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   14167篇
  免费   1061篇
  国内免费   40篇
耳鼻咽喉   196篇
儿科学   446篇
妇产科学   369篇
基础医学   2033篇
口腔科学   200篇
临床医学   1660篇
内科学   2436篇
皮肤病学   341篇
神经病学   1704篇
特种医学   410篇
外科学   1698篇
综合类   76篇
一般理论   19篇
预防医学   1658篇
眼科学   189篇
药学   815篇
  1篇
中国医学   18篇
肿瘤学   999篇
  2024年   39篇
  2023年   246篇
  2022年   368篇
  2021年   689篇
  2020年   458篇
  2019年   664篇
  2018年   725篇
  2017年   478篇
  2016年   529篇
  2015年   485篇
  2014年   634篇
  2013年   847篇
  2012年   1109篇
  2011年   1057篇
  2010年   551篇
  2009年   463篇
  2008年   686篇
  2007年   641篇
  2006年   608篇
  2005年   554篇
  2004年   489篇
  2003年   425篇
  2002年   435篇
  2001年   160篇
  2000年   123篇
  1999年   142篇
  1998年   92篇
  1997年   75篇
  1996年   85篇
  1995年   70篇
  1994年   58篇
  1993年   59篇
  1992年   73篇
  1991年   88篇
  1990年   75篇
  1989年   73篇
  1988年   45篇
  1987年   56篇
  1986年   48篇
  1985年   48篇
  1984年   33篇
  1983年   32篇
  1982年   32篇
  1981年   30篇
  1980年   25篇
  1979年   42篇
  1978年   24篇
  1977年   23篇
  1974年   34篇
  1972年   22篇
排序方式: 共有10000条查询结果,搜索用时 22 毫秒
101.
Myocardial tissue oxygen pressure (PmO2 ) and left anterior descending (LAD) artery blood flow were measured in dogs anesthetized with 1.5% isoflurane, and were then compared to brain tissue oxygen pressure (PbO2 ) and middle cerebral artery (MCA) blood flow during normocapnia, hypocapnia, and hypercapnia. A craniotomy was performed and a tissue probe (Codman, Inc.) that measures PO2, PCO2, and pH was inserted into the brain cortex in the MCA region (n = 8). Separately, after a thoracotomy, a probe was inserted into the middle myocardium of the left ventricle, within the distribution of the LAD, in eight dogs. Blood flow probes were placed on the LAD or MCA. Blood flow and tissue gases were measured during normocapnia (PaCO2 = 38 mm Hg), hypocapnia (PaCO2 = 26 mm Hg), and hypercapnia (PaCO2 = 53 mm Hg). Mean arterial pressure, heart rate, arterial gases, and pH were not different between brain and heart measurements. PbO2 was 21 +/- 9 mm Hg (mean +/- SD ), 40 +/- 16 mm Hg, and 47 +/- 11 mm Hg. PmO2 was 35 +/- 12 mm Hg, 40 +/- 14 mm Hg, and 48 +/- 15 mm Hg during hypocapnia, normocapnia, and hypercapnia respectively. During hypercapnia, LAD and MCA flow increased 50% and tissue oxygenation increased 20% ( P < .05). During hypocapnia, MCA flow and PbO2 decreased 50% ( P < .05), but LAD flow and PmO2 did not significantly change. These results indicated that LAD flow and myocardial PO2 were less responsive to hypocapnia than MCA flow and PbO2.  相似文献   
102.
BACKGROUND: Alcohol interventions decrease alcohol consumption and recurrent injury. The study hypotheses are (1) intoxicated passengers are similar to intoxicated drivers in crashes and driving under the influence of alcohol (DUI), and (2) DUI conviction rates after injury are low. METHODS: Intoxicated motor vehicle occupants hospitalized for injury in 1996-1998 were matched to the state traffic database for crashes and DUI. Drivers and passengers were compared for crashes and DUI in the 2 years preceding and 1 year after admission. Driver DUI citation at the time of admission was also recorded. A logistic regression model for crash and DUI probability was constructed. RESULTS: Six hundred seventy-four patients met inclusion criteria. In the 2 years preceding admission, passengers and drivers were equally cited for crashes (14.7% vs 19.3%, p = 0.12). In 1 year after admission, they were also equally cited (7.1% vs 7.7%, p = 0.92). Driver/passenger status was not a predictor by logistic regression; 13.4% of intoxicated drivers were convicted of DUI for the admitting crash. CONCLUSION: Intoxicated passengers and drivers are equally likely to be cited for crashes and DUI before and after admission for injury. Few admitted intoxicated drivers are convicted of DUI. Screening and intervention for all intoxicated crash occupants is warranted.  相似文献   
103.
OBJECTIVES: To assess the value of positron emission tomography (PET)/computed tomography (CT) with either (18)F-choline and/or (11)C-acetate, of residual or recurrent tumour after radical prostatectomy (RP) in patients with a prostate-specific antigen (PSA) level of <1 ng/mL and referred for adjuvant or salvage radiotherapy. PATIENTS AND METHODS: In all, 22 PET/CT studies were performed, 11 with (18)F-choline (group A) and 11 with (11)C-acetate (group B), in 20 consecutive patients (two undergoing PET/CT scans with both tracers). The median (range) PSA level before PET/CT was 0.33 (0.08-0.76) ng/mL. Endorectal-coil magnetic resonance imaging (MRI) was used in 18 patients. Nineteen patients were eligible for evaluation of biochemical response after salvage radiotherapy. RESULTS: There was abnormal local tracer uptake in five and six patients in group A and B, respectively. Except for a single positive obturator lymph node, there was no other site of metastasis. In the two patients evaluated with both tracers there was no pathological uptake. Endorectal MRI was locally positive in 15 of 18 patients; 12 of 19 responded with a marked decrease in PSA level (half or more from baseline) 6 months after salvage radiotherapy. CONCLUSIONS: Although (18)F-choline and (11)C-acetate PET/CT studies succeeded in detecting local residual or recurrent disease in about half the patients with PSA levels of <1 ng/mL after RP, these studies cannot yet be recommended as a standard diagnostic tool for early relapse or suspicion of subclinical minimally persistent disease after surgery. Endorectal MRI might be more helpful, especially in patients with a low likelihood of distant metastases. Nevertheless, further research with (18)F-choline and/or (11)C-acetate PET with optimal spatial resolution might be needed for patients with a high risk of distant relapse after RP even at low PSA values.  相似文献   
104.
Work‐based support has effects on family outcomes (Thompson, Kirk, & Brown, Stress and Health, 2005, 21, 199–207), suggesting that the effects of work‐based support are transmitted to the family environment through some mediating mechanism. This study examines two potential mediating mechanisms, emotional exhaustion and work interference with family (WIF). It was expected that women would report higher levels of work support, and work support would have a stronger relationship with outcomes for women. Gender as a moderator of the relationships between work support, and emotional exhaustion, WIF, and family environment (family cohesion, family conflict) was tested via regression analyses. Eighty‐one males (43.3 per cent) and 106 females (56.7 per cent), and their spouse/partners participated in the study. Women reported higher levels of coworker support than men, and support from supervisors predicted WIF only for women. Gender did not moderate the work support—family environment relationship. WIF, but not emotional exhaustion, mediated the relationship between supervisor and coworker support, and employee reports of family cohesion. Spouse/partner reports of family environment were not predicted by the study variables. Thus, work support reduces employee negative perceptions of the family environment through reduced work–family stress, and the impact is similar for men and women. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
105.
OBJECTIVES: This study compared the complications and the cancer control of elective nephron-sparing surgery (NSS) and radical nephrectomy (RN) in patients with a small (相似文献   
106.
INTRODUCTION: Infection after total hip replacement (THR) is a serious medical complication with significant negative ramifications for both the patient and the health care system. The prosthesis of antibiotic-loaded acrylic cement (PROSTALAC) was designed to treat the joint infection while maintaining functional movement in the hip. METHODS: We identified 28 patients treated for infected THR with the PROSTALAC system, by retrospective chart review. Preoperative and intraoperative cultures were taken to identify the causative organism. After PROSTALAC insertion, patients underwent at least 6 weeks of intravenous (IV) antibiotics. Prior to undergoing posttreatment cultures, patients were required to be antibiotic-free for a minimum of 6 weeks, with normal laboratory values. We defined resolution infection as retention of a joint prosthesis for a minimum of 2 years. RESULTS: Infection was identified in 28 patients in either the joint aspirate or intraoperative cultures. Of these patients, 2 failed to clear infection, requiring repeat PROSTALAC insertion. Two additional patients had positive 48-hour cultures post-second stage, treated with additional IV antibiotics. Retention of the post-PROSTALAC prosthesis is 100% at 2 years. CONCLUSION: PROSTALAC has acceptable infection resolution outcomes and appears effective for treating infected THR.  相似文献   
107.
Does early repair of small abdominal aortic aneurysms (AAAs) lead to faster aneurysm sac regression or less secondary intervention? Computed tomography scans and reconstructions from M2S of all patients undergoing endovascular AAA repair at our institution from 1996 to 2006 were retrospectively reviewed. A small aneurysm is defined as an aneurysm sac to renal diameter ratio of less than 2. There were 374 patients with endovascular AAA repair that had complete imaging studies. There were 75 patients (20%) with small AAAs; of those, 19 patients (25.3%) had endoleak compared with 108 patients (36.1%) with a large aneurysm ( P = .1). Over a mean follow-up time of 42 months (range, 1-109), 11 small AAAs (14.7%) had secondary interventions compared with 58 (19.4%) of the large AAAs (P = .41). Small AAAs at 5 years had a 2.5% volume sac regression but a 3.0% increase in diameter. Those with a large aneurysm had a slight increase in sac volume and diameter at 1 month (3.3%, 1.4%) and then steadily decreased to -13.4% and -8.8% at 5 years. Patients with Endologix (Endologix Inc., Irvine, Calif) devices have the most regression when compared with patients with AneuRx (Medtronic Inc., Minneapolis, Minn) and Talent (Medtronic Inc., Minneapolis, Minn) devices. Early endovascular intervention in small AAAs does not result in faster aneurysm sac regression or secondary intervention. Aneurysm sac regression is significantly affected by endoleak, aneurysm size, and device used.  相似文献   
108.

Background

Pulmonary hypertension (PH) is regarded as a risk factor for perioperative complications in patients undergoing noncardiac surgery.

Questions/Purposes

The objective of this retrospective case–control study was to evaluate the adverse outcomes of pulmonary hypertension patients undergoing elective unilateral hip replacements.

Methods

We performed a retrospective case–control study of total hip replacement patients with pulmonary hypertension (cases) and without pulmonary hypertension (control). From the years 2003 to 2008, we identified a total of 132 patients undergoing primary total hip replacements with a diagnosis of pulmonary hypertension (right ventricular systolic pressure >35). The primary outcome assessed was the incidence of adverse events that occurred during the postoperative hospital stay. Secondary outcomes studied included length of hospital stay, mortality, and ability to reach certain physical therapy milestones.

Results

The PH group had significantly more adverse events than the control group. Nonlethal cardiac dysrhythmias comprised the most common adverse outcome among the PH group. Overall, the PH group had a morbidity rate of 34.7% while the control had a rate of 21%. The PH group had longer hospital stay (6.7 days vs. 5.9). Both groups had zero mortality during the hospital stay. The PH group had comparable rehabilitation recovery times than the control group.

Conclusion

This retrospective case–control study demonstrates that pulmonary hypertension patients undergoing total hip arthroplasty are more prone to adverse outcomes, especially cardiac dysrhythmias, and longer hospital stays.  相似文献   
109.
Molecular subtyping may inform on prognosis and treatment response in bladder cancer. However, intratumoral molecular heterogeneity is not well studied in this disease and could complicate efforts to use molecular subtyping to guide patient management. To investigate intratumoral heterogeneity in bladder cancer, we examined molecular subtypes in a consecutive, retrospective cystectomy series of histologic variant bladder cancers and conventional urothelial carcinomas co-occurring with them. Molecular subtypes were assigned as per the approach reported by Lund University, an approach that incorporates cell cycle alterations and markers of differentiation, to give the urothelial-like, genomically unstable, basal-squamous, mesenchymal-like, and neuroendocrine-like subtypes. The majority (93%) of tumors were classified as urothelial like, genomically unstable, or basal squamous. Among patients with more than one tumor histology, 39% demonstrated molecular heterogeneity among the different tumor histologies. This was greatest for the basal-squamous subtype, 78% of which co-occurred with either urothelial-like or genomically unstable carcinoma (among cases with multiple histologies). In contrast, there was no co-occurrence of urothelial-like and genomically unstable carcinoma in the same patient. The findings indicate that bladder cancer is often molecularly heterogeneous, particularly in the basal-squamous subtype. This raises the concern for sampling error in laboratory tests that guide therapy based on molecular subtyping.Patient summary: In this report, we investigated molecular diversity among different areas from the same tumor in patients with bladder cancer. We found that different areas from the same tumor are often molecularly different. We conclude that this biological diversity must be taken into account when interpreting clinical molecular tests performed on bladder cancer samples.  相似文献   
110.
BACKGROUND AND PURPOSE: Rotational angiography (RA) and digital subtraction angiography (DSA) together may depict more intracranial aneurysms than DSA alone. We compared the diagnostic value of 3D RA and biplanar DSA in detecting, classifying, and planning treatment for ruptured intracranial aneurysms. METHODS: A total of 53 patients with acute subarachnoid hemorrhage (Hunt and Hess grades I-V) underwent angiography with both methods. DSA was performed in two to six standard projections in every vascular territory. Three-dimensional RA datasets were evaluated by using surface-shaded display and maximum intensity projection. The usefulness of DSA images and 3D datasets in detecting aneurysms (number, configuration) and treatment planning were retrospectively analyzed in a blinded manner. RESULTS: In 42 patients, 56 aneurysms were detected, (one to five per patient; size, 0.6-20.4 mm); no aneurysm was found in 11 patients. RA revealed seven aneurysms not seen at conventional DSA. RA failed to depict one aneurysm visible only in a compression series. Delineation of the aneurysmal neck improved with RA in 71% of cases; the parent vessel and its relationship to adjacent vessels was demonstrated better with RA than with DSA in 45% and 50%, respectively. Endovascular treatment was proposed in nine patients; microsurgical therapy, in 26. In seven patients, both options were rated as being equal. Actual treatment consisted of eight endovascular procedures and 30 neurosurgical operations. Four patients died before therapy. CONCLUSION: Compared with DSA, 3D RA allows more exact depiction of anatomic details that are important in planning surgery and interventional therapy for intracranial aneurysms. RA depicted more aneurysms.  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