全文获取类型
收费全文 | 963966篇 |
免费 | 113068篇 |
国内免费 | 616篇 |
专业分类
1077650篇 |
出版年
2016年 | 10617篇 |
2015年 | 15845篇 |
2014年 | 18170篇 |
2013年 | 25942篇 |
2012年 | 29216篇 |
2011年 | 29299篇 |
2010年 | 19774篇 |
2009年 | 18631篇 |
2008年 | 26825篇 |
2007年 | 27516篇 |
2006年 | 25768篇 |
2005年 | 24975篇 |
2004年 | 24643篇 |
2003年 | 23888篇 |
2002年 | 23195篇 |
2001年 | 40916篇 |
2000年 | 41262篇 |
1999年 | 33301篇 |
1998年 | 12848篇 |
1997年 | 13537篇 |
1996年 | 12989篇 |
1995年 | 12147篇 |
1994年 | 12017篇 |
1993年 | 11896篇 |
1992年 | 28092篇 |
1991年 | 27445篇 |
1990年 | 26914篇 |
1989年 | 26266篇 |
1988年 | 24240篇 |
1987年 | 23667篇 |
1986年 | 21728篇 |
1985年 | 21937篇 |
1984年 | 18337篇 |
1983年 | 15960篇 |
1982年 | 12717篇 |
1981年 | 11360篇 |
1980年 | 10833篇 |
1979年 | 17681篇 |
1978年 | 14126篇 |
1977年 | 13035篇 |
1976年 | 12278篇 |
1975年 | 13365篇 |
1974年 | 14481篇 |
1973年 | 14202篇 |
1972年 | 12744篇 |
1971年 | 11828篇 |
1970年 | 10267篇 |
1969年 | 9801篇 |
1968年 | 8867篇 |
1967年 | 7893篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
351.
C.J. Handley G. Speight K.M. Leyden D.A. Lowther 《Biochimica et Biophysica Acta (BBA)/General Subjects》1980,627(3):324-331
THe incorporation of [3H]glycine into acid-insoluble protein and of [3H]acetate into glysoaminoglycans by cultured chick chondrocytes was stimulated by the addition of L-glutamine to the incubation medium. The effect of exogenous L-glutamine on protein synthesis was studied further by examining changes in the sedimentation patterns on sucrose gardients of ribosomes isolated from chondrocytes incubated in presence and absence of L-glutamine. It was found that the absence of L-glutamine caused a disaggregation of poly-ribosomes that was reversed by the addition of this amino acid to the culture medium. No detectable glutamine synthetase activity could be measured in avian articular cartilage. These results indicate that L-glutamine is an essential amino acid for cartilage in that an extracellular supply of this amino acid is required for the maintenance of protein and glycosaminoglycan synthesis. A dependence on L-glutamine was also demonstrated for other avain connective tissues. 相似文献
352.
J R Ashton 《BMJ (Clinical research ed.)》1983,287(6398):1001-1002
353.
M Minnich F Kueppers H James 《Comparative biochemistry and physiology. B, Comparative biochemistry》1984,78(2):413-419
Alpha-1-antitrypsin (alpha-1-protease inhibitor) was isolated from mouse serum by a series of electrophoretic and chromatographic steps. We found it to be a glycoprotein of a mass ratio of 57.7 Kd. The extinction coefficient was E1%1cm,280=4.74. It inhibits bovine trypsin, human granulocytic and porcine pancreatic elastase. Its concentration in serum differs between inbred strains. Of those tested the concentration in C57BL/6J males was lowest with 5.58 +/- 0.71 mg/ml (females: 3.02 +/- 0.39) and that in DBA/2J was highest: 8.5 +/- 0.87 mg/ml (females: 4.09 +/- 0.51). The concentration of alpha-1-antitrypsin in male serum was almost twice as high as that in females of all strains tested. 相似文献
354.
355.
David M. Anderson Richard H. Scheller James W. Posakony Linda B. McAllister Steven G. Trabert Clifford Beall Roy J. Britten Eric H. Davidson 《Journal of molecular biology》1981,145(1):5-28
Three repetitive sequence families from the sea urchin genome were studied, each defined by homology with a specific cloned probe one to a few hundred nucleotides long. Recombinant λ-sea urchin DNA libraries were screened with these probes, and individual recombinants were selected that include genomic members of these families. Restriction mapping, gel blot, and kinetic analyses were carried out to determine the organization of each repeat family. Sequence elements belonging to the first of the three repeat families were found to be embedded in longer repeat sequences. These repeat sequences frequently occur in small clusters. Members of the second repeat family are also found in a long repetitive sequence environment, but these repeats usually occur singly in any given region of the DNA. The sequences of the third repeat are only 200 to 300 nucleotides long, and are generally terminated by single copy DNA, though a few examples were found associated with other repeats. These three repeat sequence families constitute sets of homologous sequence elements that relate distant regions of the DNA. 相似文献
356.
James F. Richards Kulgite Lit Roland Fuca Catherine Bourgeault 《Biochemical and biophysical research communications》1981,99(4):1461-1467
Several species of ornithine decarboxylase were separated by chromatography of rat thymus and kidney extracts on DEAE-Sepharose CL-6B. One major and one minor species were absent from thymus of rats two hours after hormone treatment but otherwise, the elution profile was identical to thymus from control animals. The elution patterns of ODC activity in kidneys of rats treated 2.5 or 5 hours before sacrifice with dexamethasone differ from that of control kidney and from each other. Enzyme from kidneys early after hormone treatment is eluted earlier than enzyme from control tissue, while at 5 hours, the enzyme is eluted much later than in the control. This suggests that the hormone-induced activity is subsequently modified. 相似文献
357.
A F Wright 《BMJ (Clinical research ed.)》1982,285(6342):609-611
358.
359.
J F Searle 《BMJ (Clinical research ed.)》1984,288(6435):1998-1999
360.
Sylvester J. T.; Harabin A. L.; Peake M. D.; Frank R. S. 《Journal of applied physiology》1980,49(5):820-825