全文获取类型
收费全文 | 2102篇 |
免费 | 162篇 |
专业分类
2264篇 |
出版年
2023年 | 6篇 |
2022年 | 25篇 |
2021年 | 43篇 |
2020年 | 19篇 |
2019年 | 29篇 |
2018年 | 52篇 |
2017年 | 36篇 |
2016年 | 53篇 |
2015年 | 72篇 |
2014年 | 102篇 |
2013年 | 156篇 |
2012年 | 156篇 |
2011年 | 151篇 |
2010年 | 92篇 |
2009年 | 78篇 |
2008年 | 151篇 |
2007年 | 149篇 |
2006年 | 126篇 |
2005年 | 116篇 |
2004年 | 111篇 |
2003年 | 100篇 |
2002年 | 96篇 |
2001年 | 24篇 |
2000年 | 26篇 |
1999年 | 22篇 |
1998年 | 26篇 |
1997年 | 11篇 |
1996年 | 22篇 |
1995年 | 22篇 |
1994年 | 16篇 |
1993年 | 15篇 |
1992年 | 13篇 |
1991年 | 12篇 |
1990年 | 9篇 |
1989年 | 23篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1982年 | 13篇 |
1981年 | 8篇 |
1980年 | 3篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1975年 | 8篇 |
1972年 | 3篇 |
1970年 | 4篇 |
1969年 | 3篇 |
排序方式: 共有2264条查询结果,搜索用时 15 毫秒
1.
Keisuke Hanaki Tomonori Matsuo Michihiko Nagase 《Biotechnology and bioengineering》1981,23(7):1591-1610
The inhibitory effect of long-chain fatty acids on the anaerobic digestion process was examined in batch experiments using synthetic substrates. The addition of long-chain fatty acids caused the appearance of the appearance of the lag period in the methane production from acetate and in the degradation of both long-chain fatty acids and n-butyrate. Methane production from hydrogen proceeded without lag period although its rate was lowered. Fermentation of glucose was not inhibited. Neutral fat in the whole milk was easily hydrolyzed to long-chain fatty acids, which brought about the inhibition. The addition of calcium chloride reduced the inhibitory effect of long-chain fatty but it did not do so after the culture had been exposed to long-chain fatty acids for more than several hours. The addition of calcium carbonate could not reduce the inhibition because of its insolubility. 相似文献
2.
Sleep and Biological Rhythms - 相似文献
3.
An electrophoretic karyotype for Schizosaccharomyces pombe by pulsed field gel electrophoresis. 总被引:44,自引:25,他引:19
下载免费PDF全文
![点击此处可从《Nucleic acids research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
C L Smith T Matsumoto O Niwa S Klco J B Fan M Yanagida C R Cantor 《Nucleic acids research》1987,15(11):4481-4489
The three chromosomal DNAs of S. pombe have been fractionated by pulsed field gel electrophoresis. The resulting molecular karyotype will greatly speed gene mapping in this organism, and it indicates that the separation range of the technique extends to DNA molecules as large as 9,000,000 base pairs. 相似文献
4.
Cloning and sequencing of Schizosaccharomyces pombe DNA topoisomerase I gene, and effect of gene disruption. 总被引:18,自引:7,他引:11
We cloned the structural gene topl+ for Schizosaccharomyces pombe DNA topoisomerase I (topo I) by hybridization. An eight-fold increase of topo I relaxing activity was obtained in S. pombe cells transformed with multicopy plasmid with topl+ insert. Nucleotide sequence determination showed a hypothetical coding frame interrupted by two short introns, encoding a 812 residue polypeptide (M.W. 94,000), 43 residues longer than and 47% homologous to Saccharomyces cerevisiae topo I. We show that the topl (null) strain made by gene disruption is viable, although its generation time is 20% longer than that of wild type. The topl locus is mapped in the long arm of chromosome II, using the Leu+ marker integrated with the cloned topl+ sequence. We constructed a double mutant topl (null) top2 (ts) and found its defective phenotype similar to that of previously obtained topl (heat sensitive) top2 (ts). The other double mutant topl (null) top2 (cs), however, was lethal. Our results suggest that topl+ gene of S. pombe is dispensable only if topo II activity is abundant. 相似文献
5.
Hiroaki Nobuhara Keisuke Kuida Makoto Furutani Toshihiko Shiroishi Kazuo Moriwaki Yusuke Yanagi Tomio Tada 《Immunogenetics》1989,30(6):405-413
Southern blots of genomic DNA from 23 strains of laboratory mice and 19 individual wild mice were examined for restriction
fragment length polymorphisms in their loci encoding the T-cell receptors (Tcr): the constant regions of the α, β, and γ chains
(C
α,C
β, andC
γ) and a variable region family of the β chain (V
β8). Only a few polymorphisms were observed for each locus in the laboratory mice after using three restriction enzymes,Bam HI,Eco RI, andHind III. All the laboratory mice examined fall into one of two types for theC
α,C
β andV
β8 loci and one of three types for theC
γ. These types are found in some of the wild mice studied, indicating that they were already present in the founder mice of
laboratory mouse strains. In contrast, theTcr genes are highly polymorphic among wild mice. Analysis of the polymorphisms in these loci suggests that laboratory mice have
inherited their genes not only fromMus musculus domesticus, but also from other subspecies, and much more than previously believed from Asian subspecies. 相似文献
6.
Toshikuni Sasaoka Norio Kaneda Yoshikazu Kurosawa Keisuke Fujita Toshiharu Nagatsu 《Neurochemistry international》1989,15(4):555-565
The chromosomal gene for human phenylethanolamine N-methyltransferase (PNMT; EC 2.1.1.28) was isolated from a human genomic library using a cloned human PNMT cDNA as a probe, and the nucleotide sequence was determined. PNMT is encoded in a single gene which consists of three exons. We observed newly the presence of minor PNMT mRNA (type B) besides the major mRNA (type A) as reported previously (Kaneda et al., J. Biol. Chem. 263, 7672–7677, 1988) by Northern hybridization. Type B mRNA carries an approximately 700 nucleotide-long untranslated region in the 5′ terminus. This suggests that two types of mRNA are produced from a single gene through the use of two alternative promoters. A TATA-like sequence locates 30 base pair upstream from the cap site of type A mRNA. Upstream of the cap site, there are several sequences resembling Spl binding sites and glucocorticoid responsive elements, with the latter also found in the first intron. 相似文献
7.
Characterization of Schizosaccharomyces pombe minichromosome deletion derivatives and a functional allocation of their centromere. 总被引:8,自引:1,他引:7
下载免费PDF全文
![点击此处可从《The EMBO journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A 530 kb long Schizosaccharomyces pombe linear minichromosome, Ch16, containing a centric region of chromosome III, has previously been made. In the present study, we constructed a number of deletions in the right and/or left arms of Ch16, and compared their structure and behaviour with Ch16. The functional centromere, cen3, is allocated within a 120 kb long region which is covered by the shortest derivative, Ch10, and is comprised mostly of centromeric repeating sequences. The shortest minichromosome is stable in mitosis and the copy number control is apparently precise. In monosomic meiosis it segregates normally. In disomic meioses, however, the frequency of non-disjunction is very high, suggesting that it may not form a pair. The mitotic loss rate of one of the left-arm deletions, ChR32, which lacks a part of the centromeric repeating sequence, is the highest of all the deletions. This deletion also exhibits the highest precocious sister chromatid separation in meiosis I, suggesting that sister chromatid association might become weakened in ChR32. Our results indicate that the proper meiotic segregation of S.pombe minichromosomes is dependent upon the formation of a bivalent. S.pombe may not have the 'distributive segregation' found with Saccharomyces cerevisiae minichromosomes. 相似文献
8.
It is often reported that an animal with spotty coat markings on its body has a tail with stripe-shaped pattern. In other various biological and chemical phenomena in/on cylinder-like domains, longitudinally periodic band patterns are observed much more often than the other non-uniform patterns. This paper mathematically explains these observations by proving that, in/on a long and narrow cylinder-like domain, any solution of reaction-diffusion system asymptotically loses its spatial dependence in the transectional/circumferential direction. 相似文献
9.
10.
Keisuke Yamano Masatomo Tagawa Evelyn Grace de Jesus Tetsuya Hirano Satoshi Miwa Yasuo Inui 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1991,161(4):371-375
Summary To clarify the hormonal regulation of metamorphosis of the conger eel (Conger myriaster), changes in whole body concentrations of thyroid hormones, thyroxine (T4) and triiodothyronine (T3), and cortisol during metamorphosis were examined, as well as the changes in the histological activity of the thyroid gland. In larvae before metamorphosis, T4 and T3 levels were less than 5 and 0.15 ng·g-1 respectively. Levels of T4 increased to about 30 ng·g-1 during early metamorphosis, and decreased subsequently. Levels of T3 increased gradually in early metamorphosis, and then increased abruptly to about 2.0 ng·g-1 in late metamorphosis. Before metamorphosis, cortisol levels of the leptocephali less than 11 cm in total length were greater than 200 ng·g-1. Cortisol levels decreased rapidly in larger premetamorphic leptocephali, and low levels were maintained throughout the metamorphic period. Histological observation revealed an activation of the thyroid gland in early metamorphosis; thyroid follicle epithelial cells became columnar and their nuclei larger. Active uptake of colloid by these cells and intensive vascularization of the gland were also observed. By the end of metamorphosis, follicle epithelial cells became squamous, indicating a low level of glandular activity. These results suggest that thyroid hormone plays an important role in regulation of conger eel metamorphosis.Abbreviations
AL
anal length
-
TL
total length
-
T
3
triiodothyronine
-
T
4
thyroxine 相似文献