全文获取类型
收费全文 | 1669篇 |
免费 | 190篇 |
国内免费 | 19篇 |
专业分类
儿科学 | 91篇 |
妇产科学 | 7篇 |
基础医学 | 297篇 |
口腔科学 | 66篇 |
临床医学 | 175篇 |
内科学 | 297篇 |
皮肤病学 | 106篇 |
神经病学 | 42篇 |
特种医学 | 245篇 |
外科学 | 115篇 |
综合类 | 66篇 |
一般理论 | 1篇 |
预防医学 | 189篇 |
眼科学 | 14篇 |
药学 | 69篇 |
1篇 | |
中国医学 | 1篇 |
肿瘤学 | 96篇 |
出版年
2022年 | 4篇 |
2021年 | 14篇 |
2020年 | 14篇 |
2019年 | 15篇 |
2018年 | 26篇 |
2017年 | 14篇 |
2016年 | 15篇 |
2015年 | 36篇 |
2014年 | 36篇 |
2013年 | 58篇 |
2012年 | 52篇 |
2011年 | 42篇 |
2010年 | 70篇 |
2009年 | 61篇 |
2008年 | 52篇 |
2007年 | 63篇 |
2006年 | 48篇 |
2005年 | 51篇 |
2004年 | 50篇 |
2003年 | 49篇 |
2002年 | 44篇 |
2001年 | 45篇 |
2000年 | 28篇 |
1999年 | 56篇 |
1998年 | 97篇 |
1997年 | 88篇 |
1996年 | 70篇 |
1995年 | 63篇 |
1994年 | 41篇 |
1993年 | 53篇 |
1992年 | 25篇 |
1991年 | 40篇 |
1990年 | 21篇 |
1989年 | 50篇 |
1988年 | 50篇 |
1987年 | 34篇 |
1986年 | 30篇 |
1985年 | 29篇 |
1984年 | 17篇 |
1983年 | 19篇 |
1982年 | 21篇 |
1981年 | 27篇 |
1980年 | 25篇 |
1979年 | 11篇 |
1978年 | 27篇 |
1977年 | 20篇 |
1976年 | 15篇 |
1975年 | 14篇 |
1974年 | 5篇 |
1966年 | 4篇 |
排序方式: 共有1878条查询结果,搜索用时 0 毫秒
41.
Gonzales AJ; Christensen JG; Preston RJ; Goldsworthy TL; Tlsty TD; Fox TR 《Carcinogenesis》1998,19(7):1173-1183
42.
Identification of differentially expressed genes in aflatoxin B1- treated cultured primary rat hepatocytes and Fischer 344 rats 总被引:4,自引:1,他引:4
Harris AJ; Shaddock JG; Manjanatha MG; Lisenbey JA; Casciano DA 《Carcinogenesis》1998,19(8):1451-1458
Aflatoxin B1 (AFB1), a mutagen and hepatocarcinogen in rats and humans, is
a contaminant of the human food supply, particularly in parts of Africa and
Asia. AFB1-induced changes in gene expression may play a part in the
development of the toxic, immunosuppressive and carcinogenic properties of
this fungal metabolite. An understanding of the-role of AFB1 in modulating
gene regulation should provide insight regarding mechanisms of AFB1-induced
carcinogenesis. We used three PCR- based subtractive techniques to identify
AFB1-responsive genes in cultured primary rat hepatocyte RNA: differential
display PCR (DD-PCR), representational difference analysis (RDA) and
suppression subtractive hybridization (SSH). Each of the three techniques
identified AFB1- responsive genes, although no individual cDNA was isolated
by more than one technique. Nine cDNAs isolated using DD-PCR, RDA or SSH
were found to represent eight genes that are differentially expressed as a
result of AFB1 exposure. Genes whose mRNA levels were increased in cultured
primary rat hepatocytes after AFB1 treatment were corticosteroid binding
globulin (CBG), cytochrome P450 4F1 (CYP4F1), alpha-2 microglobulin,
C4b-binding protein (C4BP), serum amyloid A-2 and glutathione S-transferase
Yb2 (GST). Transferrin and a small CYP3A-like cDNA had reduced mRNA levels
after AFB1 exposure. Full-length CYP3A mRNA levels were increased. When
liver RNA from AFB1-treated male F344 rats was evaluated for transferrin,
CBG, GST, CYP3A and CYP4F1 expression, a decrease in transferrin mRNA and
an increase in CBG, GST, CYP3A and CYP4F1 mRNA levels was also seen.
Analysis of the potential function of these genes in maintaining cellular
homeostasis suggests that their differential expression could contribute to
the toxicity associated with AFB1 exposure.
相似文献
43.
目的研究选择性头部降温对缺血性脑损伤胎羊纹状体神经元凋亡和星形胶质细胞增殖的影响。方法胎羊于妊娠117~124d时通过双侧颈动脉阻塞30min造成双侧脑缺血损伤,损伤后将胎羊随机分为:损伤组(n=10)、2h低温组(损伤后2h开始亚低温治疗,n=7)和6h低温组(损伤后6h开始亚低温治疗,n=8),另设正常对照组(n=5)。通过冷循环水进行选择性头部降温,取脑组织用免疫组化法检测胎羊纹状体caspase-3(半胱天冬氨酸酶-3),GFAP(胶质纤维酸性蛋白)和PCNA(增殖细胞核抗原)的表达。结果①纹状体神经元凋亡:正常对照组中,caspase-3表达极少(11.00±13.77),损伤组caspase-3免疫阳性细胞为177.70±48.69,明显增加(P=0.000),损伤后2h治疗组(54.14±39.44,P=0.000)和损伤后6h治疗组(122.43±52.36,P=0.017)均能减少caspase-3免疫阳性细胞。②纹状体星形胶质细胞增殖:与正常对照组(163.40±21.98)相比,缺血性脑损伤组的GFAP免疫阳性细胞明显增多(433.25±66.69,P=0.000),损伤后2h开始亚低温治疗(219.50±35.31,P=0.000)和损伤后6h开始亚低温治疗(272.50±86.20,P=0.000)均能减少GFAP免疫阳性细胞。③纹状体PCNA阳性细胞的表达:在正常对照组中,PCNA免疫阳性细胞较少,为153.40±12.46,缺血性脑损伤组的PCNA免疫阳性细胞明显增多(353.70±45.60,P=0.000),损伤后2h开始亚低温治疗(187.14±26.26,P=0.000)和损伤后6h开始亚低温治疗(230.25±67.46,P=0.000)均能减少PCNA免疫阳性细胞。结论亚低温可以抑制纹状体神经元的凋亡和星形胶质细胞的增殖,该作用可能为选择性头部降温的脑保护作用机制之一。 相似文献
44.
45.
Diet and nutrition are increasingly recognized as likely to be major determinants of cancer, notably cancers of the gastrointestinal tract, breast, endometrium, ovary, and prostate. Dietary factors may collectively account for a greater proportion of all cancers that occur in contemporary Western society than does any other category of environmental exposure (1). With the development of knowledge of the protective properties of certain components of food, links with diet have been suggested for other cancer sites (2). The epidemiological evidence for the association of diet and cancer is, however, not uniformly convincing; also, the likely biological pathways are not always clear. In this paper, we comment on some current hypotheses in this area and examine the best epidemiological methods to test them. 相似文献
46.
47.
48.
Marsh JC; Will AJ; Hows JM; Sartori P; Darbyshire PJ; Williamson PJ; Oscier DG; Dexter TM; Testa NG 《Blood》1992,79(12):3138-3144
We have used the long-term bone marrow culture (LTBMC) system to analyze hematopoiesis in three patients with dyskeratosis congenita (DC), two of whom had aplastic anemia, and the third had a normal blood count (apart from mild macrocytosis) and normal BM cellularity. Hematopoiesis was severely defective in all three patients, as measured by a low incidence of colony-forming cells and a low level of hematopoiesis in LTBMC. The function of the marrow stroma was normal in its ability to support the growth of hematopoietic progenitors from normal marrows seeded onto them in all three cases, but the generation of hematopoietic progenitors from patients marrow cells inoculated onto normal stromas was reduced, thus suggesting the defect to be of stem cell origin. The parents and unaffected brother of one of the families have also been studied in LTBMC and all showed normal hematopoietic and stromal cell function. From this study we speculate that there are some similarities between DC and the defect in the W/Wv mouse. 相似文献
49.
Celia McMichael 《Medical anthropology》2018,37(4):294-310
Globally, 2.4 billion people lack adequate sanitation, and open defecation remains common. In this article, I present the qualitative findings from an evaluation of a water, sanitation, and hygiene intervention in remote, mid-West Nepal. The evaluation, conducted in 2014, involved villagers from eight wards in Kotgaun Village Development Committee. Drawing on the concept of the “toilet tripod,” I argue as follows: multi-scalar political will provide an important foundation for construction and sustained use of toilets, proximate social pressures contributed significantly to toilet adoption and efforts to eliminate open defecation, and water insecurity constrained improved sanitation and hygiene. 相似文献
50.
Sarvepalli Shashank Garber Ari Burke Carol A. Gupta Niyati Ibrahim Mounir McMichael John Morris-Stiff Gareth Bhatt Amit Vargo John Rizk Maged Rothberg Michael B. 《Digestive diseases and sciences》2021,66(6):2059-2068
Digestive Diseases and Sciences - Inadequate bowel preparation (IBP) is associated with reduced adenoma detection. However, limited research has examined the impact of different commercial bowel... 相似文献