全文获取类型
收费全文 | 929篇 |
免费 | 67篇 |
专业分类
996篇 |
出版年
2022年 | 7篇 |
2021年 | 5篇 |
2020年 | 8篇 |
2019年 | 10篇 |
2018年 | 8篇 |
2017年 | 6篇 |
2016年 | 12篇 |
2015年 | 31篇 |
2014年 | 34篇 |
2013年 | 51篇 |
2012年 | 55篇 |
2011年 | 57篇 |
2010年 | 27篇 |
2009年 | 26篇 |
2008年 | 53篇 |
2007年 | 43篇 |
2006年 | 47篇 |
2005年 | 44篇 |
2004年 | 29篇 |
2003年 | 46篇 |
2002年 | 47篇 |
2001年 | 13篇 |
2000年 | 13篇 |
1999年 | 20篇 |
1998年 | 14篇 |
1997年 | 9篇 |
1996年 | 14篇 |
1995年 | 8篇 |
1994年 | 12篇 |
1993年 | 8篇 |
1992年 | 10篇 |
1991年 | 15篇 |
1990年 | 17篇 |
1989年 | 16篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1986年 | 12篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1982年 | 11篇 |
1981年 | 11篇 |
1980年 | 9篇 |
1979年 | 15篇 |
1978年 | 12篇 |
1977年 | 9篇 |
1975年 | 7篇 |
1974年 | 10篇 |
1973年 | 12篇 |
1972年 | 7篇 |
1968年 | 5篇 |
排序方式: 共有996条查询结果,搜索用时 15 毫秒
81.
Reinertson RC Nelson VA Aunon SM Schlegel TT Lindgren KN Kerstman EL Arya M Paloski WH 《Journal of gravitational physiology : a journal of the International Society for Gravitational Physiology》2007,14(1):P9-13
The NASA artificial gravity-bed rest pilot study (AGPS) was designed to investigate the efficacy of daily exposure to a +Gz acceleration gradient for counteracting the physiologic decrements induced by prolonged bed rest. Test subjects were continuously monitored by a physician for signs and symptoms of pre-syncope, motion sickness, and arrhythmias while on the centrifuge. In this article, we have summarized the medical monitoring observations that were made during the AGPS and included an assessment of the relative usefulness of the information provided by the various monitoring tools in making a decision to terminate a centrifuge spin. 相似文献
82.
The first step in the olfactory perception is the activation by odorants of sensory neurones in the olfactory epithelium. In humans, this sensory epithelium is located at 2 narrow passages, the olfactory clefts, at the upper part of the nasal cavities. Little is known about the physiology of these clefts. We examined, in 34 patients, the impact of obstructed clefts upon detection and postlearning identification of 5 odorants. The location and extension of the obstructions were assessed using endoscopy, CT scans, and MRI. The inflammatory obstruction was usually bilateral, extending anteroposteriorly, and confined to the clefts, with no sign of obstruction or any inflammatory disease in the rest of the nasal cavities and sinuses. When tested with 5 odorants, these patients showed greatly impaired olfaction compared with a group of 73 normosmic subjects. The majority of these 34 patients had sensory deficits equivalent to that found in another group of 41 congenital anosmic patients, where inspection with MRI indicated the lack of olfactory bulbs. This study demonstrates that the olfactory clefts, in human, function as an entity that is different from other regions of the nasal cavity and is the target for local inflammatory events that are apparently not responding to corticoid and antibiotic treatments. 相似文献
83.
Jonas Strandberg Kjell Arne Johanson 《Journal of Zoological Systematics and Evolutionary Research》2011,49(2):110-118
The genus Apsilochorema Ulmer, 1907 is unique in the family Hydrobiosidae Ulmer, being widely distributed in the Palaearctic, Oriental and Australian Regions. All other 49 genera in the family, except the New World Atopsyche Banks, 1905, are confined to a single biogeographical Region. This unique distribution has independently stimulated researchers to formulate competing hypotheses about the biogeographical history of the genus. Molecular sequence data from mitochondrial cytochrome oxidase I (COI) and nuclear cadherin (CAD) genes of Apsilochorema species from the Oriental and Australian areas were analysed phylogenetically. The results retain a monophyletic Apsilochorema, which forms the sistergroup to the other genera in the subfamily Apsilochorematinae. The results from the biogeographical analyses dispute the earlier assumptions of an Oriental or northern Gondwana origin for the genus, revealing unambiguously an initial Australian radiation of the ancestral Apsilochorema with a subsequent dispersal into the Oriental Region. All but one of the Apsilochorema species occurring on the Pacific islands had an Oriental ancestor. The exception is the sistergroup to the New Caledonian species, which is found in both Australia and Oriental Regions. The molecular dating analysis, using a relaxed clock model, indicates that the genus Apsilochorema is about 36.4 MY old and that it dispersed from Australia into the Oriental Region about 28.3 Ma. It also gives an estimate of the approximate ages of the dispersals into New Caledonia to about 15.3 Ma; to the Solomon Islands at about 16.2 Ma; to the Fiji Islands at about 16.1 Ma; and to the Vanuatu Islands at about 5.4 Ma. 相似文献
84.
Borroto-Escuela DO Romero-Fernandez W García-Negredo G Correia PA Garriga P Fuxe K Ciruela F 《Cellular physiology and biochemistry》2011,28(5):1009-1022
Acetylcholine challenge produces M(3) muscarinic acetylcholine receptor activation and accessory/scaffold proteins recruitment into a signalsome complex. The dynamics of such a complex is not well understood but a conserved NPxxY motif located within transmembrane 7 and juxtamembrane helix 8 of the receptor was found to modulate G protein activation. Here by means of receptor mutagenesis we unravel the role of the conserved M(3) muscarinic acetylcholine receptor NPxxY motif on ligand binding, signaling and multiprotein complex formation. Interestingly, while a N7.49D receptor mutant showed normal ligand binding properties a N7.49A mutant had reduced antagonist binding and increased affinity for carbachol. Also, besides this last mutant was able to physically couple to Gα(q/11) after carbachol challenge it was neither capable to activate phospholipase C nor phospholipase D. On the other hand, we demonstrated that the Asn-7.49 is important for the interaction between M(3)R and ARF1 and also for the formation of the ARF/Rho/β γ signaling complex, a complex that might determine the rapid activation and desensitization of PLD. Overall, these results indicate that the NPxxY motif of the M(3) muscarinic acetylcholine receptor acts as key conformational switch for receptor signaling and multiprotein complex formation. 相似文献
85.
Kristine Bakke Westergaard Inger Greve Alsos Torstein Engelskjøn Kjell Ivar Flatberg Christian Brochmann 《Conservation Genetics》2011,12(5):1367-1371
The red-listed, amphi-Atlantic sedge Carex rufina is highly specialized to certain alpine snowbeds, and threatened by current changes in snow cover duration and moisture conditions.
Here we address its range-wide genetic diversity, history, and conservation using amplified fragment length polymorphisms
(AFLPs). Despite extensive primer testing, we detected very low overall diversity (4.1% polymorphic markers). Only a single
AFLP phenotype was found throughout Norway and across the Atlantic to Iceland and Greenland, while another was found in Canada,
suggesting glacial survival in one East and one West Atlantic refugium. East Atlantic C. rufina has probably been heavily bottlenecked in a small refugium, possibly situated within the maximum limits of the ice sheets.
Its lack of diversity is likely maintained through local clonal growth causing longevity of genotypes. Habitat availability
appears as the main limiting factor for C. rufina, and its currently occupied habitats need to be preserved to ensure its long-time survival. 相似文献
86.
Durand TC Sergeant K Renaut J Planchon S Hoffmann L Carpin S Label P Morabito D Hausman JF 《Journal of Proteomics》2011,74(8):1396-1410
The forest ecosystem is of particular importance from an economic and ecological perspective. However, the stress physiology of trees, perennial and woody plants, is far from being fully understood. For that purpose, poplar plants were exposed to drought; the plants exhibited commonly reported drought stress traits in the different plant tissues. Leafy rooted cuttings of poplar were investigated through a proteomic approach in order to compare the water constraint response of two plant tissues, namely leaf and cambium. Sampling was realized during the drought period at 2 time points with increased drought intensity and 7 days after rewatering. Our data show that there is a difference in the moment of response to the water constraint between the two tissues, cambium being affected later than leaves. In leaves, drought induced a decrease in rubisco content, and an increase in the abundance of light harvesting complex proteins as well as changes in membrane-related proteins. In the cambial tissue, the salient proteome pattern change was the decrease of multiple proteins identified as bark storage proteins. After rewatering, almost all changes in cambial proteome disappeared whereas a significant number of leaf proteins appeared to be differentially regulated only during the recovery from drought. 相似文献
87.
Refsum T Handeland K Baggesen DL Holstad G Kapperud G 《Applied and environmental microbiology》2002,68(11):5595-5599
Postmortem records of wild-living birds in Norway with laboratory-confirmed findings of salmonella infection were summarized for the period from 1969 to 2000. Salmonella spp. were isolated from 470 birds belonging to 26 species. The salmonella-positive birds included 441 small passerines, 15 gulls, 5 waterfowl, 4 birds of prey, 3 doves, and 2 crows. The bullfinch (Pyrrhula pyrrhula) was by far the most frequently recorded species (54% of the cases). Salmonella enterica serover Typhimurium was recovered from all cases except from one hooded crow (Corvus corone), which yielded serovar Paratyphi-B var. Java. Variant O:4,12 comprised 96% (451 cases) of all serovar Typhimurium isolates, including all the passerines, while variant O:4,5,12 accounted for the remaining 4% (18 cases). The occurrence of salmonellae in small passerines showed a distinct seasonality, with a peak in February and March. Plasmid profile analysis of 346 isolates of serovar Typhimurium O:4,12 detected six profiles, of which two comprised 66 and 28% of the isolates, respectively. Phage typing of 52 randomly selected isolates of serovar Typhimurium O:4,12 from passerines detected four types: DT 40 (54%), U277 (35%), DT 99 (6%), and DT 110 (4%). 相似文献
88.
Kapetanovic MC Lindqvist E Algulin J Jonsson K Saxne T Eberhardt K Geborek P 《Arthritis research & therapy》2011,13(1):R31
Introduction
Changes in bone mineral density (BMD) in the hand as evaluated by digital X-ray radiogrammetry (DXR) of the second to fourth metacarpal bones has been suggested to predict future joint damage in patients with rheumatoid arthritis (RA). This study's objective was to investigate whether DXR-BMD loss early in the course of the disease predicts the development of joint damage in RA patients followed for up to 20 years. 相似文献89.
Four possibly false-negative samples were detected when 514 male urine specimens were tested in the Amplicor Chlamydia trachomatis assay. In three of the four samples, the inhibition could be reduced by removal of urine supernatant. Under partially inhibitory conditions, after spiking with 50 C. trachomatis elementary bodies/ml specimen, a selective inhibition of the C. trachomatis target amplification and a preferential internal control amplification was observed. We conclude that a positive internal control signal might be misleading in inhibitory specimens with low amount of C. trachomatis. 相似文献
90.
Proliferative gill inflammation (PGI) causes significant losses in farmed Atlantic salmon Salmo salar L. in Norway, especially during the first months following seawater transfer. The aetiology is apparently multifactorial, including infection with chlamydia-like bacteria and Atlantic salmon paramyxovirus (ASPV). In the present study, gills from diseased fish from 3 farms on the western coast of Norway were sampled. The pathological changes were briefly described and the aetiological significance of ASPV studied by immunofluorescent staining of cryosections and by immunohistochemistry on sections of formalin-fixed and paraffin-embedded tissue. The pathological changes were macroscopically characterized by palour of the gills, and histologically by inflammation, circulatory disturbances, cell death and epithelial cell proliferation. ASPV was demonstrated in fish from all farms studied, as immunostaining consistent with ASPV was obtained in lamellar epithelial and endothelial cells of pathologically altered tissues. It is concluded that ASPV is at least a contributing cause of PGI. As far as we know, this is the first demonstration of fish disease related to infection with a paramyxovirus. 相似文献