author. 相似文献