全文获取类型
收费全文 | 128577篇 |
免费 | 7957篇 |
国内免费 | 14篇 |
出版年
2023年 | 750篇 |
2022年 | 828篇 |
2021年 | 1832篇 |
2020年 | 1581篇 |
2019年 | 1724篇 |
2018年 | 3525篇 |
2017年 | 3178篇 |
2016年 | 4256篇 |
2015年 | 5576篇 |
2014年 | 5799篇 |
2013年 | 7715篇 |
2012年 | 8928篇 |
2011年 | 8050篇 |
2010年 | 5308篇 |
2009年 | 4142篇 |
2008年 | 6403篇 |
2007年 | 6028篇 |
2006年 | 5875篇 |
2005年 | 5000篇 |
2004年 | 4952篇 |
2003年 | 4493篇 |
2002年 | 4101篇 |
2001年 | 3180篇 |
2000年 | 3063篇 |
1999年 | 2375篇 |
1998年 | 1106篇 |
1997年 | 829篇 |
1996年 | 839篇 |
1995年 | 763篇 |
1994年 | 663篇 |
1992年 | 1373篇 |
1991年 | 1233篇 |
1990年 | 1173篇 |
1989年 | 1232篇 |
1988年 | 1054篇 |
1987年 | 1045篇 |
1986年 | 966篇 |
1985年 | 1007篇 |
1984年 | 901篇 |
1983年 | 721篇 |
1982年 | 626篇 |
1979年 | 827篇 |
1978年 | 635篇 |
1975年 | 705篇 |
1974年 | 773篇 |
1973年 | 746篇 |
1972年 | 672篇 |
1970年 | 642篇 |
1969年 | 696篇 |
1968年 | 660篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Screening of plasmids in non-pathogenic corynebacteria 总被引:1,自引:0,他引:1
H. Sandoval G. del Real L.M. Mateos A. Aguilar J.F. Martín 《FEMS microbiology letters》1985,27(1):93-98
Abstract A screening of plasmids in 25 nonpathogenic coryneform bacteria was carried out. 11 Strains showed at least one plasmid, ranging in size from 4.2 to 55 kb. These plasmids did not encode bacteriocin production or resistance to a number of antibiotics or to ions such as arsenite, mercury(II) and cobalt(II). A detailed study of plasmid pBL100 from Brevibacterium linens is presented. pBL100 has a size of 7.75 kb, and contains single sites for the endonucleases: Hin dIII; Pst I, Bgl II, Eco RI and Bam HI. B. linens is easily and efficiently transformed with vectors derived from pBL1 isolated from Brevibacterium lactofermentum . 相似文献
992.
Ján Michalko 《Folia Geobotanica》1985,20(3):313-317
Classification of euhemerobic calciphilous pine-communities should be based on studies carried out over an extensive area and for several seasons. The Malé Karpaty Mts. are situated near the northern boundary of the distribution ofPinus nigra and it is mecessary to find the planting time of allPinus nigra stands. The common use ofEllenberg’s “Zeigerwerte der Gefässpflanzen Mitteleuropas” for the ecological evaluation of plant communities in the Western Carpathians Mts. is criticised for several reasons. 相似文献
993.
A method is proposed to analyse the dispersion profiles of species in classes of environmental variables, based on the decomposition of the expected frequencies in contingency tables with many interacting species. The method has been applied to data of dominant or very frequent graminoid species in grasslands of the Natisone Valley (Friuli, Italy). It allowed to make predictions by removing the random component of variation.Nomenclature follows: P. Zangheri (1976). Flora Italica, CEDAM, Padua.The authors were recipients of an Italian CNR grant (E. Feoli) and a Canadian NSERC grant (L. Orlóci) during tenure of this project. The results are in partial fulfillment of a commitment to the Centro Regionale per la Sperimentazione Agraria per il Friuli-Venezia Giulia. 相似文献
994.
Photobiont cells of the lichen Evernia prunastri have completely been separated from their fungal partner by filtration through a bed of Sepharose 2B. Both mannitol and ribitol have been quantified by gas-liquid chromatography in the different steps of the isolation procedure. Absence of mannitol, which is exclusively produced by the mycobiont, has been used as the best probe to monitor isolation. 相似文献
995.
R Gonzàlez-Duarte L Vilageliu 《Comp. Biochem. Physiol. C, Comp. Pharmacol. Toxicol.》1985,80(1):189-193
Ethanol at low concentration increases larval viability in D. funebris and D. melanogaster and decreases it in D. immigrans. Isopropanol decreases viability in all three species. Isopropanol depresses alcohol dehydrogenase activity. This is accompanied by a change in the relative proportion of electrophoretic forms of the enzyme. Acetone appears in the medium when larvae of D. funebris and D. immigrans develop in the presence of isopropanol. It can be transformed again into isopropanol on reaching a threshold value. It seems that this transformation cannot be carried out by alcohol dehydrogenase alone. 相似文献
996.
Javier G. Fernández Velasco Norma L. Pucheu Oscar Romero Norma L. Kerber Raúl A. Fernández Augusto F. García 《Archives of microbiology》1985,143(2):192-195
The conditions under which an oscillatory behaviour is observed during net hydrolysis or synthesis of ATP in chromatophores of Rhodospirillum rubrum FR1 are described. In the case of ATPase the oscillations are observed at low temperature (ca. 11°C) in the dark after an initial transient behaviour. These oscillations are attenuated or disappear by the addition of an uncoupler.Oscillations are also observed during ATP synthesis. At 3°C the oscillations appear spontaneously if photophosphorylation is measured during a sufficiently long time. At 30°C the mere intercalation of a dark period also at 30°C is sufficient to trigger the oscillations in the following light period.Abbreviations Bchl
Bacteriochlorophyll
- FCCP
carbonyl cyanide p-trifluoromethoxyphenyl hydrazone
- PMS
phenazine methosulfate
- TMPD, N,N,N,N
tetramethyl-1,4-phenylenediamine
Dedicated to Prof. Dr. Gerhart Drews as a homage for his permanent example as hard worker and careful scientist and also for his remarkable human quality 相似文献
997.
Francisco Romero Francisco Javier Caballero Francisco Castillo José Manuel Roldán 《Archives of microbiology》1985,143(2):111-116
Anti-glutamine synthetase serum was raised in rabbits by injecting purified glutamine synthetase (GS) of the phototrophic bacterium Rhodopseudomonas capsulata E1F1. The antibodies were purified to monospecificity by immunoaffinity chromatography in GS-sepharose gel. These anti-GS antibodies were used to measure the antigen levels in crude extracts from bacteria, grown phototrophically with dinitrogen, nitrate, nitrite, ammonia, glutamate, glutamine or alanine as nitrogen sources. The amount of GS detected by rocket immunoelectrophoresis was proportional to Mn2+-dependent transferase activity measured in the crude extracts. Addition of GS inhibitor l-methionine-d,l-sulfoximine (MSX) to the actively growing cells promoted increased antigen levels, that were not found in the presence of glutamine or chloramphenicol. The ammonia-induced decrease in GS relative levels was reverted by MSX. GS levels remained constant when phototrophically growing cells were kept in the dark.Abbreviations GS
glutamine synthetase
- MOPS
2-(N-morpholine) propane sulfonate
- MSX
l-methionine-d,l-sulfoximine 相似文献
998.
Freeze etching studies in a symbiotic and a freeliving strain of Chroococcidiopsis revealed a specific layer in the outer cell wall not described so far from Cyanophyta. The layer showed a complex organisation: The main unit are ribbons, 2–3 nm thick, striated at right angle to the longitudinal axis. They are interwoven to a patchwork-like leaflet. The ribbons are virtually composed of globular particles associated in parallel rows. The cytoplasmic membrane and the cell walls of the symbiotic and the free-living strain were compared.Abbreviations cm
cytoplasmic membrane
- CW 1,2,3
cell wall layer 1,2,3
- EF
exoplasmic fracture face
- PF
protoplasmic fracture face 相似文献
999.
Dr. Lucas del Castillo Agudo 《Current microbiology》1985,12(1):41-44
We developed a method of hybrid selection between homothallic wild-type and heterothallic strains. The hybrids obtained were used to study the heredity of ethanol tolerance and production. Both characters segregated independently, but no ethanol-sensitive strains were able to produce high levels of ethanol. At least four genes are implicated in ethanol tolerance. 相似文献
1000.
Formation of protoplasts and their reversion were followed in 7 strains of brevibacteria. The formation of protoplasts and
their reversion differed both between various species of brevibacteria and between various mutant strains of the same species. 相似文献