全文获取类型
收费全文 | 192篇 |
免费 | 0篇 |
专业分类
教育与普及 | 1篇 |
理论与方法论 | 4篇 |
现状及发展 | 62篇 |
研究方法 | 39篇 |
综合类 | 85篇 |
自然研究 | 1篇 |
出版年
2018年 | 3篇 |
2017年 | 4篇 |
2015年 | 1篇 |
2014年 | 1篇 |
2013年 | 1篇 |
2012年 | 11篇 |
2011年 | 11篇 |
2010年 | 5篇 |
2009年 | 1篇 |
2008年 | 8篇 |
2007年 | 12篇 |
2006年 | 11篇 |
2005年 | 4篇 |
2004年 | 7篇 |
2003年 | 7篇 |
2002年 | 6篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 9篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1992年 | 7篇 |
1990年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1980年 | 1篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1971年 | 7篇 |
1970年 | 4篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1967年 | 6篇 |
1965年 | 2篇 |
1964年 | 3篇 |
1962年 | 1篇 |
1955年 | 2篇 |
1948年 | 1篇 |
排序方式: 共有192条查询结果,搜索用时 15 毫秒
31.
L J Valentijn F Baas R A Wolterman J E Hoogendijk N H van den Bosch I Zorn A W Gabre?ls-Festen M de Visser P A Bolhuis 《Nature genetics》1992,2(4):288-291
We have investigated the peripheral myelin protein gene, PMP-22, in a family with Charcot-Marie-Tooth disease type 1A (CMT1A). The DNA duplication commonly found in CMT1A was absent in this family, but strong linkage existed between the disease and the CMT1A marker VAW409R3 on chromosome 17p11.2. We found a point mutation in PMP-22 which was completely linked with the disease. The mutation, a proline for leucine substitution in the first putative transmembrane domain, is identical to that recently found in the Trembler-J mouse. The presence of this PMP-22 defect in this CMT1A family and the location of PMP-22 within the DNA duplication associated with CMT1A suggest that both structural alteration and overexpression of PMP-22 may lead to the disease. 相似文献
32.
Delay in vesicle fusion revealed by electrochemical monitoring of single secretory events in adrenal chromaffin cells. 总被引:48,自引:0,他引:48
In synapses, a rise in presynaptic intracellular calcium leads to secretory vesicle fusion in less than a millisecond, as indicated by the short delay from excitation to postsynaptic signal. In nonsynaptic secretory cells, studies at high time resolution have been limited by the lack of a detector as fast and sensitive as the postsynaptic membrane. Electrochemical methods may be sensitive enough to detect catecholamines released from single vesicles. Here, we show that under voltage-clamp conditions, stochastically occurring signals can be recorded from adrenal chromaffin cells using a carbon-fibre electrode as an electrochemical detector. These signals obey statistics characteristic for quantal release; however, in contrast to neuronal transmitter release, secretion occurs with a significant delay after short step depolarizations. Furthermore, we identify a pedestal or 'foot' at the onset of unitary events which may represent the slow leak of catecholamine molecules out of a narrow 'fusion pore' before the pore dilates for complete exocytosis. 相似文献
33.
H Van den Bossche 《Nature》1978,273(5664):626-630
Although several good antiparasitic agents are available, new drugs are needed for the treatment of diseases such as chloroquine-resistant malaria, Chagas' disease, leishmaniasis and filariasis. The 'semirational approach' should be the basis for their synthesis. 相似文献
34.
35.
Raghoebarsing AA Smolders AJ Schmid MC Rijpstra WI Wolters-Arts M Derksen J Jetten MS Schouten S Sinninghe Damsté JS Lamers LP Roelofs JG Op den Camp HJ Strous M 《Nature》2005,436(7054):1153-1156
Wetlands are the largest natural source of atmospheric methane, the second most important greenhouse gas. Methane flux to the atmosphere depends strongly on the climate; however, by far the largest part of the methane formed in wetland ecosystems is recycled and does not reach the atmosphere. The biogeochemical controls on the efficient oxidation of methane are still poorly understood. Here we show that submerged Sphagnum mosses, the dominant plants in some of these habitats, consume methane through symbiosis with partly endophytic methanotrophic bacteria, leading to highly effective in situ methane recycling. Molecular probes revealed the presence of the bacteria in the hyaline cells of the plant and on stem leaves. Incubation with (13)C-methane showed rapid in situ oxidation by these bacteria to carbon dioxide, which was subsequently fixed by Sphagnum, as shown by incorporation of (13)C-methane into plant sterols. In this way, methane acts as a significant (10-15%) carbon source for Sphagnum. The symbiosis explains both the efficient recycling of methane and the high organic carbon burial in these wetland ecosystems. 相似文献
36.
37.
Numerical modelling of geological processes, such as mantle convection, flow in porous media, and geothermal heat transfer, has become quite common with the increase in computing and the availability o... 相似文献
38.
In the present paper I investigate the role that analogy plays in eighteenth-century biology and in Kant's philosophy of biology. I will argue that according to Kant, biology, as it was practiced in the eighteenth century, is fundamentally based on analogical reflection. However, precisely because biology is based on analogical reflection, biology cannot be a proper science. I provide two arguments for this interpretation. First, I argue that although analogical reflection is, according to Kant, necessary to comprehend the nature of organisms, it is also necessarily insufficient to fully comprehend the nature of organisms. The upshot of this argument is that for Kant our understanding of organisms is necessarily limited. Second, I argue that Kant did not take biology to be a proper science because biology was based on analogical arguments. I show that Kant stemmed from a philosophical tradition that did not assign analogical arguments an important justificatory role in natural science. Analogy, according to this conception, does not provide us with apodictically certain cognition. Hence, sciences based on analogical arguments cannot constitute proper sciences. 相似文献
39.
Vonk WI de Bie P Wichers CG van den Berghe PV van der Plaats R Berger R Wijmenga C Klomp LW van de Sluis B 《Cellular and molecular life sciences : CMLS》2012,69(1):149-163
Menkes disease (MD) is an X-linked recessive disorder characterized by copper deficiency resulting in a diminished function
of copper-dependent enzymes. Most MD patients die in early childhood, although mild forms of MD have also been described.
A diversity of mutations in the gene encoding of the Golgi-resident copper-transporting P1B-type ATPase ATP7A underlies MD. To elucidate the molecular consequences of the ATP7A mutations, various mutations in ATP7A associated with distinct phenotypes of MD (L873R, C1000R, N1304S, and A1362D) were analyzed in detail. All mutants studied
displayed changes in protein expression and intracellular localization parallel to a dramatic decline in their copper-transporting
capacity compared to ATP7A the wild-type. We restored these observed defects in ATP7A mutant proteins by culturing the cells
at 30°C, which improves the quality of protein folding, similar to that which as has recently has been demonstrated for misfolded
ATP7B, a copper transporter homologous to ATP7A. Further, the effect of the canine copper toxicosis protein COMMD1 on ATP7A
function was examined as COMMD1 has been shown to regulate the proteolysis of ATP7B proteins. Interestingly, in addition to
adjusted growth temperature, binding of COMMD1 partially restored the expression, subcellular localization, and copper-exporting
activities of the ATP7A mutants. However, no effect of pharmacological chaperones was observed. Together, the presented data
might provide a new direction for developing therapies to improve the residual exporting activity of unstable ATP7A mutant
proteins, and suggests a potential role for COMMD1 in this process. 相似文献
40.
Philippe J. R. Kok Mátyás A. Bittenbinder Joris K. van den Berg Sergio Marques-Souza Pedro M. Sales Nunes Alexandra E. Laking 《Journal of Natural History》2018,52(13-16):1029-1066
ABSTRACTThe gymnophthalmid lizard genus Neusticurus Duméril and Bibron, 1839 currently contains six described species. One of them, Neusticurus rudis Boulenger, 1900 has a long history of taxonomic confusion, and uncertainty remains about the number of species involved under that name, especially in the Pantepui region. Our molecular phylogenetic (concatenation and species tree) and morphological (morphometrics, external and hemipenial morphology) analyses confirm Neusticurus rudis as a species complex with several candidate species in the eastern Pantepui region. Neusticurus rudis is here redescribed based on the re-examination of the holotype and 10 specimens from the vicinity of the type locality (ca. 15 km airline) in Guyana. The geographic distribution of N. rudis sensu stricto is restricted to east of the Venezuelan Gran Sabana, extending from the slopes of Mount Roraima in Venezuela through the slopes of Maringma-tepui and Wayalayeng to Mount Ayanganna in Guyana, between 678 and 1500 m elevation. Populations tentatively assigned to N. rudis also occur from Mount Wokomung in the Pakaraima Mountains of Guyana to the Iwokrama Forest Reserve in Guyana, between 159 and 1234 m elevation. A new Neusticurus species is described from the uplands and highlands of the eastern Pantepui region, west of the Venezuelan Gran Sabana in Brazil and Venezuela, between 900 and 2200 m elevation. Populations provisionally assigned to the new species were also found from the La Escalera region to Chivatón, the summit of Abakapá-tepui and the slopes and summit of Auyán-tepui, Venezuela, between 1100 and 2203 m elevation. Our results suggest the Gran Sabana as a possible recent biogeographical barrier for the genus in the region and indicate that tepui-summit Neusticurus populations derive from uplands populations that shifted their habitat preference.www.zoobank.org/lsid:zoobank.org:pub:33DCF862-11CF-4FD0-B4D6-706E2C6A339E 相似文献