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   142篇
  免费   24篇
  166篇
  2021年   2篇
  2017年   2篇
  2015年   3篇
  2014年   3篇
  2013年   25篇
  2011年   5篇
  2010年   2篇
  2009年   6篇
  2008年   3篇
  2007年   3篇
  2006年   2篇
  2005年   9篇
  2004年   3篇
  2003年   2篇
  2002年   3篇
  1999年   2篇
  1998年   2篇
  1997年   2篇
  1996年   5篇
  1994年   2篇
  1992年   2篇
  1989年   2篇
  1987年   2篇
  1986年   6篇
  1985年   5篇
  1982年   3篇
  1981年   2篇
  1980年   3篇
  1979年   2篇
  1978年   2篇
  1975年   3篇
  1915年   2篇
  1914年   1篇
  1909年   1篇
  1902年   1篇
  1901年   1篇
  1897年   2篇
  1892年   1篇
  1891年   1篇
  1889年   1篇
  1888年   1篇
  1887年   1篇
  1883年   3篇
  1882年   5篇
  1881年   2篇
  1880年   1篇
  1879年   6篇
  1878年   2篇
  1877年   2篇
  1876年   1篇
排序方式: 共有166条查询结果,搜索用时 7 毫秒
91.
92.
Although home-based care (HBC) programs are widely implemented throughout Africa, their success depends on the existence of an enabling environment, including a referral system and supply of essential commodities. The objective of this study was to explore the current state of client referral patterns and practices by community care workers (CCWs), in an evolving environment of one rural South African sub-district. Using a participant triangulation approach, in-depth qualitative interviews were conducted with 17 CCWs, 32 HBC clients and 32 primary caregivers (PCGs). An open-ended interview guide was used for data collection. Participants were selected from comprehensive lists of CCWs and their clients, using a diversified criterion-based sampling method. Three independent researchers coded three sets of data – CCWs, Clients and PCGs, for referral patterns and practices of CCWs. Referrals from clinics and hospitals to HBC occurred infrequently, as only eight (25%) of the 32 clients interviewed were formally referred. Community care workers showed high levels of commitment and personal investment in supporting their clients to use the formal health care system. They went to the extent of using their own personal resources. Seven CCWs used their own money to ensure client access to clinics, and eight gave their own food to ensure treatment adherence. Community care workers are essential in linking clients to clinics and hospitals and to promote the appropriate use of medical services, although this effort frequently necessitated consumption of their own personal resources. Therefore, risk protection strategies are urgently needed so as to ensure sustainability of the current work performed by HBC organizations and the CCW volunteers.  相似文献   
93.
94.
Background: Estuaries are characterised by salinity gradients and regular flooding events. These environmental factors form stress gradients, along which species composition changes.

Aims: Analyse and compare patterns of plant species diversity along the estuarine salinity and flooding gradients of the Elbe and Connecticut Rivers.

Methods: Vegetation was sampled at three elevations (low, mid, high) in five sites of each marsh type (fresh, brackish, salt) in both estuaries. Patterns of species density (SD) and evenness (E) along the gradients were analysed and compared between the two estuaries with three-factor ANOVAs.

Results: The regional species pool was 33% higher for the Connecticut than for the Elbe. SD of fresh marshes (19 ± 2.2) was more than twice in the Connecticut than in the Elbe. We found an overall increase in SD from low to high elevation and from salt to freshwater marshes in both estuaries. However, SD and E were strongly depressed at intermediate elevations in the Elbe fresh and brackish marshes.

Conclusions: Although diversity patterns in the two estuaries show overall similarities, patterns of SD and E differ, when particular elevational zones and marsh types are compared. We hypothesise this to be due to evolutionary and historical influences on the regional species pools, shaping the impact of local biotic and abiotic processes.  相似文献   
95.
96.
97.
Summary The purpose of this study was to determine whether the plant lectin,Dolichos biflorus agglutinin (DBA), can be used to recognize capillary endothelial cells and their processes during angiogenesis. By means of a peroxidase conjugate of DBA, blood vessels were visualized in whole mounts and ultrathin sections of mouse omentum. A part of this mesentery normally comprises an avascular membrane that is approximately 30 µm in thickness. Changes in the vascular plexus bordering this membrane were induced by intraperitoneal injection of irradiated Landschutz cells. Vascular endothelial cells were precisely and intensely stained, and vasculogenic processes were reliably distinguished from those of other cells. This technique permitted observation of the structure and distribution of capillary sprouts, and their relationship to each other and to pre-existing blood vessels. It was discovered that filiform projections extend from sprout apices. These projections may fuse allowing adjacent sprouts to form a new capillary loop.  相似文献   
98.
New, except 1d, melatonin analogue benzimidazole derivatives were synthesized and characterized in the present study. The potential role of melatonin as an antioxidant by scavenging and detoxifying ROS raised the possibility that compounds that are analogous to melatonin can also be used for their antioxidant properties. Therefore the antioxidant effects of the newly synthesized compounds were investigated in vitro by means of their inhibitory effect on hydrogen peroxide-induced erythrocyte membrane lipid peroxidation (EMLP) and on various erythrocyte antioxidant enzymes viz. superoxide dismutase (SOD), catalase (CAT) and glucose-6-phosphate dehydrogenase (G6PD). The synthesized benzimidazole derivatives showed remarkable antioxidant activity in vitro in the H2O2-induced EMLP system. Furthermore their effects on various antioxidant enzymes are discussed and evaluated from the perspective of structure- activity relationships.  相似文献   
99.
100.
The Pecten, considered from an Environmental Point of View.   总被引:1,自引:0,他引:1  
Arthur  Thoyson F.R.C.R.  LL.D.  D.C.L. 《Ibis》1929,71(4):608-639
  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