全文获取类型
收费全文 | 4741篇 |
免费 | 166篇 |
国内免费 | 1篇 |
专业分类
4908篇 |
出版年
2018年 | 101篇 |
2017年 | 94篇 |
2016年 | 102篇 |
2015年 | 116篇 |
2014年 | 132篇 |
2013年 | 182篇 |
2012年 | 223篇 |
2011年 | 218篇 |
2010年 | 169篇 |
2009年 | 117篇 |
2008年 | 179篇 |
2007年 | 155篇 |
2006年 | 179篇 |
2005年 | 253篇 |
2004年 | 213篇 |
2003年 | 189篇 |
2002年 | 115篇 |
2001年 | 102篇 |
2000年 | 93篇 |
1999年 | 69篇 |
1998年 | 37篇 |
1997年 | 30篇 |
1996年 | 37篇 |
1995年 | 43篇 |
1994年 | 40篇 |
1993年 | 41篇 |
1992年 | 40篇 |
1991年 | 46篇 |
1990年 | 38篇 |
1988年 | 42篇 |
1987年 | 36篇 |
1986年 | 40篇 |
1985年 | 45篇 |
1984年 | 61篇 |
1983年 | 59篇 |
1982年 | 51篇 |
1981年 | 52篇 |
1980年 | 46篇 |
1979年 | 73篇 |
1978年 | 50篇 |
1977年 | 37篇 |
1976年 | 44篇 |
1975年 | 50篇 |
1974年 | 64篇 |
1973年 | 46篇 |
1972年 | 50篇 |
1971年 | 30篇 |
1970年 | 36篇 |
1969年 | 47篇 |
1966年 | 34篇 |
排序方式: 共有4908条查询结果,搜索用时 0 毫秒
1.
2.
3.
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
4.
Effect of precursors on biosynthesis of monensins A and B 总被引:1,自引:0,他引:1
Precursors of monensins (acetate, propionate, butyrate, isobutyrate) affect the total production and the relative proportion of monensins A and B. Addition of propionate into the fermentation medium causes a prevalence of monensin B whereas butyrate and isobutyrate stimulate the production of monensin A and suppress the production of monensin B. 相似文献
5.
Collections from high altitudes (3840–5100 m a.s.l.) have added several species to the Pannariaceae of Ecuador: Fuscopannaria praetermissa, Pannaria hookeri, Psoroma paleaceum and Psoroma tenue are new to the Andes, and phytogeographic consequences of these are discussed. The following new taxa are described: Parmeliella corallina P. M. Jørg. & Palice, Parmeliella psoromoides P. M. Jørg. & Palice, Psoroma cinnamomeum ssp. andinum P. M. Jørg. & Palice and Santessoniella macrospora P. M. Jørg. & Palice. They are part of a high‐andean element which is not well known and is indicative of a migration route between the polar regions. In addition, two species with associated cyanobacteria, as the primary or secondary symbiont, are reported for the first time from South America: Thelignya lignyota (Wahlenb.) P. M. Jørg. & Henssen and Pilophorus cereolus (Ach.) Th. Fr, both originating from the Northern Hemisphere. 相似文献
6.
7.
Marie Lipoldová Helena Havelková Jana Badalová Jarmila Vojtíšková Lei Quan Magdaléna Krulová Yahya Sohrabi Alphons P. Stassen Peter Demant 《Cancer immunology, immunotherapy : CII》2010,59(2):203-213
Low infiltration of lymphocytes into cancers is associated with poor prognosis, but the reasons why some patients exhibit
a low and others a high infiltration of tumors are unknown. Previously we mapped four loci (Lynf1–Lynf4) controlling lymphocyte infiltration of mouse lung tumors. These loci do not encode any of the molecules that are involved
in traffic of lymphocytes. Here we report a genetic relationship between these loci and the control of production of IFNγ
in allogeneic mixed lymphocyte cultures (MLC). We found that IFNγ production by lymphocytes of O20/A mice is lower than by
lymphocytes of OcB-9/Dem mice (both H2
pz
) stimulated in MLC by irradiated splenocytes of C57BL/10SnPh (H2
b
) or BALB/cHeA (H2
d
) mice, or by ConA. IFNγ production in MLCs of individual (O20 × OcB-9)F2 mice stimulated by irradiated C57BL/10 splenocytes and genotyped for microsatellite markers revealed four IFNγ-controlling
loci (Cypr4-Cypr7), each of which is closely linked with one of the four Lynf loci and with a cluster of susceptibility genes for different tumors. This suggests that inherited differences in certain
lymphocyte responses may modify their propensity to infiltrate tumors and their capacity to affect tumor growth. 相似文献
8.
9.
10.