全文获取类型
收费全文 | 121746篇 |
免费 | 2649篇 |
国内免费 | 2793篇 |
出版年
2024年 | 53篇 |
2023年 | 387篇 |
2022年 | 1010篇 |
2021年 | 1709篇 |
2020年 | 1039篇 |
2019年 | 1345篇 |
2018年 | 12817篇 |
2017年 | 11339篇 |
2016年 | 8520篇 |
2015年 | 2427篇 |
2014年 | 2479篇 |
2013年 | 2752篇 |
2012年 | 6865篇 |
2011年 | 15048篇 |
2010年 | 13251篇 |
2009年 | 9365篇 |
2008年 | 11157篇 |
2007年 | 12553篇 |
2006年 | 1395篇 |
2005年 | 1431篇 |
2004年 | 1742篇 |
2003年 | 1672篇 |
2002年 | 1363篇 |
2001年 | 788篇 |
2000年 | 628篇 |
1999年 | 506篇 |
1998年 | 276篇 |
1997年 | 314篇 |
1996年 | 301篇 |
1995年 | 282篇 |
1994年 | 260篇 |
1993年 | 208篇 |
1992年 | 296篇 |
1991年 | 222篇 |
1990年 | 158篇 |
1989年 | 158篇 |
1988年 | 110篇 |
1987年 | 98篇 |
1986年 | 60篇 |
1985年 | 68篇 |
1984年 | 36篇 |
1983年 | 49篇 |
1982年 | 20篇 |
1981年 | 15篇 |
1980年 | 13篇 |
1972年 | 246篇 |
1971年 | 274篇 |
1965年 | 13篇 |
1962年 | 24篇 |
1944年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Swertia tetraptera Maxim is an annual alpine herb endemic to the Qinghai-Tibetan Plateau (QTP). Its populations are locally scattered as isolated patches throughout this region. Genetic variation within and among thirty-four populations of this species was assessed using ISSR fingerprinting with 10 primers. High levels of genetic diversity exist within species (P = 98.9%, I = 0.3475; He = 0.2227), while the within-population diversity is low (P = 32.7%, I = 0.177; He = 0.12). High levels of genetic differentiation were detected among populations based on various statistics, including Nei’s genetic diversity analysis (GST = 0.4608), Bayesian analysis (θB = 0.476) and AMOVA (FST = 0.57). That is, populations shared low levels of genetic identity (I = 0.2622–0.0966). This genetic structure was probably due to severe genetic drift, breeding system and limited gene flow. The observed genetic structure of the populations implies that different populations across the distribution range of the species should be sampled to maintain high genetic diversity when a conservation strategy is implemented. 相似文献
142.
This editorial addresses the debate concerning the origin of adult nucleus pulposus cells in the light of profiling studies
by Minogue and colleagues. In their report of several marker genes that distinguish nucleus pulposus cells from other related
cell types, the authors provide novel insights into the notochordal nature of the former. Together with recently published
work, their work lends support to the view that all cells present within the nucleus pulposus are derived from the notochord.
Hence, the choice of an animal model for disc research should be based on considerations other than the cell loss and replacement
by non-notochordal cells. 相似文献
143.
144.
Kevin B. Potts 《Journal of Mammalian Evolution》2010,17(3):221-222
145.
146.
147.
Background
Arsenic contamination is widespread throughout the world and this toxic metalloid is known to cause cancers of organs such as liver, kidney, skin, and lung in human. In spite of a recent surge in arsenic related studies, we are still far from a comprehensive understanding of arsenic uptake, detoxification, and sequestration in plants. Crambe abyssinica, commonly known as 'abyssinian mustard', is a non-food, high biomass oil seed crop that is naturally tolerant to heavy metals. Moreover, it accumulates significantly higher levels of arsenic as compared to other species of the Brassicaceae family. Thus, C. abyssinica has great potential to be utilized as an ideal inedible crop for phytoremediation of heavy metals and metalloids. However, the mechanism of arsenic metabolism in higher plants, including C. abyssinica, remains elusive. 相似文献148.
Yuanshan Yao Qingwang Hua Yinjie Zhou 《Biochemical and biophysical research communications》2019,508(1):37-45
Recently, circular RNAs (circRNAs) are identified as a novel class of noncoding RNAs playing important roles in human malignant tumors. However, the regulatory function of circRNA in lung adenocarcinoma (LUAD) is still largely unknown. Present study aimed to explore the role of circ_0006427 in LUAD progression. Firstly, the downregulation of circ_0006427 in LUAD tissues and cell lines was revealed by microarray analysis and qRT-PCR analysis. And we also confirmed the circ_0006427 as a prognostic target in LUAD patients. Functionally, overexpression of circ_0006427 effectively suppressed cell proliferation, migration and invasion. Mechanistically, circ_0006427 was found to be predominantly located in the cytoplasm of LUCA cell, and was further revealed to positively regulate DKK1 in LUAD by sponging miR-6783–3p. KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis and western blot analysis revealed that circ_0006427 inactivated Wnt/β-catenin signaling pathway by upregulating DKK1. At last, rescue assays proved the function of circ_0006427/miR-6783–3p/DKK1 axis in LUAD progression. In conclusion, our study revealed that circ_0006427 suppressed lung adenocarcinoma progression through regulating miR-6783–3p/DKK1 axis. 相似文献
149.
Background
Meiotic prophase is a critical stage in sexual reproduction. Aberrant chromosome recombination during this stage is a leading cause of human miscarriages and birth defects. However, due to the experimental intractability of mammalian gonads, only a very limited number of meiotic genes have been characterized. Here we aim to identify novel meiotic genes important in human reproduction through computational mining of cross-species and cross-sex time-series expression data from budding yeast, mouse postnatal testis, mouse embryonic ovary, and human fetal ovary. 相似文献150.
Kasper Stovgaard Christian Andreetta Jesper Ferkinghoff-Borg Thomas Hamelryck 《BMC bioinformatics》2010,11(1):429