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   40977篇
  免费   2689篇
  国内免费   418篇
耳鼻咽喉   179篇
儿科学   1808篇
妇产科学   793篇
基础医学   3635篇
口腔科学   462篇
临床医学   4215篇
内科学   11085篇
皮肤病学   573篇
神经病学   2671篇
特种医学   706篇
外科学   4094篇
综合类   3196篇
现状与发展   1篇
一般理论   8篇
预防医学   3752篇
眼科学   1144篇
药学   2087篇
  2篇
中国医学   747篇
肿瘤学   2926篇
  2024年   49篇
  2023年   308篇
  2022年   303篇
  2021年   445篇
  2020年   420篇
  2019年   176篇
  2018年   636篇
  2017年   620篇
  2016年   747篇
  2015年   720篇
  2014年   780篇
  2013年   1152篇
  2012年   2562篇
  2011年   3225篇
  2010年   1276篇
  2009年   1122篇
  2008年   3048篇
  2007年   2830篇
  2006年   2493篇
  2005年   2787篇
  2004年   3555篇
  2003年   3644篇
  2002年   2885篇
  2001年   2287篇
  2000年   1014篇
  1999年   863篇
  1998年   738篇
  1997年   520篇
  1996年   340篇
  1995年   263篇
  1994年   294篇
  1993年   388篇
  1992年   284篇
  1991年   227篇
  1990年   186篇
  1989年   131篇
  1988年   110篇
  1987年   121篇
  1986年   99篇
  1985年   83篇
  1984年   53篇
  1983年   32篇
  1982年   28篇
  1981年   30篇
  1980年   25篇
  1979年   20篇
  1978年   27篇
  1977年   17篇
  1975年   12篇
  1974年   16篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
RATIONALE: High-resolution computed tomography (HRCT) is an integral aspect of the evaluation of patients with suspected idiopathic pulmonary fibrosis (IPF). However, few studies have evaluated its use in a large cohort. OBJECTIVES: To describe HRCT features in patients with mild to moderate IPF, compare diagnostic evaluations by a radiology core (three thoracic radiologists) with those by study-site radiologists, correlate baseline clinical and physiologic variables with HRCT findings, and evaluate their association with mortality. METHODS: We assessed HRCT scans from patients with IPF (n = 315) enrolled in a randomized controlled study evaluating IFN-gamma1b. MEASUREMENTS AND MAIN RESULTS: There was concordance between study-site and core radiologists regarding the diagnosis of IPF in 86% of cases. Diffusing capacity of carbon monoxide (DLCO) was the physiologic characteristic most highly correlated with HRCT findings. Multivariate analysis identified three independent predictors of mortality: a higher extent of fibrosis score increased the risk of death (p < 0.0001), whereas a higher percent-predicted DLCO (p = 0.004) and treatment assignment to IFN-gamma1b rather than placebo (p = 0.04) reduced the risk of death. CONCLUSIONS: A study-site diagnosis of IPF on HRCT was regularly confirmed by core radiologists. Extent of reticulation and honeycombing on HRCT is an important independent predictor of mortality in patients with IPF.  相似文献   
992.
We investigated the effect of in utero and postnatal environmental tobacco smoke (ETS) exposure on respiratory symptoms and atopy in the first 3 years of life in children at high risk of allergic disease (both parents atopic). Three hundred and sixty-nine children were followed from birth and reviewed at ages 1 and 3 years (respiratory questionnaire, skin testing). Parental smoking questionnaires were administered, and plasma cotinine in cord and peripheral blood (at age 1 year) was measured (capillary column gas-liquid chromatography). Wheezing starting in the first year of life was significantly more common in children of smoking mothers (54.2% vs. 39.5%, P = 0.017), but not wheezing starting after age 1 year (10.8% vs. 10.9%, smoking and nonsmoking mothers, P = 0.99). Detectable cord cotinine was not associated with wheeze. More frequent wheeze in infancy was significantly more common in those with detectable 1-year cotinine (e.g., wheeze without colds, 17.8% vs. 5.6%, P = 0.02; wheeze most days, 6.5% vs. 0%, P = 0.04). ETS exposure was not associated with atopy. In the multivariate regression analysis, maternal smoking during pregnancy and/or in the first year of life remained associated with wheeze in the first year of life (odds ratio, 1.88; 95% confidence interval, 1.14-3.12; P = 0.01). ETS exposure in "high-risk" infants increases the risk of wheezing starting in the first year of life, but not after age 1 year. However, ETS exposure has little or no effect on the development of atopy. Measurement of plasma cotinine was no more useful than tobacco exposure assessment by questionnaire in our cohort.  相似文献   
993.
BACKGROUND: Nephrolithiasis is a well-known complication of indinavir treatment and may result in urological symptoms ranging from renal colic to renal insufficiency. OBJECTIVE: To obtain further knowledge regarding the incidence and risk factors of urological symptoms associated with indinavir sulfate use. METHODS: This study was performed in the ATHENA (AIDS Therapy Evaluation National AIDS Therapy Evaluation Centre) cohort of patients infected with human immunodeficiency virus (HIV) receiving antiretroviral therapy in the Netherlands. The incidence rate of urological symptoms was assessed in a subcohort of 1219 patients starting HIV protease inhibitor treatment after 1996. Urological symptoms were defined as an initial report of nephrolithiasis, renal colic, flank pain, hematuria, renal insufficiency, or nephropathy. Using multivariate Cox regression analysis, risk factors for urological symptoms during indinavir treatment were subsequently studied among the subset of 644 patients who started indinavir treatment after 1996. RESULTS: The incidence of urological symptoms was 8.3 per 100 treatment-years for indinavir vs 0.8 per 100 treatment-years for other HIV protease inhibitors. Risk factors for urological symptoms during indinavir treatment were low weight (relative risk [RR], 2.1; 95% confidence interval [CI], 1.1-3.9), low lean body mass (RR, 1.7; 95% CI, 1.0-2.9), undetectable HIV-1 RNA when starting indinavir treatment (RR, 3.2; 95% CI, 1.5-6.0), prior treatment change because of intolerance (RR, 2.4; 95% CI, 1.2-5.1), indinavir regimens of 1000 mg or more twice daily (RR, 3.1; 95% CI, 1.3-8.2), and warm environmental temperatures (RR, 3.9; 95% CI, 1.7-8.8). Risk estimates were highest among patients with a low lean body mass. CONCLUSION: Increased alertness for urological symptoms is warranted for patients starting indinavir treatment, particularly among those with a low lean body mass, during indinavir regimens of 1000 mg or more twice daily, and in warm weather environments.  相似文献   
994.
995.
996.
Anemia, a common hematological abnormality in HIV, contributes to decreased quality of life (QOL). This study assessed once-every-2-week epoetin alfa on maintaining QOL and hemoglobin (Hb) in anemic HIV-infected patients in a 24-week, open-label, multicenter study. HIV-infected patients (Hb < or =12 g/dl) received epoetin alfa 40,000 units subcutaneously once weekly, until reaching Hb > or =13 g/dl. Patients then entered a maintenance phase (MP), in which epoetin alfa was administered every other week or at longer intervals. The trial objectives were to determine if QOL, as measured by the Medical Outcomes Study-HIV (MOS-HIV) general health perceptions (GHP) domain and Hb, was maintained. Safety was also assessed. A total of 292 patients were enrolled (72% on HAART). Mean baseline laboratory values were Hb = 10.8 g/dl, CD4(+) count = 280 cells/microl, and HIV RNA = 51,867 copies/ml. In all, 81% of patients reached Hb > or =13 g/dl and 92% reached Hb > or =12 g/dl. QOL was maintained from the beginning (GHP = 44.2 points) to the end of MP (GHP = 43.4 points) with every other week or longer dosing. Mean Hb at the beginning of MP was 13.4 +/- 0.5 g/dl and was 12.8 +/- 1.4 g/dl at study end. Epoetin alfa was well tolerated; adverse events were consistent with those reported in previous studies of epoetin alfa in HIV-infected patients. Although the clinical approach tested in this study is not consistent with current prescribing recommendations, the results confirm the efficacy of prolonged dosing intervals (every 2-4 weeks) in maintaining optimal Hb levels and QOL in anemic HIV-infected patients.  相似文献   
997.
998.
To evaluate glycemic control using convenience-oriented biphasic insulin analog compared with intensified insulin therapy, we conducted a 6-month multicentric, open-label, randomized trial in Japanese insulin-naive patients with type 2 diabetes mellitus. A total of 160 adult patients at 19 centers were randomized into two groups: those who received twice-daily injections of biphasic insulin aspart 30 and those on three-times-daily injections of insulin aspart with or without NPH insulin (multiple daily injections). At 6 months, mean HbA(1c) decreased by approximately 2.5% in both groups. Reduction of HbA(1c) on both regimens was better in patients whose prior therapy before starting the study was only diet and exercise (-5.0%) than in patients who were previously taking oral antidiabetic agents (-1.0%). No incidence of major hypoglycemia was observed in either regimen. These results suggest that convenience-oriented insulin therapy using biphasic insulin analog is as useful as intensified insulin therapy with insulin analog for the treatment of type 2 diabetes mellitus over 6 months. Furthermore, early induction of insulin therapy in individuals hitherto using only diet and exercise may provide good glycemic control. This study suggests that convenience-oriented biphasic insulin aspart 30 might be a useful option for the treatment of type 2 diabetes mellitus, especially for insulin-naive patients over 6 months, although it should be changed to another regimen when expected efficacy is not obtained.  相似文献   
999.
The Oxford Cholesterol Study is a randomized placebo-controlledtrial designed primarily to assess the effects of simvastatinon blood cholesterol levels and side-effects in preparationfor a large, long-term trial of the effects of cholesterol-loweringdrug therapy on mortality. At present there is only limitedevidence from randomized comparisons of the effects of HMG-CoAreductase inhibitors, such as simvastatin, on thrombogenic,as distinct from atherogenic, pathways in coronary heart disease.The present sub-study was carried out to assess the effectsof simvastatin on a range of haemostatic variables, as wellas on free fatty acids and on lipoprotein fractions not studiedin detail previously. At an average of about 2 years after starting study treatment,non-fasting blood samples were obtained from a sequential sampleof 162 participants who had been randomly allocated to receive40 mg (54 patients) or 20 mg (57 patients) daily simvastatinor matching placebo treatment (51 patients). Only patients whoreported taking their study treatment and who were not knownto be diabetic or to be taking some other lipid lowering treatmentwere to be included. The principal comparisons were to be ofthose allocated simvastatin (i.e. 20 and 40 mg doses combined)vs those allocated placebo. Among patients allocated simvastatin, marginally significantlower factor VII antigen levels (12·10%±6·08of standard; 2P<0·05) and non-significantly lowerfactor VII coagulant activity (8·24%±4·99of standard) and fibrinogen concentrations (0·10±0·08g.l–1) were observed. In contrast, plasminogen activatorinhibitor activity was significantly higher (2·62±1·03IU; 2P<0·01) among patients allocated simvastatin.No significant differences were seen in the other haemostaticfactors studied (e.g. prothrombin fragment 1·2, factorXII and C$$$ inhibitor). Total free fatty acid concentrationwas marginally significantly reduced (2P=0·02) with simvastatin,but none of the reductions in individual free fatty acids wassignificant. Lipoprotein fractions were only measured amongpatients allocated 40 mg daily simvastatin or placebo. Comparedwith placebo, simvastatin produced significant decreases notonly in LDL cholesterol (1·74±0·15 mmol.1–1;2P<0·0001) but also in VLDL cholesterol (0·28±0·08mmol.1–1; 2P<0·001) and IDL cholesterol (0·17±0·03mmol.1–1; 2P<0·0001). There were also lowertriglyceride levels associated with LDL (0·07±0·01mmol.1–1; 2P<0·0001), IDL (0·03±0·01mmol.1–1; 2P<0·01) and VLDL (0·27±0·14;2P=0·05). The effects of simvastatin on haemostatic variables appear tobe far less marked than its lipid effects. Given the associationsof haemostatic factors with coronary heart disease incidence,larger randomized comparisons of the HMG-CoA re1ductase inhibitors(and of the newer fibrates, which may produce greater effects)are needed to provide more reliable estimates of the extentto which they influence these variables.  相似文献   
1000.
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