全文获取类型
收费全文 | 596篇 |
免费 | 43篇 |
国内免费 | 17篇 |
专业分类
656篇 |
出版年
2024年 | 1篇 |
2023年 | 17篇 |
2022年 | 7篇 |
2021年 | 14篇 |
2020年 | 20篇 |
2019年 | 12篇 |
2018年 | 22篇 |
2017年 | 13篇 |
2016年 | 16篇 |
2015年 | 19篇 |
2014年 | 24篇 |
2013年 | 41篇 |
2012年 | 17篇 |
2011年 | 19篇 |
2010年 | 22篇 |
2009年 | 26篇 |
2008年 | 31篇 |
2007年 | 31篇 |
2006年 | 29篇 |
2005年 | 22篇 |
2004年 | 22篇 |
2003年 | 25篇 |
2002年 | 11篇 |
2001年 | 12篇 |
2000年 | 15篇 |
1999年 | 29篇 |
1998年 | 14篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 10篇 |
1993年 | 2篇 |
1992年 | 12篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1987年 | 8篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有656条查询结果,搜索用时 15 毫秒
141.
Rapid reduction in parvalbumin concentration during chronic stimulation of rabbit fast twitch muscle 总被引:4,自引:0,他引:4
Chronic indirect stimulation of fast twitch rabbit muscle induced a rapid reduction in parvalbumin concentration. When compared to the unstimulated contralateral muscle, parvalbumins were reduced to 55% following 6 days of stimulation. Prolonged stimulation further reduced parvalbumins so that they were undetectable after 28 days. The time course of these changes appears to be related with the previously observed changes in the sarcoplasmic reticulum. 相似文献
142.
143.
V. V. Smolyaninov 《Biophysics》2009,54(1):94-102
Theoretical modeling substantiates the bionic solution of an optimal wave propulsor for water transport, which must have the amplitude and phase characteristics of the fish bending locomotor waves. Use is made of a computer model of multilink chain bending waves where arbitrary distributions can be set for amplitudes and phases of separate segments. With the linear increase in the amplitude of segmental oscillations, a numerical experiment determines the optimal phasing whereby each segment provides a maximal longitudinal component of the motive force. Two versions of hydrodynamic interaction of the segments with water are compared, implying (i) linear and (ii) quadratic drag: the optimal phasing of the transverse and longitudinal oscillations proves to be (i) orthogonal and (ii) nearly orthogonal. The computed bending wave shapes corresponding to dynamic optimization are consistent with the experimental data. 相似文献
144.
145.
To permit epi‐illuminated, high‐resolution optical microscopy of cells in monolayer culture during unperturbed W‐band (75–110 GHz) irradiation, a new class of applicator has been developed based upon WR10 rectangular waveguide components: the cells are normally plated onto the underside of a coverslip which is then placed against the under side of a waveguide flange and receives a roughly circular exposure pattern, with the ±1 dB central spot roughly 1 mm in diameter. Constructed and tested with 94 GHz millimeter waves, water‐immersion optics, and free‐convection cooling, the applicator works robustly and permits SARs at the cell layer as high as 4500 W/kg before the steady‐state temperature rise at the cell layer exceeds 0.5 K. Bioelectromagnetics 31:140–149, 2010. © 2009 Wiley‐Liss, Inc. 相似文献
146.
Latitudinal variation in avian life history strategies is well documented. Clutch size and nest success tend to increase with latitude, whereas longevity and developmental periods have been argued to decrease with latitude. However, these patterns are largely based on interspecific comparisons of species breeding at tropical and temperate latitudes. We compared the life history of Yellow Warblers Setophaga petechia breeding in arctic habitat at the northern extent of their range, in Inuvik, NWT (68°N), Canada, with those breeding in temperate habitat in Revelstoke, BC (50°N), and use data from 21 populations spanning 0–68°N to evaluate latitudinal trends in life history traits from tropical to arctic habitats. Females breeding in Inuvik laid first clutches that were slightly (although not significantly) larger and had higher nest success, which resulted in higher annual productivity compared with their low- latitude counterparts. Apparent adult survival rates were only marginally lower in Inuvik than in Revelstoke, whereas incubation and nestling periods in the arctic were similar to our temperate site. When comparing life history traits across the Yellow Warbler breeding range, we observed increases in clutch sizes and nest success with increasing latitude that appeared to be associated with declines in adult survival, though this relationship was weakened by the addition of our arctic site. We detected more moderate declines in incubation and nestling periods with increasing latitude. As we observed latitudinal variation in some life history traits, but not a consistent transition of traits associated with a shift from a slow to fast life history from tropical to arctic latitudes, our study suggests that the expectation for a general shift in life history traits may be over-simplified. 相似文献
147.
Debabrata?Sarkardebabrata_s@yahoo.com" title="d.sarkar@excite.com debabrata_s@yahoo.com" itemprop="email" data-track="click" data-track-action="Email author" data-track-label="">Email author Suman?K. Pandey A.?Chanemougasoundharam 《Plant Cell, Tissue and Organ Culture》2005,81(2):221-227
The present study investigated the effect of different levels of Ca[ext] (0.3, 3.0, 5.0, 7.0, 9.0 and 11.0 mM) on potato over minimal growth in vitro in relation to varying water stress levels and moisture vapour transmission regimes using 45Ca as an isotopic tracer. Ca nutrition was substantially limited when the microplants were grown at enhanced water stress level (MS + 40 g l-1 sucrose + 20 g l-1 mannitol) under minimal growth. Ca[ext] in excess of standard level (3.0 mM), however, resulted in a significant increase in Ca content in microplants. The differential Ca uptake in microplants in relation to water stress and moisture vapour transmission has been discussed in terms of transpiration stream and root pressure water flow under minimal growth. The study showed that poor microplant quality at standard Ca[ext] over prolonged storage under minimal growth was due to limiting Ca nutrition, and this could be improved by using Ca[ext]-enriched (5.0-7.0 mM) minimal growth medium for conservation of potato microplants. The role of high Ca[ext] in reducing the phenotypic abnormalities such as vitrification, flaccidity, hyperhydricity, etc. in potato microplants over extended storage under minimal growth has also been discussed. 相似文献
148.
Paola Strocchi Jeffrey M. Gilbert Larry I. Benowitz D. Dahl Ellen R. Lewis 《Journal of neurochemistry》1984,43(2):349-357
High resolution 2DGE (two-dimensional gel electrophoresis) was used to characterize neuronal and glial proteins of the rat optic nerve, to examine the phases of intraaxonal transport with which the neuronal proteins are associated, and to identify the ribosomal populations on which these proteins are synthesized. Neuronal proteins synthesized in the retinal ganglion cells were identified by injecting the eye with L-[35S]methionine, followed by 2DGE analysis of fast and slow axonally transported proteins in particulate and soluble fractions. Proteins synthesized by the glial cells were labeled by incubating isolated optic nerves in the presence of L-[35S]methionine and then analyzed by 2DGE. A number of differences were seen between filamentous proteins of neurons and glia. Most strikingly, proteins in the alpha- and beta-tubulin region of the 2D gels of glial proteins were distinctly different than was observed for axonal proteins. As expected, neurons but not glia expressed neurofilament proteins, which appeared among the slow axonally transported proteins in the particulate fraction; significant amounts of the glial filamentous protein, GFA, were also labeled under these conditions, which may have been due to transfer of amino acids from the axon to the glial compartment. The fast axonally transported proteins contained relatively large amounts of high-molecular-weight acidic proteins, two of which were shown to comigrate (on 2DGE) with proteins synthesized by rat CNS rough microsomes; this finding suggests that rough endoplasmic reticulum may be a major site of synthesis for fast transported proteins. In contrast, the free polysome population was shown to synthesize the principal components of slow axonal transport, including tubulin subunits, actin, and neurofilament proteins. 相似文献
149.
Klára Barabás László Zimányi Győző Garab 《Journal of bioenergetics and biomembranes》1985,17(6):349-364
We investigated the flash-induced electrochromic absorbance change, A
515, of isolated intact chloroplasts in continuous monochromatic background light of different intensities and wavelengths. From the variation of the amplitude of A
515 in background illumination the steady-state turnover time of electron transport was found to be around 100 msec and the slowest process could be assigned to a photosystem 1 driven cycle. The change of pH induced by nigericin, ATP, or ADP did not modify substantially the turnover time.In contrast to earlier observations the slow rise (10 msec) of A
515 in untreated chloroplasts persists also at high-intensity background illumination exciting both photosystems. The proportion of the slow rise of A
515 in nigericin-treated chloroplasts increases in the presence of background light. This result on the slow rise is discussed in terms of two different models existing in the literature. 相似文献
150.
目的和方法:本工作旨在研究免迷走复合区(DVC)内TRH对奥迪氏括约肌(SO)肌电的调节作用及外周途径。结果:(1)DVC内注射TRH(0.8nmol,1μl)后,慢波电位(SW)频率不变,但锋电位频率(FSPSO)及幅度(ASPSO)、锋电位发生率(ISP)明显增加.(2)DVC内分别注射不同剂量TRH(0.13,0.25,0.50,0.80,1.30nmol,1μl)后,各剂量TRH均能引起FSPSO增加。随注射剂量的增加,SO反应强度和持续时间均增加,呈现明显的剂量反应关系。(3)DVC内注射TRH兴奋FSPSO的效应可被静脉注射阿托品(0.2mg/kg)或迷走神经切断完全阻断,但不能被静脉注射酚妥拉明(1.5mg/kg)、心得安(1.5mg/kg)或脊髓切断术所阻断。结论:DVC内TRH可能对SO肌电有重要的调节作用,这种作用是通过迷走神经及外周M受体介导。 相似文献