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   3305篇
  免费   191篇
  国内免费   13篇
耳鼻咽喉   64篇
儿科学   222篇
妇产科学   52篇
基础医学   275篇
口腔科学   55篇
临床医学   321篇
内科学   804篇
皮肤病学   46篇
神经病学   157篇
特种医学   282篇
外科学   474篇
综合类   60篇
预防医学   131篇
眼科学   119篇
药学   158篇
  1篇
中国医学   2篇
肿瘤学   286篇
  2023年   17篇
  2022年   40篇
  2021年   106篇
  2020年   52篇
  2019年   92篇
  2018年   110篇
  2017年   61篇
  2016年   69篇
  2015年   88篇
  2014年   129篇
  2013年   141篇
  2012年   196篇
  2011年   177篇
  2010年   118篇
  2009年   130篇
  2008年   172篇
  2007年   135篇
  2006年   118篇
  2005年   113篇
  2004年   93篇
  2003年   75篇
  2002年   69篇
  2001年   51篇
  2000年   47篇
  1999年   61篇
  1998年   92篇
  1997年   91篇
  1996年   101篇
  1995年   67篇
  1994年   63篇
  1993年   51篇
  1992年   51篇
  1991年   45篇
  1990年   32篇
  1989年   58篇
  1988年   57篇
  1987年   59篇
  1986年   29篇
  1985年   44篇
  1984年   27篇
  1983年   24篇
  1982年   18篇
  1981年   17篇
  1980年   9篇
  1979年   8篇
  1978年   11篇
  1977年   10篇
  1976年   14篇
  1975年   9篇
  1970年   8篇
排序方式: 共有3509条查询结果,搜索用时 0 毫秒
81.
82.
Infection with SARS-CoV-2 leading to COVID-19 induces hyperinflammatory and hypercoagulable states, resulting in arterial and venous thromboembolic events. Deep vein thrombosis (DVT) has been well reported in COVID-19 patients. While most DVTs occur in a lower extremity, involvement of the upper extremity is uncommon. In this report, we describe the first reported patient with an upper extremity DVT recurrence secondary to COVID-19 infection.  相似文献   
83.
Purpose

Idiopathic junctional ectopic tachycardia (JET) is typically refractory to antiarrhythmic agents. Catheter ablation for JET is feasible but is associated with high risk of unintended atrioventricular (AV) block. There is limited data on the appropriate procedural technique and clinical outcomes with catheter ablation for idiopathic JET in adults.

Methods

This is a multicenter, retrospective study of all adult patients (age?≥?18 years) who underwent catheter ablation for idiopathic JET. Patient, procedural characteristics, and long-term outcomes were evaluated.

Results

Fifteen patients [radiofrequency ablation (RF)?=?14 and cryoablation?=?1) were treated with catheter ablation. The median age was 58 years with 67% males. All patients underwent mapping of the right atrium and the aortic cusps prior to energy delivery. The location of earliest activation in relation to the atrioventricular (AV) node was postero-superior in 73% (11/15), posterior in 13% (2/15), and superior in 13% (2/15) respectively. Acute success was 100%. Arrhythmia recurrence occurred in 53% (8/15) all of whom underwent a repeat ablation. High-grade AV block requiring permanent pacemaker occurred in 20% (3/15). At 12-month follow-up in the redo-ablation group, 37.5% (3/8) had recurrence of the arrhythmia two of which underwent a third ablation procedure.

Conclusion

Catheter ablation of idiopathic JET in adults is associated with a high rate of recurrence requiring multiple procedures and high risk of AV block requiring a permanent pacemaker. Mapping and ablation of the non-coronary cusp can be considered as the arrhythmia was controlled in 3 patients with no inadvertent AV block.

  相似文献   
84.
85.
Plasma levels of plasminogen activator inhibitor type-1 (PAI-1), beta- thromboglobulin (beta TG), and fibrinopeptide A (FPA) were followed over 24 hours in 30 patients treated with alteplase for acute myocardial infarction. Samples were taken at baseline (T Oh), after 90 minutes (under alteplase, no heparin, T 1.5h), after 120 minutes (under alteplase and heparin, T 2h), 30 minutes after thrombolytic therapy (T 3.5h), as well as 12 hours (T 12h) and 24 hours (T 24h) after baseline. PAI-1 antigen levels (55 +/- 9 ng/mL at T Oh, mean +/- SEM) decreased to 35 +/- 5 (T 1.5h) and 40 +/- 6 (T 2h) ng/mL under alteplase, before increasing to 84 +/- 22 (T 3.5h), 130 +/- 30 (T 12h), and 64 +/- 7 (T 24h) ng/mL after therapy, P less than .001. A high baseline PAI-1 activity (18 +/- 3 ng/mL) decreased to 2.0 +/- 0.4 (T 1.5h) and 1.7 +/- 0.2 (T 2h) under alteplase and increased to 32 +/- 5 (T 12h) and 19 +/- 3 (T 24h) ng/mL after therapy (P less than .0001). beta TG levels (339 +/- 105 ng/mL at T Oh) decreased to 203 +/- 48 (T 2h), 154 +/- 51 (T 3.5h), 187 +/- 40 (T 12h), and 142 +/- 32 (T 24h) ng/mL under heparin (P less than .01). FPA levels (34 +/- 9 ng/mL at T Oh) increased to 85 +/- 15 ng/mL under alteplase alone (T 1.5h) and normalized under heparin (11 +/- 4, 6 +/- 2, 4 +/- 2, and 3 +/- 1 ng/mL at T 2h, T 3.5h, T 12h, and T 24h, respectively). A high level of FPA at T 3.5h correlated with reocclusion (33 +/- 12 ng/mL, n = 4 v 2.9 +/- 0.5 ng/mL, n = 21, P less than .005). We conclude that plasma levels of PAI- 1 antigen as well as activity markedly increase after alteplase therapy of acute myocardial infarction. The high activity of PAI-1 and decreasing beta TG levels suggest that platelets do not contribute significantly to this phenomenon. The marked increase of FPA levels under recombinant tissue-type plasminogen activator alone and its normalization under heparin emphasize the important role of concomitant anticoagulation in controlling further intravasal fibrin generation under alteplase.  相似文献   
86.

Purpose of review

In this review, we provide a summary of the recently published literature on various methods of preventing contrast-induced acute kidney injury (CI-AKI) and radiation-related injuries associated with cardiac catheterization and percutaneous coronary intervention (PCI).

Recent findings

The overall reported incidence of CI-AKI is declining, primarily due to adaptation of a standardized definition for CI-AKI as well as implementation of pre-procedural protocols to prevent or decrease the risk of CI-AKI. The implementation of increasing awareness and establishing radiation protection culture has been shown to be effective measures in reducing radiation exposure.

Summary

Coronary angiography and PCI are valuable diagnostic and therapeutic tools in cardiovascular medicine. Accurate imaging of the coronary arteries in cardiac catheterization is dependent on the use of intravascular injection of iodinated contrast media and fluoroscopic imaging. Patients undergoing diagnostic and interventional cardiac catheterization may be exposed to a substantial amount of contrast media and ionizing radiation. Administration of contrast media is correlated with increased risk of CI-AKI, and exposure to radiation is known to be associated with a spectrum of acute and chronic tissue injuries.
  相似文献   
87.
Gronthos  S; Simmons  PJ 《Blood》1995,85(4):929-940
Factors that regulate the growth and development of primitive bone marrow stromal cell precursors are not well defined. We have examined 25 purified recombinant growth factors for their ability to initiate and support clonogenic growth of fibroblast colony-forming cells (CFU- F) from adult human bone marrow. Assays were performed using bone marrow mononuclear cells (BMMNC) enriched in CFU-F by magnetic- activated cell sorting (MACS) using the monoclonal antibody (MoAb) STRO- 1. A serum-deprived assay was developed to avoid components of fetal calf serum (FCS) that may mask or otherwise modify the response of CFU- F to exogenously added factors. L-ascorbate and the glucocorticoid dexamethasone were found to be essential for CFU-F colony development under serum-deprived conditions. Importantly, clonogenic growth of CFU- F in this culture system was absolutely dependent on an exogenous source of growth factor. Platelet-derived growth factor-BB (PDGF) and epidermal growth factor (EGF) demonstrated the greatest ability to support colony growth. Colony formation was dose-dependent, with half- maximal colony numbers at approximately 0.2 ng/mL for either factor and plateau numbers at concentrations in excess of 1.0 ng/mL. Simultaneous addition of PDGF and EGF had no effect on the number of colonies initiated but resulted in dose-dependent increases in mean colony diameter that were significant (P < or = .05) when compared with the effect of either factor alone or with the size of colonies elicited in control cultures by 20% FCS. Fluorescence-activated cell sorting (FACS) of BMMNC using MoAbs to the alpha chain of the PDGF receptor and to the EGF receptor in combination with the Moab STRO-1 demonstrated constitutive expression of both receptors by greater than 90% on CFU-F. Receptors for insulin-like growth factor-1 (IGF-1) and nerve growth factor (NGF) were also detected on STRO-1+ CFU-F, but in vitro both IGF- 1 and NGF did not support colony growth. This report demonstrates the development of a simple, reproducible, and stringent culture system for the growth and assay of stromal precursors under serum-deprived conditions and represents an important prerequisite for future studies of the role of growth factors in the regulation of stromal cell proliferation, differentiation, and development.  相似文献   
88.
To study the effect of interleukin-1 (IL-1) beta on the proliferation of hematopoietic progenitor cells (HPC) in long-term bone marrow cultures (LTBMC), stromal cell layers were established from normal human bone marrow. Autologous cryopreserved mononuclear phagocyte- and T-lymphocyte-depleted bone marrow cells were reinoculated on the stromal layers in fresh culture medium, with or without the addition of human IL-1 beta (30 U/mL). Once a week, half of the culture supernatant was replaced with fresh culture medium with or without IL-1, and all nonadherent cells were returned to the flasks. At weekly intervals during a period of 5 weeks, one culture was sacrificed to determine the total number of cells and hematopoietic progenitor cells, present in the adherent and the nonadherent cell fractions. In IL-1-stimulated cultures, the number of cells recovered during a period of 5 weeks exceeded the number of cells in unstimulated control cultures by 1.5 times. This difference was attributed to a twofold increase in the number of adherent cells. The number of HPC recovered from IL-1- stimulated cultures was not different from that recovered from controls. The levels of colony-stimulating activity (CSA) in supernatants from IL-1-stimulated cultures were significantly higher than those in supernatants from control cultures. These results indicate that IL-1 enhances the recovery of cells in LTBMC by stimulating the proliferation of HPC with the concurrent release of CSA from stromal cells, without diminishing the number of HPC.  相似文献   
89.
ObjectivesMost economic evaluations of chemotherapies for ovarian cancer patients have used hypothetical cohorts or randomized control trials, but evidence integrating real-world survival, cost, and utility data is limited.MethodsA propensity score–matched cohort of 6856 elderly (≥65 years) ovarian cancer patients diagnosed from 1991 to 2005 from the Surveillance, Epidemiology, and End Results-Medicare data cohort were included. Treatment regimens (i.e., no chemotherapy, platinum-based only, platinum plus taxane, and other nonplatinum) were identified in the 6 months postdiagnosis. Patients were followed until death or end of study (December 2006). Effectiveness was measured in quality-adjusted life-years (QALYs), and total health care costs were measured by using a payer’s perspective (2009 US dollars). Methodological and statistical uncertainties were accounted by including alternative scenarios (for utility values) and net monetary benefit approach. Incremental cost-effectiveness ratios (ICERs) were calculated, and stratified analyses were performed by tumor stages and age groups.ResultsOn comparing the platinum-based group versus no chemotherapy, we found that the ICER was $30,073/QALY and $58,151/QALY for early- and late-stage disease, respectively, while other nonplatinum and platinum plus taxane groups were dominated (less effective and more costly). Similar results were found across alternative scenarios and age groups. For patients 85 years or older, platinum plus taxane, however, was not dominated by the platinum-based group, with an ICER of $133,892/QALY.ConclusionsFollowing elderly ovarian cancer patients over a lifetime using real-world longitudinal data and adjusting for quality of life, we found that treatment with platinum-based regimen was the most cost-effective treatment alternative.  相似文献   
90.

PURPOSE

Metabolic, hormonal, and hemostatic changes associated with pregnancy loss (stillbirth and miscarriage) may contribute to the development of cardiovascular disease (CVD) in adulthood. This study evaluated prospectively the association between a history of pregnancy loss and CVD in a cohort of postmenopausal women.

METHODS

Postmenopausal women (77,701) were evaluated from 1993–1998. Information on baseline reproductive history, sociodemographic, and CVD risk factors were collected. The associations between 1 or 2 or more miscarriages and 1 or more stillbirths with occurrence of CVD were evaluated using multiple logistic regression.

RESULTS

Among 77,701 women in the study sample, 23,538 (30.3%) reported a history of miscarriage; 1,670 (2.2%) reported a history of stillbirth; and 1,673 (2.2%) reported a history of both miscarriage and stillbirth. Multivariable-adjusted odds ratio (OR) for coronary heart disease (CHD) for 1 or more stillbirths was 1.27 (95% CI, 1.07–1.51) compared with no stillbirth; for women with a history of 1 miscarriage, the OR = 1.19 (95% CI, 1.08–1.32); and for 2 or more miscarriages the OR = 1.18 (95% CI, 1.04–1.34) compared with no miscarriage. For ischemic stroke, the multivariable odds ratio for stillbirths and miscarriages was not significant.

CONCLUSIONS

Pregnancy loss was associated with CHD but not ischemic stroke. Women with a history of 1 or more stillbirths or 1 or more miscarriages appear to be at increased risk of future CVD and should be considered candidates for closer surveillance and/or early intervention; research is needed into better understanding the pathophysiologic mechanisms behind the increased risk of CVD associated with pregnancy loss.  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