全文获取类型
收费全文 | 88633篇 |
免费 | 7922篇 |
国内免费 | 8572篇 |
出版年
2023年 | 1584篇 |
2022年 | 1608篇 |
2021年 | 2479篇 |
2020年 | 2883篇 |
2019年 | 3734篇 |
2018年 | 3292篇 |
2017年 | 2875篇 |
2016年 | 3007篇 |
2015年 | 3008篇 |
2014年 | 4527篇 |
2013年 | 6182篇 |
2012年 | 3718篇 |
2011年 | 4305篇 |
2010年 | 3221篇 |
2009年 | 4334篇 |
2008年 | 4475篇 |
2007年 | 4730篇 |
2006年 | 4383篇 |
2005年 | 3725篇 |
2004年 | 3220篇 |
2003年 | 3104篇 |
2002年 | 2890篇 |
2001年 | 2424篇 |
2000年 | 2150篇 |
1999年 | 1735篇 |
1998年 | 1579篇 |
1997年 | 1420篇 |
1996年 | 1376篇 |
1995年 | 1382篇 |
1994年 | 1294篇 |
1993年 | 1156篇 |
1992年 | 1134篇 |
1991年 | 980篇 |
1990年 | 831篇 |
1989年 | 783篇 |
1988年 | 615篇 |
1987年 | 599篇 |
1986年 | 545篇 |
1985年 | 829篇 |
1984年 | 1029篇 |
1983年 | 801篇 |
1982年 | 847篇 |
1981年 | 669篇 |
1980年 | 660篇 |
1979年 | 599篇 |
1978年 | 462篇 |
1977年 | 426篇 |
1976年 | 393篇 |
1974年 | 255篇 |
1973年 | 267篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
目的:探讨踝肱指数(ABI)与糖尿病周围神经病变及中医证候积分的相关性。方法:选取我院内分泌科收治辩证以气阴两虚
为证型的糖尿病患者66 例,根据踝肱指数实验将患者分为ABI降低组(0.9>ABI>0.5)和ABI 正常组(1.4>ABI>0.9)。记录患者神
经病变症状尼龙丝检查以及中医症候评分,分析ABI与糖尿病周围神经病变及中医证候积分的相关性。结果:ABI降低组的糖尿
病周围神经病变的患病率高于ABI正常组(P<0.05)。ABI 降低组发麻、针刺感症状的发生率高于ABI 正常组,且有统计学差异
(P<0.05)。ABI降低组10 g尼龙丝检查异常者多于ABI正常组,差异显著(P<0.05)。ABI降低组的感觉振动阈值高于ABI正常组
(P<0.05)。ABI数值与中医证候积分呈负向直线相关(P<0.05)。结论:糖尿病患者ABI数值与糖尿病周围神经病变和中医证候积
分具有相关性。 相似文献
2.
目的:研究心脏康复运动对冠脉支架植入术后患者血脂、血糖、体重指数及生活质量的影响。方法:对实施冠脉支架植入术的
146例患者进行比较分析,根据随机原则分为试验组76 例及对照组70 例。对照组患者给予常规的健康教育及冠心病二级预防指
导,给予定期随访。试验组患者在此基础上给予规律的康复运动指导。经过6 个月随访,比较两组患者血脂、HbA1C、体重指数及
生活质量情况。结果:试验组患者通过为期6 个月的规律的心脏康复运动指导,其血脂、HbA1C等冠心病危险因素控制情况优于
对照组,差异有统计学意义(P<0.05)。同时,6个月后,试验组康复运动六月后sF 量表各项评分与对照组同期比较,差异均有统计
学意义(P<0.05)。结论:规范的心脏康复运动指导能够有效改善冠脉支架植入术后患者血脂、血糖情况,提高患者生活质量。 相似文献
3.
4.
5.
6.
7.
8.
Colin A. Lee Winsor H. Watson III 《Marine and Freshwater Behaviour and Physiology》2016,49(4):277-290
Although research on satiation has revealed much about the effect of sensory inputs on motivational state, we have yet to fully understand exactly how satiating signals influence the neural circuits underlying specific behaviors. One organism that is well suited for addressing this question is the nudibranch Melibe leonina, because its feeding activity is easily quantified, it has translucent skin that makes the stomach easy to observe, and it has large, identifiable neurons that are very suitable for subsequent analysis of the neural correlates of satiation. In this study our goal was to document the time course of satiation in Melibe, and determine if stomach distention contributes to satiation. When exposed to brine shrimp (Artemia), Melibe immediately commenced stereotypic oral hood movements to capture prey, and continued to do so for approximately five hours. Individuals eventually stopped, despite the continued presence of food, and the slowing and eventual termination of oral hood closures was correlated with distension of the stomach caused by the ingested Artemia. We obtained further evidence that stomach distension is one of the underlying causes of satiation by injecting artificial non-nutritive food into the stomach, and by cutting open part of the stomach wall to prevent it from filling and distending. The first treatment caused satiation to occur more rapidly, while the second treatment delayed satiation. Both results demonstrate that in Melibe stomach distention has a major impact on the motivation to feed. These findings provide the framework for subsequent studies designed to determine precisely how stomach distention influences feeding circuits. 相似文献
9.
Evaluation of the fossil fish‐specific diversity in a chadian continental assemblage: Exploration of morphological continuous variation in Synodontis (Ostariophysi,Siluriformes) 下载免费PDF全文
In the fossil record, the quantification of continuous morphological variation has become a central issue when dealing with species identification and speciation. In this context, fossil taxa with living representatives hold great promise, because of the potential to characterise patterns of intraspecific morphological variation in extant species prior to any interpretation in the fossil record. The vast majority of catfish families fulfil this prerequisite, as most of them are represented by extant genera. However, although they constitute a major fish group in terms of distribution, and ecological and taxonomic diversity, the quantitative study of their past morphological variation has been neglected, as fossil specimens are generally identified based on the scarcest remains, that is, complete neurocrania that bear discrete characters. Consequently, a part of freshwater catfish history is unprospected and unknown. In this study, we explored the morphological continuous variation of the humeral plate shape in Synodontis catfishes using Elliptic Fourier Analysis (EFA), and compared extant members and fossil counterparts. We analysed 153 extant specimens of 11 Synodontis species present in the Chad basin, in addition to 23 fossil specimens from the Chadian fossiliferous area of Toros Menalla which is dated around 7 Ma. This highly speciose genus, which is one of the most diversified in Africa, exhibits a rich fossil record with several hundred remains mostly identified as Synodontis sp. The analysis of the outline of the humeral plate reveals that some living morphological types were already represented in the Chad Basin 7 My ago, and allows for the discovery of extinct species. Beside illuminating the complex Neogene evolutionary history of Synodontis, these results underline the interest in the ability of isolated remains to reconstruct a past dynamic history and to validate the relevance of EFA as a tool to explore specific diversity through time. J. Morphol. 277:1486–1496, 2016. © 2016 Wiley Periodicals, Inc. 相似文献
10.
《Peptides》2014
The aim of our study was to investigate the appearance, density and distribution of ghrelin cells and GHS-R1a and GHS-R1b in the human stomach and duodenum during prenatal and early postnatal development. We examined chromogranin-A and ghrelin cells in duodenum, and GHS-R1a and GHS-R1b expression in stomach and duodenum by immunohistochemistry in embryos, fetuses, and infants. Chromogranin-A and ghrelin cells were identified in the duodenum at weeks 10 and 11 of gestation. Ghrelin cells were detected individually or clustered within the base of duodenal crypts and villi during the first trimester, while they were presented separately within the basal and apical parts of crypts and villi during the second and third trimesters. Ghrelin cells were the most numerous during the first (∼11%) and third (∼10%) trimesters of gestation development. GHS-R1a and GHS-R1b were detected at 11 and 16 weeks of gestation, showed the highest level of expression in Brunner's gland and in lower parts of duodenal crypts and villi during the second trimester in antrum, and during the third trimester in corpus and duodenum. Our findings demonstrated for the first time abundant duodenal expression of ghrelin cells and ghrelin receptors during human prenatal development indicating a role of ghrelin in the regulation of growth and differentiation of human gastrointestinal tract. 相似文献