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   6315篇
  免费   478篇
  国内免费   32篇
耳鼻咽喉   66篇
儿科学   94篇
妇产科学   148篇
基础医学   1127篇
口腔科学   705篇
临床医学   424篇
内科学   1100篇
皮肤病学   143篇
神经病学   506篇
特种医学   253篇
外科学   509篇
综合类   58篇
一般理论   1篇
预防医学   692篇
眼科学   58篇
药学   490篇
中国医学   59篇
肿瘤学   392篇
  2024年   8篇
  2023年   52篇
  2022年   135篇
  2021年   187篇
  2020年   131篇
  2019年   182篇
  2018年   255篇
  2017年   166篇
  2016年   201篇
  2015年   211篇
  2014年   312篇
  2013年   346篇
  2012年   486篇
  2011年   566篇
  2010年   283篇
  2009年   227篇
  2008年   389篇
  2007年   407篇
  2006年   296篇
  2005年   315篇
  2004年   266篇
  2003年   242篇
  2002年   192篇
  2001年   138篇
  2000年   127篇
  1999年   120篇
  1998年   73篇
  1997年   45篇
  1996年   27篇
  1995年   26篇
  1994年   29篇
  1993年   30篇
  1992年   54篇
  1991年   38篇
  1990年   38篇
  1989年   28篇
  1988年   30篇
  1987年   13篇
  1986年   17篇
  1985年   16篇
  1984年   10篇
  1983年   8篇
  1982年   14篇
  1981年   7篇
  1980年   8篇
  1979年   13篇
  1975年   6篇
  1974年   7篇
  1973年   6篇
  1971年   6篇
排序方式: 共有6825条查询结果,搜索用时 15 毫秒
61.
Myofibroma (MF) is a benign mesenchymal myofibroblast-derived tumor, which occurs most frequently in children, and rarely affects the maxilla. We reported a case of an aggressive intraosseous lesion found in the maxilla of a 9-year-old female child. Intraorally, the swelling extended from tooth 12 to 16, causing displacement of teeth 13, 14, and 15. Computed tomography revealed a large osteolytic lesion causing thinning and cortical erosion. Microscopically, the lesion showed a proliferation of spindle-shaped cells, with elongated nuclei and eosinophilic cytoplasm, arranged in interlaced fascicles. The immunohistochemical analysis revealed cytoplasmic positivity for α-SMA and HHF-35, and negativity for desmin, laminin, S-100, β-catenin, and CD34. Ki-67 was positive in 8% of tumor cells. The diagnosis was MF. Herein, we describe an additional case of central MF arising in the maxilla, including clinical, imaging, microscopical, and immunohistochemical features, as well as a review of the literature.  相似文献   
62.
Pseudoangiosarcomatous squamous cell carcinoma, also called pseudovascular, pseudoangiomatoid or adenoid pseudovascular carcinoma, is an uncommon and highly aggressive variant of squamous cell carcinoma. Histologically, it is characterized by proliferation of atypical keratinocytes with acantholysis and formation of pseudovascular spaces, forming anastomosed channels lined with neoplastic cells that invade the dermis. These cells are positive for cytokeratin and negative for vascular markers such as CD31 and CD34. There are few reports of this variant in the literature. Skin, breast, lung and vulva involvement have been described, but to the best of our knowledge, no cases involving the penis has been described. This study aims to describe the first case of angiosarcomatous squamous cell carcinoma of the penis. The patient presented with a painful lesion in the penis associated with urinary retention. Macroscopic findings exhibited an ulcerative vegetating lesion that involving the entire glans and part of the penile body, as well as infiltration of penile structures and scrotal skin. Microscopy shows atypical proliferation of sarcomatous keratinocyte pattern mimicking vascular spaces. Human papilloma virus (HPV) biomarkers and polymerase chain reaction (PCR) were all negative. Advanced penile squamous cell carcinoma with aggressive lymph node metastasis. This report presents the first case of penile pseudoangiosarcomatous squamous cell carcinoma, as an important differential diagnosis.  相似文献   
63.
Diagnosis of metastatic lesions to the stomach by salvage cytology   总被引:1,自引:0,他引:1  
Summary Secondary neoplasms of the stomach are rare and are often clinical and diagnostic problems. Three patients with bleeding volcano-like ulcers were diagnosed by combined endoscopic salvage cytology and surgical biopsy as having metastatic submucosal lesions from hematologic spread. The combination of endoscopic appearance, clinical findings, and tissue and cytologic examination can lead to the correct diagnosis. The results from these cases support the utility of this cytologic technique in combination with biopsy in this clinical setting.  相似文献   
64.
Egg and bone of passerine birds nesting in acidified habitats may be affected by high levels of Al or P, or low levels of Ca. Nine treatments of three levels of dietary Al (target levels of 200, 1,000, and 5,000 g/g) and three levels of Ca:P (target levels of NN = 1.3% Ca: 0.9% P; LL = 0.19 Ca:0.45 P; LH = 0.19 Ca: 1.65 P) were fed to 16–17 starling pairs during two breeding seasons. Eggs of starlings fed the LH diet were smaller and weighed less than eggs from the NN and LL treatments. Treatment effects on thickness, strength, and weight of eggshells were not consistent between seasons, probably because of differences in actual dietary levels of Al, Ca, and P or in incubation intervals. In one season, birds fed the highest Al diet had thicker eggshells than those from the other Al treatments (no effect from Ca:P); the following season, eggshells from the NN and LH treatments were thicker and stronger than those from the LL treatment. Eggshells from the NN treatment weighed more than those from the other Ca:P treatments. Starlings on the LH diet had the strongest femurs, but the effect was interactive with different levels of dietary Al. Effects of Ca:P on egg and bone were more evident than Al effects.  相似文献   
65.
66.
Several techniques have been developed to assess the ecotoxicity of contaminated watercourses. Most of these techniques involve chemical alterations of water samples, by diluting it or by adding chelating agents. These changes become particularly severe when assessing the toxicity of samples with very low pH and with high quantities of contaminants. Trying to overcome this problem, a novel toxicity test, specific for acid waters, was previously developed and field validated. The toxicity of acid samples is assessed using the survival time of Ceriodaphnia dubia. During this study, the novel test was applied to a field situation, where an aquatic system is seriously impacted with acid mine drainage. Its efficiency was tested and compared with two classical toxicity tests: the Microtox and the median lethal dilution with C. dubia. The survival time test was performed without adjusting pH and after adjusting pH to a fixed value (pH 2, 3, and 4). At pH 2 and 4 no acceptable results were obtained; at pH 3 it was possible to distinguish the toxicity due to pH from the toxicity due to other toxicants. The test conducted at local pH was able to discriminate toxicity sources only for highly contaminated samples. The toxicity evaluation of acid mine drainage samples was possible neither with the median lethal dilution test nor with Microtox.  相似文献   
67.
This study developed a bioassay with the isopod Porcellio dilatatus based on the activity of the enzymes acetylcholinesterase (AChE) and lactate dehydrogenase (LDH). The in vivo effects of the insecticides parathion-ethyl and endosulfan-sulfate on AChE and LDH activities of P. dilatatus under laboratory conditions were investigated. The route of uptake of the pesticides was through the food (alder leaves). Isopods were exposed to a wide range of concentrations of parathion or endosulfan (0.1, 1, 10, 25, 50, 100, 250, and 500 microg/g of food) for 21 days. After this period, the activity of AChE and LDH was determined. Parathion induced significant depression of both AChE and LDH activities. Animals fed with endosulfan-contaminated food exhibited lower LDH activities than control animals, while AChE activity was similar in all treatments. The results of the present investigation suggest that the isopod. P. dilatatus is a suitable species for use in toxicity tests and indicate that the enzymes AChE and LDH could be used as effect criteria both in laboratory and in field studies with this species.  相似文献   
68.
Signs of overuse after intense muscular exertion are well described in adults, while little research has been conducted in children. The aim of the study was to investigate some indirect markers of muscle damage in 13 years old boys following two different protocols of one-leg stepping exercise to exhaustion. This stepping exercise was performed by two experimental groups with different contributions of concentric and eccentric contractions in a 1:1 vs 1:2 ratio of timing. Subjective soreness perception and maximum voluntary isometric force of the knee extensor muscles were measured immediately prior to and immediately following the exercise, and at 1, 3, 24, 48, 72, 96 hours post exercise. Metabolic markers of exercise stress were taken at similar time intervals and included plasma glutathione concentrations as a marker for oxidative stress, circulating leukocyte numbers, and plasma creatine kinase (CK) activity. All parameters studied demonstrated a higher level of muscular exertion, with more evident signs of overuse in the group with the more eccentric contribution. Complete recovery was achieved between 72 and 96 hours after exertion. However, in this group of boys, the CK activity did not show the typical adult-like increase. Therefore the wide use of CK as an indicator of intense muscle exertion was not supported in this group of children. It can be concluded that children, like adults, experience similar degrees of muscle disturbances following intense exercise and that they may recover more quickly from such exercise.  相似文献   
69.
Dizziness is a frequent complaint during the initial worsening of panic patients treated with clomipramine. In order to investigate the relationship between dizziness and initial worsening mechanisms, otoneurological tests were administered to 32 consecutive patients with panic disorder, with or without agoraphobia, before treatment, 36 h after the first dose of 25 mg clomipramine and after treatment and full remission of the panic and agoraphobic symptoms. A pretreatment complaint of 'dizziness during panic attacks' but not the occurrence of otoneurological abnormalities, predicted the occurrence of clinical worsening at the start of treatment. A specific pattern of otoneurological abnormalities was not found, but only three patients had normal results in all three sessions. The inconsistent test results suggest that functional vestibular pathology is frequently associated with panic disorder.  相似文献   
70.
The role of risk management is vitally important in the hospital. As institutions grow and the field of health care advances into the future, the number of patient-associated risks will continue to multiply. In response, the Joint Commission has changed its policies to reflect the importance of patient outcomes. This new Joint Commission focus, coupled with the increasing number of patient risks, will create the need for health care professionals to recognize their role in risk management. In anticipation of the future, pharmacy has been guiding itself toward that role for some time. With a large portion of the profession participating in activities such as DUE and QA programs, pharmacists can be a useful resource to the risk manager. Participation in retrospective analysis such as ADRs and peer review committees also aids the pharmacy profession in establishing guidelines that will decrease future patient risks. Future trends in drug development will increase the pharmacist's role in drug selection, in an effort to ensure both safety and cost containment. The profession's continuing development and implementation of practice standards will ensure that pharmacy remains dedicated to improving patient outcomes and decreasing patient risks. In addition, by learning to use the risk manager as both a source of information and a partner in identifying pharmacy-related areas of risk, the pharmacy profession will be able to continue its pursuit of improved quality of patient care.  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