全文获取类型
收费全文 | 4481篇 |
免费 | 433篇 |
国内免费 | 1797篇 |
出版年
2024年 | 10篇 |
2023年 | 112篇 |
2022年 | 175篇 |
2021年 | 237篇 |
2020年 | 200篇 |
2019年 | 222篇 |
2018年 | 254篇 |
2017年 | 194篇 |
2016年 | 225篇 |
2015年 | 196篇 |
2014年 | 272篇 |
2013年 | 338篇 |
2012年 | 221篇 |
2011年 | 260篇 |
2010年 | 226篇 |
2009年 | 258篇 |
2008年 | 294篇 |
2007年 | 264篇 |
2006年 | 271篇 |
2005年 | 273篇 |
2004年 | 241篇 |
2003年 | 228篇 |
2002年 | 183篇 |
2001年 | 137篇 |
2000年 | 159篇 |
1999年 | 125篇 |
1998年 | 114篇 |
1997年 | 104篇 |
1996年 | 94篇 |
1995年 | 90篇 |
1994年 | 85篇 |
1993年 | 67篇 |
1992年 | 91篇 |
1991年 | 78篇 |
1990年 | 53篇 |
1989年 | 46篇 |
1988年 | 42篇 |
1987年 | 35篇 |
1986年 | 47篇 |
1985年 | 25篇 |
1984年 | 28篇 |
1983年 | 16篇 |
1982年 | 26篇 |
1981年 | 21篇 |
1980年 | 13篇 |
1978年 | 12篇 |
1977年 | 9篇 |
1976年 | 10篇 |
1973年 | 6篇 |
1972年 | 7篇 |
排序方式: 共有6711条查询结果,搜索用时 13 毫秒
11.
1IntroductionElbo(ECG)offersalotofilllcorralltinfondionforthediagnosisOfheartdis-eases.Berz1,seahaormalEChcax[lrins>llleu"knownsituations,thcycanbeCSUghtinthelongti1Ylecontin~11xHlltoriDg.ndterrnoultonngsystemwhichcanrecord24-hoUrECGdataisoneofeffectiveme~toprovidethefun~.AlthOUghthehag6scaleICmorestohavebeeddevelopepbedeavailabletostorelOngtboeECGdsta,itisveqdifficultyandtioublesomethatalopnUmbeOfdstaisprasersandstoredortiallsillltted.InthedigitedECGdata,thereare… 相似文献
12.
Graeme J. Inglis† 《Journal of Ecology》2000,88(1):88-99
13.
14.
15.
16.
17.
MUNENORI NOGUCHI HIROSHI INOUE TOSHIHIRO ATAGO SHOGO NAKAMURA 《The Journal of eukaryotic microbiology》1997,44(2):127-133
ABSTRACT. The effects of organic solvents on the ATPase activity and the sliding disintegration of axonemes from Chlamydomonas were investigated. The axonemal ATPase was markedly activated by methanol accompanying with marked inhibition of the sliding disintegration of axonemes. On the contrary, glycerol inhibited the ATPase activity without serious inhibition of the sliding disintegration. As far as the axonemes are not irreversibly denatured by extremely high concentration of solvents, the effects of solvents both on the ATPase and the ability of sliding are reversible. Therefore, the inhibition of sliding accompanied by the activation of ATPase is probably due to an inability to couple the hydrolysis of ATP to sliding between dynein and microtubule in the presence of methanol. The axonemal ATPase was less sensitive to vanadate inhibition after exposure to methanol. This indicates that methanol makes the dyneinADP.Pi complex unstable and increases product release. On the other hand, glycerol and ethylene glycol seem to stabilize the force generation responsible for the sliding through stabilizing the dynein.ADP.Pi complex. 相似文献
18.
The ability to respond to phytochrome (Pfr, the far-red light absorbing from of phytochrome) with anthocyanin synthesis appears first in some marginal regions of the abaxial epidermis of the mustard cotyledons and from there spreads gradually over the entire tissue (transient phase). The pertinent pattern is independent of environmental influences such as light quality and nutritional culture conditions. The competence for Pfr in the epidermal cells, with regard to the initial action of Pfr (concerning anthocyanin synthesis), appears considerably earlier than the ability for actual anthocyanin synthesis. An electron microscopical study of the ultrastructural changes occurring in vacuoles and plastids of the epidermal cells during the transient phase showed that a correlation only exists between the differentiation of central cell vacuoles, originating from the aleurone vacuoles, and the appearance of the ability to accumulate anthocyanin. It is suggested that the formation of a central cell vacuole is a prerequisite for anthocyanin accumulation in the epidermal cells of the mustard seedling cotyledons.Abbreviations Pr, Pfr
red and far-red absorbing forms of phytochrome
- HS
Hoagland's nutrient solution 相似文献
19.
20.
A new index and four new graphical displays, termed "red–blue" plots, are presented to study and measure clustering in spatially referenced count data. The index can detect clusters in the form of patches, comprising several nearby large counts, and in the form of gaps, comprising several nearby small counts. The new methods quantify the degree to which the count for each sample unit contributes towards the overall degree of clustering, either as part of a patch or as a gap; provide tests of nonrandomness to detect clustering; and facilitate a comprehensive definition of the size and dimension of a cluster. The methods are illustrated using aphid field data. 相似文献