全文获取类型
收费全文 | 65694篇 |
免费 | 4270篇 |
国内免费 | 5篇 |
出版年
2023年 | 473篇 |
2022年 | 467篇 |
2021年 | 977篇 |
2020年 | 859篇 |
2019年 | 888篇 |
2018年 | 2010篇 |
2017年 | 1883篇 |
2016年 | 2450篇 |
2015年 | 3247篇 |
2014年 | 3234篇 |
2013年 | 4332篇 |
2012年 | 5217篇 |
2011年 | 4652篇 |
2010年 | 2907篇 |
2009年 | 2302篇 |
2008年 | 3601篇 |
2007年 | 3406篇 |
2006年 | 3231篇 |
2005年 | 2739篇 |
2004年 | 2674篇 |
2003年 | 2408篇 |
2002年 | 2201篇 |
2001年 | 1483篇 |
2000年 | 1461篇 |
1999年 | 1150篇 |
1998年 | 509篇 |
1997年 | 375篇 |
1996年 | 375篇 |
1995年 | 343篇 |
1994年 | 264篇 |
1993年 | 260篇 |
1992年 | 586篇 |
1991年 | 493篇 |
1990年 | 442篇 |
1989年 | 436篇 |
1988年 | 432篇 |
1987年 | 378篇 |
1986年 | 366篇 |
1985年 | 354篇 |
1984年 | 352篇 |
1983年 | 243篇 |
1982年 | 233篇 |
1981年 | 173篇 |
1980年 | 181篇 |
1979年 | 218篇 |
1978年 | 213篇 |
1975年 | 199篇 |
1974年 | 220篇 |
1973年 | 224篇 |
1972年 | 185篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
901.
Dimethyl sulfoxide present in the agar medium at concentration 0.2 % (v/v) and lower does not inhibit cytokinin-induced betacyanin
synthesis in theAmaranthus caudatus seedlings. The activity of kinetin, N6-(Δ2-isopentenyl)adenine andtrans- zeatin is the same when these cytokinins are dissolved in either water or dimethyl sulfoxide and incorporated into the medium
after autoclaving. A simple method is described which allows the cytokinin activity of slightly water-soluble and thermolabile
compounds,e.g. aromatic urea and thiourea derivatives, to be determined in theAmaranthus bioassay. 相似文献
902.
903.
The cellular immune response (MIF, E-rosette formation and changes in nucleolar morphology of lymphocytes) was followed as
related to age and antigenic stimulation. MIF in healthy infants increased from the 2nd to the 12th week of life as compared
with the first week, probably due to BCG vaccination. The total and active E-rosette formation did not change during the whole
period of investigation. Ring-shaped nucleoli increased gradually from the second week of life. Active nucleoli increased
up to the 4th week,i.e. after BCG vaccination and then slowly decreased. Micronucleoli being high in the first week, decreased during 24 weeks of
life. After artificial colonization of the intestine the production of MIF was slightly lower in colonized infants than in
controls from the 2nd to the 12th week. The other parameters followed were not influenced by colonization. 相似文献
904.
Six new species ofPenicillium Linkex Fries are described and illustrated. Four of them have been recovered from the atmosphere in Madrid, Spain, the other two species were isolated from must and from soil respectively. They clearly differ from all species of the genus described so far and are, therefore described and proposed as new taxa:Penicillium gerundense sp. nov.,Penicillium valentinum sp. nov.,Penicillium alicantinum sp. nov.,Penicillium malacaense sp. nov.,Penicillium tarraconense sp. nov., andPenicillium vasconiae sp. nov. 相似文献
905.
Four new species of Penicillium Link ex Fries are described and illustrated. All of them but one have been isolated from the atmosphere in Madrid, Spain. They clearly differ from all species of the genus described so far and are, therefore, described and proposed as new taxa: Penicillium aurantio-flammiferum sp. nov., Penicillium gallaicum sp. nov., Penicillium granatense sp. nov., and Penicillium ilerdanum sp. nov. 相似文献
906.
During a two-year survey on the air-borne fungi in the atmosphere of Barcelona (Spain), the following genera were isolated in decreasing order: Aureobasidium, Rhizopus, Mucor, Arthrinium, Phoma, Fusarium, Trichoderma, and Botrytis. 相似文献
907.
908.
Two strains ofAspergillus flavus Linkex Fr. and two strains ofA. parasiticus Speare were cultured on crushed moist wheat (Triticum durum var. Pané no. 247) for aflatoxin production studies in correlation with morphological changes. The toxicogenic strains were adapted to the substratum by means of successive transfers at regular intervals (72 h.)The amount aflatoxins synthesized by the toxicogenic strains decreased gradually after succesive subculturing. The decrease was accompanied by marked morphological changes. One of the strains studied,A. flavus NRRL 3251, lost completly the capacity of aflatoxin synthesis after several subcultures, presenting at the same time strong morphological variations.A. flavus CBS 120.62 also lost its toxicogenicity after six subcultures. 相似文献
909.
B U Ramírez 《Journal of neurobiology》1979,10(3):239-245
Cytochalasin-B, a drug known to interfere with axoplasmic transport, evoked fibrillary potentials in the geniohyoid muscle when applied to its motor nerve. Despite this denervation-like effect, neuromuscular transmission remained normal. Some contractile characteristics of the muscle were studied. It was found that contraction time, isometric twitch tension, and half-relaxation time were not altered by the drug treatment. The present findings show that neurogenic molecular factors conveyed by axoplasmic transport to the nerve terminal are involved in the regulation of some muscle membrane characteristics but do not modify the muscle contractile features. 相似文献
910.
African swine fever virus DNA sediments in neutral sucrose density gradients as a single component with a sedimentation coefficient of 60S. In alkaline sucrose density gradients, this material shows two components with sedimentation coefficients of 85S and 95S, respectively. The sedimentation rate value of alkali-denatured virus DNA in neutral sucrose density gradients and the renaturation velocity of denatured DNA show that is reassociated much faster than expected from its genetic complexity. This behavior is compatible with the existence of interstrand cross-links in the molecule. We also present results which suggest that there are only a few such cross-links per molecule, that they are sensitive to S1 nuclease digestion, and that they are probably located next to the ends of the DNA. 相似文献