全文获取类型
收费全文 | 34096篇 |
免费 | 2553篇 |
国内免费 | 125篇 |
专业分类
耳鼻咽喉 | 430篇 |
儿科学 | 961篇 |
妇产科学 | 667篇 |
基础医学 | 4339篇 |
口腔科学 | 562篇 |
临床医学 | 3294篇 |
内科学 | 7683篇 |
皮肤病学 | 628篇 |
神经病学 | 3212篇 |
特种医学 | 1414篇 |
外科学 | 5632篇 |
综合类 | 340篇 |
现状与发展 | 1篇 |
一般理论 | 52篇 |
预防医学 | 2524篇 |
眼科学 | 471篇 |
药学 | 1801篇 |
中国医学 | 46篇 |
肿瘤学 | 2717篇 |
出版年
2023年 | 364篇 |
2022年 | 632篇 |
2021年 | 1451篇 |
2020年 | 761篇 |
2019年 | 1093篇 |
2018年 | 1346篇 |
2017年 | 956篇 |
2016年 | 928篇 |
2015年 | 1104篇 |
2014年 | 1528篇 |
2013年 | 1873篇 |
2012年 | 2728篇 |
2011年 | 2682篇 |
2010年 | 1487篇 |
2009年 | 1187篇 |
2008年 | 1809篇 |
2007年 | 1909篇 |
2006年 | 1667篇 |
2005年 | 1542篇 |
2004年 | 1329篇 |
2003年 | 1133篇 |
2002年 | 1031篇 |
2001年 | 375篇 |
2000年 | 334篇 |
1999年 | 368篇 |
1998年 | 259篇 |
1997年 | 216篇 |
1996年 | 216篇 |
1995年 | 166篇 |
1994年 | 153篇 |
1993年 | 134篇 |
1992年 | 255篇 |
1991年 | 252篇 |
1990年 | 245篇 |
1989年 | 235篇 |
1988年 | 215篇 |
1987年 | 208篇 |
1986年 | 210篇 |
1985年 | 228篇 |
1984年 | 198篇 |
1983年 | 155篇 |
1982年 | 150篇 |
1981年 | 120篇 |
1980年 | 103篇 |
1979年 | 139篇 |
1978年 | 117篇 |
1977年 | 76篇 |
1976年 | 79篇 |
1975年 | 79篇 |
1974年 | 74篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
Benjamin H. S. Lau Sharon K. Riesen Kim P. Truong Esther W. Lau Peter Rohdewald Ray A. Barreta 《The Journal of asthma》2004,41(8):825-832
A randomized, placebo-controlled, double-blind study involving 60 subjects, aged 6-18 years old, was conducted over a period of 3 months to determine the effect of Pycnogenol® (a proprietary mixture of water-soluble bioflavonoids extracted from French maritime pine) on mild-to-moderate asthma. After baseline evaluation, subjects were randomized into two groups to receive either Pycnogenol® or placebo. Subjects were instructed to record their peak expiratory flow with an Assess® Peak Flow Meter each evening. At the same time, symptoms, daily use of rescue inhalers (albuterol), and any changes in oral medications were also recorded. Urine samples were obtained from the subjects at the end of the run-in period, and at 1-, 2-, and 3-month visits. Urinary leukotriene C4/D4/E4 was measured by an enzyme immunoassay. Compared with subjects taking placebo, the group who took Pycnogenol® had significantly more improvement in pulmonary functions and asthma symptoms. The Pycnogenol® group was able to reduce or discontinue their use of rescue inhalers more often than the placebo group. There was also a significant reduction of urinary leukotrienes in the Pycnogenol® group. The results of this study demonstrate the efficacy of Pycnogenol® as an adjunct in the management of mild-to-moderate childhood asthma. 相似文献
13.
14.
Henri Gastaut Benjamin Zifkin Marcel Rufo 《Journal of autism and developmental disorders》1987,17(3):391-406
Syncopes due to compulsive respiratory stereotypies were studied in eight patients with autistic features. Most had been referred for episodes thought to be intractable epileptic seizures. Polygraphic recording showed two types of syncope, one induced by prolonged apnea and the other by a prolonged Valsalva maneuver. Fenfluramine, 1.5–3 mg/kg per day, was given in an open trial. In four of five cases with frequent Valsalva maneuvers, respiratory stereotypies and syncopes were suppressed for 2–18 months. Patients with periodic apneas were more severely retarded and had less clear benefit. Side effects consisted of dose-dependent sedation and mild weight loss which stabilized without interrupting treatment. We suggest that these syncopes are volitional and may be associated with pleasant sensations. A double-blind placebo-controlled trial of fenfluramine seems warranted in such patients. 相似文献
15.
F Parazzi B Faravelli L Gallo M Nosenzo A Razzetti D Barone R Bandelloni E D'Amore 《Tumori》1987,73(1):33-36
The usefulness of tumor marker assay in pleural effusions for differential diagnosis is still debated. From the observation of common antigens on tissue polypeptide antigen (TPA) and keratins 8, 18 and 19 and vimentin, all substances contained in normal and neoplastic mesothelium, we felt it opportune to evaluate the use of TPA assay in 105 pleural effusions (46 benign and 59 malignant). The values were much higher than those found in blood. In hydrothorax the median value was 454 U/l (range, 59-1923), in exudative effusions 846 U/l (range, 258-4485), in metastatic pleural effusions 1277 U/l (range, 58-32352) and in mesotheliomas 7705 (range, 759-16000). The maximum value found in nonmalignant effusions was 4485 U/l; this value was taken as a cutoff level, so only 29.9% of the tumors were positive to the test. Our results showed this assay to be not very important for a differential diagnosis of malignant and nonmalignant pleural effusions. Nevertheless, the different TPA patterns in mesotheliomas (66.6% positive) and metastatic pleural effusions (15.9%) suggest that further studies are warranted. 相似文献
16.
5H-Mebendazole and some related heterocyclic methyl carbamates were synthesized and their anthelmintic activity against Caenorhabditis elegans was determined. In order to study the influence of the heteroaromatic region with regard to the carbamate moiety on biological activity, the molecular electrostatic potentials (MEP) of all structures were calculated and a structure-activity relationship (SAR) was established. The electrostatic pattern of activity includes two minima of the carbamate moiety, a third heterocyclic minimum, and a pi-electronic region. 相似文献
17.
Michelle K Nurzenski N Kathryn Briffa Roger I Price Benjamin C C Khoo Amanda Devine Thomas J Beck Richard L Prince 《Journal of bone and mineral research》2007,22(3):416-424
A population-based study on 1008 postmenopausal women identified that the 24% of women achieving high levels of PA and CI had 3.4-4.4% higher femoral bone strength in axial compression and 1.7-5.2% in bending than those achieving low levels, indicating that lifestyle factors influence bone strength in the proximal femur. INTRODUCTION: Extensive research has shown that increased physical activity (PA) and calcium intake (CI) decrease the rate of bone loss; however, there is little research on how these lifestyle variables affect bone geometry. This study was designed to investigate the effects of modifiable lifestyle variables, habitual PA and dietary CI, on femoral geometry in older women. MATERIALS AND METHODS: Femoral geometry, habitual PA, and dietary CI were measured in a population-based sample of 1008 women (median age+/-interquartile range, 75+/-4years) enrolled in a randomized controlled trial (RCT) of calcium supplementation. Baseline PA and CI were assessed by validated questionnaires, and 1-year DXA scans (Hologic 4500A) were analyzed using the hip structural analysis technique. Section modulus (Z), an index of bending strength, cross-sectional area (CSA), an index of axial compression strength, subperiosteal width (SPW), and centroid position, the position of the center of mass, were measured at the femoral neck (NN), intertrochanter (IT), and femoral shaft (FS) sites. These data were divided into tertiles of PA and CI, and the results were compared using analysis of covariance (ANCOVA), with corrections for age, height, weight, and treatment (calcium/placebo). RESULTS AND CONCLUSIONS: PA showed a significant dose-response effect on CSA all hip sites (p<0.03) and Z at the narrow neck and intertrochanter sites (p<0.02). For CI, there was a dose-response effect for centroid position at the intertrochanter (p=0.03). These effects were additive, such that the women (n=240) with PA in excess of 65.5 kcal/day and CI in excess of 1039 mg/day had significantly greater CSA (NN, 4.4%; IT, 4.3%; FS, 3.4%) and Z (NN, 3.9%; IT, 5.2%). These data show a favorable association between PA and aspects of bone structural geometry consistent with better bone strength. Association between CI and bone structure was only evident in 1 of 15 variables tested. However, there was evidence that there may be additive effects, whereby women with high levels of PA and CI in excess of 1039 mg/day had significantly greater CSA (NN, 0.4%; FS, 2.1%) and Z (IT, 3.0%) than women with high PA but low CI. These data show that current public health guidelines for PA and dietary CI are not inappropriate where bone structure is the health component of interest. 相似文献
18.
Ofer Gemer Benjamin Piura Shmuel Segal Ilana Yanai Inbar 《International journal of gynecological pathology》2003,22(4):398-400
Chondroid syringoma of the vulva is an extremely rare tumor. Of the previously reported cases, only one was clinically malignant. The authors describe a case of chondroid syringoma of the right labium majus from which arose a papillary adenocarcinoma. A right inguinal lymph node was replaced with metastatic adenocarcinoma. 相似文献
19.
Children with no known prior vitamin A deficiency exhibited a significant decline in their serum retinol levels during the acute phase of measles. This decline in circulating retinol was associated with increased duration of fever, higher hospitalization rates, and decreased antibody titers. 相似文献
20.
Perceptions of Parenting and Depression-Proneness in the Offspring: Dysfunctional Attitudes as a Mediating Mechanism 总被引:2,自引:0,他引:2
This research attempted to clarifythe mechanismthrough which dysfunctional parenting leads todepression in the offspring. Consistent with theorizingbyBeck (1967), we tested a three-stage causal pathway wherein dysfunctional parenting should giverise to dysfunctional attitudes in the offspring which,in turn, should give rise to depression-proneness in theoffspring. Another objective of this study was to further delineate the types of parentingbehaviors that give rise to dysfunctional attitudes inthe offspring. To this end, a large sample of collegestudents (N = 246) completed measures assessing four parenting dimensions (i.e., low care,overprotection, perfectionistic expectations, andcriticalness) as well as measures assessingdysfunctional attitudes, general depression-proneness,and current depression. Support for the depressogenic effects of allfour parenting dimensions was obtained in that eachparenting dimension correlated significantly withdysfunctional attitudes and depression tendencies in the offspring. Moreover, path analyses supportedBeck's three-stage causal model with perfectionistic andcritical parenting playing a particularly prominentrole. Last, after controlling for current depression, the partial correlations among the variables inthe three-stage model remained significant, suggestingthat the present findings were not simply the result ofa mood congruency effect. These findings illuminate additional parenting behaviors that can havedepressogenic effects and indicate that these parentingbehaviors exert their effects, at least in part, by wayof instilling dysfunctional attitudes in the offspring. 相似文献