全文获取类型
收费全文 | 31778篇 |
免费 | 1597篇 |
国内免费 | 1285篇 |
出版年
2023年 | 333篇 |
2022年 | 285篇 |
2021年 | 556篇 |
2020年 | 669篇 |
2019年 | 842篇 |
2018年 | 727篇 |
2017年 | 698篇 |
2016年 | 784篇 |
2015年 | 1061篇 |
2014年 | 1757篇 |
2013年 | 2667篇 |
2012年 | 1399篇 |
2011年 | 1409篇 |
2010年 | 1218篇 |
2009年 | 1405篇 |
2008年 | 1468篇 |
2007年 | 1479篇 |
2006年 | 1389篇 |
2005年 | 1297篇 |
2004年 | 1172篇 |
2003年 | 1135篇 |
2002年 | 1027篇 |
2001年 | 768篇 |
2000年 | 751篇 |
1999年 | 694篇 |
1998年 | 642篇 |
1997年 | 570篇 |
1996年 | 531篇 |
1995年 | 604篇 |
1994年 | 582篇 |
1993年 | 471篇 |
1992年 | 480篇 |
1991年 | 377篇 |
1990年 | 383篇 |
1989年 | 290篇 |
1988年 | 343篇 |
1987年 | 269篇 |
1986年 | 230篇 |
1985年 | 334篇 |
1984年 | 389篇 |
1983年 | 256篇 |
1982年 | 287篇 |
1981年 | 140篇 |
1980年 | 121篇 |
1979年 | 118篇 |
1978年 | 71篇 |
1977年 | 38篇 |
1976年 | 41篇 |
1974年 | 25篇 |
1973年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
高血压是常见的慢性疾病,也是心脑血管病最主要的风险因素。原发性高血压是由多基因和环境因素共同作用引起的复杂疾病,但具体的发病机制仍不清楚。随着研究的深入,DNA甲基化等表观遗传学因素在原发性高血压病理过程中起到的作用逐渐受到重视。本文总结了部分原发性高血压关联基因中DNA甲基化在其患病中的研究进展,阐述可受环境因素影响的DNA甲基标记与原发性高血压的关系,进一步了解高血压的发病机制。 相似文献
2.
3.
We sought to develop nuclear DNA (nDNA) probes which could be used to complement mtDNA and DNA fingerprinting markers in distinguishing striped bass, Morone saxatilis (Walbaum), from discrete spawning systems. Restriction endonuclease-generated single copy, 10–20-kb striped bass nuclear nDNA fragments were cloned into the bacteriophage vector Lambda Dash II and tested in Southern blot analyses for their abilities to reveal population-specific polymorphisms. Three of the I7 nDNA sequences tested exhibited polymorphisms which potentially could be used to delineate striped bass populations. One probe, DSB 22, revealed significant genotypic frequency differences between Gulf of Mexico and Atlantic striped bass and among striped bass representative of some Atlantic systems. These preliminary results suggest that single copy nDNA sequences may provide sufficient polymorphisms to aid in stock identification of species which proved genetically monomorphic using other approaches. 相似文献
4.
5.
Honghong Yang Yuanyuan Zhang Zhihai Wang Shixun Zhong Guohua Hu Wenqi Zuo 《Bioelectromagnetics》2020,41(3):219-229
To investigate the possible mechanisms for biological effects of 1,800 MHz mobile radiofrequency radiation (RFR), the radiation-specific absorption rate was applied at 2 and 4 W/kg, and the exposure mode was 5 min on and 10 min off (conversation mode). Exposure time was 24 h short-term exposure. Following exposure, to detect cell DNA damage, cell apoptosis, and reactive oxygen species (ROS) generation, the Comet assay test, flow cytometry, DAPI (4′,6-diamidino-2-phenylindole dihydrochloride) staining, and a fluorescent probe were used, respectively. Our experiments revealed that mobile phone RFR did not cause DNA damage in marginal cells, and the rate of cell apoptosis did not increase (P > 0.05). However, the production of ROS in the 4 W/kg exposure group was greater than that in the control group (P < 0.05). In conclusion, these results suggest that mobile phone energy was insufficient to cause cell DNA damage and cell apoptosis following short-term exposure, but the cumulative effect of mobile phone radiation still requires further confirmation. Activation of the ROS system plays a significant role in the biological effects of RFR. Bioelectromagnetics. © 2020 The Authors. Bioelectromagnetics published by Wiley Periodicals, Inc. 相似文献
6.
7.
8.
Maria B. Olsen Gunn A. Hildrestrand Katja Scheffler Leif Erik Vinge Katrine Alfsnes Vuk Palibrk Junbai Wang Christine G. Neurauter Luisa Luna Jostein Johansen Jonas D.S. Øgaard Ingrid K. Ohm Geir Slupphaug Anna Kuśnierczyk Arnt E. Fiane Sverre-Henning Brorson Lili Zhang Lars Gullestad Alexandra V. Finsen 《Cell reports》2017,18(1):82-92
9.
10.
Mengnan Wang Dongjie Li Mingyue Zhang Wenzhi Yang Yali Cui Shijie Li 《Animal genetics》2015,46(4):354-360
The CDKN1C gene encodes a cyclin‐dependent kinase inhibitor and is one of the key genes involved in the development of Beckwith–Wiedemann syndrome and cancer. In this study, using a direct sequencing approach based on a single nucleotide polymorphism (SNP) at genomic DNA and cDNA levels, we show that CDKN1C exhibits monoallelic expression in all seven studied organs (heart, liver, spleen, lung, kidney, muscle and subcutaneous fat) in cattle. To investigate how methylation regulates imprinting of CDKN1C in cattle, allele‐specific methylation patterns in two putative differential methylation regions (DMRs), the CDKN1C DMR and KvDMR1, were analyzed in three tissues (liver, spleen and lung) using bisulfite sequencing PCR. Our results show that in the CDKN1C DMR both parental alleles were unmethylated in all three analyzed tissues. In contrast, KvDMR1 was differentially methylated between the two parental alleles in the same tissues. Statistical analysis showed that there is a significant difference in the methylation level between the two parental alleles (P < 0.01), confirming that this region is the DMR of KvDMR1 and that it may be correlated with CDKN1C imprinting. 相似文献