全文获取类型
收费全文 | 49957篇 |
免费 | 4468篇 |
国内免费 | 5375篇 |
出版年
2024年 | 156篇 |
2023年 | 1109篇 |
2022年 | 1520篇 |
2021年 | 2419篇 |
2020年 | 2278篇 |
2019年 | 3083篇 |
2018年 | 2240篇 |
2017年 | 1754篇 |
2016年 | 1686篇 |
2015年 | 2113篇 |
2014年 | 3063篇 |
2013年 | 3838篇 |
2012年 | 2276篇 |
2011年 | 2479篇 |
2010年 | 1837篇 |
2009年 | 2236篇 |
2008年 | 2359篇 |
2007年 | 2517篇 |
2006年 | 2504篇 |
2005年 | 2269篇 |
2004年 | 2053篇 |
2003年 | 1870篇 |
2002年 | 1707篇 |
2001年 | 1359篇 |
2000年 | 1120篇 |
1999年 | 1038篇 |
1998年 | 952篇 |
1997年 | 797篇 |
1996年 | 772篇 |
1995年 | 733篇 |
1994年 | 684篇 |
1993年 | 488篇 |
1992年 | 445篇 |
1991年 | 372篇 |
1990年 | 297篇 |
1989年 | 214篇 |
1988年 | 237篇 |
1987年 | 206篇 |
1986年 | 143篇 |
1985年 | 142篇 |
1984年 | 124篇 |
1983年 | 53篇 |
1982年 | 74篇 |
1981年 | 38篇 |
1980年 | 45篇 |
1979年 | 32篇 |
1978年 | 22篇 |
1977年 | 10篇 |
1976年 | 18篇 |
1974年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
61.
目的对virB2基因编码蛋白进行分析,为virB2基因及其编码蛋白功能提供实验依据。方法利用多种生物学软件以及网站对VirB2蛋白的结构和功能进行分析预测,VirB2蛋白序列通过基因推导获得并由生物公司合成,然后通过免疫动物实验制备鼠抗VirB2蛋白多克隆抗体,同时设计进行VirB2蛋白细胞毒试验(MTT法)。结果virB2基因编码蛋白属于疏水性蛋白,为鞭毛样结构,有较强的细胞毒作用。结论对VirB2蛋白的结构和功能进行了分析预测,证明VirB2蛋白在H.pylori相关的致病性特别是引起胃黏膜炎症方面起到一定的作用,能够为研究H.pylori致病机制提供帮助。 相似文献
62.
《Developmental cell》2022,57(2):212-227.e8
- Download : Download high-res image (115KB)
- Download : Download full-size image
63.
《Bioscience, biotechnology, and biochemistry》2013,77(5):1190-1198
The Rhynchosciara americana C3-22 gene is located in an amplified domain and is developmentally expressed. The aim of the present work was to identify intrinsically bent DNA sites in a segment containing the gene promoter and downstream sequence. The results indicated that this gene is flanked by intrinsically bent DNA sites. Three bent DNA sites (b?3, b?2, and b?1) were localized in the promoter, and one was localized downstream of the gene (b+1). These sites had helical parameters that confirmed the curved structure, as well as segments with left-handed superhelical writhe. In silico analysis of the promoters of four other insect genes, which encode secreted polypeptides, showed that they all had curved structures and similar helical parameters. Correlation with other results indicates that the detected intrinsically bent DNA sites that flank the C3-22 gene might be a consensus feature of the gene structure in the amplified domains. 相似文献
64.
65.
Global species delimitation and phylogeography of the circumtropical ‘sexy shrimp’ Thor amboinensis reveals a cryptic species complex and secondary contact in the Indo‐West Pacific
下载免费PDF全文
![点击此处可从《Journal of Biogeography》网站下载免费的PDF全文](/ch/ext_images/free.gif)
66.
PurposeTo define optimal planning target volume (PTV) margins for intensity modulated radiotherapy (IMRT) ± knee-heel support (KHS) in patients treated with adjuvant radiotherapy.MethodsComputed tomography (CT) scans ± KHS of 10 patients were taken before and at 3rd and 5th week of treatment, fused and compared with initial IMRT plans.ResultsA PTV margin of 15 mm in anteroposterior (AP) and superoinferior (SI) directions and 5 mm in lateral directions were found to be adequate without any difference between ± KHS except for the SI shifts in CTV-primary at the 3rd week. Five mm margin for iliac CTV was found to be inadequate in 10–20% of patients in SI directions however when 7 mm margin was given for iliac PTV, it was found to be adequate. For presacral CTV, it was found that the most striking shift of the target volume was in the direction of AP. KHS caused significantly less volume of rectum and bladder in the treated volume.ConclusionsPTV margin of 15 mm in SI and AP, and 5 mm in lateral directions for CTV-primary were found to be adequate. A minimum of 7 mm PTV margin should be given to iliac CTV. The remarkable shifting in presacral CTV was believed to be due to the unforeseen hip malposition of obese patients. The KHS seems not to provide additional beneficial effect in decreasing the shifts both in CTV-primary and lymphatic, however it may have a beneficial effect of decreasing the OAR volume in PTV margins. 相似文献
67.
68.
Docetaxel resistance remains one of the main problems in clinical treatment of metastatic prostate cancer (PCa). Previous studies identified differently expressed lncRNAs in docetaxel-resistant PCa cell lines, while the potential mechanisms were still unknown. In the present study, we found NEAT1 was expressed at high levels in docetaxel-resistant PCa clinical samples and related cell lines. When knockdown NEAT1, cell proliferation and invasion in docetaxel-resistant PCa cells in vitro and in vivo were downregulated. Our further researches explained that NEAT1 exerts oncogenic function in PCa by competitively ‘sponging’ both miR-34a-5p and miR-204-5p. Inhibition of miR-34a-5p or miR-204-5p expression mimics the docetaxel-resistant activity of NEAT1, whereas ectopic expression of miR-34a-5p or miR-204-5p attenuates the anti-drug function of NEAT1 in PCa cells. Besides, we also found ACSL4 is a target of both miR-34a-5p and miR-204-5p, and ACSL4 was also inhibited by miR-34a-5p and miR-204-5p. Moreover, suppression of miR-34a-5p or/and miR-204-5p greatly restrained the expression of ACSL4 upon NEAT1 overexpression. Joint expression of miR-34a-5p and miR-204a-5p synergistically decreased the expression of ASCL4, indicating miR-34a-5p and miR-204a-5p collaboratively inhibit the expression of ACSL4. Innovatively, we concluded that NEAT1 contributes to the docetaxel resistance by increasing ACSL4 via sponging miR-34a-5p and miR-204-5p in PCa cells. 相似文献
69.
70.
《Bioscience, biotechnology, and biochemistry》2013,77(12):2758-2761
A group I intron that can be spliced in vivo and in vitro was identified in the flagellin gene of the thermophilic bacterium Geobacillus stearothermophilus. We also found one or two intervening sequences (IVS) of flagellin genes in five additional bacterial species. Furthermore, we report the presence of these sequences in two sites of a highly conserved region in the flagellin gene. 相似文献