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   3637篇
  免费   224篇
  国内免费   23篇
耳鼻咽喉   94篇
儿科学   169篇
妇产科学   44篇
基础医学   465篇
口腔科学   70篇
临床医学   350篇
内科学   643篇
皮肤病学   63篇
神经病学   227篇
特种医学   546篇
外国民族医学   1篇
外科学   359篇
综合类   80篇
一般理论   2篇
预防医学   168篇
眼科学   117篇
药学   248篇
中国医学   7篇
肿瘤学   231篇
  2021年   21篇
  2020年   21篇
  2019年   28篇
  2018年   46篇
  2017年   30篇
  2016年   46篇
  2015年   48篇
  2014年   61篇
  2013年   109篇
  2012年   115篇
  2011年   104篇
  2010年   118篇
  2009年   99篇
  2008年   111篇
  2007年   124篇
  2006年   117篇
  2005年   146篇
  2004年   110篇
  2003年   91篇
  2002年   85篇
  2001年   57篇
  2000年   93篇
  1999年   89篇
  1998年   158篇
  1997年   133篇
  1996年   138篇
  1995年   109篇
  1994年   95篇
  1993年   88篇
  1992年   64篇
  1991年   70篇
  1990年   61篇
  1989年   107篇
  1988年   89篇
  1987年   102篇
  1986年   105篇
  1985年   93篇
  1984年   60篇
  1983年   58篇
  1982年   54篇
  1981年   35篇
  1980年   61篇
  1979年   40篇
  1978年   35篇
  1977年   36篇
  1976年   36篇
  1975年   48篇
  1974年   22篇
  1973年   19篇
  1971年   15篇
排序方式: 共有3884条查询结果,搜索用时 15 毫秒
1.
Neglected tears of the patellar tendon due to loss of active extension remain a difficult therapeutic endeavor. The goals in the approach to this diagnosis include restoration of both structural and functional integrity of the extensor mechanism. A procedure has been developed utilizing Z-shortening of the patellar tendon, Z-lengthening of the quadriceps tendon, and the semitendinosis gracilis as a biologic splint. This technique allows establishment of preoperative goals, including restoration of the muscle-tendon complex in its anatomic position, restoration of quadriceps function, preservation of vascularity of the reconstructed tendon, and splinting of the patellar tendon. This reconstruction allows early mobilization and rehabilitation.  相似文献   
2.
Fifteen patients (16 eyes) with proliferative sickle retinopathy treated with argon or xenon arc feeder vessel photocoagulation had chorioretinal (CRN) or choriovitreal (CVN) neovascularization develop. These patients were followed from 2 1/2 to 11 1/2 years with a mean follow-up of 6 years and 8 months. Clinically important late complications of the choroidal neovascularization included vitreous hemorrhage (in three of eight patients with CVN). However, in only two of these three eyes was there any drop in vision related to residual vitreous hemorrhage, and this was limited to loss of only one line of Snellen visual acuity. Therefore, treatment is not usually recommended if CRN or CVN develops after intense photocoagulation. Vitreous fluorophotometry was performed on these patients to examine the breakdown of the blood-retinal barrier. This gave a quantitative measure of fluorescein leakage not obtained with fluorescein angiography. Midvitreous measurements, which are more representative of these peripherally located proliferative lesions than are pre-retinal measurements, suggest that vitreous fluorophotometry may be helpful in differentiating the higher leakage of CVN from the CRN.  相似文献   
3.
4.
BACKGROUND: Our aims in the present study were to estimate the influences of pain and urinary symptoms on quality of life, and to determine which of these two variables has the most predictive power with respect to quality of life in young men with chronic prostatitis-like symptoms. METHODS: Chronic prostatitis-like symptoms were measured by the National Institutes of Health-Chronic Prostatitis Symptom Index. Of the 28,841 men aged 20 years who lived in the study community, 18,495 men (a response rate 64.1%) agreed to participate in the study. A total of 1057 men who complained of symptoms indicative of chronic prostatitis were included in the study. The influences of pain and urinary symptoms on quality of life were determined using logistic regression analysis. The receiver operating characteristic (ROC) curve was used to estimate the predictive ability of each of these variables with respect to quality of life. RESULTS: Results from multivariate analysis showed that both pain and urinary symptoms were associated with an increased likelihood of impaired quality of life, although pain contributed more to a reduced quality of life than urinary symptoms. Relative to men who experienced mild pain, men who experienced moderate pain had a 3.9-fold risk of poor quality of life (odds ratio [OR], 3.87; 95% confidence interval [CI], 2.86-5.23; P < 0.001) and those who experienced severe pain had a 15.7-fold risk of reduced quality of life (OR, 15.68; 95% CI, 6.59-37.35; P < 0.001). Moderate urinary symptoms were associated with a 1.4-fold risk of bother (OR, 1.41; 95% CI, 1.01-1.99; P < 0.001) and severe urinary symptoms were associated with 2.4-fold risk (OR, 2.39; 95% CI, 1.37-4.12; P < 0.001), relative to mild urinary symptoms. Comparison of the effects of pain and urinary symptoms showed that pain severity had the most predictive power for bother, quality of life, and quality-of-life impact. The areas under the ROC curves for bother, quality of life, and quality-of-life impact were 71.3%, 69.3% and 72.5%, respectively. CONCLUSION: Urinary symptoms and pain might be associated with an increased likelihood of impaired quality of life in young men with chronic prostatitis-like symptoms. In addition, our findings suggest that pain severity is the most influential variable for determining quality of life in this population.  相似文献   
5.
6.
Islet cell carcinomas of the pancreas: a twenty-year experience   总被引:16,自引:0,他引:16  
Unlike its lethal exocrine counterpart, islet cell carcinoma of the pancreas is an indolent neuroendocrine neoplasm. The majority of these tumors are hormonally active. When functioning, a number of clinical syndromes (for example, hyperinsulinism, Zollinger-Ellison and Cushing's syndromes) may be evident. Fifty-eight patients surgically treated between 1965 and 1984 were retrospectively analyzed. The purpose of this study was to determine the distribution of functioning versus nonfunctioning tumors and the response to type of therapy. Mean postoperative follow-up was 7.4 years. Survival and prognostic indices were calculated by the Kaplan-Meier method and compared with log-rank tests. Of the group, 54% had functioning and 46% nonfunctioning tumors. Gastrinomas were the most common functioning tumors encountered (19%). Of interest was the finding that nonfunctioning tumors increased steadily during the last 15 years of the study (25% to 65%). Curative resections were performed in 15 (26%) and noncurative procedures in 43 patients (74%), with an overall operative mortality rate of 3%. Symptomatic improvement was achieved in 90% (curative) and 51% (noncurative). Survival at 3 years was 87% and 66% for the curative and noncurative groups, respectively (p less than 0.1), with an overall 5-year survival of 42%. The absence of hepatic metastases was a major predictor of survival at 3 years (82% vs 56%, p less than 0.05). Survival was statistically better at 3 years in those patients with gastrinomas compared with patients with nonfunctioning tumors (91% vs 58%, p less than 0.05). Although surgical cure is rare, significant long-term palliation may be achieved in a large percentage of patients with an aggressive surgical approach, occasional total gastrectomy, combination chemotherapy, H2 blockade, when indicated, and, most recently, with the new long-acting analogue of somatostatin.  相似文献   
7.
The buffering capacity of tears collected from contact lens wearers was compared to that from non-contact lens wearers. Three groups of subjects were investigated: 6 subjects not wearing contact lenses, 3 subjects wearing rigid contact lenses, and 3 subjects wearing hydrogel contact lenses. Each of the 12 subjects provided, on 6 separate occasions, 100 microliters of tears. The pH of the tears was measured with a closed chamber, temperature stabilized micro-electrode system firstly on collection and then after titration with acid and base. In all, 28 titration steps across the acid-base spectrum were completed for each subject's tears on each occasion. These tear pH responses to acid-base challenge were compared to that of unbuffered distilled water for the same titration procedure. There was no statistically significant effect of contact lens wear on tear buffering capacity, but considerable inter-subject variability was noted.  相似文献   
8.
PURPOSE: The change/no-change procedure (J. E. Sussman & A. E. Carney, 1989), which assesses speech discrimination, has been used under the assumption that the number of stimulus presentations does not influence performance. Motivated by the tenets of the multiple looks hypothesis (N. F. Viemeister & G. H. Wakefield, 1991), work by R. F. Holt and A. E. Carney (2005) called this assumption into question (at least for adults): Nonsense syllable discrimination improved with more stimulus presentations. This study investigates the nature of developmental differences and the effects of multiple stimulus presentations in the change/no-change procedure. METHOD: Thirty normal-hearing children, ages 4.0-5.9 years, were tested on 3 consonant-vowel contrasts at various signal-to-noise ratios using combinations of 2 and 4 standard and comparison stimulus repetitions. RESULTS: Although performance fell below that which is predicted by the multiple looks hypothesis in most conditions, discrimination was enhanced with more stimulus repetitions for 1 speech contrast. The relative influence of standard and comparison stimulus repetitions varied across the speech contrasts in a manner different from that of adults. CONCLUSION: Despite providing no additional sensory information, multiple stimulus repetitions enhanced children's discrimination of 1 set of nonsense syllables. The results have implications for models of developmental speech perception and assessing speech discrimination in children.  相似文献   
9.
10.
The methylxanthine, theobromine (3,7-dimethylxanthine), was tested in mice, to determine whether theobromine could function in vivo as an adenosine receptor antagonist, in keeping with its reported in vitro effects as a blocker of agonist binding to the adenosine A-1 receptor. Theobromine doses, which themselves had no direct effects on spontaneous locomotor activity, completely blocked N6-cyclohexyladenosine-induced suppression of locomotor activity but were without effect on 5'-N-ethylcarboxamide adenosine (NECA)-induced decreases in motor activity. In contrast to the specific antagonism, theobromine blocked the hypothermia induced by both of these adenosine analogs. These results demonstrate that theobromine is an active in vivo adenosine receptor antagonist and that the antagonism of N6-cyclohexyladenosine sensitive systems occurs even though theobromine does not stimulate spontaneous locomotor activity. Thus, the behavioral stimulant effects of methylxanthines may be more related to effects on NECA-sensitive systems, which are not blocked by theobromine. The use of in vivo differences in the effects xanthine may provide a useful tool in the development of compounds to probe the mechanisms of caffeine induced CNS effects.  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