全文获取类型
收费全文 | 1571篇 |
免费 | 188篇 |
出版年
2021年 | 16篇 |
2020年 | 13篇 |
2019年 | 13篇 |
2018年 | 19篇 |
2017年 | 24篇 |
2016年 | 30篇 |
2015年 | 72篇 |
2014年 | 40篇 |
2013年 | 77篇 |
2012年 | 86篇 |
2011年 | 99篇 |
2010年 | 59篇 |
2009年 | 45篇 |
2008年 | 77篇 |
2007年 | 66篇 |
2006年 | 72篇 |
2005年 | 62篇 |
2004年 | 60篇 |
2003年 | 63篇 |
2002年 | 80篇 |
2001年 | 54篇 |
2000年 | 63篇 |
1999年 | 60篇 |
1998年 | 40篇 |
1997年 | 32篇 |
1996年 | 18篇 |
1995年 | 28篇 |
1994年 | 28篇 |
1993年 | 29篇 |
1992年 | 32篇 |
1991年 | 41篇 |
1990年 | 29篇 |
1989年 | 18篇 |
1988年 | 22篇 |
1987年 | 11篇 |
1986年 | 12篇 |
1985年 | 25篇 |
1984年 | 9篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1979年 | 12篇 |
1978年 | 11篇 |
1977年 | 7篇 |
1976年 | 9篇 |
1975年 | 12篇 |
1974年 | 7篇 |
1973年 | 9篇 |
1971年 | 6篇 |
1968年 | 6篇 |
排序方式: 共有1759条查询结果,搜索用时 140 毫秒
1.
2.
Stein J. Janssen Annelien L. Bredenoord Wouter Dhert Marinus de Kleuver F. Cumhur Oner Jorrit-Jan Verlaan 《PloS one》2015,10(6)
Conflicts of interest arising from ties between pharmaceutical industry and physicians are common and may bias research. The extent to which these ties exist among editorial board members of medical journals is not known. This study aims to determine the prevalence and financial magnitude of potential conflicts of interest among editorial board members of five leading spine journals. The editorial boards of: The Spine Journal; Spine; European Spine Journal; Journal of Neurosurgery: Spine; and Journal of Spinal Disorders & Techniques were extracted on January 2013 from the journals’ websites. Disclosure statements were retrieved from the 2013 disclosure index of the North American Spine Society; the program of the 20th International Meeting on Advanced Spine Techniques; the program of the 48th Annual Meeting of the Scoliosis Research Society; the program of the AOSpine global spine congress; the presentations of the 2013 Annual Eurospine meeting; and the disclosure index of the American Academy of Orthopaedic Surgeons. Names of the editorial board members were compared with the individuals who completed a disclosure for one of these indexes. Disclosures were extracted when full names matched. Two hundred and ten (29%) of the 716 identified editorial board members reported a potential conflict of interest and 154 (22%) reported nothing to disclose. The remaining 352 (49%) editorial board members had no disclosure statement listed for one of the indexes. Eighty-nine (42%) of the 210 editorial board members with a potential conflict of interest reported a financial relationship of more than $10,000 during the prior year. This finding confirms that potential conflicts of interest exist in editorial boards which might influence the peer review process and can result in bias. Academia and medical journals in particular should be aware of this and strive to improve transparency of the review process. We emphasize recommendations that contribute to achieving this goal. 相似文献
3.
C. T. A. Evelo N. G. M. Palmen Y. Artur G. M. E. Janssen 《European journal of applied physiology and occupational physiology》1992,64(4):354-358
Previously sedentary men (n = 23) and women (n = 18) were trained to run a half marathon contest after 40 weeks. Total blood glutathione had increased by 20 weeks of training and had returned to normal after 40 weeks. Erythrocyte glutathione reductase activity had increased by 20 weeks and remained elevated after 40 weeks. This effect was accompanied by decreases in glutathione reductase coefficients, which indicated that increases in the presence of riboflavin may have been responsible for the changes in reductase activity. Erythrocyte glutathione S-transferase activity had increased slightly after 20 weeks of training and a much more marked increase was found after 40 weeks. This may have been indicative of the occurrence of lipid peroxidation in this phase of training. The participants ran a 15-km race after the first 20 weeks of training and a half marathon after 40 weeks. Blood glutathione tended to decrease after the 15-km race and increased after the half marathon. In both cases it had returned to normal values 5 days after the race. Erythrocyte glutathione reductase was elevated 1 day after the races, and had returned to normal after 5 days. This could also have been explained from concurrent changes in the riboflavin content of the erythrocytes. Erythrocyte glutathione S-transferase activity decreased after both races, but was restored 5 days after the half marathon while such was not the case after the 15-km race. 相似文献
4.
A. Van Aerschot P. Herdewijn G. Janssen H. Vanderhaeghe 《Nucleosides, nucleotides & nucleic acids》2013,32(4):519-536
Abstract The reaction of O-protected inosine with p-nitrophenyl ethanol under Mitsunobu conditions yields a mixture of the 1- and 0° -alkylated derivatives. 2′-Deoxyinosine protected on 06 -, can be synthesized fairly easy from deoxyguanosine with a Mitsunobu reaction followed by reductive deamination. 相似文献
5.
Vertical migration behaviour of diatom assemblages of Wadden Sea sediments (Dangast, Germany): a study using cryo-scanning electron microscopy. 总被引:1,自引:0,他引:1
The vertical migration behaviour of diatom assemblages inhabiting Wadden Sea sediments near Dangast (Germany) was investigated using cryo-scanning electron microscopy. The diatom assemblages were dominated by small Navicula species. Intertidal sediments which were located at different distances from the high tide level or stayed submerged even throughout low tides were chosen. Samples were prepared and cryofixed in the field. Sampling was restricted to three sets: (i) before the onset of vertical migration, (ii) 3 to 5 h after the onset of vertical migration, and (iii) before the area became flooded again or just prior to dusk. The diatom assemblages inhabiting the different types of sediments did not always show the same response. When the tidal cycle exposed the sediment surfaces during the night cell densities increased in the early morning hours with the onset of light. Later on, although the photon flux density was still increasing, cell densities stayed constant or decreased before the water flooded the areas around noon. In experiments in which the water drained off around noon and the areas became exposed throughout the entire afternoon, cell densities increased even up to dusk when the photon flux density had dropped to values below 20 microM photons m-2 s-1. In an experiment in which the last sampling occurred at 10.15 pm, when the photon flux density had already declined below 10 microM photons m-2 s-1, cell densities had decreased to lower values. This was ca. 1 h before the area was flooded again. Finally, cryo-scanning electron microscopy revealed frequently occurring micro-patches of diatom assemblages which could be differentiated into typical areas of lower and higher cell densities further complicating the pattern of light or water cover induced movements. 相似文献
6.
J P Koopman F G Janssen J A van Druten 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1975,149(4):995-999
The oxidation-reduction potential (ORP) in the cecal contents of conventional rats, germ-free mice, and mice with a Colonization Resistance Factor flora (CRF-mice) was investigated. By using animals that were anaesthetized for a longer period of time, we attempted to eliminate the disturbing influence of oxygen. In addition, measurements were made under anaerobic conditions. For the rats, the ORP values reached a more or less constant level after about 30 min following the insertion of the electrodes. The mean ORP at that time was -458 mV (SD = 45 mV). The mean ORP values for the mice showed a more gradual reduction than was found in the rats. The curves leveled off at about 100 min following the insertion of the electrodes. The mean ORP values 100 min after electrode insertion were: germ-free mice, + 3 mV (SD = 39 mV); CRF-mice, -554 mV (SD = 29 mV). In rats, the ORP value decreased after death; no decrease was observed in mice. No difference was found in the values obtained when measuring under anaerobic or aerobic conditions after death. 相似文献
7.
J J Schalken J J Janssen W J de Grip R K Hawkins S Sanyal 《Biochimica et biophysica acta》1985,839(1):122-126
In 020/A mice, homozygous for the retinal degeneration slow (rds) gene, the photoreceptor cells fail to develop outer segments, and in the absorption spectra of retinal extracts the rhodopsin peak is lacking. Application of an enzyme-linked immunoassay using antisera against bovine opsin shows, however, that opsin is present in the homozygous mutant retina (0.010 nmol/eye) at 3% of the level of the normal retina (0.38 nmol/eye) of Balb/c mice. In the retina of heterozygous mice the opsin level (0.19 nmol/eye) is about half of the normal. Detection of opsin in the rds mutant retina demonstrates the functional basis for the reported electroretinographic response and light-mediated reduction in cyclic nucleotide levels in this mutant. 相似文献
8.
- Several animal species are known to distinguish between their own eggs and eggs of unrelated conspecifics. However, the cues involved in this discrimination are often unknown. These cues were studied using the predatory mite Gynaeseius liturivorus Ehara.
- Adult females of these predatory mites oviposit in clusters and avoid oviposition close to eggs laid by other females, resulting in reduced cannibalism between offspring. Because predatory mites are blind, it was tested whether volatiles of eggs were used as a cue for egg recognition.
- Adult female predatory mites were offered volatile cues of their own eggs and of unrelated conspecific eggs, and females were prevented from contacting the eggs. Predatory mites oviposited closer to their own eggs than to unrelated eggs. This preference was observed even when one own and one unrelated egg were offered as a volatile source.
- These results suggest that adult female predatory mites can determine kinship using volatiles released from the eggs.
9.
10.
EA Dukhanina TI Lukyanova EA Romanova V Guerriero NV Gnuchev GP Georgiev DV Yashin LP Sashchenko 《Cell cycle (Georgetown, Tex.)》2015,14(22):3635-3643
PGRP-S (Tag7) is an innate immunity protein involved in the antimicrobial defense systems, both in insects and in mammals. We have previously shown that Tag7 specifically interacts with several proteins, including Hsp70 and the calcium binding protein S100A4 (Mts1), providing a number of novel cellular functions. Here we show that Tag7–Mts1 complex causes chemotactic migration of lymphocytes, with NK cells being a preferred target. Cells of either innate immunity (neutrophils and monocytes) or acquired immunity (CD4+ and CD8+ lymphocytes) can produce this complex, which confirms the close connection between components of the 2 branches of immune response. 相似文献