全文获取类型
收费全文 | 2266篇 |
免费 | 100篇 |
专业分类
2366篇 |
出版年
2023年 | 4篇 |
2022年 | 13篇 |
2021年 | 30篇 |
2020年 | 13篇 |
2019年 | 31篇 |
2018年 | 21篇 |
2017年 | 18篇 |
2016年 | 45篇 |
2015年 | 63篇 |
2014年 | 93篇 |
2013年 | 117篇 |
2012年 | 136篇 |
2011年 | 126篇 |
2010年 | 78篇 |
2009年 | 68篇 |
2008年 | 154篇 |
2007年 | 129篇 |
2006年 | 121篇 |
2005年 | 115篇 |
2004年 | 145篇 |
2003年 | 136篇 |
2002年 | 136篇 |
2001年 | 43篇 |
2000年 | 51篇 |
1999年 | 45篇 |
1998年 | 36篇 |
1997年 | 28篇 |
1996年 | 36篇 |
1995年 | 23篇 |
1994年 | 19篇 |
1993年 | 26篇 |
1992年 | 32篇 |
1991年 | 24篇 |
1990年 | 21篇 |
1989年 | 17篇 |
1988年 | 16篇 |
1987年 | 15篇 |
1986年 | 8篇 |
1985年 | 13篇 |
1984年 | 11篇 |
1983年 | 20篇 |
1982年 | 19篇 |
1981年 | 11篇 |
1980年 | 8篇 |
1979年 | 13篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1974年 | 4篇 |
1970年 | 3篇 |
1969年 | 4篇 |
排序方式: 共有2366条查询结果,搜索用时 0 毫秒
1.
We documented changes in morphology and gene expression of the renal epithelial cell line A6 derived from Xenopus leavis adult kidney induced by long-term culturing with three dimensional clinostats. An oligo microarray analysis on A6 cells showed that mRNA levels of 52 out of 8091 genes were significantly altered in response to clinorotation. Upregulation or downregulation of gene expression became evident on day 8 and day 10 while there was no significant change on day 5. However, on day 15, expression of 18 out of 52 genes resumed to the levels similar to its original levels while remaining 33 genes maintained altered levels of expression. Quantitative analyses of gene expression by real-time PCR confirmed that changes in mRNA levels of selected genes were found only under clinorotation but not under hypergravity (7 G) and ground control (1 G). Morphological changes including loss of dome-like structures, disassembly of E-cadherin adherence junctions and disassembly of cortical actin were also observed over 10 days of culturing with clinorotation. The results revealed genes which expression was altered specifically in A6 cells cultured under clinorotation. 相似文献
2.
3.
Effects of an antisense napin gene on seed storage compounds in transgenic Brassica napus seeds 总被引:4,自引:0,他引:4
Junko Kohno-Murase Makoto Murase Hiroaki Ichikawa Jun Imamura 《Plant molecular biology》1994,26(4):1115-1124
To manipulate the quantity and quality of storage components in Brassica napus seeds, we have constructed an antisense gene for the storage protein napin. The antisense gene was driven by the 5-flanking region of the B. napus napin gene to express antisense RNA in a seed-specific manner. Seeds of transgenic plants with antisense genes often contained reduced amounts of napin. In some transgenic plants, no accumulation of napin was observed. However, the total protein content of transgenic and wild-type seeds did not differ significantly. Seeds lacking napin accumulated 1.4 to 1.5 times more cruciferin than untransformed seeds, although the oleosin content was not affected. Fatty acid content and composition in the seeds of transgenic plants were also analyzed by gas chromatography. Though the total fatty acid content of the transformants was the same as that of non-transformants, there was a reduction in 18:1 contents and a concomitant increase of 18:2 in seeds with reduced napin levels. This observed change in fatty acid composition was inherited in the next generation. 相似文献
4.
Recovery processes of photosynthetic systems during rewetting were studied in detail in a terrestrial, highly drought-tolerant cyanobacterium, Nostoc commune. With absorption of water, the weight of N. commune colony increased in three phases with half-increase times of about 1 min, 2 h and 9 h. Fluorescence intensities of phycobiliproteins and photosystem (PS) I complexes were recovered almost completely within 1 min, suggesting that their functional forms were restored very quickly. Energy transfer from allophycocyanin to the core-membrane linker peptide (L(CM)) was recovered within 1 min, but not that from L(CM) to PSII. PSI activity and cyclic electron flow around PSI recovered within 2 min, while the PSII activity recovered in two phases after a time lag of about 5 min, with half times of about 20 min and 2 h. Photosynthetic CO(2) fixation was restored almost in parallel with the first recovery phase of the PSII reaction center activity. Although the amount of absorbed water became more than 20 times the initial dry weight of the N. commune colony in the presence of sufficient water, about twice the initial dry weight was enough for recovery and maintenance of the PSII activity. 相似文献
5.
Sakiyama Tomoki Morimoto Junko Matsubayashi Jun Furukawa Yasuto Kondo Mami Tsuruga Hifumi Mano Tsutomu Nakamura Futoshi 《Landscape and Ecological Engineering》2021,17(3):351-362
Landscape and Ecological Engineering - Investigating factors underlying human-wildlife conflicts in agricultural landscapes is important for both preventing crop damage and wildlife conservation.... 相似文献
6.
Molecular cloning and sequence analysis of cDNA containing the entire coding region for human fetal liver cytochrome P-450 总被引:4,自引:0,他引:4
From a human fetal liver cDNA library, a cDNA clone (lambda HFL33) containing the entire coding region for a form of cytochrome P-450 related to P-450 HFLa was obtained. The clone was 1,971 bp long and had an open reading frame of 1,509 nucleotides coding for a 503 amino acid polypeptide. The nucleotide and the deduced amino acid sequences of lambda HFL33 were very similar to but clearly distinct from those of NF25 and HLp cDNAs, which code for forms of cytochrome P-450 in adult human liver. The deduced N-terminal amino acid sequence of the HFL33 protein was identical to that of P-450 HFLa. 相似文献
7.
Teiichiro Ito Tadao Ishii Motohiro Nishio 《Bioscience, biotechnology, and biochemistry》2013,77(8):728-731
α-Methylthio-cinnamic acid and its substituted analogues (III) were synthesized from their respective β-aryl-α-thiopyruvic acids (II). In connection with the study on the tautomeric ene-thiol structure of β-aryl-α-thiopyruvic acids (II), 4-arylidenerl,3-oxathiolan-5-one (IV) were prepared from compounds II. 相似文献
8.
Recent advances in the use of summed probability distribution (SPD) of calibrated 14C dates have opened new possibilities for studying prehistoric demography. The degree of correlation between climate change and population dynamics can now be accurately quantified, and divergences in the demographic history of distinct geographic areas can be statistically assessed. Here we contribute to this research agenda by reconstructing the prehistoric population change of Jomon hunter-gatherers between 7,000 and 3,000 cal BP. We collected 1,433 14C dates from three different regions in Eastern Japan (Kanto, Aomori and Hokkaido) and established that the observed fluctuations in the SPDs were statistically significant. We also introduced a new non-parametric permutation test for comparing multiple sets of SPDs that highlights point of divergences in the population history of different geographic regions. Our analyses indicate a general rise-and-fall pattern shared by the three regions but also some key regional differences during the 6th millennium cal BP. The results confirm some of the patterns suggested by previous archaeological studies based on house and site counts but offer statistical significance and an absolute chronological framework that will enable future studies aiming to establish potential correlation with climatic changes. 相似文献
9.
10.
Kenji Nakayama Takahiro Inoue Sadanori Sekiya Naoki Terada Yu Miyazaki Takayuki Goto Shigeki Kajihara Shin-Ichiro Kawabata Shinichi Iwamoto Kuniko Ikawa Junko Oosaga Hiroaki Tsuji Koichi Tanaka Osamu Ogawa 《PloS one》2014,9(9)