全文获取类型
收费全文 | 7786篇 |
免费 | 487篇 |
国内免费 | 1351篇 |
出版年
2024年 | 37篇 |
2023年 | 151篇 |
2022年 | 269篇 |
2021年 | 317篇 |
2020年 | 342篇 |
2019年 | 318篇 |
2018年 | 264篇 |
2017年 | 260篇 |
2016年 | 289篇 |
2015年 | 253篇 |
2014年 | 350篇 |
2013年 | 659篇 |
2012年 | 298篇 |
2011年 | 370篇 |
2010年 | 273篇 |
2009年 | 475篇 |
2008年 | 477篇 |
2007年 | 405篇 |
2006年 | 369篇 |
2005年 | 385篇 |
2004年 | 259篇 |
2003年 | 248篇 |
2002年 | 240篇 |
2001年 | 170篇 |
2000年 | 148篇 |
1999年 | 150篇 |
1998年 | 131篇 |
1997年 | 147篇 |
1996年 | 137篇 |
1995年 | 141篇 |
1994年 | 156篇 |
1993年 | 141篇 |
1992年 | 115篇 |
1991年 | 99篇 |
1990年 | 117篇 |
1989年 | 86篇 |
1988年 | 58篇 |
1987年 | 48篇 |
1986年 | 68篇 |
1985年 | 82篇 |
1984年 | 80篇 |
1983年 | 38篇 |
1982年 | 38篇 |
1981年 | 28篇 |
1980年 | 24篇 |
1979年 | 29篇 |
1978年 | 20篇 |
1977年 | 37篇 |
1976年 | 14篇 |
1975年 | 5篇 |
排序方式: 共有9624条查询结果,搜索用时 15 毫秒
961.
Proton transport inside the biofilm limits electrical current generation by anode-respiring bacteria
Anode-respiring bacteria (ARB) in a biofilm anode carry out an oxidation half-reaction of organic matter, producing an electrical current from renewable biomass, including wastes. At the same time, ARB produce protons, usually one proton for every electron. Our study shows how current density generated by an acclimated ARB biofilm was limited by proton transport out of the biofilm. We determined that, at high current densities, protons were mainly transported out of the biofilm by protonating the conjugate base of the buffer system; the maximum current generation was directly related to the transport of the buffer, mainly by diffusion, into and out of the biofilm. With non-limiting acetate concentrations, the current density increased with higher buffer concentrations, going from 2.21 +/- 0.02 A m(-2) with 12.5-mM phosphate buffer medium to 9.3 +/- 0.4 A m(-2) using a 100-mM phosphate buffer at a constant anode potential of E(anode) = -0.35 V versus Ag/AgCl. Increasing the concentration of sodium chloride in the medium (0-100 mM) increased current density by only 15%, indicating that ion migration was not as important as diffusion of phosphate inside the biofilm. The current density also varied strongly with medium pH as a result of the buffer speciation: The current density was 10.0 +/- 0.8 A m(-2) at pH 8, and the pH giving one-half the maximum rate was 6.5. A j-V curve analysis using 100 mM phosphate buffer showed a maximum current density of 11.5 +/- 0.9 A m(-2) and half-saturation potential of -0.414 V versus Ag/AgCl, a value that deviated only slightly from the standard acetate potential, resulting in small anode-potential losses. We discuss the implications of the proton-transport limitation in the field of microbial fuel cells and microbial electrolytic cells. 相似文献
962.
Bioremediation of contaminated soils and aquifers is subject to spatial and temporal temperature changes that can alter the kinetics of key microbial processes. This study quantifies temperature effects on the kinetics of an ethanol-fed sulfate-reducing mixed culture derived from a uranium-contaminated aquifer subject to seasonal temperature fluctuations. The mixed culture contains Desulfovibrio sp. and a Clostridia-like organism. Rates of growth, ethanol utilization, decay, and uranium reduction decreased with decreasing temperature. No significant uranium reduction was observed at 10 degrees C. While both Monod saturation kinetics and pseudo second-order kinetics adequately described the rates of growth and utilization of electron donor (ethanol), model parameters for the pseudo second-order expression had smaller uncertainties. Uranium reduction kinetics were best described by pseudo second-order kinetics modified to include a term for inactivation/death of cells. 相似文献
963.
Park YJ Ko JJ Yun SL Lee EY Kim SJ Kang SW Lee BC Kim SK 《Bioresource technology》2008,99(16):7458-7463
In this study, the potential for the application of the bioaugmentation to Cd and Zn contaminated sediment was investigated. A batch experiment was performed in the lake sediments augmented with Ralstonia sp. HM-1. The degradation capacity of 18.7 mg-DOC/l/day in the treatment group was bigger than that of the blank group (4.4 mg-DOC/l/day). It can be regarded as the result of the reduction of the metal concentration in the liquid phase due to adsorption into the sediments, with the increased alkalinity resulting from the reduction of sulfate by sulfate reducing bacteria (SRB). The removal efficiency of cadmium and zinc in the treatment group was both 99.7% after 35 days. Restrain of elution to water phase from sediment in the Ralstonia sp. HM-1 added treatment group was also shown. In particular, the observed reduction of the exchangeable fraction and an increase in the bound to organics or sulfide fraction in the treatment group indicate its role in the prevention of metal elution from the sediment. Therefore, for bioremediation and restrain of elution from the sediment polluted by metal, Ralstonia sp. augmentation with indigenous microorganism including SRB, sediment stabilization and restrain of elution to surface water is recommended. 相似文献
964.
965.
烟草内生细菌防治烟草黑胫病及促生作用研究 总被引:12,自引:0,他引:12
筛选烟草内生细菌防治烟草黑胫病,获得了对烟草黑胫病有很好防效的内生细菌118、57和93等菌株.在温室控病实验中它们的防效分别可达69.23%、61.53%和65.38%.118菌株对烟草疫霉(Phytophthora parasitica var.nicotianae)菌丝生长有明显的拮抗作用.118菌株具有较广的抗菌谱,且对烟草有促生效果,烟草的鲜重增产率为13.10%. 相似文献
966.
967.
磁选育浸矿菌种新方法的研究——磁泳分离菌种 总被引:4,自引:1,他引:3
世界无处不有磁,磁场对整个世界产生着重大的影响。本文通过大量镜检工作,观察到从酸性矿坑水中初步分离培养得到的部分细菌对外加磁场均有微弱的趋磁性。基于菌种的这种特性,设计了磁泳装置用不同的磁场梯度分离细菌,磁泳分离的方法可以初步分离出近磁、远磁茼,这两个菌群的生理特性有着很大的差异,主要体现在其对亚铁氧化和对金属高于的浸出上,远磁菌亚铁氧化活性比近磁菌高将近50%,远磁菌对铜离子的浸出效果也比近磁茼好。近磁菌在强磁性矿物培养基中生长情况较好,而远磁茼在弱磁性矿物培养基中生长情况较好。而且,在近磁茼的纯培养茼体中分离到磁性颗粒。实验结果证明。采用磁泳用于分离体内舍有磁性颗粒的细菌是可行并且有效的,这一分离技术和工艺的结合也将大大促进我国生物冶金的步伐。 相似文献
968.
磁选育浸矿菌种新方法的研究--磁泳分离菌种 总被引:3,自引:3,他引:0
世界无处不有磁,磁场对整个世界产生着重大的影响。本文通过大量镜检工作,观察到从酸性矿坑水中初步分离培养得到的部分细菌对外加磁场均有微弱的趋磁性。基于菌种的这种特性,设计了磁泳装置用不同的磁场梯度分离细菌,磁泳分离的方法可以初步分离出近磁、远磁菌,这两个菌群的生理特性有着很大的差异,主要体现在其对亚铁氧化和对金属离子的浸出上,远磁菌亚铁氧化活性比近磁菌高将近50%,远磁菌对铜离子的浸出效果也比近磁菌好。近磁菌在强磁性矿物培养基中生长情况较好,而远磁菌在弱磁性矿物培养基中生长情况较好。而且,在近磁菌的纯培养菌体中分离到磁性颗粒。实验结果证明,采用磁泳用于分离体内含有磁性颗粒的细菌是可行并且有效的,这一分离技术和工艺的结合也将大大促进我国生物冶金的步伐。 相似文献
969.
M. A. Amoozegar J. Hamedi M. Dadashipour S. Shariatpanahi 《World journal of microbiology & biotechnology》2005,21(6-7):1237-1243
Summary Ten moderately halophilic spore-forming bacilli were isolated from saline soils in Iran and their intrinsic high-level resistance
to chromate, arsenate, tellurite, selenite, selenate and biselenite was identified by an agar dilution method. Minimum inhibitory
concentration (MIC) for each oxyanion was determined. All isolates were resistant to higher concentrations of arsenate. The
resistance level of the isolates to selenooxyanions was between 10 and 40 mM. Maximum and minimum tolerance against oxyanions
was seen in selenite and biselenite, respectively. Although toxic metal resistance in the isolates was not different from
non-halophilic bacteria that has been reported, unusual resistance to arsenate (250 mM), sodium chromate (75 mM) and potassium
chromate (70 mM) was observed. The results obtained in this study revealed that all isolates were obviously susceptible to
silver, nickel, zinc and cobalt, while seven isolates were resistant to lead. Susceptibility to copper and cadmium varied
among the isolates. Silver had the maximum toxicity, whereas lead and copper showed minimum toxicity. The impact of salinity
on the toxicity of oxyanions was also studied. Our results showed that in general an increase in salinity from 5% (w/v) to
15% (w/v) enhanced tolerance to toxic oxyanions. 相似文献
970.