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   210063篇
  免费   15577篇
  国内免费   744篇
耳鼻咽喉   2284篇
儿科学   5482篇
妇产科学   4307篇
基础医学   27121篇
口腔科学   4510篇
临床医学   20009篇
内科学   44898篇
皮肤病学   2755篇
神经病学   20307篇
特种医学   6955篇
外国民族医学   13篇
外科学   32993篇
综合类   3416篇
现状与发展   2篇
一般理论   292篇
预防医学   19074篇
眼科学   4374篇
药学   14392篇
  1篇
中国医学   374篇
肿瘤学   12825篇
  2023年   843篇
  2022年   1404篇
  2021年   3442篇
  2020年   2105篇
  2019年   3391篇
  2018年   3968篇
  2017年   3214篇
  2016年   3413篇
  2015年   4069篇
  2014年   6097篇
  2013年   8822篇
  2012年   13127篇
  2011年   14324篇
  2010年   8100篇
  2009年   7304篇
  2008年   13592篇
  2007年   14430篇
  2006年   13920篇
  2005年   14395篇
  2004年   13808篇
  2003年   12903篇
  2002年   12438篇
  2001年   1880篇
  2000年   1466篇
  1999年   2053篇
  1998年   2835篇
  1997年   2439篇
  1996年   2212篇
  1995年   1954篇
  1994年   1757篇
  1993年   1657篇
  1992年   1216篇
  1991年   1151篇
  1990年   1062篇
  1989年   958篇
  1988年   1018篇
  1987年   1019篇
  1986年   1000篇
  1985年   1087篇
  1984年   1480篇
  1983年   1463篇
  1982年   1814篇
  1981年   1641篇
  1980年   1555篇
  1979年   813篇
  1978年   958篇
  1977年   932篇
  1976年   831篇
  1975年   684篇
  1974年   671篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
A bstract One etiology of unilateral lobar pulmonary edema is mitral regurgitation. Echocardiography is able to demonstrate the retrograde flow of blood into the pulmonary veins and allows timely diagnosis and treatment planning. Correction of mitral regurgitation is followed by resolution of the radiographic abnormality.  相似文献   
992.
The age-dependence of the incidence of magnocellular neurosecretory neurons containing abnormal accumulations of peptide in the rough endoplasmic reticulum was examined in homozygous Brattleboro rats and in their wild-type Long Evans counterparts. Neurons in which the immunophenotype of the peptide aggregates indicate that somatic cross-over mutations involving the 5' end of the vasopressin gene and the 3' end of the oxytocin gene have occurred, increased with age in homozygous Brattleboro rats, reaching a maximum of 24 cells per hypothalamus (approximately 0.6% of the vasopressin neurons). The increase occurred in both male and female animals but was significantly greater in females. The average incidence of such cells was 6 times greater in the supraoptic than in the paraventricular nucleus. No such cells could be detected in either nucleus of Long Evans rats despite the evidence for hybrid mRNA in these animals. Moreover, no accumulation of peptide translated from the hybrid mRNAs derived from the 5' end of the oxytocin gene and the 3' end of the vasopressin gene could be detected in either Brattleboro or Long Evans animals. These results strongly suggest that the accumulation of peptide in the rough endoplasmic reticulum of vasopressin neurons in homozygous Brattleboro rats is due to an abnormality other than the somatic crossing-over mutation. A second type of abnormal magnocellular neuron with accumulations of peptide in the rough endoplasmic reticulum, in which the immunophenotype of the peptide reveals products derived only from the oxytocin precursor, was present in both Long Evans and Brattleboro rats, but did not increase with age in Brattleboro rats. The incidence of these cells was similar in the supraoptic and paraventricular nuclei.  相似文献   
993.
Purpose. The objective of this study is to correlate drug release mechanism with measured drug concentration profiles in gel layers of Carbopol® matrices containing mesalamine or benzoic acid. Methods. Release rate experiments with Carbopol® matrices were performed using a rotating disk apparatus. Matrices were frozen and the gel layer in the matrices was sliced using a microtome in a cryostat. Drug concentration profiles were determined by direct measurement of the concentration of the drug in the gel slices. The pH of the slices was measured using microelectrodes, and water content was measured by Karl Fisher titration. Results. The concentration gradient in mesalamine matrices decreased over time and correlated with square root of time release rate kinetics. The concentration profiles of benzoic acid were unchanged over time and correlated with zero order release rate kinetics. Carbopol gel layers were highly hydrated (93–95% water). Gel layers in matrices with mesalamine had a more alkaline microenvironmental pH. This higher pH resulted in increased growth of the thickness of the gel layer and a reduction drug diffusivity in comparison to benzoic acid matrices. Conclusions. The release rate kinetics of mesalamine and benzoic acid correlated to the measured concentration profiles. The shape of the concentration profiles is determined by the rate of growth of the Carbopol® gel layer and drug diffusivity.  相似文献   
994.
National Salmonella & Escherichia Centre situated at Central Research Institute, Kasauli receives Salmonella strains from all over the country. Eight hundred and fourteen Salmonella strains belonging to 14 serotypes received during 1986 were studied for antibiotic resistance and Minimum Inhibitory concentration (MIC) with regard to ampicillin (A), chloramphenicol (C), furazolidone (Fz) and gentamicin (G). Resistance to ampicillin was found to be highest (80%) and furazolidone the least (0.1%). Similarly a large number of strains (31%) had very high MIC values greater than 640 mcg per ml for chloramphenicol, whereas only 3.4% strains were found to have MIC values greater than 640 mcg per ml for gentamicin. The present findings have been discussed in the light of similar data published from this Centre earlier and from other sources in India.  相似文献   
995.
Prognostic factors in myeloma are not only important for allowing comparisons to be made between therapeutic protocols but they also provide us with an insight into the pathophysiology of the disease and important mechanisms which result in disease progression. Prognostic factors in myeloma relate to the inherent proliferative capacity of the malignant clone, tumor bulk, renal function and other factors which reflect tumor host and host tumor interactions. The highly significant effect of the labelling index (LI) suggests that the clonogenic cell is ontologically very close to the malignant plasma cell on which the labelling index is derived. The explanation for the important role of the β2-microglobulin (β2M) level over and above its reflection of renal function is as yet unclear.  相似文献   
996.
  Variability in the interpretation of micturating cystourethrography by paediatric radiologists for the diagnosis of vesicoureteric reflux in children was evaluated. All 265 micturating cystourethrograms (MCUs) that were available from 304 consecutive children aged 0.5 – 61 months  –  who were investigated after their first urine infection between 1993 and 1995 as part of a prospective cohort study  –  were selected for interpretation. Three experienced paediatric radiologists from the same department independently interpreted the MCUs according to the grading system of the International Reflux Study in Children, from grades 0 to V, with the presence of intrarenal reflux also noted. Apart from being informed that urine infection was the indication for the MCU, no other clinical information was given to the radiologists. The indices of variability used were the percentage of agreement and the kappa statistic, expressed as a percentage. Both measures were weighted with integers representing the number of categories from perfect agreement. Disagreement was analysed for children and kidneys. For the diagnosis of vesicoureteric reflux in individual patients, including grade, the percentage of agreement was 96% – 97% (kappa 90% – 91%) and the weighted percentage of agreement was 96% – 98% (weighted kappa 93% – 94%). The same high level of agreement was present for individual kidneys, with a percentage of agreement of 97% – 98% (kappa 89% – 92%) and a weighted percentage of agreement of 98% – 99% (kappa 94% – 95%). There was near perfect agreement in the interpretation of radiological micturating cystourethrography among three experienced paediatric radiologists for the diagnosis and grade of vesicoureteric reflux. Any variations in the medical care of children suspected of having vesicoureteric reflux are not explained by differences in the reporting of this diagnostic test. Received June 19, 1996; received in revised form November 1, 1996; accepted December 6, 1996  相似文献   
997.
The pathogenesis of chronic pelvic pain syndrome continues to be an enigma. The observation of inflammatory cells in urine, ejaculate, prostate fluid, and prostate tissue combined with changed local expressions of cytokines, immunoglobulins, complement, and other inflammatory markers led to the hypothesis of an involvement of the immune system in this clinical entity. This review presents a survey of the immunology-related data available for chronic pelvic pain syndrome and attempts to explain them in the context of causes and consequences.  相似文献   
998.
999.
Presented are the results of an extensive noninvasive assessment of supraclinoid internal carotid artery (ICA) stenosis with moyamoya-like vasculopathy in 3 patients with a history of stroke. Five noninvasive criteria for the diagnosis based on magnetic resonance imaging of the brain, and hemodynamic testing using ocular pneumoplethysmography, duplex carotid ultrasound, and transcranial Doppler sonography were established: (1) normal ocular pneumoplethysmography demonstrating no pressure significant stenosis to the level of the ophthalmic artery; (2) abnormal Doppler spectral waveforms showing either no flow or a high-resistance flow pattern for the ipsilateral cervical internal carotid artery; (3) paradoxically low flow velocities for the ipsilateral intracranial (ICA) and middle cerebral artery (MCA), and markedly abnormal high velocities for the contralateral ICA and MCA; (4) decreased ipsilateral MCA vasomotor reactivity; and (5) deep MCA territory ipsilateral subcortical watershed infarction evidenced by magnetic resonance imaging. This report demonstrates that a noninvasive battery of tests may be useful in the early diagnosis and treatment of these patients.  相似文献   
1000.
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