全文获取类型
收费全文 | 2037篇 |
免费 | 107篇 |
国内免费 | 47篇 |
专业分类
耳鼻咽喉 | 8篇 |
儿科学 | 82篇 |
妇产科学 | 39篇 |
基础医学 | 158篇 |
口腔科学 | 52篇 |
临床医学 | 281篇 |
内科学 | 376篇 |
皮肤病学 | 68篇 |
神经病学 | 50篇 |
特种医学 | 153篇 |
外科学 | 161篇 |
综合类 | 250篇 |
一般理论 | 6篇 |
预防医学 | 147篇 |
眼科学 | 33篇 |
药学 | 175篇 |
中国医学 | 76篇 |
肿瘤学 | 76篇 |
出版年
2021年 | 30篇 |
2020年 | 17篇 |
2018年 | 14篇 |
2017年 | 31篇 |
2016年 | 22篇 |
2015年 | 43篇 |
2014年 | 63篇 |
2013年 | 77篇 |
2012年 | 83篇 |
2011年 | 100篇 |
2010年 | 104篇 |
2009年 | 90篇 |
2008年 | 101篇 |
2007年 | 79篇 |
2006年 | 52篇 |
2005年 | 51篇 |
2004年 | 30篇 |
2003年 | 42篇 |
2002年 | 33篇 |
2001年 | 39篇 |
2000年 | 20篇 |
1999年 | 48篇 |
1998年 | 52篇 |
1997年 | 44篇 |
1996年 | 56篇 |
1995年 | 37篇 |
1994年 | 41篇 |
1993年 | 24篇 |
1992年 | 25篇 |
1991年 | 27篇 |
1990年 | 17篇 |
1989年 | 35篇 |
1988年 | 34篇 |
1987年 | 27篇 |
1986年 | 26篇 |
1985年 | 25篇 |
1984年 | 25篇 |
1983年 | 26篇 |
1982年 | 19篇 |
1981年 | 23篇 |
1980年 | 20篇 |
1979年 | 13篇 |
1977年 | 13篇 |
1959年 | 32篇 |
1958年 | 33篇 |
1957年 | 40篇 |
1956年 | 45篇 |
1955年 | 47篇 |
1954年 | 52篇 |
1948年 | 15篇 |
排序方式: 共有2191条查询结果,搜索用时 15 毫秒
1.
Taste sensitivity was evaluated by suprathreshold scaling of six concentrations each of sodium chloride, sucrose, citric acid, and quinine hydrochloride. Magnitude estimation was used as the method of scaling. The study group was composed of 22 males and 19 females were either patients (institutionalized) or staff members of the Jewish Institute for Geriatric Care. Data from each patient were used to compute individual slopes and Y-intercepts of the log to log transformations for each solution sequence. The mean age of the persons who were institutionalized was significantly higher than that of the staff members. In addition, the mean age of the females was 10 years older than that of the males. The older adult males seemed to have impaired taste function that resulted in significant decreases in total perceived intensity of several taste solutions. No significant differences were shown in taste ability between the relatively healthy younger staff member subjects and the older, more infirm, institutionalized subjects. 相似文献
2.
Introduction and Aims. Different self‐report methods tend to produce different estimates of alcohol consumption. The present study compares differences in rates and risk levels based on responses to a modified version of the Daily Drinking Questionnaire (m‐DDQ) and quantity‐frequency (QF) questions. Design and Methods. The sample comprised 2082 university students, 61% of whom were female and 39% male with a mean age of 23.5 years. An email containing an online link to a brief six‐question survey was emailed to students enrolled in participating faculties at the University of Wollongong, Australia. Current drinkers completed m‐DDQ and QF questions about alcohol consumption. Results. QF methods identified significantly lower estimates of consumption (Mean = 9.15, SD = 12.51) compared with m‐DDQ (Mean = 13.06, SD = 14.07). Allocation to risk categories based on the Australian Alcohol Guidelines were conducted for both the m‐DDQ and QF methods. Almost twice as many students were found to be drinking at levels considered risky using the m‐DDQ method compared with QF. In addition, the relative rank order of participants varied significantly between the two methods. Discussion and Conclusions. The m‐DDQ method identified higher rates of drinking and categorised almost twice as many individuals into risky categories of drinking compared with QF. Such variations have major implications for identification of risk groups in health promotion or prevention programs.[Utpala‐Kumar R, Deane FP. Rates of alcohol consumption and risk status among Australian university students vary by assessment questions. Drug Alcohol Rev 2009] 相似文献
3.
4.
FRANK ESPERSEN NIELS FRIMODT-MLLER VIBEKE THAMDRUP ROSDAHL OVE JESSEN VIGGO FABER KIRSTEN ROSENDAL 《Journal of internal medicine》1987,222(5):465-470
ABSTRACT. A total of 6 253 cases of Staphylococcus aureus bacteremia, including 274 (4.4%) endocarditis cases, were registered in Denmark in the period 1975–1984. Patients with hematological malignancies and/or agranulocytosis accounted for 479 of the bacteremia cases. The incidence of endocarditis in this group of patients was only 0.4% as compared to 4.7% in other patients with staphylococcal bacteremia (p<0.01). The lower incidence of endocarditis complicating bacteremia in these patients may justify a shorter course of therapy than usually recommended for suspected endocarditis. Patients with hematological malignancies and other patients with agranulocytosis had a higher mortality (49 and 46%, respectively) than other patients with S. aureus bacteremia (33%). The highest mortality was found in patients with multiple myeloma (71%, p<0.01), the lowest in patients with acute lymphocytic leukemia (28%, p<0.01). The higher mortality in these patients may indicate that empiric antibiotic regimens in granulocytopenic patients should include a specific anti-staphylococcal agent. 相似文献
5.
HA Carpay P Matthijsse M Steinbuch PGH Mulde 《Cephalalgia : an international journal of headache》1997,17(5):591-595
In an open, randomized cross-over study in 124 patients, we compared the efficacy, safety and patient preference of oral and subcutaneous sum triptan in the acute treatment of migraine. Patients were treated for 3 attacks or 3 months and then crossed over. Primary clinical efficacy was defined as a reduction in headache severity on a four-point self-rating scale from severe (3) or moderate (2) to mild (1) or none (0), or mild (1) to none (0). Efficacy was evaluated 2 h after the administration of subcutaneous and 4h after the administration of oral sumatriptan. Subcutaneous sumatriptan was significantly more effective than oral sumatriptan in relieving headache (over all three attacks 78% vs 61% improvement), improving clinical disability (55% vs 41 % improvement) and relieving nausea (69% vs 53%), vomiting (72% vs 32%) and phono- or photophobia (67% vs 49%). Median time to recurrence was shorter after subcutaneous (12.5 h) than after oral sumatriptan (18 h); the number of patients experiencing a recurrence was similar Patients reported more adverse events after subcutaneous sumatriptan (1.32 per attack) than after the oral form (0.85 per attack), but all adverse events were mild to moderate in intensity and of short duration. Patient opinion was more often positive after subcutaneous sumatriptan. These results may be useful in counselling patients to choose between the available marketed formulations of sumatriptan. 相似文献
6.
Novel polyanionic proteins were designed to increase the rate of heparin cofactor II (HC) inhibition of α-thrombin, an essential protease in the coagulation cascade. Two α-helical coiled-coil proteins, a 62-residue dimer containing 8 Glu residues (E8C) and a 104-residue dimer containing 14 Glu residues (E14C), plus two 31-residue control peptides containing 8 Glu residues each (E8A and E8B), were chemically synthesized, structurally characterized and enzymatically assayed. Circular dichroic spectrophotometry indicated that both E8C and E14C formed stable two-chain α-helical coiled coils at pH 7 and 25 °C. The control peptides were only partially α-helical. E14C remained folded at 90 °C but E8C was half unfolded at 49 °C. Coiled-coil proteins E8C and E14C maximally accelerated by 35- and 33-fold, respectively, the rate of HC inhibition of α-thrombin. None of these compounds accelerated antithrombin inhibition of α-thrombin, and neither control peptide accelerated HC inhibition of α-thrombin. Acceleration of the HC inhibition of α-thrombin showed bimodal dependence on the concentration of the polyanionic protein, which is consistent with formation of a HC-coiled-coil-thrombin ternary complex. The results suggest that antithrombotic polyanionic α-helical coiled-coil proteins can be designed and synthesized and that the occurrence of secondary structure can be correlated with biologcal activity. © Munksgaard 1995. 相似文献
7.
8.
超细β-磷酸三钙/聚-L-乳酸复合材料的制备与骨折内固定器的加工 总被引:3,自引:0,他引:3
目的:制备分散性良好的超细β-磷酸三钙(β-TCP)/聚-L-乳酸(PLLA)复合材料及新型可吸收骨折内固定器。方法:通过研磨方法制备β-TCP超细粒子,用一缩二乙二醇作分散剂研磨β-TCP后,再将β-TCP与PLLA超声混合,制得复合材料,经注塑加工制成可吸收骨钉,并采用扫描电镜等方法进行表征。结果与结论:用一缩二乙二醇作分散剂研磨β-TCP后再经超声混合,可以使β-TCP超细粒子在复合材料中分散均匀,粒子大小仅为300nm左右,β-TCP与PLlA基体之间结合良好。超细β-TCP/PLLA复合材料可加工成可吸收骨钉,弯曲强度达到100MPa左右,完全满足松质骨内固定的要求。 相似文献
9.
COLMAN R. D.; FRANK M.; LOUGHNAN B. A.; COHEN D. G.; CATTERMOLE R. 《British journal of anaesthesia》1988,61(6):720-729
Twenty patients who underwent elective Caesarean section receivedranitidine 150 mg by mouth 814 h, and 50 mg i.m. 90 min,before surgery. Intraoperative gastric aspiration resulted incontents with a pH > 2.5 and volume < 25 ml in all patients(mean pH 6.5 (SD 0.8); mean volume 9.0 (SD 7.2) ml). Sixty patientsin labour, who received ranitidine 50 mg i.m. 6-hourly, underwentemergency surgery. Half of this group received, in addition,a single preinduction dose of either 15 or 30 ml of sodium citrate0.3 mol litre-1. A further 30 patients who remained unmedicatedduring labour and required emergency surgery received a preinductiondose of 15 or 30 ml of sodium citrate 0.3 mol litre-1 alone.Ranitidine medication resulted in a mean aspirated gastric volumeof 31.4 (26.6) ml and pH of 5.3 (2.1); five of 30 patients hada pH < 2.5. The addition of sodium citrate 0.3 mol litre-1resulted in gastric pH > 2.5 in all patients and a mean gastricvolume of 43.2 (38.3) ml. The group who received only sodiumcitrate 0.3 mol litre-1 had a mean pH of 5.3 (1.1) and a meanvolume 122.7 (98.2) ml. 相似文献
10.
ALEKSANDRA MISICKA ANDRZEJ W. LIPKOWSKI ROBERT HORVATH PEG DAVIS FRANK PORRECA HENRY I. YAMAMURA VICTOR J. HRUBY 《Chemical biology & drug design》1994,44(1):80-84
Further efforts to correlate the topography of the bioactive structures of DPDPE and the deltorphins, two δ-opioid receptor active peptide families, are reported. A number of DPLPE-deltorphin chimeric peptides have been synthesized in which the C-terminal dipeptide δ-address of the deltorphins (-Val-GlyNH2, -Nle-GlyNH2) have been linked to the highly δ-opioid selective cyclic peptides DPDPE or DPLPE. These studies demonstrate that a major structural feature determining high potency of hybrid analogues is the chirality of the amino acid residue in position 5. The radioligand binding assays have revealed a decrease in potency (compared to DPDPE) at §-receptors when the C-terminal dipeptides were added to DPDPE. On the other hand, chimeric peptides of DPLPE with these same C-terminal dipeptides retained high δ-selectivity and affinity. Similar results were obtained using the mouse vas deferens (MVD) and guinea pig ileum (GPI) bioassays. The importance of the hydrophilicity of amino acids in positions 2 and 5 for δ-selectivity is consistent with the previous finding for DPLPE and DPDPE. On the other hand, the replacement of phenylalanine-4 with p-chlorophenylalanine-4 did not increase δ-selectivity as in DPDPE. These findings suggest that the δ-receptor interacts with hybridized enkephalins and deltorphins somewhat differently than with DPDPE. 相似文献