全文获取类型
收费全文 | 31499篇 |
免费 | 3909篇 |
国内免费 | 29篇 |
出版年
2017年 | 210篇 |
2016年 | 281篇 |
2015年 | 398篇 |
2014年 | 494篇 |
2013年 | 766篇 |
2012年 | 767篇 |
2011年 | 826篇 |
2010年 | 557篇 |
2009年 | 486篇 |
2008年 | 709篇 |
2007年 | 737篇 |
2006年 | 715篇 |
2005年 | 708篇 |
2004年 | 731篇 |
2003年 | 733篇 |
2002年 | 737篇 |
2001年 | 1948篇 |
2000年 | 1914篇 |
1999年 | 1505篇 |
1998年 | 514篇 |
1997年 | 512篇 |
1996年 | 517篇 |
1995年 | 457篇 |
1994年 | 461篇 |
1993年 | 451篇 |
1992年 | 1131篇 |
1991年 | 1132篇 |
1990年 | 1115篇 |
1989年 | 1072篇 |
1988年 | 997篇 |
1987年 | 938篇 |
1986年 | 801篇 |
1985年 | 780篇 |
1984年 | 633篇 |
1983年 | 535篇 |
1982年 | 392篇 |
1981年 | 360篇 |
1980年 | 347篇 |
1979年 | 592篇 |
1978年 | 469篇 |
1977年 | 427篇 |
1976年 | 357篇 |
1975年 | 470篇 |
1974年 | 489篇 |
1973年 | 424篇 |
1972年 | 411篇 |
1971年 | 316篇 |
1970年 | 260篇 |
1969年 | 245篇 |
1968年 | 227篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
The signal sequence suffices to direct export of outer membrane protein OmpA of Escherichia coli K-12. 总被引:8,自引:3,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)
We studied whether information required for export is present within the mature form of the Escherichia coli 325-residue outer membrane protein OmpA. We had previously analyzed overlapping internal deletions in the ompA gene, and the results allowed us to conclude that if such information exists it must be present repeatedly within the membrane part of the protein encompassing amino acid residues 1 to 177 (R. Freudl, H. Schwarz, M. Klose, N. R. Movva, and U. Henning, EMBO J. 4:3593-3598, 1985). A deletion which removed the codons for amino acid residues 1 to 229 of the OmpA protein was constructed. In this construct the signal sequence was fused to the periplasmic part of the protein. The resulting protein, designated Pro-OmpA delta 1-229, was processed, and the mature 95-residue protein accumulated in the periplasm. Hence, information required for export does not exist within the OmpA protein. 相似文献
92.
A nuclear yeast gene (GCY) encodes a polypeptide with high homology to a vertebrate eye lens protein 总被引:2,自引:0,他引:2
We describe here the nuclear gene for a yeast protein showing unexpectedly high homology with mammalian aldo/keto reductases as well as with p-crystallin, one of the prominent proteins of the frog eye lens. Although it could be proven that the gene occurs as a single copy in the haploid yeast genome, replacement of the intact by a disrupted, nonfunctional allele led to no obvious phenotype, indicating that the gene is dispensable. The gene was assigned to chromosome XV. It is transcribed in vivo into an mRNA of about 1300 bases with a coding capacity for a protein of 312 amino acids (estimated Mr 35,000). 相似文献
93.
Intraperitoneal injections of 6-OH-dopamine (80 mg kg−l ) promote, in toad fish, killifish, lsummer and winter flounders, a darkening of their colour and loss of capacity to adapt tolthe colour of the background. This condition persisted for three weeks after which thelanimals gradually returned to normal. The study of the skin of 6-hydroxydopamineltreated killifish showed degenerative lesions in the fine nerves and synapses of its melanophores, 124 h after the administration of the drug. These lesions progressed and 4 days later, lno synaptic structures could be detected in these cells. This condition persisted up to thel20th day. These results suggest that melanophores have a single monoaminergic innervaion. 相似文献
94.
95.
96.
97.
M Magnani L Chiarantini E Vittoria U Mancini L Rossi A Fazi 《Biotechnology and applied biochemistry》1992,16(2):188-194
The use of adjuvants is usually required to induce strong immunological responses to protein antigens. However, in many cases these adjuvants cannot be extensively applied in human and veterinary vaccinations because of associated inflammatory reactions or granuloma formation. We show here that protein antigens (bovine serum albumin, hog liver uricase, and yeast hexokinase), coupled to autologous red blood cells by way of a biotin-avidin-biotin bridge, elicit an immunological response in mice similar to or higher than that obtained by the use of Freund's adjuvant. Quantities as low as 0.5 micrograms/mouse are high enough to generate these immunological responses. Furthermore, splenocytes of mice immunized by red blood cell-coupled antigens can be used to generate hybridomas secreting monoclonal antibodies. Thus, the delivery of antigens by autologous red blood cells is an effective way to avoid the use of adjuvants for producing anti-peptide antibodies and possibly to generate peptide vaccines. 相似文献
98.
U. M. X. Sangodkar T. L. Aldrich R. A. Haugland J. Johnson R. K. Rothmel P. J. Chapman A. M. Chakrabarty 《Engineering in Life Science》1989,9(4):301-316
Chlorinated aromatic hydrocarbons are widely used in industry and agriculture, and comprise the bulk of environmental pollutants. Although simple aromatic compounds are biodegradable by a variety of degradative pathways, their halogenated counterparts are more resistant to bacterial attack and often necessitate evolution of novel pathways. An understanding of such evolutionary processes is essential for developing genetically improved strains capable of mineralizing highly chlorinated compounds. This article provides an overview of the genetic aspects of dissimilation of chloroaromatic compounds and discusses the potential of gene manipulation to promote enhanced evolution of the degradative pathways. 相似文献
99.
100.
Cadmium ions introduced at concentration of 30 ppm to the cultivation medium of synchronously growing Chlorella vulgaris decreased concentration of chlorophylls a and b, carotenes alpha and beta and lutein at various stages of the cell cycle, while at concentration of 1 ppm synthesis of the photosynthetic pigments was stimulated. The pigment content in the cadmium treated cells was related to the morphometrically determined changes in the size and shape of the cells. 相似文献