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   19597篇
  免费   2197篇
  国内免费   114篇
耳鼻咽喉   303篇
儿科学   794篇
妇产科学   523篇
基础医学   2788篇
口腔科学   597篇
临床医学   2462篇
内科学   3857篇
皮肤病学   235篇
神经病学   1115篇
特种医学   898篇
外科学   2712篇
综合类   507篇
一般理论   18篇
预防医学   2038篇
眼科学   410篇
药学   1447篇
中国医学   90篇
肿瘤学   1114篇
  2021年   274篇
  2019年   224篇
  2018年   308篇
  2017年   226篇
  2016年   256篇
  2015年   264篇
  2014年   437篇
  2013年   602篇
  2012年   896篇
  2011年   940篇
  2010年   508篇
  2009年   436篇
  2008年   801篇
  2007年   894篇
  2006年   841篇
  2005年   838篇
  2004年   741篇
  2003年   725篇
  2002年   648篇
  2001年   662篇
  2000年   615篇
  1999年   600篇
  1998年   299篇
  1997年   292篇
  1996年   266篇
  1995年   240篇
  1994年   220篇
  1993年   188篇
  1992年   478篇
  1991年   450篇
  1990年   422篇
  1989年   408篇
  1988年   409篇
  1987年   379篇
  1986年   377篇
  1985年   379篇
  1984年   288篇
  1983年   256篇
  1982年   192篇
  1981年   186篇
  1979年   261篇
  1978年   215篇
  1977年   196篇
  1976年   168篇
  1975年   172篇
  1974年   193篇
  1973年   213篇
  1972年   169篇
  1971年   161篇
  1970年   160篇
排序方式: 共有10000条查询结果,搜索用时 65 毫秒
91.
92.
93.
Because of the recent rapid increase in the number of knee injuries related to racquet sports, the authors undertook a retrospective study of such injuries seen over a 5-year period at the Toronto Western Hospital Sports Medicine Institute. The 121 patients who presented over the study period with a racquet-sports-related knee injury requiring arthroscopy represented 30% of all racquet-sports related injuries seen during that period. The mean age at presentation was 32.8 years and two-thirds of the patients were men. All the major racquet sports were represented. In all, 213 lesions (7 bilateral) were seen at 128 arthroscopies, and 165 arthroscopic procedures were performed. The most common lesion was meniscal followed by chondromalacia patellae, anterior cruciate ligament tears, chondral lesions and pathologic plicae. Over 90% of the patients returned to their chosen racquet sport within 3 months of the arthroscopy and most were playing at a similar performance level to that before the initial injury.  相似文献   
94.
Test properties of the Millon Clinical Multiaxial Inventory (MCMI) were examined in a sample of 419 sex offenders and controls in three different settings. The offender group included sexual aggressives, pedophiles, incest perpetrators and miscellaneous cases. Nineteen of the 20 scales of the MCMI had alpha reliability over 0.60 and for 13 scales it was over 0.80. The scales showed satisfactory discriminant validity from age but 9 scales showed a moderate influence of intelligence scores and education. Criminal history did not influence scale results. The scales unfortunately did show significant correlations with MMPI validity scales. Although the scales were not susceptible to naive lying, they were influenced by social desirability especially. Four factors were extracted in principal axes factor analysis that accounted for 91.2% of the total variance. The first factor explained 58.2% of the variance and was labeled general psychopathology. The other three factors suggested psychotic tendencies, extraversion and the bipolar dependency-antisocial tendencies. When the groups were compared, almost all scales significantly differentiated them. When the MMPI F-K Scale was forced to enter a stepwise discriminant analysis first, five scales still were significant; Narcissistic, Schizoid-Asocial, Alcohol Abuse, Paranoid, & Dependent-Submissive scales. The MCMI taps important dimensions in sex offenders but suffers from validity problems.  相似文献   
95.
BACKGROUND: Interdialytic weight gain (IDWG) can be reduced by lowering the dialysate sodium concentration ([Na]) in haemodialysis patients. It has been assumed that this is because thirst is reduced, although this has been difficult to prove. We compared thirst patterns in stable haemodialysis patients with high and low IDWG using a novel technique and compared the effect of low sodium dialysis (LSD) with normal sodium dialysis (NSD). METHODS: Eight patients with initial high IDWG and seven with low IDWG completed hourly visual analogue ratings of thirst using a modified palmtop computer during the dialysis day and the interdialytic day. The dialysate [Na] was progressively reduced by up to 5 mmol/l over five treatments. Dialysis continued at the lowest attained [Na] for 2 weeks and the measurements were repeated. The dialysate [Na] then returned to baseline and the process was repeated. RESULTS: Baseline interdialytic day mean thirst was higher than the dialysis day mean for the high IDWG group (49.9+/-14.0 vs 36.2+/-16.6) and higher than the low weight gain group (49.9+/-14.0 vs 34.1+/-14.6). This trend persisted on LSD, but there was a pronounced increase in post-dialysis thirst scores for both groups (high IDWG: 46+/-13 vs 30+/-21; low IDWG: 48+/-24 vs 33+/-18). The high IDWG group demonstrated lower IDWG during LSD than NSD (2.23+/-0.98 vs 2.86+/-0.38 kg; P<0.05). CONCLUSIONS: Our results indicate that patients with high IDWG experience more intense feelings of thirst on the interdialytic day. LSD reduces their IDWG, but paradoxically increases thirst in the immediate post-dialysis period.  相似文献   
96.
97.
98.
This study piloted a brief individual motivational intervention targeting multiple health risk behaviors in HIV-positive youth aged 16-25. Interviews about sexual behavior and substance use and viral load testing were obtained from 51 HIV-positive youth at baseline and post intervention. Youth were randomized to receive a four-session motivational enhancement intervention (N = 25) or to a wait-list control (N = 26). Of the eligible youth approached, 88% agreed to participate, and 80% percent of participants completed at least three of four sessions. The treatment group showed significantly greater reductions in unprotected sex acts and in viral load compared with controls. Although change scores for substance use were not significantly different between the two groups, paired t tests demonstrated that reductions in alcohol use and marijuana use were significant for the treatment group at the trend level. There were no significant differences in substance use from baseline to posttest for the control group. Findings demonstrate the potential of a brief motivational enhancement intervention to improve health risk behaviors in HIV-positive youth. Larger randomized clinical trials are warranted. Resources required for retention should not be underestimated.  相似文献   
99.
MRI evaluations of intramyocardial hemorrhage in acute infarction have relied on T(2) and T(2)(*) shortening only. We propose a more comprehensive evaluation of hemorrhagic infarction based on the concept that fluctuations in T(2) and T(1) relaxation in acute reperfused infarction will reflect transient edema and hemoglobin oxidative denaturation to uncompartmentalized methemoglobin. Anteroapical infarction was created via percutaneous balloon in young swine (22-25 kg, N = 12). T(2), T(1), diastolic wall thickness (DWT), and the Gd-DTPA partition coefficient (lambda) were measured on days 0, 2, and 7. DWT was elevated at 1 hr postreperfusion (128% +/- 53%, P = 0.0001), and alleviated on days 2 and 7 (48% +/- 10%, P = 0.008; 53% +/- 24%, P = 0.003). T(2) and T(1) elevations were coincident with early edema (DeltaT(2) = 55% +/- 24%, P < 0.0001; DeltaT(1) = 27% +/- 18%, P < 0.04). T(2) and T(1) were nearly normal on day 2 (DeltaT(2) = 8% +/- 8%, P = 0.27; DeltaT(1) = 0% +/- 1%, P = 0.65). On day 7, T(2) increased while T(1) decreased (DeltaT(2) = 27% +/- 16%, P = 0.005; DeltaT(1) = -14% +/- 10%, P = 0.02). Lambda was elevated by >150% at all time points (P < or = 0.002). Histology verified hemorrhagic injury. T(1) and T(2) fluctuations are consistent with transient edema, as well as hemoglobin oxidative denaturation to decompartmentalized methemoglobin. This methodological development may broaden our understanding of hemorrhagic microvascular injury and improve its detection in clinical populations.  相似文献   
100.
Multiple molecular forms of cyclic nucleotide phosphodiesterase have been characterized in various tissues and cells according to their substrate specificity, intracellular location, and calmodulin dependence. The purpose of this study was to evaluate the possible involvement of different molecular forms of phosphodiesterase in regulating the respiratory burst and lysosomal enzyme release responses of human neutrophils. Treatment with the selective cyclic AMP-specific, cyclic GMP-insensitive phosphodiesterase inhibitors Ro 20-1724 or rolipram, or the nonselective phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX), resulted in inhibition of respiratory burst stimulated by the chemoattractants formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP) (IC50 values: 0.71-17 microM) and complement fragment C5a (IC50 values: 61-93 microM), but did not inhibit phagocytosis-stimulated respiratory burst (less than 10% inhibition at 100 microM). Selective inhibitors of calmodulin-dependent phosphodiesterase (ICI 74,917), calmodulin-insensitive, cyclic GMP-specific phosphodiesterase (M & B 22,948), cyclic GMP-stimulated phosphodiesterase (AR-L 57), or cyclic AMP-specific, cyclic GMP-inhibited phosphodiesterase (amrinone and cilostamide) exhibited little or no inhibitory effect on FMLP- or phagocytosis-stimulated respiratory burst (0-42% inhibition at 100 microM). Regulation of neutrophil activation by phosphodiesterase was also response specific, as Ro 20-1724, rolipram and IBMX were less potent inhibitors of FMLP-induced lysosomal enzyme release (0-14% inhibition at 100 microM). Analysis of human neutrophil preparations confirmed the existence of a cyclic AMP-specific, cyclic GMP-insensitive phosphodiesterase, which was associated with the particulate fraction of the cell. These results demonstrate a role for the cyclic AMP-specific, cyclic GMP-insensitive phosphodiesterase in the regulation of human neutrophil functions, which appears to be both stimulus specific and response specific.  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