全文获取类型
收费全文 | 27953篇 |
免费 | 2127篇 |
国内免费 | 7篇 |
专业分类
30087篇 |
出版年
2023年 | 234篇 |
2022年 | 195篇 |
2021年 | 443篇 |
2020年 | 365篇 |
2019年 | 395篇 |
2018年 | 864篇 |
2017年 | 827篇 |
2016年 | 987篇 |
2015年 | 1158篇 |
2014年 | 1170篇 |
2013年 | 1765篇 |
2012年 | 2518篇 |
2011年 | 2501篇 |
2010年 | 1338篇 |
2009年 | 1008篇 |
2008年 | 1895篇 |
2007年 | 1881篇 |
2006年 | 1811篇 |
2005年 | 1553篇 |
2004年 | 1528篇 |
2003年 | 1406篇 |
2002年 | 1229篇 |
2001年 | 279篇 |
2000年 | 345篇 |
1999年 | 232篇 |
1998年 | 168篇 |
1997年 | 109篇 |
1996年 | 120篇 |
1995年 | 127篇 |
1994年 | 101篇 |
1993年 | 100篇 |
1992年 | 125篇 |
1991年 | 101篇 |
1990年 | 101篇 |
1989年 | 77篇 |
1988年 | 71篇 |
1987年 | 57篇 |
1986年 | 59篇 |
1985年 | 67篇 |
1984年 | 91篇 |
1983年 | 53篇 |
1982年 | 70篇 |
1981年 | 64篇 |
1980年 | 69篇 |
1979年 | 50篇 |
1978年 | 57篇 |
1977年 | 46篇 |
1976年 | 45篇 |
1975年 | 41篇 |
1974年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
Coelho-Rocha Nina Dias de Jesus Luís Cláudio Lima Barroso Fernanda Alvarenga Lima da Silva Tales Fernando Ferreira Enio Gonçalves José Eduardo dos Santos Martins Flaviano de Oliveira Carvalho Rodrigo Dias Barh Debmalya Azevedo Vasco Ariston de Carvalho 《Probiotics and antimicrobial proteins》2023,15(1):160-174
Probiotics and Antimicrobial Proteins - Beneficial effects of Lactiplantibacillus plantarum strains have been widely reported. Knowing that the effects of probiotic bacteria are strain-dependent,... 相似文献
24.
Several aspects of community organization wereanalyzed comparatively in a small side-arm of theParaná River (Correntoso) and a shallowfloodplain lake (El Tigre) (31° 41 S and60° 42 W), in relation to the hydrology of thesystem. Taxonomic and morphological composition inthe river differed from that in the lake: the riverhad lower species richness (151 vs 218),different contributions of some Classes to totalspecies number (higher Cyano-, Zygo- andDiatomophyceae vs higher Chlorophyceae), anddiffent proportions of nannoplanktonic algae (67.5%vs 80.7%) and netplanktonic filamentousspecies (18.2% vs 4.2%). Phytoplanktonbiomass, higher in the lake than in the river due tothe retention time, was mostly dominated bynannoplankton and netplankton. Loticphytoplankton was dominated by typical fluvialspecies of Diatomophyceae (R-strategists). Riverconditions seem to maintain a subclimacticcommunity, which was little impacted by the flushingof populations from floodplain lakes. Water levelwas the main factor controlling phytoplanktonbiomass, species diversity (H), evenness (E) andcommunity change rate () in the river. Inthe lake, phytoplankton had an autogenicsuccessional sequence during the isolation phase (C-to S-strategists) and other responses todisturbance, mainly during the flood(R-strategists). Frequent changes in phytoplanktoncomposition, biomass, H, E and , revealed aenvironmental instability in the lake, which may beexplained by interactions of external factors(hydrology and climatology) and those of internalorigin, such as nutrients and grazing. 相似文献
25.
Summary Observations in a family point to the existence of autosomal dominant inheritance for discrete subaortic stenosis (DSS), which made up part of a multisystem disorder. Both parents, offspring of two full siblings, had short stature, obstructive lung disease (OLD), hoarseness and upturned nose. The father alone had aortic stenosis and inguinal hernia.The six offspring, aged from 13 to 28 years, were followed up for up to 8 years. While one of them was virtually normal, and one had only minor abnormalities, four siblings displayed clinical signs of progressive aortic stenosis. Of the two eldest siblings who eventually died, necropsy in one showed a discrete subaortic stenosis, which was hemodynamically proven in one and surgically corrected in another sibling.Upturned nose was present in each examined member of the family, short stature and hoarseness in five of the siblings, DSS in four, OLD, inguinal hernia and congested episcleral veins in three, kyphoscoliosis in two, while epicanthus, strabismus, microphthalmos and widely spaced teeth were noted in the deceased female. The prevalence of some of these traits in roughly three-quarters of the sibship was consistent with an underlying single gene abnormality in affected heterozygous parents. We proposed that this constitutes a new syndrome. 相似文献
26.
Dinoflagellate chromosomes observed in thin section show regular patterns which have been shown to correspond to a liquid crystalline helicoidal arrangement of DNA. Peripheral DNA filaments form a system of loops in the surrounding nucleoplasm. When such chromosomes (studied in Prorocentrum micans) are in presence of water, they extend considerably and form a double helical bundle. At the periphery of these bundles, one observes numerous filaments, which are smooth and devoid of nucleosomes; their diameter is constant.This study, in phase contrast and in electron microscopy, allows statistical measurements. A geometrical model is proposed and shows the simplest way to pass from the intact to the extended form. The liquid crystalline character of the chromosome is probably involved in the extension mechanisms. 相似文献
27.
Achiléa Lisboa Bittencourt Maria das Graças Santana Araujo Maria do Socorro Fontoura Paes 《Mycopathologia》1980,71(3):155-158
A case of a two-year-old boy with multiple subcutaneous lesions caused by Basidiobolus haptosporus is presented.The child had also a non-toxic familial goiter and clinical and radiological features of a pulmonary illness. The pulmonary manifestations only disappeared with the treatment with potassium iodide. The authors think that the pulmonary lesions must have arisen by direct spread of the fungus from the subcutaneous lesions of the chest. 相似文献
28.
29.
Jean- -François Laliberté Olivier Nicolas Serge Durand Rolf Morosoli 《Plant molecular biology》1992,18(3):447-451
The xylanase gene from Cryptococcus albidus contains seven introns. Genomic and cDNA clones under the control of the CaMV 35S promoter were transferred into tobacco plants using Agrobacterium-mediated cell transformation. The genes were transcribed and the mRNAs were amplified by the polymerase chain reaction using primers on each side of the intron region. About 90% of the amplification products from plants transformed with the genomic clone corresponded to the size of the pre-mRNA (1.2 kb) and 10% represented the spliced product (0.85 kb). The 0.85 kb fragment was cloned and sequenced and the result indicated that the introns from the xylanase gene were accurately spliced by the plant cells. 相似文献
30.