全文获取类型
收费全文 | 3244篇 |
免费 | 192篇 |
国内免费 | 4篇 |
专业分类
3440篇 |
出版年
2022年 | 25篇 |
2021年 | 41篇 |
2020年 | 36篇 |
2019年 | 36篇 |
2018年 | 57篇 |
2017年 | 43篇 |
2016年 | 62篇 |
2015年 | 118篇 |
2014年 | 122篇 |
2013年 | 164篇 |
2012年 | 195篇 |
2011年 | 183篇 |
2010年 | 143篇 |
2009年 | 120篇 |
2008年 | 157篇 |
2007年 | 184篇 |
2006年 | 154篇 |
2005年 | 143篇 |
2004年 | 154篇 |
2003年 | 146篇 |
2002年 | 126篇 |
2001年 | 31篇 |
2000年 | 34篇 |
1999年 | 36篇 |
1998年 | 37篇 |
1997年 | 18篇 |
1996年 | 25篇 |
1995年 | 38篇 |
1994年 | 22篇 |
1993年 | 29篇 |
1992年 | 14篇 |
1991年 | 17篇 |
1990年 | 19篇 |
1989年 | 13篇 |
1988年 | 19篇 |
1987年 | 22篇 |
1986年 | 17篇 |
1985年 | 19篇 |
1983年 | 20篇 |
1982年 | 26篇 |
1981年 | 16篇 |
1980年 | 19篇 |
1979年 | 24篇 |
1978年 | 17篇 |
1977年 | 20篇 |
1976年 | 14篇 |
1975年 | 12篇 |
1971年 | 12篇 |
1962年 | 11篇 |
1912年 | 18篇 |
排序方式: 共有3440条查询结果,搜索用时 15 毫秒
11.
Josef Deutscher 《FEMS microbiology letters》1985,29(3):237-243
Abstract A protein with an M r of 55000 was isolated from glucose-grown Streptococcus faecalis cells. The protein becomes phosphorylated in a phosphoenolpyruvate-dependent reaction catalyzed by enzyme I and HPr of the bacterial phosphotransferase system. It did not stimulate phosphoenolpyruvate-dependent glucose phosphorylation. Several sugars were tested for their ability to dephosphorylate the phosphorylated protein in the presence of membrane fragments. Even though some of the sugars were able to dephosphorylate phospho-HPr quickly, the factor III-like 55-kDa protein remained phosphorylated. We therefore assumed that this protein is not involved in any sugar uptake reaction but that it exerts a regulatory function in Gram-positive bacteria comparable to the function of factor III specific for glucose in Escherichia coli . 相似文献
12.
Josef Loidl 《Biotechnic & histochemistry》1985,60(1):13-19
Metaphase chromosome bands were induced in Allium flavum (Liliaceae) by protecting the chromosomal DN A with DN A-binding compounds of different base specificities against DNase digestion. The bands obtained represented different subsets of C-band heterochromatin. 相似文献
13.
The selection mutation equation 总被引:2,自引:0,他引:2
Josef Hofbauer 《Journal of mathematical biology》1985,23(1):41-53
Fisher's Fundamental Theorem of Natural Selection is extended to the selection mutation model with mutation rates
ij=ii.e. depending only on the target gene, by constructing a simple Lyapunov function. For other mutation rates stable limit cycles are possible. 相似文献
14.
15.
Helmut Sinzinger Thomas Zidek Peter Fitscha John O'Grady Otto Wagner Josef Kaliman 《Prostaglandins & other lipid mediators》1987,33(6)
Patients suffering from peripheral vascular disease have been “ultima ratio”-treated with PGI2 at a rate of 5 ng/kg/min for 6 hours a day and 5 consecutive days i.v. 20 of them underwent surgery thereafter as therapy was not sufficient. A histological examination and quantification of vascular tissue revealed that the number of activated smooth muscle cells was significantly lower in treated patients vascular segments than in untreated ones in all the different age groups. A comparable suppression was found in the intima and the media as well. It is thus concluded, that PGI2 inhibits smooth muscle cell proliferation most probably by inhibiting PDGF-release from the platelets and stimulation of smooth muscle cell cAMP. To achieve a more beneficial PGI2-effect at the vascular level, a prolonged PGI2-therapy looks rather promising. 相似文献
16.
Josef Ammermüller 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1986,158(3):339-344
Summary The passive electrical cable properties of ocellar L-neurons were determined by applying current steps and recording the voltage transients using a two-electrode intracellular current clamp system. Morphological data were obtained following intracellular staining with Lucifer yellow.Two groups of neurons were distinguished physiologically. In the first group both the membrane time constant
m and the first equalizing time constant
1 could be determined. In the second group only
m was measurable. The ratio of the physiological groups was equal to the ratio of the morphological types ML:(M1 plus M2) in the median ocellar nerve. Thus the first group probably consists of ML-type L-neurons. The passive cable properties of this group were calculated by combining the physiological and morphological data. The following values were obtained: electrotonic lengthL=1.35; membrane time constant
m =7.6 ms; length constant =0.22 cm; membrane resistivityR
m=2.0 · 103
· cm2; membrane capacitanceC
m=3.8 F · cm–2; intracellular resistivityR
i=24 · cm. Evidence is presented that the membrane parameters of the other types of L-neurons have the same values. The results are discussed with special reference to transmission in the ocellar system. 相似文献
17.
Three remarkable new genera of conidial lichen-forming fungi, with pycnidial or acervular conidiomata are described and illustrated.Hastifera tenuispora gen. et spec. nov. from the South-Tyrol, Italy, is characterized by very long and narrow hyaline conidia produced in pycnidial conidiomata immersed in thalline warts.Lichingoldia gyalectiformis gen. et spec. nov. from rocks subject to inundation by freshwater in Norway has long sigmoidly curved conidia which appear to be adapted to dispersal in water.Woessia fusarioides gen. et spec. nov. from aQuercus stump in the Burgenland, Austria, has a finely granular thallus and disc-like conidiomata producing falcate conidia; this species is also of interest in that it hasChlorella as the photobiont. The recently described hyphomyceteCheiromycina flabelliformis
B. Sutton is reported from Austria for the first time, and is also lichenized. Recent collections ofNigropuncta rugulosa
D. Hawksw. from Austria and Italy also show that this species is lichenized rather than parasymbiotic. In all five cases the fungal hyphae of the conidiogenous structures are continuous with those in intimate contact with cells of the algal partners and the biological relationship appears to be mutualistic giving rise to stable crustose lichen thalli. 相似文献
18.
Chromosome counts of the following 30 taxa (106 populations) are given:Betonica officinalis (2n=16);Bidens frondosus (2n=48);Calamagrostis arundinacea (2n=28+0–2B);Dianthus carthusianorum subsp.latifolius (2n=30);Festuca gigantea (2n=42, 42+2B);Hypericum perforatum (2n=32);Koeleria macrantha (2n=28);Kohlrauschia prolifera (2n=30);Lilium martagon (2n=24+0–2B);Melica ciliata (2n=18);Poa remota (2n=14);Ranunculus polyanthemos (2n=16);R. sardous subsp.sardous (2n=16);Roegneria canina (2n=28+0–1B);Rudbeckia laciniata (2n=76);Scabiosa canescens (2n=16);Serratula tinctoria (2n=22);Seseli elatum subsp.heterophyllum var.beckii (2n=18);S. hippomarathrum (2n=20);Thlaspicaerulescens caerulescens subsp.tatrense (2n=14);Trifolium alpestre (2n=16);T. avense (2n=14);T. medium (2n=79, 80+0–2B, 82);T. rubens (2n=16);Veronica officinalis subsp. alpestris (2n=36);Vincetoxicum hirundinaria (2n=22);Vulpia bromoides (2n=14);Zerna benekenii (2n=28)Z. monoclada (2n=28+0–8B);Z. ramosa (2n=42). Remarks on taxonomy, nomenclature and chorology for some of these taxa are given. 相似文献
19.
20.
Josef Holub 《Folia Geobotanica》1972,7(4):419-421
Helictotrichon desertorum (Less.) Nevskij is divided into four subspecies, based on the characters of the ligule and indumentum of the sheaths of cauline leaves. A new subspecies—subsp.centroasiaticum Holub—is proposed to cover the Central Asiatic segment of the species. 相似文献