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   10583篇
  免费   754篇
  国内免费   167篇
耳鼻咽喉   144篇
儿科学   260篇
妇产科学   192篇
基础医学   1719篇
口腔科学   148篇
临床医学   950篇
内科学   2185篇
皮肤病学   343篇
神经病学   920篇
特种医学   713篇
外科学   1249篇
综合类   64篇
现状与发展   2篇
一般理论   1篇
预防医学   490篇
眼科学   238篇
药学   972篇
中国医学   149篇
肿瘤学   765篇
  2023年   87篇
  2022年   324篇
  2021年   479篇
  2020年   228篇
  2019年   341篇
  2018年   356篇
  2017年   276篇
  2016年   435篇
  2015年   530篇
  2014年   629篇
  2013年   720篇
  2012年   981篇
  2011年   934篇
  2010年   562篇
  2009年   444篇
  2008年   607篇
  2007年   549篇
  2006年   521篇
  2005年   399篇
  2004年   352篇
  2003年   278篇
  2002年   261篇
  2001年   149篇
  2000年   152篇
  1999年   105篇
  1998年   59篇
  1997年   41篇
  1996年   39篇
  1995年   35篇
  1994年   31篇
  1993年   25篇
  1992年   45篇
  1991年   47篇
  1990年   50篇
  1989年   53篇
  1988年   21篇
  1987年   37篇
  1986年   34篇
  1985年   34篇
  1984年   26篇
  1983年   20篇
  1979年   19篇
  1976年   11篇
  1973年   11篇
  1972年   15篇
  1971年   19篇
  1970年   14篇
  1969年   13篇
  1968年   10篇
  1966年   12篇
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
991.
The neurotoxicity of methylene chloride (MC) is of special interest because of its acute effects on the central nervous system (CNS) and its metabolic conversion to carbon monoxide. A cohort study of retired airline mechanics was conducted to examine the hypothesis that long term exposure to MC results in lasting effects on the CNS. Retirees were studied to eliminate effects of current occupational exposures. The total retiree population (n = 1758) was surveyed to identify mechanics who met specific occupational, demographic, and medical criteria. A group of eligible retirees having long term exposure to MC and another group with low probability of exposure to solvents were given a comprehensive battery of physiological and psychological tests. The exposure groups were similar for all potential confounders that were measured. No statistically significant differences between groups were detected on outcome measures, although subtle differences in attention and memory were identified. Thus no firm evidence was found to support the hypothesis of lasting CNS effects in retired mechanics with long term exposure to MC.  相似文献   
992.

Purpose

To study whether anaplastic astrocytomas that are nonenhancing and/or well‐circumscribed (expansive) are associated with a better prognosis.

Materials and Methods

We retrospectively identified 59 patients with pathologically confirmed World Health Organizaiton (WHO) grade III anaplastic astrocytoma who underwent craniotomy at our institution from 1995 through 2006. We assessed prognostic variables including age, enhancement (EAA—34 patients) vs. nonenhancement (NEAA—25 patients), MR growth patterns (expansive [28 patients] vs. mixed/infiltrative [31 patients]), recursive partitioning analysis (RPA) class, resection extent, and addition of chemotherapy. Primary outcome measure was survival.

Results

Kaplan‐Meier curves showed improved survival in NEAA, expansive tumors, and RPA 1 class patients. Within RPA class I patients, expansive growth pattern remained a significant advantage in survival time. Examining extent of resection also showed that patients with gross total resections (GTR) had a better prognosis. A multivariate (Cox proportional hazards) analysis showed that patient age and expansive tumor phenotype affected outcome, whereas RPA class, enhancement, and GTR did not.

Conclusion

Circumscribed growth in histologically proven anaplastic astrocytoma, which has not been emphasized in past studies, has a considerable survival advantage. J. Magn. Reson. Imaging 2008;28:1311–1321. © 2008 Wiley‐Liss, Inc.  相似文献   
993.
In utero development of the fetal gall bladder in the Korean population.   总被引:1,自引:0,他引:1  
OBJECTIVE: To provide reference ranges of the fetal gall bladder in the Korean population. MATERIALS AND METHODS: Fetal gall bladder development was evaluated in well-dated, non-anomalous fetuses in the Korean population between February and April 2003 and the visualization rate and reference values were determined from the obtained data. RESULTS: The visualization rate of the fetal gall bladder increased as gestation advanced to a plateau above 90%, which was maintained between 16 and 34 weeks. The measured parameters from the fetal gall bladder had a significant positive relationship with gestational age (p = 0.000 for all cases), and the correlation of length and area with the gestational age (r = 0.741 and r = 0.690, respectively) was better than the correlation of width, height, and volume with gestational age. The repeatability coefficients and coefficients of variation between the two operators were 5.56 mm and 12.9% for the length and 344.11 mm(2) and 33.52% for the area. The median length of the fetal gall bladder in the Korean population was not significantly different from the mean length of gall bladders in the Caucasian and African-American populations (p = 0.915). CONCLUSION: We have provided reference values for the fetal gall bladder throughout the gestation period in the Korean population.  相似文献   
994.
OBJECTIVE: To evaluate the dynamic changes of the power Doppler (PD) in acute renal vein occlusion and recanalization in a canine model. MATERIALS AND METHODS: We performed a PD of the kidney during graded renal vein occlusion and recanalization induced by balloon inflation and deflation in nine dogs. The PD images were transferred to a personal computer, and the PD signals were quantified. RESULTS: We observed the temporal change of the PD signal during renal vein occlusion and recanalization, with a decrease in the PD signal during occlusion and an increase during recanalization. The mean PD signal decreased gradually as the renal vein was occluded, and conversely increased gradually with sequential relief of occlusion. The sequential change of the mean value of the PD signal was statistically significant. CONCLUSION: The PD can detect a change in renal blood flow during acute renal vein occlusion and recanalization in a canine model. The PD may be used as a helpful tool for the early detection of acute renal vein thrombosis and the monitoring of renal perfusion.  相似文献   
995.
PURPOSE: To determine the safety of venous intervention and the incidence of complications in patients undergoing venous interventional radiological procedures while receiving anticoagulant therapy. METHOD: Data were collected prospectively for a 1-year period. One hundred patients receiving anticoagulant therapy underwent interventional radiological procedures requiring venous cannulation. Of these, 87 had documented prolonged bleeding times. There were 50 inferior vena cavograms obtained and filters placed (29 transfemoral, 21 transjugular), and 50 transfemoral pulmonary angiogram obtained, all in patients with thrombo-embolic disease who were receiving anticoagulant therapy. In most cases venous access was achieved with real-time sonographic guidance. RESULTS: Venous access was gained in all patients in all groups. There were 41/50 filter placements and 46/50 pulmonary angiograms performed in the patients with prolonged clotting times in or above the therapeutic range. There were no cases of arterial puncture and no cases of venous bleeding either during or after the procedures. No other complications were recorded. CONCLUSION: Venous intervention in patients receiving therapeutic anticoagulation is safe, with no complications reported in our series. There is no need to discontinue anticoagulant therapy in patients with life-threatening thrombo-embolic disease. Real-time sonographic guidance greatly facilitates venous cannulation and avoids inadvertent arterial puncture.  相似文献   
996.
Twenty temporal bones (TBs) were removed from autopsy cases and prepared for immunohistochemical examination. Ten TBs were free of ear disease whereas the other ten TBs showed the signs of chronic otitis media. Expression of markers for monocyte-macrophages¶(25F9, 27E10) and natural killer cells (anti-Leu-11) was examined immunohistochemically. There were no specific positive stainings with 25F9 or anti-Leu-11 antibodies in any of the specimens. Staining for 27E10 was found to be negative in each section obtained from normal cochlea. However, 27E10 positivity was detected in three of ten TBs with signs of chronic ear inflammation. This positivity can be explained by two theories: (1) activated monocytes can enter the inner ear from the systemic circulation as a consequence of chronic antigen challenge; (2) mesothelial cells could become activated as a result of a cross-reaction, with resultant positivity. Development of sensorineural hearing loss in some cases of chronic otitis media may be due to these immunological reactions.  相似文献   
997.
Renal cell carcinoma (RCC) may present as metastatic disease. However, RCC with solitary sternal metastasis is rare. We report a rare case of RCC with synchronous solitary sternal metastasis. The patient underwent radical nephrectomy, sternal tumour resection and reconstruction as a one‐stage procedure. The role of open sternal biopsy is also described. Review of the literature was carried out and a reasonably lengthy survival was observed. We concluded that radical surgical resection and reconstruction may offer the best chance of survival in managing RCC with solitary sternal metastasis in renal cell carcinoma.  相似文献   
998.
Disseminated mycobacterial infection after bacillus Calmette-Guerin (BCG) vaccination is a very rare disorder, occurring mostly in patients with immunologic deficiency. We report a case of disseminated BCG infection in a 16-month-old girl with severe combined immunodeficiency. Plain radiographs showed multiple osteolytic lesions in the femora, tibiae, humerus, and phalanges. Abdominal sonography and CT scanning revealed multiple nodules in the spleen, and portocaval lymphadenopathy.  相似文献   
999.
1000.
Y T So  R K Olney  M J Aminoff 《Muscle & nerve》1990,13(11):1032-1036
We studied 20 asymptomatic control subjects and 14 patients with clinically unequivocal cervical radiculopathy to compare the diagnostic value of thermography with that of electromyography. We measured the average skin temperature of designated regions over the neck, shoulder, and upper extremities. We then compared the temperature between corresponding regions of the two limbs, and between fingers innervated by different roots in the same hand. Thermography was abnormal in 6 patients (43%), whereas electromyography was abnormal in 10 (71%). Thermographic abnormalities were seen only in the hands and fingers, and the pattern did not follow the dermatome of the clinically involved cervical root. When compared to electromyography, thermography provided no additional diagnostic information. Thus, thermography does not have an established role in the evaluation of patients with cervical radiculopathy.  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