全文获取类型
收费全文 | 386篇 |
免费 | 29篇 |
国内免费 | 1篇 |
出版年
2022年 | 5篇 |
2021年 | 6篇 |
2020年 | 5篇 |
2019年 | 3篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 7篇 |
2015年 | 17篇 |
2014年 | 14篇 |
2013年 | 19篇 |
2012年 | 15篇 |
2011年 | 15篇 |
2010年 | 8篇 |
2009年 | 9篇 |
2008年 | 22篇 |
2007年 | 16篇 |
2006年 | 13篇 |
2005年 | 12篇 |
2004年 | 15篇 |
2003年 | 17篇 |
2002年 | 6篇 |
2001年 | 12篇 |
2000年 | 12篇 |
1999年 | 13篇 |
1998年 | 6篇 |
1997年 | 3篇 |
1996年 | 10篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 11篇 |
1990年 | 12篇 |
1989年 | 12篇 |
1988年 | 6篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1985年 | 13篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 5篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
排序方式: 共有416条查询结果,搜索用时 140 毫秒
61.
Krens SF He S Lamers GE Meijer AH Bakkers J Schmidt T Spaink HP Snaar-Jagalska BE 《Developmental biology》2008,319(2):370-383
The MAPKs are key regulatory signaling molecules in many cellular processes. Here we define differential functions for ERK1 and ERK2 MAPKs in zebrafish embryogenesis. Morpholino knockdown of ERK1 and ERK2 resulted in cell migration defects during gastrulation, which could be rescued by co-injection of the corresponding mRNA. Strikingly, Erk2 mRNA cross-rescued ERK1 knockdown, but erk1 mRNA was unable to compensate for ERK2 knockdown. Cell-tracing experiments revealed a convergence defect for ERK1 morphants without a severe posterior-extension defect, whereas ERK2 morphants showed a more severe reduction in anterior-posterior extension. These defects were primary changes in gastrulation cell movements and not caused by altered cell fate specification. Saturating knockdown conditions showed that the absence of FGF-mediated dual-phosphorylated ERK2 from the blastula margin blocked initiation of epiboly, actin and tubulin cytoskeleton reorganization processes and further arrested embryogenesis, whereas ERK1 knockdown had only a mild effect on epiboly progression. Together, our data define distinct roles for ERK1 and ERK2 in developmental cell migration processes during zebrafish embryogenesis. 相似文献
62.
de Beer VJ Sorop O Pijnappels DA Dekkers DH Boomsma F Lamers JM Duncker DJ Merkus D 《American journal of physiology. Heart and circulatory physiology》2008,294(5):H2069-H2077
Several studies have indicated an interaction between the renin-angiotensin (ANG II) system and endothelin (ET) in the regulation of vascular tone. Previously, we have shown that both ET and ANG II exert a vasoconstrictor influence on the coronary resistance vessels of awake normal swine. Here, we investigated whether the interaction between ANG II and ET exists in the control of coronary resistance vessel tone at rest and during exercise using single and combined blockade of angiotensin type 1 (AT(1)) and ET(A)/ET(B) receptors. Since both circulating ANG II and ET levels are increased after myocardial infarction (MI), we investigated if the interaction between these systems is altered after MI. In awake healthy swine, coronary vasodilation in response to ET(A)/ET(B) receptor blockade in the presence of AT(1) blockade was similar to vasodilation produced by ET(A)/ET(B) blockade under control conditions. In awake swine with a 2- to 3-wk-old MI, coronary vasodilator responses to individual AT(1) and ET(A)/ET(B) receptor blockade were virtually abolished, despite similar coronary arteriolar AT(1) and ET(A) receptor expression compared with normal swine. Unexpectedly, in the presence of AT(1) blockade (which had no effect on circulating ET levels), ET(A)/ET(B) receptor blockade elicited a coronary vasodilator response. These findings suggest that in normal healthy swine the two vasoconstrictor systems contribute to coronary resistance vessel control in a linear additive manner, i.e., with negligible cross-talk. In contrast, in the remodeled myocardium, cross-talk between ANG II and ET emerges, resulting in nonlinear redundant control of coronary resistance vessel tone. 相似文献
63.
Hilde B.M. Tomassen Alfons J.P. Smolders Leon P.M. Lamers Jan G.M. Roelofs 《Biogeochemistry》2004,71(1):69-87
The usual method of restoring cut-over bogs is to rewet the peat surface, but this often leads to the remaining peat layers being deeply inundated. For Sphagnum-dominated vegetation to develop at deeply inundated locations, it is important for floating rafts of buoyant residual peat to develop. In this study, the chemical and physical characteristics of buoyant and inundated peat collected from rewetted cut-over bog were compared. In general, buoyant peat was poorly humified; high methane (CH4) production rates (≥2?µmol?g?1?DW?day?1) were important to ensure buoyancy. Although the peat water CH4 concentrations increased with depth, the CH4 production rates were higher in the uppermost peat layers. High CH4 production rates were related positively with P concentrations and negatively with lignin concentrations. The pH to bulk density ratio (≥0.05) also appeared to be a good indicator of CH4 production rates, providing an easy and cheap way to measure the variable for restoration practitioners. Our results indicated that analysing certain simple characteristics of the residual peat can greatly improve the success of the rewetting measures taken in cut-over bogs. If the analysis reveals that the residual peat is unsuitable for floating raft formation, deep inundation is inappropriate unless suitable peat from other locations can be introduced. 相似文献
64.
65.
Antoine P. M. Lamers Albert A. J. Verhofstad Ad M. Stadhouders Andrew M. Michelakis 《Cell and tissue research》1985,239(3):677-682
Summary The cellular localization of renin was examined in the kidneys of some amphibians of the genus Bufo by immunoperoxidase and immunofluorescence techniques with an antiserum to renin isolated from the submandibular gland of the mouse. Immunoreactivity could be demonstrated in the media cells of the afferent arterioles (juxtaglomerular cells) close to as well as at great distance from the glomeruli. Occasionally, media cells of larger arterial vessels were also stained. The immunohistochemical data seem to be in accordance with earlier results obtained with a modified silver impregnation technique (Movat's staining procedure) used for the visualization of juxtaglomerular cells in non-mammalian vertebrates. Mouse kidney tissue, studied for purposes of comparison, showed renin-immunoreactivity as described by earlier investigators, i.e., immunoreactive staining in the afferent arterioles near the glomeruli and in the proximal tubule cells. 相似文献
66.
67.
R. Gebhardt R. Jirtle A. F. M. Moorman W. H. Lamers G. Michalopoulos 《Histochemistry and cell biology》1989,92(4):337-342
Summary Isolated rat hepatocytes were transplanted into the interscapular and both anterior lateral fat pads of hepatectomized syngeneic rats. At various time points following transplantation, the fat pads were removed, fixed and embedded in paraffin. Serial sections were stained for glutamine synthetase (GS) and carbamoylphosphate synthetase (CPS) using specific antisera and the PAP technique. The initially low fraction of GS+-heptatocytes remained low up to the fourth day, then increased strikingly up to almost 100% and declined gradually after the 14th day. In contrast, the number of CPS+-cells declined continuously to about 30% after 28 days. If the animals were exposed to CCl4 prior to the isolation of the hepatocytes in order to reduce the number of GS+-cells in the initial cell suspension similar results were obtained and no difference in the probability of the colony formation was noted between this and the normal hepatocyte suspensions indicating that the appearance of the GS+-phenotype was not due to a selective survival of these cells. Analysis of the staining intensity of the transplanted hepatocytes revealed the appearance of two populations of GS+-hepatocytes, one with a strong and one with a weak staining, during the course of formation of larger nodules, while only a single weakly stained population could be discerned with respect to the staining for CPS. These results demonstrate that all hepatocytes or at least their descendents can be induced to express GS by the environmental conditions of the fat pads, and that GS and CPS can be co-expressed with an apparently reciprocal relationship. 相似文献
68.
1. A technique is described for the rapid separation of intestinal epithelial cells from the incubation medium by passage through a silicon-oil layer and collection in acid, in which their soluble constituents are released. 2. The inhibition by fatty acids of pyruvate oxidation is further studied. Measurement of pyruvate transport in epithelial cells at 0 degree C showed that short- and medium-chain fatty acids as well as ricinoleate inhibit this transport. Propionate inhibits pyruvate transport by another mechanism than octanoate. 3. Differences between pyruvate propionate and octanoate transport across the epithelial cell membrane were obtained in efflux studies. These studies revealed that acetate, propionate, butyrate and high concentrations of bicarbonate readily stimulate the efflux of pyruvate, probably by anionic counter-transport. No effects were seen with octanoate and hexanoate. The data obtained in these efflux studies suggest that lipophilicity and the pKa values of the monocarboxylic acids determine the contribution of non-ionic diffusion to overall transport. 4. Saturation kinetics, competitive inhibition by short-chain fatty acids and counter-transport suggest a carrier-mediated transport of pyruvate. 相似文献
69.
It is well known that surface mulched crop residues (CR) lead to large yield increases of pearl millet (Pennisetum glaucum
L.) on acid sandy soils of the West African Sahel. This effect is generally attributed to mulch-induced changes in chemical
properties of the surface soil and the protection of millet seedlings from erosive sand storms. However, previous research
has failed to separate the anti-erosive effects of CR on plant growth from chemical effects due to the release of nutrients
during CR decomposition. To this end a mulching trial with surface applied millet stalks at a rate of 2000 kg ha-1, an equivalent 10% surface coverage obtained by inert polyethylene (PE) tubes and a bare control treatment was conducted
from 1992 to 1994 on an acid sandy soil in southwest Niger. Across treatments, sand flux at 0.1 m height was more than twice
as high in the rainy seasons than in the dry months and mulching reduced sand flux by between 25 and 50% during rainy season
storms compared with 67% during the dry season. Over the 21 months measurement period, cumulative erosion by wind and water
was almost 270 t ha-1 of soil in unmulched control plots. In mulched plots, in contrast, between 160 and 200 t ha-1 of soil was deposited. Surface soil temperature at 0.01 m depth reached above 40 °C in bare plots but was up to 4 °C lower
with CR. Mulch reduced soil penetration resistance at 0–0.02 m and 0–0.05 depth by more than half and decreased runoff leading
to higher water contents at flowering and grain filling in the upper 0.3 m soil layers in 1993 and throughout the entire profile
in 1994, a year with particularly high rainfall. Both mulch types were similarly effective in increasing final stand density
of millet in the first two years between 5 and 23% compared with bare control plots. Relative to the bare control CR mulch
effects on total dry matter of millet at harvest increased from 35% in 1992 and 108% in 1993 to 283% in 1994, whereas PE mulch
led to respective relative increases in dry matter of only 6, 44 and 13%. In 1992 and 1993, CR mulch increased total nutrient
uptake of millet at harvest by between 34 and 86% for nitrogen (N), between 31 and 162% for P and between 56 and 126% for
potassium (K). These differences were mostly the result of differences in total dry matter and only to a smaller part due
to changed nutrient concentrations in plants.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
70.