全文获取类型
收费全文 | 194篇 |
免费 | 8篇 |
专业分类
202篇 |
出版年
2020年 | 2篇 |
2019年 | 1篇 |
2016年 | 4篇 |
2015年 | 11篇 |
2014年 | 8篇 |
2013年 | 14篇 |
2012年 | 17篇 |
2011年 | 13篇 |
2010年 | 6篇 |
2009年 | 7篇 |
2008年 | 3篇 |
2007年 | 5篇 |
2006年 | 5篇 |
2005年 | 18篇 |
2004年 | 8篇 |
2003年 | 9篇 |
2002年 | 7篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1993年 | 2篇 |
1992年 | 6篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 5篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 2篇 |
1971年 | 1篇 |
1923年 | 1篇 |
1919年 | 1篇 |
1914年 | 1篇 |
排序方式: 共有202条查询结果,搜索用时 15 毫秒
41.
Terje Lislevand Bohumír Chutný Ingvar Byrkjedal Václav Pavel Martins Briedis Peter Adamik 《Bird Study》2013,60(4):508-515
Capsule Red-spotted Bluethroats Luscinia s. svecica from two European breeding populations spent the boreal winter on the Indian sub-continent.Aim Tracking the migration of Red-spotted Bluethroats from Europe to the hitherto unknown non-breeding areas and back.Methods Light-level geolocators were deployed on male Bluethroats at breeding sites in the Czech Republic (n?=?10) and in Norway (n?=?30). Recorded light intensity data were used to estimate the locations of non-breeding sites and migration phenology during the annual cycle.Results Bluethroats spent the boreal winter in India (n?=?3) and Pakistan (n?=?1), on average more than 6000?km from their breeding areas. Autumn migration started in August (n?=?1) or early September (n?=?2), and lasted for 26–74 days. Spring migration commenced on 8 and 9 April (n?=?2) and lasted for about a month. During both autumn and spring migration, birds stopped over two or three times for more than 3 days.Conclusion This study for the first time showed where Red-spotted Bluethroats from European breeding populations stay during the boreal winter. This seems to be the first time that a passerine bird has been tracked along the Indo-European flyway. 相似文献
42.
Resident female Northern Lapwings Vanellus vanellus fight to exclude settlement by secondary females
In systems with bi‐parental care, sexual conflict theory states that a transition from monogamy to polygyny should increase fitness prospects for males and reduce fitness prospects of resident females. Behavioural observations of Northern Lapwings Vanellus vanellus suggested that resident females try to monopolize their breeding resources by attacking females prospecting for secondary status, and males commonly respond by intervening on behalf of the prospecting females. In four territories the resident females successfully defended their monogamous status, in nine territories the resident females made at least one successful eviction before being forced to accept polygyny and in nine territories observed eviction attempts were unsuccessful. These observations indicate that mating status in Northern Lapwings is partly determined by the competitive ability of resident females. 相似文献
43.
Bröde P Fiala D Błażejczyk K Holmér I Jendritzky G Kampmann B Tinz B Havenith G 《International journal of biometeorology》2012,56(3):481-494
The Universal Thermal Climate Index (UTCI) aimed for a one-dimensional quantity adequately reflecting the human physiological
reaction to the multi-dimensionally defined actual outdoor thermal environment. The human reaction was simulated by the UTCI-Fiala
multi-node model of human thermoregulation, which was integrated with an adaptive clothing model. Following the concept of
an equivalent temperature, UTCI for a given combination of wind speed, radiation, humidity and air temperature was defined
as the air temperature of the reference environment, which according to the model produces an equivalent dynamic physiological
response. Operationalising this concept involved (1) the definition of a reference environment with 50% relative humidity
(but vapour pressure capped at 20 hPa), with calm air and radiant temperature equalling air temperature and (2) the development
of a one-dimensional representation of the multivariate model output at different exposure times. The latter was achieved
by principal component analyses showing that the linear combination of 7 parameters of thermophysiological strain (core, mean
and facial skin temperatures, sweat production, skin wettedness, skin blood flow, shivering) after 30 and 120 min exposure
time accounted for two-thirds of the total variation in the multi-dimensional dynamic physiological response. The operational
procedure was completed by a scale categorising UTCI equivalent temperature values in terms of thermal stress, and by providing
simplified routines for fast but sufficiently accurate calculation, which included look-up tables of pre-calculated UTCI values
for a grid of all relevant combinations of climate parameters and polynomial regression equations predicting UTCI over the
same grid. The analyses of the sensitivity of UTCI to humidity, radiation and wind speed showed plausible reactions in the
heat as well as in the cold, and indicate that UTCI may in this regard be universally useable in the major areas of research
and application in human biometeorology. 相似文献
44.
Aim
The main aim of this study was to assess if the perception of thermal pain thresholds is associated with genetically inferred levels of expression of the 5-HT transporter (5-HTT). Additionally, the perception of the so-called thermal grill illusion (TGI) was assessed. Forty-four healthy individuals (27 females, 17 males) were selected a-priori based on their 5-HTTLPR/rs25531 (‘tri-allelic 5-HTTLPR’) genotype, with inferred high or low 5-HTT expression. Thresholds for heat- and cold-pain were determined along with the sensory and affective dimensions of the TGI.Results
Thresholds to heat- and cold-pain correlated strongly (rho = −0.58, p<0.001). Individuals in the low 5-HTT-expressing group were significantly less sensitive to heat-pain (p = 0.02) and cold-pain (p = 0.03), compared to the high-expressing group. A significant gender-by-genotype interaction also emerged for cold-pain perception (p = 0.02); low 5-HTT-expressing females were less sensitive. The TGI was rated as significantly more unpleasant (affective-motivational dimension) than painful (sensory-discriminatory dimension), (p<0.001). Females in the low 5-HTT expressing group rated the TGI as significantly less unpleasant than high 5-HTT expressing females (p<0.05), with no such differences among men.Conclusion/Significance
We demonstrate an association between inferred low 5-HTT expression and elevated thresholds to thermal pain in healthy non-depressed individuals. Despite the fact that reduced 5-HTT expression is a risk factor for chronic pain we found it to be related to hypoalgesia for threshold thermal pain. Low 5-HTT expression is, however, also a risk factor for depression where thermal insensitivity is often seen. Our results may thus contribute to a better understanding of the molecular underpinnings of such paradoxical hypoalgesia. The results point to a differential regulation of thermoafferent-information along the neuraxis on the basis of 5-HTT expression and gender. The TGI, suggested to rely on the central integration of thermoafferent-information, may prove a valuable tool in probing the affective-motivational dimension of these putative mechanisms. 相似文献45.
Berit Sverdrup Henrik K?llberg Camilla Bengtsson Ingvar Lundberg Leonid Padyukov Lars Alfredsson Lars Klareskog the Epidemiological Investigation of Rheumatoid Arthritis study group 《Arthritis research & therapy》2005,7(6):R1296
The aim of the present study was to investigate the association between exposure to mineral oil and the risk of developing
rheumatoid arthritis (RA), and in addition to perform a separate analysis on the major subphenotypes for the disease; namely,
rheumatoid factor (RF)-positive RA, RF-negative RA, anticitrulline-positive RA and anticitrulline-negative RA, respectively.
A population-based case–control study of incident cases of RA was performed among the population aged 18–70 years in a defined
area of Sweden during May 1996–December 2003. A case was defined as an individual from the study base who for the first time
received a diagnosis of RA according to the American College of Rheumatology criteria of 1987. Controls were randomly selected
from the study base with consideration taken for age, gender and residential area. Cases (n = 1,419) and controls (n = 1,674) answered an extensive questionnaire regarding lifestyle factors and occupational exposures, including different
types of mineral oils. Sera from cases and controls were investigated for RF and anticitrulline antibodies. 相似文献
46.
Leknes IL 《Zoology (Jena, Germany)》2004,107(3):201-204
This paper describes the localization and structure of melano-macrophage centres (MMCs) in the liver of platyfish (Xiphophorus maculatus), compares these centres with corresponding structures in the spleen and kidney of various teleosts and gives suggestions about their functions. The MMCs were closely apposed to the endothelial layer of liver venules covered with pancreas tissue, i.e. portal venules, and contained numerous cells displaying large amounts of Prussian blue precipitations in tissue treated with acid ferrocyanide. Thus, these centres were rich in ferric compounds, probably haemosiderin, and are suggested to be involved in the normal storage, relocation and recycling of iron compounds from effete or damaged red blood cells of the portal venule system in this species. 相似文献
47.
48.
Catherine A. Koss Leah G. Jarlsberg Saskia den Boon Adithya Cattamanchi J. Lucian Davis William Worodria Irene Ayakaka Ingvar Sanyu Laurence Huang International HIV-associated Opportunistic Pneumonias Study 《PloS one》2015,10(5)
BackgroundPneumonia is a major cause of mortality among HIV-infected patients. Pneumonia severity scores are promising tools to assist clinicians in predicting patients’ 30-day mortality, but existing scores were developed in populations infected with neither HIV nor tuberculosis (TB) and include laboratory data that may not be available in resource-limited settings. The objective of this study was to develop a score to predict mortality in HIV-infected adults with pneumonia in TB-endemic, resource-limited settings.MethodsWe conducted a secondary analysis of data from a prospective study enrolling HIV-infected adults with cough ≥2 weeks and <6 months and clinically suspected pneumonia admitted to Mulago Hospital in Kampala, Uganda from September 2008 to March 2011. Patients provided two sputum specimens for mycobacteria, and those with Ziehl-Neelsen sputum smears that were negative for mycobacteria underwent bronchoscopy with inspection for Kaposi sarcoma and testing for mycobacteria and fungi, including Pneumocystis jirovecii. A multivariable best subsets regression model was developed, and one point was assigned to each variable in the model to develop a clinical predictor score for 30-day mortality.ResultsOverall, 835 patients were studied (mean age 34 years, 53.4% female, 30-day mortality 18.2%). A four-point clinical predictor score was identified and included heart rate >120 beats/minute, respiratory rate >30 breaths/minute, oxygen saturation <90%, and CD4 cell count <50 cells/mm3. Patients’ 30-day mortality, stratified by score, was: score 0 or 1, 12.6%, score 2 or 3, 23.4%, score 4, 53.9%. For each 1 point change in clinical predictor score, the odds of 30-day mortality increased by 65% (OR 1.65, 95% CI 1.39-1.96, p <0.001).ConclusionsA simple, four-point scoring system can stratify patients by levels of risk for mortality. Rapid identification of higher risk patients combined with provision of timely and appropriate treatment may improve clinical outcomes. This predictor score should be validated in other resource-limited settings. 相似文献
49.
Chunyan Zhao Rajiv Kumar Kolbjorn Zahlsen Heidi Bager Sundmark Kari Hemminki Ingvar Eide 《Biomarkers》1997,2(6):355-360
Quantification of 7 2 hydroxyethyl guanine 7 HEG adduct in DNA of livers and lymphocytes of male Sprague-Dawley rats exposed to 300 ppm ethene by inhalation 12 h a day for three consecutive days was performed to evaluate the potential of ethene to produce DNA adducts in these tissues. The persistence of 7 HEG in livers and lymphocytes was studied in rats sacrificed 0, 1, 5, and 20 days after the last exposure. DNA samples from control and treated animals were analysed for 7 HEG and 7 methylguanine 7 MG adducts by thin layer chromatography TLC combined with a high pressure liquid chromatography HPLC assay. After a 3 day exposure to ethene, 7 HEG accumulated to a similar extent in liver and lymphocytes, with the mean adduct level of 7.0 0.7 adducts per 107 nucleotides in liver and 7.4 0.7 adducts per 107 nucleotides in lymphocytes of rats sacrificed immediately after cessation of exposure. The approximate half life of 7 HEG was 5 days in liver and 3 days in lymphocytes, which is consistent with the loss of adduct primarily by spontaneous depurination. In addition, the background levels of 7 HEG and 7 MG were determined in the liver and lymphocytes from the control rats. 相似文献
50.