全文获取类型
收费全文 | 3941篇 |
免费 | 234篇 |
国内免费 | 2篇 |
专业分类
4177篇 |
出版年
2021年 | 40篇 |
2020年 | 23篇 |
2019年 | 26篇 |
2018年 | 70篇 |
2017年 | 57篇 |
2016年 | 76篇 |
2015年 | 101篇 |
2014年 | 116篇 |
2013年 | 160篇 |
2012年 | 233篇 |
2011年 | 238篇 |
2010年 | 137篇 |
2009年 | 109篇 |
2008年 | 228篇 |
2007年 | 209篇 |
2006年 | 224篇 |
2005年 | 184篇 |
2004年 | 177篇 |
2003年 | 179篇 |
2002年 | 163篇 |
2001年 | 84篇 |
2000年 | 88篇 |
1999年 | 67篇 |
1998年 | 39篇 |
1997年 | 24篇 |
1996年 | 23篇 |
1995年 | 28篇 |
1994年 | 28篇 |
1993年 | 33篇 |
1992年 | 32篇 |
1991年 | 24篇 |
1990年 | 25篇 |
1988年 | 26篇 |
1987年 | 26篇 |
1986年 | 25篇 |
1985年 | 30篇 |
1984年 | 40篇 |
1983年 | 38篇 |
1982年 | 39篇 |
1981年 | 31篇 |
1980年 | 33篇 |
1979年 | 21篇 |
1978年 | 29篇 |
1977年 | 24篇 |
1976年 | 30篇 |
1975年 | 20篇 |
1974年 | 41篇 |
1973年 | 22篇 |
1972年 | 24篇 |
1968年 | 21篇 |
排序方式: 共有4177条查询结果,搜索用时 15 毫秒
1.
Conventional therapies for prostate cancer, especially in its androgen-independent form, may result in the survival of small populations of resistant cells with tumor-initiating potential. These “cancer stem cells” are believed to be responsible for cancer relapse, and therapeutic strategies targeting these cells are of great importance. Telomerase is a ribonucleoprotein enzyme responsible for telomere elongation and is activated in the majority of malignancies, including prostate cancer, but is absent in most normal cells. Putative tumor-initiating cells have significant levels of telomerase, indicating that they are an excellent target for telomerase inhibition therapy. In this review, we present some evidence for the hypothesis that conventional therapies (standard chemotherapy and/or radiation therapy) in combination with telomerase inhibitors may result in effective and more durable responses. 相似文献
2.
3.
4.
The production of L-lysine fromDL-α-amino-ε-caprolactam (DL-ACL) by new strains producingL-α-amino-ε-caprolactamase and aminocaprolactam racemase is described. Optimal conditions for hydrolysis ofL-ACL byCryptococcus sp. and for racemization of ACL by cells of a strain isolated in nature and identified asPseudomonas sp. were determined. Synthesis ofL-α-amino-ε-caprolactamase is induced byDL-ACL orL-lysine with the same effectivity. A positive effect of phosphates (potassium salts) on reduction of the induction lag was
detected, the synthesis of this enzyme was found to be repressed by glucose and some possibilities of the reversion of this
repressive effect were demonstrated. Under conditions optimal for the production of both enzymes a quantitative theoretical
conversion of 10 % aqueousDL-ACL toL-lysine by a mixture of native cells in a mass ratio of 1: 2 (producer of ACL-hydrolase to producer of ACL-racemase) occurred
in 8 h at 40 °C and pH 8.0 相似文献
5.
Legionella pneumophila in Cooling Towers: Fluctuations in Counts, Determination of Genetic Variability by Pulsed-Field Gel Electrophoresis (PFGE), and Persistence of PFGE Patterns 下载免费PDF全文
Sonia Ragull Marian Garcia-Nuez Maria Luisa Pedro-Botet Nieves Sopena Maria Esteve Rafael Montenegro Miquel Sabri 《Applied microbiology》2007,73(16):5382-5384
The concentrations of Legionella pneumophila in cooling towers may vary considerably over short periods of time, producing significant fluctuations throughout the year. Despite genetic variability, in small geographical areas the same indistinguishable pulsed-field gel electrophoresis patterns may be shared among different cooling towers and persist over time. 相似文献
6.
7.
8.
9.
10.
An HTY medium osmotically stabilized with 0.5 M D-glucitol was used for regeneration ofBacillus subtilis protoplasts. The application of glucitol as osmotic stabilizer allows simultaneous selection of cells resistant to kanamycin
to be made since this antibiotic is not inactivated by glucitol when added to the regeneration medium. 相似文献