全文获取类型
收费全文 | 2937篇 |
免费 | 190篇 |
出版年
2023年 | 5篇 |
2022年 | 16篇 |
2021年 | 29篇 |
2020年 | 18篇 |
2019年 | 35篇 |
2018年 | 46篇 |
2017年 | 48篇 |
2016年 | 67篇 |
2015年 | 101篇 |
2014年 | 135篇 |
2013年 | 169篇 |
2012年 | 201篇 |
2011年 | 201篇 |
2010年 | 145篇 |
2009年 | 138篇 |
2008年 | 232篇 |
2007年 | 196篇 |
2006年 | 205篇 |
2005年 | 204篇 |
2004年 | 205篇 |
2003年 | 155篇 |
2002年 | 182篇 |
2001年 | 25篇 |
2000年 | 26篇 |
1999年 | 29篇 |
1998年 | 37篇 |
1997年 | 29篇 |
1996年 | 27篇 |
1995年 | 14篇 |
1994年 | 17篇 |
1993年 | 20篇 |
1992年 | 19篇 |
1991年 | 14篇 |
1990年 | 12篇 |
1989年 | 9篇 |
1988年 | 10篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 14篇 |
1984年 | 17篇 |
1983年 | 20篇 |
1982年 | 10篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1965年 | 1篇 |
1960年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有3127条查询结果,搜索用时 15 毫秒
1.
Glycinin A3B4 mRNA. Cloning and sequencing of double-stranded cDNA complementary to a soybean storage protein 总被引:8,自引:0,他引:8
C Fukazawa T Momma H Hirano K Harada K Udaka 《The Journal of biological chemistry》1985,260(10):6234-6239
The cDNA clones encoding the precursor form of glycinin A3B4 subunit have been identified from a library of soybean cotyledonary cDNA clones in the plasmid pBR322 by a combination of differential colony hybridizations, and then by immunoprecipitation of hybrid-selected translation product with A3-mono-specific antiserum. A recombinant plasmid, designated pGA3B41425, from one of six clones covering codons for the NH2-terminal region of the subunit was sequenced, and the amino acid sequence was inferred from the nucleotide sequence, which showed that the mRNA codes for a precursor protein of 516 amino acids. Analysis of this cDNA also showed that it contained 1786 nucleotides of mRNA sequence with a 5'-terminal nontranslated region of 46 nucleotides, a signal peptide region corresponding to 24 amino acids, an A3 acidic subunit region corresponding to 320 amino acids followed by a B4 basic subunit region corresponding to 172 amino acids, and a 3'-terminal nontranslated region of 192 nucleotides, which contained two characteristic AAUAAA sequences that ended 110 nucleotides and 26 nucleotides from a 3'-terminal poly(A) segment, respectively. Our results confirm that glycinin is synthesized as precursor polypeptides which undergo post-translational processing to form the nonrandom polypeptide pairs via disulfide bonds. The inferred amino acid sequence of the mature basic subunit, B4, was compared to that of the basic subunit of pea legumin, Leg Beta, which contained 185 amino acids. Using an alignment that permitted a maximum homology of amino acids, it was found that overall 42% of the amino acid positions are identical in both proteins. These results led us to conclude that both storage proteins have a common ancestor. 相似文献
2.
Efficient synthesis and secretion of a thermophilic alpha-amylase by protein-producing Bacillus brevis 47 carrying the Bacillus stearothermophilus amylase gene. 总被引:7,自引:2,他引:5
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
N Tsukagoshi S Iritani T Sasaki T Takemura H Ihara Y Idota H Yamagata S Udaka 《Journal of bacteriology》1985,164(3):1182-1187
Bacillus subtilis and Bacillus brevis 47-5, carrying the Bacillus stearothermophilus alpha-amylase gene on pUB110 (pBAM101), synthesized the same alpha-amylase as the donor strain as determined by the enzyme's thermal stability and NH2-terminal amino acid sequence. Regardless of the host, the 34-amino acid signal peptide of the enzyme was processed at exactly the same site between two alanine residues. B. brevis 47-5(pBAM101) secreted the enzyme most efficiently of the hosts examined, 100, 15, and 5 times more than B. stearothermophilus, Escherichia coli HB101(pH1301), and B. subtilis 1A289(pBAM101), respectively. The efficient secretion of the enzyme in B. brevis 47-5(pBAM101) was suggested to be due to the unique properties of the cell wall of this organism. 相似文献
3.
Summary A 6.4 Kb HindIII fragment of Bacillus stearothermophilus DY-5 DNA cloned in Escherichia coli using pBR322 as a vector was shown to direct the synthesis of a thermophilic -amylase. In attempts to reduce the size of the insert, the -amylase gene was shown to be contained in a 3.1 Kb HindIII-BamHI fragment of the donor strain DNA.The -amylase gene was stably maintained and expressed efficiently in E. coli. The enzymic properties of -amylase produced in E. coli closely resembled those of the donor strain -amylase and the temperature range for the maximal activity was from 65° C to 80° C. Nearly 100% of the activity remained after heating at 80° C for 15 min.The -amylase was shown to be accumulated in the periplasmic space. It was purified to a nearly homogenous protein with a molecular weight of 61,000, which was very similar in size to that produced by B. stearothermophilus DY-5. 相似文献
4.
Masanori Kasahara Toshinao Takenouchi Kazumasa Ogasawara Hitoshi Ikeda Tsuguyo Okuyama Naoshi Ishikawa Junko Moriuchi Akemi Wakisaka Yuko Kikuchi Miki Aizawa Takehisa Kaneko Noboru Kashiwagi Yasuharu Nishimura Takehiko Sasazuki 《Immunogenetics》1983,17(5):485-495
To study the gene products of the HLA complex, we produced two monoclonal antibodies, termed HU-18 and HU-23. They were active in complement-dependent cytotoxicity and detected B-cell alloantigens encoded by a locus (or loci) linked to HLA. When three types of HLA-DR4 homozygous B-cell lines with different HLA-D specificities were tested for reactivity with HU-18 and HU-23, they displayed distinct reaction patterns depending on the HLA-D specificities they possessed: EBV-Wa (HLA-DYT homozygous), negative for both HU-18 and HU-23; KT2 and KOB (HLA-DKT2 homozygous), positive only for HU-18; and ER (HLA-Dw4 homozygous), positive for both. These differential reaction patterns were further confirmed by testing against a panel of 17 HLA-DR4-positive peripheral blood lymphocytes with known HLA-D specificities. Thus, these monoclonal antibodies allow us to identify HLA-DYT, HLA-DKT2, and HLA-Dw4 solely by serologic methods. This is the first clearcut serologic identification of these three HLA-DR4-associated HLA-D specificities, which have been indistinguishable by conventional serology and identified only by cellular techniques. It is hoped that immunochemical investigations using HU-18 and HU-23 will advance our understanding of the HLA-D region on a molecular level. 相似文献
5.
6.
7.
A single gene directs synthesis of a precursor protein with beta- and alpha-amylase activities in Bacillus polymyxa. 总被引:7,自引:4,他引:3
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
N Uozumi K Sakurai T Sasaki S Takekawa H Yamagata N Tsukagoshi S Udaka 《Journal of bacteriology》1989,171(1):375-382
The Bacillus polymyxa amylase gene comprises 3,588 nucleotides. The mature amylase comprises 1,161 amino acids with a molecular weight of 127,314. The gene appeared to be divided into two portions by the direct-repeat sequence located at almost the middle of the gene. The 5' region upstream of the direct-repeat sequence was shown to be responsible for the synthesis of beta-amylase. The 3' region downstream of the direct-repeat sequence contained four sequences homologous with those in other alpha-amylases, such as Taka-amylase A. The 48-kilodalton (kDa) amylase isolated from B. polymyxa was proven to have alpha-amylase activity. The amino acid sequences of the peptides generated from the 48-kDa amylase showed complete agreement with the predicted amino acid sequence of the C-terminal portion. The B. polymyxa amylase gene was therefore concluded to contain in-phase beta- and alpha-amylase-coding sequences in the 5' and 3' regions, respectively. A precursor protein, a 130-kDa amylase, directed by a plasmid, pYN520, carrying the entire amylase gene, had both beta- and alpha-amylase activities. This represents the first report of a single protein precursor in procaryotes that gives rise to two enzymes. 相似文献
8.
Amino acid residues stabilizing a Bacillus alpha-amylase against irreversible thermoinactivation 总被引:3,自引:0,他引:3
Y Suzuki N Ito T Yuuki H Yamagata S Udaka 《The Journal of biological chemistry》1989,264(32):18933-18938
The alpha-amylase of Bacillus licheniformis (BLA) is stable and active at high temperature. More than 80% of its activity is retained after heat treatment at 90 degrees C for 30 min, and the optimum temperature for its activity is 80-85 degrees C. In contrast, the alpha-amylase of Bacillus amyloliquefaciens (BAA), the amino acid sequence of which shows 80% homology with that of BLA, is rapidly inactivated at 90 degrees C. Various chimeric genes were constructed from the structural genes for the two enzymes, and their products were analyzed for stability as to irreversible thermoinactivation. Two regions in the amino acid sequence of BLA comprising Gln178 (region I) and the 255th-270th residues (region II), respectively, were shown to determine the thermostability of BLA. Region I plays a major role in determining the thermostability. By means of site-directed mutagenesis of the BAA gene, deletion of Arg176 and Gly177 in region I and substitutions of alanine for Lys269 and aspartic acid for Asn266 in region II were shown to be responsible for the enhancement of the thermostability. Mutant BAAs containing the above deletion and substitutions showed almost the same thermostability as BLA as to irreversible thermoinactivation. Nevertheless, the mutant BAAs showed a temperature optimum as low as that of BAA (65 degrees C), indicating that they are still susceptible to reversible inactivation at temperatures higher than 65 degrees C. 相似文献
9.
Akira Nomura Yuko Yamazaki Takashi Tsuji Yukishige Kawasaki Shoji Tanaka 《Experimental cell research》1996,227(2):256
For all biological particles such as cells or cellular organelles, there are three-dimensional coordinates representing the centroid or center of gravity. These coordinates and other numerical parameters such as volume, fluorescence intensity, surface area, and shape are referred to in this paper as geometric properties, which may provide critical information for the clarification ofin situmechanisms of molecular and cellular functions in living organisms. We have established a method for the elucidation of these properties, designated the three-dimensional labeling program (3DLP). Algorithms of 3DLP are so simple that this method can be carried out through the use of software combinations in image analysis on a personal computer. To evaluate 3DLP, it was applied to a 32-cell-stage sea urchin embryo, double stained with FITC for cellular protein of blastomeres and propidium iodide for nuclear DNA. A stack of optical serial section images was obtained by confocal laser scanning microscopy. The method was found effective for determining geometric properties and should prove applicable to the study of many different kinds of biological particles in three-dimensional space. 相似文献
10.
Takeshi Minami Masayo Ichii Yoshiyuki Tohno Setsuko Tohno Masako Utsumi Masa-oki Yamada Yuko Okazaki 《Biological trace element research》1996,55(1-2):199-205
The purpose of this study was to determine the extent of aluminum (Al) accumulation in the human aorta and cerebral arteries.
The Al contents in the aortae and in the cerebral arteries from 23 human subjects was determined by inductively coupled plasma
atomic emission spectrophotometry (ICP-AES). The subjects' age range was 45–99-yr-old; 15 of the subjects were males and 8
were females. Al was detected in twelve aortae and in six cerebral arteries, when the entire specimen was analyzed. Two specimens
where Al was found in the cerebral arteries contained no Al in the aorta. No relationship to the subject's sex was found.
When related to age, two groups were established. Group L (45–75 yr old) and group H (>75 yr old), which exhibited aortal
Al concentrations of 33.3 and 72.7%, respectively. When the aortic wall was dissected into the tunica intima, media, and adventitia,
Al was found mainly in the tunica media. In the aorta, significant relationships were found between Al and phosphorus (P)
levels (r=0.801,p<0.01) and between Al and calcium (Ca) (r=0.661,p<0.05). We have concluded that Al accumulation is age-dependent and that it occurs both in the aorta and in the cerebral artery.
In the aorta, accumulation occurs mainly in the tunica media. Both P and Ca appear to enhance aortal Al accumulation. 相似文献