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   2887篇
  免费   135篇
  国内免费   9篇
耳鼻咽喉   28篇
儿科学   491篇
妇产科学   56篇
基础医学   278篇
口腔科学   35篇
临床医学   175篇
内科学   551篇
皮肤病学   81篇
神经病学   129篇
特种医学   73篇
外科学   464篇
综合类   59篇
预防医学   117篇
眼科学   84篇
药学   152篇
中国医学   6篇
肿瘤学   252篇
  2023年   22篇
  2022年   28篇
  2021年   60篇
  2020年   35篇
  2019年   59篇
  2018年   90篇
  2017年   46篇
  2016年   85篇
  2015年   61篇
  2014年   102篇
  2013年   131篇
  2012年   208篇
  2011年   197篇
  2010年   141篇
  2009年   82篇
  2008年   154篇
  2007年   138篇
  2006年   129篇
  2005年   120篇
  2004年   98篇
  2003年   113篇
  2002年   100篇
  2001年   82篇
  2000年   78篇
  1999年   64篇
  1998年   29篇
  1997年   16篇
  1996年   19篇
  1995年   16篇
  1994年   21篇
  1993年   9篇
  1992年   48篇
  1991年   51篇
  1990年   32篇
  1989年   29篇
  1988年   26篇
  1987年   28篇
  1986年   28篇
  1985年   30篇
  1984年   19篇
  1983年   13篇
  1981年   21篇
  1979年   15篇
  1978年   16篇
  1977年   25篇
  1976年   26篇
  1975年   10篇
  1974年   11篇
  1973年   8篇
  1968年   8篇
排序方式: 共有3031条查询结果,搜索用时 0 毫秒
71.
Kudva GC  Maliekel K  Kim HJ  Naunheim KS  Stolar C  Fletcher JW  Puri S 《Chest》2002,121(6):2061-2063
We present the case of a 42-year-old woman with myotonic dystrophy and thymoma. She was treated with combination chemotherapy followed by external beam radiation, and remains in remission 19 months after thymoma was diagnosed. The myotonic dystrophy is unchanged. Only six cases of this nature have been reported in the literature, and this patient is the first to be successfully treated with combined modality therapy.  相似文献   
72.
73.
74.

Purpose

Pulmonary hypoplasia (PH), characterized by alveolar immaturity, remains the main cause of neonatal mortality and long-term morbidity in infants with congenital diaphragmatic hernia (CDH). Lipid-containing interstitial fibroblasts (LIFs) are critically important for normal alveolar development. Thymocyte antigen 1 (Thy-1) is a highly expressed cell-surface protein in this specific subset of lung fibroblasts, which plays a key role in fetal alveolarization by coordinating the differentiation and lipid homeostasis of alveolar LIFs. Thy-1 increases the lipid content of LIFs by upregulation of adipocyte differentiation-related protein (ADRP), a lipogenic molecular marker characterizing pulmonary LIFs. Thy-1 ?/? mice further show impaired alveolar development with reduced proliferation of pulmonary LIFs, resulting in a PH-similar phenotype. We hypothesized that pulmonary Thy-1 signaling is disrupted in experimentally induced CDH, which may has an adverse effect on the lipid content of alveolar LIFs.

Methods

Timed-pregnant Sprague–Dawley rats were treated with either 100 mg nitrofen or vehicle on embryonic day 9.5 (E9.5). Fetuses were killed on E21.5, and lungs were divided into controls (n = 14) and CDH-associated PH (n = 14). Pulmonary gene expression levels of Thy-1 and ADRP were assessed by quantitative real-time PCR. ADRP immunohistochemistry and oil-red-O staining were used to localize alveolar LIF expression and lipid droplets. Immunofluorescence double staining for Thy-1 and oil-red-O was performed to evaluate Thy-1 expression and lipid content in alveolar LIFs.

Results

Radial alveolar count was significantly reduced in CDH-associated PH with significant downregulation of pulmonary Thy-1 and ADRP mRNA expression compared to controls. ADRP immunoreactivity and lipid droplets were markedly diminished in alveolar interstitial cells, which coincided with decreased alveolar LIF expression in CDH-associated PH compared to controls. Confocal laser scanning microscopy confirmed markedly decreased Thy-1 expression and lipid content in alveolar LIFs of CDH-associated PH compared to controls.

Conclusion

Our study provides strong evidence that disruption of pulmonary Thy-1 signaling results in reduced lipid droplets in alveolar LIFs and may thus contribute to PH in the nitrofen-induced CDH model. Treatment modalities aimed at increasing lipid content in alveolar LIFs may therefore have a therapeutic potential in attenuating CDH-associated PH.  相似文献   
75.
India affords special laws and exemptions to minors under the criminal, marriage, labour and administrative laws. Many perpetrators claim to be a minor in the hope of a lenient trial and verdict. The authorities often rely upon forensic experts to provide evidence-based reports. The third molar can be relied upon in the assessment of legal age as it continues developing into the early twenties. The method established by Cameriere et al in 2008 provides an objective method for the accurate evaluation of legal age. Our study was designed to analyze and validate the efficacy of Third Molar Maturity index (I3M) in an Indian Goan population and compare it to published literature. 542 panoramic radiographs of subjects aged between 14 and 24 years were evaluated. The chronologic age increased as I3M reduced. There was no evidence of sexual dimorphism in third molar development across various I3M classes (p>0.05). Receiver Operator Characteristic Curve was plotted for males and females which showed an Area Under Curve of 0.95 (95% CI, 0.92-0.97) and 0.93 (95% CI, 0.90-0.96) respectively. 2x2 contingency tables were used to test the performance of various I3M cut-off values ranging from I3M=0.02 to 0.14. I3M = 0.08 showed the most promising results for the assessment of legal age. Our study achieved a high degree of accurate classification of 0.90 and 0.88 for males and females respectively. Results demonstrate a sensitivity of 0.899 and 0.854 and specificity of 0.90 and 0.93 for males and females respectively. The positive likelihood ratios were 9.88 and 12.44 while negative likelihood ratio was 0.11 and 0.15 for males and females respectively. A favourable Bayes Post Test Probability of 0.95 was noted for both males and females. These results allow us to strongly recommend the use of I3M for the assessment of legal age in an Indian Goan population.  相似文献   
76.
We have evaluated the effect of variation in aryl-tetralin lignans on the radioprotective properties of Podophyllum hexandrum. Two fractionated fractions of P. hexandrum [methanolic (S1) and chloroform fractions (S2)], with varying aryl-tetralin lignan content were utilized for the present study. The peroxyl ion scavenging potentials of S1 and S2 were found to be comparable [i.e. 45.88% (S1) and 41% (S2)] after a 48 h interval in a time-dependent study, whereas in a 2 h study, S2 exhibited significant (P < 0.05) antioxidant activity in different metal ion + flux states. In the aqueous phase, S2 exhibited non-site-specific reactive oxygen species scavenging activity, i.e. 73.12% inhibition at 500 mug ml(-1). S1 exhibited 58.40 +/- 0.8% inhibition (at 0.025 mug ml(-1)) of the formation of reactive nitrite radicals, comparable to S2 (52.45 +/- 0.825%), and also showed 45.01% site-specific activity (1000 mug ml(-1)), along with significant (P < 0.05) electron donation potential (50-2000 mug ml(-1)) compared to S2. Such activities of S1 could be attributed to the significantly (P < 0.05) higher levels of podophyllotoxin beta-d-glucopyranoside (16.5 times) and demethyl podophyllotoxin glucoside (2.9 times) compared with S2. Together, these findings clearly prove that aryl-tetralin lignan content influences the radiation protective potential of the Podophyllum fractions to a great extent.  相似文献   
77.
78.
New observations on the pathogenesis of multiple intestinal atresias   总被引:2,自引:0,他引:2  
It has been suggested that multiple intestinal atresias result from multiple ischemic infarctions of the intestinal tract. We have studied surgical material from 59 neonates with intestinal atresias seen at our hospital between 1975 and 1986. Forty (68%) patients had single intestinal atresias and 19 (32%) had multiple atresias. There were seven cases of hereditary multiple atresias seen in three families and 12 cases of nonhereditary multiple atresias. All hereditary cases had numerous type I or type II gastrointestinal atresias but none had type IIIa atresia. Six of the seven hereditary cases had multiple atresias in the small as well as large bowel. The 12 patients with nonhereditary atresias had various types of atresias but mesenteric or intestinal interruption was observed in only two patients. All patients with hereditary multiple intestinal atresias showed identical microscopic appearances in the small and large intestine, consisting of sieve-like multiple lumina, each surrounded by its own mucosa and muscularis mucosae but sharing a common muscle coat. There was no evidence of lanugo, bile pigments, or squames within the lumen distal to atretic segments in any of these patients. Six nonhereditary cases who had multiple septal atresias affecting only the small bowel demonstrated essentially similar lesions on microscopic examination as seen in hereditary cases. There was no evidence of arterial occlusion in the mesentery and lanugo, bile pigments, and squames could not be found distally in the intestinal contents in any of these cases. These pathologic findings suggest that all cases of hereditary multiple intestinal atresias and some cases of nonhereditary multiple intestinal atresias are a consequence of a malformative process of the gastrointestinal tract rather than an ischemic process.  相似文献   
79.
A 45-year-old woman with livid plaques showing central atrophy and erythematous vesicular borders over both dorsa of feet and buttocks, and follicular and papular lesions over buttocks and lumbar area, was difficult to diagnose as either lichen planus (LP) or lupus erythematosus (LE). The histological studies from two places showed features of both LE and LP. Laboratory findings were within normal limits first, but follow up studies for two years showed persistent albuminurea, leucopenia, arthritis and erythema over the exposed areas with same histology suggesting that eruption may be an unusual variant of LE.  相似文献   
80.
Although malignant melanoma is rare in children, its incidence is steadily increasing, and it is potentially lethal. Few studies have examined head and neck melanoma in children, and even fewer have focused on the histopathologic features of melanoma within this anatomic region. To further the understanding of this entity, we examined pathology specimens from nine subjects age 18 years and younger with an original diagnosis of head or neck melanoma. The anatomic locations of these primary melanomas were the face and nose (n = 4), scalp and neck (n = 4), and ear (n = 1). The cases included seven superficial spreading melanomas, one unclassified (possible nodular) melanoma, and one melanoma in situ. No melanomas demonstrating desmoplastic or spindle cell morphologies were noted upon review. Breslow depth ranged from 0 to 2.9 mm (mean 1.3 mm, median 0.6 mm), with Clark level ranging from I to V. Pagetoid scatter was found in eight cases. Other notable features included regression (n = 5), ulceration (n = 1), and associated melanocytic nevus (n = 4). We did not observe any small cell variants; all nine cases had an epithelioid appearance. Nor was any melanoma‐associated mortality observed at last follow‐up (mean 60.4 mos, median 48 mos, range 2–174 mos). These histopathologic features were consistent with adult‐type melanoma, which is in agreement with other histopathologic studies of melanoma in children.  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