首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   260篇
  免费   22篇
  2021年   6篇
  2019年   4篇
  2018年   4篇
  2016年   2篇
  2015年   8篇
  2014年   5篇
  2013年   16篇
  2012年   18篇
  2011年   14篇
  2010年   6篇
  2009年   8篇
  2008年   8篇
  2007年   10篇
  2006年   7篇
  2005年   19篇
  2004年   14篇
  2003年   11篇
  2002年   8篇
  2001年   2篇
  2000年   3篇
  1999年   2篇
  1998年   3篇
  1996年   3篇
  1993年   2篇
  1992年   4篇
  1991年   3篇
  1990年   3篇
  1989年   3篇
  1988年   5篇
  1986年   6篇
  1985年   4篇
  1984年   6篇
  1983年   4篇
  1981年   3篇
  1980年   6篇
  1979年   2篇
  1978年   2篇
  1975年   2篇
  1974年   4篇
  1973年   2篇
  1972年   2篇
  1971年   2篇
  1970年   2篇
  1938年   3篇
  1934年   2篇
  1928年   2篇
  1921年   2篇
  1919年   2篇
  1918年   2篇
  1916年   4篇
排序方式: 共有282条查询结果,搜索用时 15 毫秒
1.
We undertook a 2-year (2002–2004) mark–recapture study to investigate demographic performance and habitat use of salt marsh harvest mice (Reithrodontomys raviventris halicoetes) in the Suisun Marsh. We examined the effects of different wetland types and microhabitats on 3 demographic variables: density, reproductive potential, and persistence. Our results indicate that microhabitats dominated by mixed vegetation or pickleweed (Salicornia spp.) supported similar salt marsh harvest mouse densities, reproductive potential, and persistence throughout much of the year, whereas few salt marsh harvest mice inhabited upland grass-dominated microhabitats. We found that densities were higher in diked wetlands, whereas post-winter persistence was higher in tidal wetlands, and reproductive potential did not differ statistically between wetland types. Our results emphasize the importance of mixed vegetation for providing adequate salt marsh harvest mouse habitat and suggest that, despite their physiognomic and hydrological differences, both diked and tidal wetlands support salt marsh harvest mouse populations by promoting different demographic attributes. We recommend that habitat management, restoration, and enhancement efforts include areas containing mixed vegetation in addition to pickleweed in both diked and tidal wetlands. © 2011 The Wildlife Society.  相似文献   
2.
Primary cultures of endometrial glands and stromal cells were labelled with [14C]-arachidonic acid for 4 h before exposure to either the calcium ionophore, A23187 (which activates phospholipase A2 (PLA2) by increasing intracellular calcium concentrations) or sodium fluoride (which activates a G-protein). Calcium ionophore (0.5-50 mumol/l) stimulated a dose- and time-dependent release of arachidonic acid from endometrial glands. Incubation with ionophore (10 mumol/l) for 1 h released 22% of the incorporated arachidonic acid. There was a corresponding decrease in phospholipids and no loss from triglycerides. Stromal cells were unresponsive to ionophore. Fluoride (10 mmol/l) stimulated a release of arachidonic acid from stromal cells and endometrial glands (6.5% of the total arachidonic acid incorporated). In stromal cells, arachidonic acid was released from triglycerides in Day-1 cultures and from phospholipids in Day-2 cultures. In both Day-1 and Day-2 cultures of endometrial glands, arachidonic acid was released from phospholipids, but not from triglycerides. Among the phospholipids, phosphatidylcholine was always the major source of arachidonic acid. Arachidonic acid release from endometrial glands and stromal cells may be mediated by activation of PLA2 (or phospholipase C) via a G-protein, but in glands calcium ionophore may have a direct effect on PLA2. The response to calcium ionophore may reflect the differences in calcium requirements of the two endometrial PLA2 isoenzymes.  相似文献   
3.
4.
TISACID (a new, modern Hungarian Al-containing antacid) with a high acid-neutralizing capacity (greater than 26.8 mmol/g) also enhances gastric mucosal defense mechanisms (prostaglandin-dependent gastroprotection). A simple-blind, prospective, randomized, parallel multicentre clinical trial has been performed on both the clinical efficacy and possible side effects of TISACID monotherapy (Al-Mg-hydroxy-carbonate) on informed patients suffering from active duodenal ulcers. The study groups were as follows: Group "A": 3 g/day of TISACID (acid-neutralizing capacity = 78 mmol, n = 85), Group "B": 6 g/day of TISACID (acid-neutralizing capacity = 156 mmol, n = 88), Group "C": 12 g/day of TISACID (acid-neutralizing capacity = 312 mmol, n = 68), Group "D": (as control): (1.0 g/day cimetidine (HISTODIL, RGH, Budapest, n = 91). The total number of patients: 332. It was found that: 1. The new Hungarian antacid compound (both tablet and suspension) can essentially accelerate the healing rate of duodenal ulcers. 2. The cumulative healing rate of ulcers and the decrease of complaints can be achieved equally by relatively low doses of TISACID monotherapy and cimetidine alone. 3. There were no differences between the clinical potency and side-effects of TISACID tablet and suspension.  相似文献   
5.
6.
Combined linkage and segregation analysis using regressive models.   总被引:14,自引:12,他引:2       下载免费PDF全文
Regressive models for segregation analysis have been extended to include multivariate data and linked marker loci. The new models have been applied to data from two pedigrees segregating a gene for cardiovascular disease.  相似文献   
7.
Resident mouse peritoneal macrophages when exposed to zymosan during the first day of cell culture synthesize and secrete large amounts of prostaglandin E2 (PGE2) and leukotriene C4 (LTC4), the respective products of cyclo-oxygenase- and 5-lipoxygenase-catalysed oxygenations of arachidonic acid. Under these conditions of cell stimulation only small amounts of hydroxyeicosatetraenoic acids (HETEs) are concomitantly produced. However, exogenously added arachidonic acid is metabolized to large amounts of 12- and 15-HETE and only relatively small amounts of PGE2. No LTC4 is formed under these conditions. In contrast, resident mouse peritoneal macrophages in cell culture for 4 days synthesized less PGE2 and LTC4 when exposed to zymosan. However, these macrophage populations continue to synthesize 12-HETE from exogenously added arachidonic acid. Zymosan induced the secretion of a lysosomal enzyme, N-acetyl-beta-glucosaminidase, equally in both 1- and 4-day cultures. Both 12- and 15-hydroperoxyeicosatetraenoic acids (HPETEs), the precursors of 12- and 15-HETE, were found to be irreversible inhibitors of the cyclo-oxygenase pathway and reversible inhibitors of the 5-lipoxygenase pathway in macrophages. 15-HETE were found to be reversible inhibitors of both pathways. Thus the oxidation of arachidonic oxidation of arachidonic acid to both prostaglandins and leukotrienes may be under intracellular regulation by products of 12- and 15-lipoxygenases.  相似文献   
8.
The gastric cytoprotective effects of vitamin A, De-Nol and sucralfate were compared with the effectiveness of pirenzepine in healing ulcer in patients with chronic gastric ulcer. A total of 100 patients was randomized into different groups: the patients were treated with antacids, vitamin A (3 X 50.000 IU), De-Nol liquid (4 X 5 ml), sucralfate (4 X 1 g) or pirenzepine (3 X 50 mg). The treatment was continued for 4 weeks. At the beginning, 2 and 4 weeks after starting treatment the patients were subjected to endoscopy and the size of the ulcer was measured planimetrically. The ulcer-healing effect of De-Nol liquid was significantly better than that of the antacids (p less than 0.01). Ulcer size was reduced significantly in all groups (p less than 0.01), however, at the end of the study the gastric ulcers were smallest in the De-Nol treated group (p less than 0.001). The dynamics of ulcer healing in the second week was most favourable in the patients receiving vitamin A (p less than 0.01). The present data point to the cytoprotective effects of De-Nol liquid, vitamin A and sucralfate and to their ability of healing chronic gastric ulcers.  相似文献   
9.
The effects of cimetidine (12.5 mg i.m.) and atropine (0.125 mg i.m.) were studied on the basal (BAO) and pentagastrin (6 micrograms X kg-1 s.c.)-stimulated (MAO) gastric acid secretion; the gastric mucosal microbleeding provoked by one-day treatment with indomethacin (4 X 25 mg orally) in patients with chronic disorders of the joints. The extent of the gastric microbleeding was measured by spectrophotometric determination of haemoglobin in gastric lavage fluid. The aims of this study were to determine the doses of cimetidine and atropine in humans without any significant inhibitory effects either on the basal or on the maximal gastric acid output to evaluate the cytoprotective action of these doses of cimetidine and atropine on the indomethacin-induced gastric microbleeding in the man. It was found that cimetidine (12.5 mg i.m.) and atropine (0.125 mg i.m.) did not cause any significant inhibition either of the BAO or of the MAO; indomethacin (4 X 25 mg orally) significantly increased gastric microbleeding in the patients; cimetidine and atropine, in the above doses, were able to prevent significantly indomethacin-induced gastric microbleeding in the patients. These results provide evidence for the existence of gastric cytoprotective effects of cimetidine and atropine in humans.  相似文献   
10.
The interaction of phorbol myristate acetate with resident populations of mouse peritoneal macrophages causes an increased release of arachidonic acid followed by increased synthesis and secretion of prostaglandin E2 and 6-keto-prostaglandin F1 alpha. In addition, phorbol myristate acetate causes the selective release of lysosomal acid hydrolases from resident and elicited macrophages. These effects of phorbol myristate acetate on macrophages do not cause lactate dehydrogenase to leak into the culture media. The phorbol myristate acetate-induced release of arachidonic acid and increased synthesis and secretion of prostaglandins by macrophages can be inhibited by RNA and protein synthesis inhibitors, whereas the release of lysosomal hydrolases is unaffected. 0.1 microgram/ml actinomycin D blocked the increased prostaglandin production due to this inflammatory agent by more than 80%, and 3 microgram/ml cycloheximide blocked prostaglandin production by 78%. Similar results with these metabolic inhibitors were found with another stimulator of prostaglandin production, zymosan. However, these inhibitors do not interfere with lysosomal hydrolase releases caused by zymosan or phorbol myristate acetate. It appears that one of the results of the interaction of macrophages with inflammatory stimuli is the synthesis of a rapidly turning-over protein which regulates the production of prostaglandins. It is also clear that the secretion of prostaglandins and lysosomal hydrolases are independently regulated.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号