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   16299篇
  免费   938篇
  国内免费   75篇
耳鼻咽喉   118篇
儿科学   408篇
妇产科学   402篇
基础医学   2280篇
口腔科学   286篇
临床医学   1587篇
内科学   3711篇
皮肤病学   454篇
神经病学   1395篇
特种医学   279篇
外科学   1585篇
综合类   80篇
一般理论   11篇
预防医学   1740篇
眼科学   396篇
药学   1147篇
中国医学   73篇
肿瘤学   1360篇
  2024年   13篇
  2023年   128篇
  2022年   104篇
  2021年   563篇
  2020年   308篇
  2019年   507篇
  2018年   547篇
  2017年   360篇
  2016年   361篇
  2015年   481篇
  2014年   674篇
  2013年   903篇
  2012年   1359篇
  2011年   1504篇
  2010年   807篇
  2009年   628篇
  2008年   1144篇
  2007年   1150篇
  2006年   1073篇
  2005年   1051篇
  2004年   911篇
  2003年   841篇
  2002年   781篇
  2001年   101篇
  2000年   65篇
  1999年   90篇
  1998年   131篇
  1997年   108篇
  1996年   70篇
  1995年   79篇
  1994年   67篇
  1993年   47篇
  1992年   38篇
  1991年   36篇
  1990年   26篇
  1989年   27篇
  1988年   27篇
  1987年   17篇
  1986年   18篇
  1985年   18篇
  1984年   18篇
  1983年   18篇
  1982年   14篇
  1981年   15篇
  1980年   15篇
  1979年   9篇
  1978年   8篇
  1977年   8篇
  1976年   7篇
  1974年   6篇
排序方式: 共有10000条查询结果,搜索用时 718 毫秒
991.
Background Situs inversus (SI) is a rare autosomal recessive congenital defect in which the position of abdominal and/or thoracic organs is a mirror image of the normal one, in the sagittal plain. In 25% of these cases, SI is part of the Kartagener syndrome, together with bronchiectasis and chronic sinusitis.Methods We present a case of a patient with Kartagener syndrome and complete SI that was laparoscopically operated on for diverticulitis. We also review the published English information available on this rare condition.Results A review of the literature revealed another single case of laparoscopic sigmoidectomy and 27 cases of other laparoscopic interventions in the presence of SI. Those laparoscopic procedures included basic procedures such as explorations and cholecystectomies, as well as advanced procedures such as gastrectomy and gastric bypass.Conclusion The laparoscopic approach is feasible in cases of SI, although technically more complicated because of the different position of the organs and the different laparoscopic view of the anatomy.  相似文献   
992.
Androgens and estrogens are critical factors for bone homeostasis; hence, polymorphisms of genes involved in the metabolism and activity of sex steroids are likely candidates to influence bone mass. Therefore, we studied the association of two of those microsatellite polymorphisms, situated in intron 4 of CYP19-aromatase and exon 1 of androgen receptor, with bone mass in a group of 324 healthy men of a wide age range (mean age 49, range 22-75). CYP19 and androgen receptor alleles were typed by capillary electrophoresis after PCR amplification. Bone mass was measured by dual X-ray absorptiometry at the hip and the spine. No association was found between androgen receptor variation and bone mass. However, among the 184 subjects aged more than 45 years, a significant association was found between CYP19 alleles and bone mass at the lumbar spine (P = 0.001) and total hip (P = 0.01). Individuals with long alleles had higher bone mass, even after adjusting for body weight, height, or calcium intake. Mean spine Z scores were -0.1 (95% CI, -0.3 to 0.2), -0.1 (-0.4 to 0.2), and 0.6 (0.3 to 0.9) for individuals with short, intermediate, and long alleles, respectively. Total hip Z scores were 0.4 (0.2 to 0.6), 0.4 (0.2 to 0.6), and 0.8 (0.5 to 1.0), respectively. Longer CYP19 alleles were also associated with higher free estradiol index. These results suggest that common variations in CYP19-aromatase gene may have an important influence on the maintenance of male skeleton after peak bone mass is reached.  相似文献   
993.
994.
Context  The metabolic syndrome has been identified as a target for dietary therapies to reduce risk of cardiovascular disease; however, the role of diet in the etiology of the metabolic syndrome is poorly understood. Objective  To assess the effect of a Mediterranean-style diet on endothelial function and vascular inflammatory markers in patients with the metabolic syndrome. Design, Setting, and Patients  Randomized, single-blind trial conducted from June 2001 to January 2004 at a university hospital in Italy among 180 patients (99 men and 81 women) with the metabolic syndrome, as defined by the Adult Treatment Panel III. Interventions  Patients in the intervention group (n = 90) were instructed to follow a Mediterranean-style diet and received detailed advice about how to increase daily consumption of whole grains, fruits, vegetables, nuts, and olive oil; patients in the control group (n = 90) followed a prudent diet (carbohydrates, 50%-60%; proteins, 15%-20%; total fat, <30%). Main Outcome Measures  Nutrient intake; endothelial function score as a measure of blood pressure and platelet aggregation response to L-arginine; lipid and glucose parameters; insulin sensitivity; and circulating levels of high-sensitivity C-reactive protein (hs-CRP) and interleukins 6 (IL-6), 7 (IL-7), and 18 (IL-18). Results  After 2 years, patients following the Mediterranean-style diet consumed more foods rich in monounsaturated fat, polyunsaturated fat, and fiber and had a lower ratio of omega-6 to omega-3 fatty acids. Total fruit, vegetable, and nuts intake (274 g/d), whole grain intake (103 g/d), and olive oil consumption (8 g/d) were also significantly higher in the intervention group (P<.001). The level of physical activity increased in both groups by approximately 60%, without difference between groups (P = .22). Mean (SD) body weight decreased more in patients in the intervention group (–4.0 [1.1] kg) than in those in the control group (–1.2 [0.6] kg) (P<.001). Compared with patients consuming the control diet, patients consuming the intervention diet had significantly reduced serum concentrations of hs-CRP (P = .01), IL-6 (P = .04), IL-7 (P = 0.4), and IL-18 (P = 0.3), as well as decreased insulin resistance (P<.001). Endothelial function score improved in the intervention group (mean [SD] change, +1.9 [0.6]; P<.001) but remained stable in the control group (+0.2 [0.2]; P = .33). At 2 years of follow-up, 40 patients in the intervention group still had features of the metabolic syndrome, compared with 78 patients in the control group (P<.001). Conclusion  A Mediterranean-style diet might be effective in reducing the prevalence of the metabolic syndrome and its associated cardiovascular risk.   相似文献   
995.
Summary.Background: Evidence from in vitro studies suggests that antioxidant olive oil phenolic compounds can prevent LDL oxidation. However, in vivo evidence in support of this hypothesis is sparse.Aim of the study: to establish the antioxidant effect of olive oils with differences in their phenolic compounds content in humansMethods: A controlled, double blind, cross-over, randomized, clinical trial using three similar olive oils with increasing phenolic concentration (from 0 to 150 mg/Kg) was conducted in 30 healthy volunteers. Olive oils were administered over three periods of 3 weeks preceded by two-week washout periods.Results: Urinary tyrosol and hydroxytyrosol increased (p < 0.020), in vivo plasma oxidized LDL decreased (p = 0.006), and ex vivo resistance of LDL to oxidation increased (p = 0.012) with the phenolic content of the olive oil administered. After virgin olive oil administration, an increase (p = 0.029) was observed in HDL cholesterol levels.Conclusions: Sustained consumption of virgin olive oil with the high phenolic content was more effective in protecting LDL from oxidation and in rising HDL cholesterol levels than that of other type of olive oils. Dose-dependent changes in oxidative stress markers, and phenolic compounds in urine, were observed with the phenolic content of the olive oil administered. Our results support the hypothesis that virgin olive oil consumption could provide benefits in the prevention of oxidative processes.* Participants of the SOLOS-Investigation are listed in the Appendix.  相似文献   
996.
997.
The aim of the present study was to evaluate whether olive oils high in phenolic compounds influence the oxidative/antioxidative status in humans. Healthy men (n = 12) participated in a double-blind, randomized, crossover study in which 3 olive oils with low (LPC), moderate (MPC), and high (HPC) phenolic content were given as raw doses (25 mL/d) for 4 consecutive days preceded by 10-d washout periods. Volunteers followed a strict very low-antioxidant diet the 3 d before and during the intervention periods. Short-term consumption of olive oils decreased plasma oxidized LDL (oxLDL), 8-oxo-dG in mitochondrial DNA and urine, malondialdehyde in urine (P < 0.05 for linear trend), and increased HDL cholesterol and glutathione peroxidase activity (P < 0.05 for linear trend), in a dose-dependent manner with the phenolic content of the olive oil administered. At d 4, oxLDL after MPC and HPC, and 8-oxo-dG after HPC administration (25 mL, respectively), were reduced when the men were in the postprandial state (P < 0.05). Phenolic compounds in plasma increased dose dependently during this stage with the phenolic content of the olive oils at 1, 2, 4, and 6 h, respectively (P < 0.01). Their concentrations increased in plasma and urine samples in a dose-dependent manner after short-term consumption of the olive oils (P < 0.01). In conclusion, the olive oil phenolic content modulated the oxidative/antioxidative status of healthy men who consumed a very low-antioxidant diet.  相似文献   
998.
999.
1000.
Dust-cloud episodes were detected in summer 1999 in the city of Cordoba, southwestern Spain, with a higher frequency than usual. Solid airborne particles were collected using a suction volumetric sampler and analyzed to determine both their nature and their origin. Nonbiological material was mostly identified as mineral sand and partially burned remains of hydrocarbons and stubble. Amounts were estimated in terms of the percentage of microscopic field of view covered. Biological materials, in this case pollen grains, were identified and classified as belonging to either autochthonous or remote flora; in the latter case, the possibility was examined that they might originate in North Africa. Some pollen types were also used as tracers to chart the path followed by the sand clouds within the Iberian Peninsula. Meteorological conditions on the days in which episodes occurred were analyzed. In all cases, very dry southwesterly winds were recorded, at moderate to high speeds, together with temperatures of over 35°C. The increase in airborne pollen detected, together with the large amount of particles collected, could have an adverse effect on health, particularly in pollen allergy sufferers, for whom dust-clouds represent an added risk.  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