全文获取类型
收费全文 | 11822篇 |
免费 | 1340篇 |
国内免费 | 3篇 |
专业分类
13165篇 |
出版年
2022年 | 76篇 |
2021年 | 134篇 |
2020年 | 142篇 |
2019年 | 222篇 |
2018年 | 240篇 |
2017年 | 257篇 |
2016年 | 324篇 |
2015年 | 526篇 |
2014年 | 531篇 |
2013年 | 723篇 |
2012年 | 708篇 |
2011年 | 635篇 |
2010年 | 532篇 |
2009年 | 465篇 |
2008年 | 565篇 |
2007年 | 581篇 |
2006年 | 568篇 |
2005年 | 614篇 |
2004年 | 580篇 |
2003年 | 628篇 |
2002年 | 634篇 |
2001年 | 122篇 |
2000年 | 102篇 |
1999年 | 156篇 |
1998年 | 199篇 |
1997年 | 142篇 |
1996年 | 142篇 |
1995年 | 142篇 |
1994年 | 123篇 |
1993年 | 90篇 |
1992年 | 129篇 |
1991年 | 100篇 |
1990年 | 91篇 |
1989年 | 93篇 |
1988年 | 72篇 |
1987年 | 87篇 |
1986年 | 81篇 |
1985年 | 95篇 |
1984年 | 102篇 |
1983年 | 83篇 |
1982年 | 107篇 |
1981年 | 119篇 |
1980年 | 90篇 |
1979年 | 92篇 |
1978年 | 91篇 |
1977年 | 81篇 |
1976年 | 84篇 |
1975年 | 53篇 |
1974年 | 73篇 |
1973年 | 67篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Frederic Barras Jean Pierre Chambost Marc Chippaux 《Molecular & general genetics : MGG》1984,197(3):486-490
Summary The study of mutants of Erwinia specifically unable to ferment cellobiose indicates that the mutations are clustered between arg and ile on the chromosome of this organism. In vivo cloning of the genes responsible for cellobiose utilization lead to a plasmid, pBEC2, which complements all Erwinia Clb- specific mutants. When introduced into wild-type E. coli it allows this organism to use cellobiose, arbutin and salicin; it also complements bglB and bglC mutants of Escherichia coli indicating that arbutin and salicin utilization is due to the products of the pBEC2 cloned genes. From the characterization of mutants pleiotropically affected in the utilization of various carbon sources, including cellobiose, arbutin and salicin, it is proposed that the three--glucosides are substrates of the phosphoenolpyruvate-dependent phosphotransferase system (PTS). 相似文献
22.
Chardonnet Yvette Viac Jacqueline Levai Jacques Begoud Gérard Morgon Alain Thivolet Jean 《Virchows Archiv. B, Cell pathology including molecular pathology》1986,51(1):421-428
Virchows Archiv B Cell Pathology - Various parameters of the local cellular response have been studied in 16 laryngeal papillomas from ten patients with recurrent papillomas as well as normal... 相似文献
23.
24.
Differential Tolerance of Streptomycetes to Sodium Chloride as a Taxonomic Aid 总被引:2,自引:1,他引:1 下载免费PDF全文
A survey was made of the NaCl tolerance of approximately 1,300 Streptomyces strains belonging to 313 species. The growth medium of the organisms was supplemented with a graded series of NaCl concentrations (4, 7, 10, and 13%). Only 1.8% of the species could not tolerate 4% NaCl; 26.9% could grow at a maximum of 4%; 49.7% could tolerate a maximum of 7%; 18.8% could grow at a maximum of 10%; and only 2.8% could tolerate 13% NaCl. In evaluating the relationships of NaCl tolerance to various taxonomic features, higher tolerance was statistically associated with the "yellow" and possibly the "white"-spored streptomycetes, whereas the "red"-spored series tended to have lesser tolerance. Higher tolerance was also indicated for spiny-spored species, as a group, than for smooth-spored forms. Likewise, nonproducers of melanin, collectively, were more NaCl tolerant than melanin-producing species. Uniformity of test responses between strains of species studied suggested the usefulness of NaCl tolerance as a taxonomic criterion. 相似文献
25.
26.
Coxsackie A9 virus was identified by the authors during the fall of 1965 in Montreal in six children with fever and exanthem. Three of the six children were siblings. The exanthem was centrally distributed as described by Lerner et al. and consisted of discrete maculopapules 3 to 4 mm. in diameter. The viral agent was recovered and identified in tissue culture in five cases, while in the sixth Coxsackie type-A lesions were produced in suckling mice. Serological confirmation was obtained in two patients from whom sera were available. In contrast, no exanthem was observed in three older patients with a diagnosis of aseptic meningitis associated with Coxsackie A9 virus. In only one of 16 patients with Coxsackie B virus infection was an exanthem observed during the same period.The true incidence of Coxsackie A9-associated exanthems is difficult to determine because of the benign nature of the disease. 相似文献
27.
28.
29.
Spores of Aspergillus niger obtained by solid state fermentation on buckwheat seeds produced gluconic acid from glucose with a high yield, near 1.06 g gluconic acid/g glucose, close to the stoichiometric value. The reaction itself could be carried out either with purified biocatalyst or with the whole buckwheat medium resulting from spore production process. 200 g gluconic acid/L were obtained in 200 h with sequential feedings of glucose up to 190 g/L. 相似文献
30.