全文获取类型
收费全文 | 27868篇 |
免费 | 2681篇 |
国内免费 | 9篇 |
出版年
2022年 | 151篇 |
2021年 | 377篇 |
2020年 | 236篇 |
2019年 | 250篇 |
2018年 | 348篇 |
2017年 | 326篇 |
2016年 | 626篇 |
2015年 | 1006篇 |
2014年 | 1125篇 |
2013年 | 1417篇 |
2012年 | 1878篇 |
2011年 | 1936篇 |
2010年 | 1224篇 |
2009年 | 1140篇 |
2008年 | 1530篇 |
2007年 | 1635篇 |
2006年 | 1421篇 |
2005年 | 1421篇 |
2004年 | 1449篇 |
2003年 | 1431篇 |
2002年 | 1294篇 |
2001年 | 467篇 |
2000年 | 358篇 |
1999年 | 461篇 |
1998年 | 434篇 |
1997年 | 309篇 |
1996年 | 304篇 |
1995年 | 299篇 |
1994年 | 287篇 |
1993年 | 279篇 |
1992年 | 305篇 |
1991年 | 257篇 |
1990年 | 268篇 |
1989年 | 235篇 |
1988年 | 262篇 |
1987年 | 238篇 |
1986年 | 208篇 |
1985年 | 250篇 |
1984年 | 241篇 |
1983年 | 209篇 |
1982年 | 228篇 |
1981年 | 215篇 |
1980年 | 198篇 |
1979年 | 170篇 |
1978年 | 173篇 |
1977年 | 145篇 |
1976年 | 155篇 |
1975年 | 131篇 |
1974年 | 141篇 |
1973年 | 123篇 |
排序方式: 共有10000条查询结果,搜索用时 625 毫秒
21.
22.
Xinzhu Deng David Michaelson Jason Tchieu Jin Cheng Diana Rothenstein Regina Feldman Sang-gyu Lee John Fuller Adriana Haimovitz-Friedman Lorenz Studer Simon Powell Zvi Fuks E. Jane Albert Hubbard Richard Kolesnick 《PloS one》2015,10(6)
Mammalian NOTCH1-4 receptors are all associated with human malignancy, although exact roles remain enigmatic. Here we employ glp-1(ar202), a temperature-sensitive gain-of-function C. elegans NOTCH mutant, to delineate NOTCH-driven tumor responses to radiotherapy. At ≤20°C, glp-1(ar202) is wild-type, whereas at 25°C it forms a germline stem cell⁄progenitor cell tumor reminiscent of human cancer. We identify a NOTCH tumor phenotype in which all tumor cells traffic rapidly to G2⁄M post-irradiation, attempt to repair DNA strand breaks exclusively via homology-driven repair, and when this fails die by mitotic death. Homology-driven repair inactivation is dramatically radiosensitizing. We show that these concepts translate directly to human cancer models. 相似文献
23.
24.
25.
Ratul Saha Robert S. Donofrio Susan T. Bagley 《Journal of industrial microbiology & biotechnology》2010,37(8):843-848
A TaqMan quantitative real-time polymerase chain reaction (qPCR) assay was developed for the detection and enumeration of
three Pseudomonas species belonging to the mendocina sublineage (P. oleovorans, P. pseudoalcaligenes, and P. oleovorans subsp. lubricantis) found in contaminated metalworking fluids (MWFs). These microbes are the primary colonizers and serve as indicator organisms
of biodegradation of used MWFs. Molecular techniques such as qPCR are preferred for the detection of these microbes since
they grow poorly on typical growth media such as R2A agar and Pseudomonas isolation agar (PIA). Traditional culturing techniques not only underestimate the actual distribution of these bacteria but
are also time-consuming. The primer–probe pair developed from gyrase B (gyrB) sequences of the targeted bacteria was highly sensitive and specific for the three species. qPCR was performed with both
whole cell and genomic DNA to confirm the specificity and sensitivity of the assay. The sensitivity of the assay was 101 colony forming units (CFU)/ml for whole cell and 13.7 fg with genomic DNA. The primer–probe pair was successful in determining
concentrations from used MWF samples, indicating levels between 2.9 × 103 and 3.9 × 106 CFU/ml. In contrast, the total count of Pseudomonas sp. recovered on PIA was in the range of <1.0 × 101 to 1.4 × 105 CFU/ml for the same samples. Based on these results from the qPCR assay, the designed TaqMan primer–probe pair can be efficiently
used for rapid (within 2 h) determination of the distribution of these species of Pseudomonas in contaminated MWFs. 相似文献
26.
27.
M A Taylor K A Pratt D F Revell K C Baker I G Sumner P W Goodenough 《Protein engineering》1992,5(5):455-459
For the first time the pro-form of a recombinant cysteine proteinase has been expressed at a high level in Escherichia coli. This inactive precursor can subsequently be processed to yield active enzyme. Sufficient protein can be produced using this system for X-ray crystallographic structure studies of engineered proteinases. A cDNA clone encoding propapain, a precursor of the papaya proteinase, papain, was expressed in E. coli using a T7 polymerase expression system. Insoluble recombinant protein was solubilized in 6 M guanidine hydrochloride and 10 mM dithiothreitol, at pH 8.6. A protein-glutathione mixed disulphide was formed by dilution into oxidized glutathione and 6 M GuHCl, also at pH 8.6. Final refolding and disulphide bond formation was induced by dilution into 3 mM cysteine at pH 8.6. Renatured propapain was processed to active papain at pH 4.0 in the presence of excess cysteine. Final processing could be inhibited by the specific cysteine proteinase inhibitors E64 and leupeptin, but not by pepstatin, PMSF or EDTA. This indicates that final processing was due to a cysteine proteinase and suggests that an autocatalytic event is required for papain maturation. 相似文献
28.
Background
While traditional models of Alzheimer's disease focused on large fibrillar deposits of the Aβ42 amyloid peptide in the brain, recent work suggests that the major pathogenic effects may be attributed to SDS-stable oligomers of Aβ42. These Aβ42 oligomers represent a rational target for therapeutic intervention, yet factors governing their assembly are poorly understood. 相似文献29.
Hydrogen bonding in globular proteins 总被引:41,自引:0,他引:41
30.
Jane Stewart 《CMAJ》1995,153(4):459-462
The CMA''s incoming president is Dr. Jack Armstrong, a Winnipeg pediatrician with a particular interest in aboriginal issues. Armstrong, who graduated from the University of Manitoba in 1966, considers himself a team player. “You have to be a part of a team. My job is to try to be as good a spokesperson as possible, along with the other team members, for the physicians of the country.” 相似文献