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   233篇
  免费   26篇
  2022年   1篇
  2021年   3篇
  2020年   3篇
  2019年   5篇
  2018年   6篇
  2017年   4篇
  2016年   7篇
  2015年   5篇
  2014年   15篇
  2013年   11篇
  2012年   16篇
  2011年   12篇
  2010年   7篇
  2009年   6篇
  2008年   3篇
  2007年   11篇
  2006年   16篇
  2005年   10篇
  2004年   7篇
  2003年   11篇
  2002年   6篇
  2001年   7篇
  2000年   5篇
  1999年   6篇
  1998年   3篇
  1997年   4篇
  1996年   2篇
  1995年   2篇
  1994年   3篇
  1993年   6篇
  1992年   3篇
  1991年   9篇
  1990年   6篇
  1989年   5篇
  1988年   2篇
  1987年   7篇
  1986年   4篇
  1985年   4篇
  1984年   5篇
  1983年   1篇
  1982年   3篇
  1981年   2篇
  1978年   2篇
  1974年   1篇
  1973年   1篇
  1967年   1篇
排序方式: 共有259条查询结果,搜索用时 31 毫秒
141.
Background: Because of the known efficacy of several cytokines in the treatment of advanced renal cell cancer (RCC), we have conducted a phase II trial of the efficacy and toxicity of subcutaneous interferon γ (IFNγ) and interleukin-2 (IL-2). Methods: 63 patients with progressive metastatic RCC were treated with 100 μg recombinant IFNγ1b administered three times weekly during weeks 1 and 2 and with 4.5 MU recombinant IL-2 administered on 4 consecutive days during weeks 3 and 4, every 6 weeks. Results: 11% of patients had an objective response (CR: 3%, PR: 8%), 33% had SD. Toxicity was generally mild. The median duration of remissions (CR + PR) was 9.6 months; the median duration of SD 8 months. A significant survival benefit was evident at a median observation time of 51 months for patients (44%) responding to therapy (P < 0.0001). Conclusions: we conclude that sequential treatment with IFNγ and IL-2 may prolong survival in patients with metastatic RCC responding to therapy. Received: 2 April 2000 / Accepted: 21 April 2000  相似文献   
142.
The distribution and abundance of the myxosporean parasite Parvicapsula minibicornis in the Klamath River mirrored that of Ceratomyxa shasta, with which it shares both its vertebrate and invertebrate host. Assay of fish held at sentinel sites and water samples collected from those sites showed that parasite prevalence was highest below Iron Gate dam, which is the barrier to anadromous salmon passage. Above this barrier parasite levels fluctuated, with the parasite detected in the free-flowing river reaches between reservoirs. This was consistent with infection prevalence in the polychaete host, Manayunkia speciosa, which was greater than 1% only in populations tested below Iron Gate dam. Although a low prevalence of infection was detected in juvenile out-migrant fish in the Trinity River, the tributaries tested did not appear to be a significant source of the parasite to the mainstem despite the presence of large numbers of infected adult salmon that migrate and spawn there. Rainbow trout became infected during sentinel exposure, which expands the host range for P. minibicornis and suggests that wild rainbow trout populations are a reservoir for infection, especially above Iron Gate dam. High parasite prevalence in the lower Klamath River is likely a combined effect of high spore input from heavily infected, spawned adult salmon and the proximity to dense populations of polychaetes.  相似文献   
143.
Previous studies have shown that the frequency of gill ventilation during exposure to estrone and gonadal extracts in the round goby (Neogobius melanostomus) is linked to olfactory sensory input. Control over gill ventilation may be a regulatory mechanism used for odorant sampling during reproductive periods. In this study, we examined changes in gill ventilation in osmic and anosmic (nasal occluded), reproductive and non-reproductive male round gobies to a putative steroidal pheromone estrone (1,3,5(10)-estratrien-3-ol-17-one). We tested 5 different concentrations of estrone (10(-12) to 10(-8) M) and showed that the response threshold for estrone varied with the male's reproductive status; it was 10(-11) M in reproductive males, and rose to 10(-9) M in non-reproductive males. However, anosmic reproductive and non-reproductive males did not respond to estrone. These findings suggest that olfactory responses to putative pheromones may change depending on the reproductive status of the fish.  相似文献   
144.
Photoactive perovskite semiconductors are highly tunable, with numerous inorganic and organic cations readily incorporated to modify optoelectronic properties. However, despite the importance of device reliability and long service lifetimes, the effects of various cations on the mechanical properties of perovskites are largely overlooked. In this study, the cohesion energy of perovskites containing various cation combinations of methylammonium, formamidinium, cesium, butylammonium, and 5‐aminovaleric acid is reported. A trade‐off is observed between the mechanical integrity and the efficiency of perovskite devices. High efficiency devices exhibit decreased cohesion, which is attributed to reduced grain sizes with the inclusion of additional cations and PbI2 additives. Microindentation hardness testing is performed to estimate the fracture toughness of single‐crystal perovskite, and the results indicated perovskites are inherently fragile, even in the absence of grain boundaries and defects. The devices found to have the highest fracture energies are perovskites infiltrated into a porous TiO2/ZrO2/C triple layer, which provide extrinsic reinforcement and shielding for enhanced mechanical and chemical stability.  相似文献   
145.
Peatlands are large terrestrial stores of carbon, and sustained CO2 sinks, but over the last century large areas have been drained for agriculture and forestry, potentially converting them into net carbon sources. More recently, some peatlands have been re-wetted by blocking drainage ditches, with the aims of enhancing biodiversity, mitigating flooding, and promoting carbon storage. One potential detrimental consequence of peatland re-wetting is an increase in methane (CH4) emissions, offsetting the benefits of increased CO2 sequestration. We examined differences in CH4 emissions between an area of ditch-drained blanket bog, and an adjacent area where drainage ditches were recently infilled. Results showed that Eriophorum vaginatum colonization led to a “hotspot” of CH4 emissions from the infilled ditches themselves, with smaller increases in CH4 from other re-wetted areas. Extrapolated to the area of blanket bog surrounding the study site, we estimated that CH4 emissions were around 60 kg CH4 ha?1 y?1 prior to drainage, reducing to 44 kg CH4 ha?1 y?1 after drainage. We calculated that fully re-wetting this area would initially increase emissions to a peak of around 120 kg CH4 ha?1 y?1, with around two-thirds of the increase (and 90% of the increase over pre-drainage conditions) attributable to CH4 emissions from E. vaginatum-colonized infilled ditches, despite these areas only occupying 7% of the landscape. We predicted that emissions should eventually decline toward pre-drainage values as the ecosystem recovers, but only if Sphagnum mosses displace E. vaginatum from the infilled ditches. These results have implications for peatland management for climate change mitigation, suggesting that restoration methods should aim, if possible, to avoid the colonization of infilled ditches by aerenchymatous species such as E. vaginatum, and to encourage Sphagnum establishment.  相似文献   
146.
147.
148.
149.

Background  

A synergistic cytotoxic effect has been hypothesized for taxanes and capecitabine, a prodrug of 5-fluorouracil. Based on preclinical studies, this synergism has been attributed to an up-regulation of the enzyme thymidine phosphorylase (TP). Beside tumour tissue, TP is highly expressed in white blood cells, possibly causing increased hematotoxicity, when taxanes are combined with capecitabine. So far, this hypothesis has not been investigated in humans.  相似文献   
150.
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