全文获取类型
收费全文 | 4838篇 |
免费 | 447篇 |
国内免费 | 1篇 |
出版年
2023年 | 19篇 |
2021年 | 75篇 |
2020年 | 58篇 |
2019年 | 71篇 |
2018年 | 77篇 |
2017年 | 70篇 |
2016年 | 105篇 |
2015年 | 207篇 |
2014年 | 230篇 |
2013年 | 245篇 |
2012年 | 378篇 |
2011年 | 339篇 |
2010年 | 204篇 |
2009年 | 193篇 |
2008年 | 264篇 |
2007年 | 254篇 |
2006年 | 233篇 |
2005年 | 249篇 |
2004年 | 230篇 |
2003年 | 211篇 |
2002年 | 207篇 |
2001年 | 88篇 |
2000年 | 96篇 |
1999年 | 74篇 |
1998年 | 61篇 |
1997年 | 42篇 |
1996年 | 39篇 |
1995年 | 57篇 |
1994年 | 36篇 |
1993年 | 38篇 |
1992年 | 54篇 |
1991年 | 65篇 |
1990年 | 69篇 |
1989年 | 61篇 |
1988年 | 46篇 |
1987年 | 40篇 |
1986年 | 42篇 |
1985年 | 38篇 |
1984年 | 37篇 |
1983年 | 22篇 |
1981年 | 18篇 |
1979年 | 22篇 |
1978年 | 19篇 |
1977年 | 21篇 |
1976年 | 19篇 |
1975年 | 20篇 |
1974年 | 23篇 |
1973年 | 16篇 |
1971年 | 16篇 |
1969年 | 21篇 |
排序方式: 共有5286条查询结果,搜索用时 15 毫秒
1.
2.
3.
E Ortega Rincón J M Marchena J J García A Schmidt T Schulz I Malpica A B Rodríguez C Barriga H Michna H L?tzerich 《Journal of applied physiology》2001,91(3):1067-1072
Flow cytometer measurements were made of the basal variations in peripheral blood functional monocytes and granulocytes over the course of a training season (January to November) of a cycling team. Parallel determinations were made of plasma concentration of catecholamines (chromatography) and cortisol (RIA) in a search for neuroendocrine markers. The results showed the greatest phagocytic capacity to occur in the central months (March, May, and July), coinciding with the greatest number and highest level of competitive events with good correlation with a peak in epinephrine during these months (r(2) = 0.998 for monocytes and r(2) = 0.674 for granulocytes). No good correlations were found between phagocytosis and norepinephrine or cortisol. The highest values for phagocytosis and epinephrine concentration were found in May. These results suggest that blood epinephrine concentration could be a good neuroendocrine marker of sportspeople's phagocytic response. 相似文献
4.
Valentina Isetta Josep M. Montserrat Raquel Santano Alison J. Wimms Dinesh Ramanan Holger Woehrle Daniel Navajas Ramon Farré 《PloS one》2016,11(3)
Bench testing is a useful method to characterize the response of different automatic positive airway pressure (APAP) devices under well-controlled conditions. However, previous models did not consider the diversity of obstructive sleep apnea (OSA) patients’ characteristics and phenotypes. The objective of this proof-of-concept study was to design a new bench test for realistically simulating an OSA patient’s night, and to implement a one-night example of a typical female phenotype for comparing responses to several currently-available APAP devices. We developed a novel approach aimed at replicating a typical night of sleep which includes different disturbed breathing events, disease severities, sleep/wake phases, body postures and respiratory artefacts. The simulated female OSA patient example that we implemented included periods of wake, light sleep and deep sleep with positional changes and was connected to ten different APAP devices. Flow and pressure readings were recorded; each device was tested twice. The new approach for simulating female OSA patients effectively combined a wide variety of disturbed breathing patterns to mimic the response of a predefined patient type. There were marked differences in response between devices; only three were able to overcome flow limitation to normalize breathing, and only five devices were associated with a residual apnea-hypopnea index of <5/h. In conclusion, bench tests can be designed to simulate specific patient characteristics, and typical stages of sleep, body position, and wake. Each APAP device behaved differently when exposed to this controlled model of a female OSA patient, and should lead to further understanding of OSA treatment. 相似文献
5.
6.
7.
Syee Weldeab Kay-Christian EmeisChristoph Hemleben Gerhard SchmiedlHartmut Schulz 《Palaeogeography, Palaeoclimatology, Palaeoecology》2003,191(2):169-190
We investigated five time-equivalent core sections (180-110 kyr BP) from the Balearic Sea (Menorca Rise), the easternmost Levantine Basin and southwest, south, and southeast of Crete to reconstruct spatial patterns of productivity during deposition of sapropels S5 and S6 in the Mediterranean Sea. Our indicators are Ba, total organic carbon and carbonate contents. We found no indications of Ba remobilization within the investigated core intervals, and used the accumulation rate of biogenic Ba to compute paleoproductivity. Maximum surface water productivity (up to 350 g C/m2/yr) was found during deposition of S5 (isotope stage 5e) but pronounced spatial variability is evident. Coeval sediment intervals in the Balearic Sea show very little productivity change, suggesting that chemical and biological environments in the eastern and western Mediterranean basins were decoupled in this interval. We interpret the spatial variability as the result of two different modes of nutrient delivery to the photic zone: river-derived nutrient input and shoaling of the pycnocline/nutricline to the photic zone. The productivity increase during the formation of S6 was moderate compared to S5 and had a less marked spatial variability within the study area of the eastern Mediterranean Sea. Given that S6 formed during a glacial interval, glacial boundary conditions such as high wind stress and/or cooler surface water temperatures apparently favored lateral and vertical mixing and prevented the development of the spatial gradients within the Eastern Mediterranean Sea (EMS) observed for S5. A non-sapropel sediment interval with elevated Ba content and depleted 18O/16O ratios in planktonic foraminifer calcite was detected between S6 and S5 that corresponds to the weak northern hemisphere insolation maximum at 150 kyr. At this time, productivity apparently increased up to five times over surrounding intervals, but abundant benthic fauna show that the deep water remained oxic. Following our interpretation, the interval denotes a failed sapropel, when a weaker monsoon did not force the EMS into permanent stratification. The comparison of interglacial and glacial sapropels illustrates the relevance of climatic boundary conditions in the northern catchment in determining the facies and spatial variability of sapropels within the EMS. 相似文献
8.
Sixteen raptors, including one eagle, two falcons, five hawks and eight owls, were found to have developmental ocular lesions. The most common lesion was microphthalmia. Other findings included cataract, microphakia, retinal dysplasia, malformation of the ciliary body, choroid and pecten, and lentoid formation. Specific causes for these lesions could not be determined. It is hypothesized that developmental ocular disease probably is more common than available reports indicate. 相似文献
9.
10.