全文获取类型
收费全文 | 1476篇 |
免费 | 92篇 |
国内免费 | 52篇 |
专业分类
1620篇 |
出版年
2024年 | 6篇 |
2023年 | 21篇 |
2022年 | 41篇 |
2021年 | 42篇 |
2020年 | 41篇 |
2019年 | 46篇 |
2018年 | 37篇 |
2017年 | 34篇 |
2016年 | 39篇 |
2015年 | 38篇 |
2014年 | 72篇 |
2013年 | 86篇 |
2012年 | 44篇 |
2011年 | 65篇 |
2010年 | 53篇 |
2009年 | 52篇 |
2008年 | 67篇 |
2007年 | 57篇 |
2006年 | 61篇 |
2005年 | 50篇 |
2004年 | 58篇 |
2003年 | 55篇 |
2002年 | 30篇 |
2001年 | 24篇 |
2000年 | 27篇 |
1999年 | 39篇 |
1998年 | 33篇 |
1997年 | 32篇 |
1996年 | 27篇 |
1995年 | 28篇 |
1994年 | 33篇 |
1993年 | 23篇 |
1992年 | 26篇 |
1991年 | 26篇 |
1990年 | 21篇 |
1989年 | 23篇 |
1988年 | 17篇 |
1987年 | 7篇 |
1986年 | 11篇 |
1985年 | 6篇 |
1984年 | 25篇 |
1983年 | 21篇 |
1982年 | 21篇 |
1981年 | 14篇 |
1980年 | 22篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 7篇 |
1973年 | 3篇 |
1972年 | 2篇 |
排序方式: 共有1620条查询结果,搜索用时 15 毫秒
71.
Cees Hol Cees M. Verduin Etienne E.A. Van Dijke Jan Verhoef ré Fleer Hans van Dijk 《FEMS immunology and medical microbiology》1995,11(3):207-211
Abstract The purpose of this study was to investigate complement resistance in Branhamella (Moraxella) catarrhalis isolated from healthy schoolchildren or sputum-producing adult patients. Two techniques were used: a serum bactericidal assay as the gold standard and an easier ‘culture and spot’ test. Children (age 4–13; n = 303) and patients ( n = 1047) showed high colonization/infection rates with B. catarrhalis (31% and 19%, respectively). Complement resistance or intermediate sensitivity occurred frequently in patient isolates (62% and 27%, respectively) and less often in children (33% and 8.5%, respectively; P ⪡ 0.0001). In young children (age 4–5 years), the proportion of complement-resistant strains was around 50%. Complement resistance in B. catarrhalis is associated with illness and may hence be considered a virulence factor. 相似文献
72.
73.
Iron, the prosthetic group of haemoglobin, was found to lower serum glucose levels of diabetic rats. Its regulative mechanism
and effects on enzymatic activities of glucose metabolism are still unknown. In this study, the correlation between iron supply
and enzymatic activities of glucose metabolism and respiratory chain were evaluated in liver and kidney tissues of alloxan
induced-diabetic rats. After FeSO4 and metformin administration, serum samples were collected for serum glucose and fructosamine level measurements. Kidney
and liver tissues were excised at the end of the study for assaying enzymatic activities of isocitrate dehydrogenase, succinate
dehydrogenase, malate dehydrogenase, NADH-dehydrogenase and cytochrome-c-oxidase. Results showed significantly decreased serum glucose and fructosamine levels in treatment groups and enhanced enzymatic
activities of several proteins as compared with the diabetic control group. Therefore, these data suggested that FeSO4 administration could increase the supply of oxygen, enhance enzymatic activities of glucose metabolism and the respiratory
chain, accelerate glucose metabolism and consequently decrease serum glucose levels. 相似文献
74.
75.
Ke-Fei Hu Margaret Chen Izzeldin Abusugra Federica Monaco Bror Morein 《FEMS immunology and medical microbiology》2001,31(2):105-112
The recognition of a pathogen or a vaccine antigen formulation by cells in the innate immune system leads to production of proinflammatory cytokines, which will determine the ensuing acquired immune response quantitatively and qualitatively. Tumour necrosis factor (TNF)-alpha, interleukin (IL)-1 and IL-6 are the first set of cytokines produced upon such an encounter, which have roles both in protective immunity and immunopathogenesis evident with respiratory syncytial virus (RSV). RSV antigens in different physical adjuvant-vaccine formulations were analysed for their capacity to provoke cultured murine peritoneal cells to produce these three proinflammatory cytokines. RSV immunostimulating complex (ISCOM), i.e. both antigen and adjuvant are incorporated in the same particle, induced high levels of IL-1alpha being of the same magnitude or higher than those of live RSV and lipopolysaccharide (LPS). Live virus and LPS induced higher levels of IL-6 and TNF-alpha than ISCOM and so did non-adjuvanted UV-inactivated RSV but only at high doses. ISCOM-Matrix, i.e. ISCOM without antigens, admixed as a separate entity to inactivated RSV, downregulated or blocked the cytokine response to the inactivated RSV in contrast to ISCOM. Kinetic studies showed that ISCOM induced cytokine production first detected at hours 1, 2, 4 for TNF-alpha, IL-6 and IL-1alpha respectively, which was earlier than for the other antigen formulations containing corresponding doses of antigen and/or Quillaja adjuvant. Peak values for production of TNF-alpha and IL-6 were at 8 h and for IL-1alpha at 72 h following stimulation with ISCOM. The delayed appearance of IL-1alpha may reflect the cell-bound nature of this cytokine. 相似文献
76.
Junko Amemura-Maekawa Sakurako Mishima-Abe Fumiaki Kura Tomoko Takahashi Haruo Watanabe 《FEMS microbiology letters》1999,176(2):339-344
A gene katA that encodes a novel catalase-peroxidase was cloned from the chromosome of Legionella pneumophila. The nucleotide sequence revealed that KatA was highly homologous to members of the bacterial bifunctional catalase-peroxidase family. In addition, KatA has a N-terminal signal sequence and was considered to be present in the periplasm of the bacterium. 相似文献
77.
78.
水稻、玉米和狼尾草花粉低温贮藏期间激素和维生素含量及呼吸速率变化 总被引:1,自引:1,他引:1
测定了水稻、玉米和狼尾草花粉在低温(4±1℃)贮藏时内源激素(IAA、GA3、ZT和ABA)、维生素B.维生素C、维生素E、类胡萝卜素含量和呼吸速率的变化,结果表明IAA、GA3、ZT、维生素B2、维生素C、维生素E、类胡萝卜素的含量和呼吸速率在贮藏期间下降,而脱落酸的含量不断上升.与短寿命的水稻和玉米花粉相比,长寿命的狼尾草花粉的IAA和GA3含量及呼吸速率低,下降速度慢,而ABA始终保持较高水平. 相似文献
79.
A direct hydrogen bond between ubiquinone/quinol bound at the QO site and a cluster-ligand histidine of the iron-sulfur protein (ISP) is described as a major determining factor explaining much experimental data on position of the ISP ectodomain, electron paramagnetic resonance (EPR) lineshape and midpoint potential of the iron-sulfur cluster, and the mechanism of the bifurcated electron transfer from ubiquinol to the high and low potential chains of the bc1 complex. 相似文献
80.