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   658篇
  免费   28篇
  2023年   3篇
  2021年   24篇
  2020年   6篇
  2019年   8篇
  2018年   13篇
  2017年   11篇
  2016年   16篇
  2015年   26篇
  2014年   37篇
  2013年   39篇
  2012年   52篇
  2011年   52篇
  2010年   31篇
  2009年   32篇
  2008年   38篇
  2007年   40篇
  2006年   30篇
  2005年   29篇
  2004年   37篇
  2003年   27篇
  2002年   20篇
  2001年   10篇
  2000年   13篇
  1999年   13篇
  1998年   6篇
  1997年   9篇
  1996年   3篇
  1995年   5篇
  1994年   3篇
  1993年   4篇
  1992年   7篇
  1991年   4篇
  1990年   3篇
  1988年   3篇
  1987年   5篇
  1986年   2篇
  1985年   2篇
  1984年   1篇
  1983年   1篇
  1982年   2篇
  1981年   1篇
  1980年   1篇
  1979年   3篇
  1978年   2篇
  1977年   1篇
  1976年   2篇
  1975年   2篇
  1974年   4篇
  1972年   1篇
  1969年   1篇
排序方式: 共有686条查询结果,搜索用时 171 毫秒
41.
Lipopolysaccharide (LPS) derived from the outer membrane of gram-negative bacteria induces acute lung injury (ALI) in mice. This injury is associated with lung edema, inflammation, diffuse alveolar damage, and severe respiratory insufficiency. We have previously reported that LPS-mediated nitric oxide synthase (NOS) uncoupling, through increases in asymmetric dimethylarginine (ADMA), plays an important role in the development of ALI through the generation of reactive oxygen and nitrogen species. Therefore, the focus of this study was to determine whether mice deficient in endothelial NOS (eNOS-/-) are protected against ALI. In both wild-type and eNOS-/- mice, ALI was induced by the intratracheal instillation of LPS (2 mg/kg). After 24 hours, we found that eNOS-/-mice were protected against the LPS mediated increase in inflammatory cell infiltration, inflammatory cytokine production, and lung injury. In addition, LPS exposed eNOS-/- mice had increased oxygen saturation and improved lung mechanics. The protection in eNOS-/- mice was associated with an attenuated production of NO, NOS derived superoxide, and peroxynitrite. Furthermore, we found that eNOS-/- mice had less RhoA activation that correlated with a reduction in RhoA nitration at Tyr34. Finally, we found that the reduction in NOS uncoupling in eNOS-/- mice was due to a preservation of dimethylarginine dimethylaminohydrolase (DDAH) activity that prevented the LPS-mediated increase in ADMA. Together our data suggest that eNOS derived reactive species play an important role in the development of LPS-mediated lung injury.  相似文献   
42.
43.
44.
45.
In India, about 0.86 million people is engaged in pulling cycle rickshaws as occupation. There is no anthropometric data of cycle rickshaw pullers although data is available for Indian population. The objective of the study was to collect anthropometric data of the cycle rickshaw pullers so that these could be utilized for redesigning a cycle rickshaw. Anthropometric data for 34 body measurements were recorded from 880 rickshaw pullers (age 18 to 66 years) of four different places in India. The mean values of different standing heights, different lengths and breadths of cycle rickshaw pullers were significantly lower compared with Indian population. However, there was no significant difference in erect sitting height. The outcome of the research project is beneficial for the manufacturers of cycle rickshaws and similar products well as users of such products, including rickshaw pullers. The manufacturers would be able to use the data for fabricating newer models of cycle rickshaws which would be more compatible for rickshaw pullers as well as passengers.  相似文献   
46.
Contamination of soils by effluents from industries is on the increase. There is the possibility of remediating these contaminated soils through the use of certain plants. This work investigated the remediating ability of Helianthus annuus and Tithonia diversifolia on the soil polluted with effluents from a paint industry in Ibadan, Nigeria. The experiment consisted of three treatments (H. annuus, T. diversifolia, and control) each replicated three times in a factorial combination of four different fertility managements, viz mineral fertilizer (MF); Grade A organomineral fertilizer (OMF); control1, plants without fertilizer application; and control2, where no fertilizer and no crop was planted using randomized complete block design. A total of 12 plots of 2 × 4 m2 each per phytoplant were obtained. Each plot was planted with the viable seeds of the phytoplant at a spacing of 60 × 30 cm2 and at the seed rate of four seeds per hole. The seedlings were thinned to two stands per hole 2 weeks after planting (WAP) and also weeded two times (2 and 5 WAP). After in situ second successive cultivation, percentage removal of heavy metals by Helianthus annuus with MF and OMF, respectively, were Cu 32.5 and 41.6; Pb 30.3 and 42.8; and Cd 44.5 and 56.7. Tithonia diversifolia, similarly, removed, respectively, Cu 16.9 and 23.4; Pb 36.9 and 43.7; and Cd 20.1 and 35.1. Lower percentages were removed in the controls where no fertilizer was applied. In the shoot of H. annuus with OMF, significantly (p< .05) higher values of 0.27, 1.72, and 0.11 mg kg?1 of Cu, Pb, and Cd, respectively, were removed and stored at second cultivation as against 0.21, 3.39 and 0.08 mg kg?1 in the shoot of T diversifolia. Lower values of Cu, Pb, and Cd were removed with MF, and also at first cultivation with OMF and MF. This study therefore recommends the use of sunflower plants, whether hybrids or wild-types along with the application of OMF for the effective remediation of soils contaminated with heavy metals, particularly in tropical climate.  相似文献   
47.
48.

Background  

Pichia pastoris has been recognized as an effective host for recombinant protein production. A number of studies have been reported for improving this expression system. However, its physiology and cellular metabolism still remained largely uncharacterized. Thus, it is highly desirable to establish a systems biotechnological framework, in which a comprehensive in silico model of P. pastoris can be employed together with high throughput experimental data analysis, for better understanding of the methylotrophic yeast's metabolism.  相似文献   
49.
Computational procedures for predicting metabolic interventions leading to the overproduction of biochemicals in microbial strains are widely in use. However, these methods rely on surrogate biological objectives (e.g., maximize growth rate or minimize metabolic adjustments) and do not make use of flux measurements often available for the wild-type strain. In this work, we introduce the OptForce procedure that identifies all possible engineering interventions by classifying reactions in the metabolic model depending upon whether their flux values must increase, decrease or become equal to zero to meet a pre-specified overproduction target. We hierarchically apply this classification rule for pairs, triples, quadruples, etc. of reactions. This leads to the identification of a sufficient and non-redundant set of fluxes that must change (i.e., MUST set) to meet a pre-specified overproduction target. Starting with this set we subsequently extract a minimal set of fluxes that must actively be forced through genetic manipulations (i.e., FORCE set) to ensure that all fluxes in the network are consistent with the overproduction objective. We demonstrate our OptForce framework for succinate production in Escherichia coli using the most recent in silico E. coli model, iAF1260. The method not only recapitulates existing engineering strategies but also reveals non-intuitive ones that boost succinate production by performing coordinated changes on pathways distant from the last steps of succinate synthesis.  相似文献   
50.
The anthracycline, doxorubicin is a potent cancer chemotherapeutic agent whose therapeutic usefulness is limited by both a dose- and time-dependent cardiomyopathy. We tested the ability of an immunomodulatory alkaloid swainsonine (8alphabeta-indolizidine-1alpha,2alpha,8beta-triol) to protect C57BL/6 mice against lethality within 70 days following a single bolus intraperitoneal injection of LD50/14 doxorubicin. Also, we sought the potential mechanisms responsible for this protection. This extended 70-day study in mice, which may be considered equivalent to a period of 4 to 5 years in humans, has clinical implication for delayed cardiotoxic sequela of therapy with high dose doxorubicin. Mice were pretreated with swainsonine or its diluent buffer, phosphate buffered saline for ten consecutive days prior to a single bolus intraperitoneal injection of a LD50/14 doxorubicin. We have previously defined this swainsonine pretreatment regimen as one of the two optimal conditions for swainsonine rescue of mice from death induced by LD50/14 doxorubicin. The survival and well being of groups of mice pretreated with swainsonine and phosphate buffered saline prior to LD50/14 doxorubicin, sham-treated and untreated were monitored daily for up to 70 days. The bone marrow cellularity of the mice were quantified, and in vitro progenitor cell assays were used to determine the effects of these treatment regimens on bone marrow competence following doxorubicin treatment. The effects of these treatment regimens on heart morphology and hematologic toxicities were also determined. This swainsonine pretreatment regimen significantly abrogated doxorubicin-induced lethality and prolonged survival of mice by facilitating restoration of bone marrow cellularity, accelerating restoration of blood hematocrit and total leukocyte levels, enhancing the proliferation and differentiation of bone marrow pluripotent stem cells along the different paths to progenitor lineages, and preserving the heart morphology. This study strongly suggests a potential role for swainsonine with doxorubicin in cancer chemotherapy.  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