全文获取类型
收费全文 | 6962篇 |
免费 | 579篇 |
国内免费 | 572篇 |
出版年
2024年 | 17篇 |
2023年 | 113篇 |
2022年 | 222篇 |
2021年 | 399篇 |
2020年 | 269篇 |
2019年 | 316篇 |
2018年 | 307篇 |
2017年 | 188篇 |
2016年 | 316篇 |
2015年 | 449篇 |
2014年 | 497篇 |
2013年 | 505篇 |
2012年 | 623篇 |
2011年 | 593篇 |
2010年 | 322篇 |
2009年 | 315篇 |
2008年 | 378篇 |
2007年 | 310篇 |
2006年 | 271篇 |
2005年 | 216篇 |
2004年 | 200篇 |
2003年 | 194篇 |
2002年 | 177篇 |
2001年 | 109篇 |
2000年 | 107篇 |
1999年 | 86篇 |
1998年 | 41篇 |
1997年 | 58篇 |
1996年 | 70篇 |
1995年 | 34篇 |
1994年 | 42篇 |
1993年 | 32篇 |
1992年 | 52篇 |
1991年 | 38篇 |
1990年 | 27篇 |
1989年 | 28篇 |
1988年 | 30篇 |
1987年 | 22篇 |
1986年 | 14篇 |
1985年 | 17篇 |
1984年 | 11篇 |
1983年 | 19篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1975年 | 8篇 |
1973年 | 4篇 |
排序方式: 共有8113条查询结果,搜索用时 953 毫秒
851.
852.
Passerini L Casey GJ Biggs BA Cong DT Phu LB Phuc TQ Carone M Montresor A 《PLoS neglected tropical diseases》2012,6(4):e1608
Background
Hookworm infections are significant public health issues in South-East Asia. In women of reproductive age, chronic hookworm infections cause iron deficiency anaemia, which, upon pregnancy, can lead to intrauterine growth restriction and low birth weight. Low birth weight is an important risk factor for neonatal and infant mortality and morbidity.Methodology
We investigated the association between neonatal birth weight and a 4-monthly deworming and weekly iron-folic acid supplementation program given to women of reproductive age in north-west Vietnam. The program was made available to all women of reproductive age (estimated 51,623) in two districts in Yen Bai Province for 20 months prior to commencement of birth weight data collection. Data were obtained for births at the district hospitals of the two intervention districts as well as from two control districts where women did not have access to the intervention, but had similar maternal and child health indicators and socio-economic backgrounds. The primary outcome was low birth weight.Principal Findings
The birth weights of 463 infants born in district hospitals in the intervention (168) and control districts (295) were recorded. Twenty-six months after the program was started, the prevalence of low birth weight was 3% in intervention districts compared to 7.4% in control districts (adjusted odds ratio 0.29, 95% confidence interval 0.10 to 0.81, p = 0.017). The mean birth weight was 124 g (CI 68 - 255 g, p<0.001) greater in the intervention districts compared to control districts.Conclusions/Significance
The findings of this study suggest that providing women with regular deworming and weekly iron-folic acid supplements before pregnancy is associated with a reduced prevalence of low birth weight in rural Vietnam. The impact of this health system-integrated intervention on birth outcomes should be further evaluated through a more extensive randomised-controlled trial. 相似文献853.
Mendoza EE Pocceschi MG Kong X Leeper DB Caro J Limesand KH Burd R 《Translational oncology》2012,5(3):208-216
Tumor cells grow in nutrient- and oxygen-deprived microenvironments and adapt to the suboptimal growth conditions by altering their metabolic pathways. This adaptation process commonly results in a tumor phenotype that displays a high rate of aerobic glycolysis and aggressive tumor characteristics. The glucose regulatory molecule, 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3), is a bifunctional enzyme that is central to glycolytic flux and is downstream of the metabolic stress sensor AMP-activated protein kinase (AMPK), which has been suggested to modulate glycolysis and possibly activate isoforms of PFKFB, specifically PFKFB3 expressed in tumor cells. Our results demonstrated that long-term low pH exposure induced AMPK activation, which resulted in the up-regulation of PFKFB3 and an increase in its serine residue phosphorylation. Pharmacologic activation of AMPK resulted in an increase in PFKFB3 as well as an increase in glucose consumption, whereas in contrast, inhibition of AMPK resulted in the down-regulation of PFKFB3 and decreased glycolysis. PFKFB3 overexpression in DB-1 tumor cells induced a high rate of glycolysis and inhibited oxygen consumption, confirming its role in controlling glycolytic flux. These results show that low pH is a physiological stress that can promote a glycolytic phenotype commonly associated with tumorigenesis. The implications are that the tumor microenviroment contributes to tumor growth and treatment resistance. 相似文献
854.
The mudskipper, Boleophthalmus pectinirostris (Perciformes, Gobiidae), is an amphibious gobioid fish. In this paper, the complete mitochondrial genome of B. pectinirostris was firstly determined. The mitogenome (17,111 bp) comprises 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes and 1 putative control region. 130-bp tandem repeat was identified in the control region, which was almost identical among the 10 individuals examined, and three different frequencies of the repeat unit (five, six or seven) were found among these individuals. 相似文献
855.
Yung-Nung Chiu Jared M. Sampson Xunqing Jiang Susan B. Zolla-Pazner Xiang-Peng Kong 《Journal of visualized experiments : JoVE》2012,(68)
Nucleic acid-based vaccination is a topic of growing interest, especially plasmid DNA (pDNA) encoding immunologically important antigens. After the engineered pDNA is administered to the vaccines, it is transcribed and translated into immunogen proteins that can elicit responses from the immune system. Many ways of delivering DNA vaccines have been investigated; however each delivery route has its own advantages and pitfalls. Skin tattooing is a novel technique that is safe, cost-effective, and convenient. In addition, the punctures inflicted by the needle could also serve as a potent adjuvant. Here, we a) demonstrate the intradermal delivery of plasmid DNA encoding enhanced green fluorescent protein (pCX-EGFP) in a mouse model using a tattooing device and b) confirm the effective expression of EGFP in the skin cells using confocal microscopy. 相似文献
856.
In this paper, we determined the complete mitochondrial genome of Solen strictus (Bivalvia: Solenidae). The whole mitogenome of S. strictus is 16,535?bp in length with a base composition of 21.7% A, 41.0% T, 25.6% C, and 11.7% G and contains 12 protein-coding genes (atp8 is missing), 2 ribosomal RNA genes, 22 transfer RNA genes, and a major non-coding region (MNR). Some peculiar patterns including tandem repeats and microsatellite-like elements are found in the MNR of S. strictus. 相似文献
857.
Pancreatic cancer is one of the most lethal malignancies, with a prominent desmoplastic reaction as its defining hallmark. The past several decades have seen dramatic progress in understanding of pancreatic cancer pathogenesis, including identification of precursor lesions, sequential transformation from normal pancreatic tissue to invasive pancreatic cancer and corresponding signature genetic events, and the biological impact of these events on malignant behavior. However, the currently used therapeutic strategies for epithelial tumor cells, which have exhibited potent antitumor activity in cell culture and animal models, have failed to produce significant effects in the clinic. The desmoplastic stroma surrounding pancreatic cancer cells, which accounts for about 90% of a tumor's mass, clearly is not a passive scaffold for cancer cells but an active contributor to carcinogenesis. Improved understanding of the dynamic interaction between cancer cells and the stroma will be important to designing effective therapeutic strategies for pancreatic cancer. This review focuses on the origin of stromal molecular and cellular components in pancreatic tumors, their biological effects on pancreatic cancer cells, and the orchestration of these two components. 相似文献
858.
A conserved RNA recognition motif (RRM) domain of Brassica napus FCA improves cotton fiber quality and yield by regulating cell size 总被引:2,自引:0,他引:2
Fan Sun Chuanliang Liu Chaojun Zhang Weiwei Qi Xueyan Zhang Zhixia Wu Depei Kong Qianhua Wang Haihong Shang Xiaoyin Qian Fuguang Li Jinshui Yang 《Molecular breeding : new strategies in plant improvement》2012,30(1):93-101
Cotton (Gossypium hirsutum L.) is an important crop that is used to produce both natural textile fiber and cottonseed oil. Cotton fiber is a unicellular trichome, whose length is critical to fiber quality and yield but difficult to modify. FCA was originally identified based on flowering time control in Arabidopsis. The function of the second RNA recognition motif (RRM) domain of Oryza sativa FCA in rice cell-size regulation has been previously reported, showing it to be highly conserved across dicotyledonous and monocotyledonous plants. The present study showed that the second RRM domain of Brassica napus FCA functioned in Gossypium hirsutum, leading to enlargement of multiple cell types, such as pollen, cotyledon petiole, and cotton fiber. In the resulting transgenic cotton, fiber length increased by ~10% and fiber yield per plant showed a dramatic increase, ranging from 35 to 66% greater than controls. Thus, this RRM domain may be a cell-size regulator and have great economic value in the cotton industry. 相似文献
859.
860.
Tavares J Ouaissi A Silva AM Lin PK Roy N Cordeiro-da-Silva A 《Parasitology international》2012,61(2):360-363
Bisnaphthalimidopropyl (BNIP) derivatives were recently identified as inhibitors of the Leishmania Silent Information Regulator 2 (SIR2) NAD(+)-dependent deacetylase. In this report we have for the first time, determined the potential of these compounds to treat visceral leishmaniasis using BALB/c mice chronically infected with Leishmania infantum as a model. These experiments led to the identification of BNIPdiaminooctane (BNIPDaoct) as an effective compound able to induce significant reduction of the parasite load in the spleen and in the liver. Indeed, at a dose of 1mg/kg, BNIPDaoct was more effective to treat leishmaniasis in a short course treatment (3 or 6 drug administrations) than the standard amphotericin B. Moreover, no indications of hematological toxicity were detected as evaluated by the hemoglobin, hematocrit, white and red blood cell counts, hence making BNIPDaoct a potential therapeutic agent against leishmaniasis. 相似文献