全文获取类型
收费全文 | 3759篇 |
免费 | 236篇 |
国内免费 | 123篇 |
专业分类
耳鼻咽喉 | 6篇 |
儿科学 | 67篇 |
妇产科学 | 52篇 |
基础医学 | 424篇 |
口腔科学 | 39篇 |
临床医学 | 273篇 |
内科学 | 730篇 |
皮肤病学 | 44篇 |
神经病学 | 217篇 |
特种医学 | 19篇 |
外国民族医学 | 1篇 |
外科学 | 215篇 |
综合类 | 362篇 |
现状与发展 | 1篇 |
预防医学 | 234篇 |
眼科学 | 74篇 |
药学 | 942篇 |
1篇 | |
中国医学 | 134篇 |
肿瘤学 | 283篇 |
出版年
2024年 | 3篇 |
2023年 | 23篇 |
2022年 | 46篇 |
2021年 | 79篇 |
2020年 | 68篇 |
2019年 | 75篇 |
2018年 | 68篇 |
2017年 | 85篇 |
2016年 | 119篇 |
2015年 | 99篇 |
2014年 | 203篇 |
2013年 | 323篇 |
2012年 | 236篇 |
2011年 | 248篇 |
2010年 | 201篇 |
2009年 | 188篇 |
2008年 | 230篇 |
2007年 | 207篇 |
2006年 | 207篇 |
2005年 | 176篇 |
2004年 | 162篇 |
2003年 | 148篇 |
2002年 | 98篇 |
2001年 | 83篇 |
2000年 | 60篇 |
1999年 | 65篇 |
1998年 | 59篇 |
1997年 | 51篇 |
1996年 | 41篇 |
1995年 | 39篇 |
1994年 | 34篇 |
1993年 | 53篇 |
1992年 | 27篇 |
1991年 | 33篇 |
1990年 | 40篇 |
1989年 | 30篇 |
1988年 | 27篇 |
1987年 | 25篇 |
1986年 | 17篇 |
1985年 | 32篇 |
1984年 | 25篇 |
1983年 | 19篇 |
1982年 | 13篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1978年 | 9篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1975年 | 4篇 |
排序方式: 共有4118条查询结果,搜索用时 15 毫秒
101.
Several molecular epidemiological studies have been conducted to examine the association between methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and male infertility susceptibility, but the results remain inconclusive. To derive a more precise estimation of the relationship, a meta-analysis was performed. In this meta-analysis, a total of 26 case–control studies including 5659 infertility cases and 5528 controls were selected to evaluate the possible association. The pooled odds ratios (ORs) with 95% confidence intervals (95% CIs) were used to assess the strength of association of C677T polymorphism with male infertility in the additive model, dominant model, recessive model and allele-frequency genetic model. In the overall analysis, the frequency of the 677T allele was significantly associated with male infertility susceptibility (OR?=?2.32, 95%CI?=?2.04–2.65 for TT vs. CC genotype; OR?=?1.09, 95%CI?=?1.00–1.19 for CT vs. CC genotype; OR?=?1.19, 95%CI?=?1.10–1.29 for CT/TT vs. CC genotype; OR?=?1.54, 95%CI?=?1.36–1.74 for TT vs. CC/TT genotype; OR?=?1.22, 95%CI?=?1.15–1.30 for T vs. C allele). A subgroup analysis of the subjects showed that significantly strong association between MTHFR C677T polymorphism and male infertility was present only in Asians, but not in Caucasians. Additionally, MTHFR C677T was associated with a significant increase in the risk of azoospermia in all genetic models. Meanwhile, no significantly increased risks of oligoasthenotertozoospermia (OAT) were found in most of the genetic models. In conclusion, this meta-analysis is in favor that the MTHFR C677T polymorphism is capable of causing male infertility susceptibility, especially in Asians and the subgroup of azoospermia. 相似文献
102.
ATM,THMS, and RRM1 protein expression in nasopharyngeal carcinomas treated with curative intent 下载免费PDF全文
Jenny Jaeeun Ko MD FRCPC Alexander C. Klimowicz PhD Amanda Jagdis MD Tien Phan MD FRCPC Janessa Laskin MD FRCPC Harold Y. Lau MD FRCPC Jodi E. Siever MSc Stephanie K. Petrillo MSc Thomas A. Thomson MD FRCPC M. Sarah Rose PhD Gwyn Bebb MBMCh PhD FRCPC Anthony M. Magliocco MD FRCPC FCAP Desirée Hao MD FRCPC 《Head & neck》2016,38(Z1):E384-E391
103.
Lankin VZ Ivanova MV Konovalova GG Tikhaze AK Kaminnyi AI Kukharchuk VV 《Bulletin of experimental biology and medicine》2007,143(4):414-417
We studied the effects of two inhibitors of β-hydroxy-β-methylglutaryl coenzyme A reductase, simvastatin and lovastatin, on
the lag phase of ascorbate-dependent lipid oxidation in rat liver. Oxidizability of liver biological membranes significantly
increased in intact animals and rats with induced hypercholesterolemia after peroral administration of these statins. The
lag phase of ascorbate-dependent lipid oxidation in liver biomembranes decreased by 2.1 times in hypercholesterolemic rats.
In animals of the lovastatin group this parameter decreased by 4.4 times compared to the control. In intact rats receiving
simvastatin, the lag phase of oxidation in biomembranes from the liver decreased practically by 2 times. At the same time,
in animals receiving simvastatin in combination with antioxidant vitamins (vitamins E and C, provitamin A) and selenium, the
period of induction of oxidation increased by 3.3 times. Our results indicate that β-hydroxy-β-methylglutaryl coenzyme A reductase
inhibitors produce a prooxidant effect on the liver, which can be prevented by administration of antioxidant agents.
__________
Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 143, No. 4, pp. 390–393, April, 2007 相似文献
104.
Chepurnenko SA 《Bulletin of experimental biology and medicine》2007,143(5):585-586
An imbalance in the first line of the antioxidant defence and hyperactivity of the glutathione-dependent system were revealed
in 137 youths with mitral valve prolapse. Increased activities of superoxide dismutase and glutathione reductase (by 6 and
1.82–2.10 times, respectively) can serve as an additional diagnostic criterion of decreased compensatory reserves in patients
with mitral valve prolapse.
__________
Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 143, No. 5, pp. 519–521, May, 2007 相似文献
105.
Lakomkin VL Kapel'ko VI Lankin VZ Konovalova GG Kaminnyi AI 《Bulletin of experimental biology and medicine》2007,143(4):408-410
Long-term administration of β-hydroxy-β-methylglutaryl coenzyme A reductase inhibitor atorvastatin to rats was accompanied
by an increase in the relative weight of the heart and decrease in the rate of pressure development in the isovolumic heart.
During oxidative stress induced by addition of 100 μM H2O2 to the perfusate, the decrease in contractile function was more pronounced that in the control. Our results indicate that
administration of atorvastatin is accompanied by a decrease in myocardial contractility, which becomes more pronounced under
conditions of oxidative stress.
__________
Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 143, No. 4, pp. 383–385, April, 2007 相似文献
106.
107.
Nitrite reductase in Streptoccocus mutans plays a critical role in the survival of this pathogen in oral cavity 总被引:1,自引:0,他引:1
BACKGROUND/AIMS: The mechanisms of nitric oxide (NO) production by bacteria in the oral cavity are still not clearly defined but salivary streptococci have been reported to generate NO. The aim of this study was to clarify the mechanism of nitrite metabolism and generation of NO by Streptococcus mutans, a major pathogen of dental caries. METHODS: We searched the genomic database of oral pathogens for nitrite reductase and used a polymerase chain reaction (PCR) to clone the nirJ gene from S. mutans GS5. His-tagged recombinant NirJ protein was expressed in Escherichia coli BL21 and characterized. We constructed a nirJ gene-disrupted mutant strain of S. mutans (DeltanirJ) to analyze the physiological significance of nirJ. RESULTS: S. mutans generates NO from nitrite, probably as a result of the possession of nitrite reductase. We cloned the nirJ gene from S. mutans GS5 by PCR. The recombinant NirJ protein catalyzed the reduction of nitrite with a K(m) value of 3.37 microM and a specific activity of 2.5 micromol/min/mg of protein at 37 degrees C. Biochemical analysis revealed that the nitrite-reducing activity of the mutant (DeltanirJ) strain was significantly lower than that of the wild-type strain. The growth of the mutant strain, but not of the wild-type strain, was strongly suppressed by the presence of physiological levels of nitrite ( approximately 0.2 mM) in saliva. CONCLUSION: These observations suggest that the elimination of nitrite and/or the generation of NO are important for the survival of S. mutans in the oral cavity. 相似文献
108.
Manaf AlMatar Essam A. Makky Işıl Var Begüm Kayar Fatih Köksal 《Pharmacological reports : PR》2018,70(2):217-226
Tuberculosis (TB) is described as lethal disease in the world. Resistant to TB drugs is the main reason to have unfavourable outcomes in the treatment of TB. Therefore, new agents to replace existing drugs are urgently needed. Previous reports suggested that InhA inhibitors, an enoyl-ACP-reductase, might provide auspicious candidates which can be developed into novel antitubercular agents. In this review, we explain the role of InhA in the resistance of isoniazid. Furthermore, five classes of InhA inhibitors, which display novel binding modes and deliver evidence of their prosperous target engagement, have been debated. 相似文献
109.
糖尿病性角膜病变(diabetic keratopathy,DK)是糖尿病在眼部的常见并发症之一,其主要临床表现包括干眼症、点状角膜炎、角膜上皮再生迟缓、反复的上皮糜烂、角膜知觉减退和角膜水肿等,主要发病机制为糖基化反应、多元醇通路和蛋白酶改变等。本文就糖尿病角膜病变的主要临床表现相对应的发病机制进行综述,以期对临床治疗提供新思路。 相似文献
110.
NRH:quinone reductase (QR2) is present in the retinas of embryonic and post-hatched (PH) chicks. 5-Methoxycarbonylamino-N-acetyltryptamine (5-MCA-NAT) is a QR2 ligand that increases cAMP levels in developing retinas, but it does not affect cAMP levels in CHO-QR2 cells. The dopamine quinone reductase activity of QR2 retrieves dopamine, which increases cAMP levels in developing retinas. The objective of the present study was to investigate whether 5-MCA-NAT increases endogenous dopamine levels in retinas from chick embryos and post-hatched chicks. Endogenous dopamine was measured by enzyme-linked immunosorbent assay (ELISA). 5-MCA-NAT increased retinal endogenous dopamine levels at all developmental stages studied and in PH chicks (−log EC50 = 11.62 ± 0.34 M). This effect was inhibited by non-selective antagonists of receptors and melatonin binding sites N-acetyl-2-benzyltryptamine (luzindole, 5 μM), but it was not inhibited by the Mel1b melatonin receptor antagonist 4-phenyl-2-propionamidotetralin (4-P-PDOT, 10 nM). The QR2 cosubstrate, N-methyl-dihydronicotinamide (NMH) (−log EC50 = 6.74 ± 0.26 M), increased endogenous dopamine levels in controls and in retinas stimulated with 5-MCA-NAT (3 nM). The QR2 inhibitor benzo[e]pyrene inhibited endogenous dopamine levels in both control (−log IC50 = 7.4 ± 0.28 M) and NMH-stimulated (at 100 nM and 1 μM benzo[e]pyrene concentrations) retinas. Theoretical studies using Molegro Virtual Docking software corroborated these experimental results. We conclude that 5-MCA-NAT increases the level of endogenous dopamine via QR2. We suggest that this enzyme triggers double reduction of the dopamine quinone, recovering dopamine in retinal development. 相似文献