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   2363篇
  免费   143篇
  国内免费   23篇
耳鼻咽喉   18篇
儿科学   68篇
妇产科学   24篇
基础医学   294篇
口腔科学   59篇
临床医学   182篇
内科学   690篇
皮肤病学   45篇
神经病学   141篇
特种医学   92篇
外科学   418篇
综合类   5篇
预防医学   97篇
眼科学   25篇
药学   122篇
中国医学   6篇
肿瘤学   243篇
  2024年   6篇
  2023年   31篇
  2022年   77篇
  2021年   135篇
  2020年   59篇
  2019年   74篇
  2018年   108篇
  2017年   77篇
  2016年   75篇
  2015年   79篇
  2014年   91篇
  2013年   108篇
  2012年   155篇
  2011年   155篇
  2010年   119篇
  2009年   89篇
  2008年   139篇
  2007年   144篇
  2006年   108篇
  2005年   104篇
  2004年   100篇
  2003年   92篇
  2002年   100篇
  2001年   47篇
  2000年   33篇
  1999年   38篇
  1998年   17篇
  1997年   16篇
  1996年   7篇
  1995年   7篇
  1994年   7篇
  1993年   10篇
  1992年   16篇
  1991年   14篇
  1990年   4篇
  1989年   8篇
  1988年   7篇
  1987年   7篇
  1986年   10篇
  1984年   3篇
  1982年   5篇
  1981年   3篇
  1979年   4篇
  1977年   4篇
  1975年   3篇
  1974年   4篇
  1972年   6篇
  1971年   5篇
  1970年   3篇
  1969年   3篇
排序方式: 共有2529条查询结果,搜索用时 0 毫秒
101.
We examined the emergence and sequential changes in type I, II, and VI collagen production in an experimental rabbit model of disc degeneration. Type I collagen was minimally present initially and did not change over 24 weeks. Type I collagen seemed to have no effect on the degenerative process in this model. Staining for type II collagen was positive circumferentially in chondrocytelike cells and was mild in the early phase of disc degeneration, when the chondrocytelike cells began to appear in the inner layers of the annulus fibrosus. The stain became stronger during the middle phase when the chondrocytelike cells arranged themselves in cluster. Compared with type II collagen, the staining for type VI collagen was relatively strong early in the degenerative process. These findings led us to speculate that these chondrocytelike cells play an active role in the degenerative process. The reinsertion of nucleus pulposus cells cocultured with annulus fibrosus delayed disc degeneration and the emergence of chondrocytelike cells. Considering that the emergence of chondrocytelike cells which produce type II and type VI collagen is delayed in discs with the injection of cocultured nucleus pulposus cells by annulus fibrosus cells, we conclude that chondrocytelike cells that produce type VI collagen also seems to accelerate degeneration. Type VI collagen is produced at an earlier phase than type II collagen and may be both active agent and a marker for disc degeneration.  相似文献   
102.
Introduction We analyzed the findings of diffusion-weighted (DW) imaging using the single-shot fast spin-echo sequence in acute cervical cord injury and evaluated the usefulness of this method for predicting the prognosis.Methods Our patient group comprised 14 patients examined 2 h to 3 days after injury. First, we visually evaluated the DW imaging findings in all patients. Apparent diffusion coefficient (ADC) maps were also assessed in 13 patients. Second, we assessed follow-up magnetic resonance (MR) examinations obtained in six patients whose DW images showed hyperintensity. Third, we reviewed the functional outcome at discharge.Results The lesions showed hyperintensity in ten patients, and no abnormal signal was noted in the remaining four patients. The ADC maps showed restricted diffusion in all patients with hyperintensity on DW imaging except in one patient for whom the ADC map was unavailable. Repeated MR examinations obtained in six of the ten patients showed either myelomalacia or exacerbation. Seven of the ten patients (70%) required assistance and the other three were independent. Among the four patients without hyperintensity on DW imaging, three (75%) were independent and only one required assistance.Conclusion DW imaging in acute cervical cord injury often reveals restricted diffusion. This finding may predict an unfavorable functional prognosis.  相似文献   
103.
Diagnostic and therapeutic strategies for acute biliary inflammation/infection (acute cholangitis and acute cholecystitis), according to severity grade, have not yet been established in the world. Therefore we formulated flowcharts for the management of acute biliary inflammation/infection in accordance with severity grade. For mild (grade I) acute cholangitis, medical treatment may be sufficient/appropriate. For moderate (grade II) acute cholangitis, early biliary drainage should be performed. For severe (grade III) acute cholangitis, appropriate organ support such as ventilatory/circulatory management is required. After hemodynamic stabilization is achieved, urgent endoscopic or percutaneous transhepatic biliary drainage should be performed. For patients with acute cholangitis of any grade of severity, treatment for the underlying etiology, including endoscopic, percutaneous, or surgical treatment should be performed after the patient's general condition has improved. For patients with mild (grade I) cholecystitis, early laparoscopic cholecystectomy is the preferred treatment. For patients with moderate (grade II) acute cholecystitis, early laparoscopic or open cholecystectomy is preferred. In patients with extensive local inflammation, elective cholecystectomy is recommended after initial management with percutaneous gallbladder drainage and/or cholecystostomy. For the patient with severe (grade III) acute cholecystitis, multiorgan support is a critical part of management. Biliary peritonitis due to perforation of the gallbladder is an indication for urgent cholecystectomy and/or drainage. Delayed elective cholecystectomy may be performed after initial treatment with gallbladder drainage and improvement of the patient's general medical condition.  相似文献   
104.
Background: Upregulation of matrix metalloproteinase‐9 (MMP‐9) induced by tumour necrosis factor‐α (TNF‐α) is reportedly involved in a variety of non‐neoplastic and neoplastic diseases. In this study, we examined which signalling pathways are involved in TNF‐α‐induced MMP‐9 upregulation in cholangiocarcinoma (CC). Methods: We used two CC cell lines: HuCCT‐1 and CCKS‐1. Results: In an ex vivo study using HuCCT‐1 and CCKS‐1 cells, TNF‐α treatment induced MMP‐9 production and activation via interaction with TNF receptor‐1 (TNF‐R1) but not with TNF receptor‐2 (TNF‐R2), shown by zymography, and increased MMP‐9 promoter activity (luciferase assay). As for the signalling pathway, TNF‐α stimulation led to the phosphorylation of extracellular signal‐regulated kinase 1/2 (Erk1/2) and p38 mitogen‐activated protein kinase (p38MAPK) and translocation of nuclear factor κB (NF‐κB) (p65) into the nuclei. Inhibition studies using SB203580 (inhibitor of p38MAPK), U0126 (inhibitor of mitogen‐activated or extracellular signal‐regulated protein kinase 1/2) and MG132 (inhibitor of NF‐κB) showed that the phosphorylation of Erk1/2 and p38MAPK with activation of NF‐κB was closely related to MMP‐9 upregulation in both cell lines. Conclusion: These data suggest that TNF‐α/TNF‐R1 interaction leads to the phosphorylation of Erk1/2 and p38MAPK and nuclear translocation of NF‐κB, which is closely associated with the production and activation of MMP‐9 in cultured CC cells of HuCTT‐1 and CCKS‐1. Upregulation of MMP‐9 with NF‐κB activation may be involved in the tumour invasion of CC.  相似文献   
105.
Intracerebroventricular (ICV) injection of α-melanocyte-stimulating hormone (α-MSH) inhibits, whereas ICV injection of neuropeptide Y (NPY) stimulates food intake in the goldfish. However, there is little information about the functional relationship between α-MSH-induced anorexigenic and NPY-induced orexigenic actions in the goldfish. In this study we examined the relationship between α-MSH- and NPY-containing neurons in the goldfish hypothalamus to investigate whether these α-MSH- and NPY-containing neurons have direct mutual inputs. α-MSH- and NPY-like immunoreactivities were distributed throughout the brain, especially in the diencephalon. In particular, α-MSH-containing nerve fibers or endings lay in close apposition to NPY-containing neurons in a specific region of the hypothalamus, the nucleus posterioris periventricularis (NPPv). NPY-containing nerve fibers or endings also lay in close apposition to α-MSH-containing neurons specifically in the interior part of the nucleus lateralis tuberis (NLTi). We also investigated the effect of ICV injection of melanocortin 4 receptor agonist (melanotan II) at 100 pmol/g body weight (BW), which is enough to suppress food intake, or NPY at 10 pmol/g BW, which is enough to enhance food intake, on expression levels of mRNA for NPY or proopiomelanocortin (POMC) in the hypothalamus. ICV injection of melanotan II and NPY induced a significant decrease in the expression levels for NPY and POMC mRNA, respectively. These observations suggest that α-MSH- and NPY-containing neurons share direct mutual inputs in the NPPv and the NLTi of the hypothalamus, and that α-MSH and NPY functionally interact or exhibit mutual inhibition to regulate feeding behavior in the goldfish.  相似文献   
106.
While most cesareans are conducted without any particular problem, in nearly 20% of cases, women may present severe postoperative pain, despite adequately managed multimodal analgesia. In terms of pain, there is significant variability because of the numerous factors involved, including physiological, cognitive, cultural, social, emotional and genetic ones.Different approaches have been proposed to identify women at risk of developing significant postoperative pain, including nociceptive tests and/or psychosocial questionnaires associated or not to genetic analyses.Although some results remain controversial, these approaches now identify a population at risk in the presence of preoperative features such as: anxiety, catastrophism, low nociceptive threshold, hyperalgesia or certain genetic polymorphisms involved in nociception or effectiveness of analgesic drugs.If nociceptive tests and especially genetic tests are currently difficult to implement, assessment of psychosocial factors using questionnaires, more or less complex, seems like a more appropriate routine approach.  相似文献   
107.
Recent high precision 142Nd isotope measurements showed that global silicate differentiation may have occurred as early as 30–75 Myr after the Solar System formation [Bennett V, et al. (2007) Science 318:1907–1910]. This time scale is almost contemporaneous with Earth’s core formation at ∼30 Myr [Yin Q, et al. (2002) Nature 418:949–952]. The 182Hf-182W system provides a powerful complement to the 142Nd results for early silicate differentiation, because both core formation and silicate differentiation fractionate Hf from W. Here we show that eleven terrestrial samples from diverse tectonic settings, including five early Archean samples from Isua, Greenland, of which three have been previously shown with 142Nd anomalies, all have a homogeneous W isotopic composition, which is ∼2ε-unit more radiogenic than the chondritic value. By using a 3-stage model calculation that describes the isotopic evolution in chondritic reservoir and core segregation, as well as silicate differentiation, we show that the W isotopic composition of terrestrial samples provides the most stringent time constraint for early core formation (27.5–38 Myr) followed by early terrestrial silicate differentiation (38–75 Myr) that is consistent with the terrestrial 142Nd anomalies.  相似文献   
108.
The normal bone turnover is important for ESRD patients in not only skeletal problem but also patients QOL and survival. The abnormal bone turnover often induces the renal osteodystrophy and ectopic calcification. The major regulative factor on bone turnover is PTH. We propose here the target zone of PTH in ESRD patients with skeletal resistance for PTH. We recommended the intact-PTH 100 - 150 pg/mL for normal Ca/Pi/bone metabolism. This range of intact-PTH is equivalent to C-PTH 4.0 - 6.2 ng/mL, HS-PTH 10.0 - 16.0 ng/mL, and whole-PTH 80 - 110 pg/mL. The maintenance of normacalcemia and normophosphatemia are important for the arrival into the target zone of PTH using active vitamin D.  相似文献   
109.
110.
Inamasu J  Nakamura Y  Saito R  Kuroshima Y  Mayanagi K  Ichikizaki K 《Neurosurgery》2002,50(6):1199-205; discussion 205-6
OBJECTIVE: Patients with poor-grade subarachnoid hemorrhage (SAH) have been considered good candidates for endovascular treatment. The results of treatment of Grade V SAH, the poorest grade, however, have not been fully elucidated. METHODS: The clinical characteristics and outcome parameters of 22 World Federation of Neurosurgical Societies Grade V SAH patients treated endovascularly in the acute stage between 1998 and 2000 are summarized and compared with those of 18 Grade V SAH patients treated conservatively between 1995 and 1997. RESULTS: Among the 22 patients treated endovascularly, 8 patients (36.4%) survived. The rate was significantly higher than that of the 18 patients treated conservatively (5.6%), only one of whom survived. The favorable outcome rate, however, was not significantly different between the two groups (4.5% versus 6.0%). Subdivision of both treatment groups according to Glasgow Coma Scale (GCS) score showed that the improved survival among those treated endovascularly was attributable to the improved survival in those with a preprocedural GCS score of 6 but not of 4 or 5. CONCLUSION: Endovascular treatment of the 22 World Federation of Neurosurgical Societies Grade V SAH patients improved their survival rate but not their favorable outcome rate in comparison with conservative treatment. Further accumulation of clinical data is essential to determine whether endovascular treatment can improve the functional outcome of those with GCS scores of 6 and whether there is no role for endovascular treatment in those with GCS scores of 4 or 5.  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