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   6643篇
  免费   478篇
  国内免费   22篇
耳鼻咽喉   20篇
儿科学   246篇
妇产科学   118篇
基础医学   1241篇
口腔科学   77篇
临床医学   753篇
内科学   1332篇
皮肤病学   223篇
神经病学   676篇
特种医学   125篇
外科学   733篇
综合类   37篇
一般理论   2篇
预防医学   352篇
眼科学   74篇
药学   404篇
中国医学   20篇
肿瘤学   710篇
  2023年   40篇
  2022年   69篇
  2021年   96篇
  2020年   95篇
  2019年   119篇
  2018年   150篇
  2017年   112篇
  2016年   139篇
  2015年   164篇
  2014年   183篇
  2013年   286篇
  2012年   460篇
  2011年   501篇
  2010年   275篇
  2009年   291篇
  2008年   455篇
  2007年   536篇
  2006年   467篇
  2005年   500篇
  2004年   464篇
  2003年   430篇
  2002年   401篇
  2001年   65篇
  2000年   38篇
  1999年   65篇
  1998年   80篇
  1997年   80篇
  1996年   69篇
  1995年   63篇
  1994年   56篇
  1993年   36篇
  1992年   21篇
  1991年   25篇
  1990年   21篇
  1989年   24篇
  1988年   28篇
  1987年   22篇
  1986年   13篇
  1985年   14篇
  1984年   16篇
  1983年   16篇
  1982年   22篇
  1981年   8篇
  1980年   19篇
  1977年   7篇
  1975年   9篇
  1974年   9篇
  1973年   7篇
  1971年   8篇
  1968年   7篇
排序方式: 共有7143条查询结果,搜索用时 22 毫秒
31.
A sulfated emodin glucoside, emodin 8-O-beta-D-glucopyranosyl-6-O-sulfate (1), was isolated from the roots of Rheum emodi in an investigation of the active constituents of this Nepalese medicinal plant, and its structure was determined by spectroscopic and chemical methods. Additionally, two rare auronols, carpusin (2) and maesopsin (3), besides other anthraquinones and phenolics, were isolated and identified. Compounds 2 and 3 showed significant antioxidant activity in the DPPH assay, while chrysophanol, physcion, and emodin and their 8-O-glucosides were found to be inactive.  相似文献   
32.
BACKGROUND Patients with skull defects sometimes develop neurological deficits, which have been grouped under “the syndrome of the trephined”. The deficits are usually nonspecific or nonlocalizing, such as apathy or diffuse headaches. We report, to our knowledge, a first case of severe midbrain syndrome associated with a skull defect. Cranioplasty dramatically resolved the patient's symptoms. A midbrain syndrome represents the main manifestation of the syndrome of the trephined and can be corrected by cranioplasty. CLINICAL PRESENTATION A 38-year-old man with head trauma and epidural hematoma initially had normal eye motility. He developed a skull defect after infection following cranioplasty. He presented with onset of neurological symptoms one year after head trauma with a skull defect, a small divergent and vertical strabismus, elevation deficit of both eyes, headaches and fatigue. Over several months he developed severe bilateral deficit of adduction, elevation, depression and convergence. He had neuropsychological deficits, fatigue, headaches and impaired coordination. Neuroimaging and lumbar puncture did not show evidence of increased intracranial pressure or hydrocephalus. INTERVENTION Cranioplasty using Palacos was performed one-and-a-half years after trauma. Immediately after surgery, the patient noted remarkable improvement in his symptoms. Headaches and fatigue disappeared within two days. Two weeks after cranioplasty the patient had orthotropia and virtually normal ocular motility. Neurological symptoms completely disappeared. Recovery remained sustained for over 5 years after cranioplasty. CONCLUSION To our knowledge, this represents the first case of the syndrome of the trephined in which the neurological deficits map primarily to the brainstem and show rapid improvement following cranioplasty. We show that cranioplasty in patients with large skull defects is indicated for more then cosmetic reasons and should be considered even after longer periods following a trauma.  相似文献   
33.
Fetal stroke is an important cause of cerebral palsy but is difficult to diagnose unless imaging is undertaken in pregnancies at risk because of known maternal or fetal disorders. Fetal ultrasound or magnetic resonance imaging may show haemorrhage or ischaemic lesions including multicystic encephalomalacia and focal porencephaly. Serial imaging has shown the development of malformations including schizencephaly and polymicrogyra after ischaemic and haemorrhagic stroke. Recognised causes of haemorrhagic fetal stroke include alloimmune and autoimmune thrombocytopaenia, maternal and fetal clotting disorders and trauma but these are relatively rare. It is likely that a significant proportion of periventricular and intraventricular haemorrhages are of venous origin. Recent evidence highlights the importance of arterial endothelial dysfunction, rather than thrombocytopaenia, in the intraparenchymal haemorrhage of alloimmune thrombocytopaenia. In the context of placental anastomoses, monochorionic diamniotic twins are at risk of twin twin transfusion syndrome (TTTS), or partial forms including Twin Oligohydramnios Polyhydramnios Sequence (TOPS), differences in estimated weight (selective Intrauterine growth Retardation; sIUGR), or in fetal haemoglobin (Twin Anaemia Polycythaemia Sequence; TAPS). There is a very wide range of ischaemic and haemorrhagic injury in a focal as well as a global distribution. Acute twin twin transfusion may account for intraventricular haemorrhage in recipients and periventricular leukomalacia in donors but there are additional risk factors for focal embolism and cerebrovascular disease. The recipient has circulatory overload, with effects on systemic and pulmonary circulations which probably lead to systemic and pulmonary hypertension and even right ventricular outflow tract obstruction as well as the polycythaemia which is a risk factor for thrombosis and vasculopathy. The donor is hypovolaemic and has a reticulocytosis in response to the anaemia while maternal hypertension and diabetes may influence stroke risk. Understanding of the mechanisms, including the role of vasculopathy, in well studied conditions such as alloimmune thrombocytopaenia and monochorionic diamniotic twinning may lead to reduction of the burden of antenatally sustained cerebral palsy.  相似文献   
34.
35.
The dynamics of the subcellular distribution of PLCbeta1 was investigated during meiosis competence acquisition and meiosis resumption in relation to oocyte diameter and to nonsurrounded-nucleolus or surrounded-nucleolus chromatin configurations. Oocytes collected after both in vivo and in vitro folliculogenesis were studied. In both conditions, at the beginning of the process, most oocytes exhibited a nuclear PLCbeta 1 associated with a nonsurrounded-nucleolus chromatin configuration. Then at the final stage of the process, the factors shifted mainly toward a cytoplasmic PLCbeta1 and a surrounded-nucleolus chromatin configuration, typical of a preovulatory fertilizable oocyte. Additionally, only germinal vesicle oocytes with a diameter > 75 microm, and exhibiting cytoplasmic PLC beta1 distribution and surrounded-nucleolus chromatin configuration, resumed meiosis. Our findings demonstrate a strong correlation between oocyte diameter, chromatin configuration, and PLCbeta1 localization. Thus, PLCbeta1 localization appears to be a key factor determining the progressive acquisition of meiotic competence and final resumption of meiosis.  相似文献   
36.
37.
OBJECTIVE: We studied hypophosphatasia (HP) mutations in 19 cases prenatally detected by ultrasonography without familial history of HP. We correlated the mutations with the reported ultrasound signs, and discussed genetic counseling with regard to the particular dominantly inherited prenatal benign form of HP. METHOD: The coding sequence of the tissue nonspecific alkaline phosphatase (TNSALP) gene was analyzed by DNA sequencing, and 3D modeling was used to locate the mutated amino acids with regard to the functional domains of TNSALP. RESULTS: Although reported ultrasound signs were heterogeneous, two mutated alleles were found in 18 of the 19 cases studied, indicating recessive transmission of the disease. Functional domains of TNSALP were affected by 74% of missense mutations. In all the cases, including one with only a heterozygous mutation, molecular, biological, and familial data do not corroborate the hypothesis of prenatal benign HP. The mutation c.1133A>T observed in the prenatal benign form of HP and common in USA was not found in this series. CONCLUSION: The results point out the prenatally detectable allelic heterogeneity of HP. The nature of the detected mutations and the evidence of recessive inheritance do not support these cases being affected with prenatal benign HP.  相似文献   
38.
OBJECTIVE: Cyclic platinum-based intraperitoneal chemotherapy has proven to be effective after optimal surgical cytoreduction in ovarian carcinoma. Hyperthermia is directly cytotoxic and enhances chemotherapy tumoricidal effects. This study was designed to determine the maximum tolerated dose (MTD) of carboplatin used intraoperatively as intraperitoneal hyperthermic chemotherapy (IPHC), the effect on postoperative systemic chemotherapy administration, and the potential for repeat IPHC at second look surgery. METHODS: Using the ThermoChem HT System, escalating doses of carboplatin (400, 600, 800, 1000, and 1200 mg/m(2)) were administered intraoperatively as IPHC with a perfusion time of 90 min. A subgroup of eight patients that received initial IPHC and subsequent systemic chemotherapy underwent second look reassessment surgery with IPHC. RESULTS: The first 4 dose levels were well tolerated without dose-defining toxicity. The initial two patients treated at 1200 mg/m(2) developed grade 4 myelosuppression thus defining the MTD at 1000 mg/m(2). Newly diagnosed ovarian cancer patients receiving the initial IPHC at the MTD defined above completed standard systemic chemotherapy with six courses of systemic chemotherapy. Eight patients having initial IPHC and systemic chemotherapy subsequently had repeat IPHC performed at second look laparotomy without grade 3 or 4 toxicities. Four patients were found to have extensive adhesions at the time of second look reassessment surgery yet completed IPHC. CONCLUSIONS: The MTD for intraperitoneal carboplatin administered as IPHC was established at 1000 mg/m(2). IPHC at the initial cytoreductive procedure did not preclude subsequent systemic chemotherapy. In addition, repetitive IPHC was feasible at second look reassessment surgery.  相似文献   
39.
40.
OBJECTIVES: To evaluate the level of information and informed consent for maternal serum screening (MSS) for Down syndrome (DS) in the second trimester of pregnancy and analyse the exercise of autonomy towards the test by the women concerned. METHODS: We studied the population of pregnant women attending obstetric consultations in two French hospitals over a 3-month period. The women were assigned to three groups according to MSS results for DS: women at high risk of having a child with DS (group 1), women at low risk (group 2) and women who did not undergo the test (group 3). A questionnaire was completed before the medical consultation, to assess the quality of consent before amniocentesis for the group at high risk and before the second-trimester ultrasound scan for the other two groups. RESULTS: We analysed 305 questionnaires for 89, 137 and 79 women belonging to groups 1, 2 and 3 respectively. In total, 123 women (40.3% [IC 95%, 35-46%]) were considered to be well informed; 33 (10%, [IC 95%, 8-12%]) had a high level of knowledge, but made choices not consistent with their stated attitude, and 149 (49.7% [IC 95%, 45-56%]) were considered uninformed. Logistic regression analysis showed that maternal consent depended on three independent components: The score attributed to the doctor for information about MSS (t = 4.216, p < 0.001).Whether the patient belonged to group 1 (t = -2.631, p < 0.009).Educational level (< high-school diploma, high-school diploma or at least two years of higher education after high school) (t = 2.324, p < 0.02). The rate of consent increased with educational level and was highest for the women in group 1 and for those whose doctor had a high information score. CONCLUSIONS: Our findings clearly show that women are provided with insufficient information concerning MSS screening for DS in the second trimester of pregnancy for real and valid consent to be obtained.  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