全文获取类型
收费全文 | 5375篇 |
免费 | 438篇 |
国内免费 | 2篇 |
专业分类
5815篇 |
出版年
2023年 | 43篇 |
2022年 | 111篇 |
2021年 | 182篇 |
2020年 | 85篇 |
2019年 | 101篇 |
2018年 | 135篇 |
2017年 | 98篇 |
2016年 | 208篇 |
2015年 | 294篇 |
2014年 | 324篇 |
2013年 | 391篇 |
2012年 | 448篇 |
2011年 | 466篇 |
2010年 | 282篇 |
2009年 | 255篇 |
2008年 | 294篇 |
2007年 | 310篇 |
2006年 | 276篇 |
2005年 | 236篇 |
2004年 | 230篇 |
2003年 | 200篇 |
2002年 | 173篇 |
2001年 | 41篇 |
2000年 | 27篇 |
1999年 | 39篇 |
1998年 | 54篇 |
1997年 | 40篇 |
1996年 | 29篇 |
1995年 | 31篇 |
1994年 | 25篇 |
1993年 | 26篇 |
1992年 | 24篇 |
1991年 | 15篇 |
1990年 | 20篇 |
1989年 | 19篇 |
1988年 | 14篇 |
1987年 | 11篇 |
1985年 | 15篇 |
1984年 | 19篇 |
1983年 | 15篇 |
1982年 | 18篇 |
1981年 | 22篇 |
1980年 | 23篇 |
1979年 | 19篇 |
1978年 | 23篇 |
1977年 | 15篇 |
1976年 | 9篇 |
1975年 | 8篇 |
1974年 | 10篇 |
1968年 | 8篇 |
排序方式: 共有5815条查询结果,搜索用时 15 毫秒
191.
192.
Vanessa Mendonça Diana Boaventura Henrique Cabral Ana C. F. Silva 《Marine Biology Research》2016,12(2):125-132
Chitons are very common molluscs on European rocky shores. They are common prey of fish and crabs and often display several colour morphs within a given habitat. Predation is one of the potential mechanisms accounting for chiton colour polymorphism. The colour variation is considered to provide a camouflage protection through a match with the substratum surface typology. However, the effectiveness of chiton polymorphism as a predation defence requires further investigation. Previously we found a relationship between chiton colour morphs and substrate characteristics, with chitons most commonly found on substrates that were of similar colour to their shells. Here, we examined whether each morph displayed an active choice for matching the substratum. Next, we assessed if the predation success of the intertidal common crab Carcinus maenas varied significantly with the absence/presence of an apparent camouflage effect created between the chiton colour morph and the substratum type. The present study indicates that chiton colour morphs probably actively choose substratum types where they blend in. Carcinus maenas was able to prey on all Lepidochitona cinereus colour morphs, regardless of the substrate camouflage effect. Surprisingly, the predation frequency was higher on camouflaged chitons than on contrasting chitons. It was concluded that chiton camouflage is probably not a defence mechanism against predation by the crab C. maenas, and that chiton colour polymorphism is probably promoted by other, more visual predators. 相似文献
193.
Diana Vilas Boas Carina Almeida Sanna Sillankorva Ana Nicolau Joana Azeredo 《Biofouling》2016,32(2):179-190
Bacteriophage–host interaction studies in biofilm structures are still challenging due to the technical limitations of traditional methods. The aim of this study was to provide a direct fluorescence in situ hybridization (FISH) method based on locked nucleic acid (LNA) probes, which targets the phage replication phase, allowing the study of population dynamics during infection. Bacteriophages specific for two biofilm-forming bacteria, Pseudomonas aeruginosa and Acinetobacter, were selected. Four LNA probes were designed and optimized for phage-specific detection and for bacterial counterstaining. To validate the method, LNA-FISH counts were compared with the traditional plaque forming unit (PFU) technique. To visualize the progression of phage infection within a biofilm, colony-biofilms were formed and infected with bacteriophages. A good correlation (r = 0.707) was observed between LNA-FISH and PFU techniques. In biofilm structures, LNA-FISH provided a good discrimination of the infected cells and also allowed the assessment of the spatial distribution of infected and non-infected populations. 相似文献
194.
Mark R. Westmoreland Diana K. Allan 《Visual Anthropology: Published in cooperation with the Commission on Visual Anthropology》2016,29(3):205-210
Five years ago images from the Arab uprisings revealed a renewed investment in political visibility. Despite the brutal outcome of most of these revolts, the centrality of seeing for understanding the dynamics of political vision and struggle in the region remains salient. Images serve as important touchstones around which political narratives emerge and cohere. In this special issue on Visual Revolutions in the Middle East, seven scholars— Diana K. Allan, Zeynep Devrim Gürsel, Alisa Lebow, Peter Limbrick, Anjali Nath, Peter Snowdon and Mark R. Westmoreland—bring interdisciplinary attention to the generative possibilities of image-making in sites of political contestation. Whether through archival remnants, mobile screen technologies or the lens of a camera, the contributors to this collection explore the image as an agent of expression, engagement and critique, operating at the interface between political desires and evidentiary forms of visuality. 相似文献
195.
196.
Mariona Guitart‐Mampel Diana L. Juarez‐Flores Lina Youssef Constanza Moren Laura Garcia‐Otero Vicente Roca‐Agujetas Marc Catalan‐Garcia Ingrid Gonzalez‐Casacuberta Ester Tobias Jos C. Milisenda Josep M. Grau Ftima Crispi Eduard Gratacos Francesc Cardellach Glria Garrabou 《Journal of cellular and molecular medicine》2019,23(6):3962-3973
Intrauterine growth restriction (IUGR) is an obstetric complication characterised by placental insufficiency and secondary cardiovascular remodelling that can lead to cardiomyopathy in adulthood. Despite its aetiology and potential therapeutics are poorly understood, bioenergetic deficits have been demonstrated in adverse foetal and cardiac development. We aimed to evaluate the role of mitochondria in human pregnancies with IUGR. In a single‐site, cross‐sectional and observational study, we included placenta and maternal peripheral and neonatal cord blood mononuclear cells (PBMC and CBMC) from 14 IUGR and 22 control pregnancies. The following mitochondrial measurements were assessed: enzymatic activities of mitochondrial respiratory chain (MRC) complexes I, II, IV, I + III and II + III, oxygen consumption (cell and complex I‐stimulated respiration), mitochondrial content (citrate synthase [CS] activity and mitochondrial DNA copy number), total ATP levels and lipid peroxidation. Sirtuin3 expression was evaluated as a potential regulator of bioenergetic imbalance. Intrauterine growth restriction placental tissue showed a significant decrease of MRC CI enzymatic activity (P < 0.05) and CI‐stimulated oxygen consumption (P < 0.05) accompanied by a significant increase of Sirtuin3/β‐actin protein levels (P < 0.05). Maternal PBMC and neonatal CBMC from IUGR patients presented a not significant decrease in oxygen consumption (cell and CI‐stimulated respiration) and MRC enzymatic activities (CII and CIV). Moreover, CS activity was significantly reduced in IUGR new‐borns (P < 0.05). Total ATP levels and lipid peroxidation were preserved in all the studied tissues. Altered mitochondrial function of IUGR is especially present at placental and neonatal level, conveying potential targets to modulate obstetric outcome through dietary interventions aimed to regulate Sirtuin3 function. 相似文献
197.
Diana Y. Sakae Lauriane Ramet Annabelle Henrion Odile Poirel Stphane Jamain Salah El Mestikawy Stphanie Daumas 《Genes, Brain & Behavior》2019,18(3)
The atypical vesicular glutamate transporter VGLUT3 is present in subpopulations of GABAergic interneurons in the cortex and the hippocampus, in subgroups of serotoninergic neurons in raphe nuclei, and in cholinergic interneurons in the striatum. C56BL/6N mice that no longer express VGLUT3 (VGLUT3?/?) display anxiety‐associated phenotype, increased spontaneous and cocaine‐induced locomotor activity and decreased haloperidol‐induced catalepsy. Inbred mouse strains differ markedly in their sensitivity to anxiety and behavioral responses elicited by drugs. The purpose of this study was to investigate strain differences in VGLUT3 expression levels and its potential correlates with anxiety and reward‐guided behaviors. Five inbred mouse lines were chosen according to their contrasted anxiety and drugs sensitivity: C57BL/6N, C3H/HeN, DBA/2J, 129/Sv, and BALB/c. VGLUT3 protein expression was measured in different brain areas involved in reward or mood regulation (such as the striatum, the hippocampus, and raphe nuclei) and genetic variations in Slc17a8, the gene encoding for VGLUT3, have been explored. These five inbred mouse strains express very different levels of VGLUT3, which cannot be attributed to the genetic variation of the Slc17a8 locus. Furthermore, mice behavior in the open field, elevated plus maze, spontaneous‐ and cocaine‐induced locomotor was highly heterogeneous and only partially correlated to VGLUT3 levels. These data highlight the fact that one single gene polymorphism could not account for VGLUT3 expression variations, and that region specific VGLUT3 expression level variations might play a key role in the modulation of discrete behaviors. 相似文献
198.
Roger T. Chetelat Xiaoqiong Qin Meilian Tan Diana Burkart‐Waco Yosuke Moritama Xiuwen Huo Tim Wills Ricardo Pertuz 《The Plant journal : for cell and molecular biology》2019,100(4):836-850
The wild tomato relative Solanum sitiens is a xerophyte endemic to the Atacama Desert of Chile and a potential source of genes for tolerance to drought, salinity and low‐temperature stresses. However, until recently, strong breeding barriers prevented its hybridization and introgression with cultivated tomato, Solanum lycopersicum L. We overcame these barriers using embryo rescue, bridging lines and allopolyploid hybrids, and synthesized a library of introgression lines (ILs) that captures the genome of S. sitiens in the background of cultivated tomato. The IL library consists of 56 overlapping introgressions that together represent about 93% of the S. sitiens genome: 65% in homozygous and 28% in heterozygous (segregating) ILs. The breakpoints of each segment and the gaps in genome coverage were mapped by single nucleotide polymorphism (SNP) genotyping using the SolCAP SNP array. Marker‐assisted selection was used to backcross selected introgressions into tomato, to recover a uniform genetic background, to isolate recombinant sub‐lines with shorter introgressions and to select homozygous genotypes. Each IL contains a single S. sitiens chromosome segment, defined by markers, in the genetic background of cv. NC 84173, a fresh market inbred line. Large differences were observed between the lines for both qualitative and quantitative morphological traits, suggesting that the ILs contain highly divergent allelic variation. Several loci contributing to unilateral incompatibility or hybrid necrosis were mapped with the lines. This IL population will facilitate studies of the S. sitiens genome and expands the range of genetic variation available for tomato breeding and research. 相似文献
199.
Clara Ins Ortiz‐Ramírez Marco A. Giraldo Cristina Ferrndiz Natalia Pabn‐Mora 《The Plant journal : for cell and molecular biology》2019,99(4):686-702
The genetic mechanisms underlying fruit development have been identified in Arabidopsis and have been comparatively studied in tomato as a representative of fleshy fruits. However, comparative expression and functional analyses on the bHLH genes downstream the genetic network, ALCATRAZ (ALC) and SPATULA (SPT), which are involved in the formation of the dehiscence zone in Arabidopsis, have not been functionally studied in the Solanaceae. Here, we perform detailed expression and functional studies of ALC/SPT homologs in Nicotiana obtusifolia with capsules, and in Capsicum annuum and Solanum lycopersicum with berries. In Solanaceae, ALC and SPT genes are expressed in leaves, and all floral organs, especially in petal margins, stamens and carpels; however, their expression changes during fruit maturation according to the fruit type. Functional analyses show that downregulation of ALC/SPT genes does not have an effect on gynoecium patterning; however, they have acquired opposite roles in petal expansion and have been co‐opted in leaf pigmentation in Solanaceae. In addition, ALC/SPT genes repress lignification in time and space during fruit development in Solanaceae. Altogether, some roles of ALC and SPT genes are different between Brassicaceae and Solanaceae; while the paralogs have undergone some subfunctionalization in the former they are mostly redundant in the latter. 相似文献
200.
Iyll‐Joon Doh Jennifer Sturgis Diana V. Sarria Zuniga Robert E. Pruitt J. Paul Robinson Euiwon Bae 《Journal of biophotonics》2019,12(12)
The forward elastic‐light‐scattering pattern of a bacterial colony reflects its morphological characteristics. Three bacteria genera whose colonies having convex, crateriform, or irregular elevation were investigated to study the correlation between the morphology and the scattering pattern of the colony. The difference in the colony elevation produced distinct shapes of light diffraction in the scattering pattern, resulting circular diffraction rings or scattered light. Further details can be found in the article by Iyll‐Joon Doh, Jennifer Sturgis, Diana V. Sarria Zuniga, et al. ( e201900149 ).