全文获取类型
收费全文 | 13806篇 |
免费 | 935篇 |
专业分类
14741篇 |
出版年
2024年 | 17篇 |
2023年 | 126篇 |
2022年 | 243篇 |
2021年 | 464篇 |
2020年 | 294篇 |
2019年 | 369篇 |
2018年 | 454篇 |
2017年 | 473篇 |
2016年 | 581篇 |
2015年 | 873篇 |
2014年 | 860篇 |
2013年 | 1036篇 |
2012年 | 1204篇 |
2011年 | 1102篇 |
2010年 | 680篇 |
2009年 | 592篇 |
2008年 | 748篇 |
2007年 | 710篇 |
2006年 | 615篇 |
2005年 | 519篇 |
2004年 | 469篇 |
2003年 | 443篇 |
2002年 | 396篇 |
2001年 | 204篇 |
2000年 | 155篇 |
1999年 | 134篇 |
1998年 | 108篇 |
1997年 | 67篇 |
1996年 | 67篇 |
1995年 | 51篇 |
1994年 | 39篇 |
1993年 | 38篇 |
1992年 | 53篇 |
1991年 | 36篇 |
1990年 | 67篇 |
1989年 | 23篇 |
1988年 | 37篇 |
1987年 | 30篇 |
1986年 | 28篇 |
1985年 | 26篇 |
1984年 | 32篇 |
1983年 | 28篇 |
1982年 | 18篇 |
1981年 | 29篇 |
1980年 | 13篇 |
1979年 | 23篇 |
1978年 | 19篇 |
1977年 | 12篇 |
1975年 | 15篇 |
1974年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Eder Jorge de Oliveira Vanusia Batista Oliveira Amorim Edneide Luciana Santiago Matos Juliana Leles Costa Milene da Silva Castellen Juliano Gomes Pádua Jorge Luiz Loyola Dantas 《Plant Molecular Biology Reporter》2010,28(3):519-530
A set of 81 new microsatellite markers for Carica papaya L. previously identified by data mining using freely available sequence information from Genbank were tested for polymorphism
using 30 germplasm accessions from the Papaya Germplasm Bank (PGM) at Embrapa Mandioca e Fruticultura Tropical (CNPMF) and
18 landraces. The data were used to estimate pairwise genetic distances between the genotypes. A neighbor-joining based dendrogram
was used to define clusters and infer possible genetic structuring of the collection. Most microsatellites were polymorphic
(73%), with an observed number of alleles per locus ranging from one to eleven. The levels of observed and expected heterozygosity
for 51 polymorphic loci varied from 0.00 to 0.85 and from 0.08 to 0.82, averaging 0.19 and 0.59, respectively. Forty-four
percent of microsatellites showed polymorphism information content (PIC) higher than 0.50. The compound microsatellites seem
to be more informative than dinucleotide and trinucleotide repeats in average alleles per locus and PIC. Among dinucleotides,
AG/TC or GA/CT repeat motifs exhibited more informativeness than TA/AT, GT/CA and TG/AC repeat motifs. The neighbor-joining
analysis based on shared allele distance could differentiate all the papaya accessions and landraces as well as differences
in their genetic structure. This set of markers will be useful for examining parentage, inbreeding and population structure
in papaya. 相似文献
962.
963.
Adriano Caliman Aliny F. Pires Francisco A. Esteves Reinaldo L. Bozelli Vinicius F. Farjalla 《Biodiversity and Conservation》2010,19(3):651-664
The sub-discipline of biodiversity and ecosystem functioning (BEF) has emerged as a central topic in contemporary ecological
research. However, to date no study has evaluated the prominence and publication biases in BEF research. Herein we report
the results of a careful quantitative assessment of BEF research published in five core general ecology journals from 1990
to 2007 to determine the position of BEF research within ecology, identify patterns of research effort within BEF research,
and discuss their probable proximal and historical causes. The relative importance of BEF publications increased exponentially
during the period analyzed and was significantly greater than the average growth of ecological literature, affirming the prominence
of BEF as a current paradigm in ecology. However, BEF research exhibited a strong bias toward experimental studies on terrestrial
plant communities, with significantly lower effort devoted to the functional aspects of biodiversity in aquatic systems, multiple
trophic level systems, and animal or microbial communities. Such trends may be explained by a combination of methodological
adequacy and historic epistemological differences in ecological thinking. We suggest that BEF researchers should direct more
effort toward the study of aquatic systems and animal communities, emphasize long-term and trophically complex experiments,
such as those with multi-trophic microbial communities, employ larger-scale field observational studies and increase the use
of integrative and theoretical studies. Many technical and analytical methodologies that are already employed in ecological
research, such as stable isotopes, paleobiology, remote sensing, and model selection criteria, can facilitate these aims.
Overcoming the above-mentioned shortcomings of current BEF research will greatly improve our ability to predict how biodiversity
loss will affect ecosystem processes and services in natural ecosystems. 相似文献
964.
Matthew G. Stanton Jed Hubbs David Sloman Christopher Hamblett Paula Andrade Minilik Angagaw Grace Bi Regina M. Black Jamie Crispino Jonathan C. Cruz Eric Fan Georgia Farris Bethany L. Hughes Candia M. Kenific Richard E. Middleton George Nikov Peter Sajonz Sanjiv Shah Nirah Shomer Alexander A. Szewczak Benito Munoz 《Bioorganic & medicinal chemistry letters》2010,20(2):755-758
We report herein a novel series of difluoropiperidine acetic acids as modulators of γ-secretase. Synthesis of 2-aryl-3,3-difluoropiperidine analogs was facilitated by a unique and selective β-difluorination with Selectfluor®. Compounds 1f and 2c were selected for in vivo assessment and demonstrated selective lowering of Aβ42 in a genetically engineered mouse model of APP processing. Moreover, in a 7-day safety study, rats treated orally with compound 1f (250 mg/kg per day, AUC0–24 = 2100 μM h) did not exhibit Notch-related effects. 相似文献
965.
Felipe F.D. Oliveira Diego C.B.D. Santos Alexandre A.M. Lapis José R. Corrêa Alexandre F. Gomes Fabio C. Gozzo Paulo F. Moreira Virgínia C. de Oliveira Frank H. Quina Brenno A.D. Neto 《Bioorganic & medicinal chemistry letters》2010,20(20):6001-6007
Newly designed 2,1,3-benzothiadiazole-containing fluorescent probes with four excited state intramolecular proton transfer (ESIPT) sites were successfully tested in live cell-imaging assays using a confluent monolayer of human stem-cells (tissue). All tested dyes were compared with the commercially available DAPI and gave far better results. 相似文献
966.
967.
968.
Toyama MH Toyama DO Torres VM Pontes GC Farias WR Melo FR Oliveira SC Fagundes FH Diz Filho EB Cavada BS 《The protein journal》2010,29(8):567-571
Low molecular weight fragments of sulfated galactans (Boc-5 and Boc-10) from the red algae Botryocladia occidentalis significantly inhibited Crotalus durissus cascavella sPLA2 enzymatic activity. Equimolar ratios of sPLA2 to Boc-5 or Boc-10 resulted in allosteric inhibition of sPLA2. Under
the conditions tested, we observed that both Boc-5 and Boc-10 strongly decreased edema, myonecrosis, and neurotoxicity induced
by native sPLA2. 相似文献
969.
Ivane Abiatari Irene Esposito Tiago De Oliveira Klaus Felix Hong Xin Roland Penzel Thomas Giese Helmut Friess Jörg Kleeff 《Journal of cellular and molecular medicine》2010,14(5):1166-1179
Cell motility is controlled by the dynamic cytoskeleton and its related proteins, such as members of the ezrin/radixin/moesin (ERM) family, which act as signalling molecules inducing cytoskeleton remodelling. Although ERM proteins have been identified as important factors in various malignancies, functional redundancy between these proteins has hindered the dissection of their individual contribution. The aim of the present study was to analyse the functional role of moesin in pancreatic malignancies. Cancer cells of different malignant lesions of human and transgenic mice pancreata were evaluated by immunohistochemistry. For functional analysis, cell growth, adhesion and invasion assays were carried out after transient and stable knock‐down of moesin expression in pancreatic cancer cells. In vivo tumourigenicity was determined using orthotopic and metastatic mouse tumour models. We now show that moesin knock‐down increases migration, invasion and metastasis and influences extracellular matrix organization of pancreatic cancer. Moesin‐regulated migratory activities of pancreatic cancer cells were in part promoted through cellular translocation of β‐catenin, and re‐distribution and organization of the cytoskeleton. Analysis of human and different transgenic mouse pancreatic cancers demonstrated that moesin is a phenotypic marker for anaplastic carcinoma, suggesting that this ERM protein plays a specific role in pancreatic carcinogenesis. 相似文献
970.
Cybele Esteves Almeida Barbara Charlotte Bach Maristela Lovato Flores Rogério Pereira Fontoura Stefanie Dickel Segabinazi Marta Helena Carlesso Aita 《European Journal of Wildlife Research》2010,56(1):101-104
Serum proteins from 47 healthy greater rheas (Rhea americana; male and female) were separated by electrophoresis in order to characterize normal reference ranges. Determination of total
protein concentration was performed through biuret reaction. The mean value of total serum protein was 4.4 g/dL. Absolute
concentrations of serum proteins were determined by agarose gel electrophoretic fractioning. Five fractions were analyzed:
albumin, alpha, beta1, beta2, and gamma globulins, and the average values in grams per deciliter were 2.39, 0.32, 0.45, 0.30,
and 0.79, respectively. 相似文献