全文获取类型
收费全文 | 2431篇 |
免费 | 212篇 |
国内免费 | 2篇 |
出版年
2023年 | 12篇 |
2022年 | 27篇 |
2021年 | 63篇 |
2020年 | 27篇 |
2019年 | 30篇 |
2018年 | 51篇 |
2017年 | 35篇 |
2016年 | 76篇 |
2015年 | 126篇 |
2014年 | 111篇 |
2013年 | 144篇 |
2012年 | 203篇 |
2011年 | 185篇 |
2010年 | 125篇 |
2009年 | 94篇 |
2008年 | 140篇 |
2007年 | 149篇 |
2006年 | 145篇 |
2005年 | 117篇 |
2004年 | 116篇 |
2003年 | 104篇 |
2002年 | 89篇 |
2001年 | 44篇 |
2000年 | 33篇 |
1999年 | 31篇 |
1998年 | 25篇 |
1997年 | 15篇 |
1996年 | 12篇 |
1995年 | 12篇 |
1994年 | 21篇 |
1993年 | 14篇 |
1992年 | 17篇 |
1991年 | 19篇 |
1990年 | 18篇 |
1989年 | 13篇 |
1988年 | 15篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 12篇 |
1983年 | 10篇 |
1982年 | 7篇 |
1980年 | 11篇 |
1978年 | 15篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1975年 | 13篇 |
1974年 | 18篇 |
1973年 | 8篇 |
1972年 | 9篇 |
1971年 | 7篇 |
排序方式: 共有2645条查询结果,搜索用时 796 毫秒
101.
102.
103.
104.
A detailed protocol for the synthesis of core/shell semiconductor nanocrystal, their encapsulation into phospholipid micelles, their purification and their coupling to a controlled number of small molecules is given. The protocol for the core/shell quantum dot (QD) CdSe/CdZnS synthesis has been specifically designed with two constraints in mind: green and reproducible core/shell QD synthesis with thick shell structure and QDs that can easily be encapsulated in poly(ethylene glycol)-phospholipid micelles with one QD per micelle. We present two procedures for the QD purification that are suitable for the use of QD micelles for in vivo imaging: ultracentrifugation and size-exclusion chromatography. We also discuss the different coupling chemistry for covalently linking a controlled number of molecules to the QD micelles. The total time durations for the different protocols are as follows: QD synthesis: 6 h; encapsulation: 15 min; purification: 1-4 h; coupling: reaction dependent. 相似文献
105.
Aloys du Bois dAische Mathieu De Craene Xavier Geets Vincent Grgoire Benoit Macq Simon K. Warfield 《Biomedical signal processing and control》2007,2(1):16-24
We present a new non-rigid registration algorithm estimating the displacement field generated by articulated bodies. Indeed the bony structures between different patient images may rigidly move while other tissues may deform in a more complex way. Our algorithm tracks the displacement induced in the column by a movement of the patient between two acquisitions. The volumetric deformation field in the whole body is then inferred from those displacements using a linear elastic biomechanical finite element model. We demonstrate in this paper that this method provides accurate results on 3D sets of computed tomography (CT), MR and positron emission tomography (PET) images and that the results of the registration algorithm show significant decreases in the mean, min and max errors. 相似文献
106.
Provencher V Bégin C Tremblay A Mongeau L Boivin S Lemieux S 《Obesity (Silver Spring, Md.)》2007,15(4):957-966
Objective: To assess the effects of a “Health‐At‐Every‐Size” (HAES) intervention on eating behaviors and appetite ratings in 144 premenopausal overweight women. Research Methods and Procedures: Women were randomly assigned to one of the 3 groups: HAES group, social support (SS) group, and control group (N = 48 in each group). Interventions were conducted over a 4‐month period, and measurements were taken before and after this period. Eating behaviors (cognitive dietary restraint, disinhibition, and susceptibility to hunger) were evaluated by the Three‐Factor Eating Questionnaire. Appetite ratings (desire to eat, hunger, fullness, and prospective food consumption) were assessed by visual analogue scales before and after a standardized breakfast. Results: More important decreases in susceptibility to hunger and external hunger were observed in the HAES group when compared with the SS group (p = 0.05, for susceptibility to hunger) and the control group (p = 0.02 and p = 0.005, for susceptibility to hunger and external hunger, respectively). In addition, women from the HAES group had more important decreases in postprandial area under the curve for desire to eat (p = 0.02) and hunger (p = 0.04) when compared with the control group. The change in the desire to eat noted in the HAES group was also different from the one observed in SS group (p = 0.02). Women from the HAES group experienced significant weight loss at 4 months (?1.6 ± 2.5 kg, p < 0.0001), which did not differ significantly from the SS and control groups (p = 0.09). An increase in flexible restraint was significantly related to a greater weight loss in both HAES and SS groups (r = ?0.39, p < 0.01; and r = ?0.37, p < 0.05, respectively). A decrease in habitual susceptibility to disinhibition was also associated with a greater weight loss in HAES and control groups (r = 0.31, p < 0.05; and r = 0.44, p < 0.05, respectively). Discussion: These results suggest that a HAES intervention could have significant effects on eating behaviors and appetite ratings in premenopausal overweight women, when compared with an SS intervention or a control group. 相似文献
107.
It is well known that simultaneous presentation of incongruent audio and visual stimuli can lead to illusory percepts. Recent data suggest that distinct processes underlie non-specific intersensory speech as opposed to non-speech perception. However, the development of both speech and non-speech intersensory perception across childhood and adolescence remains poorly defined. Thirty-eight observers aged 5 to 19 were tested on the McGurk effect (an audio-visual illusion involving speech), the Illusory Flash effect and the Fusion effect (two audio-visual illusions not involving speech) to investigate the development of audio-visual interactions and contrast speech vs. non-speech developmental patterns. Whereas the strength of audio-visual speech illusions varied as a direct function of maturational level, performance on non-speech illusory tasks appeared to be homogeneous across all ages. These data support the existence of independent maturational processes underlying speech and non-speech audio-visual illusory effects. 相似文献
108.
Beginning in the early 1990s, the balsam fir sawfly (Neodiprion abietis) became a significant defoliating insect of precommercially thinned balsam fir (Abies balsamea (L.) Mill.) stands in western Newfoundland, Canada. In 1997, a nucleopolyhedrovirus (NeabNPV) was isolated from the balsam
fir sawfly and, as no control measures were then available, NeabNPV was developed for the biological control of balsam fir
sawfly. In order to register NeabNPV for operational use under the Canadian Pest Control Products Act, research was carried
out in a number of areas including NeabNPV field efficacy, non-target organism toxicology, balsam fir sawfly ecology and impact
on balsam fir trees, and NeabNPV genome sequencing and analysis. As part of the field efficacy trials, approximately 22 500
hectares of balsam fir sawfly-infested forest were aerially treated with NeabNPV between 2000 and 2005. NeabNPV was found
to be safe, efficacious, and economical for the suppression of balsam fir sawfly outbreak populations. Conditional registration
for the NeabNPV-based product, Abietiv™, was received from the Pest Management Regulatory Agency (Health Canada) in April
2006. In July 2006, Abietiv was applied by spray airplanes to 15 000 ha of balsam fir sawfly-infested forest in western Newfoundland
in an operational control program.
相似文献
109.
110.