全文获取类型
收费全文 | 39600篇 |
免费 | 3493篇 |
国内免费 | 4176篇 |
出版年
2024年 | 72篇 |
2023年 | 397篇 |
2022年 | 1017篇 |
2021年 | 1783篇 |
2020年 | 1414篇 |
2019年 | 1670篇 |
2018年 | 1615篇 |
2017年 | 1263篇 |
2016年 | 1553篇 |
2015年 | 2347篇 |
2014年 | 2879篇 |
2013年 | 3154篇 |
2012年 | 3790篇 |
2011年 | 3341篇 |
2010年 | 2184篇 |
2009年 | 1981篇 |
2008年 | 2438篇 |
2007年 | 2052篇 |
2006年 | 1886篇 |
2005年 | 1608篇 |
2004年 | 1465篇 |
2003年 | 1378篇 |
2002年 | 1242篇 |
2001年 | 687篇 |
2000年 | 539篇 |
1999年 | 517篇 |
1998年 | 378篇 |
1997年 | 298篇 |
1996年 | 285篇 |
1995年 | 265篇 |
1994年 | 218篇 |
1993年 | 176篇 |
1992年 | 179篇 |
1991年 | 138篇 |
1990年 | 128篇 |
1989年 | 124篇 |
1988年 | 100篇 |
1987年 | 86篇 |
1986年 | 86篇 |
1985年 | 92篇 |
1984年 | 51篇 |
1983年 | 42篇 |
1982年 | 50篇 |
1981年 | 20篇 |
1980年 | 19篇 |
1979年 | 31篇 |
1977年 | 24篇 |
1976年 | 19篇 |
1973年 | 20篇 |
1971年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 734 毫秒
1.
2.
R Liang 《Biochemical and biophysical research communications》1984,120(3):741-746
Primary cell cultures were prepared from breast muscles of 11 day 4 hour-embryonic chicks. Cytoplasmic RNAs were isolated from the cultured cells at various time intervals from day 3 to day 8. A [P32] DNA probe complementary to messenger RNA of myosin heavy chain was used to hybridize with the RNAs after gel electrophoresis. A transient species of polyadenylated RNA with a decreased mobility in electrophoresis was detected during a period of time when contractions of syncytial fibers were first observed. 相似文献
3.
4.
Yunfan Sun Liang Wu Yu Zhong Kaiqian Zhou Yong Hou Zifei Wang Zefan Zhang Jiarui Xie Chunqing Wang Dandan Chen Yaling Huang Xiaochan Wei Yinghong Shi Zhikun Zhao Yuehua Li Ziwei Guo Qichao Yu Liqin Xu Jia Fan 《Cell》2021,184(2):404-421.e16
- Download : Download high-res image (233KB)
- Download : Download full-size image
5.
6.
Dongliang Liu Jun Liu Weilan Wang Lijie Xia Jianhua Yang Surong Sun Fuchun Zhang 《Food biophysics》2016,11(4):319-331
Cecropin XJ, as a heat stable antimicrobial peptide (AMP), displayed broad bacteriostatic activities, effectively inhibited proliferation of cancer cells and induced cell apoptosis in vitro. However, it exhibited little hemolytic activity and very low cytotoxicity to erythrocytes and normal cells. Although exerts multiple remarkable bioactivities, the refined molecular conformation of native Cecropin XJ remains unsolved. The aim of the present study is to comprehensively investigate the physicochemical characteristics and structure-function relationship of this antimicrobial peptide by using a series of bioinformatics and experimental approaches. In this study, we revealed that the mature Cecropin XJ consists of 41 amino acids, containing two α-helical structures from Lys7 to Lys25 and from Ala29 to Ile39. The phylogenetic tree indicated that Cecropin XJ belongs to the Class I AMPs of cecropin family. Hydrophobic analysis showed Cecropin XJ is a typical amphiphilic molecule. The surface of Cecropin XJ was found to have a much wide range of electrostatic potential from ?83.243 to +83.243. The amphipathicity and surface potential of Cecropin XJ partially supported the AMP pore-forming hypothesis. Scanning electron microscopy experimentally confirmed the damages of Cecropin XJ to microbial membrane. Four predicted docking sites respectively for magnesium ion (Mg2+), adenosine diphosphate (ADP), bacteriopheophytin (BPH), and guanosine triphosphate (GTP) were found on the surface of Cecropin XJ. Thereinto, Mg2+ was experimentally proved to suppress the antibacterial activity of Cecropin XJ; both GTP and ADP enhanced the bactericidal activities to varying degrees. The present study provides a foundation for further investigation of molecular evolution, structural modification, and functional mechanisms of Cecropin XJ. 相似文献
7.
8.
9.
Effect of fertilizers on Cd accumulation and subcellular distribution of two cosmos species (Cosmos sulphureus and Cosmos bipinnata) 总被引:1,自引:0,他引:1
Addition of fertilizer amendments is regarded as an ideal approach to enhancing phytoextraction. However, there is little information available on the influence of common fertilizers on Cd accumulation of two newly reported Cd accumulators, Cosmos sulphureus and Cosmos bipinnata (C. sulphureus and C. bipinnata). The effects of N (CO(NH2)2), NP (CO(NH2)2 + Ca(H2PO4)2), and NPK (CO(NH2)2 + Ca(H2PO4)2 + KCl) fertilizers on Cd accumulation and subcellular distribution of C. sulphureus and C. bipinnata were studied in a 70-d pot experiment. The results showed that Cd uptake of C. sulphureus and C. bipinnata with NPK fertilizer was significantly higher than control, N, and NP fertilizers, especially 3.8- and 4.7-fold higher than control (p < 0.05). Compared with C. bipinnata, C. sulphureus achieved higher biomass and Cd uptake in aboveground parts under fertilizer treatments, especially NPK fertilizer. The Cd subcellular distribution revealed that segregation of Cd to Cd-rich granules (MRG) might play an important role in Cd detoxification in both species. C. sulphureus is more likely than C. bipinnata to separate the Cd in MRG and reduce the partition in the heat-denatured protein fraction, especially with NPK fertilizer. Therefore, C. sulphureus combined with NPK fertilizers could be an effective method to remediate Cd-polluted farmland soils in China. 相似文献
10.
1. Larval success was compared when one, two, or three egg clutches were laid in kumquat fruits (≈ 10 ml in volume) either successively on the same day or at the rate of one clutch per day. 2. Increased clutch density was associated with a significant decrease in larval survival rate and non‐significant decreases in larval growth rate and pupal mass. 3. Larval and pupal parameters showed significantly larger variance when clutches were laid on successive days than on the same day, suggesting a competitive advantage for older larvae over younger larvae. 4. The results suggest that, in small fruit, reduced fitness due to larval competition may act against possible fitness benefits due to social facilitation among adult females, hence reducing the likelihood of non‐linear population dynamics caused by processes such as the Allee effect. 相似文献