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   2465篇
  免费   140篇
  国内免费   20篇
耳鼻咽喉   32篇
儿科学   79篇
妇产科学   49篇
基础医学   380篇
口腔科学   52篇
临床医学   209篇
内科学   619篇
皮肤病学   101篇
神经病学   216篇
特种医学   43篇
外科学   190篇
综合类   8篇
预防医学   221篇
眼科学   37篇
药学   194篇
中国医学   10篇
肿瘤学   185篇
  2024年   5篇
  2023年   33篇
  2022年   58篇
  2021年   132篇
  2020年   50篇
  2019年   94篇
  2018年   103篇
  2017年   71篇
  2016年   70篇
  2015年   75篇
  2014年   92篇
  2013年   139篇
  2012年   190篇
  2011年   214篇
  2010年   104篇
  2009年   82篇
  2008年   155篇
  2007年   146篇
  2006年   143篇
  2005年   140篇
  2004年   133篇
  2003年   119篇
  2002年   110篇
  2001年   10篇
  2000年   3篇
  1999年   11篇
  1998年   23篇
  1997年   10篇
  1996年   13篇
  1995年   12篇
  1994年   4篇
  1993年   5篇
  1992年   5篇
  1990年   3篇
  1989年   3篇
  1988年   3篇
  1987年   5篇
  1985年   5篇
  1984年   4篇
  1983年   3篇
  1981年   4篇
  1980年   4篇
  1977年   4篇
  1976年   2篇
  1975年   2篇
  1973年   3篇
  1972年   3篇
  1971年   3篇
  1969年   2篇
  1927年   3篇
排序方式: 共有2625条查询结果,搜索用时 15 毫秒
991.
Neutralizing antibodies have been thought to be required for protection against acutely cytopathic viruses, such as the neurotropic vesicular stomatitis virus (VSV). Utilizing mice that possess B cells but lack antibodies, we show here that survival upon subcutaneous (s.c.) VSV challenge was independent of neutralizing antibody production or cell-mediated adaptive immunity. However, B cells were absolutely required to provide lymphotoxin (LT) α1β2, which maintained a protective subcapsular sinus (SCS) macrophage phenotype within virus draining lymph nodes (LNs). Macrophages within the SCS of B cell-deficient LNs, or of mice that lack LTα1β2 selectively in B cells, displayed an aberrant phenotype, failed to replicate VSV, and therefore did not produce type I interferons, which were required to prevent fatal VSV invasion of intranodal nerves. Thus, although B cells are essential for survival during VSV infection, their contribution involves the provision of innate differentiation and maintenance signals to macrophages, rather than adaptive immune mechanisms.  相似文献   
992.
Clinical trials for the treatment of schizophrenia now often include cognitive assessments in addition to clinical ratings of symptoms. Recently, these trials have included cross-national assessments. It is not clear if translated psychological tests produce consistent results across different languages. This paper presents the results of a study of the comparability of the results of cognitive assessments in different English-speaking countries and a number of countries where tests were translated into other languages. Performance on tests of executive functioning, verbal and visuo-spatial learning and memory, language skills, psychomotor speed, and vigilance was compared across the first episode patients with schizophrenia (n = 301) assessed in six different languages (English, French, Finnish, German, Hebrew, and Afrikaans), including two different countries where patients were assessed in English and other languages: Canada (French) and South Africa (Afrikaans). The variance in performance across the sites tested in English was as large as the variance between English and non-English speakers when all tests were considered. Performance differences across English and other languages were found only for executive functions, vigilance, and psychomotor speed, with executive functioning differences nonsignificant when education was considered. No differences were found between English and non-English speakers in Canada. These results suggest that the translation of tests of memory and verbal skills can lead to consistent results across translated versions of the tests. Differences between countries were greater than differences between languages, suggesting the need to consider representativeness of patient samples in terms of local educational attainment. In general, these data support the validity of cross-national neuropsychological assessments.  相似文献   
993.
994.
995.
Borage (Borago officinalis) is a plant with nutritional value that is also used in traditional medicine to treat gastrointestinal disease. This study investigated the amoebicidal activity of a methanol extract of borage. The 50% inhibitory concentration (IC??) of the extract for Entamoeba histolytica was 33 μg/mL. The 50% lethal dose of the extract for brine shrimp was greater than 1,000?μg/mL. The IC?? of the extract for Vero cells was 203.9?μg/mL. These results support the use of borage to prevent diseases associated with E. histolytica infection.  相似文献   
996.
Tynanthus panurensis (Bureau) Sanwith (Bignoniaceae) is a liana vine used in traditional Amazonian medicine as a tonic and energizer as well as a treatment for rheumatism. These traditional indications prompted this study of the antioxidant and anti-inflammatory activities of T. panurensis bark extract (ETP). Phytochemical analysis of ETP showed the presence of saponins and a high concentration of phenols and flavonoids. A battery of in vitro tests revealed that the extract has free radical-scavenging antioxidant properties and reduces microsomal lipid peroxidation, uric acid synthesis, and tumor necrosis factor-α production. The anti-inflammatory properties of ETP were further confirmed in vivo in a rat carrageenan edema model, in which the extract exhibited a potent activity. These results support the idea that T. panurensis bark extract could be beneficial for treating inflammation and are in agreement with one of the main traditional uses of this plant.  相似文献   
997.
998.
999.
For therapeutic peptides, the lung represents an attractive, noninvasive route into the bloodstream. To achieve optimal bioavailability and control their fast rate of absorption, peptides can be protected by coprocessing with polymers such as polyethylene glycol (PEG). Here, we formulated and characterized salmon calcitonin (sCT)-loaded microparticles using linear or branched PEG (L-PEG or B-PEG) and hydroxypropyl-beta-cyclodextrin (HPβCD) for pulmonary administration. Mixtures of sCT, L-PEG or B-PEG and HPβCD were co-spray dried. Based on the particle properties, the best PEG:HPβCD ratio was 1:1 w:w for both PEGs. In the sCT-loaded particles, the L-PEG was more crystalline than B-PEG. Thus, L-PEG-based particles had lower surface free energy and better aerodynamic behavior than B-PEG-based particles. However, B-PEG-based particles provided better protection against chemical degradation of sCT. A decrease in sCT permeability, measured across Calu-3 bronchial epithelial monolayers, occurred when the PEG and HPβCD concentrations were both 1.6 wt %. This was attributed to an increase in buffer viscosity, caused by the two excipients. sCT pharmacokinetic profiles in Wistar rats were evaluated using a 2-compartment model after iv injection or lung insufflation. The maximal sCT plasma concentration was reached within 3 min following nebulization of sCT solution. L-PEG and B-PEG-based microparticles were able to increase T(max) to 20 ± 1 min and 18 ± 8 min, respectively. Furthermore, sCT absolute bioavailability after L-PEG-based microparticle aerosolization at 100 μg/kg was 2.3 times greater than for the nebulized sCT solution.  相似文献   
1000.
We report the synthesis of new chemical probes (1a,b, 2a-c, 3a-c) based on the structure of the main endocannabinoids for their use in biological systems directly or via click chemistry. As proof of concept, 2-arachidonyl glyceryl ether based biotinylated 3b enables direct visualization of CB(1) receptor in cells. These results represent the starting point for the development of advanced small molecule chemical probes able to generate valuable information about the cannabinoid receptors.  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