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   296篇
  免费   18篇
  2022年   3篇
  2021年   6篇
  2020年   5篇
  2019年   1篇
  2018年   3篇
  2017年   3篇
  2016年   10篇
  2015年   12篇
  2014年   20篇
  2013年   17篇
  2012年   19篇
  2011年   15篇
  2010年   18篇
  2009年   11篇
  2008年   13篇
  2007年   22篇
  2006年   10篇
  2005年   10篇
  2004年   16篇
  2003年   22篇
  2002年   17篇
  2001年   3篇
  2000年   9篇
  1999年   7篇
  1998年   4篇
  1997年   4篇
  1996年   4篇
  1995年   6篇
  1994年   6篇
  1993年   5篇
  1992年   2篇
  1988年   2篇
  1986年   1篇
  1983年   2篇
  1981年   1篇
  1980年   3篇
  1972年   1篇
  1971年   1篇
排序方式: 共有314条查询结果,搜索用时 31 毫秒
101.
Muehlenbeckia hastulata (J. E.Sm.) Johnst. used mainly for its abortive properties was found active for oxytoxic and analgesic activities in a biological activity screening (oxytoxic, analgesic, antimicrobial, cytotoxic and xanthine oxidase assay). Epicatechin, emodin-8-glycoside and rutin were isolated from the aerial part and the root of the plant.  相似文献   
102.
Morphology of the mandibular and pharyngeal region, and the feeding habits of Micropogonias furnieri were examined in 256 male and female specimens, between 28.7 and 54.3 cm total length, collected around Morro Puerto Santo, in northeast Sucre State, Venezuela (10 degrees 45'00" N-63 degrees 8'0" W), from May 1989 to April 1990. Micropogonias furnieri has a small ventral mouth; protrusible premaxillary and dentary; first branchial arches with 21 to 27 gill rakers, generally 24 to 25; and 7 to 11 pyloric caecae. The index of vacuity was low, with mean value of 7.00%. The mean intestinal index was 0.72, indicative of carnivorous species. Analysis of frequency of occurrence, indicates preference for crustaceans (45.70%), mainly crabs (34.90%), followed by polychaetes (28.00%), fishes (11.41%) and occasionally mollusks and echinoderms (4.0 and 3.9%, respectively). The diet of this species did not vary with sex.  相似文献   
103.
104.
For sessile marine invertebrates with complex life cycles, habitat choice is directed by the larval phase. Defining which habitat-linked cues are implicated in sessile invertebrate larval settlement has largely concentrated on chemical cues which are thought to signal optimal habitat. There has been less effort establishing physical settlement cues, including the role of surface microtopography. This laboratory based study tested whether surface microtopography alone (without chemical cues) plays an important contributing role in the settlement of larvae of coral reef sessile invertebrates. We measured settlement to tiles, engineered with surface microtopography (holes) that closely matched the sizes (width) of larvae of a range of corals and sponges, in addition to surfaces with holes that were markedly larger than larvae. Larvae from two species of scleractinian corals (Acropora millepora and Ctenactis crassa) and three species of coral reef sponges (Luffariella variabilis, Carteriospongia foliascens and Ircinia sp.,) were used in experiments. L. variabilis, A. millepora and C. crassa showed markedly higher settlement to surface microtopography that closely matched their larval width. C. foliascens and Ircinia sp., showed no specificity to surface microtopography, settling just as often to microtopography as to flat surfaces. The findings of this study question the sole reliance on chemical based larval settlement cues, previously established for some coral and sponge species, and demonstrate that specific physical cues (surface complexity) can also play an important role in larval settlement of coral reef sessile invertebrates.  相似文献   
105.
106.
107.
Mesenchymal stem cell (MSC) therapy is a promising approach to promote tissue regeneration by either differentiating the MSCs into the desired cell type or by using their trophic functions to promote endogenous tissue repair. These strategies of regenerative medicine are limited by the availability of MSCs at the point of clinical care. Our laboratory has recently identified multipotent mesenchymal progenitor cells (MPCs) in traumatically injured muscle tissue, and the objective of this study was to compare these cells to a typical population of bone marrow derived MSCs. Our hypothesis was that the MPCs exhibit multilineage differentiation and expression of trophic properties that make functionally them equivalent to bone marrow derived MSCs for tissue regeneration therapies. Quantitative evaluation of their proliferation, metabolic activity, expression of characteristic cell-surface markers and baseline gene expression profile demonstrate substantial similarity between the two cell types. The MPCs were capable of differentiation into osteoblasts, adipocytes and chondrocytes, but they appeared to demonstrate limited lineage commitment compared to the bone marrow derived MSCs. The MPCs also exhibited trophic (i.e. immunoregulatory and pro-angiogenic) properties that were comparable to those of MSCs. These results suggest that the traumatized muscle derived MPCs may not be a direct substitute for bone marrow derived MSCs. However, because of their availability and abundance, particularly following orthopaedic injuries when traumatized muscle is available to harvest autologous cells, MPCs are a promising cell source for regenerative medicine therapies designed to take advantage of their trophic properties.  相似文献   
108.
109.
Zinc-binding protein-89 regulates Bak to facilitate apoptosis in cancer cells. This study examined if zinc-binding protein-89 regulates Bak through an epigenetic mechanism in hepatocellular carcinoma. We first demonstrated that the expression of Bak was reduced but the levels of deoxyribonucleic acid methyltransferase 1 and histone deacetylase 3 were increased in hepatocellular carcinoma cancer tissues compared to the corresponding non-cancer tissues. Moreover, there was a negative correlation between Bak expression and deoxyribonucleic acid methyltransferase 1 levels in hepatocellular carcinoma. Administration of zinc-binding protein-89 downregulated histone deacetylase 3 expression and suppressed the activities of histone deacetylase and deoxyribonucleic acid methyltransferase, which led to maintenance of histone acetylation status, inhibited the binding of methyl-CpG-binding protein 2 to genomic deoxyribonucleic acid and demethylated CpG islands in the Bak promoter in hepatocellular carcinoma cells. Using the xenograft mouse tumor model, we demonstrated that zinc-binding protein-89 or inhibitors of either epigenetic enzymes could stimulate Bak expression, induce apoptosis, and arrest tumor growth and that the maximal effort was achieved when zinc-binding protein-89 and the enzyme inhibitors were used in combination. Conclusively, zinc-binding protein-89 upregulates the expression of Bak by targeting multiple components of the epigenetic pathway in hepatocellular carcinoma.  相似文献   
110.
Biofouling in marine aquaculture is a specific problem where both the target culture species and/or infrastructure are exposed to a diverse array of fouling organisms, with significant production impacts. In shellfish aquaculture the key impact is the direct fouling of stock causing physical damage, mechanical interference, biological competition and environmental modification, while infrastructure is also impacted. In contrast, the key impact in finfish aquaculture is the fouling of infrastructure which restricts water exchange, increases disease risk and causes deformation of cages and structures. Consequently, the economic costs associated with biofouling control are substantial. Conservative estimates are consistently between 5–10% of production costs (equivalent to US$ 1.5 to 3 billion yr?1), illustrating the need for effective mitigation methods and technologies. The control of biofouling in aquaculture is achieved through the avoidance of natural recruitment, physical removal and the use of antifoulants. However, the continued rise and expansion of the aquaculture industry and the increasingly stringent legislation for biocides in food production necessitates the development of innovative antifouling strategies. These must meet environmental, societal, and economic benchmarks while effectively preventing the settlement and growth of resilient multi-species consortia of biofouling organisms.  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