全文获取类型
收费全文 | 324354篇 |
免费 | 29094篇 |
国内免费 | 22887篇 |
专业分类
耳鼻咽喉 | 2987篇 |
儿科学 | 3424篇 |
妇产科学 | 4926篇 |
基础医学 | 39918篇 |
口腔科学 | 5496篇 |
临床医学 | 45273篇 |
内科学 | 49725篇 |
皮肤病学 | 3082篇 |
神经病学 | 18371篇 |
特种医学 | 11985篇 |
外国民族医学 | 213篇 |
外科学 | 33238篇 |
综合类 | 49911篇 |
现状与发展 | 76篇 |
一般理论 | 20篇 |
预防医学 | 19635篇 |
眼科学 | 9598篇 |
药学 | 32820篇 |
334篇 | |
中国医学 | 17434篇 |
肿瘤学 | 27869篇 |
出版年
2024年 | 1001篇 |
2023年 | 5023篇 |
2022年 | 13068篇 |
2021年 | 16352篇 |
2020年 | 12054篇 |
2019年 | 10837篇 |
2018年 | 11426篇 |
2017年 | 9933篇 |
2016年 | 9361篇 |
2015年 | 14363篇 |
2014年 | 17809篇 |
2013年 | 15351篇 |
2012年 | 22820篇 |
2011年 | 25815篇 |
2010年 | 15914篇 |
2009年 | 12256篇 |
2008年 | 17025篇 |
2007年 | 17023篇 |
2006年 | 17059篇 |
2005年 | 16790篇 |
2004年 | 10672篇 |
2003年 | 9765篇 |
2002年 | 8448篇 |
2001年 | 7472篇 |
2000年 | 8285篇 |
1999年 | 9022篇 |
1998年 | 5480篇 |
1997年 | 5501篇 |
1996年 | 4335篇 |
1995年 | 3924篇 |
1994年 | 3215篇 |
1993年 | 2098篇 |
1992年 | 2828篇 |
1991年 | 2419篇 |
1990年 | 2117篇 |
1989年 | 1862篇 |
1988年 | 1564篇 |
1987年 | 1352篇 |
1986年 | 1107篇 |
1985年 | 912篇 |
1984年 | 527篇 |
1983年 | 373篇 |
1982年 | 242篇 |
1981年 | 238篇 |
1980年 | 188篇 |
1979年 | 221篇 |
1978年 | 82篇 |
1977年 | 89篇 |
1974年 | 102篇 |
1973年 | 83篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
881.
Transitional mucosa adjacent to colorectal cancers is essentially characterized by an excess of sialomucins at the expense of the normally predominant sulphomucins in epithelial cells lining the intestinal crypts which presents the early stage of oncogenic transformation of colorectal epithelium. The presence or absence of sialomucins at the resection margins was studied histochemically using the high iron diamine-alcian blue(HID-AB) stain in 64 rectal cancer patients in Dukes' B stage who underwent curative anterior resection. The correlation was revealed between the presence of sialomucins at the resection margins and subsequent development of local tumour recurrence. Fourteen of 27 patients (51.9%) with sialomucins predominant pattern at either resection margin developed local recurrence compared with 4 of 37 patients (10.8%) with sulphomucins predominant pattern (P less than 0.001). It is suggested that determination of the transitional mucosa around anastomosis in patients treated for the rectal carcinoma by anterior resection appears to identify those with a higher risk of local recurrence. 相似文献
882.
The effects of combined use of earthworm extract(912)and HpD-laser on the produc-tion of reactive oxygen and the biosynthesis of DNA in S_(180) tumor cells were studied throughchemiluminescence measurement and[~3H]-TdR incorporation assay.The results showed that as com-pared with the control,the intensity of chemiluminescence emitted by tumor cells treatedsimultaneously with 912 and HpD-laser was enhanced more than ten-folds,while that treated with912 or HpD-laser alone was increased only 2~4 folds.The[~3H]-TdR incorporation into tumorcells of the former group was inhibited upto 74.1%,and that of the latter groups decreased onlyby 42.2% and 40.0%,respectively.In accordance with these biochemical changes,the ultrastructuraldamage of tumor cells of the former,combinedly treated group appeared to be the most serious.This suggests an additive effect of 912 with HpD-laser on tumor cells.In addition,if free radicalscavengers,such as catalase and superoxide dismutase,were added to the reaction systembefore chemiluminescence assay,the luminescent enhancement effect mentioned above was dramaticallyalleviated,implying the presence of O_2~ and H_2O_2 in the system.Therefore,as to the toxic effecton tumor cells,912 and HpD-laser are not only additive in efficiency,but also similar in theunderlying mechanism of action. 相似文献
883.
采用大鼠30%Ⅲ度烫伤模型,应用光镜、电镜、3β-羟甾脱氢酶(3β-HSD)组织化学染色及其相对活性的测定和血清睾酮及黄体生成素(LH)浓度的检测,分不同时相对严重烫伤后30天内大鼠睾丸间质细胞的改变进行了动态观察。结果表明,烫伤后睾丸间质细胞有不同程度的变性、坏死;间质细胞内3β-HSD活性迅速降低,伤后30天仍保持较低水平;血清睾酮水平迅速下降,并持续维持较低水平,伤后30天仍不回升,而血清LH浓度无明显改变。提示烫伤后血清睾酮下降的机理可能与睾丸间质细胞的受损及糖皮质激素升高有关。 相似文献
884.
Two phospholipase A2 (PLA2) enzymes, TMVPLA2 I and TMVPLA2 II, isolated from Trimeresurus mucrosquamatus venom induced rat hind-paw oedema. Recovered myeloperoxidase activity increased within 1 h and was greatly elevated in the rat paw 3-6 h after subplantar injection of these venom PLA2 enzymes. Methotrexate pretreatment significantly reduced not only the peripheral leucocyte count but also venom PLA2-induced paw oedema. In rat isolated PMN leucocyte suspension, venom PLA2 induced superoxide radical formation. Paw swelling caused by TMVPLA2 I or TMVPLA2 II was only slightly or not, respectively, reduced in the rats pretreated with anti-platelet plasma, which reduced peripheral blood platelet count by greater than 96%, suggesting platelets are not involved. In isolated platelet preparation, TMVPLA2 I induced platelet activation in a concentration-dependent manner, while TMVPLA2 II had no effect. Pretreatment with diphenhydramine/methysergide greatly suppressed the oedematous responses caused by the two venom PLA2 enzymes; the residual responses were significantly further depressed by aspirin. The oedematous responses caused by the enzymes were also suppressed by FPL 55712, BW 755C, dexamethasone, superoxide dismutase/catalase, isoprenaline and terbutaline. However, BN 52021 and L 652731, both platelet aggregating factor antagonists, were not effective on these responses. Thus, in addition to histamine and 5-hydroxytryptamine release by the mast cells in PLA2-induced paw oedema (Wang & Teng 1990), the results of this study indicate minor, but significant, roles for neutrophils and inflammatory mediators including prostaglandins, leukotrienes and superoxide radicals. 相似文献
885.
丙型肝炎患者外周血单核细胞中丙型肝炎病毒复制的研究 总被引:2,自引:0,他引:2
9例临床诊断为丙型肝炎患者,研究其外周血单核细胞中HCVRNA的存在及复制。9例患者血清标本抗-HCV及HCVRNA均为阳性,采用高敏感的逆转录一套式PCR法测定其外周血单核细胞中HCV正、负链RNA,结果9例患者外周血单核细胞中7例HCV正链RNA阳性,3例HCV负链RNA阳性,证实部分丙肝患者外周血单核细胞中存在HCV的复制,表明肝细胞并非为HCV感染与复制的唯一场所。 相似文献
886.
The mechanisms by which adreno-corticoid hormones regulate Na+,K(+)-ATPase in adult kidney were studied in adrenalectomized (Adx) rats. Five days after adrenalectomy, Na+,K(+)-ATPase activity was significantly reduced in the renal cortex homogenate (C = 13.0 +/- 0.8 vs. Adx = 7.1 +/- 0.7 mumol Pi mg-1 protein h-1) and in renal microsomes (C = 30.3 +/- 1.9 vs Adx = 14.6 +/- 1.3 mumol Pi mg-1 protein h-1). Glucocorticoid replacement treatment of adrenalectomized rats with betamethasone (20 micrograms kg-1 body wt twice daily for 5 days) effectively counteracted the observed reduction in Na+,K(+)-ATPase activity. In cortical homogenate the protein level of alpha 1 and beta 1 subunits measured in immunoblots was not significantly different in Adx and control rats, indicating that 5 days after adrenalectomy the alpha 1 and beta 1 subunits were present in renal cortical cells to almost normal extent but could not be assembled into a transmembrane functional unit. In support of this conclusion we found that the protein level of both the alpha 1 and beta 1 subunits was significantly lower (P less than 0.001 for both subunits) in microsomes from Adx than in control rats. The mRNA abundance for alpha 1 and beta 1 subunits were not lower in Adx as compared to control rats 1 and 5 days after surgery. However, if Adx rats were given a single dose of betamethasone (600 micrograms kg-1 body wt), a significant 2-fold increase in both alpha 1 and beta 1 mRNAs was observed (P less than 0.05 for both subunits).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
887.
本文用30例成人尸体观察了动脉韧带和左喉返神经,动脉韧带长1.2.97±4.53mm,圆索状动脉韧带23例(77%),直径为3.92±1.12mm。动脉韧带的主动脉端附着于主动脉弓(80%)或降主动脉(20%),肺动脉端附着于左肺动脉,6例肺动脉端位于心包内。19例(63%)左喉返神经绕主动脉弓,11例(37%)绕动脉韧带的主动脉端。 相似文献
888.
889.
890.