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   72278篇
  免费   5413篇
  国内免费   2067篇
耳鼻咽喉   468篇
儿科学   1101篇
妇产科学   521篇
基础医学   5440篇
口腔科学   1155篇
临床医学   9501篇
内科学   9956篇
皮肤病学   426篇
神经病学   3200篇
特种医学   1876篇
外国民族医学   2篇
外科学   6724篇
综合类   13033篇
现状与发展   5篇
预防医学   6311篇
眼科学   2781篇
药学   10124篇
  204篇
中国医学   6301篇
肿瘤学   629篇
  2024年   269篇
  2023年   1177篇
  2022年   2483篇
  2021年   3220篇
  2020年   2830篇
  2019年   2074篇
  2018年   2076篇
  2017年   2263篇
  2016年   2375篇
  2015年   2345篇
  2014年   4826篇
  2013年   5212篇
  2012年   4378篇
  2011年   4759篇
  2010年   3580篇
  2009年   3216篇
  2008年   3374篇
  2007年   3612篇
  2006年   2990篇
  2005年   2503篇
  2004年   2169篇
  2003年   1742篇
  2002年   1535篇
  2001年   1431篇
  2000年   1181篇
  1999年   1087篇
  1998年   937篇
  1997年   904篇
  1996年   807篇
  1995年   835篇
  1994年   759篇
  1993年   685篇
  1992年   664篇
  1991年   586篇
  1990年   536篇
  1989年   480篇
  1988年   484篇
  1987年   434篇
  1986年   402篇
  1985年   442篇
  1984年   383篇
  1983年   230篇
  1982年   330篇
  1981年   237篇
  1980年   205篇
  1979年   180篇
  1978年   159篇
  1977年   96篇
  1976年   86篇
  1975年   54篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
171.
The renin-angiotensin system is involved in control of blood pressure and salt and fluid homeostasis. Genes for components of this system have been of major focus in research on the causation of the common, complex, polygenic trait, essential hypertension (HT). Association of an A→C variant at nucleotide 1166 of the angiotensin II type 1 receptor (AT1R) gene with HT, but an absence of linkage of this locus with this disease, has been reported recently. Since confirmation in a different setting is imperative, we performed a cross-sectional case-control study of the A1166C variant in a well-characterized group of 108 Caucasian HT subjects with a strong family history (two affected parents) and early onset disease. Genotyping was by mismatch polymerase chain reaction/ Bfr I restriction fragment length polymorphism analysis. Frequency of the C1166allele was 0.40 in HTs and 0.29 in normotensives. The difference in genotype (χ2= 13, P = 0.0015) and allele (χ2= 5.3, P = 0.02) frequencies between the two groups was significant (odds ratio for CC vs AA+AC = 7.3 [95% CI, 1.9–31.9). The present results implicate the AT1R gene, or a locus in linkage disequilibrium with the variant tested, in the causation of essential HT.  相似文献   
172.
川芎嗪对弥漫性轴索损伤影像学变化及预后的影响   总被引:3,自引:0,他引:3  
目的:探讨川芎嗪对弥漫性轴索损伤(DAI)的治疗作用。方法:42例DAI患者随机分为两组,治疗组除常规治疗加用川芎嗪,对照组仅常规治疗。结果:两组在伤后影像学及预后方面均有显著性差异。结论:伤后早期应用川芎嗪能明显促进挫伤及出血灶的吸收,改善DAI的预后。  相似文献   
173.
Da-Nian Zhu, Long-Mei Xue, Peng Li. Effect of central muscarine receptor blockade. with DKJ-21 on the blood pressure and heart rote in stress-induced hypertensive rats.

The experiments were performed on Wistar or Sprague-Dawley rats of both sexes divided at random into stress and control groups. The rats in the stress groups were put into cages and subjected to electric foot-shocks and noises for 9-15 days, which caused an increase in blood pressure (BP) and heart rate (HR). In hypertensive rats DKJ-21 (4mg/lml) was injected intravenously (i.v.), and 0.5-1.0h after administration the BP and HR dropped from the high level to normotensive level. In normotensive rats, however, administration of DKJ-21 had no effect on BP or HR. In separate groups of normotensive rats, pretreatment of DKJ-21 (4 mg/l ml, i.v.) blocked the pressor and tachycardiac effect induced by microinjection of physostigmine (0.4μg/0.1 /μl/site), corticosterone (40μg/0.1μl/site) or aldosterone (40 μg/0.1 μl/site) into the rostral ventrolateral medulla (rVLM). Furthermore, DKJ-21 also attenuated the enhancement of the pressor response to stimulation of the defense area in the midbrain, which was induced by microinjection of drugs (mentioned above) into the rVLM. These results indicate that i.v. DKJ-21 can selectively block the muscarinic receptors in the rVLM in stress-induced hypertensive rats, which suggests that abnormal enhancement of cholinergic mechanism in the rVLM may be related to hypertensive effects of corticoids in this area.  相似文献   
174.
An improved sib-pair test for linkage is introduced which is superior to the previously proposed tests. The test is derived from the standard chi-squared goodness of fit statistic by restricting the alternative hypothesis to the genetically possible. Critical values are given and exact power comparisons are made with the previously proposed tests. The new test is shown to be more powerful for finite samples as well as being asymptotically uniformly most powerful. © 1993 Wiley-Liss, Inc.  相似文献   
175.
Summary. Eleven normotensive diabetics with noninsulin-dependent diabetes mellitus (NIDDM) (mean age 52.5 SD 8.2 years) and 11 controls (mean age 47.4 SD 8.9 years) had their ambulatory blood pressure and heart rate recorded non-invasively by the Oxford Medilog System in standard hospital conditions. The results were averaged as hourly means of systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MAP), and heart rate (HR) for the 24-h period and similarly for the ‘awake’ period (14.16 h) and the ‘asleep’ period (8–10 h). Hourly means for diabetics and controls showed no differences in blood pressure and heart rate over the 24 h. During sleep, control subjects showed a significant drop in SBP (P < 0.001), DBP (P < 0.001), MAP (P < 0.001) and HR (P < 0.001). However, this nocturnal dip in blood pressure could not be demonstrated in the diabetic group. Blood pressure variability was significantly increased in diabetics compared to controls during waking hours (P < 0.01). These results indicate that in noninsulin-dependent diabetics during sleep there is loss of the nocturnal dip of BP seen in normal subjects, and they have increased BP variability. These may be contributing factors to the development of hypertension and the accelerated target organ damage (TOD) seen in diabetes.,  相似文献   
176.
计算了单边椭圆缺口试件(SENCP)高应变区裂纹的J积分失效评定曲线(FAC),考察了影响FAC的几种因素。结果表明:在外加载荷与塑性屈服载荷之比(Lr)1.0时,用R6通用失效评定曲线进行结构高应变区裂纹断裂评定与疲劳剩余寿命估算是安全的。  相似文献   
177.
The duration of the late exteroceptive suppression period (ES2) of temporal muscle EMG activity has been reported to be reduced in patients suffering from chronic tension-type headache. Methods of recording and analysing ES2 have varied between centers and reproducibility of results within subjects , although insufficiently studied, has generally been poor. ES2 was investigated in 30 healthy subjects, using a computerized technique of recording, rectifying and averaging the EMG signals. Hour to hour and week to week variations of ES2 durations were calculated, and the influence of pain during a cold pressor test and of sustained muscle contraction on ES2 durations was investigated. The intra-individual variation of ES2 durations was 16.0% from hour to hour and 20.7% from week to week. The inter-individual variation was 36.7%. The present method for analysis of ES2 periods proved to be reliable, as the intra-observer variation was 4.2% and the inter-observer variation 4.6%. ES2 periods were significantly shorter on the first compared to the second day of examination ( p = 0.006) and during experimental pain ( p = 0.0005). We recommend the use of the computerized averaging technique in future studies and caution against the dependence of results upon factors such as conditioning and pain.  相似文献   
178.
Hereditary hypertriglyceridemic rats (hHTg) were developed as a new genetic model for the study of relationships between blood pressure (BP) and metabolic abnormalities. This strain has been produced by selective inbreeding from Wistar rats according to the rise of plasma triglycerides induced by a high-sucrose diet. Though hHTg rats display hypertriglyceridemia, impaired glucose tolerrance, hyperinsulinemia, insulin resistance and increased BP even without nutritional stimuli, high sucrose feeding further aggravates these symptoms. High plasma triglycerides levels in hHTg rats seem to be a consequence of their hyperproduction. Impaired insulin action is responsible for the defective glucoregulation in this strain. The loss of insulin responsiveness might be due to a reduction in the number of glucose transporters. Highly significant relationships among plasma triglycerides, ouabain-resistant Na+ transport and BP were demonstrated in the hHTg rats. Segregating populations (F2 hybrids) should be used for genetic analysis of the primary role of lipid and/or ion transport abnormalities in the pathogenesis of this form of genetic hypertension.  相似文献   
179.
本文报道pH指示剂吸收度比值法测定盐酸乙胺丁醇的含量。该法采用指示剂为0.05%茜素黄R,测定波长374nm和500nm;标准液为0.1mol/L NaOH;仪器为WFZ-800D_2型分光光度计。测得三批盐酸乙胺丁醇的含量分别为99.5±0.04%,99.4±0.05%和99.6±0.03%.同时与药典法比较,结果一致。  相似文献   
180.
Background : Wounds are a common problem, particularly in the elderly population. The scale of wound problems in hospital is largely unknown because wounds are widely dispersed. The present study examined the point prevalence of hospital wounds and undertook a pressure ulcer risk assessment of all patients on one day. Methods : All 360 inpatients were surveyed and thoroughly examined. A risk scale for pressure sore development, the Norton score, was applied. When wounds were found, information was collected to determine their aetiology. Results : Forty leg ulcers, 40 pressure sores, 85 surgical wounds and seven other types of wounds were found. Most leg ulcer and pressure sore cases were admitted for other reasons. The Norton score did not predict all cases of pressure ulceration. A total of 52% of wounds did not qualify for additional funding under current funding criteria. Conclusion : The prevalence of non-surgical wounds in Heidelberg Repatriation Hospital was easily underestimated. Wound care management can be optimized by staff education and protocol design, early identification of troublesome wounds and of at-risk patients, and a cross-sectional approach that incorporates wound-management teams.  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