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   7625篇
  免费   458篇
  国内免费   40篇
耳鼻咽喉   84篇
儿科学   208篇
妇产科学   152篇
基础医学   1181篇
口腔科学   194篇
临床医学   512篇
内科学   1954篇
皮肤病学   305篇
神经病学   586篇
特种医学   237篇
外科学   586篇
综合类   51篇
一般理论   1篇
预防医学   467篇
眼科学   163篇
药学   556篇
中国医学   50篇
肿瘤学   836篇
  2024年   10篇
  2023年   61篇
  2022年   124篇
  2021年   209篇
  2020年   124篇
  2019年   163篇
  2018年   213篇
  2017年   199篇
  2016年   218篇
  2015年   204篇
  2014年   322篇
  2013年   356篇
  2012年   499篇
  2011年   594篇
  2010年   348篇
  2009年   356篇
  2008年   454篇
  2007年   561篇
  2006年   497篇
  2005年   541篇
  2004年   527篇
  2003年   475篇
  2002年   409篇
  2001年   79篇
  2000年   50篇
  1999年   72篇
  1998年   69篇
  1997年   51篇
  1996年   48篇
  1995年   34篇
  1994年   23篇
  1993年   24篇
  1992年   14篇
  1991年   16篇
  1990年   22篇
  1989年   15篇
  1988年   15篇
  1987年   12篇
  1986年   10篇
  1985年   8篇
  1984年   12篇
  1983年   7篇
  1982年   6篇
  1981年   9篇
  1980年   13篇
  1978年   6篇
  1977年   6篇
  1975年   5篇
  1974年   7篇
  1972年   5篇
排序方式: 共有8123条查询结果,搜索用时 0 毫秒
1.

Background

Photosensitizers used for photodynamic therapy (PDT) to treat dermatologic disease are metabolized into mainly protoporphyrin IX (PpIX), which has five absorption wavelength peaks: 410?nm, 510?nm, 545?nm, 580?nm, and 630?nm. Although only red light around 635?nm and blue light around 400?nm are used as light sources for PDT, the efficiency of PDT might be improved by using multiple wavelengths, including those that correspond to the other absorption peaks of PpIX. Furthermore, because the target disease often occurs on the face, a flexible-type light-source unit that can be fitted to the lesion without unnecessarily exposing the mucous membranes, e.g., the eyes, nostrils, and mouth, is preferred.

Objective

We investigated the efficacy of a flexible light-emitting diode (LED) unit that emits multiple wavelengths to improve PDT effects.

Methods

HaCaT cells were incubated with 5-ALA and subsequently irradiated with either a single wavelength or sequentially with two wavelengths. Cell viability and reactive oxygen species were analyzed. Nude mice were implanted with COLO679 cells by subcutaneous injection into the flank. 5-ALA was subcutaneously injected into the tumor. The tumor was irradiated with 50?J/cm2 (day 0) and assessed daily until day 21.

Results

The synergistic PDT effects of dual-wavelength irradiation and reactive oxygen species production were highest with the 405-nm and 505-nm wavelength combination. This dual wavelength combination was also the most effective in vivo.

Conclusion

We could therefore conclude that dual-wavelength PDT is an efficient strategy for improving the therapeutic effects of PDT. Using a flexible LED unit is expected to achieve more uniform irradiation of uneven areas.  相似文献   
2.
3.
4.
The requirement for endoscopic access to a stricture is a major limitation of the endoscopic dilatation for the treatment of strictures in the gastrointestinal tract. We have developed the double‐balloon enteroscopy method that enables visualization of the entire small bowel. In addition, double‐balloon enteroscopy has a potential for the interventional therapy including dilatation of strictures. We present here a case of jejunal strictures in a 47‐year‐old woman with Crohn's disease successfully treated with a balloon catheter in combination with double‐balloon enteroscopy. Balloon dilation with double‐balloon enteroscopy is a promising method for the treatment of small bowel strictures in Crohn's disease.  相似文献   
5.
We used morphological, biochemical and immunohistochemical methods to assess the response of Müller cells after experimental lensectomy-vitrectomy in rabbits. We observed widened intercellular spaces between the Müller cells and nerve fibers of ganglion cells, and increased electron opacity in the Müller cells of eyes injected with silicone oil. No apparent morphological changes were detected in the Müller cells of air-injected eyes. The specific and total activities of Müller cell-marker enzymes (glucose 6-phosphatase and glutamine synthetase) showed an initial increase, followed by a decrease. Glial fibrillary acidic protein immunoreactivity was not found in the Müller cells of the normal rabbit retina but was exhibited after surgery. Our results showed that markers of Müller cells associated with glycogenolysis and/or gluconeogenesis, glutamate-glutamine cycle and cytoskeletal protein metabolism were affected by the experimental lensectomy-vitrectomy.  相似文献   
6.
7.
PURPOSE: The association of BRCA2 polymorphisms at codon 372 [Asn (N)/His (H)]and codon 784 [Met (M)/Val (V)] with breast cancer risk was evaluated in Japanese women. In addition, the prognostic significance of these polymorphisms was studied in breast cancer patients. EXPERIMENTAL DESIGN: A case-control study was conducted to examine the association of the BRCA2 N/H372 polymorphism and M/V 784 polymorphism with breast cancer risk (cases = 149, controls = 154). The prognostic significance of these polymorphisms was evaluated in 139 patients with primary breast cancer. RESULTS: No significant association was observed between the N/H372 polymorphism and breast cancer risk. In contrast, a significant increase in breast cancer risk (odds ratio, 2.03; 95% confidence interval, 1.07-3.87) was observed in carriers of the variant allele (V784) of the M/V784 polymorphism as compared with noncarriers after adjustment for the classical risk factors, age, family history, parity, body mass index, and so forth. Among breast cancer patients, various clinicopathological parameters including menopausal status, tumor size, lymph node status, histological grade, and estrogen-receptor status were not significantly different between the carriers and noncarriers of the variant allele with regard to both N/H372 and M/V784 polymorphisms. The N/H 372 polymorphism was not significantly associated with patient prognosis. On the other hand, breast cancer patients carrying the variant allele of M/V784 polymorphism showed a significantly (P = 0.014) lower 3-year disease-free survival rate (63%) than noncarriers (92%). Multivariate analysis has revealed that the M/V784 polymorphism is a significant prognostic factor, being independent of the other conventional prognostic factors such as lymph node status and estrogen receptor status. CONCLUSION: These results suggest that the M/V784 polymorphism, but not the N/H372 polymorphism, would be useful in the selection of women at high risk for developing breast cancer and would also serve as a clinically useful prognostic factor in breast cancer patients.  相似文献   
8.
We report a 52 year-old man presenting with an acute considerable hair loss induced by carbamazepine (CBZ). The remarkable scalp hair loss started within a week after CBZ administration. There was no evidence of dermatitis or allergic reaction, or other cause for the hair loss. The serum concentration of CBZ was 8.6 microg/ml (therapeutic range 8-12 microg/ml). CBZ was discontinued, and the hair loss stopped within several days with new hair growth. Medication-induced hair loss is an occasional adverse effect of many drugs used for neuropsychological diseases. CBZ also induces hair loss and its frequency was reported below 2%. Only a limited number of detailed case reports describing CBZ-induced hair loss were available, and we found these cases could divide into two groups with regard to a delay in starting hair loss after administration of CBZ. In one group, the hair loss started within a week suggesting anagen effluvium and in another it started after two or three months suggesting telogen effluvium. This finding suggests the causative mechanism of CBZ-induced hair loss is not unitary.  相似文献   
9.
OBJECTIVE: To evaluate the influence of the age at disease onset on the clinical symptoms, laboratory findings, treatment, and complications of microscopic polyangiitis (MPA). PATIENTS: From 1999 to 2001, we encountered 4 MPA patients with disease onset at age 65 or older (average 77.3, all were female: the elderly group). For comparison, 4 MPA patients with disease onset a 64 years or younger (average 44.7, two were male: the non-elderly group) were used. RESULTS: There was no statistically significant difference in clinical features between the two groups. All patients in the elderly group were referred to our hospital, because of fever of unknown origin or suspicion of connective tissue disease. The elderly group had a longer duration from the first admission to the start of treatment. Renal biopsies were done in all of the non-elderly group and one of the elderly group. The diagnosis of the other 3 patients of the elderly group was based on muscle or nerve biopsy, showing necrotizing vasculitis. At the time of diagnosis, antibodies to myeloperoidase (MPO-ANCA) were positive in 7 of 8 patients (87.5%). 2 patients of the non-elderly group were died of heart failure and hepatic failure by cyclophosphamide (CYC). The other 6 patients achieved substantial improvement. CONCLUSIONS: Muscle or nerve biopsy helped clinical management of elderly patients when renal biopsies could not be done. IVCY was relatively safe and effective treatment for MPA in elderly as well as non-elderly patients.  相似文献   
10.
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