全文获取类型
收费全文 | 3871篇 |
免费 | 193篇 |
国内免费 | 111篇 |
专业分类
耳鼻咽喉 | 8篇 |
儿科学 | 60篇 |
妇产科学 | 9篇 |
基础医学 | 376篇 |
口腔科学 | 117篇 |
临床医学 | 215篇 |
内科学 | 708篇 |
皮肤病学 | 85篇 |
神经病学 | 151篇 |
特种医学 | 46篇 |
外科学 | 134篇 |
综合类 | 391篇 |
预防医学 | 596篇 |
眼科学 | 31篇 |
药学 | 935篇 |
1篇 | |
中国医学 | 253篇 |
肿瘤学 | 59篇 |
出版年
2024年 | 12篇 |
2023年 | 25篇 |
2022年 | 90篇 |
2021年 | 174篇 |
2020年 | 103篇 |
2019年 | 110篇 |
2018年 | 82篇 |
2017年 | 83篇 |
2016年 | 88篇 |
2015年 | 102篇 |
2014年 | 213篇 |
2013年 | 278篇 |
2012年 | 249篇 |
2011年 | 271篇 |
2010年 | 170篇 |
2009年 | 163篇 |
2008年 | 155篇 |
2007年 | 161篇 |
2006年 | 155篇 |
2005年 | 137篇 |
2004年 | 124篇 |
2003年 | 121篇 |
2002年 | 101篇 |
2001年 | 72篇 |
2000年 | 59篇 |
1999年 | 69篇 |
1998年 | 51篇 |
1997年 | 47篇 |
1996年 | 57篇 |
1995年 | 41篇 |
1994年 | 35篇 |
1993年 | 24篇 |
1992年 | 46篇 |
1991年 | 26篇 |
1990年 | 32篇 |
1989年 | 25篇 |
1988年 | 36篇 |
1987年 | 22篇 |
1986年 | 18篇 |
1985年 | 57篇 |
1984年 | 55篇 |
1983年 | 53篇 |
1982年 | 51篇 |
1981年 | 34篇 |
1980年 | 24篇 |
1979年 | 15篇 |
1978年 | 16篇 |
1977年 | 8篇 |
1975年 | 9篇 |
1974年 | 7篇 |
排序方式: 共有4175条查询结果,搜索用时 15 毫秒
1.
BackgroundThis study sought to determine trends in out-patient visits for gastrointestinal cancer (GC) at a quaternary hospital in KwaZulu-Natal (KZN), South Africa; and identify geographical regions which contribute most to GC-related out-patient clinic utilization at this hospital.MethodData for GC-related outpatient visits over an 11-year period was obtained from the hospital''s administrative database. Trends were analyzed using simple regression and trend line analyses. Patient residential postal codes from the administrative database were used to determine the geospatial distribution of complex GC in KZN.ResultsStrong increasing trends in GC-related out-patient visits were noted for age >65 years old (R2=0.8014), male (R2=0.7020), female (R2=0.7292), lower GC (R2=0.7094), and rural residence (R2=0.7008). Moderate increasing trends in GC-related out-patient visits were noted for age ≤65 years old (R2=0.6556), upper GC (R2=0.6498), and urban residence (R2=0.6988). The magnitude at which the number of out-patient visits increased was greater for urban residence when compared with rural residence (p=0.006). Urban centers and some regions along the North and South coast of KZN contributed the most toward GC-related out-patient visits.ConclusionOut-patient visits for complex GC in KZN are increasing. Several regions have been identified for anti-cancer interventions and decentralized out-patient services. 相似文献
2.
《Vaccine》2020,38(39):6141-6152
Influenza vaccination is considered the most valuable means to prevent and control seasonal influenza infections, which causes various clinical symptoms, ranging from mild cough and fever to even death. Among various influenza vaccine types, the inactivated subunit type is known to provide improved safety with reduced reactogenicity. However, there are some drawbacks associated with inactivated subunit type vaccines, with the main ones being its low immunogenicity and the induction of Th2-biased immune responses. In this study, we investigated the role of a single-stranded RNA (ssRNA) derived from the intergenic region in the internal ribosome entry site of the Cricket paralysis virus as an adjuvant rather than the universal vaccine for a seasonal inactivated subunit influenza vaccine. The ssRNA adjuvant stimulated not only well-balanced cellular (indicated by IgG2a, IFN-γ, IL-2, and TNF-α) and humoral (indicated by IgG1 and IL-4) immune responses but also a mucosal immune response (indicated by IgA), a key protector against respiratory virus infections. It also increases the HI titer, the surrogate marker of influenza vaccine efficacy. Furthermore, ssRNA adjuvant confers cross-protective immune responses against heterologous influenza virus infection while promoting enhanced viral clearance. Moreover, ssRNA adjuvant increases the number of memory CD4+ and CD8+ T cells, which can be expected to induce long-term immune responses. Therefore, this ssRNA-adjuvanted seasonal inactivated subunit influenza vaccine might be the best influenza vaccine generating robust humoral and cellular immune responses and conferring cross-protective and long-term immunity. 相似文献
3.
采用快速粘度分析仪(RVA)研究了食盐对18种普通玉米杂交种淀粉糊化性质的影响。结果表明:食盐显著降低了所有普通玉米杂交种淀粉的峰值、破损值和回生值;提高了谷值、终粘度、出峰时间和成糊温度。但对不同的普通玉米杂交种淀粉的糊化性质的影响程度有显著差别。随着食盐溶液质量分数的增加,普通玉米杂交种淀粉的谷值、终粘度、出峰时间和成糊温度也逐渐增加,破损值和回生值则显著降低,峰值受食盐溶液质量分数的影响很小。 相似文献
4.
Despite the use of gold complexes in modern medicine for over 100 years and the use of gold complexes in the management of
rheumatoid disease for more than 60 years, the definitive mechanisms of action for efficacy and for toxicity have not been
established.
Gold is a group 1b metal in the periodic table with several oxidation states but it is only Au(I) which is active in the biological
milieu. Gold sodium thiomalate is not only a polymeric structure, but also has the chiral ligand, thiomalic acid. Gold sodium
thiomalate thus can exist in several different physical states which may have different biological activity. In addition the
pharmacokinetic profile of gold complexes has been of little value in the understanding of either the mechanism of action,
efficacy or toxicity for both the injectable and the oral gold complexes. Many authors have misinterpreted research data on
the activities of gold complexes because they compared gold complexes of different structures, and gold complexes which exist
at different pH.
Experimental work in our laboratory has identified that gold sodium thiomalate is a mixture and can exist as either a yellow
or a colourless solution. These have some similar but several different biological activities.
Many factors contribute to the lack of understanding of the action of gold complexes. Some of these factors are related to
the wide variation in physical structure and biological activities exhibited by these compounds. 相似文献
5.
E. Perucca R. Grimaldi G. Ruberto C. Gelmi F. Trimarchi A. Crema 《European journal of clinical pharmacology》1986,29(6):729-730
Summary The kinetics of phenobarbital (PB) was compared after oral administration of equivalent doses of the drug as the acid or the propylhexedrine salt (barbexaclone) to 7 normal volunteers. The absorption and elimination parameters were very similar. It was concluded that propylhexedrine did not affect the serum kinetics of PB given as barbexaclone. 相似文献
6.
WEIGUANG ZENG PIERRE-OLIVIER REGAMEY KEITH ROSE YUZHOU WANG ERNST BAYER 《Chemical biology & drug design》1997,49(3):273-279
The use of N, O-bisFmoc-N-(2-hydroxy-4-methoxybenzyl) amino acid derivatives in the synthesis of peptides with difficult sequences has already been described. With these amino acid derivatives the reversible protecting group 2-hydroxy-4-methoxybenzyl (Hmb) for the backbone amide bonds of peptide chains is introduced, and thus the aggregation due to hydrogen-bond interchain association is inhibited. This paper describes the synthesis and use of Fmoc-N-(2-hydroxy-4-methoxybenzyl)amino acid derivatives as an alternative means of introducing Hmb backbone protection. These new monoFmoc derivatives were obtained in higher yield than the bisFmoc derivatives. Coupling yields to the amino peptide resin were the same as those obtained with bisFmoc derivatives, under the TBTU/HOBt/DIEA conditions. We also compared different syntheses of a difficult peptide with the Fmoc approach [triple coupling, capping, use of chaotropic agents, backbone protection using monoFmoc (Hmb)Ala] and with optimized Boc chemistry. Both the backbone protection and optimized Boc chemistry approaches gave the desired product in excellent yield and purity. © Munksgaard 1997. 相似文献
7.
8.
僵蚕抗凝活性及其成分的分析 总被引:7,自引:1,他引:6
目的对僵蚕不同部位抗凝活性及其主要成分的含量进行测定 ,为僵蚕的质量控制和用药提供依据。方法用凝血酶时间 (TT)和经典化学方法为指标测定生、制僵蚕以及制僵蚕的不同部位的抗凝血活性大小以及总氮、铵态氮、蛋白质和草酸铵的含量。结果制僵蚕的抗凝活性、蛋白质和草酸铵含量均大于生僵蚕。制僵蚕不同部位凝血酶时间和蛋白质含量比较 ,其顺序是 :透明胶状物 >全药 >僵蚕皮 >绿褐色物。结论生、制僵蚕以及僵蚕不同部位抗凝活性和蛋白质等成分含量不一致 ,建议根据用药目的选择生、制僵蚕 ,作为抗凝药物应用时 ,可选择制僵蚕或其某一个或几个部位 相似文献
9.
采用正交试验优选出最佳条件为:当乙酰乙酸乙酯为0.2moL时,硫酸铁铵0.7g,环乙烷10mL。乙酰乙酸乙酯和惭二醇摩尔比为1:1.5,反应时间为5h。所得产率为59.2%。 相似文献
10.