全文获取类型
收费全文 | 21591篇 |
免费 | 1934篇 |
国内免费 | 1467篇 |
专业分类
耳鼻咽喉 | 126篇 |
儿科学 | 243篇 |
妇产科学 | 197篇 |
基础医学 | 2685篇 |
口腔科学 | 374篇 |
临床医学 | 3044篇 |
内科学 | 3083篇 |
皮肤病学 | 228篇 |
神经病学 | 1125篇 |
特种医学 | 859篇 |
外国民族医学 | 13篇 |
外科学 | 2075篇 |
综合类 | 3970篇 |
现状与发展 | 5篇 |
预防医学 | 1085篇 |
眼科学 | 564篇 |
药学 | 2306篇 |
21篇 | |
中国医学 | 1186篇 |
肿瘤学 | 1803篇 |
出版年
2024年 | 59篇 |
2023年 | 373篇 |
2022年 | 794篇 |
2021年 | 1159篇 |
2020年 | 893篇 |
2019年 | 711篇 |
2018年 | 812篇 |
2017年 | 684篇 |
2016年 | 699篇 |
2015年 | 1062篇 |
2014年 | 1281篇 |
2013年 | 1095篇 |
2012年 | 1612篇 |
2011年 | 1771篇 |
2010年 | 1040篇 |
2009年 | 818篇 |
2008年 | 1085篇 |
2007年 | 1054篇 |
2006年 | 1091篇 |
2005年 | 1057篇 |
2004年 | 701篇 |
2003年 | 634篇 |
2002年 | 550篇 |
2001年 | 487篇 |
2000年 | 506篇 |
1999年 | 515篇 |
1998年 | 345篇 |
1997年 | 334篇 |
1996年 | 227篇 |
1995年 | 218篇 |
1994年 | 232篇 |
1993年 | 131篇 |
1992年 | 129篇 |
1991年 | 127篇 |
1990年 | 133篇 |
1989年 | 98篇 |
1988年 | 97篇 |
1987年 | 83篇 |
1986年 | 73篇 |
1985年 | 72篇 |
1984年 | 25篇 |
1983年 | 17篇 |
1982年 | 25篇 |
1981年 | 21篇 |
1980年 | 12篇 |
1979年 | 15篇 |
1978年 | 11篇 |
1977年 | 9篇 |
1976年 | 7篇 |
1975年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Uroscopy in the 21st century: high-field NMR spectroscopy 总被引:1,自引:1,他引:0
Neild GH; Foxall PJ; Lindon JC; Holmes EC; Nicholson JK 《Nephrology, dialysis, transplantation》1997,12(3):404-417
From the experiments described, it can be seen that there are different
research approaches that can be taken and these are summarized in Table 1.
Whereas much scientific research is principally hypothesis led, there
remains, nevertheless, an important place for exploratory research. High
resolution NMR can measure, directly and simultaneously, a wide range of
endogenous metabolites in biological fluids and has the unique capability
of providing structural information on the metabolites detected. It has
proved to be a powerful research tool with which to study inherited
metabolic diseases, renal disease, drug metabolism, and toxicity, and can
be used to monitor the effects of drug therapy. For instance, by using a
library of experimental toxins one can map the metabolic profile of
site-specific nephron injury. With this approach in man one could
eventually take an unknown disease such as Balkan nephropathy and predict
the initial site of tubular injury, the mode of injury and therefore the
kind of toxin capable of producing that injury. NMR spectroscopic
techniques are still advancing rapidly, with ever increasing sensitivity
and sophistication of NMR pulse sequences to enhance structural elucidation
in complex mixtures. Given the advances in directly coupled HPLC-NMR and
even HPLC-NMR-mass spectroscopy it is likely that these technologies in
conjunction with pattern recognition will make major contribution to our
understanding of renal processes and provide new diagnostic insights in the
21st century.
相似文献
112.
用K.S熵(一种信息熵)判别林业系统中生态和经济的协调关系,并提出了控制和改进现有林业系统的有效途径。 相似文献
113.
Chang-Fu Peng Yu-Jie Li Yuan-Jian Li Han-Wu Deng 《The Journal of pharmacy and pharmacology》1995,47(7):614-617
This study was designed to explore the effect of ginsenosides, saponins from Panax ginseng, on the vasodilator nerve actions in the rat perfused mesentery and the mechanism of this effect. In the rat perfused mesentery, when adrenergic nerves were blocked by guanethidine (5 × 10?6 M) and vascular muscle tone was increased with methoxamine (5 × 10?6-10?5 M), transmural field stimulation produced a frequency-dependent vasodilator response, which is due to the release of calcitonin generelated peptide; ginsenosides significantly suppressed this vasodilator response in a concentration-dependent manner (3–30 μg mL?1). After pretreatment with saponin (50 μg mL?1, 3min) to damage endothelial cells, this suppressing effect of ginsenosides was unaltered. However, the effect was abolished by Nω-nitro-l-arginine methyl ester (L-NAME) (10?4 M), an inhibitor of nitric oxide synthesis and addition of l -arginine (3 × 10?4 M) restored this suppressing effect. Methylene blue (10?5 M), an inhibitor of guanylate cyclase, also abolished the suppressing effect of ginsenosides. However, ginsenosides did not alter the relaxation responses caused by exogenous calcitonin gene-related peptide administration. We conclude that ginsenosides can produce an inhibitory effect on the vasodilator response prejunctionally in the rat perfused mesentery and that this effect of ginsenosides may be mediated by nitric oxide released from non-adrenergic, non-cholinergic nerves. 相似文献
114.
作者采用PCR方法克隆了我国海南省FCC1/HN株P190抗原两个保守区基因,分别定名为P190CRI和P190CRV。基因片段经纯化后连接到pUC18载体中进行DNA序列分析,结果显示:除了P190CRV中有5个碱基变换外,其余序列均与MAD20型序列一致。经序列分析的两个基因片段分别与pGEX-2T载体连接,经双酶切鉴定后转化感受态JM109(DE_3)大肠杆菌进行高效融合表达,并且用Sepharose 4B-谷胱甘肽层析柱进行亲和纯化,结果为:两个插入基因片段均得到高效融合表达,经一步亲和纯化后就取得高纯度的重组蛋白。 相似文献
115.
高渗盐/甘露醇液对内毒素小鼠脑腺细胞凋亡的保护作用 总被引:2,自引:0,他引:2
为探讨高渗盐/甘露醇法(HSM)对内毒素诱导小鼠胸腺细胞凋亡的影响,取昆明纯种小白鼠24只平分为三组,即(1)对照组,腹腔注射生理盐水;(2)内毒素实验组(LPS组),腹腔注入内毒素;(3)LPS+HSM组,腹腔注入内毒素前后共注HSM二次。结果示,第三组胸腺细胞凋亡百分率及DNA断裂百分率明显低于第二组(P〈0.01),DNA断裂碎片中的琼脂糖凝胶电泳未见典型的梯状带。提示HSM对内毒素诱导的小 相似文献
116.
江油市粮食中霉菌污染调查 总被引:6,自引:0,他引:6
对江油市胡豆,黄豆,玉米,大米,麦子,碗豆共375件样品进行霉菌污染调查。调查表明:粮食中霉菌平均侵染率87.8%,其中黄豆,碗豆污染较轻,其侵浸率明显低于小麦,大米,胡豆。胡豆,碗豆,黄豆以曲霉菌属为主;小麦以交链孢霉为主,大米以青霉菌属为主;玉米以预 相似文献
117.
自1990年以来收治直径在2-5.6cm的大、巨型垂体腺瘤33例。依肿瘤生长形态与扩展范围将其简略分为三种类型。A型:瘤体位于鞍内或侵入蝶窦;B型;瘤体呈椭圆形或哑铃向鞍上扩展,三脑室明显移位抬高;C型:瘤体巨大侵入三脑室阻塞室间孔或明显的鞍周扩展。 相似文献
118.
Introduction : Hypertrophic scar is a devastating sequel to burns and other tangential skin injuries. It follows deep dermal injuries and does not occur after superficial injuries. Nitric oxide (NO) plays many important roles in wound healing from inflammation to scar remodeling. Studies have shown that expression of nitric oxide synthase and nitric oxide production are decreased in human hypertrophic scar. However little is known about NO involvement in the early stages of hypertrophic scarring, because of the lack of an animal model. It was recently reported that the female red Duroc pig (FRDP) makes thick scar, which is similar to human hypertrophic scar. We hypothesized that NO production in wounds on the female, red Duroc pig is similar to that of human hypertrophic scar and that NO involvement in deep wounds is different from that in superficial wounds. Methods : Superficial (0.015” to 0.030”) and deep (0.045” to 0.060”) wounds were created on the backs of four FRDPs. Biopsies were collected at weeks 1.5, 4, 8 and 21 post wounding including samples of uninjured skin. Nitric oxide levels were measured with the Griess reaction assay and normalized with tissue protein level. Results : Superficial wounds healed with an invisible scar whereas the deep wounds healed with scar resembling mild hypertrophic scar. The thickness of the scars from the deep wounds was significantly greater than uninjured skin and healed superficial wounds (p < 0.01). NO levels were increased at 1.5 weeks in deep wounds compared to superficial wounds and uninjured skin (p < 0.05). At 8 weeks, NO levels in deep wounds had returned to the level of uninjured tissue and superficial wounds. By 21 weeks, NO levels had decreased significantly when compared to superficial wounds (p < 0.01). There were no differences in NO levels between uninjured skin and superficial wounds at any time point (p > 0.05). Conclusions : NO production is similar in late, deep wounds on the female, red Duroc pig to that reported in the literature for human hypertrophic scar further validating this animal model. NO production is quite different after deep wounds as compared to superficial wounds in the FRDP. Early elevation in nitric oxide production might account for excessive inflammation in deep wounds that become thick scars in the FRDP. Nitric oxide regulators and effects at early stages of scar formation should be elucidated further and the FRDP appears to be a useful model. 相似文献
119.
中国三城市儿童步行者道路交通安全状况回顾性研究 总被引:1,自引:0,他引:1
目的了解北京、上海、广州三城市儿童步行安全状况及相关因素,为加强儿童道路交通伤害预防、干预提供科学依据。方法回顾性收集2000~2004年三城市交管部门14岁以下儿童步行者交通伤害发生资料。结果三城市5年间儿童步行者道路交通伤害发生率为14.93/10万,男女比例为1.79∶1,5~9岁为高发年龄,儿童步行者发生道路交通伤、亡的主要责任方为行人,受伤害儿童43.0%为轻伤,46.6%为重伤,10.4%为死亡。结论道路交通伤害严重威胁儿童安全与健康,儿童步行者发生道路交通伤害与多种因素有关,需社会各个部门参与预防。 相似文献
120.