全文获取类型
收费全文 | 2472篇 |
免费 | 171篇 |
国内免费 | 171篇 |
出版年
2023年 | 40篇 |
2022年 | 65篇 |
2021年 | 75篇 |
2020年 | 85篇 |
2019年 | 99篇 |
2018年 | 108篇 |
2017年 | 89篇 |
2016年 | 90篇 |
2015年 | 81篇 |
2014年 | 85篇 |
2013年 | 243篇 |
2012年 | 78篇 |
2011年 | 97篇 |
2010年 | 88篇 |
2009年 | 113篇 |
2008年 | 109篇 |
2007年 | 127篇 |
2006年 | 114篇 |
2005年 | 79篇 |
2004年 | 91篇 |
2003年 | 94篇 |
2002年 | 76篇 |
2001年 | 62篇 |
2000年 | 49篇 |
1999年 | 45篇 |
1998年 | 30篇 |
1997年 | 40篇 |
1996年 | 42篇 |
1995年 | 24篇 |
1994年 | 18篇 |
1993年 | 26篇 |
1992年 | 22篇 |
1991年 | 22篇 |
1990年 | 31篇 |
1989年 | 16篇 |
1988年 | 16篇 |
1987年 | 19篇 |
1986年 | 32篇 |
1985年 | 25篇 |
1984年 | 28篇 |
1983年 | 21篇 |
1982年 | 21篇 |
1981年 | 17篇 |
1980年 | 13篇 |
1979年 | 12篇 |
1978年 | 12篇 |
1976年 | 6篇 |
1975年 | 9篇 |
1974年 | 10篇 |
1973年 | 9篇 |
排序方式: 共有2814条查询结果,搜索用时 125 毫秒
101.
Hideo Otaki 《Marine and Freshwater Behaviour and Physiology》2013,45(4):195-269
Demersal fish resources in the East China and Yellow Seas were reviewed. A current and historical survey of the fishery was made. The distribution and migration of demersal fish were characterized, and an assessment of fishery resources was provided. The standardization of fishing efforts and resources management were also examined. 相似文献
102.
The East Aegean (East Aegean Islands, Greece and West Anatolia, Turkey) is a biogeographically transitional region, where biodiversity elements from Europe and Asia join. However, affinities in the region were until recently scarcely explored. We assess biogeographical affinities in the East Aegean focusing on distribution patterns of Lamiaceae plants in Chios Island and its adjacent Çe?me–Karaburun Peninsula. Detailed in-situ record was acquired for 48 native species. These were grouped based on their habitat and geological substrate preference, their distribution was mapped in grid cells and distribution patterns were analysed in relation to species groupings. In both Chios and Çe?me–Karaburun, species follow five distribution patterns: widespread, locally widespread, locally restricted, sporadic and rare. Fifty to 62% of the species exhibit similar distribution patterns, trends in habitat and geological substrate preference in Chios and Çe?me–Karaburun, results complying with previous evidence of close biogeographical affinities of the East Aegean Islands and neighbouring Anatolia. Differences observed between the two regions may be attributed to insularity effects, human impact and the melange, an old rock matrix known for its key role in elucidating regional geodynamic evolution. Distributions of widespread and locally widespread species in Chios give evidence of density compensation and niche shifts responses, however, the actual occurrence of these phenomena in island plant populations is still to be elucidated. Overall, the species distribution patterns, particularly those of rare ones, reflect the complex geological history, palaeogeography and human influence in the Aegean region. 相似文献
103.
《Expert review of proteomics》2013,10(1):113-126
Human and animal African trypanosomoses, or sleeping sickness and Nagana, are neglected vector-borne parasitic diseases caused by protozoa belonging to the Trypanosoma genus. Advances in proteomics offer new tools to better understand host–vector–parasite crosstalks occurring during the complex parasitic developmental cycle, and to determine the outcome of both transmission and infection. In this review, we summarize proteomics studies performed on African trypanosomes and on the interactions with their vector and mammalian hosts. We discuss the contributions and pitfalls of using diverse proteomics tools, and argue about the interest of pathogenoproteomics, both to generate advances in basic research on the best knowledge and understanding of host–vector–pathogen interactions, and to lead to the concrete development of new tools to improve diagnosis and treatment management of trypanosomoses in the near future. 相似文献
104.
H. F. Dallas 《African Journal of Aquatic Science》2013,38(1):79-94
Summary The rapid bioassessment method, SASS (South African Scoring System) has been developed to assess water quality in riverine ecosystems. It is a scoring system based on the presence or absence of macroinvertebrate groups, and yields three values, namely SASS4 Score, Number of Taxa and Average Score Per Taxon (ASPT). The current and future use of SASS, including incorporation into the National Biomonitoring Programme for Riverine Ecosystems, necessitates evaluation of this bioassessment method. This study focuses on three aspects. namely spatial variation in SASS scores, including regional and longitudinal (sub-regional) variation; temporal variation in SASS scores, and the effect of biotope availability on SASS scores. 相似文献
105.
Hassan Ashktorab Hamed Rahi Daniel Wansley Sudhir Varma Babak Shokrani Edward Lee Mohammad Daremipouran Adeyinka Laiyemo Ajay Goel John M Carethers Hassan Brim 《Epigenetics》2013,8(8):807-815
CpG Island Methylator Phenotype (CIMP) is one of the underlying mechanisms in colorectal cancer (CRC). This study aimed to define a methylome signature in CRC through a methylation microarray analysis and a compilation of promising CIMP markers from the literature. Illumina HumanMethylation27 (IHM27) array data was generated and analyzed based on statistical differences in methylation data (1st approach) or based on overall differences in methylation percentages using lower 95% CI (2nd approach). Pyrosequencing was performed for the validation of nine genes. A meta-analysis was used to identify CIMP and non-CIMP markers that were hypermethylated in CRC but did not yet make it to the CIMP genes’ list. Our 1st approach for array data analysis demonstrated the limitations in selecting genes for further validation, highlighting the need for the 2nd bioinformatics approach to adequately select genes with differential aberrant methylation. A more comprehensive list, which included non-CIMP genes, such as APC, EVL, CD109, PTEN, TWIST1, DCC, PTPRD, SFRP1, ICAM5, RASSF1A, EYA4, 30ST2, LAMA1, KCNQ5, ADHEF1, and TFPI2, was established. Array data are useful to categorize and cluster colonic lesions based on their global methylation profiles; however, its usefulness in identifying robust methylation markers is limited and rely on the data analysis method. We have identified 16 non-CIMP-panel genes for which we provide rationale for inclusion in a more comprehensive characterization of CIMP+ CRCs. The identification of a definitive list for methylome specific genes in CRC will contribute to better clinical management of CRC patients. 相似文献
106.
《Epigenetics》2013,8(4):503-512
The identification of genes that are differentially methylated in colorectal cancer (CRC) has potential value for both diagnostic and therapeutic interventions specifically in high-risk populations such as African Americans (AAs). However, DNA methylation patterns in CRC, especially in AAs, have not been systematically explored and remain poorly understood. Here, we performed DNA methylome profiling to identify the methylation status of CpG islands within candidate genes involved in critical pathways important in the initiation and development of CRC. We used reduced representation bisulfite sequencing (RRBS) in colorectal cancer and adenoma tissues that were compared with DNA methylome from a healthy AA subject’s colon tissue and peripheral blood DNA. The identified methylation markers were validated in fresh frozen CRC tissues and corresponding normal tissues from AA patients diagnosed with CRC at Howard University Hospital. We identified and validated the methylation status of 355 CpG sites located within 16 gene promoter regions associated with CpG islands. Fifty CpG sites located within CpG islands—in genes ATXN7L1 (2), BMP3 (7), EID3 (15), GAS7 (1), GPR75 (24), and TNFAIP2 (1)—were significantly hypermethylated in tumor vs. normal tissues (P < 0.05). The methylation status of BMP3, EID3, GAS7, and GPR75 was confirmed in an independent, validation cohort. Ingenuity pathway analysis mapped three of these markers (GAS7, BMP3 and GPR) in the insulin and TGF-β1 network—the two key pathways in CRC. In addition to hypermethylated genes, our analysis also revealed that LINE-1 repeat elements were progressively hypomethylated in the normal-adenoma-cancer sequence. We conclude that DNA methylome profiling based on RRBS is an effective method for screening aberrantly methylated genes in CRC. While previous studies focused on the limited identification of hypermethylated genes, ours is the first study to systematically and comprehensively identify novel hypermethylated genes, as well as hypomethylated LINE-1 sequences, which may serve as potential biomarkers for CRC in African Americans. Our discovered biomarkers were intimately linked to the insulin/TGF-B1 pathway, further strengthening the association of diabetic disorders with colon oncogenic transformation. 相似文献
107.
Maria D. Jackson Marshall K. Tulloch-Reid Norma McFarlane-Anderson Alexis Watson Vestra Seers Franklyn I. Bennett Brian Egleston Camille Ragin 《Genes & nutrition》2013,8(2):199-207
Little is known about the role of folate and polymorphisms associated with folate metabolism on prostate cancer risk in populations of African origin. We examined the relationship between serum folate and prostate cancer and whether any association was modified by genetic polymorphisms for folate metabolism. The study was case–control in design and consisted of 218 men 40–80 years old with newly diagnosed, histologically confirmed prostate cancer and 236 cancer-free men attending the same urology clinics in Jamaica, March 2005–July 2007. Serum folate was measured by an immunoassay method and genomic DNA evaluated for MTHR (C677T and A1298C), MTRR A66G, and MTR A2756G polymorphisms. Mean serum folate concentration was higher among cases (12.3 ± 4.1 nmol/L) than controls (9.7 ± 4.2 nmol/L). Serum folate concentration showed a positive association with prostate cancer (OR, 4.41; CI, 2.52–7.72 per 10 nmol/L) regardless of grade. No interactions were observed between genotype and folate concentration, but a weak gene effect was observed for MTHFR A1298C and low-grade prostate cancer. Larger studies to investigate the role of gene–gene/gene–diet interactions in Black men are needed. 相似文献
108.
Pioneer Taashwa Gamundani Kudzai Mpakairi Christopher Magadza Shakkie Kativu Elmon Dhlomo 《African Journal of Ecology》2020,58(3):432-445
Climate models project a hot and dry future for Southern Africa. In this research, Maximum Entropy was used to model the extent to which climate change, land cover and distance from water edges may influence current and future distribution of the African skimmer in the mid-Zambezi Valley. Global Biodiversity Information Facility data collected between the years 2000–2019 were used to develop the models. Three models were built: one for current distribution and two for future distribution under Representative Concentration Pathways (RCPs) 2.6 and 6.0. Results revealed that annual precipitation and distance from water edges were the most important predictors of habitat suitability for the African skimmer under current and future climate. Temperature and land cover were least important in explaining current and future distribution of the species. The RCP 2.6 predicted future decrease in suitable habitat for the African skimmer in the mid-Zambezi Valley, while RCP 6.0 predicted future increase in suitable habitat for the species. This research conclusively revealed that precipitation and distance from water edges were consistently key predictors of suitable habitat for the African skimmer. 相似文献
109.
Huiyun Li Ye Liu Sumei Chen Jiafu Jiang Aiping Song Weimin Fang Fadi Chen 《Phyton》2020,89(4):851-859
Black spot disease, caused by the necrotrophic fungus Alternaria
tenuissima (Fr.) Wiltsh (A. tenuissima), is considered a highly destructive disease
of Chrysanthemum (Chrysanthemum morifolium Ramat.). A set of 17 accessions
of commercial chrysanthemum cultivars were evaluated for resistance to A.
tenuissima by seedling artificial inoculation. It was found that the reaction of
the accessions to artificial inoculation ranged from resistant to highly susceptible.
Five varieties of chrysanthemum (‘Zhongshan Taogui’, ‘Jinba’, ‘Zhongshan Jinguan’, ‘Jinling Wanhuang’ and ‘Jinling Yangguang’) were resistant; two varieties
of chrysanthemum (‘Zhongshan Xinggui’ and ‘Zhongshan Jinkui’) were moderately resistant; and others were susceptible to various degrees, four varieties of
chrysanthemum (‘Zhongshan Zihe’, ‘Zhongshan Jiuhong’, ‘Zaoyihong’ and ‘Jinling Jiaohuang’) were highly susceptible, especially. Some leaf morphological features of two resistant and two highly susceptible cultivars were further researched.
Trichome density, length, height, gland size and stomata density were found to be
associated with plant passive resistance. Resistant varieties that were identified in
present study will be promising germplasm for exploitation of breeding programmes aimed at developing A. tenuissima-resistant cultivars and increasing
genetic diversity. 相似文献
110.
Priyanka Jha Swati Chahal Devendra Kumar Pandey Joginder Singh Ram Prasad Vijay Kumar 《Phyton》2020,89(4):779-794
The use of medicinal plants for different therapeutic values is well
documented in African continent. African diverse biodiversity hotspots provide
a wide range of endemic species, which ensures a potential medicinal value.
The feasible conservation approach and sustainable harvesting for the medicinal
species remains a huge challenge. However, conservation approach through different biotechnological tools such as micropropagation, somatic embryogenesis,
synthetic seed production, hairy root culture, molecular markers based study
and cryopreservation of endemic African medicinal species is much crucial. In
this review, an attempt has been made to provide different in vitro biotechnological approaches for the conservation of African medicinal species. The present
review will be helpful in further technology development and deciding the priorities at decision-making levels for in vitro conservation and sustainable use of
African medicinal species. 相似文献