全文获取类型
收费全文 | 222篇 |
免费 | 13篇 |
出版年
2022年 | 2篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2016年 | 10篇 |
2015年 | 8篇 |
2014年 | 11篇 |
2013年 | 22篇 |
2012年 | 12篇 |
2011年 | 7篇 |
2010年 | 12篇 |
2009年 | 17篇 |
2008年 | 9篇 |
2007年 | 8篇 |
2006年 | 6篇 |
2005年 | 10篇 |
2004年 | 5篇 |
2003年 | 5篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1999年 | 4篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1968年 | 2篇 |
1966年 | 1篇 |
排序方式: 共有235条查询结果,搜索用时 15 毫秒
1.
In this contribution we investigate the impact of the forcing waveform on the productivity of a continuous bioreactor governed by an unstructured, nonlinear kinetic model. The (periodic) forcing is applied on the substrate concentration in the feed. To this end, some alternative waveforms commonly encountered in practice are evaluated and their performance is compared. An analytical/numerical approach is used. The preliminary analytical step is based on the π‐criterion that gives useful information for small amplitudes. The extension to larger amplitudes, when significant improvements are expected, is then performed through a continuation‐optimization procedure. It is found that the choice of the specific waveform has an impact on the performance of the process and there is no unique best forcing for any process condition, but its choice depends on the operating parameters and the forcing amplitude and frequency values. Further, the influence of the waveform functions on the wash‐out conditions are extensively examined. The analysis shows that all the waveforms examined in this work may lead to significant enlargement of the nontrivial regime with respect to a steady state operation. In particular, square‐wave forcing leads in practice to the extinction of the wash‐out conditions for any feed substrate concentration and for a well defined choice of the forcing parameters. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010 相似文献
2.
3.
The alpha-like globin gene cluster in rabbits contains embryonic zeta-
globin genes, an adult alpha-globin gene, and theta-globin genes of
undetermined function. The basic arrangement of genes, deduced from
analysis of cloned DNA fragments, is 5'-zeta 0-zeta 1-alpha 1-theta 1- zeta
2-zeta 3-theta 2-3'. However, the pattern of restriction fragments
containing zeta- and theta-globin genes varies among individual rabbits.
Analysis of BamHI fragments of genomic DNA from 24 New Zealand white
rabbits revealed eight different patterns of fragments containing
zeta-globin genes. The large BamHI fragments containing genes zeta 0 and
zeta 1 are polymorphic in length, whereas a 1.9-kb fragment containing the
zeta 2 gene and the 3.5-kb fragment containing the zeta 3 gene do not vary
in size. In contrast to this constancy in the size of the restriction
fragments, the copy number of the zeta 2 and zeta 3 genes does vary among
different rabbits. No length polymorphism was detected in the BamHI
fragments containing the theta-globin genes, but again the copy number
varies for restriction fragments containing the theta 2 gene. The alpha 1-
and theta 1-globin genes are located in a nonpolymorphic 7.2-kb BamHI
fragment. The combined data from hybridization with both zeta and theta
probes shows that the BamHI cleavage pattern does not vary within the
region 5'-alpha 1-theta 1- zeta 2-zeta 3-theta 2-3', but the pattern
genomic blot-hybridization patterns for the progeny of parental rabbits
with different zeta-globin gene patterns shows that the polymorphic
patterns are inherited in a Mendelian fashion. Two different haplotypes
have been mapped based on the genomic blot-hybridization data. The
variation in the alpha-like globin gene cluster in the rabbit population
results both from differences in the copy number of the duplication block
containing the zeta-zeta-theta gene set and from the presence or absence of
polymorphic BamHI sites.
相似文献
4.
Trimethyloxonium modification of single batrachotoxin-activated sodium channels in planar bilayers. Changes in unit conductance and in block by saxitoxin and calcium 总被引:13,自引:9,他引:4 下载免费PDF全文
Single batrachotoxin-activated sodium channels from rat brain were modified by trimethyloxonium (TMO) after incorporation in planar lipid bilayers. TMO modification eliminated saxitoxin (STX) sensitivity, reduced the single channel conductance by 37%, and reduced calcium block of inward sodium currents. These effects always occurred concomitantly, in an all-or-none fashion. Calcium and STX protected sodium channels from TMO modification with potencies similar to their affinities for block. Calcium inhibited STX binding to rat brain membrane vesicles and relieved toxin block of channels in bilayers, apparently by competing with STX for the toxin binding site. These results suggest that toxins, permeant cations, and blocking cations can interact with a common site on the sodium channel near the extracellular surface. It is likely that permeant cations transiently bind to this superficial site, as the first of several steps in passing inward through the channel. 相似文献
5.
Modulation of c-myc expression in the HL-60 cell line 总被引:7,自引:0,他引:7
A decrease in the expression of the myc proto-oncogene of HL-60 cells has been reported as an accompaniment of myeloid differentiation induced by either dimethylsulfoxide or retinoic acid. We report herein that several inhibitors of poly(ADP-ribose)-polymerase induced myeloid differentiation in HL-60 cultures. Studies on the expression of the c-myc gene in total cell RNA populations indicate that expression of this gene is inversely correlated with the state of differentiation, either myeloid or monocytic, of the cultured cells independent of the inducer and the rate of cell proliferation. 相似文献
6.
R Testi F M Pulcinelli M G Cifone D Botti E Del Grosso S Riondino L Frati P P Gazzaniga A Santoni 《Journal of immunology (Baltimore, Md. : 1950)》1992,148(9):2867-2871
CD69 is a signal transducing disulfide-linked homodimer functionally expressed on platelets, CD3bright thymocytes, and activated lymphocytes. In an attempt to investigate early molecular events in CD69-mediated cell activation we studied the relative contribution of phospholipase A2 (PLA2) and phosphatidylinositol-specific phospholipase C-dependent pathways during platelet activation induced by CD69 stimulation. Thromboxane A2 (TXA2) synthetase inhibitor and TXA2R inhibitor R68070 were able to inhibit platelet aggregation induced by CD69 stimulation, indicating that TXA2 was the main mediator of the response. CD69-induced arachidonic acid release and TXA2 production were essentially PLA2 dependent because they could be blocked by the PLA2 inhibitor quinacrine. Inositol 1,3,4-trisphosphate generation was clearly detectable after CD69 cross-linking, but it was completely abrogated by quinacrine and R68070 and therefore secondary to TXA2 release and TXA2R engagement. Finally, direct measurement of enzymatic activity in vitro using radiolabeled phospholipid vesicles showed that CD69 cross-linking resulted in PLA2-dependent arachidonic acid and lysophosphatidylcholine generation from phosphatidylcholine, which was sensitive to quinacrine but not to R68070. By contrast, CD69-induced 1,2-diacylglycerol release from phosphatidylinositol 4,5-bisphosphate was blocked by both inhibitors. These results indicate a preferential involvement of PLA2 in CD69-dependent signal transduction in platelets and provide evidence for the unique role of PLA2-mediated activation pathways in transmembrane receptor signaling. 相似文献
7.
8.
Abstract Opportunistic sightings and strandings of Caperea marginata (n=196) from the vicinity of Australia and New Zealand (1884 to early 2007) were used to relate geographic and temporal patterns to oceanographic and broad-scale climatic variability. Records were not uniformly distributed along the coast and more (69%) were from Australia than New Zealand. Seven coastal whale ‘hotspots’ were identified which accounted for 61% of records with locality data. Half of the hotspot records were from southeast (37) and northwest (20) Tasmania—others each had 9–15 events. Upwelling and/or high zooplankton abundance has been documented near all whale hotspots. Records of C. marginata occurred in all months, with 75% in spring and summer. Inter-annual variability showed broad agreement between increased whale records (usually in spring/summer) and strongly positive ‘Niño 3.4’ during 1980–1995 but not thereafter. Coastal upwelling and productivity increase during climatic phenomena such as El Niño and are likely to be quickly beneficial to plankton-feeding whales such as C. marginata. 相似文献
9.
Bernardetta?AddisEmail author Giuliana?Carello Andrea?Grosso Elena?Tànfani 《Flexible Services and Manufacturing Journal》2016,28(1-2):206-232
In this work we consider the problem of selecting a set of patients among a given waiting list of elective patients and assigning them to a set of available operating room blocks. We assume a block scheduling strategy in which the number and the length of available blocks are given. As each block is related to a specific day, by assigning a patient to a block his/her surgery date is fixed, as well. Each patient is characterized by a recommended maximum waiting time and an uncertain surgery duration. In practical applications, new patients enter the waiting list continuously. Patient selection and assignment is performed by surgery departments on a short-term, usually a week, regular base. We propose a so-called rolling horizon approach for the patient selection and assignment. At each iteration short-term patient assignment is decided. However, in a look-ahead perspective, a longer planning horizon is considered when looking for the patient selection. The mid-term assignment over the next \(n\) weeks is generated by solving an ILP problem, minimizing a penalty function based on total waiting time and tardiness of patients. The approach is iteratively applied by shifting ahead the mid-term planning horizon. When applying the first week solution, unpredictable extensions of surgeries may disrupt the schedule. Such disruptions are recovered in the next iteration: the mid-term solution is rescheduled limiting the number of variations from the previously computed plan. Besides, the approach allows to deal with new patient arrivals. To keep limited the number of disruptions due to uncertain surgery duration, we propose also a robust formulation of the ILP problem. The deterministic and the robust formulation based frameworks are compared over a set of instances, including different stochastic realization of surgery times. 相似文献
10.
Cluster Computing - There are many organizations interested in sharing data with others, and they can do this only if a multi-domain secure platform is available. Such platforms, often referred to... 相似文献