全文获取类型
收费全文 | 1658篇 |
免费 | 189篇 |
国内免费 | 1篇 |
出版年
2022年 | 8篇 |
2021年 | 23篇 |
2020年 | 14篇 |
2019年 | 15篇 |
2018年 | 26篇 |
2017年 | 26篇 |
2016年 | 30篇 |
2015年 | 76篇 |
2014年 | 44篇 |
2013年 | 79篇 |
2012年 | 95篇 |
2011年 | 102篇 |
2010年 | 63篇 |
2009年 | 54篇 |
2008年 | 83篇 |
2007年 | 72篇 |
2006年 | 75篇 |
2005年 | 63篇 |
2004年 | 61篇 |
2003年 | 66篇 |
2002年 | 79篇 |
2001年 | 55篇 |
2000年 | 62篇 |
1999年 | 62篇 |
1998年 | 40篇 |
1997年 | 33篇 |
1996年 | 21篇 |
1995年 | 30篇 |
1994年 | 29篇 |
1993年 | 29篇 |
1992年 | 33篇 |
1991年 | 39篇 |
1990年 | 29篇 |
1989年 | 19篇 |
1988年 | 23篇 |
1987年 | 13篇 |
1986年 | 13篇 |
1985年 | 25篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 9篇 |
1979年 | 11篇 |
1978年 | 11篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1975年 | 10篇 |
1974年 | 7篇 |
1973年 | 9篇 |
1971年 | 6篇 |
1968年 | 6篇 |
排序方式: 共有1848条查询结果,搜索用时 46 毫秒
51.
Double-stranded cDNA of in vitro polyadenylated tobacco streak virus (TSV) RNA 3 has been cloned and sequenced. The complete primary structure of 2,205 nucleotides reveals two open reading frames flanked by a leader sequence of 210 bases, an intercistronic region of 123 nucleotides and a 3'-extracistronic sequence of 288 nucleotides. The 5'-terminal open reading frame codes for a Mr 31,742 protein, which probably corresponds to the only in vitro translation product of TSV RNA 3. The 3'-terminal coding region predicts a Mr 26,346 protein, probably the viral coat protein, which is the translation product of the subgenomic messenger, RNA 4. Although the coat proteins of alfalfa mosaic virus (A1MV) and TSV are functionally equivalent in activating their own and each others genomes, no homology between the primary structures of those two proteins is detectable. 相似文献
52.
Glutamine synthetase of Klebsiella aerogenes: genetic and physiological properties of mutants in the adenylylation system. 总被引:17,自引:14,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)
Mutations resulting in defects in the adenylylation system of glutamine synthetase (GS) affect the expression of glnA, the structural gene for GS. Mutants with lesions in glnB are glutamine auxotrophs and contain repressed levels of highly adenylylated GS. Glutamine-independent revertants of the glnB3 mutant have acquired an additional mutation at the glnE site. The glnE54 mutant is incapable of adenylylating GS and produces high levels of enzyme, even when ammonia is present in the growth medium. The fact that mutations in glnB and glnE simultaneously disturb both the normal adenylylation and repression patterns of GS in Klebsiella aerogenes indicates that the adenylylation system, or adenylylation state, of GS is critical for the regulation of synthesis of GS. 相似文献
53.
Characterization of glutamine-requiring mutants of Pseudomonas aeruginosa. 总被引:1,自引:0,他引:1
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)
Revertants were isolated from a glutamine-requiring mutant of Pseudomonas aeruginosa PAO. One strain showed thermosensitive glutamine requirement and formed thermolabile glutamine synthase, suggesting the presence of a mutation in the structural gene for glutamine synthetase. The mutation conferring glutamine auxotrophy was subsequently mapped and found to be located at about 15 min on the chromosomal map, close to and before hisII4. Furthermore, in transduction experiments, it appeared to be very closely linked to gln-2022, a suppressor mutation affecting nitrogen control. With immunological techniques, it could be demonstrated that the glutamine auxotrophs form an inactive glutamine synthetase protein which is regulated by glutamine or a product derived from it in a way similar to other nitrogen-controlled proteins. 相似文献
54.
By indirect immunoelectron microscopy we tested for the presence of H-2 antigens on murine mammary tumor virus (MMTV) and murine leukemia virus (MuLV) particles. The association of H-2 antigens and viral antigens on the virus-infected cell surface was investigated with antibody-induced redistribution. Mammary tumor cells and leukemia cell lines with different H-2 genotypes and carrying different MuMTV or MuLV were used. No H-2 antigens could be demonstrated on the envelope of MMTV and MuLV particles, even after the permeabilization of their envelopes with saponin. On the surface of virus-infected cells antibody-induced patching or capping of the viral antigens did not result in copatching or cocapping of the H-2 antigens. In the reciprocal tests no co-redistribution of viral antigens with H-2 antigens was seen. Our experiments failed to show any physical association between H-2 antigens and MMTV or MuLV antigens on the cell surface.Abbreviations used in this paper MMTV
mammary tumor virus
- MuLV
murine leukemia virus
- MHC
major histocompatibility complex
- IEM
immunelectron microscopy 相似文献
55.
A major substrate of maturation promoting factor identified as elongation factor 1 beta gamma delta in Xenopus laevis 总被引:9,自引:0,他引:9
G M Janssen J Morales A Schipper J C Labbé O Mulner-Lorillon R Bellé W M?ller 《The Journal of biological chemistry》1991,266(23):14885-14888
Protein synthesis is believed to be under control of the cell cycle during meiosis and mitosis. Any relationship between substrates for cdc2 kinase and components of the protein synthetic apparatus would therefore be of prime importance. During meiosis of Xenopus laevis oocytes one of the substrates for this kinase is a p47 protein, which is complexed to two other proteins, P36 and P30. Judged from partial amino acid sequence data on P47 and P30, the P30 and P47 proteins were reported to resemble the protein synthetic elongation factors (EF) 1 beta and 1 gamma from Artemia salina (Bellé, R., Derancourt, J., Poulhe, R., Capony, J.P., Ozon, R., and Mulner-Lorillon, O. (1989) FEBS Lett. 255, 101-104). This paper shows that the complex composed of P30, P47, and P36 from Xenopus is identical to the complex of EF-1 beta, EF-1 gamma, and EF-1 delta from Artemia according to two criteria. 1) Both stimulate elongation factor 1 alpha-mediated transfer RNA binding to ribosomes and exchange of guanine nucleotides on elongation factor 1 alpha to a comparable degree. 2) Each of the three subunits of the protein complex P30.P47.P36 from Xenopus shows a structural homology with one of the corresponding subunits of EF-1 beta gamma delta from Artemia. Presumably the phosphorylation of EF-1 gamma, which associates with tubulin at least in vitro, is important in processes following the onset of meiosis which is accompanied by a rise of protein synthesis. 相似文献
56.
T cell receptor/CD3-signaling induces death by apoptosis in human T cell receptor gamma delta + T cells. 总被引:14,自引:0,他引:14
O Janssen S Wesselborg B Heckl-Ostreicher K Pechhold A Bender S Schondelmaier G Moldenhauer D Kabelitz 《Journal of immunology (Baltimore, Md. : 1950)》1991,146(1):35-39
mAb directed against the TCR/CD3 complex activate resting T cells. However, TCR/CD3 signaling induces death by apoptosis in immature (CD4+CD8+) murine thymocytes and certain transformed leukemic T cell lines. Here we show that anti-TCR and anti-CD3 mAb induce growth arrest of cloned TCR-gamma delta + T cells in the presence of IL-2. In the absence of exogenous IL-2, however, the very same anti-TCR/CD3 mAb stimulated gamma delta (+)-clones to proliferation and IL-2 production. In the presence of exogenous IL-2, anti-TCR/CD3 mAb induced the degradation of DNA into oligosomal bands of approximately 200 bp length in cloned gamma delta + T cells. This pattern of DNA fragmentation is characteristic for the programmed cell death termed apoptosis. These results demonstrate that TCR/CD3 signaling can induce cell death in cloned gamma delta + T cells. In addition, this report is the first to show that apoptosis triggered by TCR/CD3 signaling is not restricted to CD4+CD8+ immature thymocytes and transformed leukemic T cell lines but can be also observed with IL-2-dependent normal (i.e., TCR-gamma delta +) T cells. 相似文献
57.
Purification and characterization of haloalcohol dehalogenase from Arthrobacter sp. strain AD2. 总被引:9,自引:3,他引:6
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)
An enzyme capable of dehalogenating vicinal haloalcohols to their corresponding epoxides was purified from the 3-chloro-1,2-propanediol-utilizing bacterium Arthrobacter sp. strain AD2. The inducible haloalcohol dehalogenase converted 1,3-dichloro-2-propanol, 3-chloro-1,2-propanediol, 1-chloro-2-propanol, and their brominated analogs, 2-bromoethanol, as well as chloroacetone and 1,3-dichloroacetone. The enzyme possessed no activity for epichlorohydrin (3-chloro-1,2-epoxypropane) or 2,3-dichloro-1-propanol. The dehalogenase had a broad pH optimum at about 8.5 and a temperature optimum of 50 degrees C. The enzyme followed Michaelis-Menten kinetics, and the Km values for 1,3-dichloro-2-propanol and 3-chloro-1,2-propanediol were 8.5 and 48 mM, respectively. Chloroacetic acid was a competitive inhibitor, with a Ki of 0.50 mM. A subunit molecular mass of 29 kDa was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. With gel filtration, a molecular mass of 69 kDa was found, indicating that the native protein is a dimer. The amino acid composition and N-terminal amino acid sequence are given. 相似文献
58.
G Schieren O Janssen G M H?nsch 《Journal of immunology (Baltimore, Md. : 1950)》1992,148(10):3183-3188
C8 binding protein (C8bp) is a 65-kDa membrane glycoprotein that inhibits complement-mediated lysis by homologous C5b-9. C8bp was first identified on human erythrocytes, but could also be detected on peripheral blood cells, platelets, glomerular cells and synovial fibroblasts. Lack of C8bp as seen in patients with paroxysmal nocturnal hemoglobinuria type III results in enhanced susceptibility of the cells toward C5b-9. We studied C8bp expression on the promonocytic cell line U937. In addition to the membrane-bound C8bp, a cytoplasmic form of C8bp could also be identified by immunofluorescence, blotting, and precipitation. Stimulation of the cells with IL-1 beta, endotoxin, IFN-gamma, or phorbol ester increased C8bp surface expression. Because cycloheximide did not inhibit enhanced surface expression, it was most probably mobilized from cytoplasmic reservoirs. Thus, resistance of nuclear cells to complement attack seems to be based on two events: 1) the removal of the C5b-9 complex from the membrane; and 2) expression of regulatory surface proteins such as C8bp, which inhibit C5b-9-mediated lysis. We propose that the C8bp mobilization by cytokines might provide an additional protection against complement attack by its known interference with the C5b-9 assembly. 相似文献
59.
Peter H. Janssen 《Antonie van Leeuwenhoek》1991,59(3):191-198
Enrichments on L-tartrate from a freshwater lake sediment yielded a pure culture of anaerobic bacterium designated strain 16Lt1. The rod-shaped organism was motile, did not form spores, and had a gram-negative wall structure. No cytochromes were detected. The mol % G+C of the DNA was 58. The new strain was microaerotolerant, and grew optimally at 30°C and neutral pH in freshwater medium. A wide range of carbohydrates was fermented, with formate, acetate, ethanol, lactate and succinate being the end-products detected. L-tartrate and citrate were fermented to formate, acetate and CO2. L-tartrate was fermented by the dehydratase pathway, and glucose by the Embden-Meyerhof-Parnas pathway. Fumarate was reduced, but nitrate, sulfate, sulfur and thiosulfate were not used as terminal electron acceptors. Glucose metabolism was constitutive, whereas L-tartrate-degrading activity was inducible. When glucose and L-tartrate were both present as substrates, growth was diauxic with glucose being metabolized first. The growth rate and growth yield were higher on glucose than on L-tartrate. Strain 16Lt1 has been deposited with the Deutsche Sammlung von Mikroorganismen as Bacteroides sp. DSM6268. 相似文献
60.
W D Nes G G Janssen R A Norton M Kalinowska F G Crumley B Tal A Bergenstrahle L Jonsson 《Biochemical and biophysical research communications》1991,177(1):566-574
Whereas sitosterol and 24(28)-methylene cycloartanol were competitive inhibitors (with Ki = 26 microM and 14 microM, respectively), 24(R,S)-25-epiminolanosterol was found to be a potent non-competitive inhibitor (Ki = 3.0 nM) of the S-adenosyl-L-methionine-C-24 methyl transferase from sunflower embryos. Because the ground state analog, 24(R,S)-oxidolanosterol, failed to inhibit the catalysis and 25-azalanosterol inhibited the catalysis with a Ki of 30 nM we conclude that the aziridine functions in a manner similar to the azasteriod (Rahier, A., et al., J. Biol. Chem. (1984) 259, 15215) as a transition state analog mimicking the carbonium intermediate found in the normal transmethylation reaction. Additionally, we observed that the aziridine inhibited cycloartenol metabolism (the preferred substrate for transmethylation) in cultured sunflower cells and cell growth. 相似文献