全文获取类型
收费全文 | 5077篇 |
免费 | 539篇 |
国内免费 | 28篇 |
专业分类
耳鼻咽喉 | 39篇 |
儿科学 | 189篇 |
妇产科学 | 155篇 |
基础医学 | 651篇 |
口腔科学 | 102篇 |
临床医学 | 493篇 |
内科学 | 1228篇 |
皮肤病学 | 59篇 |
神经病学 | 267篇 |
特种医学 | 285篇 |
外科学 | 659篇 |
综合类 | 255篇 |
一般理论 | 1篇 |
预防医学 | 525篇 |
眼科学 | 92篇 |
药学 | 307篇 |
中国医学 | 41篇 |
肿瘤学 | 296篇 |
出版年
2022年 | 44篇 |
2021年 | 82篇 |
2020年 | 55篇 |
2019年 | 83篇 |
2018年 | 75篇 |
2017年 | 60篇 |
2016年 | 85篇 |
2015年 | 114篇 |
2014年 | 150篇 |
2013年 | 166篇 |
2012年 | 225篇 |
2011年 | 205篇 |
2010年 | 195篇 |
2009年 | 181篇 |
2008年 | 194篇 |
2007年 | 199篇 |
2006年 | 225篇 |
2005年 | 194篇 |
2004年 | 173篇 |
2003年 | 201篇 |
2002年 | 178篇 |
2001年 | 148篇 |
2000年 | 156篇 |
1999年 | 150篇 |
1998年 | 84篇 |
1997年 | 93篇 |
1996年 | 90篇 |
1995年 | 85篇 |
1994年 | 64篇 |
1993年 | 66篇 |
1992年 | 110篇 |
1991年 | 101篇 |
1990年 | 109篇 |
1989年 | 120篇 |
1988年 | 100篇 |
1987年 | 100篇 |
1986年 | 93篇 |
1985年 | 90篇 |
1984年 | 63篇 |
1983年 | 58篇 |
1982年 | 47篇 |
1981年 | 32篇 |
1980年 | 43篇 |
1979年 | 59篇 |
1978年 | 48篇 |
1977年 | 44篇 |
1974年 | 40篇 |
1973年 | 40篇 |
1972年 | 32篇 |
1971年 | 35篇 |
排序方式: 共有5644条查询结果,搜索用时 15 毫秒
71.
Abnormal esophageal transit in patients with typical reflux symptoms but normal endoscopic and pH profiles 总被引:2,自引:0,他引:2
C A Eriksen P T Cullen D Sutton N Kennedy A Cuschieri 《American journal of surgery》1991,161(6):657-661
There is a small, well-known cohort of patients who, despite classic reflux symptoms, have a normal esophageal pH profile and endoscopic picture. The treatment of these patients has proved problematic. In an attempt at determining the pathophysiology of this subgroup, we investigated the esophageal transit, using the radiolabeled solid bolus esophageal egg transit technique, in 58 such patients: 25 males, 33 females, mean age 39.5 years (range: 13 to 65 years). The egg transit was normal in 31 (53.4%) patients. In the remaining 27 (46.6%) patients, the condensed image analysis showed the following specific abnormal transit patterns: "step" delay pattern, demonstrating segmental hold-up in mid- or distal esophagus in 16 (59.3%); nonspecific delay in 6 (22.2%); oscillatory pattern in 3 (11.1%); and total nonclearance during the study period (4 minutes) in 2 (7.4%) patients. The patients with abnormal transit patterns had demographic parameters and symptom scores similar to those found in patients with normal transit. This study shows that almost 50% of patients with reflux symptoms and negative pH and endoscopy have abnormal esophageal transit, and almost two thirds of these patients display segmental transit delay in the lower half of the esophagus. The effect on symptomatology by prokinetic agents in the patient subgroup needs evaluation. 相似文献
72.
Since exogenous hemin has been shown to exert a variety of stimulatory effects on erythroid cells, including the augmentation of hemoglobin synthesis, we determined its effect on early stages of erythroid development by employing clonal cells assays. The addition of hemin at a concentration of 2 X 10(-4) M to cultures of normal murine marrow substantially increased the observed number of primitive BFU-E, which was in contrast to its lack of an effect on more mature erythroid colony-forming cells. This cell-specific enhancement of primitive BFU-E resulted in marrow frequencies equivalent to or exceeding those reported in the presence of "burst-promoting activity." In the presence of hemin, the number of BFU-E was also observed to be linearly related to the number of cells plated at very low plating densities, and the cell titration curve was observed to extrapolate to the origin. The evidence suggests that hemin may be a primary growth regulator of early developmental stages of erythroid progenitor cells. 相似文献
73.
The evolution of a vascular surgeon at a district general hospital: is sub-specialisation inevitable?
下载免费PDF全文
![点击此处可从《Annals of the Royal College of Surgeons of England》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Sutton CD Gilmour JP Berry DP Lewis MH 《Annals of the Royal College of Surgeons of England》2000,82(4):272-274
We report a 15-year retrospective audit to evaluate the change in arterial surgical commitment on general surgical case mix of a single surgeon with a vascular interest at a district general hospital. There was a 409% increase in the number of arterial procedures performed combined with a fall of 52% in the total number of operations over the study period. We conclude that, with such a rapidly growing arterial caseload, sub-specialisation to vascular surgery is inevitable. 相似文献
74.
Levy MF Crippin J Sutton S Netto G McCormack J Curiel T Goldstein RM Newman JT Gonwa TA Banchereau J Diamond LE Byrne G Logan J Klintmalm GB 《Transplantation》2000,69(2):272-280
BACKGROUND: Whole organ extracorporeal perfusion of a genetically modified humanized (transgenic) pig liver has been proposed as a technology that may sustain patients with severe liver failure while awaiting human liver transplantation. METHODS: We report on two cases of successful extracorporeal perfusion of a transgenic pig liver in patients awaiting transplantation for fulminant hepatic failure. The pig livers used were transgenic for human CD55 (decay-accelerating factor) and human CD59. These transgenic modifications are designed to reduce or eliminate the hyperacute rejection inherent in pig-to-primate xenotransplants. We also report on the results of serial surveillance testing for presence of the porcine endogenous retrovirus (PoERV) in these two patients. RESULTS: Extracorporeal perfusion in two patients was performed for 6.5 and 10 hr, respectively, followed by the successful transplantation of a human liver and resultant healthy patients (18 and 5 months later as of this writing). The porcine livers showed evidence of synthetic and secretory function (decreasing protime and bilirubin, bile production). Serial polymerase chain reaction analysis of these patients' peripheral blood mononuclear cells has failed to show presence of PoERV DNA sequences. CONCLUSIONS: The CD55/CD59 transgenic porcine liver appears capable of safely "bridging" a patient to liver transplantation. Human PoERV infection from these livers has yet to be demonstrated. 相似文献
75.
Assessment of the mutagenicity of dichloroacetic acid in lacI transgenic B6C3F1 mouse liver 总被引:2,自引:0,他引:2
Dichloroacetic acid (DCA) is a chlorination byproduct found in finished
drinking water. When administered in drinking water this chemical has been
shown to produce hepatocellular adenomas and carcinomas in B6C3F1 mice over
the animal's lifetime. In this study, we investigated whether mutant
frequencies were increased in mouse liver using treatment protocols that
yielded significant tumor induction. DCA was administered continuously at
either 1.0 or 3.5 g/l in drinking water to male transgenic B6C3F1 mice
harboring the bacterial lacI gene. Groups of five or six animals were
killed at 4, 10 or 60 weeks and livers removed. At both 4 and 10 weeks of
treatment, there was no significant difference in mutant frequency between
the treated and control animals at either dose level. At 60 weeks, mice
treated with 1.0 g/l DCA showed a 1.3-fold increase in mutant frequency
over concurrent controls (P = 0.05). Mice treated with 3.5 g/l DCA for 60
weeks had a 2.3-fold increase in mutant frequency over the concurrent
controls (P = 0.002). The mutation spectrum recovered from mice treated
with 3.5 g/l DCA for 60 weeks contained G:C-->A:T transitions (32.79%)
and G:C-->T:A transversions (21.31%). In contrast, G:C-->A:T
transitions comprised 53.19% of the recovered mutants among control
animals. Although only 19.15% of mutations among the controls were at T:A
sites, 32.79% of the mutations from DCA-treated animals were at T:A sites.
This is consistent with the previous observation that the proportion of
mutations at T:A sites in codon 61 of the H-ras gene was increased in
DCA-induced liver tumors in B6C3F1 mice. The present study demonstrates
DCA-associated mutagenicity in the mouse liver under conditions in which
DCA produces hepatic tumors.
相似文献
76.
Fatty acid balance studies in term infants fed formula milk containing long-chain polyunsaturated fatty acids 总被引:1,自引:0,他引:1
C Morgan L Davies F Corcoran J Stammers J Colley SA Spencer D Hull 《Acta paediatrica (Oslo, Norway : 1992)》1998,87(2):136-142
Long-chain polyunsaturated fatty acids (LCP) are thought to be required for optimal nervous system development in the newborn. A commercial milk formula containing LCP (Aptamil-LCP) with a fatty acid profile closely resembling breast milk, has recently been introduced for term infants. The absorption of fatty acids in term infants was examined in a double-blind randomized controlled trial comparing Aptamil-LCP ( n = 20) and standard Aptamil ( n = 20). Formula-fed newborn infants were studied from birth for 14 d. Fat balances (3 d) were performed from d 10. A 3-d stool collection was performed from d 10 in a parallel breastfed group ( n = 21). Plasma samples were taken on d 6. Median fat excretion (mg kg−1 ) was 897.1, 615.0 and 355.2 with Aptamil, Aptamil-LCP and breastfeeding, respectively. The median total fat absorption coefficient in Aptamil-LCP-fed infants was higher than in those fed standard Aptamil ( p < 0:01). These findings were accounted for by differences in the excretion and absorption of long-chain saturated fatty acids (C14:0, C16:0 and C18:0). Higher fat excretion was associated with bulkier and firmer stools. Only trace amounts of LCP were detected in the stools of all groups. This accounted for less than 4% of dietary intake in Aptamil-LCP-fed infants. No differences in the utilization of LCP from Aptamil-LCP and breast milk feeding were apparent. Plasma phospholipid fatty acid composition data reflected differences in dietary LCP intake. Thus, PL LCP levels were highest in the breastfed infants and lowest in the Aptamil-fed infants, with values for the Aptamil-LCP-fed group falling in between. 相似文献
77.
Characterization of the insulin-like growth factor axis in a human hepatoma cell line (PLC) 总被引:4,自引:0,他引:4
Scharf JG; Schmidt-Sandte W; Pahernik SA; Ramadori G; Braulke T; Hartmann H 《Carcinogenesis》1998,19(12):2121-2128
78.
79.
Gerald Gartlehner Suzanne L West Kathleen N Lohr Leila Kahwati Jana G Johnson Russell P Harris Lynn Whitener Christiane E Voisin Sonya Sutton 《International journal for quality in health care》2004,16(5):399-406
BACKGROUND: An important concern for developers of clinical practice guidelines is how best to determine when guidelines require updating to ensure they remain current and evidence based. Because of the high costs associated with updating guidelines, recent attention has focused on approaches that can reliably assess the extent of updating required. Recently, Shekelle and colleagues proposed a model of limited literature searches with modest expert involvement as a way to reduce the cost and time requirements for assessing whether a guideline needs updating. METHODS: The main objective of this study was to compare the Shekelle et al. assessment model (review approach) and a conventional process using typical systematic review methods (traditional approach) in terms of comprehensiveness and effort. We modeled the review approach on that by Shekelle and colleagues but refined it iteratively over three phases to achieve greater efficiency. Using both methods independently, we assessed the need to update six topics from the 1996 Guide to Clinical Preventive Services from the US Preventive Services Task Force. Main outcomes included completeness of study identification, importance of missed studies and the effort involved. RESULTS: Although the review approach identified fewer eligible studies than the traditional approach, none of the studies missed was rated as important by task force members acting as liaisons to the project with respect to whether the topic required an update. On average, the review approach produced substantially fewer citations to review than the traditional approach. The effort involved and potential time saving depended largely on the scope of the topic. CONCLUSIONS: The revised review approach provides an efficient and acceptable method for judging whether a guideline requires updating. 相似文献