全文获取类型
收费全文 | 16140篇 |
免费 | 1220篇 |
国内免费 | 930篇 |
专业分类
耳鼻咽喉 | 69篇 |
儿科学 | 101篇 |
妇产科学 | 109篇 |
基础医学 | 3056篇 |
口腔科学 | 192篇 |
临床医学 | 630篇 |
内科学 | 1752篇 |
皮肤病学 | 205篇 |
神经病学 | 1621篇 |
特种医学 | 330篇 |
外国民族医学 | 5篇 |
外科学 | 653篇 |
综合类 | 4113篇 |
现状与发展 | 4篇 |
预防医学 | 676篇 |
眼科学 | 176篇 |
药学 | 2306篇 |
中国医学 | 1234篇 |
肿瘤学 | 1058篇 |
出版年
2024年 | 25篇 |
2023年 | 92篇 |
2022年 | 208篇 |
2021年 | 266篇 |
2020年 | 307篇 |
2019年 | 277篇 |
2018年 | 254篇 |
2017年 | 425篇 |
2016年 | 433篇 |
2015年 | 519篇 |
2014年 | 754篇 |
2013年 | 990篇 |
2012年 | 934篇 |
2011年 | 1080篇 |
2010年 | 887篇 |
2009年 | 803篇 |
2008年 | 908篇 |
2007年 | 916篇 |
2006年 | 908篇 |
2005年 | 741篇 |
2004年 | 726篇 |
2003年 | 652篇 |
2002年 | 571篇 |
2001年 | 474篇 |
2000年 | 439篇 |
1999年 | 391篇 |
1998年 | 289篇 |
1997年 | 261篇 |
1996年 | 289篇 |
1995年 | 263篇 |
1994年 | 240篇 |
1993年 | 241篇 |
1992年 | 202篇 |
1991年 | 155篇 |
1990年 | 148篇 |
1989年 | 126篇 |
1988年 | 125篇 |
1987年 | 105篇 |
1986年 | 92篇 |
1985年 | 125篇 |
1984年 | 120篇 |
1983年 | 54篇 |
1982年 | 92篇 |
1981年 | 91篇 |
1980年 | 62篇 |
1979年 | 42篇 |
1978年 | 39篇 |
1977年 | 34篇 |
1976年 | 31篇 |
1970年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Masakatsu Takashima Wataru Tanaka Hiroki Matsuyama Hayato Tajiri Hiroyuki Sakakibara 《Nutrients》2021,13(4)
Quercetin has been shown to have anti-obesity effects, but it is unknown whether these effects can be transmitted from mothers to their progeny. In this study, we investigated whether maternal quercetin consumption during pregnancy has a protective effect on high-fat diet–induced hyper lipid levels and overweight in progeny. Female mice consumed a control diet or a diet containing 1.0% quercetin during breeding. The male progeny were then divided into four groups that were (1) sacrificed at postnatal day 3; (2) born to dams fed the control diet and also fed the control diet (C-C), (3) born to dams fed the control diet and then fed a 30% high-fat diet (C-HF), or (4) born to dams fed the Q-diet and then fed the HF diet (Q-HF). Maternal consumption of quercetin did not affect body weight or blood lipid parameters in either dams or neonates at postnatal day 3. After 13 weeks, the Q-HF group exhibited greater body and liver weights, and higher blood cholesterol levels than the C-HF group. However, the total cholesterol/ high density lipoprotein (HDL)-cholesterol ratios in the Q-HF and C-C groups remained similar. In conclusion, maternal quercetin consumption does not appear to protect the next generation from high-fat diet–induced hyper cholesterol level in the blood and liver, and consequently overweight, but may help regulate the total cholesterol/HDL-cholesterol ratio. 相似文献
62.
一氧化氮对谷氨酸单钠脑损害小鼠学习记忆能力的影响 总被引:3,自引:2,他引:1
目的 观察谷氨酸单钠 (MSG)对小鼠学习记忆的影响及血浆、脑内NO含量的变化。方法 给断乳分窝小鼠MSG灌胃 ,每天 2次 ,连续 30d ,31d早灌胃后对小鼠进行迷宫行为训练 ,2 4h后对其进行迷宫记忆检测 ,用硝酸还原酶法检测血浆脑内的NO含量。结果 MSG对小鼠学习记忆能力有影响并存在剂量效应关系 ,其血浆、脑中NO含量均升高并有显著差异 (P <0 .0 5 )。结论 NO可加重MSG对小鼠学习与记忆的损害作用。 相似文献
63.
恒河猴tPA基因的克隆、测序与真核表达 总被引:2,自引:0,他引:2
本试验采用高浓度乙二醇(EG-8)作为胚胎冷冻保护剂,以高浓度的半乳糖作为解冻稀释液,对MMTV-Wnt-1转基因小鼠的早期囊胚进行玻璃化冷冻保存。结果在EG-2中平衡4-6min和解冻时间为3-5min时获得了最佳冷冻效果。此条件下冷冻胚胎的总回收率为88.61%(109/123);回收胚胎在体外发育率达88.99%(97/109);孵化率达81.65%(89/109);发育胚胎的移植出生率为38.36%(69/181);冷漠胚胎移植出生后经PCR检测一半小鼠整合阳性。结果表明使用高浓度的乙二醇作为冷冻保护剂和以高浓度的半乳糖作为冻稀释液能有效地保存转基因小鼠胚胎。 相似文献
64.
电磁辐射对小鼠神经系统超微结构影向的分析 总被引:1,自引:0,他引:1
目的探讨移动电话的电磁辐射对生物体的影响.方法用大众常用移动电话作为辐射源,工作频率为900MHz,功率密度为1190μW/cm2,在一定范围对小鼠辐射2h/d,30d后把小鼠断颈处死,取出大脑皮层、海马和小脑进行电镜观察分析.结果电镜所见,处理组与对照组小鼠的神经系统的细胞超微结构未见明显异常.结论一定时间内,移动电话的电磁辐射,对小鼠神经系统的细胞超微结构并没有明显影响. 相似文献
65.
国产甲磺酸培氟沙星体内抗菌活性试验 总被引:1,自引:0,他引:1
口服和静脉给予国产甲磺酸培氟沙星对大肠杆菌-12、克氏肺炎杆菌-64和绿脓杆菌-14感染小鼠均有保护作用,其中口服给药的PD_(50)分别为1.08,5.87和8.10mg/kg;静脉给药的PD_(50)分别为0.54,3.10和7.02mg/kg。 相似文献
66.
Valrie Kouskoff Jean-Luc Vonesch Christophe Benoist Diane Mathis 《European journal of immunology》1995,25(1):54-58
The expression of recombination activating gene (RAG) products, responsible for T cell receptor (TcR) gene rearrangement, is shut off during positive selection of thymocytes. The precise stage at which this down-regulation occurs remains somewhat controversial. We have analyzed RAG-1 expression in thymocytes of TcR transgenic mice carried on selecting versus non-selecting genetic backgrounds, both by in situ hybridization on thymus sections and by polymerase chain reaction amplification of RNA from sorted cells. The data from several transgenic lines indicate that RAG expression is already reduced in immature, cortical, CD4+CD8+ cells in the presence of positively selecting major histocompatibility complex molecules, although complete shut-off is not achieved until the mature, medullary, single-positive stage. This finding has practical and theoretical significance for studies on the mechanism of positive selection. 相似文献
67.
68.
目的 探讨CD44v6、E -Cadherin表达与人鼻咽癌裸鼠移植瘤转移的关系。方法 分别将人鼻咽癌细胞克隆株F1在体外与鼠肺块共同孵育及胸内移植 ,然后将带瘤细胞肺块 (Ⅰ组 )和胸内瘤组织块 (Ⅱ组 )各行裸鼠皮下移植 ,并与瘤细胞悬液皮下移植瘤 (Ⅲ组 )比较 ,观察各组移植瘤转移特点。采用免疫组织化学技术检测各组移植瘤回复培养细胞CD44v6和E -Cadherin表达。结果 Ⅰ组和Ⅱ组皮下移植瘤的总转移率和淋巴结转移率均高于Ⅲ组 (其中ⅠvsⅢ ,P <0 .0 5) ;肺转移仅发生在Ⅰ组。这两组移植瘤细胞CD44v6表达水平明显增高 ,其阳性细胞数分别为 (79.7± 5.7) %、(74.1± 3.1 ) % ,第 3组为 (65.6± 4.31 ) %移植瘤转移率与CD44v6高表达密切相关 ;E -Cadherin阳性细胞分别为 (41 .7± 4.9) %、(43.8± 6.4) %和 (2 7.4± 4.9) % ,Ⅰ组、Ⅱ组与Ⅲ组之间比较 ,有显著差异 (P <0 .0 5)。结论 CD44v6的过表达和E -Cadherin功能障碍 ,可能在鼻咽癌侵袭转移中起一定作用。 相似文献
69.
Karin Hori Satoshi Yamazaki Chiaki Ohtaka-Maruyama Tomio Ono Tomohiro Iguchi Hisao Masai 《Genes to cells : devoted to molecular & cellular mechanisms》2023,28(10):679-693
The evolutionally conserved Cdc7 kinase plays crucial roles in initiation of DNA replication as well as in other chromosomal events. To examine the roles of Cdc7 in brain development, we have generated mice carrying Cdc7 knockout in neural stem cells by using Nestin-Cre. The Cdc7Fl/Fl NestinCre mice were born, but exhibited severe growth retardation and impaired postnatal brain development. These mice exhibited motor dysfunction within 9 days after birth and did not survive for more than 19 days. The cerebral cortical layer formation was impaired, although the cortical cell numbers were not altered in the mutant. In the cerebellum undergoing hypoplasia, granule cells (CGC) decreased in number in Cdc7Fl/F lNestinCre mice compared to the control at E15-18, suggesting that Cdc7 is required for DNA replication and cell proliferation of CGC at mid embryonic stage (before embryonic day 15). On the other hand, the Purkinje cell numbers were not altered but its layer formation was impaired in the mutant. These results indicate differential roles of Cdc7 in DNA replication/cell proliferation in brain. Furthermore, the defects of layer formation suggest a possibility that Cdc7 may play an additional role in cell migration during neural development. 相似文献
70.
Summary Ovulation was induced in immature mice by injections of pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (HCG) spaced 48 hours apart. The mice were divided into six groups: one group received intraperitoneal injections of normal saline, another group received alcoholic saline which was used as the vehicle of pineal indoles, and the remaining groups received respectively hydroxyindoleacetic acid (HIAA), melatonin (MEL), methoxytryptamine (MTA) and methoxytryptophol (MTP). The pineal indoles were administered 24 hours before, on the same day as, 24 hours after and 48 hours after the PMSG injection. The mice were sacrificed 24 hours after the HCG injection. The numbers of growing primary follicles, multilaminar primary follicles, Graafian follicles, preovulatory follicles and corpora lutea in the ovary were not altered by treatment with pineal indoles. However, there was an increased incidence of follicular atresia in the groups treated with MEL, MTA and MTP. The pineal indoles did not affect the number of ovulated oocytes, but there was a large number of degenerated and fragmented ovulated oocytes in the MTA- and MTP-treated groups. Treatment with MEL, MTA and MTP also resulted in lower plasma levels of estradiol-17 and progesterone. 相似文献