全文获取类型
收费全文 | 800981篇 |
免费 | 90238篇 |
国内免费 | 1034篇 |
专业分类
892253篇 |
出版年
2016年 | 9009篇 |
2015年 | 13318篇 |
2014年 | 15514篇 |
2013年 | 21587篇 |
2012年 | 24675篇 |
2011年 | 25243篇 |
2010年 | 16855篇 |
2009年 | 15476篇 |
2008年 | 22206篇 |
2007年 | 23053篇 |
2006年 | 21791篇 |
2005年 | 20972篇 |
2004年 | 20980篇 |
2003年 | 19799篇 |
2002年 | 19397篇 |
2001年 | 34017篇 |
2000年 | 34414篇 |
1999年 | 27618篇 |
1998年 | 10006篇 |
1997年 | 10216篇 |
1996年 | 9625篇 |
1995年 | 9218篇 |
1994年 | 8865篇 |
1993年 | 8930篇 |
1992年 | 22857篇 |
1991年 | 22354篇 |
1990年 | 21865篇 |
1989年 | 21182篇 |
1988年 | 19784篇 |
1987年 | 18792篇 |
1986年 | 17805篇 |
1985年 | 17825篇 |
1984年 | 14784篇 |
1983年 | 12739篇 |
1982年 | 9879篇 |
1981年 | 9132篇 |
1980年 | 8382篇 |
1979年 | 14082篇 |
1978年 | 11489篇 |
1977年 | 10381篇 |
1976年 | 9732篇 |
1975年 | 11110篇 |
1974年 | 12152篇 |
1973年 | 11955篇 |
1972年 | 10880篇 |
1971年 | 10009篇 |
1970年 | 8528篇 |
1969年 | 8410篇 |
1968年 | 7668篇 |
1967年 | 6723篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
121.
Phylogenetic revision of Agapophytinae subf.n. (Diptera: Therevidae) based on molecular and morphological evidence 总被引:1,自引:0,他引:1
Shaun L. Winterton† Longlong Yang† Brian M. Wiegmann† David K. Yeates . 《Systematic Entomology》2001,26(2):173-211
Agapophytinae subf.n. is a highly diverse lineage of Australasian Therevidae, comprising eight described and two new genera: Agapophytus Guérin‐Méneville, Acupalpa Kröber, Acraspisa Kröber, Belonalys Kröber, Bonjeania Irwin & Lyneborg, Parapsilocephala Kröber, Acatopygia Kröber, Laxotela Winterton & Irwin, Pipinnipons gen.n. and Patanothrix gen.n. A genus‐level cladistic analysis of the subfamily was undertaken using sixty‐eight adult morphological characters and c. 1000 base pairs of the elongation factor‐1α (EF‐1α) protein coding gene. The morphological data partition produced three most parsimonious cladograms, whereas the molecular data partition gave a single most parsimonious cladogram, which did not match any of the cladograms found in the morphological analysis. The level of congruence between the data partitions was determined using the partition homogeneity test (HTF) and Wilcoxon signed ranks test. Despite being significantly incongruent in at least one of the incongruence tests, the partitions were combined in a simultaneous analysis. The combined data yielded a single cladogram that was better supported than that of the individual partitions analysed separately. The relative contributions of the data partitions to support for individual nodes on the combined cladogram were investigated using Partitioned Bremer Support. The level of support for many nodes on the combined cladogram was non‐additive and often greater than the sum of support for the respective nodes on individual partitions. This synergistic interaction between incongruent data partitions indicates a common phylogenetic signal in both partitions. It also suggests that criteria for partition combination based solely on incongruence may be misleading. The phylogenetic relationships of the genera are discussed using the combined data. A key to genera of Agapophytinae is presented, with genera diagnosed and figured. Two new genera are described: Patanothrix with a new species (Pat. skevingtoni) and Pat. wilsoni (Mann) transferred from Parapsilocephala, and Pipinnipons with a new species (Pip. kroeberi). Pipinnipons fascipennis (Kröber) is transferred from Squamopygia Kröber and Pip. imitans (Mann) is transferred from Agapophytus. Agapophytus bicolor (Kröber) is transferred from Parapsilocephala. Agapophytus varipennis Mann is synonymised with Aga. queenslandi Kröber and Aga. flavicornis Mann is synonymised with Aga. pallidicornis (Kröber). 相似文献
122.
123.
124.
Synaptonemal complexes and meiosis in myxomycetes 总被引:4,自引:0,他引:4
Synaptonemal complexes (SC) have been observed in spores 18–24 hr past cleavage in natural fruitings of Physarum cinereum, P. bogoriense, Hemitrichia stipitata, Tubifera ferruginosa, and Arcyria incarnata. Laboratory fruitings of Arcyria cinerea, Stemonitis herbatica, and a homothallic isolate of Physarum pusillum also have SC's present in spores during the same postcleavage period. The presence of these paired chromosomes of meiotic prophase in spores of species collected in nature and in a diversity of taxa suggests that the usual position of meiosis in Myxomycetes is inside the postcleavage spore. Criteria are proposed for evaluating the validity of the SC as an indicator of meiosis. 相似文献
125.
HIF-1 expression in healing wounds: HIF-1alpha induction in primary inflammatory cells by TNF-alpha 总被引:12,自引:0,他引:12
126.
The cell surface of the parasitic protozoan Leishmania mexicana is coated by glycosylphosphatidylinositol (GPI)-anchored glycoproteins, a GPI-anchored lipophosphoglycan and a class of free GPI glycolipids. To investigate whether the anchor or free GPIs are required for parasite growth we cloned the L.mexicana gene for dolichol-phosphate-mannose synthase (DPMS) and attempted to create DPMS knockout mutants by targeted gene deletion. DPMS catalyzes the formation of dolichol-phosphate mannose, the sugar donor for all mannose additions in the biosynthesis of both the anchor and free GPIs, except for a alpha1-3-linked mannose residue that is added exclusively to the free GPIs and lipophosphoglycan anchor precursors. The requirement for dolichol-phosphate-mannose in other glycosylation pathways in L.mexicana is minimal. Deletion of both alleles of the DPMS gene (lmdpms) consistently resulted in amplification of the lmdpms chromosomal locus unless the promastigotes were first transfected with an episomal copy of lmdpms, indicating that lmdpms, and possibly GPI biosynthesis, is essential for parasite growth. As evidence presented in this and previous studies indicates that neither GPI-anchored glycoproteins nor lipophosphoglycan are required for growth of cultured parasites, it is possible that the abundant and functionally uncharacterized free GPIs are essential membrane components. 相似文献
127.
The cellular long-chain component patterns of 33 strains of Eubacterium lentum were determined by gas chromatography. Two main types of long-chain component patterns were distinguished. The first (26 strains) was characterized by saturated branched-chain fatty acids (br14:0, br15:0, br16:0 and br17:0). The second (7 strains) did not contain branched-chain fatty acids and was characterized by saturated straight-chain fatty acids (11:0, 12:0, 14:0 and 16:0). Both types contained fatty aldehydes and their respective dimethyl acetals (14ald and 14dma, 16ald and 16dma). br16dma was only found in the first type. The G + C content of the DNA (Tm) of the 33 strains varied between 63.7 and 69.1 mol %. Canonical correlation analysis distinguished three subtypes within the first main type. 相似文献
128.
129.
L I Kulikova G A Iatskiavichiute V S Tsvetkov Iu E Ershikova S P Gordienko 《Biulleten' eksperimental'no? biologii i meditsiny》1987,104(8):224-226
Antibodies to calcitonin, parathyroid hormone and cortisol are detected in acute stage of infection-caused bronchial asthma. The appearance of antibodies is paralleled by marked hypercalcaemia. The antibodies may bind excessive hormones in the blood, preventing further hormonal imbalance. Ten-day treatment with glucocorticoids decreased the amount of antibodies possibly due to normalization of hormonal secretion and restoration of their balance. As a result, calcium blood levels returned to normal. 相似文献
130.