全文获取类型
收费全文 | 5341篇 |
免费 | 477篇 |
国内免费 | 2篇 |
专业分类
5820篇 |
出版年
2023年 | 35篇 |
2022年 | 105篇 |
2021年 | 181篇 |
2020年 | 117篇 |
2019年 | 131篇 |
2018年 | 145篇 |
2017年 | 129篇 |
2016年 | 208篇 |
2015年 | 312篇 |
2014年 | 353篇 |
2013年 | 408篇 |
2012年 | 460篇 |
2011年 | 409篇 |
2010年 | 299篇 |
2009年 | 223篇 |
2008年 | 361篇 |
2007年 | 317篇 |
2006年 | 284篇 |
2005年 | 264篇 |
2004年 | 209篇 |
2003年 | 185篇 |
2002年 | 154篇 |
2001年 | 61篇 |
2000年 | 52篇 |
1999年 | 59篇 |
1998年 | 37篇 |
1997年 | 24篇 |
1996年 | 18篇 |
1995年 | 11篇 |
1994年 | 20篇 |
1993年 | 10篇 |
1992年 | 25篇 |
1991年 | 22篇 |
1990年 | 20篇 |
1989年 | 20篇 |
1988年 | 22篇 |
1987年 | 16篇 |
1986年 | 10篇 |
1985年 | 19篇 |
1984年 | 11篇 |
1983年 | 12篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 11篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1968年 | 3篇 |
1967年 | 3篇 |
排序方式: 共有5820条查询结果,搜索用时 0 毫秒
1.
Alicia A. Gil de Pertierra 《Zoologischer Anzeiger》2005,243(4):307-304
The surface of the tegument of the scolex and the immature proglottides of Monticellia belavistensis, M. ventrei, Nomimoscolex chubbi, and N. lopesi is described using scanning electron microscopy. Only blade-like spiniform microtriches and filiform microtriches were observed in the species studied. The types, size and density of microtriches on the apical region surface of the scolex, central cavity surface of suckers, marginal ring surface of suckers, non-adherent surface of suckers, proliferation zone surface, and immature proglottis surface were compared among these species. The distribution pattern of the microtriches was not a reliable feature to discriminate among the genera considered in this study. It varied in each of the species of Monticellia examined, and did not permit to split the heterogeneous genus Nomimoscolex. However, the microthrix pattern can be regarded as an additional diagnostic feature to distinguish among species of proteocephalideans. Further comparative research involving other species of proteocephalid taxa is needed to elucidate the systematic value of the tegumental morphology. 相似文献
2.
We have compared the species richness of medicinal plants and the differential patterns of use amongst settlements in the
Andean communities of Northwest Argentina which have differing levels of isolation. About 259 ethnoespecies, belonging to
74 plant families, were included, representing between 70 and 80% of the total estimate. The results indicate that Coronopus didymus is the most relevant and important species. The method of use of medicinal plants and the ailments treated by rural doctors compared to those of the layperson is different. Native and exotic plants are used differently according to the body system
treated. There are some relationships between internal and external use and body systems and recipes. The greater medicinal
species richness found in the less isolated locations is due to external enriching cultural influences. 相似文献
3.
4.
5.
The phytophagous fruit fly Rhagoletis meigenii harbors the bacterium Wolbachia pipientis and, together with Japanese barberry, form a tri-partite symbiosis. R. meigenii is a seed predator of invasive Japanese barberry plants and is dependent on this insect-plant interaction for reproductive success. The endosymbiotic bacterium W. pipientis is a reproductive parasite known to alter the sex ratios of offspring and the fitness of infected host insects. We investigated Japanese barberry fruit for the degree of infestation by R. meigenii and characterized the Wolbachia strain infecting R. meigenii. Densities of R. meigenii in four naturalized stands of Japanese barberry revealed low numbers of fruit flies with high variability in the population densities observed among individual plants. Overall, R. meigenii infested roughly 10–20 % of the Japanese barberry fruits analyzed; fruit with two seeds (vs. one seed) were the most frequently infested. Approximately, 90 % of the R. meigenii tested positive for Wolbachia infection via PCR amplification of the Wolbachia surface protein (wsp) gene. No bacterial strain diversity was observed when comparing multi-locus sequence typing (MLST) profiles within or among five R. meigenii populations in Maine, although the MLST profile obtained from R. meigenii differed from three co-occurring Rhagoletis. The Wolbachia endosymbiont of R. meigenii is a member of the Wolbachia supergroup A and the ST-13 cluster complex. 相似文献
6.
Dominique Dorin-Semblat Claudia Demarta-Gatsi Romain Hamelin Florence Armand Teresa Gil Carvalho Marc Moniatte Christian Doerig 《PloS one》2015,10(12)
Casein kinase 1 (CK1) is a pleiotropic protein kinase implicated in several fundamental processes of eukaryotic cell biology. Plasmodium falciparum encodes a single CK1 isoform, PfCK1, that is expressed at all stages of the parasite’s life cycle. We have previously shown that the pfck1 gene cannot be disrupted, but that the locus can be modified if no loss-of-function is incurred, suggesting an important role for this kinase in intra-erythrocytic asexual proliferation. Here, we report on the use of parasite lines expressing GFP- or His-tagged PfCK1 from the endogenous locus to investigate (i) the dynamics of PfCK1 localisation during the asexual cycle in red blood cells, and (ii) potential interactors of PfCK1, so as to gain insight into the involvement of the enzyme in specific cellular processes. Immunofluorescence analysis reveals a dynamic localisation of PfCK1, with evidence for a pool of the enzyme being directed to the membrane of the host erythrocyte in the early stages of infection, followed by a predominantly intra-parasite localisation in trophozoites and schizonts and association with micronemes in merozoites. Furthermore, we present strong evidence that a pool of enzymatically active PfCK1 is secreted into the culture supernatant, demonstrating that PfCK1 is an ectokinase. Our interactome experiments and ensuing kinase assays using recombinant PfCK1 to phosphorylate putative interactors in vitro suggest an involvement of PfCK1 in many cellular processes such as mRNA splicing, protein trafficking, ribosomal, and host cell invasion. 相似文献
7.
8.
J Ignacio Andrés Jesús Alcázar José M Alonso Adolfo Díaz Javier Fernández Pilar Gil Laura Iturrino Encarna Matesanz Theo F Meert Anton Megens Victor K Sipido 《Bioorganic & medicinal chemistry letters》2002,12(2):249-253
Following the programme started at Janssen Research Foundation searching for 5-HT(2A/2C) antagonists, we now report on the synthesis of a series of substituted 2-(Dimethylaminomethyl)-2,3,3a,8-tetrahydrodibenzo[c,f]isoxazolo[2,3-a]azepine derivatives. The 5-HT(2A), 5-HT(2C) and H(1) receptor affinities as well as the mCPP antagonistic activity of the compounds synthesised is described. 相似文献
9.
10.