全文获取类型
收费全文 | 191945篇 |
免费 | 14481篇 |
国内免费 | 61篇 |
出版年
2023年 | 943篇 |
2022年 | 1318篇 |
2021年 | 2699篇 |
2020年 | 2105篇 |
2019年 | 2397篇 |
2018年 | 4375篇 |
2017年 | 3883篇 |
2016年 | 5708篇 |
2015年 | 8321篇 |
2014年 | 8578篇 |
2013年 | 11372篇 |
2012年 | 13450篇 |
2011年 | 12541篇 |
2010年 | 8144篇 |
2009年 | 6625篇 |
2008年 | 9946篇 |
2007年 | 9799篇 |
2006年 | 9088篇 |
2005年 | 8876篇 |
2004年 | 8525篇 |
2003年 | 7644篇 |
2002年 | 6910篇 |
2001年 | 4168篇 |
2000年 | 4020篇 |
1999年 | 3541篇 |
1998年 | 1751篇 |
1997年 | 1441篇 |
1996年 | 1423篇 |
1995年 | 1297篇 |
1994年 | 1217篇 |
1993年 | 1114篇 |
1992年 | 2445篇 |
1991年 | 2250篇 |
1990年 | 2043篇 |
1989年 | 1936篇 |
1988年 | 1853篇 |
1987年 | 1649篇 |
1986年 | 1541篇 |
1985年 | 1551篇 |
1984年 | 1416篇 |
1983年 | 1136篇 |
1982年 | 933篇 |
1981年 | 918篇 |
1980年 | 812篇 |
1979年 | 1174篇 |
1978年 | 942篇 |
1977年 | 808篇 |
1975年 | 826篇 |
1974年 | 896篇 |
1973年 | 880篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Morphological taxonomy of simple Hyphomycetes is complicated by the frequent occurrence of pleoanamorphism. In some groups
of yeast-like fungi, uncommon synanamorphs are diagnostic. Differences in conidiogenesis do not always delimit natural groups.
Some nomenclatural problems are mentioned, with an emphasis on the need of neotypification. Prospects are sketched for future
taxonomic research. 相似文献
52.
Occurrence of multiple-antibiotic-resistant enteric bacteria in domestic sewage and oxidation lagoons 总被引:1,自引:0,他引:1
The coliform bacterial population in the Grand Forks, N.Dak. sewage system was examined for multiple-antibiotic-resistant organisms over a 1-year period. Multiple-antibiotic-resistant coliforms were found to be common in the sewage, and their numbers remained fairly constant relative to the total coliform population throughout the year. Resistance to kanamycin, tetracycline, and ampicillin was found to be transferable at variable rates. Transfer rates were found to be temperature sensitive and were optimal at 35 degrees C. Although 75% of the multiple-antibiotic-resistant coliforms were capable of transferring resistance at some level, only 25% were capable of transferring resistance at rates greater than 10(-3) transconjugants per initial donor. 相似文献
53.
C Chong-Cerrillo M E Selsted E M Peterson L M de la Maza 《The journal of peptide research》2003,61(5):237-242
Four antimicrobial peptides, protegrin-1, RTD-1, cryptdin-4, and indolicidin, were tested for their ability to inhibit the in vitro growth of Chlamydia trachomatis serovars E, L2, and mouse pneumonitis (MoPn). In general, protegrin-1 was found to have the strongest anti-chlamydial activity. Overall, of the three serovars tested, L2 was the most susceptible while MoPn was the most resistant to these peptides. 相似文献
54.
55.
56.
Eugénie Bassères Giuseppe Coppotelli Thorsten Pfirrmann Jens B. Andersen Maria Masucci Teresa Frisan 《Cellular microbiology》2010,12(11):1622-1633
Invasion of eukaryotic target cells by pathogenic bacteria requires extensive remodelling of the membrane and actin cytoskeleton. Here we show that the remodelling process is regulated by the ubiquitin C‐terminal hydrolase UCH‐L1 that promotes the invasion of epithelial cells by Listeria monocytogenes and Salmonella enterica. Knockdown of UCH‐L1 reduced the uptake of both bacteria, while expression of the catalytically active enzyme promoted efficient internalization in the UCH‐L1‐negative HeLa cell line. The entry of L. monocytogenes involves binding to the receptor tyrosine kinase Met, which leads to receptor phosphorylation and ubiquitination. UCH‐L1 controls the early membrane‐associated events of this triggering cascade since knockdown was associated with altered phosphorylation of the c‐cbl docking site on Tyr1003, reduced ubiquitination of the receptor and altered activation of downstream ERK1/2‐ and AKT‐dependent signalling in response to the natural ligand Hepatocyte Growth Factor (HGF). The regulation of cytoskeleton dynamics was further confirmed by the induction of actin stress fibres in HeLa expressing the active enzyme but not the catalytic mutant UCH‐L1C90S. These findings highlight a previously unrecognized involvement of the ubiquitin cycle in bacterial entry. UCH‐L1 is highly expressed in malignant cells that may therefore be particularly susceptible to invasion by bacteria‐based drug delivery systems. 相似文献
57.
58.
M. de Kwaadsteniet C. A. van Reenen L. M. T. Dicks 《Probiotics and antimicrobial proteins》2010,2(2):61-65
The potential of nisin F as an antimicrobial agent in treating subcutaneous skin infections was tested in vivo by infecting C57BL/6 mice with a bioluminescent strain of Staphylococcus aureus (Xen 36). Strain Xen 36 has the luxABCDE operon located on a native plasmid. Mice were grouped into four groups: Infected with strain Xen 36 and treated with nisin F, infected with strain Xen 36 and treated with saline (placebo), not infected and treated with nisin (control) and not infected and not treated (control). The immune systems of the mice were suppressed with deksamethasone. Mice were treated with either nisin F or sterile physiological saline 24 and 48 h after infection with subcutaneously injected S. aureus Xen 36 (4 × 106 CFU). Histology and bioluminescent flux measurements revealed no significant difference between infected mice treated with nisin and saline, respectively. However, infected mice treated with nisin F had an increased number of polymorphonuclear cells when compared with infected mice treated with saline. Also, not infected mice treated with nisin F had an influx of polymorphonuclear cells. Nisin F is thus ineffective in combating deep dermal staphylococcal infections. The apparent immune modulation of nisin when subcutaneously injected has to be investigated. 相似文献
59.
60.
Release of pituitary melanocyte-stimulating hormone by the oxytocin fragment, H-Cys-Tyr-Ile-Gln-Asn-Oh 总被引:5,自引:0,他引:5
M E Celis S Taleisnik R Walter 《Biochemical and biophysical research communications》1971,45(3):564-569
The effect of the pentapeptide H-Cys-Tyr-Ile-Gln-Asn-OH to act like melanocyte-stimulating hormone-releasing factor (MSH-RF) was studied. This peptide decreases at ng amounts the MSH content of the rat pituitary and increases plasma MSH concentration. This agent also stimulates the release of MSH in animals with eminence lesion, indicating a direct action of the pentapeptide on the gland. 相似文献