全文获取类型
收费全文 | 118127篇 |
免费 | 11513篇 |
国内免费 | 8169篇 |
专业分类
耳鼻咽喉 | 935篇 |
儿科学 | 1376篇 |
妇产科学 | 1485篇 |
基础医学 | 15158篇 |
口腔科学 | 2498篇 |
临床医学 | 15469篇 |
内科学 | 18329篇 |
皮肤病学 | 1284篇 |
神经病学 | 7818篇 |
特种医学 | 4249篇 |
外国民族医学 | 58篇 |
外科学 | 12152篇 |
综合类 | 17537篇 |
现状与发展 | 22篇 |
一般理论 | 21篇 |
预防医学 | 7479篇 |
眼科学 | 3602篇 |
药学 | 11955篇 |
100篇 | |
中国医学 | 6179篇 |
肿瘤学 | 10103篇 |
出版年
2024年 | 257篇 |
2023年 | 1445篇 |
2022年 | 3874篇 |
2021年 | 5551篇 |
2020年 | 4125篇 |
2019年 | 3553篇 |
2018年 | 4027篇 |
2017年 | 3360篇 |
2016年 | 3301篇 |
2015年 | 4851篇 |
2014年 | 5992篇 |
2013年 | 5414篇 |
2012年 | 7842篇 |
2011年 | 8893篇 |
2010年 | 5375篇 |
2009年 | 4275篇 |
2008年 | 5733篇 |
2007年 | 5701篇 |
2006年 | 5770篇 |
2005年 | 5617篇 |
2004年 | 3621篇 |
2003年 | 3477篇 |
2002年 | 2904篇 |
2001年 | 4110篇 |
2000年 | 4160篇 |
1999年 | 3912篇 |
1998年 | 2079篇 |
1997年 | 1782篇 |
1996年 | 1404篇 |
1995年 | 1287篇 |
1994年 | 1077篇 |
1993年 | 748篇 |
1992年 | 1577篇 |
1991年 | 1371篇 |
1990年 | 1242篇 |
1989年 | 1278篇 |
1988年 | 1115篇 |
1987年 | 990篇 |
1986年 | 894篇 |
1985年 | 770篇 |
1984年 | 452篇 |
1983年 | 363篇 |
1982年 | 217篇 |
1981年 | 169篇 |
1980年 | 132篇 |
1979年 | 221篇 |
1973年 | 93篇 |
1972年 | 92篇 |
1971年 | 94篇 |
1968年 | 83篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
青年人群血清流感抗体水平纵向监测 总被引:5,自引:1,他引:4
通过对北京405例青年1992~1994年流感抗体的纵向监测结果表明,3年中B型流感表现很活跃,抗体分别在1993年和1994年春出现高峰。A型流感抗体在1993年春出现高峰。其中218例个体连续3年6次抗体检测,据抗体波动提示:3年中流感3个亚型总的感染频率为440%,每个体每年平均为1.4次,其中A1型感染频率最高,每个体3年内平均1.8次;A3型次之为1.52;B型为1.06。流感3个亚型抗体在机体内有67%~73%高水平抗体个体可在0.5~1年内下降至≤20的低水平。218例个体中A1型抗体3年内长期低水平者有3%,A3有9%,B有38%。 相似文献
102.
本研究选择10μg/ml、20μg/ml、40μg/ml浓度的溴氰菊酯处理白纹伊蚊C6/36细胞,以MMC作为阳性对照物,观察溴氰菊酯处理24h后对C6/36细胞染色体畸变率和姐妹染色单体互换(SCE)频率的影响。结果显示,三个浓度的溴氰菊酯对C6/36细胞染色体畸变率均没有显著影响(P<0.05);溴氰菊酯浓度在40μg/ml时可诱导C6/36细胞SCE频率轻度增高(P>0.05),而溴氰菊酯浓度在10μg/ml、20μg/ml时,对C6/36细胞SCE频率没有诱导作用。表明溴氰菊酯对C6/36细胞的遗传学效应较弱 相似文献
103.
Investigation of Role of Nitric Oxide in Protection from Bordetella pertussis Respiratory Challenge
下载免费PDF全文
![点击此处可从《Infection and immunity》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The mechanism whereby whole-cell pertussis vaccines (WCV) confer protection against Bordetella pertussis is still not fully understood. We have previously reported that macrophage activation produced by vaccination with WCV is associated with induction of NO synthesis by macrophages in response to in vitro stimulation with B. pertussis antigens. To determine whether NO production is an effector of protection or simply a marker of activation, the susceptibility of inducible nitric oxide synthase (type II, iNOS) knockout mice to infection with B. pertussis was examined. We showed that iNOS knockout mice were more susceptible to B. pertussis respiratory challenge than wild-type mice. iNOS-deficient mice also developed a less effective protective response than wild-type mice after the same immunization with WCV. This suggests that NO plays an important role in effecting protection against B. pertussis challenge. 相似文献
104.
105.
C W Tabor H Tabor Q W Xie 《Proceedings of the National Academy of Sciences of the United States of America》1986,83(16):6040-6044
We have obtained Escherichia coli mutants lacking spermidine synthase (putrescine aminopropyltransferase) and have found that the mutated gene (speE) is located immediately upstream from the gene coding for S-adenosylmethionine decarboxylase (speD); these genes are located at 2.7 minutes on the E. coli chromosome. Both genes are present in a 1795-base-pair fragment of E. coli DNA that was cloned into pBR322. Deletion of 105 bases upstream of speE caused a coordinate loss of both activities, indicating that speE and speD constitute a single operon. speE and speD have also been cloned separately in a high-expression vector; strains carrying these plasmids overproduce the respective enzymes. 相似文献
106.
107.
The possible reversal by calcium of the inhibitory action of verapamil on the atrioventricular (AV) node was investigated in anesthetized, atropinized dogs, with cardiac pacing. The His bundle potentials were recorded by endocavitory electrode and the AV node effective refractory period measured by the extrastimulus method. Calcium infusion was effective against the impairment of AV nodal conduction induced by verapamil, provided it remained moderate: the gradual rise in the plasma calcium concentration counteracted the effects of an infusion of verapamil on conduction time and effective refractory period in the AV node, as long as it did not exceed 5 mmol/L. However, beyond this level, calcium appeared less and less capable of reversing the effects of verapamil. Thus, the protective action of calcium had a bell-shaped dose-response curve, with the optimum at 5 mmol/L. This biphasic influence is consistent with the opposite opinions previously given concerning the antagonism between calcium and calcium blockers, depending on whether hypercalcemia brought into play was mild or major. In any case, the prominent role played by calcium in the slow inward current in the AV node accounts for the antagonism, observed in vivo, between calcium and verapamil. The pacemaker activity of the sinoatrial (SA) node was less influenced by both calcium blocker and calcium. 相似文献
108.
Previous studies have demonstrated that the ability of the in vitro whole bladder to empty in response to bethanechol administration was inhibited by anoxia while its ability to generate pressure decreased only slightly. One question was not addressed by these early studies: Is the anoxic effect selective for receptor-mediated contractile stimulation (as opposed to non-receptor-mediated contractile stimulation)? The present study was designed to compare the effect of anoxia on the ability of the in vitro bladder to generate pressure, sustain pressure, and empty in response to field stimulation (FS), bethanechol and KC1 administration. Each New Zealand white rabbit was anesthetized with pentobarbital and the bladder removed. The bladder was mounted as a whole-bladder preparation in a 300-ml isolated bath containing Tyrode's solution at 37 degrees C and equilibrated with 95% O2, 5% CO2. Anoxia was produced by changing the gas mixture to 95% nitrogen, 5% CO2. The effect of anoxia on the response to FS, bethanechol, and KCl was determined at different times after the initiation of anoxia. The results of these studies can be summarized as follows. (1) Anoxia induced a time-dependent decrease in the rate of pressure generation, the magnitude of pressure generation, and the percent volume emptied in response to FS and bethanechol. (2) At all time periods of anoxia, the ability of the bladder to empty was inhibited to a significantly greater degree than either the rate of magnitude of pressure generation (for both FS and bethanechol administration).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
109.
110.
持续静脉滴注安定治疗频繁发作的小儿癫痫 总被引:3,自引:0,他引:3
目的探讨持续静脉滴注安定法治疗频繁发作小儿癫痫的疗效.方法对28例频繁发作癫痫的患儿,采用安定持续静脉滴注,按发作情况调整滴注速度,比较治疗前后的发作频率;应用荧光偏振免疫法测定血安定浓度.结果持续静脉滴注安定治疗后每日发作次数较治疗前明显减少(P<0.01).血安定浓度的安全有效范围为574.50±291.57μg/ml.安定静脉滴注速度与血药浓度呈正相关(γ=0.941,P<0.01).结论持续静脉滴注安定是一种安全有效的控制小儿频繁发作癫痫的辅助治疗方法. 相似文献