全文获取类型
收费全文 | 322篇 |
免费 | 28篇 |
出版年
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 4篇 |
2019年 | 14篇 |
2018年 | 10篇 |
2017年 | 5篇 |
2016年 | 10篇 |
2015年 | 13篇 |
2014年 | 17篇 |
2013年 | 22篇 |
2012年 | 14篇 |
2011年 | 18篇 |
2010年 | 15篇 |
2009年 | 9篇 |
2008年 | 23篇 |
2007年 | 23篇 |
2006年 | 14篇 |
2005年 | 12篇 |
2004年 | 14篇 |
2003年 | 13篇 |
2002年 | 13篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 10篇 |
1993年 | 8篇 |
1992年 | 3篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1965年 | 1篇 |
排序方式: 共有350条查询结果,搜索用时 31 毫秒
21.
Background
Studies have shown an increase in mortality and morbidity during heatwaves, especially among the elderly. We assessed the knowledge of the general population of Brussels and Amsterdam on groups at risk and protective measures for heat-related health effects.Results
Six locations with mixed populations were selected in each city. Passer-by’s in both cities were asked to participate in a short survey. Respondents in Brussels (n = 120) had significantly more knowledge on risk groups and protective measures than respondents in Amsterdam (n = 133). In both cities, individuals with higher education had better knowledge on risk groups and protective measures than individuals with lower education.Conclusions
Efforts at heat-awareness raising must be strengthened, especially in Amsterdam, and public health actions should effectively target vulnerable groups with lower education in both cities.22.
Wimke Fokkema Wendy de Boer Henk P. van der Jeugd Adriaan Dokter Bart A. Nolet Luit J. De Kok J. Theo M. Elzenga Han Olff 《Oikos》2016,125(6):804-811
In different ecosystems herbivores highly prefer particular plant species. This is often explained in a stoichiometric framework of nutrient‐based plant adaptations to herbivory. We hypothesize that such super‐palatability can also arise as an evolutionary by‐product of osmoregulatory adaptations of plants to stressful environmental conditions, as salinity, drought and cold. Here, we investigate in a coastal salt marsh why some plant species are highly preferred by migratory brent geese Branta bernicla bernicla in spring while others are avoided. This salt marsh is an important spring staging site for the geese. Sufficient energy storage in a short period is critical to enable their northward migration to Siberia and subsequent reproduction. We test if geese prefer plants that balance their internal osmotic potential with the saline environment through energy‐rich soluble sugars over plant species that use (compartmentalized) salts for this. We find that plant nitrogen and acid detergent fiber content, classic predictors of herbivore preferences, poorly explain which plants the geese prefer. Instead, plant species that are highly preferred by the geese adapt to salinity by high soluble sugar concentrations while avoided species do this by high plant salt concentrations. Thus, the type of osmoregulatory adaptation to stress displayed by different plant species is a good predictor for the food preference of geese on this salt marsh. We suggest that variation in other types of osmoregulation‐based stress adaptations, as plant cold adaptations in tundras and plant drought adaptations in savannas, have similar important consequences for trophic interactions. 相似文献
23.
Sebastian H. Grimm Berend Gagestein Jordi F. Keijzer Nora Liu Ruud H. Wijdeven Eelke B. Lenselink Adriaan W. Tuin Adrianus M.C.H. van den Nieuwendijk Gerard J.P. van Westen Constant A.A. van Boeckel Herman S. Overkleeft Jacques Neefjes Mario van der Stelt 《Bioorganic & medicinal chemistry》2019,27(5):692-699
Acute myeloid leukemia (AML) is characterized by fast progression and low survival rates, in which Fms-like tyrosine kinase 3 (FLT3) receptor mutations have been identified as a driver mutation in cancer progression in a subgroup of AML patients. Clinical trials have shown emergence of drug resistant mutants, emphasizing the ongoing need for new chemical matter to enable the treatment of this disease. Here, we present the discovery and topological structure-activity relationship (SAR) study of analogs of isoquinolinesulfonamide H-89, a well-known PKA inhibitor, as FLT3 inhibitors. Surprisingly, we found that the SAR was not consistent with the observed binding mode of H-89 in PKA. Matched molecular pair analysis resulted in the identification of highly active sub-nanomolar azaindoles as novel FLT3-inhibitors. Structure based modelling using the FLT3 crystal structure suggested an alternative, flipped binding orientation of the new inhibitors. 相似文献
24.
Nicky HGM Peters Inne HM Borel Rinkes Willem PTM Mali Maurice AAJ van den Bosch Remmert K Storm Peter W Plaisier Erwin de Boer Adriaan J van Overbeeke Petra HM Peeters 《Trials》2007,8(1):1-7
Background
In orthodontic treatment, anchorage control is a fundamental aspect. Usually conventional mechanism for orthodontic anchorage control can be either extraoral or intraoral that is headgear or intermaxillary elastics. Their use are combined with various side effects such as tipping of occlusal plane or undesirable movements of teeth. Especially in cases, where key-teeth are missing, conventional anchorage defined as tooth-borne anchorage will meet limitations. Therefore, the use of endosseous implants for anchorage purposes are increasingly used to achieve positional stability and maximum anchorage.Methods/Design
The intended study is designed as a prospective, multicenter randomized controlled trial (RCT), comparing and contrasting the effect of early loading of palatal implant therapy versus implant loading after 12 weeks post implantation using the new ortho-implant type II anchor system device (Orthosystem Straumann, Basel, Switzerland). 124 participants, mainly adult males or females, whose diagnoses require temporary stationary implant-based anchorage treatment will be randomized 1:1 to one of two treatment groups: group 1 will receive a loading of implant standard therapy after a healing period of 12 week (gold standard), whereas group 2 will receive an early loading of orthodontic implants within 1 week after implant insertion. Participants will be at least followed for 12 months after implant placement. The primary endpoint is to investigate the behavior of early loaded palatal implants in order to find out if shorter healing periods might be justified to accelerate active orthodontic treatment. Secondary outcomes will focus e.g. on achievement of orthodontic treatment goals and quantity of direct implant-bone interface of removed bone specimens. As tertiary objective, a histologic and microtomography evaluation of all retrieved implants will be performed to obtain data on the performance of the SLA surface in human bone evaluation of all retrieved implants. Additionally, resonance frequency analysis (RFA, Osstell? mentor) will be used at different times for clinically monitoring the implant stability and for histological comparison in order to measure the reliability of the resonance frequency measuring device.Trial registration
Current Controlled Trials ISRCTN97142521. 相似文献25.
The mechanism and regulation of coffee seed germination were studied in Coffea arabica L. cv. Rubi. The coffee embryo grew inside the endosperm prior to radicle protrusion and abscisic acid (ABA) inhibited the increase in its pressure potential. There were two steps of endosperm cap weakening. An increase in cellulase activity coincided with the first step and an increase in endo--mannanase (EBM) activity with the second step. ABA inhibited the second step of endosperm cap weakening, presumably by inhibiting the activities of at least two EBM isoforms and/or, indirectly, by inhibiting the pressure force of the radicle. The increase in the activities of EBM and cellulase coincided with the decrease in the force required to puncture the endosperm and with the appearance of porosity in the cell walls as observed by low-temperature scanning electronic microscopy. Tissue printing showed that EBM activity was spatially regulated in the endosperm. Activity was initiated in the endosperm cap whereas later during germination it could also be detected in the remainder of the endosperm. Tissue printing revealed that ABA inhibited most of the EBM activity in the endosperm cap, but not in the remainder of the endosperm. ABA did not inhibit cellulase activity. There was a transient rise in ABA content in the embryo during imbibition, which was likely to be responsible for slow germination, suggesting that endogenous ABA also may control embryo growth potential and the second step of endosperm cap weakening during coffee seed germination. 相似文献
26.
27.
The goal of this study was to prospectively assess the long-term results of ruby laser depilation in 346 consecutive patients who underwent hair removal at 402 anatomical sites. The patients were treated using a ruby laser, with mean power ranging from 8.6 J to 15.7 J according to skin type. Results were assessed using two outcome measures-the percentage reduction in hair density and the hair-free interval. The median reduction in hair density was 55 percent (range, 0 to 100 percent) at a median time of 1 year after the last treatment session. The median hair-free interval was 8 weeks. Patients underwent a median number of four treatment sessions. Forty-three of the 346 patients were treated at more than one anatomical site. Of the sites treated, 75 percent reduction in hair density was achieved in 22 percent, 90 percent reduction was achieved in 2.2 percent, and complete depilation was achieved in only 0.7 percent. Darker colored hair was more effectively treated. Treatment efficacy was not affected by anatomical site, with the exception of the faces of male patients, which were found to be particularly resistant to treatment. There was a significant correlation between the number of treatments given and the outcome. The overall complication rate was 9.0 percent (36 of 402 sites) with respect to pigmentary changes and blistering, but varied according to Fitzpatrick skin type. The complication rate was highest in skin types V and VI (24.7 percent), with no complications in skin type I. Although a greater than 50 percent reduction in hair density was achieved in half of the 346 patients treated, complete depilation was achieved in only an extremely limited number of patients. 相似文献
28.
Duijvestijn YC Cobben JM Leegte B de Vries TW 《Genetic counseling (Geneva, Switzerland)》2002,13(1):49-54
A family with primary infertility and two members with mental retardation and subtle facial dysmorphism is described. In the two retarded persons chromosomal rearrangements (partial monosomy of chromosome 5 and partial trisomy of chromosome 7) were detected. One member of the family had died with major congenital malformations. Her fibroblasts had been stored and her chromosomes showed the inverse pattern (partial trisomy of chromosome 5 and partial monosomy of chromosome 7). It appeared that in familial mental retardation with or without congenital malformations FISH-techniques should be used to detect submicroscopic chromosomal aberrations, which are not detectable by routine chromosome studies. 相似文献
29.
Lens PN Gastesi R Vergeldt F van Aelst AC Pisabarro AG Van As H 《Applied and environmental microbiology》2003,69(11):6644-6649
The diffusive properties of anaerobic methanogenic and sulfidogenic aggregates present in wastewater treatment bioreactors were studied using diffusion analysis by relaxation time-separated pulsed-field gradient nuclear magnetic resonance (NMR) spectroscopy and NMR imaging. NMR spectroscopy measurements were performed at 22 degrees C with 10 ml of granular sludge at a magnetic field strength of 0.5 T (20 MHz resonance frequency for protons). Self-diffusion coefficients of H(2)O in the investigated series of mesophilic aggregates were found to be 51 to 78% lower than the self-diffusion coefficient of free water. Interestingly, self-diffusion coefficients of H(2)O were independent of the aggregate size for the size fractions investigated. Diffusional transport occurred faster in aggregates growing under nutrient-rich conditions (e.g., the bottom of a reactor) or at high (55 degrees C) temperatures than in aggregates cultivated in nutrient-poor conditions or at low (10 degrees C) temperatures. Exposure of aggregates to 2.5% glutaraldehyde or heat (70 or 90 degrees C for 30 min) modified the diffusional transport up to 20%. In contrast, deactivation of aggregates by HgCl(2) did not affect the H(2)O self-diffusion coefficient in aggregates. Analysis of NMR images of a single aggregate shows that methanogenic aggregates possess a spin-spin relaxation time and self-diffusion coefficient distribution, which are due to both physical (porosity) and chemical (metal sulfide precipitates) factors. 相似文献
30.