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   4781篇
  免费   264篇
  国内免费   28篇
耳鼻咽喉   60篇
儿科学   93篇
妇产科学   93篇
基础医学   473篇
口腔科学   142篇
临床医学   334篇
内科学   991篇
皮肤病学   134篇
神经病学   168篇
特种医学   295篇
外国民族医学   4篇
外科学   1105篇
综合类   120篇
一般理论   4篇
预防医学   316篇
眼科学   114篇
药学   335篇
中国医学   24篇
肿瘤学   268篇
  2024年   2篇
  2023年   45篇
  2022年   151篇
  2021年   251篇
  2020年   136篇
  2019年   202篇
  2018年   196篇
  2017年   120篇
  2016年   154篇
  2015年   170篇
  2014年   258篇
  2013年   268篇
  2012年   374篇
  2011年   432篇
  2010年   248篇
  2009年   185篇
  2008年   297篇
  2007年   329篇
  2006年   269篇
  2005年   224篇
  2004年   188篇
  2003年   193篇
  2002年   152篇
  2001年   29篇
  2000年   29篇
  1999年   31篇
  1998年   15篇
  1997年   10篇
  1996年   16篇
  1995年   9篇
  1994年   7篇
  1993年   3篇
  1992年   5篇
  1991年   6篇
  1990年   4篇
  1989年   3篇
  1988年   9篇
  1987年   5篇
  1986年   2篇
  1984年   5篇
  1981年   4篇
  1980年   2篇
  1979年   3篇
  1976年   7篇
  1975年   3篇
  1974年   3篇
  1973年   4篇
  1972年   4篇
  1969年   3篇
  1921年   1篇
排序方式: 共有5073条查询结果,搜索用时 31 毫秒
91.
Several organic and functional disorders of the urinary bladder, reproductive tract, anorectum, and the pelvic floor musculature cause pelvic pain. This article describes functional disorders in which chronic pelvic and anorectal pain cannot be explained by a structural or other specified pathology. Currently, these functional disorders are classified into urogynecologic conditions or cystitis and painful bladder syndrome, anorectal disorders, and the levator ani syndrome. Although nomenclature suggests that these conditions are distinct, there is considerable overlap of their symptoms and these disorders have much in common.  相似文献   
92.
A 38-year-old man underwent coronary artery bypass graft surgery for angina pectoris following myocardial infarction. During the following 28 years, he required two repeat coronary artery bypass graft surgical procedures, nine percutaneous coronary interventions and 17 coronary angiograms. His treatment included saphenous vein, left internal mammary artery and gastroepiploic artery grafting, percutaneous transluminal coronary angioplasty and intragraft thrombolytic therapy, directional coronary atherectomy, cutting balloon angioplasty, intracoronary stenting with bare-metal and drug-eluting stents, treatment for in-stent restenosis, stenting of the left main and circumflex coronary arteries and saphenous vein graft as well as intracoronary pressure wire diagnostics. In addition to his statin therapy, antiplatelets and angiotensin-converting enzyme inhibitors, he also underwent biventricular automatic implantable cardioverter-defibrillator implantation and atrioventricular node radiofrequency ablation for his impaired left ventricular function, ventricular tachycardia and rapid atrial fibrillation. The present unusual case represents almost 'the whole nine yards' of treatment that has become available to patients with coronary artery disease during the past 30 years of technological development.  相似文献   
93.
Epidemiological studies in the developing world are frequently biased by the simultaneous presence of several infectious pathogens. In the present study, we examined the usefulness of circulating markers of oxidative stress and liver fibrosis to investigate the distinct forms of chronic liver inflammations associated with schistosomiasis and viral hepatitis, respectively. The study was performed in a Sudanese population exposed to Schistosoma. Circulating hyaluronic acid (HA) was used as a marker of liver fibrosis; the severity of schistosomiasis was determined by ultrasonic examination; viral hepatitis infection was ascertained by circulating anti-hepatitis antibodies. Serum markers were examined also in Sudanese subjects not exposed to Schistosoma infection and in French control subjects. We found a drastic decrease of lycopene levels in the subjects exposed to schistosomiasis in comparison with non-exposed Sudanese and French control subjects. Retinol, alpha-tocopherol and five carotenoids were unchanged. Lycopene depletion was unlikely to be due to variations of nutritional origin, since the lycopene/beta-carotene ratio was five-fold lower in the population at risk of schistosomiasis than in the other groups. We found that high HA serum levels were associated with severe periportal fibrosis but not with viral infection. Conversely, levels of the oxidized lipid malondialdehyde (MDA) were associated with viral infection but not with the severity of schistosomiasis, even though the two infections had additive effects. We concluded that serum markers are valuable tools for investigating the complex effects of co-existing factors of chronic liver inflammation.  相似文献   
94.
95.
Manual assessment of estrogen receptors′ (ER) status from breast tissue microscopy images is a subjective, time consuming and error prone process. Automatic image analysis methods offer the possibility to obtain consistent, objective and rapid diagnoses of histopathology specimens. In breast cancer biopsies immunohistochemically (IHC) stained for ER, cancer cell nuclei present a large variety in their characteristics that bring various difficulties for traditional image analysis methods. In this paper, we propose a new automatic method to perform both segmentation and classification of breast cell nuclei in order to give quantitative assessment and uniform indicators of IHC staining that will help pathologists in their diagnostic. Firstly, a color geometric active contour model incorporating a spatial fuzzy clustering algorithm is proposed to detect the contours of all cell nuclei in the image. Secondly, overlapping and touching nuclei are separated using an improved watershed algorithm based on a concave vertex graph. Finally, to identify positive and negative stained nuclei, all the segmented nuclei are classified into five categories according to their staining intensity and morphological features using a trained multilayer neural network combined with Fisher's linear discriminant preprocessing. The proposed method is tested on a large dataset containing several breast tissue images with different levels of malignancy. The experimental results show high agreement between the results of the method and ground-truth from the pathologist panel. Furthermore, a comparative study versus existing techniques is presented in order to demonstrate the efficiency and the superiority of the proposed method.  相似文献   
96.
97.
The aim of this study was to evaluate the quality of B cell responses in patients with Inflammatory Bowel Disease (IBD) and healthy individuals of different ages, vaccinated with the pandemic (p)2009 influenza vaccine. The in vivo response was measured by the hemagglutination inhibition (HAI) assay, which represents the most established correlate with vaccine protectiveness. The in vitro response was measured by activation-induced cytidine deaminase (AID) in cultures of vaccine-stimulated PBMC. Both responses are somewhat impaired in IBD patients undergoing anti-TNF-α treatment but these are much more decreased in IBD patients undergoing treatment with anti-TNF-α and immunosuppressive (IS) drugs. These latter patients had in vivo and in vitro B cell responses similar to those of elderly individuals. Moreover, as we have previously demonstrated in healthy subjects, the in vitro response to the polyclonal stimulus CpG may be used as a biomarker for subsequent vaccine response and AID activation is correlated with the serum response in IBD patients, as it is in healthy individuals. These results altogether indicate that IBD patients on anti-TNF-α and IS have significantly impaired in vivo and in vitro B cell responses, as compared to those on monotherapy. This is the first report to demonstrate that B cell defects, as measured by the autonomous AID reporter, in IBD patients contribute to reduced humoral responses to the influenza vaccine, as we have previously shown for elderly individuals.  相似文献   
98.
Poly(methyl methacrylate-glycidyl methacrylate) [Poly(MMA-GMA)] cryogels were synthesized using monomers of methylmethacrylic acid and epoxy group bearing GMA via radical cryopolymerization technique. Synthesized cryogels were used for the immobilization of amyloglucosidase to the cryogel surface using epoxy chemistry. Characterizations of the free and immobilized amyloglucosidase were carried out by comparing the optimum and kinetic parameters of enzymes. For this, pH and temperature profiles of free and immobilized preparation were studied and, it was found that, optimum pH of enzyme was not change upon immobilization (pH 5.0), while optimum temperature of the enzyme shifted 10 °C to warmer region after immobilization (optimum temperatures for free and immobilized enzyme were 55 and 65 °C, respectively). Kinetic parameters of free and immobilized enzyme were also investigated and Km values of free and immobilized amyloglucosidase were found to be 2.743 and 0.865 mg/mL, respectively. Vmax of immobilized amyloglucosidase was found to be (0.496 µmol/min) about four times less than that of free enzyme (2.020 µmol/min). Storage and operational stabilities of immobilized amyloglucosidase were also studied and it was showed that immobilized preparation had much more stability than free preparation. In the present work, amyloglucosidase immobilized poly(MMA-GMA) cryogels were used for continuous glucose syrup production from starch for the first time. Efficiency of immobilized enzyme was investigated and released amount of glucose was found to be 2.54 mg/mL at the end of the 5 min of hydrolysis. The results indicate that the epoxy functionalized cryogels offer a good alternative for amyloglucosidase immobilization applications with increased operational and thermal stability, and reusability. Also, these cryogels can be used for immobilization of other industrially valuable enzymes beyond amyloglucosidase.  相似文献   
99.
Canine hepatozoonosis is a worldwide protozoal disease caused by Hepatozoon canis and Hepatozoon americanum and is transmitted by ixodid ticks, Rhipicephalus and Amblyomma spp., respectively. H. canis infection is widespread in Africa, Europe, South America, and Asia, including Japan. The objective of this study was to study the distribution pattern and diversity of H. canis in naturally infected dogs in nine Japanese islands and peninsulas. Therefore, 196 hunting dogs were randomly sampled during the period from March to September 2011 and the ages and sexes were identified. Direct microscopy using Giemsa-stained blood smears revealed H. canis gametocytes in the peripheral blood of 45 (23.6 %) dogs. Polymerase chain reaction (PCR) was performed on EDTA-anticoagulated blood, initially with the common primer set (B18S-F and B18S-R) amplifying the 1,665-bp portion of the 18S rRNA gene, and then with the specific primer set (HepF and HepR) amplifying about 660 bp fragments of the same gene. Based on PCR, 84 (42.9 %) dogs were positive using the common primer and 81 (41.3 %) were positive using the specific primer. The current investigation indicated that all screened areas, except for Sado Island and Atsumi Peninsula, were infected. Yaku Island had the highest infection rate (84.6 % in males and 100.0 % in females), while Ishigaki Island showed the lowest infection rates (8.3 % in males and 17.7 % in females). Both sexes were infected with no significant difference. However, diversity of infection among the surveyed islands and peninsulas was significantly different (P?<?0.05). Although H. canis has previously been reported in dogs in Japan, the higher infection rate described in the current study and the diversity of infection in a wide range of islands strongly encourage prospective studies dealing with the prevention and treatment of the infection in dogs, as well as control of ticks.  相似文献   
100.
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