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   32790篇
  免费   2406篇
  国内免费   95篇
耳鼻咽喉   376篇
儿科学   812篇
妇产科学   430篇
基础医学   4255篇
口腔科学   650篇
临床医学   2948篇
内科学   6828篇
皮肤病学   467篇
神经病学   3677篇
特种医学   1344篇
外国民族医学   3篇
外科学   4946篇
综合类   677篇
一般理论   66篇
预防医学   2902篇
眼科学   741篇
药学   1998篇
中国医学   20篇
肿瘤学   2151篇
  2023年   115篇
  2022年   191篇
  2021年   460篇
  2020年   268篇
  2019年   459篇
  2018年   596篇
  2017年   429篇
  2016年   502篇
  2015年   562篇
  2014年   866篇
  2013年   1365篇
  2012年   2074篇
  2011年   2209篇
  2010年   1188篇
  2009年   1133篇
  2008年   2104篇
  2007年   2233篇
  2006年   2196篇
  2005年   2400篇
  2004年   2145篇
  2003年   1958篇
  2002年   1994篇
  2001年   374篇
  2000年   300篇
  1999年   373篇
  1998年   438篇
  1997年   410篇
  1996年   380篇
  1995年   368篇
  1994年   298篇
  1993年   285篇
  1992年   268篇
  1991年   289篇
  1990年   262篇
  1989年   226篇
  1988年   196篇
  1987年   226篇
  1986年   194篇
  1985年   199篇
  1984年   240篇
  1983年   232篇
  1982年   281篇
  1981年   279篇
  1980年   230篇
  1979年   140篇
  1978年   155篇
  1977年   105篇
  1976年   128篇
  1975年   97篇
  1974年   119篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Orbital exenteration at the Mayo Clinic. 1967-1986   总被引:2,自引:0,他引:2  
Orbital exenteration was performed in 102 patients at the Mayo Clinic during the 20-year period from 1967 through 1986. The surgical procedure was performed for mucormycosis in one patient and for pain and deformity after a severe facial burn in another; in the remaining 100 patients, exenteration was used to treat a neoplastic disorder. Although 19 different neoplasms were encountered, squamous cell carcinoma, basal cell carcinoma, and melanoma constituted 70% of the total. In 82 patients with no known residual tumor or metastases at operation, the 1-year survival rate was 88.6%, the 5-year rate was 56.8%, and the 5-year rate free of recurrence or metastases was 48.3%. In 18 patients with known residual tumor or metastases at exenteration, 55.0% were alive 1 year postoperatively, and the 5-year survival rate was 25.8%. Unusual findings in this series included two patients with metastatic basal cell carcinoma and one patient with a metastatic thyroid Hürthle cell carcinoma.  相似文献   
22.
Reductions in serum levels of Gc globulin, a hepatically synthesized component of the extracellular actin scavenger system responsible for complexing circulating actin and attenuating intravascular microthrombus formation, are associated with poor outcome in acute liver failure. Clinically applicable assays of the important actin-free fraction (Af-Gc) have not been available until now. We measured actin-free Gc globulin levels with a novel, rapid assay in 61 cases of acute liver failure (ALF) and in 91 patients with cirrhosis (40 of whom were clinically unstable with extrahepatic organ dysfunction), and studied associations with liver dysfunction, extrahepatic organ dysfunction, indices of disseminated coagulation, and outcome. Reductions in Af-Gc levels mirrored hepatic dysfunction and organ dysfunction in both groups, and discriminated patients with poor prognosis from those with good prognosis in the ALF cohort. Levels were lowest in patients with ALF (10% of control values), but levels were also markedly reduced in both unstable (28%) and stable (44%) patients with cirrhosis. Associations with markers of disseminated intravascular coagulation were seen in both groups, most notably in the cirrhosis cohort, supporting a pathophysiological role for reduced Af-Gc in the evolution of organ dysfunction. In acetaminophen-induced ALF, Af-Gc identified patients with poor prognosis as well as did the Acute Physiology and Chronic Health Evaluation (APACHE II) score (area under the receiver operating characteristic curve, 0.7), and in cirrhosis, Af-Gc was an independent predictor of mortality by multifactorial analysis. In conclusion, the importance of Af-Gc reductions in the development of multiple organ dysfunction in ALF and cirrhosis is highlighted, probably resulting from reduced hepatic production and peripheral exhaustion of this arm of the extracellular actin scavenger system.  相似文献   
23.
24.
Mycobacteria-infected macrophages are poor responders to interferon-gamma (IFN-gamma), resulting in decreased expression of IFN-gamma-induced genes. In the present study, we examined the inhibition of IFN-gamma-induced gene expression by Mycobacterium tuberculosis and four different Mycobacterium avium strains in mouse RAW264.7 macrophages. Gamma-irradiated M. tuberculosis inhibited mRNA expression of a panel of six different IFN- gamma-induced genes. All four of the M. avium strains completely inhibited IFN-gamma-induced expression of MHC class II Aalpha and Ebeta mRNA. However, the Mac101 strain, which is serovar 1, inhibited IFN-gamma induction of IFN regulatory factor-1 (IRF-1) and guanylate-binding protein-1 (GBP-1) mRNA to a greater extent than the other M. avium strains, which are serovar 2. In this study, we also show that mycobacteria inhibit gene expression by both toll-like receptor 2 (TLR2)-dependent and independent pathways. The inhibition of IFN-gamma-induced gene expression by M. avium was reduced but not completely blocked in macrophages from TLR2(/) mice. IFN-gamma-induced gene expression was also inhibited by mycobacteria in RAW264.7 cells expressing dominantnegative TLR2 or myeloid differentiation factor 88 (MyD88), further indicating the existence of a pathway independent of TLR2 and MyD88. These data suggest that mycobacteria inhibit IFN-gamma-induced gene expression by multiple pathways involving both TLR2 and non-TLR receptors.  相似文献   
25.
Reports of an 18-fold higher incidence of schizophrenia among second-generation Afro-Caribbeans, and especially Jamaican migrants in the United Kingdom were soon called “an epidemic of schizophrenia,” with the inference that a novel virus, likely to be perinatally transmitted, was a possible etiological agent. This intriguing observation led us to explore a possible link with human T-cell lymphotropic virus type one (HTLV-I), because it is a virus that is endemic in the Caribbean Islands, is perinatally transmitted, known to be neuropathogenic, and the cause of a chronic myelopathy (tropical spastic paraparesis/ HTLV-I associated myelopathy). We therefore examined inpatients at the Bellevue Mental Hospital, Kingston, Jamaica and did standard serological tests for retroviruses HTLV-I and HTLV-II and HIV-I and HIV-II on 201 inpatients who fulfilled ICD-9 and DSM III-R criteria for schizophrenia. Our results produced important negative data, since the seropositivity rates for HTLV-I, the most likely pathogen, were no greater than the seropositivity range for HTLV-I carriers in this island population, indicating that HTLV-I and the other retroviruses tested do not play a primary etiological role in Jamaican schizophrenics.  相似文献   
26.
Summary An infant with persistent truncus arteriosus associated with splenic agenesis and the asplenia syndrome is reported, including clinical, echocardiographic and autopsy findings. To the authors' knowledge this association has not been previously reported.  相似文献   
27.
It is often difficult to make a clinical or histologic diagnosis of erythrodermic mycosis fungoides (MF) and Sézary syndrome (SS). Whereas the histologic parameters for making a diagnosis of MF with well-developed patch and plaque stage lesions are clearly defined, the same criteria appear to be less relevant for diagnosing MF in patients with erythroderma secondary to the disease. In order to better define the histologic features of erythrodermic MF and SS, we studied 28 routine histologic sections of 17 patients with known erythrodermic MF or SS. Sections were reviewed independently by 2 dermatopathologists. Each of 24 parameters was scored semi-quantitatively and the data were compared to data previously reported from a group of 64 patients with limited patch and plaque stage lesions of MF. When compared to biopsies from patients with limited patch/plaque lesions, biopsies taken from erythrodermic patients displayed more parakeratosis (p=0.0492) and acanthosis (p=0.0046), less disproportionate epidermotropism, fewer lymphocytes aligned within the basal layer (p=0.0045), fewer hyper-convoluted cells in the epidermis, more dermal hyperconvoluted cells (p=0.0191), more papillary dermal fibrosis (p=0.0002), more prominent teleangiectasias (p=0.0028) and more mitotic figures.
The histologic features of erythrodermic MF and Sézary syndrome are even more subtle than the features of patch and plaque stage MF, thus rendering the histologic diagnosis more difficult.  相似文献   
28.
A 7-cm anterior mediastinal tumor in an 80-year-old woman was found by light and electron microscopy to be a neuroblastoma. Immunoreactivity for neuron-specific enolase, synaptophysin, and chromogranin supported the diagnosis. Neuroblastoma is an uncommon tumor in adults and we are not aware of a previous report of such a tumor in a patient of this age.  相似文献   
29.
Corneal pathophysiology with contact lens wear   总被引:2,自引:0,他引:2  
Contact lens wear induces a wide spectrum of changes in the appearance and function of the cornea. The most salient effect of lens wear is the hypoxically induced reduction in the rate of metabolic activity of the corneal epithelium and its sequellae. Other important alterations to corneal health associated with contact lens wear may be caused by antigenic and toxic stimuli, mechanical forces, osmotic effects and carbon dioxide retention. Perhaps the most important task facing the contact lens clinician is to distinguish between an acceptable state of physiological modification and an anomalous or pathological state of hypofunction. In this article, we review the assortment of corneal changes primarily on the basis of the causative agents and time scale with reference to the physical and chemical processes leading to the observed signs or symptoms. This procedure allows a strong foundation for understanding the etiology and management principles for the variety of effects that contact lenses may have on the cornea.  相似文献   
30.
Global and regional cerebral blood flow (CBF) were evaluated with single photon emission computerized tomography (SPECT) utilizing both 133Xenon (133Xe) (47 subjects, 47–82 years old) and 99Tc-hexamethylpropyleneamine oxime (99Tc-HMPAO) (27 subjects, 47–80 years old). The 133Xe results showed: among total subjects, no age-related decline in global CBF, but a significant regional decline in the occipital lobe (p < 0.05); among men, significant age-related declines in global, frontal, temporal, occipital and right hemisphere CBF (all p < 0.05); among women, no age-related decline in global or regional CBF. The 99Tc-HMPAO results showed no age-related decline in either global or regional perfusion among total subjects, men or women. These results suggest that age-related global and regional (including frontal lobe) CBF declines do not occur in healthy control subjects after the age of 45 years. However, gender differences in age-related CBF changes warrant further study.  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