全文获取类型
收费全文 | 4091篇 |
免费 | 304篇 |
国内免费 | 1篇 |
出版年
2024年 | 3篇 |
2023年 | 10篇 |
2022年 | 46篇 |
2021年 | 93篇 |
2020年 | 68篇 |
2019年 | 94篇 |
2018年 | 123篇 |
2017年 | 114篇 |
2016年 | 165篇 |
2015年 | 315篇 |
2014年 | 298篇 |
2013年 | 344篇 |
2012年 | 405篇 |
2011年 | 328篇 |
2010年 | 269篇 |
2009年 | 181篇 |
2008年 | 246篇 |
2007年 | 229篇 |
2006年 | 223篇 |
2005年 | 206篇 |
2004年 | 176篇 |
2003年 | 138篇 |
2002年 | 129篇 |
2001年 | 18篇 |
2000年 | 22篇 |
1999年 | 19篇 |
1998年 | 24篇 |
1997年 | 14篇 |
1996年 | 12篇 |
1995年 | 12篇 |
1994年 | 9篇 |
1993年 | 7篇 |
1992年 | 9篇 |
1991年 | 9篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1980年 | 1篇 |
1979年 | 4篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1970年 | 3篇 |
1962年 | 1篇 |
排序方式: 共有4396条查询结果,搜索用时 921 毫秒
171.
172.
This study was conducted to investigate how different levels of illumination below 1,000 lx would affect the autonomic and behavioral temperature regulation of humans. Seven healthy college-aged women (20+/-0 years) volunteered to participate in this study. They were exposed to a temperature of 26 degrees C in 320 lx for 30 min ('Equilibrium') followed by 700 lx or 70 lx for 30 min (stage 1). After stage 1, they were exposed to 20 degrees C for 30 min in the same illumination as in stage 1 (stage 2). In stage 2 the subjects were instructed to select and wear the clothing they needed for their thermal comfort. The data obtained were analyzed by paired t-test and repeated measures of analysis of variance. Forearm skin blood flow tended to remain steady in 700 lx but decreased markedly in 70 lx in stage 1. There were no significant differences between subjective thermal responses of the subjects experiencing 700 lx or 70 lx in both stages although the subjects felt cooler in stage 2 than in stage 1. The subjects were likely to prefer wearing heavier clothing in 70 lx than in 700 lx. It was concluded that vasoconstriction in the upper limbs occurred more strongly in dim light, which might result in different clothing preferences in a cool environment from those associated with brighter light intensity. 相似文献
173.
Netting operation to control neurofibroma of the face 总被引:3,自引:0,他引:3
When neurofibroma involves the face, it can lead to a most disfiguring, destructive, and debilitating condition. Because of the unique aesthetic and functional properties of the face, the surgeon might hesitate to remove all of the involved soft tissues and facial nerves in a radical procedure. Involvement of the craniofacial skeleton makes the treatment more difficult and complex. The treatment usually consists of excising the symptomatic lesion, and often these lesions are incompletely corrected. Regrowth after partial excision is frequent and leads to recurrence of deformity. The force of gravity plays a major role in the appearance of deformity, leading to facial tissue drooping and bulging as the mass grows and gains weight. The aim of this operation was to contain the residual mass after excision within a tight net against the force of gravity, thus limiting and preventing drooping or bulging of the facial soft tissue while preserving muscles and nerves associated with facial expression. Polytetrafluoroethylene (Teflon) mesh, used as a net, was evaluated as a replacement material for subcutaneous tissue and a substitute for superficial fascia destroyed by tumor infiltration. The mesh was suspended in the superior-posterior direction, capturing the residual mass like a net capturing fish. From 1989 to 1999, a total of eight patients underwent the netting procedure after partial excision of neurofibroma of the face. The follow-up period was 3 to 10 years. The use of Teflon mesh proved to be compatible with the surrounding tissue, endurable at follow-up, and consistent with expectations. Follow-up computed tomographic scans revealed no further visible tumor growth, and the area was contained under the mesh net with satisfactory postoperative facial contour. The advantages of this procedure are the avoidance of radical excision of facial soft tissue, preservation of remnant facial expression, and prevention of progression of facial dysmorphism. 相似文献
174.
Shin SH Shin DH Ryu PY Chung SS Rhee JH 《FEMS immunology and medical microbiology》2002,33(2):133-138
Vibrio vulnificus causes a fulminant and frequently fatal septicemia in susceptible hosts. The present study was designed to evaluate the proinflammatory cytokine profile in V. vulnificus septicemia patients' sera and the effect of doxycycline therapy on the levels of proinflammatory cytokines. Levels of proinflammatory cytokines, tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta and IL-6, were measured in the sera of V. vulnificus septicemic patients and normal healthy volunteers using colorimetric sandwich ELISA. The mean values of TNF-alpha, IL-1beta and IL-6 in the sera of V. vulnificus patients (n=33) increased by 210-, 232- and 40-fold in comparison with those of normal healthy volunteers (n=5), but only the IL-6 level showed a statistically significant difference (P<0.05) between the two groups. Sera from the cases for which doxycycline treatment histories were obvious were designated 'before-treatment' (TX). All the others were included in the after-TX group. In the before-TX group (n=5), the levels of TNF-alpha and IL-1beta significantly increased (P<0.05) in comparison with the after-TX group (n=5). IL-6 levels in the two groups showed no difference. In conclusion, the levels of the well known proinflammatory cytokines TNF-alpha, IL-1beta and IL-6 increased in the V. vulnificus septicemic patients' sera, and the levels of TNF-alpha and IL-1beta decreased significantly after doxycycline treatment. These data indicate that proinflammatory cytokines might play a critical role in V. vulnificus septicemia like in other endotoxemic shocks. The use of doxycycline as an effective bactericidal agent and as an effective modulator of proinflammatory cytokines is supported. 相似文献
175.
A new disposable amperometric bi-enzyme sensor system for detecting phenols has been developed. The phenol sensor developed uses horseradish peroxidase modified screen-printed carbon electrodes (HRP-SPCEs) coupled with immobilized tyrosinase prepared using poly(carbamoylsulfonate) (PCS) hydrogels or a poly(vinyl alcohol) bearing styrylpyridinium groups (PVA-SbQ) matrix. Optimization of the experimental parameters has been performed with regard to buffer composition, pH, operating potential and storage stability. A co-operative reaction involving tyrosinase and HRP occurs at a potential of -50 mV versus Ag/AgCl without the requirement for addition of extraneous H(2)O(2), thus, resulting in a very simple and efficient system. Comparison of the electrode responses with the 4-aminoantipyrine standard method for phenol sample analysis indicated the feasibility of the disposable sensor system for sensitive "in-field" determination of phenols. The most sensitive system was the tyrosinase immobilized HRP-SPCE using PCS, which displayed detection limits for phenolic compounds in the lower nanomolar range e.g. 2.5 nM phenol, 10 nM catechol and 5 nM p-cresol. 相似文献
176.
Yang JM Bell J Huang Y Tirado M Thomas D Forster AH Haigis RW Swanson PD Wallace RB Martinsons B Krihak M 《Biosensors & bioelectronics》2002,17(6-7):605-618
An integrated, stacked microlaboratory for performing automated electric-field-driven immunoassays and DNA hybridization assays was developed. The stacked microlaboratory was fabricated by orderly laminating several different functional layers (all 76 x 76 mm(2)) including a patterned polyimide layer with a flip-chip bonded CMOS chip, a pressure sensitive acrylic adhesive (PSA) layer with a fluidic cutout, an optically transparent polymethyl methacrylate (PMMA) film, a PSA layer with a via, a patterned polyimide layer with a flip-chip bonded silicon chip, a PSA layer with a fluidic cutout, and a glass cover plate layer. Versatility of the stacked microlaboratory was demonstrated by various automated assays. Escherichia coli bacteria and Alexa-labeled protein toxin staphylococcal enterotoxin B (SEB) were detected by electric-field-driven immunoassays on a single chip with a specific-to-nonspecific signal ratios of 4.2:1 and 3.0:1, respectively. Furthermore, by integrating the microlaboratory with a module for strand displacement amplification (SDA), the identification of the Shiga-like toxin gene (SLT1) from E. coli was accomplished within 2.5 h starting from a dielectrophoretic concentration of intact E. coli bacteria and finishing with an electric-field-driven DNA hybridization assay, detected by fluorescently labeled DNA reporter probes. The integrated microlaboratory can be potentially used in a wide range of applications including detection of bacteria and biowarfare agents, and genetic identification. 相似文献
177.
Here we describe a proteomic approach to detect fibrinolytic enzymes from the culture supernatant of Bacillus subtilis 168. Following isoelectric focusing without dithiothreitol, two gels, one for sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and the other for zymography, were run in parallel. After silver staining of SDS-PAGE and activity staining of zymography gel, the two gels were superimposed to detect protein spots that coincided with clear zones on the zymography gel. We identified four protein spots and characterized them with matrix-assisted laser desorption/ionization mass spectrometry. Database search revealed that four spots contained at least one of the extracellular serine proteases such as WprA and Vpr. This combined method of two-dimensional gel and zymography can be used as a powerful tool to detect proteases from various organisms. 相似文献
178.
Retrotransposons are present in multi-copy numbers that are integrated into plant genomes with considerable heterogeneous sequences within a single plant and between plant species, which allows the use of retrotransposons as additional sources of DNA polymorphism. A primer design for the sequence-tagged specific site and cleaved amplified polymorphic sequences (STS-CAPs) that are derived from retrotransposon-like sequences was developed for the molecular marker analysis in Hibiscus syriacus. This method was applied for the detection of sequence variations of intact retrotransposons that exist in plant genomes, which resulted in higher polymorphisms than in the amplified fragment length polymorphism (AFLP). Through STS-CAPs, specific fingerprinting data among H. syriacus varieties can be easily distinguished and generated with reproducible results. It could also be adapted to any species that possess multi-copy retrotransposons for varietal identification as well as the assessment of genetic relationships. 相似文献
179.
180.
Regulation of septation and cytokinesis during resumption of cell division requires uvi31+, a UV-inducible gene of fission yeast 总被引:1,自引:0,他引:1
uvi31+ is a sequence homolog of Escherichia coli bolA gene in Schizosaccharomyces pombe, identified as a UV-inducible gene. Here, the cellular function of uvi31+ was investigated by null mutant analysis. Deletion of uvi31+ led to a delayed germination of spore and defects in subsequent cell division. However, the uvi31 mutant cell proliferated faster with smaller cell size than the wild-type cell during vegetative growth. In addition, the uvi31 mutant was sensitive to UV-light. It showed a normal cell cycle delay after UV-irradiation but displayed aberrant septum formation and defective cytokinesis when released from the UV damage checkpoint. These results suggest that uvi31+ may be involved in control of cell division, especially during the resumption from cell cycle arrest. 相似文献