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   1439篇
  免费   113篇
  国内免费   9篇
耳鼻咽喉   28篇
儿科学   9篇
妇产科学   14篇
基础医学   235篇
口腔科学   31篇
临床医学   91篇
内科学   272篇
皮肤病学   93篇
神经病学   70篇
特种医学   73篇
外科学   273篇
综合类   15篇
一般理论   3篇
预防医学   79篇
眼科学   23篇
药学   95篇
中国医学   29篇
肿瘤学   128篇
  2024年   3篇
  2023年   16篇
  2022年   39篇
  2021年   58篇
  2020年   40篇
  2019年   42篇
  2018年   70篇
  2017年   45篇
  2016年   59篇
  2015年   72篇
  2014年   82篇
  2013年   111篇
  2012年   150篇
  2011年   98篇
  2010年   55篇
  2009年   34篇
  2008年   80篇
  2007年   75篇
  2006年   67篇
  2005年   67篇
  2004年   64篇
  2003年   56篇
  2002年   40篇
  2001年   19篇
  2000年   15篇
  1999年   11篇
  1998年   3篇
  1997年   6篇
  1996年   7篇
  1995年   8篇
  1994年   3篇
  1993年   5篇
  1992年   7篇
  1991年   9篇
  1990年   7篇
  1989年   8篇
  1988年   2篇
  1987年   3篇
  1986年   5篇
  1985年   2篇
  1984年   6篇
  1980年   1篇
  1979年   1篇
  1978年   2篇
  1975年   2篇
  1974年   2篇
  1973年   1篇
  1968年   2篇
  1944年   1篇
排序方式: 共有1561条查询结果,搜索用时 15 毫秒
991.
We investigated the effects of Cistanches herba (CH) on the male reproductive system in mice, assessing CREM gene expression and spermatogenesis. Our results demonstrate that CH treatment lead to a significant decrease in sperm count dose-dependently, 298.3 ± 48.9 vs. 296.6 ± 102.4 (250 mg/kg), 236.7 ± 75.1 (500 mg/kg), 223.0 ± 48.7 × 106 (1000 mg/kg), respectively. Additionally, serum testosterone levels decreased following CH treatment to as low as ~57% compared with the vehicle-treated group. CREM gene expression was also down-regulated following CH treatment and histological examination of the testicular seminiferous tubules showed severe damage on CH treatment. These results suggest that CH induces cytotoxicity in the male reproductive system, through the inhibition of spermatogenesis, testicular damage, and limited hormonal function.  相似文献   
992.
Media attitudes and media use have been the focus of considerable academic research. This article uses this research to explore patient and health care practitioner attitudes toward telemedicine interactions via videoconferencing technology.  相似文献   
993.

Aims of the study

Gynura procumbens (Merr.), which is known as “Sambung nyawa”, is widely used in South East Asian countries in the traditional treatment of many ailments. However, there is little toxicological information available regarding safety following repeated exposure.The present investigation describes the toxicity of a methanol extract of Gynura procumbens leaves in rats.

Materials and methods

For acute toxicity studies, a methanol extract of Gynura procumbens was orally administered to Sprague–Dawley rats (female and male) at a dose range of 1000–5000 mg/kg. For sub-chronic toxicity studies, the rats were orally administered the methanol extract of Gynura procumbens at the doses of 125, 250, and 500 mg/(kg day) for a period of 13 weeks. The animals were sacrificed, followed by examination of their organs and blood serum.

Results and conclusions

Administration of the methanol extract from Gynura procumbens leaves at 1000–5000 mg/kg did not produce mortality or significant changes in the general behaviour, body weight, or organ gross appearance of rats. There were no significant differences in the general condition, growth, organ weights, haematological parameters, clinical chemistry values, or gross and microscopic appearance of the organs from the treatment groups as compared to the control group. Therefore, the NOAEL for the Gynura procumbens methanol extract is 500 mg/(kg day) administered orally for 13 weeks.  相似文献   
994.
A qualitative study was conducted to examine parental concerns over the issue of disclosure with those whose children were diagnosed with HIV/AIDS. Semi-structured interviews were conducted with seven parents and the main issues that arose from the interviews were (a) parents' explanation of their children's medical condition; (b) factors that influence disclosure; (c) factors that hinder disclosure; and (d) parents' perception on the appropriate time for disclosure. Parents viewed disclosure as a single event, as opposed to an ongoing process where varying levels of information on the illness was to be provided in accordance to the children's individual cognitive and emotional development.  相似文献   
995.
Two cases of natural killer (NK)/T-cell primary nasal lymphoma with similar clinical presentations are reported, for comparison and contrast, to highlight the clinical issues and challenges posed by this unusual disease, its aggressiveness being matched only by its rarity. Presenting as a lesion in the nasal cavity with histological features of malignant lymphoma, primary nasal lymphoma is an uncommon extranodal lymphoma, which poses problems in both diagnosis and management. In people of oriental descent, the common cell subtype is NK/T-cell. Although it is generally thought that combination treatment with chemotherapy and radiation is the best management for early stage non-Hodgkin's lymphoma (NHL), there is still debate as to whether combined therapy is optimal treatment for this particular subtype of NHL, given that it responds less well to conventional chemotherapy. Herein we report two patients to illustrate these controversies.  相似文献   
996.
997.
998.
999.
Cognitive dysfunction is a core feature of dementia and a prominent feature in psychiatric disease. As non-redundant regulators of intracellular cAMP gradients, phosphodiesterases (PDE) mediate fundamental aspects of brain function relevant to learning, memory, and higher cognitive functions. Phosphodiesterase-4B (PDE4B) is an important phosphodiesterase in the hippocampal formation, is a major Disrupted in Schizophrenia 1 (DISC1) binding partner and is itself a risk gene for psychiatric illness. To define the effects of specific inhibition of the PDE4B subtype, we generated mice with a catalytic domain mutant form of PDE4B (Y358C) that has decreased ability to hydrolyze cAMP. Structural modeling predictions of decreased function and impaired binding with DISC1 were confirmed in cell assays. Phenotypic characterization of the PDE4BY358C mice revealed facilitated phosphorylation of CREB, decreased binding to DISC1, and upregulation of DISC1 and β-Arrestin in hippocampus and amygdala. In behavioral assays, PDE4BY358C mice displayed decreased anxiety and increased exploration, as well as cognitive enhancement across several tests of learning and memory, consistent with synaptic changes including enhanced long-term potentiation and impaired depotentiation ex vivo. PDE4BY358C mice also demonstrated enhanced neurogenesis. Contextual fear memory, though intact at 24 h, was decreased at 7 days in PDE4BY358C mice, an effect replicated pharmacologically with a non-selective PDE4 inhibitor, implicating cAMP signaling by PDE4B in a very late phase of consolidation. No effect of the PDE4BY358C mutation was observed in the prepulse inhibition and forced swim tests. Our data establish specific inhibition of PDE4B as a promising therapeutic approach for disorders of cognition and anxiety, and a putative target for pathological fear memory.  相似文献   
1000.
The cation channel of sperm (CatSper) protein family plays important roles in male reproduction and infertility. The four members of this family are expressed exclusively in the testis and are localized differently in sperm. To investigate the effects of Panax ginseng treatment on the expression of CatSper genes and sperm hyperactivation in male mice, sperm motility and CatSper gene expression were assessed using a computer-assisted semen analysis system, a Fluoroskan Ascent microplate fluorometer to assess Ca2* influx, real.time polymerase chain reaction, Western blotting and immunofluorescence. The results suggested that the Ca2* levels of sperm cells treated with P. ginseng were increased significantly compared with the normal group. The P. ginseng-treated groups showed increased sperm motility parameters, such as the curvilinear velocity and amplitude of lateral head displacement. Taken together, the data suggest that CatSper messenger ribonucleic acid levels were increased significantly in mouse testes in the P. ginseng-treated group, as was the protein level, with the exception of CatSper2. In conclusion, P. ginseng plays an important role in improving sperm hyperactivation via CatSper gene expression.  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