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   913篇
  免费   63篇
  2024年   2篇
  2023年   5篇
  2022年   20篇
  2021年   28篇
  2020年   22篇
  2019年   22篇
  2018年   40篇
  2017年   30篇
  2016年   41篇
  2015年   40篇
  2014年   66篇
  2013年   66篇
  2012年   71篇
  2011年   84篇
  2010年   64篇
  2009年   37篇
  2008年   58篇
  2007年   63篇
  2006年   68篇
  2005年   33篇
  2004年   30篇
  2003年   19篇
  2002年   14篇
  2001年   2篇
  2000年   4篇
  1999年   6篇
  1998年   2篇
  1997年   4篇
  1996年   5篇
  1995年   5篇
  1994年   2篇
  1993年   1篇
  1992年   2篇
  1991年   3篇
  1989年   3篇
  1988年   1篇
  1985年   3篇
  1984年   1篇
  1983年   1篇
  1981年   1篇
  1980年   2篇
  1978年   1篇
  1973年   2篇
  1966年   1篇
  1965年   1篇
排序方式: 共有976条查询结果,搜索用时 171 毫秒
71.
72.
BACKGROUND: Spontaneous splenic rupture (SSR) is a very rare complication described in several hundred patients, mainly as case reports. It is defined as a splenic rupture without antecedent injury. The authors of the present paper describe the only two SSR cases diagnosed at the Hemato-oncology department, coincidentally in one year. PATIENTS: The first patient was admitted to hospital because of planned chemotherapy for relapsed hairy cell leukemia. The second was directed to the Hemato-oncology outpatient department because of anemia and painful splenomegaly diagnosed by a physician. The diagnose of hematologic malignancy (diffuse large B-cell lymphoma) was determined subsequently on the basis of histological examination of the spleen. CONCLUSION: It is necessary to consider SSR not only in patients with known diagnosis of malignant disease but in the patients with negative anamnesis, too. The aim of the paper is to draw attention to the existence of this complication.  相似文献   
73.
BACKGROUND: Monoclonal antibodies have dramatically changed the treatment possibilities for follicular lymphoma. (90)Y-ibritumomab tiuxetan (Zevalin) is the first radioimmunotherapy agent approved for the treatment of relapsed and resistant follicular lymphoma patients. Long-term benefit was observed especially for patients achieving CR after radioimmunotherapy. METHODS AND RESULTS: A 65-year-old female patient with the second relapse of CD20 positive follicular lymphoma and multiple concomitant diseases was treated with four weekly doses of rituximab (375 mg/m(2)). (18)F-fluoro-deoxyglucose positron emission tomography combined with computed tomography (PET-CT) demonstrated only partial response to therapy with persistent PET scan positivity in enlarged abdominal lymph nodes. Therefore, it was decided to treat her with a 1200-MBq (32-mCi) dose of (90)Y-ibritumomab tiuxetan radioimmunotherapy. No acute complications were noted afterwards. Hematological nadirs were reached 4 weeks later, with a platelet count of 24 x 10(9)/l that normalized within the next 2 weeks. The patient had neither infection nor bleeding complications. Eight weeks after radioimmunotherapy, the PET-CT scans documented only 3 lymph nodes around the abdominal aorta, maximum size 2 x 1 cm. The PET scan analysis proved no accumulation of (18)F-fluoro-deoxy-glucose in any lymph nodes or other organs and tissues. CONCLUSIONS: Sequential treatment with rituximab and (90)Y-ibritumomab tiuxetan may be an interesting alternative in cases of relapsed follicular or other indolent lymphomas in pretreated or older patients with other concomitant diseases.  相似文献   
74.
75.
Hydrobiologia - To understand the spatiotemporal overlap in the habitat use of sympatric predators, we studied longitudinal activity and reservoir section and depth use of pike (Esox lucius),...  相似文献   
76.
Molecular and Cellular Biochemistry - Increased concentration of plasma homocysteine (Hcy) is an independent risk factor of cardiovascular disease, yet the mechanism by which hyperhomocysteinemia...  相似文献   
77.
Selective logging is one of the most common forms of forest use in the tropics. Although the effects of selective logging on biodiversity have been widely studied, there is little agreement on the relationship between life-history traits and tolerance to logging. In this study, we assessed how species traits and logging practices combine to determine species responses to selective logging, based on over 4000 observations of the responses of nearly 1000 bird species to selective logging across the tropics. Our analysis shows that species traits, such as feeding group and body mass, and logging practices, such as time since logging and logging intensity, interact to influence a species'' response to logging. Frugivores and insectivores were most adversely affected by logging and declined further with increasing logging intensity. Nectarivores and granivores responded positively to selective logging for the first two decades, after which their abundances decrease below pre-logging levels. Larger species of omnivores and granivores responded more positively to selective logging than smaller species from either feeding group, whereas this effect of body size was reversed for carnivores, herbivores, frugivores and insectivores. Most importantly, species most negatively impacted by selective logging had not recovered approximately 40 years after logging cessation. We conclude that selective timber harvest has the potential to cause large and long-lasting changes in avian biodiversity. However, our results suggest that the impacts can be mitigated to a certain extent through specific forest management strategies such as lengthening the rotation cycle and implementing reduced impact logging.  相似文献   
78.
79.
Patch configuration is viewed as an important factor affecting the distributions of plant species. Although a number of studies have explored the relationship between plant life‐history traits and species’ distributions in fragmented landscapes, the effect of individual traits on the dependence of species on historical versus current landscape configurations remains unclear. We identified the extent to which present (2000s) and historical (1843, 1954, 1980s) patch configurations (area and connectivity) and patch age affected the distributions of 99 species inhabiting dry calcareous grasslands. We used traits related to dispersal, survival, growth and habitat preferences to explain the dependence of 60 of these species on present and historical configurations, and the age of grassland patches. We found that most of the species had an affinity to currently or historically large, older and more isolated patches. This suggests that many dry grassland species are not in equilibrium with the current landscape, as their distributions still reflect past landscape structures. Rapidly growing species with higher seed bank longevity and nutrient requirements primarily occur in young, large grassland patches whereas species with the opposite traits occur in older, historically large and currently more isolated smaller patches. We hypothesise that patch quality is the reason why different species occupy patches of different age. Species occupying young, large patches commonly disperse by endozoochory. By contrast, no dispersal trait is associated with species occupying old, usually isolated patches. Our results suggest that species occupying old patches are exposed to higher potential risk of extinction, as their distributions are probably limited by the low number and connectivity of available suitable patches and poor dispersal ability. We thus suggest that the dynamics of these species can effectively be supported by improving the quality of young grassland patches.  相似文献   
80.
Intracellular production of reactive oxygen species (ROS) plays an important role in the control of cell physiology. For the assessment of intracellular ROS production, a plethora of fluorescent probes is commonly used. Interestingly, chemical structures of these probes imply they could be substrates of plasma membrane efflux pumps, called ABC transporters. This study tested whether the determination of intracellular ROS production and mitochondrial membrane potential by selected fluorescent probes is modulated by the expression and activity of ABC transporters. The sub-clones of the HL-60 cell line over-expressing MDR1, MRP1 and BCRP transporters were employed. ROS production measured by luminol- and L-012-enhaced chemiluminescence and cytochrome c reduction assay showed similar levels of ROS production in all the employed cell lines. It was proved that dihydrorhodamine 123, dihexiloxocarbocyanine iodide, hydroethidine, tetrachloro-tetraethylbenzimidazolocarbo-cyanine iodide and tetramethylrhodamine ethyl ester perchlorate are substrates for MDR1; dichlorodihydrofluoresceine, hydroethidine and tetramethylrhodamine ethyl ester perchlorate are substrates for MRP1; dichlorodihydrofluoresceine, dihydrorhodamine 123, hydroethidine and tetrachloro-tetraethylbenzimidazolocarbo-cyanine iodide are substrates for BCRP. Thus, the determination of intracellular ROS and mitochondrial potential by the selected probes is significantly altered by ABC transporter activities. The activity of these transporters must be considered when employing fluorescent probes for the assessment of ROS production or mitochondrial membrane potential.  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