全文获取类型
收费全文 | 261881篇 |
免费 | 279254篇 |
国内免费 | 36439篇 |
专业分类
耳鼻咽喉 | 2557篇 |
儿科学 | 4421篇 |
妇产科学 | 2387篇 |
基础医学 | 90110篇 |
口腔科学 | 2896篇 |
临床医学 | 59181篇 |
内科学 | 97988篇 |
皮肤病学 | 5122篇 |
神经病学 | 23406篇 |
特种医学 | 9591篇 |
外科学 | 44761篇 |
综合类 | 51763篇 |
一般理论 | 3篇 |
预防医学 | 41880篇 |
眼科学 | 18816篇 |
药学 | 59422篇 |
3篇 | |
中国医学 | 46695篇 |
肿瘤学 | 16572篇 |
出版年
2020年 | 6071篇 |
2019年 | 13430篇 |
2018年 | 14019篇 |
2017年 | 14628篇 |
2016年 | 13259篇 |
2015年 | 13111篇 |
2014年 | 12885篇 |
2013年 | 12953篇 |
2012年 | 13142篇 |
2011年 | 14829篇 |
2010年 | 17189篇 |
2009年 | 24884篇 |
2008年 | 12822篇 |
2007年 | 9424篇 |
2006年 | 8962篇 |
2005年 | 8930篇 |
2004年 | 10966篇 |
2003年 | 10054篇 |
2002年 | 10437篇 |
2001年 | 12125篇 |
2000年 | 7708篇 |
1999年 | 12865篇 |
1998年 | 13960篇 |
1997年 | 13804篇 |
1996年 | 14875篇 |
1995年 | 15023篇 |
1994年 | 14776篇 |
1993年 | 13542篇 |
1992年 | 13181篇 |
1991年 | 12555篇 |
1990年 | 11514篇 |
1989年 | 11365篇 |
1988年 | 10890篇 |
1987年 | 10238篇 |
1986年 | 9776篇 |
1985年 | 8828篇 |
1984年 | 6768篇 |
1983年 | 6735篇 |
1982年 | 7682篇 |
1981年 | 7225篇 |
1980年 | 6866篇 |
1979年 | 6821篇 |
1978年 | 5928篇 |
1977年 | 6221篇 |
1976年 | 5808篇 |
1975年 | 5566篇 |
1974年 | 5112篇 |
1973年 | 4850篇 |
1972年 | 4844篇 |
1971年 | 4179篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
981.
982.
983.
外源性三磷酸腺苷对肾小管上皮细胞增殖的影响 总被引:2,自引:0,他引:2
观察外源性三磷酸腺苷(ATP)对肾小管上皮细胞株LLCPK1增殖的影响。方法通过测定3H-胸腺嘧啶掺入、细胞计数以及细胞内丝裂素活化蛋白激酶活性,并与表皮生长因子(EGF)的作用比较。结果发现ATP呈浓度依赖性促进细胞的DNA合成,并可使细胞计数增加,同时激活细胞内的丝裂素活化蛋白激酶,其作用与EGF相似。腺苷与ATP有类似作用,但较弱。核苷酸转运蛋白抑制剂对4-硝基苯6-硫基甙并不能抑制ATP及腺苷的作用。结论细胞外ATP可促进肾小管上皮细胞增殖,并可增强EGF的促增殖作用,这一作用可能是通过膜受体介导的细胞内丝裂素活化蛋白激酶活化而实现的 相似文献
984.
D—氨基葡萄糖盐酸盐的制备研究 总被引:14,自引:0,他引:14
从龙虾壳制备的甲壳素,经盐酸水解得D-氨基葡萄糖盐酸盐,收率>50%,纯度>98.7%。水解条件考察表明,以12mol/LHCl水解2.5~3h效果最佳。 相似文献
985.
986.
Genotype determining low catechol-O-methyltransferase activity as a risk factor for obsessive-compulsive disorder
下载免费PDF全文
![点击此处可从《Proceedings of the National Academy of Sciences of the United States of America》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Maria Karayiorgou Margaret Altemus Brandi L. Galke David Goldman Dennis L. Murphy Jurg Ott Joseph A. Gogos 《Proceedings of the National Academy of Sciences of the United States of America》1997,94(9):4572-4575
In the present study, we address the role of the gene for catechol-O-methyltransferase (COMT), a key modulator of dopaminergic and noradrenergic neurotransmission, in the genetic predisposition to obsessive-compulsive disorder (OCD). We show that a common functional allele of this gene, which results in a 3- to 4-fold reduction in enzyme activity, is significantly associated in a recessive manner with susceptibility to OCD, particularly in males. This association is further supported by psychiatric evaluation of patients who carry microdeletions encompassing the comt gene. The mechanism underlying this sex-selective association remains to be defined and may include a sexual dimorphism in COMT activity, although close linkage with a nearby disease susceptibility locus cannot be excluded at this point. 相似文献
987.
988.
989.
Immunohistochemical detection of imidazolone, a novel advanced glycation end product, in kidneys and aortas of diabetic patients. 总被引:11,自引:0,他引:11
下载免费PDF全文
![点击此处可从《The Journal of clinical investigation》网站下载免费的PDF全文](/ch/ext_images/free.gif)
T Niwa T Katsuzaki S Miyazaki T Miyazaki Y Ishizaki F Hayase N Tatemichi Y Takei 《The Journal of clinical investigation》1997,99(6):1272-1280
To investigate the role of the Maillard reaction in the pathogenesis of diabetic complications, we produced several clones of monoclonal antibodies against advanced glycation end products (AGEs) by immunizing mice with AGE-modified keyhole limpet hemocyanin, and found that one clone (AG-1) of the anti-AGE antibodies reacted specifically with imidazolones A and B, novel AGEs. Thus, the imidazolones, which are the reaction products of the guanidino group of arginine with 3-deoxyglucosone (3-DG), a reactive intermediate of the Maillard reaction, were found to be common epitopes of AGE-modified proteins produced in vitro. We determined the erythrocyte levels of imidazolone in diabetic patients using ELISA with the monoclonal anti-imidazolone antibody. The imidazolone levels in the erythrocytes of diabetic patients were found to be significantly increased as compared with those of healthy subjects. Then we studied the localization of imidazolone in the kidneys and aortas obtained from diabetic patients by immunohistochemistry using the antibody. Specific imidazolone immunoreactivity was detected in nodular lesions and expanded mesangial matrix of glomeruli, and renal arteries in an advanced stage of diabetic nephropathy, as well as in atherosclerotic lesions of aortas. This study first demonstrates the localization of imidazolone in the characteristic lesions of diabetic nephropathy and atherosclerosis. These results, taken together with a recent demonstration of increased serum 3-DG levels in diabetes, strongly suggest that imidazolone produced by 3-DG may contribute to the progression of long-term diabetic complications such as nephropathy and atherosclerosis. 相似文献
990.
Neuronal death in the central nervous system demonstrates a non-fibrin substrate for plasmin
下载免费PDF全文
![点击此处可从《Proceedings of the National Academy of Sciences of the United States of America》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Stella E. Tsirka Thomas H. Bugge Jay L. Degen Sidney Strickland 《Proceedings of the National Academy of Sciences of the United States of America》1997,94(18):9779-9781
Mice deficient for plasminogen exhibit a variety of pathologies, all of which examined to date are reversed when the animals are also made fibrin(ogen) deficient. These results suggested that the predominant, and perhaps exclusive, physiological role of plasminogen is clearance of fibrin. Plasminogen-deficient mice also display resistance to excitotoxin-induced neurodegeneration, in contrast with wild-type mice, which are sensitive. Based on the genetic interaction between plasminogen and fibrinogen, we investigated whether resistance to neuronal cell death in the plasminogen-deficient mice is dependent on fibrin(ogen). Unexpectedly, mice lacking both plasminogen and fibrinogen are resistant to neurodegeneration to levels comparable to plasminogen-deficient mice. Therefore, plasmin acts on substrates other than fibrin during experimental neuronal degeneration, and may function similarly in other pathological settings in the central nervous system. 相似文献