全文获取类型
收费全文 | 34199篇 |
免费 | 2030篇 |
国内免费 | 160篇 |
专业分类
耳鼻咽喉 | 353篇 |
儿科学 | 826篇 |
妇产科学 | 834篇 |
基础医学 | 5038篇 |
口腔科学 | 1958篇 |
临床医学 | 2867篇 |
内科学 | 7732篇 |
皮肤病学 | 1077篇 |
神经病学 | 2931篇 |
特种医学 | 591篇 |
外科学 | 2813篇 |
综合类 | 145篇 |
一般理论 | 21篇 |
预防医学 | 3862篇 |
眼科学 | 543篇 |
药学 | 2673篇 |
中国医学 | 197篇 |
肿瘤学 | 1928篇 |
出版年
2024年 | 42篇 |
2023年 | 411篇 |
2022年 | 900篇 |
2021年 | 1602篇 |
2020年 | 912篇 |
2019年 | 1313篇 |
2018年 | 1603篇 |
2017年 | 1065篇 |
2016年 | 1033篇 |
2015年 | 1263篇 |
2014年 | 1663篇 |
2013年 | 2028篇 |
2012年 | 3088篇 |
2011年 | 3255篇 |
2010年 | 1629篇 |
2009年 | 1379篇 |
2008年 | 2238篇 |
2007年 | 2170篇 |
2006年 | 1904篇 |
2005年 | 1693篇 |
2004年 | 1468篇 |
2003年 | 1233篇 |
2002年 | 1084篇 |
2001年 | 149篇 |
2000年 | 115篇 |
1999年 | 116篇 |
1998年 | 155篇 |
1997年 | 138篇 |
1996年 | 97篇 |
1995年 | 79篇 |
1994年 | 76篇 |
1993年 | 51篇 |
1992年 | 70篇 |
1991年 | 44篇 |
1990年 | 34篇 |
1989年 | 33篇 |
1988年 | 27篇 |
1987年 | 23篇 |
1986年 | 19篇 |
1985年 | 22篇 |
1984年 | 20篇 |
1983年 | 15篇 |
1982年 | 21篇 |
1981年 | 11篇 |
1980年 | 13篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1975年 | 8篇 |
1973年 | 8篇 |
1972年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Michelle L. DeOliveira Timothy M. Pawlik Ana L. Gleisner Lia Assumpcaom Gaspar J. Lopes-Filho Michael A. Choti 《Journal of gastrointestinal surgery》2007,11(8):970-976
Survival after resection of colorectal liver metastases has traditionally been associated with clinicopathologic factors.
We sought to investigate whether echogenicity of colorectal liver metastasis as assessed by intraoperative ultrasound (IOUS)
was a prognostic factor after hepatic resection. Prospective data on tumor IOUS appearance were collected in 84 patients who
underwent hepatic resection for colorectal liver metastasis. Images were digitally recorded, blindly reviewed, and scored
for echogenicity (hypo-, iso-, or hyperechoic). The median tumor number was 1 and the median tumor size was 5.0 cm. At the
time of surgery, the IOUS appearance of the colorectal liver metastases were hypoechoic in 35 (41.7%) patients, isoechoic
in 37 (44.0%) patients, and hyperechoic in 12 (14.3%) patients. Traditional clinicopathologic prognostic factors were similarly
distributed among the three echogenicity groups (all p > 0.05). Patients with a hypoechoic lesion had a significantly shorter median survival (30.2 months) compared with patients
who had either an isoechoic (53.2 months) or hyperechoic (42.3 months) lesion (p = 0.005). The 5-year survival after hepatic resection of colorectal liver metastasis was also associated with the echogenic
appearance of the lesion (hypoechoic 14.4 vs isoechoic 37.4 vs hyperechoic 46.2%) (p < 0.05). Intraoperative ultrasound echogenicity should be considered a prognostic factor after hepatic resection of metastatic
colorectal cancer.
This study was presented at the 47th annual meeting of The Society for Surgery of the Alimentary Tract, Los Angeles, CA, USA,
22 May 2006. 相似文献
12.
13.
Plasma levels and vascular effects of vasopressin in patients undergoing coronary artery bypass grafting. 总被引:1,自引:0,他引:1
Susana Novella Ana Cristina Martínez Rosa María Pagán Medardo Hernández Albino García-Sacristán Angel González-Pinto José María González-Santos Sara Benedito 《European journal of cardio-thoracic surgery》2007,32(1):69-76
OBJECTIVE: Recent studies have suggested that endogenous vasopressin (AVP) acts as a spasmogen during coronary artery bypass grafting (CABG). Given that AVP could induce vasospasm in the grafted vessel, we assessed the release of this peptide during and after CABG, and explored ways of counteracting its contractile effect on the internal mammary artery (IMA). METHODS: Plasma levels of AVP were determined by radioimmunoassay in 16 patients before, during and after CABG. Using isometric force recording techniques, we also investigated the mechanisms involved in the contractile effect of AVP in ring preparations of IMA specimens taken from 95 patients. RESULTS: Plasma AVP levels peaked after the start of cardiopulmonary bypass (CPB) and correlated well with serum osmolality (Pearson's r=0.9490; P<0.0001; n=16). An inverse correlation was observed between plasma AVP levels recorded at this stage and the maximal contraction induced in vitro by AVP in vascular rings from the same patients (Pearson's r=-0.6968; P<0.01; n=16). No change in the AVP response was produced by endothelium removal, exposure to the NO precursor (3 x 10(-4)M L-arginine), inhibition of nitric oxide (NO) synthase (3 x 10(-5) M L-NAME) or soluble guanylate cyclase (3 x 10(-6) M 1H-[1,2,4]oxadiazol [4,3,-alpha]quinoxalin-1-one (ODQ)), removal of the superoxide anion (100 U/ml superoxide dismutase (SOD) plus 1200 U/ml catalase) or hydroxyl radical (10(-4) M deferoxamine), or specific alpha1 - (10(-6) M prazosin) or endothelin (10(-5) M bosentan) receptor antagonism. In contrast, adenylate cyclase activation (3 x 10(-8) M forskolin) reduced the contractile response to AVP, while prostanoid synthesis (3 x 10(-6) M indomethacin) inhibition and blockade of Ca2+ -activated potassium channels (KCa) (10(-3) M tetraethylammonium (TEA)) enhanced AVP contraction. Age, gender and smoking also modified the AVP response. CONCLUSION: Our findings suggest a role for AVP as a modulator of vascular tone in human IMA. The effect of AVP is dependent on prostanoids and Ca2+ -activated K+ channels, so its dysfunction in pathophysiological cardiovascular processes could mean that AVP, among other factors, produces vasospasm in IMA grafts. 相似文献
14.
Ana Vanson Arthur P. Arnold Barney A. Schlinger 《General and comparative endocrinology》1996,102(3):342-350
3β-hydroxysteroid dehydrogenase/Δ5−Δ4isomerase (3β-HSD) activity was measured in primary dissociated cell cultures prepared from telencephalons of developing zebra finches. 3β-HSD activity was confirmed after cultures were incubated with [7-3H]pregneno- lone (Preg) or (1,2,6,7-3H-) dehydroepiandrosterone (DHEA) and3H-progesterone (Prog) and3H-androstenedione (AE) were detected in the medium. Product identity was confirmed by recrystallizations and by HPLC analysis. When DHEA was used as substrate,3H-estradiol and3H-estrone were also detected in the culture medium, presumably derived from the aromatization of3H-AE or3H-T produced from3H-DHEA. To test this idea, cultures were incubated with3H-DHEA together with radioinert AE or with fadrozole HCl, a potent and specific aromatase inhibitor. In the presence of radioinert AE,3H-AE increased but metabolites of3H-AE decreased in the media; in the presence of fadrozole,3H-estrogens decreased but3H-AE and its androgenic metabolite3H-5β-androstanedione increased. These data demonstrate 3β-HSD activity in the songbird brain. The presence of Prog and estradiol in these cultures suggest that Preg and DHEA can potentially serve as substrates for the ultimate formation of active sex steroids in the songbird telencephalon. 相似文献
15.
16.
Ernst P. Leumann Andreas Dietl Ana Matasovic 《Pediatric nephrology (Berlin, Germany)》1990,4(5):493-497
The molar ratios of oxalate and glycolate over creatinine were determined in single urine samples of 26 infants and 27 children aged 1–5 years. In 135 children aged 5–16 years, two urine specimens were collected, one before breakfast and one at noon. Oxalate was determined by oxalate oxidase, and glycolate was measured by a colorimetric method (improved chromatotropic acid-sulphuric acid assay after prior purification by cation and anion exchanger). Both ratios (expressed in mmol/mol creatinine and analysed on a log-normal basis) were highest in infants 0–6 months old [mean oxalate 147 (95% confidence interval: 60–360), mean glycolate 175 (72–425)]. The mean oxalate ratio was 72 mmol/mol (29–174) at the age of 7–24 months, 44 (19–101) at the age of 2–5 years and 22 (12–40) in adolescents aged 16 years. Molar glycolate ratios were higher, but disclosed the same pattern. Oxalate and glycolate ratios in fasting urines did not differ significantly from those in noon samples (except glycolate in the oldest age group). Oxalate ratios correlated well with glycolate ratios in children up to 5 years of age only. Random urine samples are thus suitable for screening. However, interpretation of data requires use of age-specific reference values that are based on comparable methods. 相似文献
17.
A coupled chromogenic reaction (based on an agar overlay combining NADH, pyruvate kinase, lactate dehydrogenase, phosphoenolpyruvate, ATP, and kanamycin sulfate with thiazolyl blue-phenazine methosulfate for detection of NADH consumption) was optimized for the detection of aminoglycoside phosphotransferases (APHs). When used after analytical isoelectrofocusing of bacterial extracts from APH-producing strains, this method revealed one band in each of two strains with a genetically confirmed APH (3′) I and two bands in another strain with both APH (3′) I and APH (3′) VI, whereas no bands were detected in susceptible control strains or in aminoglycoside-resistant microorganisms without APH genes. 相似文献
18.
Ana Martín-Ancel María Luisa Casas Bartolomé Bonet 《Infection control and hospital epidemiology》2004,25(7):611-613
A neonate vaccinated against HBV was the source of an occupational exposure to blood. She was tested for hepatitis B surface antigen and found to be positive, leading to unnecessary treatment, retesting, and concern. Evaluation of the infectious status of HBV should rely on other means if vaccination has recently occurred. 相似文献
19.
20.
António Travassos Susana Teixeira Pinto Ferreira Isaura Regadas Ana Sofia Travassos Florindo Esteves Esperancinha Isabel Prieto Grapa Pires Robert van Velze A Valido Maria do Céu Machado 《Ophthalmic surgery, lasers & imaging》2007,38(3):233-237
The anatomic response to intravitreal bevacizumab injection in three patients with aggressive, posterior retinopathy of prematurity is described. In all cases, the worse eye was treated with a single intravitreal injection of 0.75 mg of bevacizumab as monotherapy or complementary to laser therapy. In 24 hours, all injected eyes showed regression of the tunica vasculosa lentis and iris vessel engorgement and disappearance of iris rigidity. In addition, plus disease and retinal proliferation began to regress. None of the eyes required additional treatment. Follow-up of up to 10 months 相似文献