全文获取类型
收费全文 | 2272篇 |
免费 | 216篇 |
国内免费 | 2篇 |
专业分类
耳鼻咽喉 | 22篇 |
儿科学 | 74篇 |
妇产科学 | 37篇 |
基础医学 | 318篇 |
口腔科学 | 39篇 |
临床医学 | 267篇 |
内科学 | 522篇 |
皮肤病学 | 40篇 |
神经病学 | 145篇 |
特种医学 | 174篇 |
外科学 | 267篇 |
综合类 | 48篇 |
预防医学 | 213篇 |
眼科学 | 17篇 |
药学 | 188篇 |
中国医学 | 1篇 |
肿瘤学 | 118篇 |
出版年
2022年 | 16篇 |
2021年 | 50篇 |
2020年 | 26篇 |
2019年 | 31篇 |
2018年 | 48篇 |
2017年 | 42篇 |
2016年 | 26篇 |
2015年 | 47篇 |
2014年 | 62篇 |
2013年 | 100篇 |
2012年 | 90篇 |
2011年 | 108篇 |
2010年 | 65篇 |
2009年 | 81篇 |
2008年 | 91篇 |
2007年 | 105篇 |
2006年 | 87篇 |
2005年 | 79篇 |
2004年 | 96篇 |
2003年 | 65篇 |
2002年 | 70篇 |
2001年 | 42篇 |
2000年 | 58篇 |
1999年 | 54篇 |
1998年 | 43篇 |
1997年 | 56篇 |
1996年 | 53篇 |
1995年 | 46篇 |
1994年 | 40篇 |
1993年 | 42篇 |
1992年 | 48篇 |
1991年 | 35篇 |
1990年 | 34篇 |
1989年 | 45篇 |
1988年 | 39篇 |
1987年 | 38篇 |
1986年 | 39篇 |
1985年 | 33篇 |
1984年 | 27篇 |
1983年 | 22篇 |
1981年 | 20篇 |
1980年 | 15篇 |
1979年 | 18篇 |
1978年 | 19篇 |
1977年 | 24篇 |
1976年 | 25篇 |
1975年 | 20篇 |
1974年 | 17篇 |
1973年 | 16篇 |
1968年 | 15篇 |
排序方式: 共有2490条查询结果,搜索用时 0 毫秒
1.
Nonocclusive mesenteric ischemia (NOMI) is a disorder with an extremely high mortality. Salvage of affected patients requires early recognition and aggressive intervention to prevent intestinal gangrene. Dialysis patients represent a group at particularly high risk for this condition. Clinicians should develop a high index of suspicion for NOMI in dialysis patients to lessen the risk of death. A high interventional posture must be maintained due to the notoriously unreliable signs and symptoms of this disorder. 相似文献
2.
BACKGROUND: There are obvious advantages to increasing donor retention. However, for reasons of blood safety, certain donors may, in fact, be more desirable to retain than others. “Safe” donors are defined as those who provided a blood donation that was negative on all laboratory screening tests and who subsequently reported no behavioral risks in response to an anonymous survey. This study identifies the most important factors affecting the intention of “safe” donors to provide another donation. STUDY DESIGN AND METHODS: An anonymous survey asking about donation history, sexual history, injecting drug use, and recent donation experience was mailed to 50,162 randomly selected allogeneic donors (including directed donors) who gave blood from April through July or from October through December 1993 at one of the five United States blood centers participating in the Retrovirus Epidemiology Donor Study. Before mailing, questionnaires were coded to designate donors with nonreactive laboratory screening tests at their most recent donation. RESULTS: A total of 34,726 donors (69%) responded, with substantially higher response among repeat donors. According to reported intentions only, the vast majority of “safe” donors indicated a high likelihood of donating again within the next 12 months. Only 3.4 percent reported a low likelihood of donating again. A comparison of those likely to return and those unlikely to return reveals significant differences in demographics and in ratings of the donation experience. A higher proportion of those unlikely to return were first-time donors, minority-group donors, and donors with less education. The highest projected loss among “safe” donors was seen for those who gave a fair to poor assessment of their treatment by blood center staff or of their physical well-being during or after donating. CONCLUSION: These data suggest that efforts to improve donors' perceptions of their donation experience, as well as attention to the physical effects of blood donation, may aid in the retention of both repeat and first-time donors. 相似文献
3.
Comparative testicular toxicity of bis(2-methoxyethyl) ether and 2-methoxyethanol in rats 总被引:2,自引:0,他引:2
Male rats were exposed to 0, 110, 370, or 1100 ppm bis(2-methoxyethyl)ether (diglyme) 6 h/day, 5 days/week for 2 weeks. One group of male rats was exposed to 300 ppm 2-methoxyethanol (2-ME) for 2 weeks as a positive control. Exposed rats were killed after 10 days of exposure and 14, 42, or 84 days post-exposure (PE), respectively. At 110 ppm diglyme, spermatocytes in pachytene and meiotic division at spermatogenic stages XII-XIV were mainly affected. At 370 ppm diglyme, affected germ cells were similar to those seen at 110 ppm diglyme, but round spermatids at spermatogenic stages I-VII were also affected. The testes regained normal spermatogenesis by 84 days PE. At 1100 ppm diglyme or 300 ppm 2-ME, marked testicular atrophy was found affecting all spermatogenic stages. Damaged seminiferous tubules were lined with regenerating pachytene spermatocytes at 14 days PE and with spermatocytes and round spermatids after 42 days PE. Most but not all testes in rats exposed to 300 ppm 2-ME or 1100 ppm diglyme had normal morphology after 84 days PE. Based on the observation of germ cell damage, spermatozoa population in the epidymal tubules, reversibility of spermatogenesis after various PE periods, testicular toxicity induced by 300 ppm 2-ME was more severe than that seen at 370 ppm diglyme but was slightly less remarkable than that of 1100 ppm diglyme. 相似文献
4.
Clare Bradley Rosalind Plowright John Stewart John Valentine Elke Witthaus 《Health and quality of life outcomes》2007,5(1):57
Background
The results of using status measures to identify any changes in treatment satisfaction strongly suggest a need for specific change instruments designed to overcome the ceiling effects frequently observed at baseline. Status measures may leave little room to show improvement in situations where baseline ceiling effects are observed. A change version of the DTSQ (DTSQc) is compared here with the original status (now called DTSQs) version to test the instruments' comparative ability to demonstrate change. 相似文献5.
D A Frambach C E Roy J L Valentine S F Boles J J Weiter C L Schepens 《Ophthalmic surgery》1988,19(2):98-100
The prevalence of cardiovascular disease (by EKG criteria) in patients with rhegmatogenous retinal detachments has been reported to be more than four times that found in age-matched controls. Adhesion between the retinal pigment epithelium (RPE) and the photoreceptors is facilitated by RPE transport. Because RPE transport is driven by a Na-K ATPase, it has been suggested that the correlation of EKG abnormalities and retinal detachment may be due to clinical use of digoxin, a Na-K ATPase inhibitor frequently given to patients with cardiovascular disease. The prevalence of EKG abnormalities in 299 consecutive patients with primary retinal detachment is about the same as that reported previously. However, 92% of these patients with EKG abnormalities did not take digoxin. Therefore, clinical use of digoxin cannot account for the reported association of EKG abnormalities and rhegmatogenous retinal detachment. 相似文献
6.
Nemaline myopathy of cats 总被引:2,自引:0,他引:2
An apparently inherited myopathy, characterized by the presence of large numbers of nemaline rods in skeletal muscle fibers, was investigated in five cats. Onset of signs varied from 6 months to 1.5 years of age and consisted of reluctance to move, jerky gait and muscle twitching, hyporeflexia, and muscle wasting, which was most prominent in the proximal muscles of the forelimbs. All of the cats, three males and two females, were from the same dam. In addition to the presence of rods, the myopathy was characterized by marked fiber size variation, with atrophy of type 1 and type 2a muscle fibers. In addition, there was infolding of the sarcolemma and fiber splitting. Ultrastructurally, the rods closely resembled those described in human nemaline myopathy. 相似文献
7.
David Salonen M.D. FRCP Donald Resnick M.D. Sabina M. Valentine 《Skeletal radiology》1994,23(6):454-454
8.
Sylvester Valentine Fernandes 《Otolaryngology--head and neck surgery》2003,128(2):267-272
OBJECTIVES: The study goal was to assess the success rate and efficacy of a myringoplasty (tympanoplasty type I) technique using a composite chondroperichondrial graft in a combined overlay-underlay fashion. STUDY DESIGN: A retrospective analysis of patients subjected to the technique was conducted. METHODS: A sample of 15 patients who met the inclusion criteria were reviewed for surgical results. All patients were treated by a single surgeon. RESULTS: This transcanal technique provides minimal morbidity and excellent results in selected patients. CONCLUSIONS: The described technique provides an effective method of closing nonmarginal perforations of the tympanic membrane. 相似文献
9.
Steenbergen EJ; Verhagen OJ; van Leeuwen EF; van den Berg H; von dem Borne AE; van der Schoot CE 《Blood》1995,86(2):692-702
Crosslineage T-cell receptor delta (TCR delta) rearrangements are widely used as tumor markers for the follow up of minimal residual disease in childhood B-precursor acute lymphoblastic leukemia (ALL) by polymerase chain reaction (PCR). The major drawback of this approach is the risk of false-negative results due to clonal evolution. We investigated the stability of V delta 2D delta 3 rearrangements in a group of 56 childhood B-precursor ALL patients by PCR and Southern blot analysis. At the PCR level, V delta 2D delta 3-to-J alpha rearranged subclones (one pathway for secondary TCR delta recombination) were demonstrated in 85.2% of V delta 2D delta 3-positive patients tested, which showed that small subclones are present in the large majority of patients despite apparently monoclonal TCR delta Southern blot patterns. Sequence analysis of V delta 2D delta 3J alpha rearrangements showed a biased J alpha gene usage, with HAPO5 and J alpha F in 26 of 32 and 6 of 32 clones, respectively. Comparison of V delta 2D delta 3 rearrangement status between diagnosis and first relapse showed differences in seven of eight patients studied. In contrast, from first relapse onward, no clonal changes were observed in six patients studied. To investigate the occurrence of crosslineage TCR delta rearrangements in normal B and T cells, fluorescence-activated cell sorter-sorted peripheral blood CD19+/CD3- and CD19-/CD3+ cell populations from three healthy donors were analyzed. V delta 2D delta 3 rearrangements were detected at low frequencies in both B and T cells, which suggests that V delta 2-to-D delta 3 joining also occurs during normal B-cell differentiation. A model for crosslineage TCR delta rearrangements in B-precursor ALL is deduced that explains the observed clonal changes between diagnosis and relapse and is compatible with multistep leukemogenesis of B-precursor ALL. 相似文献
10.
AE Castellano G Micieli P Bellantonio MG Buzzi S Marcheselli F Pompeo F Rossi G Nappi 《Cephalalgia : an international journal of headache》1998,18(9):622-630
Intracerebral vascular reactivity induced by the nitric oxide (NO) donor isosorbide dinitrate (IDN, 5 mg sublingually) is more major and longer-lasting in migraine patients who develop delayed headache in response to the drug. The headache is purportedly due to neuronally-mediated vascular mechanisms. Indomethacin inhibits prostaglandin synthesis, which is involved in NO generation. Indomethacin also decreases cerebral blood flow by constricting precapillary resistance vessels. In the present study, the hemodynamic effects of indomethacin were evaluated in migraine patients and healthy controls by means of transcranial Doppler monitoring. Indomethacin caused a significant decrease in mean flow velocity in the middle cerebral artery. This was an additional effect to the mean velocity decrease induced by IDN. The interactions between the two drugs suggest that their effects on cerebral hemodynamics (and pain) may be of relevance both in understanding the role of NO in migraine pathogenesis and in evaluating symptomatic treatments for migraine attacks. 相似文献