全文获取类型
收费全文 | 28639篇 |
免费 | 8536篇 |
国内免费 | 173篇 |
专业分类
耳鼻咽喉 | 257篇 |
儿科学 | 809篇 |
妇产科学 | 514篇 |
基础医学 | 5451篇 |
口腔科学 | 1053篇 |
临床医学 | 4063篇 |
内科学 | 6967篇 |
皮肤病学 | 570篇 |
神经病学 | 2183篇 |
特种医学 | 1911篇 |
外科学 | 6327篇 |
综合类 | 355篇 |
一般理论 | 12篇 |
预防医学 | 3094篇 |
眼科学 | 814篇 |
药学 | 1551篇 |
4篇 | |
中国医学 | 26篇 |
肿瘤学 | 1387篇 |
出版年
2021年 | 483篇 |
2020年 | 340篇 |
2018年 | 435篇 |
2017年 | 435篇 |
2016年 | 621篇 |
2015年 | 960篇 |
2014年 | 1621篇 |
2013年 | 2257篇 |
2012年 | 934篇 |
2011年 | 815篇 |
2010年 | 1320篇 |
2009年 | 1397篇 |
2008年 | 731篇 |
2007年 | 553篇 |
2006年 | 659篇 |
2005年 | 564篇 |
2004年 | 515篇 |
2003年 | 396篇 |
2002年 | 417篇 |
2001年 | 543篇 |
2000年 | 448篇 |
1999年 | 638篇 |
1998年 | 822篇 |
1997年 | 783篇 |
1996年 | 821篇 |
1995年 | 790篇 |
1994年 | 668篇 |
1993年 | 620篇 |
1992年 | 628篇 |
1991年 | 604篇 |
1990年 | 548篇 |
1989年 | 643篇 |
1988年 | 648篇 |
1987年 | 638篇 |
1986年 | 597篇 |
1985年 | 625篇 |
1984年 | 557篇 |
1983年 | 543篇 |
1982年 | 599篇 |
1981年 | 570篇 |
1980年 | 541篇 |
1979年 | 539篇 |
1978年 | 511篇 |
1977年 | 519篇 |
1976年 | 449篇 |
1975年 | 408篇 |
1974年 | 366篇 |
1973年 | 346篇 |
1972年 | 348篇 |
1971年 | 311篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
J B Croft J L Cresanta L S Webber S R Srinivasan D S Freedman G L Burke G S Berenson 《Southern medical journal》1988,81(3):341-9, 353
Fasting serum lipids, lipoprotein cholesterol, and other cardiovascular disease risk factors were examined in 321 natural parents of children with low and/or high levels of beta- and pre-beta-lipoprotein cholesterol. Parents of children from low pre-beta-lipoprotein groups had elevated alpha- and lower pre-beta-lipoprotein cholesterol levels. Parents whose children had high beta-lipoprotein cholesterol levels also had high serum total and beta-lipoprotein cholesterol levels. Parents of children with high levels of both beta- and pre-beta-lipoprotein cholesterol had a high prevalence of both abnormal risk factor levels, as well as clinical evidence of early coronary artery disease (before age 50 years). These observations show that parents of children with high beta- and/or pre-beta-lipoprotein cholesterol levels have greatly enhanced risk for cardiovascular disease, and children mirror their parents' lipoprotein cholesterol levels. These observations emphasize the need for cardiovascular risk evaluation early in life, especially in high-risk families. 相似文献
82.
C Lynn Van Antwerpen MD Sidney M Gospe Jr MD PhD Nancy A Wade MD 《Pediatric neurology》1988,4(6):379-380
A 12-year-old girl developed a reversible myeloradiculopathy 1 week after a wasp sting. Delayed neurologic hypersensitivity reactions to Hymenopteran stings occur primarily in adults. Reactions involving both the peripheral and central nervous systems are extremely rare and have never been reported in a child. The mechanisms underlying this uncommon reaction may be related to age-dependent differences in immunologic responses. 相似文献
83.
The phosphorylation patterns of isolated red blood cell (RBC) membranes labeled with [ γ-32p]ATP are altered by Zn++ ions. Zn++ ions caused an increased phosphate incorporation into a 72 KDa protein and several proteins in the 40–60 KDa region and a decrease in the labeling of a 53 KDa protein. The 72 KDa and 53 KDa proteins have been identified as protein 4.2 and a protease-cleaved fragment of protein 3, respectively. Evidence suggests that the changes in phosphorylation pattern may be due to the stimulation of endogenous membrane alkaline phosphatase(s). Our results suggest that Zn++, at physiological concentrations in the intact erythrocyte, could modulate the phosphorylation of selected proteins which may regulate their association in the cytoskeletal network. 相似文献
84.
Vasoactive intestinal peptide (VIP), the structurally homologous pituitary adenylate cyclase-activating peptide (PACAP) and the pituitary hormone, prolactin (PRL) enhance rapid eye movement sleep (REMS). VIP and PACAP are both inducers of PRL gene expression and release in the pituitary gland. Little is known about PRL regulation in the brain although it is hypothesized that the REMS-promoting activity of i.c.v. administered VIP may be mediated via the activation of cerebral PRL. To test whether VIP or PACAP in fact increase intracerebral mRNA, the peptides (VIP: 30 or 300 pmol; PACAP: 220 pmol) were injected i.c.v. into rats at dark onset. 1 h later, cDNA was synthesized from purified hypothalamic mRNA. Standardized amounts were analysed for PRL using the polymerase chain reaction followed by Southern blotting and hybridization. Compared with β-actin mRNA levels, both VIP and PACAP increased PRL mRNA levels in a dose-dependent fashion though VIP was more effective on a molar basis. The previously reported alternatively spliced PRL mRNA (lacking exon 4) was not detected. The data support the hypothesis that the REMS-promoting activity of central VIP and PACAP might be mediated by cerebral PRL. 相似文献
85.
Arterial wall injury and proteoglycan changes in atherosclerosis 总被引:1,自引:0,他引:1
G S Berenson B Radhakrishnamurthy S R Srinivasan P Vijayagopal E R Dalferes 《Archives of pathology & laboratory medicine》1988,112(10):1002-1010
The concept of injury as a mechanism leading to atherosclerosis has been fostered by numerous studies of initiating factors and by observation of the response of cardiovascular connective tissue, ie, cellular and extracellular matrix components. Carbohydrate-protein macromolecules of the extracellular matrix are a complex group of biologically important substances that play a crucial role in mesenchymal tissue repair following injury, a process needed to maintain arterial wall integrity. Of particular interest are the proteoglycans that enter into a variety of roles, from that of inhibiting atherosclerosis and helping to maintain fibrillar structures to that of taking part in lipid deposition in the development of atherosclerosis. 相似文献
86.
R. S. Kurban F. I. Preffer A. J. Sober M. C. Mihm Jr. R. L. Barnhill 《Journal of cutaneous pathology》1992,19(5):423-428
We report a case of melanoma arising in a large nevus spilus. On histologic examination, the nevus spilus had diagnostic features of melanocytic dysplasia. Further characterization by flow cytometry showed DNA-aneuploidy within the melanoma as well as in one of the darker pigmented papules within the nevus spilus. The significance of this finding and a review of melanomas originating in nevi spili are presented. 相似文献
87.
88.
89.
A short C-terminal sequence is necessary and sufficient for the targeting of chitinases to the plant vacuole. 总被引:20,自引:4,他引:16 下载免费PDF全文
J M Neuhaus L Sticher F Meins Jr T Boller 《Proceedings of the National Academy of Sciences of the United States of America》1991,88(22):10362-10366
Tobacco contains different isoforms of chitinase (EC 3.2.1.14), a hydrolase thought to be involved in the defense against pathogens. Deduced amino acid sequences for putatively vacuolar, basic chitinases differ from the homologous extracellular, acidic isoforms by the presence of a C-terminal extension. To examine the role of this C-terminal extension in protein sorting, Nicotiana silvestris plants were stably transformed with chimeric genes coding for tobacco basic chitinase A with and without the seven C-terminal amino acids. In plants expressing unmodified chitinase A, the enzyme activity was low in the intercellular wash fluid but high in protoplasts and isolated vacuoles. In contrast, in plants expressing mutant chitinase lacking the C terminus, the activity was high in the intercellular wash fluid but low in protoplasts. N. silvestris plants were also transformed with similar constructions coding for a structurally unrelated, extracellular cucumber chitinase. In plants expressing unmodified cucumber chitinase, its activity was present in the intercellular wash fluid and absent from protoplasts. In plants expressing cucumber chitinase with the C-terminal extension from tobacco chitinase A, activity was low in intercellular wash fluids but high in protoplasts and vacuoles. These results demonstrate that the C-terminal extension of tobacco chitinase A is necessary and sufficient for the vacuolar localization of chitinases and, therefore, that it comprises a targeting signal for plant vacuoles. 相似文献
90.
Thomas Patrick S. Jr; Fraley Gregory S.; Damian Vincent; Woodke Lillie B.; Zapata Francisco; Sopher Bryce L.; Plymate Stephen R.; La Spada Albert R. 《Human molecular genetics》2006,15(19):2972
Human Molecular 相似文献