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   127140篇
  免费   7789篇
  国内免费   1592篇
耳鼻咽喉   1697篇
儿科学   3221篇
妇产科学   4253篇
基础医学   19433篇
口腔科学   3737篇
临床医学   10269篇
内科学   22974篇
皮肤病学   2525篇
神经病学   8811篇
特种医学   4200篇
外国民族医学   3篇
外科学   17876篇
综合类   5474篇
一般理论   42篇
预防医学   9692篇
眼科学   2979篇
药学   10893篇
中国医学   819篇
肿瘤学   7623篇
  2021年   1081篇
  2019年   1147篇
  2018年   1726篇
  2017年   1264篇
  2016年   1286篇
  2015年   1557篇
  2014年   2029篇
  2013年   2681篇
  2012年   3896篇
  2011年   4164篇
  2010年   2501篇
  2009年   2235篇
  2008年   3679篇
  2007年   3985篇
  2006年   3949篇
  2005年   3505篇
  2004年   3298篇
  2003年   3051篇
  2002年   2929篇
  2001年   6967篇
  2000年   7195篇
  1999年   5899篇
  1998年   1923篇
  1997年   1444篇
  1996年   1013篇
  1995年   933篇
  1992年   3944篇
  1991年   4022篇
  1990年   3777篇
  1989年   3767篇
  1988年   3644篇
  1987年   3477篇
  1986年   3274篇
  1985年   3108篇
  1984年   2178篇
  1983年   1899篇
  1982年   1068篇
  1979年   2028篇
  1978年   1282篇
  1977年   1073篇
  1976年   1002篇
  1975年   1279篇
  1974年   1481篇
  1973年   1518篇
  1972年   1439篇
  1971年   1324篇
  1970年   1201篇
  1969年   1188篇
  1968年   1081篇
  1967年   948篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
The Synergist Erection System (SES) was tested over a six-month period in 44 impotent patients with an organic etiology. The device was successfully used by 73 percent. The duration of erection for 75 percent of the patients was as long as they wanted to wear the device. The frequency of use was once a week for 47 percent. The quality of erection was rated satisfactory by 63 percent of the patients and 78 percent of the couples rated satisfactory intercourse. It appears the SES option is a valid one with high success and satisfaction rating at least on a short-term basis. In addition, it offers prophylactic protection.  相似文献   
102.
103.
A patient with primary malignant melanoma localized to the right gluteal region is described. Four years later and alter intercurrent influenza, disseminated metastases of malignant melanoma to the skin occurred. After a further 6 months melanodermia developed and lasted until the death of the patient (6 months later). Autopsy revealed melanosis of the visceral organs. Histology taken from internal organs using S-100 protein and HMB-45 melanoma methods confirmed metastases of malignant melanoma to the skin, oral cavity, palatal tonsils, nasal and nasopharyngeal mucosae, lungs, myocardium and brain. The authors discuss the mechanism of melanosis—a rare sign in patients with metastasizing malignant melanoma.  相似文献   
104.
There is a large body of literature describing the causative role of oxidative stress mediated by increased levels of reactive oxygen species in the pathogenesis of cardiovascular disease such as atherosclerosis, hypertension, and restenosis after angioplasty. The positioning of a soft silicone collar around the rabbit carotid artery elicits intimal thickening. The findings from recent studies demonstrated that both intimal thickening and atherosclerosis lead to synthesis of inducible nitric oxide synthase, resulting in abundant amounts of nitric oxide. We investigated the effects of collaring and nicardipine treatment on the activities of antioxidant enzymes, superoxide dismutase and catalase, and total nitrite/nitrate levels, stable products of nitric oxide. Placing the collar increased the total nitrite/ nitrate levels and decreased superoxide dismutase activity in collared arteries. Treatment with nicardipine (20 mg/kg/day, s.c.) prevented enhanced nitric oxide degradation without affecting superoxide dismutase and catalase activities. Our results suggest that enhanced nitric oxide production and superoxide anion are generated in response to the collaring, resulting in oxidative stress within the segment in this model.  相似文献   
105.
The effect of high alveolar surface tension on alveolar epithelial permeability was studied in anesthetized closed-chest mongrel dogs. Alveolar surface tension was elevated by displacement of pulmonary surfactant from the alveolar hypophase by the aerosolized detergent dioctyl sodium sulfosuccinate (OT). After measurement of baseline hemodynamics, arterial blood gases, and airway pressure, the dogs were separated into groups: Group I inhaled a 1% solution of OT (15 mg/kg) in a vehicle of equal parts saline and ethanol; group II inhaled the same volume of vehicle without OT. The pulmonary clearance of technetium 99m diethylenetriamine-pentaacetic acid (99mTc-DTPA) (half-time in minutes) was studied immediately after aerosol (OT and vehicle) delivery and compared with that of historical control values. No change was seen in arterial blood gases and airway pressure after vehicle inhalation, whereas OT caused a marked fall in arterial oxygen tension and increase in airway pressure. Vehicle inhalation effected only a slight increase in DTPA clearance, whereas OT significantly reduced half-time over control and group II. These data suggest that high alveolar surface tension increases alveolar epithelial permeability.  相似文献   
106.
The effects of chemical exposure on the developing nervous system have been documented in both humans and animals for a variety of agents. However, the comparability of these effects has not been carefully evaluated to determine the predictability of animal models to adverse effects in humans. A workshop sponsored by the U.S. Environmental Protection Agency (EPA) and the National Institute on Drug Abuse was held on April 11-13, 1989, to address the Qualitative and Quantitative Comparability of Human and Animal Developmental Neurotoxicity. Invited experts were asked to review the human and animal data on several agents that are known to cause developmental neurotoxicity in humans, including lead, methylmercury, selected abused agents, anticonvulsants, polychlorinated biphenyls (PCBs), ethanol and X-irradiation, and to make quantitative comparisons on a specific end point basis as well as on a functional category basis. In addition, they were asked to make quantitative comparisons when adequate dose-effect data were available. The data also were evaluated in the context of the proposed EPA developmental neurotoxicity testing battery to determine whether or not the battery would adequately detect the effects of each agent. Finally, four work groups were asked to reach consensus on issues relating to: 1) comparability of end points across species for developmental neurotoxicity; 2) testing methods in developmental neurotoxicity for use in human risk assessment; 3) weight-of-evidence and quantitative evaluation of data from developmental neurotoxicity studies; and 4) triggers for developmental neurotoxicity testing.  相似文献   
107.
108.
The hereditary characteristics of enzyme deficiency and dermatoglyphics in congenital color blindness (CCB) were studied. We propose that there is a linkage between the two loci on the X-chromosome determining CCB and glucose-6-phosphate dehydrogenase (G6PD), based on our study of a high incidence of G6PD deficiency in 156 male cases with CCB. The CCB gene is closely linked with that of G6PD deficiency from our pedigree investigations. The rise in the frequency of eight or more whorls, the low value of atd angle and the presenting rate of real palmar patterns of the thenar, hypothenar and I, areas presented the hereditary traits of congenital color blindness.  相似文献   
109.
Translated from Khimiko-farmatsevticheskii Zhurnal, Vol. 26, No. 1, pp. 44–45, January, 1992.  相似文献   
110.
Purified murein from Thiobacillus neapolitanus was poorly digested by lysozyme. It's sensitivity to the enzyme greatly increased after N-acetylation. The murein was found to contain 30 to 35% glucosamine residues lacking N-acetyl groups. It also contained phosphomuramic acid. Further modifications included amidation of diaminopimelic acid in the peptide side chains and a low alanine content. None of these modifications were found in the murein of another sulphur bacterium, Thiobacillus versutus.  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