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1.
Hexavalent chromium reduction by an actinomycete, Arthrobacter crystallopoietes ES 32 总被引:1,自引:0,他引:1
Environmental contamination by hexavalent chromium, Cr(VI), presents a serious public health problem. This study assessed
the reduction of Cr(VI) by intact cells and a cell-free extract (CFE) of an actinomycete, Arthrobacter crystallopoietes (strain ES 32), isolated from soil contaminated with dichromate. Both intact cells and CFE of A. crystallopoietes, displayed substantial reduction of Cr(VI). Intact cells reduced about 90% of the Cr(VI) added within 12 h and Cr(VI) was
almost completely reduced after 24 h. The K
M
and V
max of Cr(VI) bioreduction by intact cells were 2.61 μM and 0.0142 μmol/min/mg protein, respectively. Cell-free chromate reductase of the A. crystallopoietes (ES 32) reduced hexavalent chromium at a K
M
of 1.78 μM and a V
max of 0.096 μmol/min/mg protein. The rate constant (k) of chromate reduction was inversely related to Cr(VI) concentration and the half-life (t
1/2) of Cr(VI) reduction increased with increasing concentration. A. crystallopoietes produced a periplasmic chromate reductase that was stimulated by NADH. Results indicate that A. crystallopoietes ES 32 can be used to detoxify Cr(VI) in polluted sites, particularly in stressed environments. 相似文献
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Vicente Gomes Phan Van Ngan Claude de Broyer Maria José deA. C. Rocha Passos 《Hydrobiologia》1993,262(2):109-113
Mitotic and meiotic chromosomes of the Antarctic lysianassoid amphipod Waldeckia obesa are described. The modal chromosome number is n = 25 and 2n = 50. The potential applications of cytogenetical studies in this group are discussed. 相似文献
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Canilha L Santos VT Rocha GJ Almeida e Silva JB Giulietti M Silva SS Felipe MG Ferraz A Milagres AM Carvalho W 《Journal of industrial microbiology & biotechnology》2011,38(9):1467-1475
Experiments based on a 23 central composite full factorial design were carried out in 200-ml stainless-steel containers to study the pretreatment,
with dilute sulfuric acid, of a sugarcane bagasse sample obtained from a local sugar–alcohol mill. The independent variables
selected for study were temperature, varied from 112.5°C to 157.5°C, residence time, varied from 5.0 to 35.0 min, and sulfuric
acid concentration, varied from 0.0% to 3.0% (w/v). Bagasse loading of 15% (w/w) was used in all experiments. Statistical
analysis of the experimental results showed that all three independent variables significantly influenced the response variables,
namely the bagasse solubilization, efficiency of xylose recovery in the hemicellulosic hydrolysate, efficiency of cellulose
enzymatic saccharification, and percentages of cellulose, hemicellulose, and lignin in the pretreated solids. Temperature
was the factor that influenced the response variables the most, followed by acid concentration and residence time, in that
order. Although harsher pretreatment conditions promoted almost complete removal of the hemicellulosic fraction, the amount
of xylose recovered in the hemicellulosic hydrolysate did not exceed 61.8% of the maximum theoretical value. Cellulose enzymatic
saccharification was favored by more efficient removal of hemicellulose during the pretreatment. However, detoxification of
the hemicellulosic hydrolysate was necessary for better bioconversion of the sugars to ethanol. 相似文献
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Nathalia Torres Dutra Vanildo Silveira Inga Gonçalves de Azevedo Lupis Ribeiro Gomes‐Neto Arnoldo Rocha Façanha Neusa Steiner Miguel Pedro Guerra Eny Iochevet Segal Floh Claudete Santa‐Catarina 《Physiologia plantarum》2013,148(1):121-132
Polyamines (PAs) are abundant polycationic compounds involved in many physiological processes in plants, including somatic embryogenesis. This study investigates the role of PAs on cellular growth and structure of pro‐embryogenic masses (PEMs), endogenous PA and proton pump activities in embryogenic suspension cultures of Araucaria angustifolia. The embryogenic suspension cultures were incubated with putrescine (Put), spermidine (Spd), spermine (Spm) and the inhibitor methylglyoxal‐bis(guanylhydrazone) (MGBG), respectively (1 mM). After 24 h and 21 days, the cellular growth and structure of PEMs, endogenous PA contents and proton pump activities were analyzed. The addition of Spm reduced the cellular growth and promoted the development of PEMs in embryogenic cultures, which could be associated with a reduction in the activities of proton pumps, such as H+‐ATPase P‐ and V‐types and H+‐PPases, and alterations in the endogenous PA contents. Spm significantly affected the physiology of the A. angustifolia somatic embryogenesis suspension, as it potentially affects cellular growth and structure of PEMs through the modulation of proton pump activities. This work demonstrates the involvement of exogenous PAs in the modulation of cellular growth and structure of PEMs, endogenous PA levels and proton pump activities during somatic embryogenesis. To our knowledge, this study is the first to report a relationship between PAs and proton pump activities in these processes. The results obtained in this study offer new perspectives for studies addressing the role of PAs and proton pump on somatic embryogenesis in this species. 相似文献