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   7926篇
  免费   608篇
  国内免费   54篇
耳鼻咽喉   67篇
儿科学   241篇
妇产科学   173篇
基础医学   1138篇
口腔科学   131篇
临床医学   1235篇
内科学   1554篇
皮肤病学   71篇
神经病学   695篇
特种医学   369篇
外科学   707篇
综合类   140篇
一般理论   6篇
预防医学   759篇
眼科学   183篇
药学   528篇
中国医学   25篇
肿瘤学   566篇
  2023年   48篇
  2022年   102篇
  2021年   143篇
  2020年   115篇
  2019年   144篇
  2018年   217篇
  2017年   151篇
  2016年   145篇
  2015年   162篇
  2014年   211篇
  2013年   349篇
  2012年   468篇
  2011年   485篇
  2010年   292篇
  2009年   251篇
  2008年   413篇
  2007年   493篇
  2006年   429篇
  2005年   481篇
  2004年   411篇
  2003年   378篇
  2002年   352篇
  2001年   128篇
  2000年   119篇
  1999年   113篇
  1998年   126篇
  1997年   124篇
  1996年   92篇
  1995年   93篇
  1994年   104篇
  1993年   86篇
  1992年   77篇
  1991年   76篇
  1990年   76篇
  1989年   71篇
  1988年   86篇
  1987年   71篇
  1986年   68篇
  1985年   82篇
  1984年   63篇
  1983年   41篇
  1982年   65篇
  1981年   57篇
  1980年   62篇
  1979年   42篇
  1978年   42篇
  1977年   39篇
  1976年   55篇
  1975年   41篇
  1973年   35篇
排序方式: 共有8588条查询结果,搜索用时 15 毫秒
51.
BackgroundSevere acute respiratory syndrome (SARS) and coronavirus disease 2019 (COVID-19) are closely related. The effect of AKI on the clinical outcomes of these two conditions is unclear.MethodsThis retrospective, territory-wide cohort study used an electronic public healthcare database in Hong Kong to identify patients with SARS or COVID-19 by diagnosis codes, virologic results, or both. The primary endpoint was a composite of intensive care unit admission, use of invasive mechanical ventilation, and/or death.ResultsWe identified 1670 patients with SARS and 1040 patients with COVID-19 (median ages, 41 versus 35 years, respectively). Among patients with SARS, 26% met the primary endpoint versus 5.3% of those with COVID-19. Diabetes mellitus, abnormal liver function, and AKI were factors significantly associated with the primary endpoint among patients with either SARS or COVID-19. Among patients with SARS, 7.9%, 2.1%, and 3.7% developed stage 1, stage 2, and stage 3 AKI, respectively; among those with COVID-19, 6.6%, 0.4%, and 1.1% developed stage 1, stage 2, and stage 3 AKI, respectively. In both groups, factors significantly associated with AKI included diabetes mellitus and hypertension. Among patients with AKI, those with COVID-19 had a lower rate of major adverse clinical outcomes versus patients with SARS. Renal function recovery usually occurred within 30 days after an initial AKI event.ConclusionsAKI rates were higher among patients with SARS than those with COVID-19. AKI was associated with major adverse clinical outcomes for both diseases. Patients with diabetes mellitus and abnormal liver function were also at risk of developing severe consequences after SARS and COVID-19 infection.  相似文献   
52.
53.
Five major objectives for pharmacokinetic investigations in support of toxicity studies are identified as follows: Assess whether animals exhibited measurable blood concentrations in a dose-dependent manner; estimate average area under the concentration- time curve (AUC)and maximal concentration (C max )for each treatment group; elucidate general patterns in the concentration-time (CxT)profile, and summarize relationships between CxTand treatment group; determine CxTdependence on day into study; and judge interanimal variability and identify any animals with unusual concentration response. Such objectives are generally addressed in rodent toxicity studies by including satellite animals in the study. Satellite animals are extra animals dosed as per protocol but not subjected to toxicological and pathological observations and tests. Instead, they are used exclusively for the evaluation of pharmacokinetic characteristics of the test compound. In this paper, methods are described for achieving the five listed pharmacokinetic objectives in rodent toxicity studies without the use of satellite animals. A rat toxicity study is presented as an example.  相似文献   
54.
The value of cancer treatment was assessed using a natural experiment where patients who refused treatment served as no-treatment controls in a situation where withholding treatment to form a control group is unethical. Each cancer patient who refused treatment in Alberta, Canada between 1975 and 1988 was compared with five subjects who accepted treatment, matched on cancer site, age, number of cancers, and time period. Variables associated with treatment-refusal were included in Cox's proportional hazards model of survival, with death from cancer as the endpoint and deaths from other causes as censored observations. Treatment was refused at a rate of 7.5 per 1,000. One-third of patients who refused treatment had lung cancer and most had unstaged disease. Treatment refusal was associated with a difference in median survival of approximately nine months. Site-specific analyses showed a range of effects. Case fatality among the treated patients fell by approximately 10 percent during the 14-year study period. Even in advanced disease, treatment can result in improved survival. However, the results of this study must be interpreted with caution and cannot be generalized to all cancer patients.Dr Huchcroft and Mr Snodgrass are with the Alberta Cancer Board, Calgary, Alberta, Canada. Address correspondence to Dr Shirley Huchcroft, Senior Scientist, Division of Epidemiology and Preventive Oncology, Alberta Cancer Board, Calgary, Alberta, Canada T2N 4N2.  相似文献   
55.
Using the UV-mimetic mutagen 4-nitroquinoline-1-oxide (4NQO) to induce genetic damage in human cells (lymphoblastoid lines and primary cultures of peripheral blood samples), chromosome aberrations were induced by treating the cells with 4NQO at 1 X 10(-5) M for 24 h. The overwhelming majority of chromosome aberrations was of the chromatid (S + G2) type instead of the chromosome (G1) type. The most common chromatid aberrations were simple breaks, isochromatid breaks, and chromatid exchanges. When the number of chromatid breaks per cell value was used as a measurement for 4NQO sensitivity, lymphoblastoid cells from a xeroderma pigmentosum patient showed the highest sensitivity, followed by the cells of two melanoma patients and normal persons. These preliminary results suggest that 4NQO may be employed to develop an assay system as a biomarker for determining UV sensitivity in the human population.  相似文献   
56.
The safety of cysteamine after renal transplantation and during pregnancy is an important issue, since girls with cystinosis are in better health on cysteamine therapy and thus more likely to become pregnant. In the first study, cysteamine was given to pregnant rats on days 6.5–18.5 post conception in oral doses of 0, 37.5, 75, 100, and 150 mg/kg per day. The dams were sacrificed on day 20.5, the fetal kidneys removed and prepared for histological examination. In the second study, cysteamine was given to dams on days 6.5–19.5 post conception in oral doses of 0, 37.5, 50, and 75 mg/kg per day. Dams were allowed to give birth naturally and pups were given cysteamine on days 4–21 to yield the same oral doses of cysteamine given to the dam. Renal function was evaluated on day 35. Histological examination of fetal kidneys revealed no changes even in kidneys from fetuses with growth retardation and malformations. Furthermore, there were no alterations in renal function in offspring on day 35. These findings demonstrate that cysteamine therapy does not affect renal development in the rat. Further investigations will be required to prove whether cysteamine therapy has the potential to affect renal development in the human. Received: 25 September 1998 / Revised: 17 November 1998 / Accepted: 13 December 1998  相似文献   
57.
The aim of this study was to compare the linear growth of children with cerebral palsy (CP) with that of children without CP. The segmental lengths (humerus, ulna, femur, tibia, and spine), recumbent length, body weight, and bone age of 62 children with CP (age range 2.25 to 14 years, mean 7.13 years) were measured and compared with 68 children without CP (age range 1.50 to 12.67 years, mean 6.73 years). The results show that bone-age delay is common in children with CP (68% with a delay of more than 1 year). The linear growth of children with CP is similar to that of children without CP when bone age is used instead of chronological age. There is a strong correlation between segmental lengths and body height. Hence, this study favours using segmental lengths for estimating height in children with CP and using the comparison group as a reference for this purpose. Nutritional and non-nutritional factors on bone-age delay are discussed.  相似文献   
58.
PURPOSE: To determine whether molecular genetic analysis of ocular-adnexal lymphoid tumors, combined with histopathology and tumor location, is helpful in predicting which patients will develop systemic lymphoma. METHODS: A combined retrospective and prospective study of 77 patients with ocular-adnexal lymphoid tumors was performed. The tumors were subdivided into conjunctival, orbital, and eyelid lesions, and all were studied using both routine histopathology and molecular genetic analysis. RESULTS: Most lesions (70%) were small cell lymphomas of the mucosa-associated lymphoid tissue type, and the majority of tumors (90%) contained monoclonal or oligoclonal populations of lymphocytes discovered on molecular genetic analysis. Additionally, 72% of tumors exhibiting clonality had more than one gene rearrangement. Fifty-three percent of patients developed extraocular lymphoma sometime during the course of their disease. Patients with gene rearrangements on Southern blot hybridization had a 52% incidence of nonocular disease, compared with 63% of those without rearrangements. Patients with conjunctival tumors had a 37.5% incidence of nonocular disease, those with orbital tumors had a 54% incidence, and those with eyelid tumors had a 100% incidence of nonocular lymphoma. Only two patients died as result of systemic lymphoma. CONCLUSIONS: Most ocular-adnexal lymphoid tumors are lymphomas of the mucosa-associated lymphoid tissue type. The majority of tumors exhibit gene rearrangements on molecular genetic analysis, and this technique was not helpful in predicting which patients would develop nonocular lymphoma. Tumor location did have predictive value: Conjunctival lesions had the lowest incidence of nonocular lymphoma, and lid lesions had the highest incidence. Even with disseminated disease, most patients have a favorable prognosis with treatment.  相似文献   
59.
60.
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