全文获取类型
收费全文 | 20701篇 |
免费 | 1450篇 |
国内免费 | 8篇 |
专业分类
22159篇 |
出版年
2023年 | 135篇 |
2022年 | 168篇 |
2021年 | 333篇 |
2020年 | 279篇 |
2019年 | 280篇 |
2018年 | 532篇 |
2017年 | 477篇 |
2016年 | 655篇 |
2015年 | 1025篇 |
2014年 | 1057篇 |
2013年 | 1369篇 |
2012年 | 1713篇 |
2011年 | 1632篇 |
2010年 | 990篇 |
2009年 | 805篇 |
2008年 | 1305篇 |
2007年 | 1237篇 |
2006年 | 1128篇 |
2005年 | 1097篇 |
2004年 | 1019篇 |
2003年 | 886篇 |
2002年 | 786篇 |
2001年 | 326篇 |
2000年 | 247篇 |
1999年 | 221篇 |
1998年 | 143篇 |
1997年 | 131篇 |
1996年 | 115篇 |
1995年 | 107篇 |
1994年 | 85篇 |
1993年 | 94篇 |
1992年 | 121篇 |
1991年 | 96篇 |
1990年 | 111篇 |
1989年 | 81篇 |
1988年 | 75篇 |
1987年 | 66篇 |
1986年 | 63篇 |
1985年 | 84篇 |
1984年 | 77篇 |
1983年 | 65篇 |
1982年 | 68篇 |
1981年 | 68篇 |
1979年 | 83篇 |
1978年 | 82篇 |
1976年 | 56篇 |
1975年 | 56篇 |
1974年 | 59篇 |
1973年 | 48篇 |
1971年 | 49篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Antti Huunan-Seppälä 《Journal of bioenergetics and biomembranes》1971,2(3-4):197-207
The effect of the polybasic substances Polybrene and spermine on the passive and active transport of monovalent cations in mitochondria was studied. These agents were found to stimulate the low amplitude swelling of mitochondria. Volume oscillations were induced by addition of substrate in the presence of spermine. In conditions where weak oscillations were obtained without these substances, oscillations were stimulated and their frequencies increased in the presence of Polybrene and spermine. Their effects were maximal with 100–300 moles spermine per litre and 3–5 mg Polybrene per litre. These results are discussed in relation to an interaction of the agents studied with membrane negative charges which may be important regulators of ion transport. 相似文献
62.
63.
Henri Saëz 《Mycopathologia》1970,41(3-4):383-395
Résumé Chez 44 Babouins,Papio papio (Desm.), appartenant à la collection du Parc zoologique de Paris, distingués en trois groupes, en fonction de l'âge, nous avons pratiqué 101 prélèvements aux niveaux suivants du tube digestif: intestin grêle gros intestin et rectum.C'est chez les animaux les plus âgés que nous avons obtenu les valeurs les plus élevées pour les deux critères étudiés, le pourcentage de positivité et la richesse spécifique des prélèvements et ce, aussi bien en ce qui concerne l'ensemble des levures identifiées que pour les seuls constituants de la flore probable. La fréquence de ces champignons aux divers étages du tube digestif, ainsi que l'incidence saisonnière sur les isolements ont été abordés.
In 44 Baboons,Papio papio (Desm.), of the Zoological Park of Paris, 101 samples have been taken at three levels of the alimentary tract: small intestine, large intestine and rectum. Three groups of subjects have been recognized according to age. The yeasts or the yeast-like flora, have been found with maximum of frequency and diversity in the oldest animals. The variations of the isolation in the three levels of this Mammal's gut and the seasonal influence have been discussed.相似文献
64.
The course of biosynthesis of fatty acids in the seeds of winter rape (Brassica napus L. ssp.oleifera, f.biennis cv. T?ebí?ská) was investigated. After the termination of flowering seed samples were taken at five intervals, the seeds were divided into 4 fractions according to size, and their weight, water content, oil content and fatty acid composition were determined. The oil content was found to increase in all size categories with time, with the exception of a minute drop when complete maturity is reached. Larger seeds contained more oil. The fatty acid composition changes with time in the individual size fractions almost continuously. The same holds for differences between seed sizes of the same sample. The main change in oil composition consists in the decrease of C18 acids in favour of C22 acids. Greatest decrements during maturation were found with oleic acid, less with linoleic acid. In absolute amounts the quantity of all synthesized acids rises, the greatest rise being observed with C22 acids (i.e. predominantly erucic acid). It follows from the mean rates of synthesis of the individual groups (C16, C18, C20, C22) of fatty acids that the fraction of C22 rate of synthesis increases, while that of the C18 acids decreases with the same speed. The results indicate that the fatty acid synthesis is most intense during the second half of seed maturation, the main role being played by accelerating the synthesis of higher acids, especially of erucic acid. 相似文献
65.
Ribosomal precursor RNA in Saccharomyces carlsbergensis 总被引:9,自引:0,他引:9
66.
Lubomír Scháněl 《Biologia Plantarum》1966,8(4):292-298
Mycelium of white-rot fungi secretes laccase into the medium. It was found by cultivation on malt-agar plates that the mycelium does not produce laccase equally in all its parts. The youngest hyphae at the margins of the colony represent usually the maximum producers, whereas older hyphae produce less or none at all. An exception here isCollybia velutipes which is the weakest producer of laccase of all the fungi studied and where only the older hyphae begin to secrete it. Manometric estimation of laccase showed that maximum specific activity of laccase is achieved at the boundary between the phases of initial and linear growth and i11 some cases during the first half of linear growth. Ageing of the mycelium characterized by certain changes in its metabolism is reflected in changes of enzyme production by fungal hypha of different age. 相似文献
67.
68.
Rudolf Dostál 《Biologia Plantarum》1964,6(3):236-237
U r?stově na za?átku fyziologického odpo?inku inhibovaných rostlinTilia platyphyllos Scop. aTilia cordata Mill. se vlivem giberelové kyseliny (GA3) zachoval terminální pupen jako náznak monopodiálního větvení, co? lze vylo?it jako fylogenetickou rekapitulaci. P?itom se ukázalo, ?e po?et normálně na letorostech zachovávaných list? je p?edur?en ji? v pupenech. 相似文献
69.
Csillag A. Bourne R. C. Patel Sanjay N. Stewart Michael G. Tömböl Teréz 《Brain Cell Biology》1989,18(3):369-379
Brain Cell Biology - The distribution of GABA-like immunoreactivity (GABA-LI) in the ectostriatal core (Ec) of domestic chicks (one to two days old) was investigated using (1) preembedding GABA... 相似文献
70.
J. Soinila A. Salo H. Uusitalo N. Yanaihara O. Häppölä 《Histochemistry and cell biology》1989,91(6):455-460
Summary Indirect immunofluorescence technique was used to study the occurrence and distribution of CGRP immunoreactivity in the submandibular gland of normal rats and after unilateral sensory and sympathetic denervations. In normal rats, CGRP-immunoreactive nerve fibers and nerve trunks were seen around or in close contact with interlobular salivary ducts as well as around small blood vessels of the gland. Occasionally, CGRP-immunoreactive nerve fibers were also detected between or around the acini of the gland.The submandibular ganglia contained CGRP-immunoreactive nerve fibers, but the ganglion cells were not immunoreactive for CGRP. The trigeminal ganglion contained a population of CGRP-immunoreactive, mainly small sized ganglion cells and nerve fibers distributed throughout the ganglion. Unilateral electrocoagulation of the trigeminal nerve caused a significant reduction in the number of immunoreactive nerve fibers in the gland, although some fibers still were present in the ipsilateral glandular tissue. Unilateral superior cervical ganglionectomy caused no detectable effect on the number of CGRP-immunoreactive nerve fibers in the gland.The present results suggest that the rat submandibular gland contains CGRP-immunoreactive nerve fibers both around blood vessels and in glandular secretory elements. Denervation experiments support the view that the majority, but perhaps not all of them originate from the trigeminal ganglion. 相似文献