全文获取类型
收费全文 | 14412篇 |
免费 | 1333篇 |
国内免费 | 35篇 |
专业分类
耳鼻咽喉 | 165篇 |
儿科学 | 485篇 |
妇产科学 | 430篇 |
基础医学 | 1964篇 |
口腔科学 | 249篇 |
临床医学 | 1957篇 |
内科学 | 2647篇 |
皮肤病学 | 234篇 |
神经病学 | 1409篇 |
特种医学 | 705篇 |
外国民族医学 | 1篇 |
外科学 | 1668篇 |
综合类 | 267篇 |
一般理论 | 12篇 |
预防医学 | 1473篇 |
眼科学 | 325篇 |
药学 | 906篇 |
中国医学 | 18篇 |
肿瘤学 | 865篇 |
出版年
2022年 | 107篇 |
2021年 | 242篇 |
2020年 | 171篇 |
2019年 | 224篇 |
2018年 | 318篇 |
2017年 | 230篇 |
2016年 | 247篇 |
2015年 | 259篇 |
2014年 | 400篇 |
2013年 | 576篇 |
2012年 | 720篇 |
2011年 | 693篇 |
2010年 | 403篇 |
2009年 | 390篇 |
2008年 | 624篇 |
2007年 | 632篇 |
2006年 | 650篇 |
2005年 | 648篇 |
2004年 | 561篇 |
2003年 | 518篇 |
2002年 | 505篇 |
2001年 | 351篇 |
2000年 | 341篇 |
1999年 | 335篇 |
1998年 | 229篇 |
1997年 | 192篇 |
1996年 | 176篇 |
1995年 | 158篇 |
1994年 | 163篇 |
1993年 | 147篇 |
1992年 | 259篇 |
1991年 | 251篇 |
1990年 | 249篇 |
1989年 | 238篇 |
1988年 | 252篇 |
1987年 | 258篇 |
1986年 | 249篇 |
1985年 | 224篇 |
1984年 | 193篇 |
1983年 | 184篇 |
1982年 | 140篇 |
1981年 | 143篇 |
1980年 | 125篇 |
1979年 | 185篇 |
1978年 | 145篇 |
1977年 | 115篇 |
1976年 | 138篇 |
1975年 | 130篇 |
1974年 | 128篇 |
1973年 | 94篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
991.
While the androgens, including dihydrotestosterone (DHT), have been implicated in the development of androgenetic alopecia (AGA), the exact mechanism by which they exert their effect(s) is unknown. Since apoptosis is an integral component of the normal cycling of human hair, we investigated individuals clinically affected by AGA to assess whether objective differences in the expression of apoptosis-related immunohistochemical markers could be observed in scalp biopsies. Specimens from 16 alopecic male patients were stained with bd-2 and the terminal deoxynucleotidyltransferase dUTP fluorescein nick end-labeling (TUNEL) method was used to assess apoptotic activity in affected and unaffected areas ofthe scalp. Immunoreactivity was analyzed by quantifying staining differences within the same individual. Sections from 3 human volunteers were used to establish the method validity. Significant differences in the bcl-2 staining index (0.67 versus 0.42, p < 0.05) and TUNEL expression (5.7 versus 10.2, p < 0.05) were observed between the areas of the scalp that were clinically affected (frontal) and unaffected (occipital) by AGA. The Gaussian distributions of bcl-2 and TUNEL staining suggest that a relatively uniform population of follicles exists at the frontal hairline and/or that synchrony of follicular cycling occurs in AGA. The apoptosis "hot spot" revealed by TUNEL staining in the bulge-isthmus region of the murine follicle is also identifiable in the human follicle. 相似文献
992.
Dai T Wu Y Leng AS Ao Y Robel RC Lu SC French SW Wan YJ 《Experimental and molecular pathology》2003,75(3):194-200
Retinoids influence the pathogenesis of alcohol liver disease (ALD). To analyze the impact of retinoid X receptor alpha (RXRalpha) on ALD, alcohol-induced hepatotoxicity was studied using mice fed ethanol intragastrically for 25 days. Alcohol-induced microvesicular fat around the central vein and drug-induced morphological changes (loss of rough endoplasmic reticulum, pinkish cytoplasm, and enlarged hepatocyte) in the pericentral area were observed in the liver of wild-type mice. In the hepatocyte RXRalpha-deficient mouse liver, alcohol induced fat accumulation, mitosis, acute inflammation, and necrosis. The histology score after alcohol treatment was significantly higher in mutant mice than in wild-type mice. However, drug-induced morphological changes were not apparent in alcohol-treated hepatocyte RXRalpha-deficient mice. Northern analysis showed that the basal and alcohol-induced CYP2B, CYP2A, and CYP3A mRNA levels were lower in hepatocyte RXRalpha-deficient mice than in wild-type mice, which in turn may protect mutant mice from morphological changes. Compared with wild-type mice, hepatocyte RXRalpha-deficient mice have significant lower levels of S-adenosylmethionine and glutathione, which is further reduced after alcohol treatment, and that may account for severe liver injury induced by alcohol. The overall result suggests an important role of RXRalpha in preventing alcohol-induced liver injury. 相似文献
993.
Aae,an autotransporter involved in adhesion of Actinobacillus actinomycetemcomitans to epithelial cells
下载免费PDF全文
![点击此处可从《Infection and immunity》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The periodontal pathogen Actinobacillus actinomycetemcomitans possesses myriad virulence factors, among them the ability to adhere to and invade epithelial cells. Recent advances in the molecular manipulation of this pathogen and the sequencing of strain HK 1651 (http://www.genome.ou.edu/act.html) have facilitated examination of the genetics of its interaction with epithelial cells. The related gram-negative organism, Haemophilus influenzae, possesses autotransporter adhesins. A search of the sequence database of strain HK 1651 revealed a homologue with similarity in the pore-forming domain to that of the H. influenzae autotransporter, Hap. A. actinomycetemcomitans mutants deficient in the homologue, Aae, showed reduced binding to epithelial cells. A method for making A. actinomycetemcomitans SUNY 465 transiently resistant to spectinomycin was used with conjugation to generate an isogenic aae mutant. An allelic replacement mutant was created in the naturally transformable A. actinomycetemcomitans strain ATCC 29523. Lactoferrin, an important part of the innate host defense system, protects against bacterial infection by bactericidal and antiadhesion mechanisms. Lactoferrin in human milk removes or cleaves Hap and another autotransporter, an immunoglobulin A1 protease, from the surface of H. influenzae, thereby reducing their binding to epithelial cells. Human milk whey had similar effects on Aae from A. actinomycetemcomitans ATCC 29523 and its binding to epithelial cells; however, there was little effect on the binding of SUNY 465. A difference in the genetic structure of aae in the two strains, apparently due to the copy number of a 135-base repeated sequence, may be the cause of the differential action of lactoferrin. aae is the first A. actinomycetemcomitans gene involved in adhesion to epithelial cells to be identified. 相似文献
994.
A rapid 'one-plate' in vitro test for pyrogens 总被引:2,自引:0,他引:2
Poole S Mistry Y Ball C Gaines Das RE Opie LP Tucker G Patel M 《Journal of immunological methods》2003,274(1-2):209-220
A rapid, 'one-plate' monocyte-activation test is described for detecting endotoxin and non-endotoxin pyrogens in parenteral medicinal products. The one-plate test offers useful gains over conventional 'two-plate' (cell culture plate+ELISA plate) tests in terms of its limit of detection, robustness, speed and cost. The 'one-plate' test is likely to be applicable to a wide range of products because it allows less time for product interference in the test. The 'one-plate' test utilises pyrogen-free anti-cytokine (interleukin (IL)-6 or tumour necrosis factor alpha (TNFalpha)) antibodies (Ab), coated and stabilised onto (pyrogen-free) 96-well plates. Monocytes/monocytic cells, endotoxin (lipopolysaccharides, LPS) standard or sample and (pyrogen-free) second (labelled) Ab are cultured together (usually for 2-4 h) on the Ab-coated plate and then the plate is washed and the ELISA completed. There is no transfer from one plate to another and no (further) incubations of (released) cytokine with, first, coating Ab and, then, developing Ab since these steps have already taken place during the initial cell culture. The rapid, 'one-plate' test is readily automated. The preferred readout is IL-6, which gives a limit of detection of 0.015 endotoxin units (EU)/ml with peripheral blood mononuclear cell (PBMNC), 0.03 EU/ml with diluted whole blood and 0.05 EU/ml with a monocytic cell line (MONO MAC 6). 相似文献
995.
996.
Ovarian cancer remains the most deadly gynecologic malignancy, resulting in an estimated 23,300 new cases and 13,900 deaths in the United States in the year 2002. The discovery of the BRCA1 gene in 1994 has proven to be of great interest to the study of hereditary ovarian cancer. BRCA1 gene mutation confers a 16-42% lifetime risk of the development of ovarian cancer in those affected. Although BRCA1 functions as a tumor suppressor gene, conflicting studies have shown that BRCA1 dysfunction alone may not be sufficient for tumorigenesis. p53 is a tumor suppressor gene found to be dysfunctional in nearly 50% of all human cancers and in up to 80% of ovarian malignancies. The p53 protein product plays a crucial role in DNA surveillance and repair at the Gap 1-synthesis (G1-S) cell cycle checkpoint. Studies exhibiting the interaction of BRCA1 and p53 and the role of this interaction in DNA damage response led many investigators to suggest that p53 gene mutation is required for BRCA1-associated tumor development. This review explores the evidence for BRCA1 and p53 interplay, and outlines the crucial role p53 may play in BRCA1-related ovarian cancer. 相似文献
997.
BACKGROUND: Incontinent urinary diversions are frequently performed in gynecologic oncology. The incontinent urinary diversions generally utilize a short segment of distal ileum or colon as a conduit. Conduit complications such as anastomosis leaks and strictures may be related to the technique utilized for inserting and securing the ureters and the degree of postimplant manipulation. TECHNIQUE: We describe a technique using a metal Yankaur suction device placed through the conduit's matured stoma to facilitate the mucosa-to-mucosa anastomosis of the ureters. This procedure allows for tension-free ureteral anastomoses, the isolation of the ideal conduit length, optimal stomal maturation, and reduced manipulation of the conduit after the ureteral anastomoses. CONCLUSION: This modification provides an elegant, yet simple and expedient, method of ureteral anastomosis to the incontinent urinary conduit. 相似文献
998.
Insulin pump therapy in pediatrics: a therapeutic alternative to safely lower HbA1c levels across all age groups 总被引:1,自引:1,他引:0
Ahern JA Boland EA Doane R Ahern JJ Rose P Vincent M Tamborlane WV 《Pediatric diabetes》2002,3(1):10-15
Abstract: Objective: To examine the efficacy and safety of using continuous subcutaneous insulin infusion (CSII) therapy in a large group of patients 18 months to 18 yr from a single pediatric diabetes program. Research design and methods: All patients ≤ 18 yr of age starting on CSII from 1 January 1997 to 31 March 2000 at the Yale Children's Diabetes Program were included. Clinical data were collected prospectively before and during pump treatment. HbA1c was the primary efficacy outcome and rates of diabetes‐related adverse events were the primary safety measures. Results: One hundred and sixty‐one children ranging in age from 18 months to 18 yr received CSII for an average of 32 ± 9 months when data collection was closed on 31 October 2001, including 26 preschoolers (< 7 yr), 76 school‐agers (7–11 yr) and 59 adolescents (12–18 yr). Mean HbA1c levels were 7.1% in the preschoolers, 7.8% in the school‐agers and 8.1% in the adolescents prior to the start of CSII. There was a significant and consistent reduction in mean HbA1c levels after 12 months of CSII (to 6.5% in preschoolers, 7.3% in school‐agers and 7.4% in adolescents, p < 0.02 vs. prepump) that was maintained at the most recent visit. Improved diabetes control was achieved with CSII without increasing daily insulin doses and in association with a decrease in the frequency of severe hypoglycemic events (p < 0.05 vs. prepump, all three age groups combined). Conclusions: CSII is an effective alternative to injection therapy in a large pediatric diabetes clinic setting. Even very young patients can utilize CSII to safely lower HbA1c levels. 相似文献
999.
BACKGROUND: Cutaneous cylindromas are benign adnexal tumors that may occur as a solitary lesion or in a multiple familiar pattern. Malignant change is rare. The association of multiple trichoepitheliomas and cylindromas, the so called Brooke-Spiegler Syndrome, is supposed to be inherited in an autosomal dominant manner. PATIENTS: A 55 year old woman presented with multiple skin tumors on the scalp, as well as the nasolabial and periauricular area since the age of 20 years. Her daughter and her nephew were also affected. Tumors were surgically removed for cosmetic reasons and showed histological signs of benign cylindromas and trichoepitheliomas. 35 years after diagnosis patient presented with a large exulceration on the right occipital area with intracranial invasion. Staging revealed multiple metastases in both lungs. Patient died 1 month later. RESULTS: Histological examination showed beside zones of massive necrosis multiple mitosis. The jigsaw puzzle pattern and the thick PAS positive basal layer, the striking characteristics of benign cylindromas, were lost. These histological findings and the clinical presentation led to the diagnosis of cylindrocarcinoma. CONCLUSIONS: Cylindrocarcinoma is an aggressive tumor with tendency to a local destructive growth and metastases. As malignant transformation of a benign cylindroma occurs more often in the multiple form a close follow-up of patients with multiple cylindromas is necessary. A family study is indicated. 相似文献
1000.