全文获取类型
收费全文 | 6833篇 |
免费 | 487篇 |
国内免费 | 33篇 |
专业分类
耳鼻咽喉 | 72篇 |
儿科学 | 161篇 |
妇产科学 | 135篇 |
基础医学 | 1161篇 |
口腔科学 | 86篇 |
临床医学 | 668篇 |
内科学 | 1533篇 |
皮肤病学 | 88篇 |
神经病学 | 748篇 |
特种医学 | 353篇 |
外科学 | 955篇 |
综合类 | 40篇 |
一般理论 | 6篇 |
预防医学 | 381篇 |
眼科学 | 94篇 |
药学 | 457篇 |
中国医学 | 7篇 |
肿瘤学 | 408篇 |
出版年
2023年 | 43篇 |
2022年 | 91篇 |
2021年 | 187篇 |
2020年 | 95篇 |
2019年 | 144篇 |
2018年 | 201篇 |
2017年 | 148篇 |
2016年 | 151篇 |
2015年 | 202篇 |
2014年 | 255篇 |
2013年 | 365篇 |
2012年 | 519篇 |
2011年 | 537篇 |
2010年 | 309篇 |
2009年 | 304篇 |
2008年 | 447篇 |
2007年 | 452篇 |
2006年 | 426篇 |
2005年 | 424篇 |
2004年 | 395篇 |
2003年 | 317篇 |
2002年 | 334篇 |
2001年 | 79篇 |
2000年 | 50篇 |
1999年 | 61篇 |
1998年 | 52篇 |
1997年 | 51篇 |
1996年 | 46篇 |
1995年 | 55篇 |
1994年 | 28篇 |
1993年 | 36篇 |
1992年 | 38篇 |
1991年 | 22篇 |
1990年 | 25篇 |
1989年 | 32篇 |
1988年 | 21篇 |
1987年 | 16篇 |
1986年 | 14篇 |
1985年 | 22篇 |
1984年 | 15篇 |
1983年 | 21篇 |
1982年 | 29篇 |
1981年 | 30篇 |
1980年 | 17篇 |
1979年 | 25篇 |
1978年 | 22篇 |
1976年 | 15篇 |
1974年 | 14篇 |
1973年 | 12篇 |
1972年 | 19篇 |
排序方式: 共有7353条查询结果,搜索用时 16 毫秒
61.
Liefeldt L Plentz A Klempa B Kershaw O Endres AS Raab U Neumayer HH Meisel H Modrow S 《Journal of medical virology》2005,75(1):161-169
Organ transplant recipients infected with parvovirus B19 frequently develop persistent viremia associated with chronic anemia and pure red cell aplasia. In this study, a male renal transplant recipient who had been infected with parvovirus B19/genotype 2 after renal transplantation at the age of 34 years is described. The patient was repeatedly treated with high dose intravenous immunoglobulin (IVIG) that resulted in the resolvement of symptoms but not in virus eradication. During an observation period of 33 months after transplantation three phases associated with high parvovirus B19 viremia were observed. Both the first and the second viremic phases were combined with severe anemia. Parvovirus B19 specific IgM-antibodies were initially detected at the beginning of the second phase in continually rising concentrations. Initially eradication of the virus by immunoglobulin therapy was reported after the first viremic phase [Liefeldt et al. (2002): Nephrol Dial Transplant 17:1840-1842]. Retrospectively this statement has to be corrected. It was based on the use of a qualitative PCR assay specific for parvovirus B19 genotype 1 associated with reduced sensitivity for detection of genotype 2. After sequence analysis of the viral DNA and adjustment of a real-time PCR assay (TaqMan) for quantitative detection of all three B19 virus genotypes analysis of consecutive serum samples allowed the demonstration of long lasting phases with reduced viral loads following IVIG-treatment. These results demonstrate that IVIG treatment of parvovirus B19-triggered anemia in transplant recipients offers an opportunity to resolve symptoms, but does not guarantee eradication of the virus. Since reactivation of parvovirus B19 infection can result in high virus load associated with the recurrence of symptoms repeated screening for viral DNA is recommended using the TaqMan system established for quantitative detection of all three genotypes of parvovirus B19. 相似文献
62.
Ovariectomized rats were housed either singly or in groups of three, with housing density kept constant. Subcutaneous injections of 0.8 μg estradiol benzoate (EB) were administered daily, beginning 6 days after surgery. The first two experiments provided evidence that isolation facilitated lordosis within 3 days of initial EB administration. Other behavioral components of female sexual receptivity were not affected. The third experiment involved comparison of the effects of isolation in ovariectomized and adrenalectomized-ovariectomized rats. Isolation again significantly facilitated lordosis in ovariectomized rats but no such trend was apparent in adrenalectomized rats even though high levels of lordosis were evident in these animals. One possible interpretation of this latter finding is that isolation of female rats facilitates estrogen-induced lordosis by increasing adrenocortical secretion. The present series of experiments demonstrate that social isolation can influence sexual receptivity in rodents. 相似文献
63.
Effects of aging on hypothalamic-pituitary-adrenal system function in non-human primates 总被引:1,自引:0,他引:1
The study was aimed at characterizing the changes in hypothalamic-pituitary-adrenal (HPA) axis function during aging in monkey models (Papio hamadryas and Macaca mulatta). It has been established by specific radioimmunoassay and enzyme immunoassay that basal plasma levels of adrenal androgenes (dehydroepiandrosterone-DHEA, dehydroepiandrosterone sulfate-DHEAS) and the early precursors of steroid hormones (pregnenolone and 17-hydroxypregnenolone) progressively decrease with age in baboons and macaques, while cortisol and 11-desoxycortisol concentrations do not change. The old female rhesus monkeys exhibited a higher cortisol and corticosterone response, but a lower DHEAS response to corticotropin-releasing hormone (CRH) administration then the young monkeys. The aged rhesus monkeys also exhibited a decrease of the adrenal cortex resiliency, that was manifested in the deceleration of the decrease of cortisol concentrations after the peak values had been reached in response to ACTH 1-39 administration. At the same time the ACTH 1-24 depot test revealed no age-related changes in the maximum capacity of monkey adrenals to synthesize and secrete cortisol. The aged monkeys also developed less sensitivity of the HPA axis to dexametasone suppression test. The age-related hormonal changes may play an important role in the age-related involutive processes and in the disorders of the adaptive ability of old organisms. 相似文献
64.
Origin and primary dispersal of the Mycobacterium tuberculosis Beijing genotype: clues from human phylogeography 总被引:2,自引:0,他引:2
下载免费PDF全文
![点击此处可从《Genome research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Mokrousov I Ly HM Otten T Lan NN Vyshnevskyi B Hoffner S Narvskaya O 《Genome research》2005,15(10):1357-1364
We suggest that the evolution of the population structure of microbial pathogens is influenced by that of modern humans. Consequently, the timing of hallmark changes in bacterial genomes within the last 100,000 yr may be attempted by comparison with relevant human migrations. Here, we used a lineage within Mycobacterium tuberculosis, a Beijing genotype, as a model and compared its phylogeography with human demography and Y chromosome-based phylogeography. We hypothesize that two key events shaped the early history of the Beijing genotype: (1) its Upper Palaeolithic origin in the Homo sapiens sapiens K-M9 cluster in Central Asia, and (2) primary Neolithic dispersal of the secondary Beijing NTF::IS6110 lineage by Proto-Sino-Tibetan farmers within east Asia (human O-M214/M122 haplogroup). The independent introductions of the Beijing strains from east Asia to northern Eurasia and South Africa were likely historically recent, whereas their differential dissemination within these areas has been influenced by demographic and climatic factors. 相似文献
65.
66.
Jovanović I Stefanović N Antić S Ugrenović S Djindjić B Vidović N 《Italian journal of anatomy and embryology = Archivio italiano di anatomia ed embriologia》2004,109(1):19-33
Psammoma bodies are one of many choroid plexus aging changes which origin is still enigma for the scientists. During our investigation psammoma bodies were studied on 30 postmortem brains by light microscopy. They stained red with HE, and were PAS and AB PAS positive. The largest number of lamellas were stained blue with Mallory's connective tissue stain, except peripheral and next to the center lamella which stained red. During the aging, psammoma bodies became larger and more irregular, which was followed with group area and perimeter, single psammoma body average area and average perimeter, average diameter and contour index increase. Psammoma bodies mearged in the second and the third age group and mearging process led to larger and more irregular structures formation. The results of this investigation suggest that psammoma bodies are more frequent in choroid plexus of healthy older people and during the aging they obtain larger dimensions, more irregular contours, which is the result of their mutual mearging. 相似文献
67.
Igor A. Yamskov Boris B. Berezin Vadim A. Davankov 《Macromolecular chemistry and physics.》1978,179(9):2121-2132
The paper describes the syntheses of four asymmetric sorbents, which contain S-(2-aminoethyl)-L -cysteine ( 1a ), S-(carboxymethyl)-L -cysteine ( 1c ), S,S′-(ethylene)-bis(L -cysteine) ( 2a ), and N,N′-(ethylene)-bis(D-methionine) ( 3a ) groupings as the chiral fixed ligands in a cross-linked polystyrene matrix. The sorbents were used for ligand-exchange chromatography of amino acid enantiomers in the presence of Cu(II) and Ni(II) ions. Enantioselective effects in the formation of mixed-ligand complexes consisting of a fixed ligand, a metal ion, and an amino acid enantiomer were determined. The highest values of enantioselectivity reaching 1 300 to 1 890J/mol were found in mixed-ligand complexes containing histidine or β-phenyl-α-alanine. 相似文献
68.
69.
Edward A. Sykes Madeline Lemke Daniel Potter Terry Li Zuhaib M. Mir Guy Sheahan Vincent Wu Boris Zevin 《Canadian journal of surgery》2021,64(1):E59
BackgroundSquare knots can be difficult to construct in deep body cavities. The reversing half-hitch alternating post (RHAP) surgical knot has noninferior tensile strength and performance characteristics in deep body cavities. We compared the enterotomy repairs of novice learners in simulated deep body cavities using RHAP versus square knots after proficiency-based training.MethodsUndergraduate students were randomized to RHAP (n = 10) or square knot (n = 10) groups and trained to defined proficiency. They then performed hand-sewn enterotomy repairs of cadaveric porcine small bowels on flat surfaces and in simulated deep body cavities. We recorded time to knot-tying proficiency and to enterotomy repair, and burst pressures for the repair.ResultsMean time-to-proficiency in knot tying was equivalent between the RHAP and square knot groups (23 [standard deviation (SD) 3] v. 21 [SD 2] min, p = 0.33). Mean time for enterotomy repair in deep cavities was shorter for the RHAP group (16 [SD 2] min v. 21 [SD 1] min, p = 0.02). Mean burst pressures for enterotomy repair were equivalent on flat surfaces (128 [SD 41] v. 101 [SD 36] mm Hg, p = 0.31), and were significantly higher for the RHAP group in simulated deep body cavities (32 [SD 13] v. 105 [SD 37] mm Hg, p = 0.05).ConclusionThe RHAP knots appear to have superior performance versus square knots when tied in a deep body cavity by novice learners. Future work should focus on demonstrating the clinical relevance and broad utility of the RHAP knot in abdominal surgery. Both knot types should be taught to novice learners. 相似文献
70.
Veacheslav Zilbermints Yehuda Hershkovitz Kobi Peleg Joseph J. Dubose Adi Givon David Aranovich Mickey Dudkiewicz Israeli Trauma Group Boris Kessel 《中华创伤杂志(英文版)》2021,24(3):132-135
Purpose: There is a common opinion that spinal fractures usually reflect the substantial impact of injuries and therefore may be used as a marker of significant associated injuries, specifically for intraabdominal injury (IAI). The impact of concomitant spinal cord injury (SCI) with the risk of associated IAI has not been well clarified. The aim of this study was to evaluate the incidence and severity of IAIs in patients suffering from spinal fractures with or without SCI.
Methods: A retrospective cohort study using the Israeli National Trauma Registry was conducted. Patients with thoracic, lumbar and thoracolumbar fractures resulting from blunt mechanisms of injury from January 1, 1997 to December 31, 2018 were examined, comparing the incidence, severity and mortality of IAIs in patients with or without SCI. The collected variables included age, gender, mechanism of injury, incidence and severity of the concomitant IAIs and pelvic fractures, abbreviated injury scale, injury severity score, and mortality. Statistical analysis was performed using GraphPad InStat ® Version 3.10, with Chi-square test for independence and two sided Fisher’s exact probability test.
Results: Review of the Israeli National Trauma Database revealed a total of 16,878 patients with spinal fractures. Combined thoracic and lumbar fractures were observed in 1272 patients (7.5%), isolated thoracic fractures in 4967 patients (29.4%) and isolated lumbar fractures in 10,639 patients (63.0%). The incidence of concomitant SCI was found in 4.95% (63/1272), 7.65% (380/4967) and 2.50% (266/10639) of these patients, respectively. The overall mortality was 2.5%, proving higher among isolated thoracic fracture patient than among isolated lumbar fracture counterparts (11.3% vs. 4.6%, p < 0.001). Isolated thoracic fractures with SCI were significantly more likely to die than non-SCI counterparts (8.2% vs. 3.1%, p < 0.001). There were no differences in the incidence of IAIs between patients with or without SCI
following thoracolumbar fractures overall or in isolated thoracic fractures; although isolated lumbar fractures patients with SCI were more likely to have renal (3.4% vs. 1.6%, p = 0.02) or bowel injuries (2.3% vs. 1.0%, p = 0.04) than the non-SCI counterparts.
Conclusion: SCI in the setting of thoracolumbar fracture does not appear to be a marker for associated IAI. However, in a subset of isolated lumbar fractures, SCI patient is associated with increased risks for renal and bowel injury. 相似文献