全文获取类型
收费全文 | 7896篇 |
免费 | 539篇 |
专业分类
8435篇 |
出版年
2023年 | 85篇 |
2022年 | 65篇 |
2021年 | 145篇 |
2020年 | 116篇 |
2019年 | 118篇 |
2018年 | 354篇 |
2017年 | 283篇 |
2016年 | 344篇 |
2015年 | 286篇 |
2014年 | 348篇 |
2013年 | 584篇 |
2012年 | 640篇 |
2011年 | 672篇 |
2010年 | 420篇 |
2009年 | 276篇 |
2008年 | 246篇 |
2007年 | 211篇 |
2006年 | 248篇 |
2005年 | 114篇 |
2004年 | 145篇 |
2003年 | 116篇 |
2002年 | 86篇 |
2001年 | 102篇 |
2000年 | 106篇 |
1999年 | 116篇 |
1998年 | 85篇 |
1997年 | 78篇 |
1996年 | 77篇 |
1995年 | 87篇 |
1994年 | 71篇 |
1993年 | 65篇 |
1992年 | 80篇 |
1991年 | 70篇 |
1990年 | 56篇 |
1989年 | 73篇 |
1987年 | 66篇 |
1986年 | 58篇 |
1985年 | 75篇 |
1984年 | 61篇 |
1983年 | 66篇 |
1982年 | 59篇 |
1981年 | 69篇 |
1980年 | 57篇 |
1979年 | 80篇 |
1978年 | 57篇 |
1977年 | 62篇 |
1975年 | 52篇 |
1974年 | 59篇 |
1973年 | 52篇 |
1969年 | 56篇 |
排序方式: 共有8435条查询结果,搜索用时 0 毫秒
1.
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
2.
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
3.
Drahomíra Kenov Lucie oltysov Michal Pravenec Marie-Pierre Moisan W. Theodore Kurtz Vladimír Ken 《Journal of Experimental Animal Science》2000,41(1-2)
The SHR-Lx congenic strain carrying a differential segment of chromosome 8 of BN and PD origin was recently shown to exhibit a significant decrease in blood pressure as compared to the SHR strain. There were two positional candidate genes for blood pressure control mapped to the differential segment: the rat kidney epithelial potassium channel gene (Kcnj1) and brain dopamine receptor 2 gene (Drd2). Bot these genes were separated into SHR.BN-RNO8 congenic substrains. In this communication, we are presenting the assignment of two further putative candidate genes, which might be involved in blood pressure control to the BN/PD differential segment of the SHR-Lx congenic strain. These are: the gene coding for smooth muscle cell specific protein 22 (Sm22) defined by the D8Mcw1 marker and neuronal nicotinic acetylcholine receptor gene cluster, defined by the D8Bord1 marker. Moreover, the glutamate receptor gene Grik4 which also maps to the differential segment of the SHR-Lx should be taken into account. The genetic separation of all these putative candidate genes of blood pressure control is being performed by recombinations and subsequent selection using (SHR×SHR-Lx) intercross population. 相似文献
4.
5.
Activation of erythrocyte membrane Ca2+-ATPase by calpain 总被引:1,自引:0,他引:1
K S Au 《Biochimica et biophysica acta》1987,905(2):273-278
Ca2+-ATPase of erythrocyte membranes, prepared from erythrocytes substantially removed of contaminating leukocytes, was found to be activated by calpain isolated from the same source. Saponin or glycodeoxycholate treatment of membranes was essential for elicitation of the calpain response. Unlike the membrane bound ATPase, solubilized ATPase was inactivated by calpain. Digestion of membranes with the protease did not affect the Km (ATP) of Ca2+-ATPase though stimulation of the membrane ATPase by calmodulin could be partially substituted by calpain treatment. As compared with control, Ca2+-ATPase of calpain-digested membranes attained maximal activity at a lower free Ca2+ concentration. 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.
Anatomy and arteriography of cleft lips in stillborn children 总被引:1,自引:0,他引:1
M Fára 《Plastic and reconstructive surgery》1968,42(1):29-36
10.