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   746篇
  免费   46篇
  国内免费   1篇
耳鼻咽喉   13篇
儿科学   22篇
妇产科学   23篇
基础医学   93篇
口腔科学   23篇
临床医学   74篇
内科学   132篇
皮肤病学   40篇
神经病学   18篇
特种医学   27篇
外科学   52篇
综合类   4篇
一般理论   1篇
预防医学   42篇
眼科学   42篇
药学   62篇
中国医学   3篇
肿瘤学   122篇
  2024年   1篇
  2023年   3篇
  2022年   11篇
  2021年   32篇
  2020年   19篇
  2019年   44篇
  2018年   42篇
  2017年   11篇
  2016年   33篇
  2015年   36篇
  2014年   41篇
  2013年   48篇
  2012年   86篇
  2011年   66篇
  2010年   31篇
  2009年   28篇
  2008年   51篇
  2007年   31篇
  2006年   39篇
  2005年   38篇
  2004年   28篇
  2003年   11篇
  2002年   22篇
  2001年   1篇
  2000年   6篇
  1999年   2篇
  1998年   2篇
  1996年   3篇
  1995年   1篇
  1993年   1篇
  1992年   1篇
  1991年   4篇
  1990年   1篇
  1989年   4篇
  1988年   1篇
  1987年   1篇
  1985年   3篇
  1984年   3篇
  1982年   5篇
  1981年   2篇
排序方式: 共有793条查询结果,搜索用时 312 毫秒
1.
Molecular characterization of Wuchereria bancrofti is essential to develop suitable anti-filarial drugs and vaccines. We describe here isolation, sequence analysis and cloning of a partial cDNA of an enzyme superoxide dismutase from this parasite. The immunoscreening of a lambda zap W. bancrofti microfilarial (Mf) cDNA library with microfilaremic sera had resulted in the isolation of several seroreactive clones including, WbSOD. This clone contained a 309 bp insert and showed significant nucleotide and deduced amino acid sequence homologies to the superoxide dismutases of other nematode parasites. The antioxidant property of this enzyme may have important contribution in the defense mechanism of the parasite against host immune response.  相似文献   
2.
We report the case of a 25-year-old male patient who presented with complaints of redness, photophobia, and decreased vision in the right eye of a week's duration. Slit-lamp biomicroscopic examination revealed a cream-colored, irregular elevated inferior iris mass, extending on to the anterior lens surface. Differential diagnoses of a fungal granuloma, a medulloepithelioma, and an amelanotic melanoma were considered. An excisional biopsy of the mass was performed through a superior clear corneal incision. Polymerase chain reaction analysis of the aqueous humor showed a positive pan fungal genome. Histopathology of the biopsied mass showed a giant cell granuloma with surrounding numerous branching, septate hyphae. Culture growth revealed Aspergillus fumigatus We report this case because of the rarity of Aspergillus iris granuloma as a primary presentation of endogenous Aspergillosis and review the relevant literature. Absence of a significant systemic history compounded the diagnostic dilemma in our patient. Definitive differentiation of this rare entity from a foreign body, amelanotic melanoma, and other inflammatory conditions such as sarcoidosis and tuberculosis, may be possible only on microbiological and histo-pathological evaluation.  相似文献   
3.
Clinical Experience with Light-Emitting Diode (LED) Photomodulation   总被引:1,自引:0,他引:1  
Background. Light-emitting diode (LED) photomodulation is a novel nonthermal technology used to modulate cellular activity with light.
Objective:. We describe our experience over the last 2 years using 590 nm LED photomodulation within a dermatologic surgery environment.
Methods. Practical use of nonthermal light energy and emerging applications in 3,500 treatments delivered to 900 patients is detailed.
Results. LED photomodulation has been used alone for skin rejuvenation in over 300 patients but has been effective in augmentation of results in 600 patients receiving concomitant nonablative thermal and vascular treatments such as intense pulsed light, pulsed dye laser, KTP and infrared lasers, radiofrequency energy, and ablative lasers.
Conclusion:. LED photomodulation reverses signs of photoaging using a new nonthermal mechanism. The anti-inflammatory component of LED in combination with the cell regulatory component helps improve the outcome of other thermal-based rejuvenation treatments.  相似文献   
4.
Background. Facial acne scarring has been treated with multiple methods with varying degrees of improvement. Although the 1,320 nm neodymium:yttrium-aluminum-garnet (Nd:YAG) laser has been widely used to improve photoaging, studies analyzing its effects on atrophic acne scarring are limited.
Objective. To evaluate the efficacy of a dynamic cryogen-cooled 1,320 nm Nd:YAG laser for the treatment of atrophic facial acne scars in a larger cohort of patients with long-term follow-up.
Methods. Twenty-nine patients (skin phototypes I–IV) with facial acne scarring received a mean of 5.5 (range 2–17) treatments with a 1,320 nm Nd:YAG laser. Objective physician assessment scores of improvement were determined by side-by-side comparison of preoperative and postoperative photographs at a range of 1 to 27 months (mean 10.4 months) postoperatively. Subjective patient self-assessment scores of improvement were also obtained.
Results. Acne scarring was significantly improved by both physician and patient assessment scores. Mean improvement was 2.8 (  p < .05  ) on a 0- to 4-point scale by physician assessment and 5.4 (  p < .05  ) on a 0- to 10-point scale by patient assessment. No significant complications were observed.
Conclusions. Nonablative laser skin resurfacing with a 1,320 nm Nd:YAG laser can effectively improve the appearance of facial acne scars with minimal adverse sequelae.  相似文献   
5.
Background. Upper eyelid dermatochalasis is typically treated with excisional blepharoplasty. The role of the CO2 laser previously had been confined to that of a vaporizing, incisional, or hemostatic tool. Over the past several years, however, ablative CO2 laser skin resurfacing has been popularized as an adjunctive treatment to blepharoplasty to minimize periorbital rhytides through its vaporizing as well as skin-tightening action.
Objective. To evaluate the safety and efficacy of a high-energy pulsed CO2 laser as a stand-alone treatment for dermatochalasis and periorbital rhytides.
Methods. Sixty-seven patients (skin phototypes I–IV) with mild-to-severe upper eyelid dermatochalasis and periorbital rhytides received periocular CO2 laser skin treatment. Global assessment scores of dermatochalasis and rhytides were determined by a side-by-side comparison of periocular photographs preoperatively and 1, 3, and 6 months postoperatively. In addition, caliper measurements of upper eyelids before and 1, 3, and 6 months after treatment were obtained.
Results. Both dermatochalasis and periorbital rhytides were significantly improved after periocular CO2 laser skin resurfacing. Patients with more severe dermatochalasis and rhytides showed greater improvement after CO2 laser treatment than did those with mild or moderate involvement. Side effects were limited to erythema and transient hyperpigmentation. No scarring, hypopigmentation, or ectropion were observed.
Conclusions. Periocular skin resurfacing with a CO2 laser can safely and effectively improve upper eyelid dermatochalasis and periorbital rhytides.  相似文献   
6.
7.
Heroin use is postulated to act as a cofactor in the neuropathogenesis of human immunodeficiency virus (HIV-1) infection. Astrocytes, integral components of the CNS, are reported to be susceptible to HIV-1 infection. Upon activation, astrocytes release a number of immunoregulatory products or modulate the expression of a number of proteins that foster the immunopathogenesis of HIV-1 infection. However, the role of heroin on HIV-1 infectivity and the expression of the proteome of normal human astrocytes (NHA) have not been elucidated. We hypothesize that heroin modulates the expression of a number of proteins by NHA that foster the neuoropathogenesis of HIV-1 infection. We utilized LTR amplification and the p24 antigen assay to quantitate the effect of heroin on HIV-1 infectivity while difference gel electrophoresis (DIGE) combined with protein identification through high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) to analyze the effects of heroin on the proteomic profile of NHA. Results demonstrate that heroin potentiates HIV-1 replication in NHA. Furthermore, heroin significantly increased protein expression levels for protein kinase C (PKC), reticulocalbin 1 precursor, reticulocalbin 1, tyrosine 3-monooxgenase/tryptophan 5-monooxgenase activation protein, chloride intracellular channel 1, cathepsin D preproprotein, galectin 1 and myosin light chain alkali. Heroin also significantly decreased protein expression for proliferating cell nuclear antigen, proteasome beta 6 subunit, tropomyosin 3, laminin receptor 1, tubulin alpha 6, vimentin, EF hand domain family member D2, Tumor protein D54 (hD54), ATP synthase, H+ transporting, mitochondrial F1 complex and ribosomal protein S14. Identification of unique, heroin-induced proteins may help to develop novel markers for diagnostic, preventative and therapeutic targeting in heroin using subjects.  相似文献   
8.
The natural product quercetin is a flavonoid found in many fruits and vegetables. Previous research has shown that quercetin has antitumor, anti-inflammatory, antiallergic, and antiviral activities. In the present investigation we studied the effect of quercetin on the ability of prostate cancer cell lines with various degrees of aggressive potential to form colonies in vitro. Specifically, we examined the molecular mechanisms underlying this effect, including the expression of cell cycle and tumor suppressor genes as well as oncogenes. We observed that quercetin at concentrations of 25 and 50 μM significantly inhibited the growth of the highly aggressive PC-3 prostate cancer cell line and the moderately aggressive DU-145 prostate cancer cell line, whereas it did not affect colony formation by the poorly aggressive LNCaP prostate cancer cell line or the normal fibroblast cell line BG-9. Using the gene array methodology, we found that quercetin significantly inhibited the expression of specific oncogenes and genes controlling G1, S, G2, and M phases of the cell cycle. Moreover, quercetin reciprocally up-regulated the expression of several tumor suppressor genes. In conclusion, our results demonstrate that the antitumor effects of quercetin directly correlate with the aggressive potential of prostate cancer cells and that the mechanism(s) of quercetin-mediated antitumor effects may involve up-regulation of tumor suppressor genes and reciprocal down-regulation of oncogenes and cell cycle genes. The results of these studies provide a scientific basis for the potential use of flavonoids as nutraceuticals in the chemoprevention of cancer.  相似文献   
9.
The natural product quercetin is a flavonoid found in many fruits and vegetables. Previous research has shown that quercetin has antitumor, anti-inflammatory, antiallergic, and antiviral activities. In the present investigation we studied the effect of quercetin on the ability of prostate cancer cell lines with various degrees of aggressive potential to form colonies in vitro. Specifically, we examined the molecular mechanisms underlying this effect, including the expression of cell cycle and tumor suppressor genes as well as oncogenes. We observed that quercetin at concentrations of 25 and 50 micro M significantly inhibited the growth of the highly aggressive PC-3 prostate cancer cell line and the moderately aggressive DU-145 prostate cancer cell line, whereas it did not affect colony formation by the poorly aggressive LNCaP prostate cancer cell line or the normal fibroblast cell line BG-9. Using the gene array methodology, we found that quercetin significantly inhibited the expression of specific oncogenes and genes controlling G(1), S, G(2), and M phases of the cell cycle. Moreover, quercetin reciprocally up-regulated the expression of several tumor suppressor genes. In conclusion, our results demonstrate that the antitumor effects of quercetin directly correlate with the aggressive potential of prostate cancer cells and that the mechanism(s) of quercetin-mediated antitumor effects may involve up-regulation of tumor suppressor genes and reciprocal down-regulation of oncogenes and cell cycle genes. The results of these studies provide a scientific basis for the potential use of flavonoids as nutraceuticals in the chemoprevention of cancer.  相似文献   
10.
We describe the emergence of a nephropathogenic avian infectious bronchitis virus (IBV) with a novel genotype in India. The Indian IBV isolate exhibited a relatively high degree of sequence divergence with reference strains. The highest homology was observed with strain 6/82 (68%) and the least homology with strain Mex/1765/99 (34.3%).  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