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   1105篇
  免费   121篇
  国内免费   2篇
耳鼻咽喉   14篇
儿科学   39篇
妇产科学   18篇
基础医学   131篇
口腔科学   17篇
临床医学   137篇
内科学   157篇
皮肤病学   18篇
神经病学   118篇
特种医学   107篇
外科学   146篇
综合类   46篇
一般理论   1篇
预防医学   130篇
眼科学   26篇
药学   65篇
中国医学   1篇
肿瘤学   57篇
  2022年   12篇
  2021年   23篇
  2020年   15篇
  2019年   21篇
  2018年   30篇
  2017年   19篇
  2016年   14篇
  2015年   17篇
  2014年   28篇
  2013年   34篇
  2012年   60篇
  2011年   45篇
  2010年   30篇
  2009年   30篇
  2008年   49篇
  2007年   46篇
  2006年   48篇
  2005年   37篇
  2004年   38篇
  2003年   43篇
  2002年   30篇
  2001年   29篇
  2000年   33篇
  1999年   13篇
  1998年   13篇
  1997年   11篇
  1996年   20篇
  1995年   17篇
  1994年   13篇
  1993年   15篇
  1992年   26篇
  1991年   29篇
  1990年   25篇
  1989年   30篇
  1988年   25篇
  1987年   29篇
  1986年   32篇
  1985年   25篇
  1984年   16篇
  1983年   9篇
  1982年   10篇
  1981年   16篇
  1980年   13篇
  1979年   15篇
  1978年   15篇
  1976年   9篇
  1975年   12篇
  1974年   10篇
  1973年   10篇
  1967年   8篇
排序方式: 共有1228条查询结果,搜索用时 15 毫秒
111.
AIM: The longevity of peritoneal dialysis (PD) is limited by technique failure and patient mortality. The authors assessed the influence of baseline and time-averaged fluid removal on patient, technique and death-censored technique survival. METHODS: Peritoneal and total fluid removal was measured 1 month after commencing PD, then 6 monthly, in 225 incident patients (mean age 55.3+/-15.8 years, 52% male). A Cox proportional hazards model regression analysis was performed to identify variables independently predictive of technique and patient survival. RESULTS: Seventy (31.9%) patients were transferred to haemodialysis and 39 (17.63%) died. Technique survival was greatest in the middle tertile of baseline total fluid removal (mean survival time 3.5 vs 2.5 and 2.2 years for the lower and upper tertiles, respectively, log rank 6.5, P=0.039). The middle tertile of both baseline and time-averaged total fluid removal were significant predictors of PD survival (adjusted hazard ratio (HR) 0.476, 95% CI 0.286-0.795, P=0.005 relative to the upper tertile and HR 0.573, 95% CI 0.350-0.939, P=0.027 for baseline and time-averaged, respectively). Other significant variables on multivariate analysis were body mass index (HR 1.044 per kg/m2, 95% CI 1.005-1.084, P=0.028), creatinine (HR 0.999 per micromol, 95% CI 0.998-1.000, P=0.048) and residual Kt/V (HR 0.418, 95% CI 0.233-0.747, P=0.003). Patient survival was not affected by fluid removal. CONCLUSION: Patients with moderate total fluid removal both at baseline and throughout their PD career have improved technique survival. Attention should be paid to optimizing total fluid removal.  相似文献   
112.
BACKGROUND AND OBJECTIVES: This study aimed to identify the proportion of patients with breast cancer who do not undergo primary operative treatment, to identify the reasons surgery is not performed, and to determine the outcome for this group of patients. METHODS: Data was obtained from the Bedford Breast Cancer Registry for all non-metastatic patients presenting between January 1990 and December 2004 who were initially treated non-operatively. Robust diagnostic, therapeutic, and follow-up data on all patients was collected prospectively during this period. RESULTS: One hundred and eighty-five out of 2110 episodes of breast cancer were treated non-operatively during this period. Sixty-eight percent of patients were unfit for surgery, 15% had inoperable tumours, and 17% refused surgical intervention. Median survival and 5-year survival rate for all non-operative patients were 3.7 years and 41.2%. Median survival for inoperable patients was 3.7 years, compared with 3.5 years for those unfit for surgery and 4.2 years for those who refused surgery. The 5-year survival rate for patients refusing surgery was 43%, compared with 61% for a matched group of patients undergoing standard surgical therapy. CONCLUSIONS: This study provides useful data on the reasons for, and outcome of, the non-operative management of breast cancer.  相似文献   
113.
114.
115.
Simple tests of lung function may be misleading in the assessment of patients with interstitial lung disease. Eight patients are described with cryptogenic fibrosing alveolitis (histologically proven in four) with severe breathlessness and low gas transfer (median DLCO 32.4%, range 9.2 to 35.3%, % predicted) in whom lung volumes were preserved [median VC 98.7, range 67.5-131.1%; median TLC 92.5, range 88.1 to 121.2, (% predicted)], and in whom there was no evidence of airflow obstruction [median FEV1/FVC 84.6, range 68-116 (% predicted)]. All were current or ex-heavy smokers. Thoracic high resolution computed tomography revealed upper zone emphysema, the extent of which was not appreciated using conventional chest radiography. The atypical physiological and radiological features can be explained by coincidental cryptogenic fibrosing alveolitis and emphysema and high resolution computed tomography was valuable in the assessment of these patients.  相似文献   
116.
A triplet gestation was treated with Motrin for oral tocolysis. A significant reduction of amniotic fluid was observed, but this was corrected by stopping the drug. A cause-and-effect relationship was established by restarting the Motrin and observing the same development of oligohydramnios, which again returned to normal with discontinuation of the drug.  相似文献   
117.
118.
Concentric coil arrays for parallel MRI.   总被引:1,自引:0,他引:1  
A new type of coil array is proposed that consists of concentrically placed coil elements, each of which is characterized by symmetrically arranged lobes that have alternating current directions. Symmetries in the coil elements' conductor paths allow for the minimization of mutual inductance and noise correlations. In addition, the concentric arrangement of the coil elements provides spatial encoding capabilities in multiple directions, which is valuable when arrays are used with parallel MRI. Simulations are presented that describe the signal-to-noise ratio (SNR) properties of individual concentric array elements, and a four-element prototype concentric array is constructed. This prototype array is compared experimentally with three alternative four-element array designs. The overall SNR of the concentric array is comparable to the SNR of the competing arrays. Reconstruction of twofold undersampled data using the concentric array yields an average g-factor of less than 1.3 in all directions parallel to the plane of the array. There is some degradation in performance when threefold undersampled data are reconstructed, but the array still shows substantial directional invariance compared to alternative designs. Both fully-sampled and undersampled cardiac images acquired using the concentric array are shown. These results suggest that concentric structures can be useful tools for designing specialized coil arrays for parallel MRI.  相似文献   
119.
120.
A sample of 100 undergraduate students at a southern college campus were employed to answer computer-administered questions once a week for 20 weeks. This facility was used to collect both intensive and comprehensive data to describe respondents' drinking and its correlates. Although women were somewhat less likely to be abstainers than were men, women were disproportionately represented among moderate-only drinkers and men were overrepresented among heavy drinkers. The data indicate that the change in respondents' reported drinking was quite volatile in the transition from high school to college. Heavy-drinking college students reported that they drank in bars accompanied by friends. Different types of drinkers (e.g., moderate, infrequent, heavy) attributed different motives to drinking as well as to sometimes abstaining, but they held similar antialcohol beliefs. The drinking-related variables of friends explained more of the variance in respondents' drinking than did those of their parents. However, the variance explained by the parents' drinking-related variables was increased when statistical interactions involving family cohesion and control were included. The variance explained by the friends' drinking-related variables was also greater when interactions with respondents' spending money were included. There was a small positive correlation between socioeconomic status and drinking. The only variables to decrease this relationship when statistically controlled were the drinking-related variables of significant others.  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