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   861992篇
  免费   70561篇
  国内免费   1839篇
耳鼻咽喉   12799篇
儿科学   24623篇
妇产科学   25096篇
基础医学   124199篇
口腔科学   25484篇
临床医学   75302篇
内科学   164526篇
皮肤病学   16974篇
神经病学   70068篇
特种医学   35190篇
外国民族医学   171篇
外科学   136142篇
综合类   24603篇
现状与发展   2篇
一般理论   263篇
预防医学   66864篇
眼科学   20517篇
药学   64708篇
中国医学   1600篇
肿瘤学   45261篇
  2018年   7331篇
  2015年   7722篇
  2014年   11105篇
  2013年   16777篇
  2012年   22712篇
  2011年   23825篇
  2010年   13860篇
  2009年   13058篇
  2008年   22564篇
  2007年   24613篇
  2006年   24488篇
  2005年   24137篇
  2004年   23696篇
  2003年   22828篇
  2002年   21922篇
  2001年   35823篇
  2000年   36464篇
  1999年   30895篇
  1998年   9219篇
  1997年   8545篇
  1996年   8475篇
  1995年   8006篇
  1994年   7724篇
  1992年   26659篇
  1991年   26098篇
  1990年   25617篇
  1989年   24677篇
  1988年   23219篇
  1987年   22883篇
  1986年   21740篇
  1985年   21097篇
  1984年   16385篇
  1983年   13996篇
  1982年   8854篇
  1981年   8201篇
  1980年   7671篇
  1979年   16736篇
  1978年   12114篇
  1977年   10181篇
  1976年   9328篇
  1975年   10147篇
  1974年   12641篇
  1973年   12136篇
  1972年   11538篇
  1971年   10685篇
  1970年   10218篇
  1969年   9909篇
  1968年   8900篇
  1967年   8230篇
  1966年   7653篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
The intraocular pressure and the anteroposterior length of the eye are of great clinical importance for the diagnosis and management, before and after surgery, of congenital glaucoma. It is well-known that normal intraocular pressure in children is different from the normal levels in adults. We performed measurements of intraocular pressure and axial length in 141 children who had been admitted for eye problems other than glaucoma. The intraocular pressures were measured with the Perkins hand-held applanation tonometer at the beginning of general anesthesia. Simultaneously, A-scan ultra-sound measurements of the axial lengths of the eyes were made. In 10 children under the age of two years, the intraocular pressure was 11.85 +/- 1.35 mmHg. In 79 children from two to seven years, the intraocular pressure was 12.80 +/- 1.73 mmHg. In 52 children from seven to 15 years, the intraocular pressure was 13.31 +/- 1.79 mmHg. The axial lengths of the eyes in children under the age of two years, from two to seven years, and from seven to 15 years, were 21.31 +/- 0.97 mm, 22.04 +/- 0.92 mm, and 23.22 +/- 1.00 mm, respectively. These results were considered to be guidelines for measuring intraocular pressure and axial length in children suspected of having congenital glaucoma. The differences of intraocular pressures stated by other authors are due to early measurement of the intraocular pressure at the beginning of general anesthesia.  相似文献   
992.
The visual acuity, the difference in sensitivity of the two eyes to light (brightness ratio), and contrast sensitivity were assessed in 28 patients with chronic open angle glaucoma and compared with those of 41 normal controls of similar ages and visual acuity. The results obtained were related to the results of Tübingen visual field analysis in patients with glaucoma. Twenty-four of the 28 glaucoma patients (86%) had a significant disparity in brightness ratio between the two eyes. This was found to match the frequency of visual field loss. Moreover, there was a significant relationship between the interocular differences in brightness sense and the difference in the degree of visual field loss between the two eyes. Of the glaucoma patients 39% had sum contrast sensitivities outside the normal range for age-matched normal controls. No significant correlation was found between the interocular difference in brightness sense and the visual acuity or the interocular difference in sum contrast sensitivity. It is concluded that, in the presence of a normal visual acuity, the brightness ratio test warrants evaluation as a potential screening test for chronic open angle glaucoma.  相似文献   
993.
Children with pure depression or depression plus an anxiety-related disorder (n = 14) had a higher drug response rate (57%) and a lower placebo response rate (20%) when compared to children with depression plus a concomitant conduct or oppositional disorder (n = 17) (33% drug response rate and 67% placebo response rate). These findings could explain why studies of prepubertal-onset depression found no differences between drug and placebo treatment assuming that a large percentage of the studies' subjects had concomitant conduct or oppositional disorders. The children with pure depression or depression plus an anxiety-related disorder had different symptom clusters from those with depression plus a concomitant conduct or oppositional disorder. The former had more severe CDRS ratings on sleep, appetite disturbance, depressed feelings, and psychomotor retardation. In contrast, those with a concomitant conduct or oppositional disorder had shorter attention spans and were more likely to disturb other children (based on Conners scale scores).  相似文献   
994.
Trospectomycin sulfate is an experimental, aminocyclitol antibiotic. It has been shown in preclinical, chronic safety studies in the dog and rat to elicit a reversible, lysosomal phospholipidosis in liver. The present experiments were conducted to characterize the tissue distribution and disposition of 3H]trospectomycin sulfate in the male rat, perfused rat, perfused rat liver, and cultured rat hepatocytes. Following a 5 mg/kg iv dose to four rats, approximately 70% of the dose was recovered within 24 hr primarily in urine as unchanged drug, and the remainder was eliminated with a terminal phase half-life in blood and tissues of 3 days. Fecal excretion was relatively minor (16% of the dose recovered in feces in 7 days) until later timepoints, when it was the principal pathway of terminal phase elimination. The liver sequestered approximately 10% of the dose and had the highest tissue levels of drug at all times measured. Liver perfusion experiments indicated that trospectomycin accumulated in a hepatic depot compartment as parent drug by a first-order process which was nonsaturable up to a 1 mM concentration of drug. Biliary excretion of unchanged trospectomycin by the perfused liver was slow (approximately 3% of the dose in 2 hr) and occurred by both paracellular and transcellular mechanisms. The hepatic depot compartment appeared to be responsible for transcellular biliary excretion, and thus for the sustained fecal excretion observed in vivo. Subcellular distribution experiments indicated that at least 50% of the drug in the hepatic depot was sequestered in organelles having a broad density range. The existence of a trospectomycin depot compartment was also demonstrated in cultured hepatocytes.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
995.
996.
Immunogold localisation of laminin in normal and exfoliative iris.   总被引:1,自引:1,他引:0       下载免费PDF全文
Immunoelectron microscopic studies of exfoliative iris tissue (seven specimens) revealed the presence of laminin in the fibrillar component of exfoliation material. The immunogold label was uniformly distributed on the exfoliation fibres. Deposition of laminin labelled exfoliation material in the dilator muscle was a noteworthy feature, as was an apparent depletion of laminin in the basement membranes of ostensibly unaffected vessels. In control iris tissue (five enucleated eyes) laminin was identified in the basement membrane round vascular contractile cells, but not beneath the endothelium.  相似文献   
997.
998.
999.
We report on 7 patients (6 M, 1 F) with Coffin-Lowry syndrome who have a sensorineural hearing deficit in addition to developmental delay and characteristic facial changes. One of the patients also had a history of premature exfoliation of primary teeth. These are previously unappreciated clinical signs that may aid in the early diagnosis of Coffin-Lowry syndrome. Early diagnosis and recognition of a hearing deficit in the patient can lead to the use of hearing aids to help the patient achieve his or her full potential. These “;new”; clinical manifestations expand the phenotype of Coffin-Lowry syndrome and constitute an additional indication of pleiotropy. © 1993 Wiley-Liss, Inc.  相似文献   
1000.
The usefulness of surveillance in relating chronic disease trends to recent changes in risk exposures is often questioned on the grounds that these trends respond slowly, reflecting long periods between aetiological exposures and clinical onset of disease. We challenge this preconception on the basis of a review of several important risk factors and diseases: alcohol and liver cirrhosis; tobacco and stroke, cardiovascular disease, and lung cancer; and oestrogens and endometrial cancer. Data from cohort, cross-sectional, and modelling studies demonstrate that the time between removal of exposures and the onset of decline in morbidity or mortality is not defined by the time between initial exposure and disease occurrence. Rather, the pattern of lifetime exposures (with recent exposures often having a dominant effect), the dynamics of the disease process, and the segment of the population with reduced exposures determine how soon the decline begins.  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