全文获取类型
收费全文 | 3189篇 |
免费 | 214篇 |
专业分类
3403篇 |
出版年
2022年 | 19篇 |
2021年 | 28篇 |
2020年 | 14篇 |
2019年 | 21篇 |
2018年 | 31篇 |
2017年 | 29篇 |
2016年 | 45篇 |
2015年 | 74篇 |
2014年 | 93篇 |
2013年 | 145篇 |
2012年 | 137篇 |
2011年 | 131篇 |
2010年 | 89篇 |
2009年 | 74篇 |
2008年 | 161篇 |
2007年 | 159篇 |
2006年 | 181篇 |
2005年 | 151篇 |
2004年 | 145篇 |
2003年 | 126篇 |
2002年 | 132篇 |
2001年 | 136篇 |
2000年 | 129篇 |
1999年 | 91篇 |
1998年 | 44篇 |
1997年 | 38篇 |
1996年 | 28篇 |
1995年 | 26篇 |
1994年 | 23篇 |
1993年 | 31篇 |
1992年 | 70篇 |
1991年 | 73篇 |
1990年 | 62篇 |
1989年 | 63篇 |
1988年 | 75篇 |
1987年 | 56篇 |
1986年 | 56篇 |
1985年 | 36篇 |
1984年 | 41篇 |
1983年 | 32篇 |
1982年 | 25篇 |
1981年 | 20篇 |
1980年 | 24篇 |
1979年 | 38篇 |
1978年 | 25篇 |
1977年 | 21篇 |
1976年 | 19篇 |
1975年 | 14篇 |
1974年 | 20篇 |
1973年 | 20篇 |
排序方式: 共有3403条查询结果,搜索用时 0 毫秒
101.
Cloning and nucleotide sequences of the linear DNA killer plasmids from yeast. 总被引:17,自引:11,他引:6
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)
F Hishinuma K Nakamura K Hirai R Nishizawa N Gunge T Maeda 《Nucleic acids research》1984,12(19):7581-7597
The linear DNA killer plasmids (pGKL1 and pGKL2) isolated from a Kluyveromyces lactis killer strain are also maintained and expressed its killer character in Saccharomyces cerevisiae. After these killer plasmid DNAs isolated from S. cerevisiae were treated with alkali, four terminal fragments from each plasmid DNAs were cloned separately. Using these and other cloned DNA fragments, the terminal nucleotide sequences of pGKL2 and the complete nucleotide sequence of pGKL1 were determined. The inverted terminal repetitions of 202 bp and 182 bp were found in pGKL1 and pGKL2, respectively. The pGKL1 sequence showed an extremely high A + T content of 73.2% and it contained five large open reading frames. The largest of these open reading frame was suggested to code for a membrane-bound precursor of glycoprotein subunit of the killer toxin. 相似文献
102.
Transmembrane phospholipid motions induced by F glycoprotein in hemagglutinating virus of Japan.
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Transfer of phospholipid from the envelope of hemagglutinating virus of Japan (HVJ) to erythrocyte (RBC) membrane and the virus-induced transfer of phospholipid between RBC membranes were studied using spin-labeled phosphatidylcholine (PC). The transfer of PC from membranes labeled densely with PC to unlabeled membranes was followed by the peak height increase in the electron spin resonance spectrum. The two kinds of transfer reactions took place very rapidly as reported previously. To obtain further details, the transfer reactions were studied with HVJ, HVJ inactivated by trypsin, HVJ harvested early, HVJ grown in fibroblast cells, the fibroblast HVJ activated by trypsin, influenza virus, and glutaraldehyde-treated RBCs. The results demonstrated that the viral F glycoprotein played a crucial role in the transmembrane phospholipid movements as well as in the fusion and hemolysis of RBCs. The transfer from HVJ to RBC's occurred partially through an exchange mechanism not accompanying the envelope fusion. This was shown by a decrease in the exchange broadening of the electron spin resonance spectrum of released spin-labeled HVJ (HVJ) and also by an increase in the ratio of PC to viral proteins incorporated into RBC membranes. HVJ modified RBC membrane so as to be able to exchange its phospholipids with those of inactive membranes such as fibroblast HVJ, influenza virus, glutaraldehyde-treated RBC'S, and phosphatidylcholine vesicles. HVJ affected the fluidity of RBC membranes markedly, the environments around PC being much fluidized. The virus-induced fusion was discussed based on close apposition of the membranes by HANA proteins and on the destabilization and fluidization of RBC membranes by F glycoproteins. 相似文献
103.
LM cells in which the membrane phospholipids had been modified with choline analogues were infected with vesicular stomatitis virus. The choline analogues tested were choline, N,N'-dimethylethanolamine, N-monomethylethanolamine and ethanolamine. These modifications per se did not affect the syntheses of individual viral proteins. The viral glycoprotein was detected in the plasma membranes of all the modified cells by pronase digestion in pulse-chase experiments, but the amount of glycoprotein susceptible to proteolysis varied, decreasing in these modified cells in the following order: N,N'-dimethylethanolamine- greater than choline- greater than N-monomethylethanolamine- greater than ethanolamine-treated cells. After a 4-h chase, glycoprotein was mainly distributed in the plasma membranes of cells modified with N,N'-dimethylethanolamine, whereas it was found in both the microsomes and plasma membranes of cells modified with other analogues. Fairly large amounts of glycoprotein were also found in the soluble fraction of ethanolamine-treated cells, but not in that of choline- or N,N'-dimethylethanolamine-treated cells. More precise experiments on the behaviour of glycoprotein with a short period of chase strongly suggested that migration of glycoprotein from the microsomes to the plasma membranes was fastest in cells modified with N,N'-dimethylethanolamine and slowest in cells modified with ethanolamine. Membrane lipid modifications also resulted in release of different numbers of progeny virions from the cells, release of virions from the cells decreasing in the following order: N,N'-dimethylethanolamine- greater than choline- greather N-monomethylethanolamine- greater than ethanolamine-treated cells. These results indicate that modification of membrane phospholipids influences not only the insertion of glycoprotein into the microsomes and its migration to the plasma membranes, but also the production of progeny virions. 相似文献
104.
Inoue Mitsugu; Maeda Eizo; Yoshida Ryuji; Oritani Takashi 《Plant & cell physiology》1979,20(5):917-924
Rice callus tissues contained at least three active cytokinincompounds: zeatin, its riboside and N6-(2-isopentenyl) adenosine.These butanol-extractable cytokinins were identified by theirchromatographic mobilities in Sephadex LH-20, paper and gaschromatography. Zeatin, the apparent major cytokinin, was presentat concentrations of 0.7 to 1.0 µg/g fresh tissue and1.3 to 1.7 µg/g fresh tissue in 107 M and 1055M 2,4-D callus, respectively. On the basis of these and earlierresults, the induction and growth of rice callus tissue is discussedin relation to the occurrence of cytokinins in the tissue. (Received December 27, 1978; ) 相似文献
105.
106.
Tadao Maeda Toshikazu Yamaguchi Masahisa Hashimoto 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1981,223(2):357-363
A gas chromatographic method has been developed that permits the accurate and specific determination of the hypoglycaemic agent gliclazide in plasma. Gliclazide is extracted with chloroform and, after clean-up, derivatized with diazomethane followed by heptafluorobutyric anhydride to form N-methyl-N′-heptafluorobutyrylgliclazide, which is assayed on a gas chromatograph equipped with a flame ionization detector, an electron-capture detector or a nitrogen—phosphorus sensitive detector.Accurate determinations are possible with flame ionization detection over a concentration range of 1–15 μg/ml of gliclazide in plasma with a relative standard deviation of 5.2%. The minimum detectable concentration with electron-capture detection is 0.02 μg per sample. Plasma levels of gliclazide in dogs following single oral administration (40 mg per dog) have also been determined. 相似文献
107.
Formation of ribonucleotide 2'',3''-cyclic carbonates during conversion of ribonucleoside 5''-phosphates to diphosphates and triphosphates by the phosphorimidazolidate procedure. 总被引:1,自引:0,他引:1
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)
Ribo- and 2'-deoxyribonucleoside 5'-di- or triphosphates are commonly synthesized by reaction of inorganic phosphate or pyrophosphate with phosphorimidazolidates obtained by reaction of nucleoside 5'-phosphates with 1,1'-carbonyldiimidazole. The latter reaction, however, converted UMP, CMP, IMP, GMP, and AMP in high yield to the 2',3'-cyclic carbonate derivatives of their phosphorimidazolidates. Acidic treatment of the product from AMP gave AMP 2',3'-cyclic carbonate dihydrate; this was characterized by its uv, ir, and pmr spectra and by its conversion to adenosine 2',3'-cyclic carbonate by acid phosphatase and to AMP by basic hydrolysis. ADP or ATP synthesized by the phosphorimidazolidate method contained equal or greater amounts of their respective 2',3'-cyclic carbonates. The latter could be quantitatively converted to ADP and ATP, respectively, by 4-hr hydrolysis at pH 10.5, 22 degrees. ADP or ATP can be synthesized without concomitant 2',3'-cyclic carbonate formation by reaction of AMP with phosphorimidazolidates of inorganic phosphate or pyrophosphate. 相似文献
108.
There are clones of myeloid leukemic cells that can be induced to differentiate by the normal differentiation-inducing protein MGI to form Fc and C3 rosettes, mature macrophages and granulocytes. One of these clones (MGI+DMSO+) was also inducible by dimethylsulfoxide (DMSO) for C3 but not Fc rosettes, and for mature macrophages but not for mature granulocytes. Other clones (MGI+DMSO-) were inducible by MGI but not DMSO and a third type of clone (MGI-DMSO-) was not inducible by either compound. Clones that differed in their inducibility by DMSO showed a similar inhibition of cell multiplication by DMSO. The results indicate, that some stages of differentiation can be induced by DMSO in an appropriate clone of myeloid leukemic cells and that there are different cellular sites for induction by DMSO and MGI. 相似文献
109.
Expression of cDNA for batroxobin, a thrombin-like snake venom enzyme 总被引:11,自引:0,他引:11
The cloned cDNA for batroxobin has been expressed in E. coli. Batroxobin could only be obtained as intracellular aggregates of fusion proteins, fused with a small peptide. To obtain the mature batroxobin, the recognition sequence for thrombin was inserted between the peptide and the mature batroxobin. This fusion protein accumulated in an insoluble form and could easily be purified. After site-specific cleavage of the fusion protein with thrombin, recombinant batroxobin was isolated by preparative electrophoresis. Batroxobin with enzymatic activity was obtained by the refolding of recombinant batroxobin. 相似文献
110.
Two genes, atpC1 and atpC2, for the gamma subunit of Arabidopsis thaliana chloroplast ATP synthase. 总被引:2,自引:0,他引:2
N Inohara A Iwamoto Y Moriyama S Shimomura M Maeda M Futai 《The Journal of biological chemistry》1991,266(12):7333-7338
Arabidopsis thaliana has two genes (atpC1, atpC2) coding for gamma subunits of chloroplast ATP synthase. The atpC1 and atpC2 were cloned and sequenced. They had no introns within the reading frames and coded for proteins of 373 and 386 amino acid residues, respectively, including putative transit sequences (50 and 60 amino acid residues, respectively). In contrast, the spinach gamma subunit gene had two introns within the reading frame. The mature sequences coded by the two genes of A. thaliana (atpC1, 323 residues; atpC2, 326 residues) were homologous with that of spinach (J. Miki, M. Maeda, Y. Mukohata, and M. Futai (1988) FEBS Lett. 232, 221-226): the homologies of gamma subunits coded by atpC1 and atpC2 were 72%, those of the subunits coded by atpC1 and spinach cDNA were 84%, and those of the proteins coded by atpC2 and spinach cDNA were 71%. Like the spinach subunit, the gamma subunits coded by the two genes had unique regulatory domains not found in mitochondrial or bacterial subunits. Poly(A)+ mRNAs corresponding to atpC1 (1.5 kilobases) and atpC2 (2.5 kilobases) were detected in illuminated plants, the amount of the former being at least 140 times that of the latter. The atpC1 mRNA was not found in dark-adapted plants. Nuclear protein(s) specifically bound to the upstream region of atpC1 was detected by gel shift assay and its binding was shown to be inhibited by the GT-1 element of the gene encoding the ribulose-1,5-bisphosphate carboxylase small subunit, which is expressed under illumination (P. J. Green, S. A. Kay, and N. H. Chau (1987) EMBO J. 6, 2543-2549). Consistent with these findings, an increased amount of the gamma subunit was detected immunochemically in illuminated plants. 相似文献