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   6333篇
  免费   405篇
  国内免费   61篇
耳鼻咽喉   107篇
儿科学   183篇
妇产科学   119篇
基础医学   896篇
口腔科学   436篇
临床医学   485篇
内科学   1334篇
皮肤病学   147篇
神经病学   445篇
特种医学   183篇
外科学   872篇
综合类   37篇
一般理论   2篇
预防医学   622篇
眼科学   206篇
药学   397篇
中国医学   49篇
肿瘤学   279篇
  2023年   47篇
  2022年   106篇
  2021年   186篇
  2020年   130篇
  2019年   163篇
  2018年   211篇
  2017年   156篇
  2016年   170篇
  2015年   205篇
  2014年   270篇
  2013年   317篇
  2012年   478篇
  2011年   448篇
  2010年   275篇
  2009年   197篇
  2008年   324篇
  2007年   336篇
  2006年   305篇
  2005年   292篇
  2004年   272篇
  2003年   269篇
  2002年   178篇
  2001年   134篇
  2000年   142篇
  1999年   130篇
  1998年   47篇
  1997年   51篇
  1996年   49篇
  1995年   40篇
  1994年   36篇
  1993年   30篇
  1992年   78篇
  1991年   69篇
  1990年   69篇
  1989年   55篇
  1988年   62篇
  1987年   60篇
  1986年   55篇
  1985年   52篇
  1984年   33篇
  1983年   22篇
  1982年   16篇
  1981年   19篇
  1980年   14篇
  1979年   23篇
  1976年   14篇
  1975年   17篇
  1974年   14篇
  1973年   16篇
  1972年   15篇
排序方式: 共有6799条查询结果,搜索用时 15 毫秒
41.
42.
This report describes a rare case of coexistence of benign phyllodes tumor, which measured 9 cm in the right breast, and invasive ductal carcinoma of 6 cm in the left breast, synchronous and independent, in a 66-year-old patient. The patient underwent a bilateral mastectomy due to the size of both lesions. Such situations are rare and usually refer to the occurrence of ductal or lobular carcinoma in situ when associated with malignant phyllodes tumors, and more often in ipsilateral breast or intra-lesional.  相似文献   
43.
Type II deiodinase (D2) activates thyroid hormone by converting thyroxine (T4) to 3,5,3′-triiodothyronine (T3). This allows plasma T4 to signal a negative feedback loop that inhibits production of thyrotropin-releasing hormone (TRH) in the mediobasal hypothalamus (MBH) and thyroid-stimulating hormone (TSH) in the pituitary. To determine the relative contributions of these D2 pathways in the feedback loop, we developed 2 mouse strains with pituitary- and astrocyte-specific D2 knockdown (pit-D2 KO and astro-D2 KO mice, respectively). The pit-D2 KO mice had normal serum T3 and were systemically euthyroid, but exhibited an approximately 3-fold elevation in serum TSH levels and a 40% reduction in biological activity. This was the result of elevated serum T4 that increased D2-mediated T3 production in the MBH, thus decreasing Trh mRNA. That tanycytes, not astrocytes, are the cells within the MBH that mediate T4-to-T3 conversion was defined by studies using the astro-D2 KO mice. Despite near-complete loss of brain D2, tanycyte D2 was preserved in astro-D2 KO mice at levels that were sufficient to maintain both the T4-dependent negative feedback loop and thyroid economy. Taken together, these data demonstrated that the hypothalamic-thyroid axis is wired to maintain normal plasma T3 levels, which is achieved through coordination of T4-to-T3 conversion between thyrotrophs and tanycytes.  相似文献   
44.
The need for daily parenteral administration is an important limitation in the clinical use of pentavalent antimonial drugs against leishmaniasis. In this study, amphiphilic antimony(V) complexes were prepared from alkylmethylglucamides (L8 and L10, with carbon chain lengths of 8 and 10, respectively), and their potential for the oral treatment of visceral leishmaniasis (VL) was evaluated. Complexes of Sb and ligand at 1:3 (SbL8 and SbL10) were obtained from the reaction of antimony(V) with L8 and L10, as evidenced by elemental and electrospray ionization-tandem mass spectrometry (ESI-MS) analyses. Fluorescence probing of hydrophobic environment and negative-staining transmission electron microscopy showed that SbL8 forms kinetically stabilized nanoassemblies in water. Pharmacokinetic studies with mice in which the compound was administered by the oral route at 200 mg of Sb/kg of body weight indicated that the SbL8 complex promoted greater and more sustained Sb levels in serum and liver than the levels obtained for the conventional antimonial drug meglumine antimoniate (Glucantime [Glu]). The efficacy of SbL8 and SbL10 administered by the oral route was evaluated in BALB/c mice infected with Leishmania infantum after a daily dose of 200 mg of Sb/kg for 20 days. Both complexes promoted significant reduction in the liver and spleen parasite burdens in relation to those in the saline-treated control group. The extent of parasite suppression (>99.96%) was similar to that achieved after Glu given intraperitoneally at 80 mg of Sb/kg/day. As expected, there was no significant reduction in the parasitic load in the group treated orally with Glu at 200 mg of Sb/(kg day). In conclusion, amphiphilic antimony(V) complexes emerge as an innovative and promising strategy for the oral treatment of VL.  相似文献   
45.
46.
47.
Thymectomy by partial sternotomy for the treatment of myasthenia gravis   总被引:5,自引:0,他引:5  
BACKGROUND: Myasthenia gravis is an autoimmune disease characterized by weakness and fatigue of voluntary muscles. Surgical treatment of choice for myasthenia gravis has been thymectomy. However, thymectomy indications and surgical approach are still controversial. The purpose of this study is to evaluate the efficacy of partial median sternotomy approach to the thymus. METHODS: From 1973 to 1999, 478 patients with myasthenia gravis underwent thymectomy through a partial median sternotomy. RESULTS: Sixty-one patients (12.7%) had complete remission of symptoms, 299 (62.5%) had a significant improvement, and 83 (17.4%), a mild improvement; whereas 35 patients (7.4%) had no improvement of clinical symptoms. CONCLUSIONS: Partial median sternotomy has shown to be a useful surgical approach to the thymus, as demonstrated by the good functional and aesthetic results, associated with low morbidity and no mortality.  相似文献   
48.
This study was to evaluate specific effects of photodynamic therapy (energy density 15.8 J/cm2, 26.3 J/cm2 and 39.5 J/cm2) using methylene blue, toluidine blue and malachite green as photosensitizers and low-power laser irradiation on the viability of Candida albicans. Suspensions of C. albicans containing 106 cells/ml were standardized in a spectrophotometer. For each dye, 120 assays, divided into four groups according to the following experimental conditions, were carried out: laser irradiation in the presence of the photosensitizer; laser irradiation only; treatment with the photosensitizer only; no exposure to laser light or photosensitizer. Next, serial dilutions were prepared and seeded onto Sabouraud dextrose agar for the determination of the number of colony-forming units per milliliter (CFU/ml). The results were subjected to analysis of variance and the Tukey test (P < 0.05). Photodynamic therapy using the photosensitizers tested was effective in reducing the number of C. albicans.. The number of CFU/ml was reduced by between 0.54 log10 and 3.07 log10 and depended on the laser energy density used. Toluidine blue, methylene blue and malachite green were effective photosensitizers in antimicrobial photodynamic therapy against C. albicans, as was low-power laser irradiation alone.  相似文献   
49.
We investigated the expression of nitric oxide synthase (NOS) isoforms -1, -2 and -3 in the retina and optic nerve head (ONH) in an experimental rat model of elevated intraocular pressure (IOP) before and after treatment with timolol, to assess whether its neuroprotective action is associated with the activity of these enzymes. Episcleral vein cauterization in unilateral eyes of Wistar rats was performed to produce elevated IOP. Histological sections of retina and ONH from animals with normal IOP, with elevated IOP, and elevated IOP treated with timolol, were studied by immunohistochemistry with antibodies to NOS-1, NOS-2, and NOS-3. In the control rats, NOS-1 was localized to photoreceptor inner segments, amacrine cells and bipolar cells in the retina, and in astrocytes, pericytes and vascular nitrergic terminals in the ONH. NOS-3 immunostaining localized to the endothelial cells. The rats with elevated IOP showed increased expression of NOS-1 in the plexiform layers of the retina and reactive astrocytes in the ONH. These cells also showed NOS-2 positivity. The rats treated with timolol showed reduced expression of NOS-1 in the retina and ONH. NOS-2 was only detected in a few groups of astrocytes in the ONH. NOS-3 was unchanged in both elevated IOP and timolol-treated groups. These results show that excessive levels of NO synthesized by the NOS-1 and -2 isoforms, considered neurotoxic, might contribute to the progressive lesions of retinal ganglion cell axons. Their reduction after treatment suggests a possible neuroprotective effect of timolol in neurons exposed to excessive amounts of NO.  相似文献   
50.

Introduction

The use of elderly donors can increase the pool of organs available for transplant. The aim of this study was to analyze the outcomes of grafts from donors older than 75 years.

Patients and methods

We selected 29 patients transplanted from January 2003 to January 2010 with livers from donors older than 75 years for comparison with a control group (58 patients), selected among patients transplanted immediately before or after each study case. Data analyzed using SPSS 15.0 were considered statistically significant at P < .05.

Results

Statistically significant differences were evident in the mean age of donors (78.3 ± 2.9 vs 50.4 ± 17.8 years, P < .001), levels of aspartate aminotransferase alanine aminotransferase (30.8 ± 18.13/24.9 ± 14.4 vs 53.81 ± 68.4/39.37 ± 39.94 U/L, P < .05), and waiting list time of (122.4 ± 94.3 vs 169.2 ± 135.5 days, P = .034) of elderly donor versus control graft cohorts. The median follow-up was 32 months (range: 4-88.0) No differences were observed at 1 and 3 years after transplantation: graft survival was 78% and 61% in the older donor group and 83% and 71% in the younger donor group, respectively.

Conclusion

The use of expanded donors from elderly subjects can increase the donor pool with good results.  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