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   2215324篇
  免费   154556篇
  国内免费   4568篇
耳鼻咽喉   31816篇
儿科学   72051篇
妇产科学   63247篇
基础医学   319871篇
口腔科学   61907篇
临床医学   187088篇
内科学   440005篇
皮肤病学   48219篇
神经病学   176943篇
特种医学   84941篇
外国民族医学   764篇
外科学   336350篇
综合类   43377篇
现状与发展   1篇
一般理论   603篇
预防医学   169443篇
眼科学   50736篇
药学   164964篇
  1篇
中国医学   4638篇
肿瘤学   117483篇
  2019年   17846篇
  2018年   28063篇
  2017年   20430篇
  2016年   21422篇
  2015年   24215篇
  2014年   32511篇
  2013年   49936篇
  2012年   70805篇
  2011年   74820篇
  2010年   43245篇
  2009年   39409篇
  2008年   69936篇
  2007年   74918篇
  2006年   74755篇
  2005年   73380篇
  2004年   70004篇
  2003年   67282篇
  2002年   65741篇
  2001年   92944篇
  2000年   95562篇
  1999年   81609篇
  1998年   23038篇
  1997年   20632篇
  1996年   20688篇
  1995年   19387篇
  1994年   18409篇
  1993年   17183篇
  1992年   64363篇
  1991年   62695篇
  1990年   61669篇
  1989年   59556篇
  1988年   55593篇
  1987年   54427篇
  1986年   52077篇
  1985年   49706篇
  1984年   37199篇
  1983年   32057篇
  1982年   19286篇
  1979年   35201篇
  1978年   24733篇
  1977年   21227篇
  1976年   20068篇
  1975年   22125篇
  1974年   26225篇
  1973年   25309篇
  1972年   23984篇
  1971年   22365篇
  1970年   21106篇
  1969年   20044篇
  1968年   19004篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The chemical composition of the seeds of the low-alkaloid variety “Inti” of the Andean lupin (Lupinus mutabilis) grown in the south of Chile was examined. The contents of (% of dry weight) total alkaloids, protein, lipids, and oligosaccharides were found to be 0.0075, 51.0, 16.0, and 14.7%, respectively. The low levels of the sulfur amino acids (2.38% of total protein) made them the first amino acids to limit the protein quality of these lupin seeds. The fatty acid pattern was C16:0,13.9%; C18:0, 3.0%; C18:1, 41.8%; C18:2, 38.9%; and C18:3,2.6% of total fatty acids. The α-galactoside amounted to 13.5% of dry weight (raffinose, 2.49%; stachyose, 10.1%, verbascose, 0.85%). It can be stated that “Inti” is highly interesting as a potential protein energy crop for a temperate climate.  相似文献   
992.
993.
994.
Since its introduction in early 1985, the Volk +90D lens has become a very popular auxiliary lens for biomicroscopic fundus evaluation. The Volk +90D lens provides a wide field of view which is accessible by simple scanning of the biomicroscope. The necessity to hand hold the lens, however, has not always provided enough stability, particularly for the novice user. This article describes a newly introduced holder for the Volk +90D lens which mounts on the base of the biomicroscope headrest providing rapid and stable lens placement. Use of this holder improves the technique of retinal examination and photography by stabilizing the image and by freeing both hands to operate the slit lamp biomicroscope. The enhanced stability afforded by this holder also gives the examiner the practical capability of viewing the posterior pole without mydriasis.  相似文献   
995.
We report a prevalence study of the best visual acuity in the affected eye of 100 selected patients with herpetic keratitis seen during a two-year period. Sixty-two patients retained an acuity of 6/9 or better without requiring penetrating keratoplasty (PK). The prevalence of reduced visual acuity severe enough to warrant PK was 33%. Patients requiring PK for whom full clinical records were available suffered a mean of 6.8 episodes of keratitis. In this group of patients the vision of 18 fell from 6/6 to 6/60 over a mean period of 8.5 years. Once visual acuity was permanently reduced to 6/12, 78% of patients proceeded to lose vision to 6/60. Unilateral visual impairment occurs in at least a third of patients with severe herpetic keratitis. Once vision falls permanently to 6/12, the long-term prognosis for vision appears to be poor.  相似文献   
996.
The onset of diabetic nephropathy is characterized by subclinical elevation of urinary albumin excretion, so-called 'microalbuminuria' (M). Dietary assessments were carried out in 15 insulin-dependent diabetic patients with persistent M and an equal number with persistently normal albumin excretion. The groups were matched for sex, age, duration of diabetes, body mass index, insulin dose and glycosylated haemoglobin; there were no significant differences in systemic blood pressure, glomerular filtration rate, blood glucose and serum albumin concentrations between the groups; retinopathy was significantly more frequent in patients with M. Diabetics with persistent M were found to consume a significantly larger amount of fat (expressed as grams and percentage of total energy) and a significantly smaller percentage of total energy as carbohydrate than patients with normal albumin excretion; total dietary energy was larger in those with persistent M, but the difference was not significant. No significant differences were found in protein and fibre intakes between the groups. Our findings suggest that an excess in the dietary consumption of fat relative to carbohydrate might play an important role in the pathogenesis of early nephropathy in insulin-dependent diabetes mellitus. We emphasize the importance of careful attention to nutrient intake in the prevention and treatment of diabetic complications.  相似文献   
997.
998.
Tear mucus crystallization in children with cystic fibrosis   总被引:1,自引:0,他引:1  
Cystic fibrosis is characterized by an abnormally high electrolyte concentration in exocrine secretions. The authors performed the tear mucus ferning test in 26 eyes of children with cystic fibrosis and compared the results to those in an equal number of age-matched normals. The results suggest that the increased electrolyte concentration could be responsible for the increased hyperviscosity of mucus. The tear mucus ferning test appears to be a suitable diagnostic test for the assessment of cystic fibrosis.  相似文献   
999.
1000.
Penetrating keratoplasty was performed in 106 cases of post-inflammatory corneal opacity with vascularization. Donor material obtained post mortem was preserved in a moist chamber, MK-medium at 4 degrees C or in culture medium at room temperature. 55.7% of patients gained a useful vision after keratoplasty. The post-operative spherical error of refraction was found to be -1.4 +/- 3.6 D and the astigmatic error of refraction -3.3 +/- 2.0 D. The post-operative visual acuity was found to be 0.2 +/- 0.2. The ocular pathology associated with keratoplasty is discussed.  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