全文获取类型
收费全文 | 20342篇 |
免费 | 1362篇 |
国内免费 | 2829篇 |
出版年
2024年 | 22篇 |
2023年 | 264篇 |
2022年 | 335篇 |
2021年 | 481篇 |
2020年 | 507篇 |
2019年 | 697篇 |
2018年 | 553篇 |
2017年 | 593篇 |
2016年 | 634篇 |
2015年 | 769篇 |
2014年 | 990篇 |
2013年 | 1336篇 |
2012年 | 886篇 |
2011年 | 1001篇 |
2010年 | 840篇 |
2009年 | 1166篇 |
2008年 | 1263篇 |
2007年 | 1348篇 |
2006年 | 1228篇 |
2005年 | 1236篇 |
2004年 | 1066篇 |
2003年 | 1041篇 |
2002年 | 833篇 |
2001年 | 684篇 |
2000年 | 564篇 |
1999年 | 517篇 |
1998年 | 511篇 |
1997年 | 386篇 |
1996年 | 375篇 |
1995年 | 413篇 |
1994年 | 352篇 |
1993年 | 274篇 |
1992年 | 268篇 |
1991年 | 216篇 |
1990年 | 178篇 |
1989年 | 120篇 |
1988年 | 148篇 |
1987年 | 99篇 |
1986年 | 66篇 |
1985年 | 66篇 |
1984年 | 61篇 |
1983年 | 35篇 |
1982年 | 37篇 |
1981年 | 17篇 |
1980年 | 11篇 |
1979年 | 14篇 |
1978年 | 10篇 |
1976年 | 7篇 |
1975年 | 4篇 |
1950年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
《Saudi Journal of Biological Sciences》2017,24(1):1-10
Uranium has been defined in material research engineering field as one of the most energetic radioactive elements in the entire Mendeleev periodic table. The manipulation of uranium needs higher theories and sophisticated apparatus even in nuclear energy extraction or in many other chemical applications. Above the nuclear exploitation level, the chemical conventional approaches used, require a higher temperature and pressure to control the destination of ionic form. However, it has been discovered later that at biological scale, the manipulation of this actinide is possible under friendly conditions. The review summarizes the relevant properties of uranium element and a brief characterization of nanoparticles, based on some structural techniques. These techniques reveal the common link between chemical approaches and biological assistance in nanoparticles. Also, those biological entities have been able to get it after reduction. Uranium is known for its ability to destroy ductile materials. So, if biological cell can really reduce uranium, then how does it work? 相似文献
3.
4.
5.
6.
Learning-Induced Expression of Meningeal Ependymin mRNA and Demonstration of Ependymin in Neurons and Glial Cells 总被引:1,自引:0,他引:1
Stefan Rother Rupert Schmidt Wolfgang Brysch †Karl-Hermann Schlingensiepen 《Journal of neurochemistry》1995,65(4):1456-1464
Abstract: The turnover of a CNS-specific cell adhesion glycoprotein, ependymin, has earlier been found to increase during periods of neuronal plasticity. Here, ependymin mRNA expression was analyzed by semiquantitative in situ hybridization in goldfish. Learning of an active avoidance response resulted in a significant increase in ependymin mRNA expression 20 min to 4 h after acquisition of the task. In contrast, yoked control animals that were exposed to the same numbers of conditioned and unconditioned stimuli in a random, unpaired manner exhibited a strong down-regulation of ependymin mRNA. Hybridization signals were also increased by injection of anti-ependymin antiserum into brain ventricles. Ependymin mRNA was exclusively localized to reticular-shaped fibroblasts of the inner endomeningeal cell layer. Immunoelectron microscopic investigation, however, revealed ependymin also in distinct neuronal and glial cell populations in which no ependymin mRNA had been detected. Uptake of meningeal protein factors into glial and neuronal cells may therefore be of functional importance for plastic adaptations of the CNS. 相似文献
7.
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
8.
9.
10.