全文获取类型
收费全文 | 259篇 |
免费 | 15篇 |
出版年
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 8篇 |
2014年 | 7篇 |
2013年 | 4篇 |
2012年 | 13篇 |
2011年 | 14篇 |
2010年 | 9篇 |
2009年 | 5篇 |
2008年 | 9篇 |
2007年 | 17篇 |
2006年 | 11篇 |
2005年 | 10篇 |
2004年 | 14篇 |
2003年 | 7篇 |
2002年 | 9篇 |
2001年 | 7篇 |
2000年 | 9篇 |
1999年 | 10篇 |
1998年 | 11篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 7篇 |
1992年 | 4篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 6篇 |
1971年 | 3篇 |
1970年 | 4篇 |
1969年 | 1篇 |
排序方式: 共有274条查询结果,搜索用时 187 毫秒
1.
Fluid-phase interactions between hematologic cells and those of the vessel wall were studied in order to define a role for lipoxygenase products as cell signals in the control of vascular cholesterol metabolism. A functional parameter for hydroxy acids in this system has not been previously demonstrated. We report herein for the first time a biochemical effect of lipoxygenase-derived eicosanoids in the modulation of cholesterol metabolism in smooth muscle cells. Products of platelet-neutrophil interactions served as cell signals in vitro to modulate cholesterol metabolism. We demonstrate that 12-HETE, 12,20-DiHETE, and 12-HETE-1,20-dioic acid activate both lysosomal and cytoplasmic cholesteryl ester (CE) hydrolytic activities, although no effect was observed on CE synthetic (ACAT) activity. The platelet lipoxygenase product, 12-HETE, was the most effective stimulator of CE hydrolysis in the smooth muscle cell, and its conversion to 12,20-DiHETE and the dioic acid derivative by the neutrophils was not necessary for the activation of CE hydrolase. A 2-fold enhancement on CE hydrolysis occurred and was independent of any "cross-activation" by hydroxy acids on production of cyclooxygenase or other lipoxygenase products. The activation of cytoplasmic CE hydrolysis had a lesser cofactor dependence on bile salts in the presence of 12-HETE. This suggested a reduced requirement for surface-active agents in an enzyme-substrate interaction where enzymes are hydrolyzing insoluble lipid substrates. Moreover, 12-HETE induced an additive effect with several lipolytic hormones in the activation of CE catabolism.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
2.
L Staiano-Coico D P Hajjar J M Hefton K A Hajjar M Kimmel 《Journal of cellular physiology》1988,134(3):485-490
Arterial endothelial cells (EC) or their conditioned medium (ECCM) can alter the proliferation of cocultured arterial smooth muscle cells (SMC). Previously, we have shown, as have others, that EC regulate the growth of cocultured SMC depending on the density of both cell types. To ascertain the rate of cell-cycle traverse in preconfluent arterial SMC cocultured with arterial EC or ECCM (derived from preconfluent EC), we have conducted a series of stathmokinetic experiments using flow cytometry to determine where specific changes may occur in the cell cycle. Results of our experiments indicate for the first time that ECCM stimulates the proliferation of preconfluent SMC by significantly shortening the residence times in the G1 and S phases of the cell cycle. The predominant relative effect occurs within the early G1 (G1A) compartment where pretreatment with ECCM shortens the residence time by approximately 55%. Furthermore, we have observed that preincubation of serum-free ECCM with antiplatelet-derived growth factor (PDGF) antibody abolishes any mitogenic effect on SMC. This suggests that EC secrete PDGF-like molecules which enhance the proliferation rate of preconfluent, cocultured SMC. These findings support the hypothesis that arterial EC may secrete mitogens which stimulate arterial SMC proliferation in the vascular wall. 相似文献
3.
A M Hajjar R F DiGiacomo J K Carpenter S A Bingel T C Moazed 《Laboratory animal science》1991,41(1):22-25
Sialodacryoadenitis virus (SDAV) was detected in athymic rats subcutaneously implanted with human tumor cell lines. Clinical signs included sneezing, dyspnea, weight loss and death. Necropsy revealed both upper and lower respiratory tract disease from which Staphylococcus aureus, Pasteurella pneumotropica and Pseudomonas aeruginosa were recovered. Histopathological changes consisted of suppurative rhinitis and bronchopneumonia. Lesions characteristic of SDAV infection were found in lacrimal and salivary glands, and viral antigens were detected in the salivary glands and respiratory tract by immunohistochemistry. Submaxillary salivary gland. Harderian gland and lung homogenates from affected athymic rats were inoculated intranasally into euthymic rats as a rat antibody production test. All euthymic rats seroconverted to SDAV. Seroconversion to SDAV was demonstrated in consecutive pairs of sentinel euthymic rats housed for 6 months with infected athymic rats. Inoculation of supernatants of the original tumor cell lines into euthymic rats did not result in seroconversion. The source of the virus was not determined. In this study, spontaneously acquired SDAV infection persisted for at least 6 months in athymic rats. 相似文献
4.
Trimethyloxonium modification of single batrachotoxin-activated sodium channels in planar bilayers. Changes in unit conductance and in block by saxitoxin and calcium 总被引:13,自引:9,他引:4
下载免费PDF全文
![点击此处可从《The Journal of general physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Single batrachotoxin-activated sodium channels from rat brain were modified by trimethyloxonium (TMO) after incorporation in planar lipid bilayers. TMO modification eliminated saxitoxin (STX) sensitivity, reduced the single channel conductance by 37%, and reduced calcium block of inward sodium currents. These effects always occurred concomitantly, in an all-or-none fashion. Calcium and STX protected sodium channels from TMO modification with potencies similar to their affinities for block. Calcium inhibited STX binding to rat brain membrane vesicles and relieved toxin block of channels in bilayers, apparently by competing with STX for the toxin binding site. These results suggest that toxins, permeant cations, and blocking cations can interact with a common site on the sodium channel near the extracellular surface. It is likely that permeant cations transiently bind to this superficial site, as the first of several steps in passing inward through the channel. 相似文献
5.
Metabolic activity of cholesteryl esters in aortic smooth muscle cells is altered by prostaglandins I2 and E2 总被引:7,自引:0,他引:7
Among the biochemical processes associated with the atherogenic process are increased aortic cholesteryl ester (CE) accumulation and altered prostaglandin (PG) production. The precise physiological role of PG, particularly prostacyclin (PGI2), in the control of CE metabolism in intact aortic smooth muscle cells remains to be fully elucidated. We report here that cytosolic neutral cholesteryl ester hydrolytic activity (NCEH) in intact cultured aortic smooth muscle cells is significantly increased by 75-250 nM PGI2 at the end of a 2-hr incubation period. The effect was mediated by increased intracellular cAMP levels since the effect of PGI2 on NCEH activity was abolished in the presence of an inhibitor of adenylate cyclase activity, viz., dideoxyadenosine (DDA0. Although the addition of 20-100 microM dibutyryl cAMP (Bt2cAMP) and 50-100 microM sodium arachidonate also increased NCEH activity twofold, 6-keto PGF1 alpha, PGE1, and PGE2 did not increase the activity of this enzyme. In contrast to these findings, 75-250 nM PGE2 significantly inhibited CE synthetic activity (ACAT) approximately 60%. Arachidonate or Bt2cAMP did not affect ACAT activity. This decrease in ACAT activity induced by PGE2 does not appear to be mediated by cAMP. Taken together, these findings suggest that PGI2, a well known potent vasodilator and inhibitor of platelet aggregation, and PGE2 may have an important regulatory role in aortic CE metabolism. 相似文献
6.
Viral activation of the coagulation cascade: molecular interactions at the surface of infected endothelial cells 总被引:10,自引:0,他引:10
Herpesviral infection of endothelial cells (ECs) induces arterial injury. We now demonstrate that such infection promoted enhanced monocyte-endothelial adhesion. Enhanced adhesion was blocked by monoclonal antibodies to the viral-encoded cell surface glycoprotein gC but not by antibodies to gD or gE. Adhesion was also blocked by treating ECs with specific thrombin inhibitors or by growing cells in prothrombin-depleted serum. We found that gC bound and promoted activation of factor X on infected ECs, thereby contributing to thrombin generation. Factor X also bound to transfected L cells that were induced to express gC. Cross-linking and immunoprecipitation studies demonstrated factor X-gC complex formation on the surface of these cells. We suggest that gC-dependent thrombin generation by herpes-infected endothelium may be an important mediator of vascular pathology during viral infection. 相似文献
7.
Relative apparent synapomorphy analysis (RASA). I: The statistical measurement of phylogenetic signal 总被引:10,自引:9,他引:1
We have developed a new approach to the measurement of phylogenetic signal
in character state matrices called relative apparent synapomorphy analysis
(RASA). RASA provides a deterministic, statistical measure of natural
cladistic hierarchy (phylogenetic signal) in character state matrices. The
method works by determining whether a measure of the rate of increase of
cladistic similarity among pairs of taxa as a function of phenetic
similarity is greater than a null equiprobable rate of increase. Our
investigation of the utility and limitations of RASA using simulated and
bacteriophage T7 data sets indicates that the method has numerous
advantages over existing measures of signal. A first advantage is
computational efficiency. A second advantage is that RASA employs known
methods of statistical inference, providing measurable sensitivity and
power. The performance of RASA is examined under various conditions of
branching evolution as the number of characters, character states per
character, and mutations per branch length are varied. RASA appears to
provide an unbiased and reliable measure of phylogenetic signal, and the
general approach promises to be useful in the development of new techniques
that should increase the rigor and reliability of phylogenetic estimates.
相似文献
8.
9.
Variation in heat-shock proteins among species of desert fishes (Poeciliidae, Poeciliopsis) 总被引:4,自引:0,他引:4
Analysis of the heat-shock proteins (hsps) of six closely related species
of Poeciliopsis demonstrated the existence of biochemical diversity in the
hsp100, hsp70, hsp60, and hsp30 protein families among species. Each
species expressed five to seven hsp70-related isoforms. Constitutive 70-kD
isoforms were identical among species, but four different patterns of
heat-inducible isoforms were seen in these six species. Members of the
hsp70 family of molecular chaperones are included among the most highly
conserved proteins known, and the possibility of variation in hsp70 among
closely related species has rarely been addressed. The hsp30 family is
known to be less conserved than the hsp70 family, and, as expected, the
Poeciliopsis hsp30 patterns showed more variation. Most of the hsp30
isoforms characteristic of a particular species were unique to that
species. Hsp100 and hsp60 were identical in five of the species, but
alternate isoforms were found in P. monacha. The small size and limited
geographical distribution of the P. monacha population have probably
contributed to the uniqueness of the monacha pattern. Two of the species
were shown to acquire thermotolerance, the ability to withstand normally
lethal temperatures when subjected to a gradual temperature increase.
Rapid-heating protocols commonly used to establish critical thermal maxima
of organisms do not include this inducible component of thermoresistance
and therefore do not adequately assess an organism's capacity to withstand
thermal stress.
相似文献
10.