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   9671篇
  免费   705篇
  国内免费   37篇
耳鼻咽喉   87篇
儿科学   207篇
妇产科学   145篇
基础医学   1806篇
口腔科学   234篇
临床医学   875篇
内科学   1830篇
皮肤病学   286篇
神经病学   1199篇
特种医学   357篇
外科学   840篇
综合类   24篇
一般理论   8篇
预防医学   827篇
眼科学   227篇
药学   596篇
中国医学   23篇
肿瘤学   842篇
  2024年   12篇
  2023年   97篇
  2022年   164篇
  2021年   316篇
  2020年   191篇
  2019年   257篇
  2018年   259篇
  2017年   284篇
  2016年   329篇
  2015年   396篇
  2014年   446篇
  2013年   555篇
  2012年   868篇
  2011年   840篇
  2010年   494篇
  2009年   450篇
  2008年   664篇
  2007年   701篇
  2006年   681篇
  2005年   585篇
  2004年   509篇
  2003年   452篇
  2002年   368篇
  2001年   76篇
  2000年   49篇
  1999年   67篇
  1998年   74篇
  1997年   56篇
  1996年   27篇
  1995年   25篇
  1994年   28篇
  1993年   21篇
  1992年   11篇
  1991年   3篇
  1990年   3篇
  1989年   9篇
  1987年   4篇
  1986年   4篇
  1984年   2篇
  1983年   4篇
  1982年   8篇
  1981年   5篇
  1980年   3篇
  1979年   2篇
  1978年   3篇
  1977年   5篇
  1976年   2篇
  1975年   1篇
  1974年   1篇
  1959年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
To evaluate tumor response after treating unresectable lung metastases with transpulmonary chemoembolization (TPCE) in palliative intention. From 2001 to 2005, 52 patients (mean: 59.8 years; 32 males/20 females) suffering from 106 unresectable lung metastases (mean:6 metastases/patient; range,1–21) were treated with 2–10 TPCE-sessions (mean: 3.3 sessions/patient). Metastases originated from primaries, including colorectal carcinoma (n = 20), breast cancer (n = 6), renal cellular carcinoma (n = 5), thyroid cancer (n = 4), cholangiocellular carcinoma (n = 2), leiomyosarcoma (n = 2), and others (n = 13). Tumor-feeding pulmonary arteries were selectively probed after puncturing the femoral vein, and administering 10 ml lipiodol, mitomycin C, and microspheres (Spherex) each via balloon catheter over pulmonary approach. During therapy, follow-up was accomplished at 4-week intervals using unenhanced and contrast-enhanced CT. After sequential therapy, follow-up was performed every 3 months for a period of 6 months up to 2.25 years. All patients tolerated the treatments well without major side effects or complications. In 24% (n = 13) moderate to high lipiodol uptake was found, while 75% (n = 39) of the tumors showed a low uptake. According to the RECIST criteria, “partial response” was achieved in 16 cases, “stable disease” in 11 cases, and “progressive disease” in 25 cases [mean survival: 17 months/median: 21.1 months (Kaplan-Meyer)]. According to these findings, TPCE is a well-tolerated procedure for palliative treatment of unresectable lung metastases.  相似文献   
82.
The class of autocalibrating “data‐driven” parallel imaging (PI) methods has gained attention in recent years due to its ability to achieve high quality reconstructions even under challenging imaging conditions. The aim of this work was to perform a formal comparative study of various data‐driven reconstruction techniques to evaluate their relative merits for certain imaging applications. A total of five different reconstruction methods are presented within a consistent theoretical framework and experimentally compared in terms of the specific measures of reconstruction accuracy and efficiency using one‐dimensional (1D)‐accelerated Cartesian datasets. It is shown that by treating the reconstruction process as two discrete phases, a calibration phase and a synthesis phase, the reconstruction pathway can be tailored to exploit the computational advantages available in certain data domains. A new “split‐domain” reconstruction method is presented that performs the calibration phase in k‐space (kx, ky) and the synthesis phase in a hybrid (x, ky) space, enabling highly accurate 2D neighborhood reconstructions to be performed more efficiently than previously possible with conventional techniques. This analysis may help guide the selection of PI methods for a given imaging task to achieve high reconstruction accuracy at minimal computational expense. Magn Reson Med 59:382–395, 2008. © 2008 Wiley‐Liss, Inc.  相似文献   
83.
PURPOSE: To investigate the effects of intravascular volume replacement therapy on the inflammatory response during major surgery. METHODS: Thirty-six patients scheduled for elective abdominal surgery were randomized to receive either 6% hydroxyethylstarch (130,000 Dalton mean molecular weight, degree of substitution 0.4; n = 18, HES-group) or lactated Ringer's solution (RL-group; n = 18) for intravascular volume replacement. Fluid therapy was given perioperatively and continued for 48 hr in the intensive care unit. Volume replacement was guided by physiological parameters. Serum concentrations of interleukin (IL)-6, IL-8 and IL-10 and soluble adhesion molecules (sELAM-1 and sICAM-1) were measured after induction of anesthesia, four hours after the end of surgery, as well as 24 hr and 48 hr postoperatively. RESULTS: Biometric and perioperative data, hemodynamics and oxygenation were similar between groups. On average, 4470 +/- 340 mL of HES 130/0.4 per patient were administered in the HES-group compared to 14310 +/- 750 mL of RL in the RL-group during the study period. Release of pro-inflammatory cytokines IL-6 and IL-8 was significantly lower in the HES-group [(peak values) 47.8 +/- 12.1 pg*dL(-1) of IL-6 and 35.8 +/- 11.2 pg*mL(-1) of IL-8 (HES-group) vs 61.2 +/- 11.2 pg*dL(-1) of IL-6 and 57.9 +/- 9.7 pg*mL(-1) of IL-8 (RL-group); P < 0.05]. Serum concentrations of sICAM-1 were significantly higher in the RL-group [(peak values) 1007 +/- 152 ng*mL(-1) (RL-group) vs 687 +/- 122 ng*mL(-1), (HES group); P < 0.05)]. Values of sELAM-1 were similar in both groups. CONCLUSION: Intravascular volume replacement with HES 130/0.4 may reduce the inflammatory response in patients undergoing major surgery compared to a crystalloid-based volume therapy. We hypothesize that this is most likely due to an improved microcirculation with reduced endothelial activation and less endothelial damage.  相似文献   
84.
BACKGROUND: Ageing is associated with a progressive loss of renal mass and kidney length and a decline in glomerular filtration rate (GFR). This study evaluated a possible correlation between renal function and kidney size measured by ultrasonography (US), and whether the latter helps estimate GFR in the elderly. METHODS: Twenty-five medically stable elderly patients (mean age 85 +/- 5 yrs) were examined in a geriatric ward at a university hospital. Blood samples were taken to determine serum creatinine (Cr) levels. On the same day, 51chromium ethylenediamine tetraacetic acid (51Cr-EDTA) clearance was performed as the gold standard of GFR. US measured kidney length, transverse and anteroposterior dimensions. RESULTS: Serum Cr (r=-0.67; p=0.0002), Cockcroft-Gault formula (r=0.82; p<0.0001), absolute length (r=0.51; p=0.008) and volume kidney (r=0.46; p=0.02) correlated significantly with GFR. After receiver operating curve (ROC) analysis, length was less specific than sensitive in detecting renal impairment. Adding length to the Cockcroft-Gault formula did not improve GFR estimation (p=0.44). In contrast, adding length to serum Cr levels improved GFR estimation (p=0.015). CONCLUSION: In the elderly, kidney length and volume significantly correlated with GFR. However, length has a low specificity in predicting renal impairment. Therefore, in clinical practice, serum Cr levels and calculated Cr clearance are more useful in predicting renal impairment. However, normal kidney length can help to exclude renal impairment in the elderly at risk of GFR underestimation by a calculated Cr clearance.  相似文献   
85.
Traditional cardiac risk factors in individuals with chronic kidney disease   总被引:4,自引:0,他引:4  
Individuals with chronic kidney disease (CKD) are at increased risk for the development and progression of cardiovascular disease (CVD). The increased risk is due to a higher prevalence of both traditional risk factors as well as nontraditional risk factors. In this review we focus on individuals at all stages of CKD and discuss modifiable traditional risk factors, namely hypertension, dyslipidemia, diabetes mellitus and poor glycemic control, smoking, and physical inactivity. The prevalence of each risk factor and its relationship with CVD is described. Treatment recommendations are provided using evidence available from populations with CKD or evidence extrapolated from the general population when there are insufficient data on individuals with CKD.  相似文献   
86.
BACKGROUND: After open-chest cardiac surgery, ventricular function remains depressed (myocardial stunning). Catecholamines (epinephrine) improve ventricular function by increasing the intracellular Ca(2+) concentration. In parallel, the oxygen consumption is increased, so that the hitherto intact myocardium can be jeopardized. In the very insufficient ventricle, epinephrine can even become ineffective. Since Ca(2+) sensitizers provide another therapeutic avenue, the effects of epinephrine and levosimendan on postischemic hemodynamics were investigated. METHODS: After hemodynamic steady state, isolated, blood (erythrocyte-enriched Krebs-Henseleit solution)-perfused rabbit hearts were subjected to 25 min normothermic, no-flow ischemia and 20 min reperfusion. Heart rate (HR), cardiac output (CO), left ventricular pressure (LVP), coronary blood flow (CBF), and arterio-venous oxygen difference (AVDO(2)) were recorded during reperfusion and after administration of either epinephrine (n=16; 0.03 micromol), or levosimendan (n=11; 0.75 micromol) or epinephrine plus levosimendan (n=5). RESULTS: Epinephrine increased HR (19%, p=0.01) and improved hemodynamics in terms of CO (62%, p=0.0006), stroke volume SV (46%, p=0.02), stroke work W (158%, p=0.01), LVP(max) (58%, p=0.0001), maximal pressure increase dP/dt(max)(140%, p=0.0004), minimal pressure increase dP/dt(min) (104%, p=0.0002), LVP(ed) (-26%, p=0.02), and increased coronary resistance CR (31%, p=0.05). Epinephrine impaired hemodynamics in terms of AVDO(2) (+63%, p=0.003), myocardial oxygen consumption MVO(2) (+67%, p=0.0003) and MVO(2)/beat (+36%, p=0.01). External efficiency eta was increased by 92% (p=0.02). Levosimendan in postischemic hearts increased HR (32%, p=0.009) and improved hemodynamics in terms of CO (85%, p=0.01), SV (44%, p=0.03), W (115%, p=0.04), LVP(max) (95%, p=0.04), dP/dt(max) (133%, p=0.009), dP/dt(min) (121%, p=0.007), LVP(ed) (-63%, p=0.0006), and CR (-17%; n.s., p=0.1). It altered hemodynamics in terms of AVDO(2) (+7.0%; n.s., p=0.3) and MVO(2) (+32%, p=0.007) and MVO(2)/beat (+2.3%; n.s., p=0.4). External efficiency was increased by 307% (p=0.04). In five additional extremely dysfunctional rabbit hearts, epinephrine was ineffective. Additional levosimendan increased hemodynamics in terms of HR (56%; n.s., p=0.1), CO (159%, p=0.04), SV (89%, p=0.03), W (588%, p=0.02), LVP(max) (168%, p=0.03), dP/dt(max) (102%, p=0.005), dP/dt(min) (78%, p=0.006), LVP(ed) (-98%, p=0.0006), and CR (-50%, p=0.02). It altered hemodynamics in terms of AVDO(2) (-11%; n.s., p=0.05), MVO(2) (+131%, p=0.04) and MVO(2)/beat (+171%, p=0.03). External efficiency was increased by 212% (p=0.04). CONCLUSION: In contrast to epinephrine, levosimendan improves ventricular function without increasing oxygen demand, thereby considerably improving external efficiency. Even during epinephrine resistance in extremely dysfunctional hearts, levosimendan successfully improves ventricular function.  相似文献   
87.
Background and aims Since the introduction of endovascular aortic aneurysm repair (EVAR) for aortic aneurysms, the number of juxtarenal aortic aneurysms (JRA) has been growing steadily due to selection bias (neck morphology for EVAR). This case-match study compares the perioperative outcome and midterm results of suprarenally clamped JRA with infrarenal aortic aneurysms (AAA). Methods From 1997 to 2004, patients who received open surgery with suprarenal clamping for JRA were included in the study and compared to matched patients with infrarenal clamping (AAA). Measurements analyzed were the in-hospital mortality and morbidity. Midterm results were obtained through clinical investigation and magnetic resonance angiography imaging. Results Thirty-five patients (mean age, 68.4 years; 30 male and 5 female) received suprarenal cross-clamping for JRA. The overall in-hospital mortality for JRA and for the controls (AAA) with elective aortic repair was 4.5% (6.1% JRA; 3% AAA, p = 0.058). The morbidity of JRA was elevated according to the rate of pulmonary complications (p = 0.021) and the need for re-operation (p = 0.019). The mean follow-up time was 2.3 years (range, 8–96 months). At follow-up, 28 patients (80%) from the JRA group and 29 patients from the AAA group (82.9%) were alive. Conclusion Open aortic surgery for JRA with the need for suprarenal cross-clamping shows a slightly elevated in-hospital mortality rate without statistical significance and equal midterm mortality results in comparison with infrarenally clamped aortic aneurysms.  相似文献   
88.
Serial bone scintigraphy in Legg-Calvé-Perthes disease (LCP) has a good early prognostic value. So far, no intra- and inter-observer reliability study on this classification has been published. Serial technetium scintigraphy of the hips was performed in 40 children with LCP disease, and the hips were classified based on their scintigraphic patterns according to Conway. Forty hips were classified twice by six observers. The two assessments were made in a different order, with a minimum time interval of one month. Unweighted kappa coefficients were calculated. Only moderate reliability was measured: intra-observer reliability: kappa = 0.573 and inter-observer reliability: kappa = 0.525. Serial bone scintigraphy in LCP has an inter- and intra-observer reliability that is only moderate. The reliability is better than that observed for the radiological Catterall classification and head-at-risk factors, but worse than the reliability of the radiological Herring classification.  相似文献   
89.
We report evidence for a context- and not stimulus-dependent functional asymmetry in the left and right human auditory midbrain, thalamus, and cortex in response to monaural sounds. Neural activity elicited by left- and right-ear stimulation was measured simultaneously in the cochlear nuclei, inferior colliculi (ICs), medial geniculate bodies (MGBs), and auditory cortices (ACs) in 2 functional magnetic resonance imaging experiments. In experiment 1, pulsed noise was presented monaurally to either ear, or binaurally, simulating a moving sound source. In experiment 2, only monaural sounds were presented. The results show a modulation of the neural responses to monaural sounds by the presence of binaural sounds at a time scale of tens of seconds: In the absence of binaural stimulation, the left and right ICs, MGBs, and ACs responded stronger to stimulation of the contralateral ear. When blocks of binaural stimuli were interspersed in the sound sequence, the contralateral preference vanished in those structures in the right hemisphere. The resulting hemispheric asymmetry was similar to the asymmetry demonstrated for spatial sound processing. Taken together, the data demonstrate that functional asymmetries in auditory processing are modulated by context. The observed long time constant suggests that this effect results from a "top-down" mechanism.  相似文献   
90.
OBJECTIVE: Type 2 diabetes mellitus is a well-known risk factor in patients with severe coronary artery disease undergoing coronary artery bypass grafting (CABG). The aim of the study was to analyze the endothelial dysfunction in these patients by evaluating postoperative soluble inflammatory cytokines. METHODS: Patients undergoing CABG without (n=15, group A) and with (n=14, group B) diabetes mellitus were analyzed for their release of E-selectin, interleukin-6 (IL-6), and tumor necrosis factor (TNF) up to 3 days postoperatively. A pharmacokinetic quantitative kinetic evaluation (Kinetica 2000) of maximum concentrations (c(max)), time to reach c(max) (t(max)), area under the curve (AUC(0-inf)), and terminal elimination half time (t(1/2)) was performed using a non-compartmental model. RESULTS: There was no difference in preoperative plasma concentrations of the cytokines and in the postoperative kinetic analyses of TNF when comparing both groups. However, the release of IL-6 was restricted with c(max) of 1055+/-543 pg/ml for group B versus 2112+/-1532 pg/ml for group A (p< or =0.05), paralleled by a decrease in the absolute amount (AUC(0-inf)) of IL-6. The t(1/2) remained unaffected (13.9+/-6.6h and 12.7+/-4.6h, respectively). The AUC(0-inf) of E-selectin decreased by a factor of 1.7 (p< or =0.05) with unchanged c(max) but reduced t(1/2) (12.9+/-10h for group B vs 33.1+/-20.4h for group A; p< or =0.01) referring to an augmented endothelial uptake and degradation of E-selectin. CONCLUSIONS: CABG with extracorporeal circulation could be used to verify a specific endothelial dysfunction in diabetic patients characterized by an impaired release of IL-6 and an increased turnover of E-selectin.  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