全文获取类型
收费全文 | 23731篇 |
免费 | 1570篇 |
国内免费 | 144篇 |
专业分类
耳鼻咽喉 | 293篇 |
儿科学 | 470篇 |
妇产科学 | 448篇 |
基础医学 | 3377篇 |
口腔科学 | 485篇 |
临床医学 | 2145篇 |
内科学 | 5516篇 |
皮肤病学 | 306篇 |
神经病学 | 2374篇 |
特种医学 | 958篇 |
外科学 | 3077篇 |
综合类 | 232篇 |
一般理论 | 49篇 |
预防医学 | 1895篇 |
眼科学 | 918篇 |
药学 | 1420篇 |
中国医学 | 35篇 |
肿瘤学 | 1447篇 |
出版年
2023年 | 100篇 |
2022年 | 219篇 |
2021年 | 494篇 |
2020年 | 280篇 |
2019年 | 400篇 |
2018年 | 502篇 |
2017年 | 364篇 |
2016年 | 427篇 |
2015年 | 489篇 |
2014年 | 693篇 |
2013年 | 947篇 |
2012年 | 1428篇 |
2011年 | 1595篇 |
2010年 | 870篇 |
2009年 | 824篇 |
2008年 | 1409篇 |
2007年 | 1483篇 |
2006年 | 1308篇 |
2005年 | 1407篇 |
2004年 | 1241篇 |
2003年 | 1183篇 |
2002年 | 1156篇 |
2001年 | 299篇 |
2000年 | 278篇 |
1999年 | 317篇 |
1998年 | 254篇 |
1997年 | 264篇 |
1996年 | 209篇 |
1995年 | 183篇 |
1994年 | 134篇 |
1993年 | 138篇 |
1992年 | 199篇 |
1991年 | 178篇 |
1990年 | 188篇 |
1989年 | 136篇 |
1988年 | 151篇 |
1987年 | 146篇 |
1986年 | 158篇 |
1985年 | 156篇 |
1984年 | 164篇 |
1983年 | 169篇 |
1982年 | 161篇 |
1981年 | 181篇 |
1980年 | 156篇 |
1979年 | 129篇 |
1978年 | 113篇 |
1977年 | 109篇 |
1975年 | 117篇 |
1974年 | 109篇 |
1973年 | 123篇 |
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
91.
Existing knowledge and present experience relating to the indications for imaging techniques in trauma surgery were summarised, screened and considered in different ways by representatives of various professional scientific bodies, with the aim of finding what procedures should be implemented as the primary examination techniques after a careful clinical examination when particular posttraumatic situations affecting the knee, foot, ankle, or hand were found. In the course of an interdisciplinary consensus conference the evidence-based recommendations prepared by a panel were discussed and modified, giving rise to statements on the suitability of the given imaging techniques in 28 different clinical situations immediately after a clinical examination, based on scientific evidence and medical consensus. The degree of consensus was measured and carefully documented. These statements were transformed into decision algorithms and presented to doctors working in accident and emergency medicine during a conference on trauma surgery, with the aim of.measuring the acceptance of the statements among those attending the trauma surgery meeting. The remarks made by the participants during the discussion and the results of the acceptance measurements clearly show the need for further discussion among experts. 相似文献
92.
Christine A. Ellis Susan F. Brooks Gavin Brooks A. Tudor Evans Nicholas Morrice Fred. J. Evans Alastair Aitken 《Phytotherapy research : PTR》1987,1(4):187-190
The sapintoxins are a series of naturally occurring fluorescent phorbol esters with a range of selective biological activities (e.g. pro-inflammatory but non-tumour promoting). Their ability to activate protein kinase C (PKC) in vitro has been studied. Both tumour promoting and non-promoting phorbol derivatives activate the enzyme in vitro at low concentrations. 12-deoxyphorbol-13-phenylacetate-20 acetate (DOPPA) acts as a partial agonist in the activation of protein kinase C. Structurally distinct phorbol esters may therefore preferentially activate different forms of protein kinase C. α-sapinine, a biologically inactive compound, binds to protein kinase C without stimulating the enzyme and prevents subsequent activation by phorbol esters such as 12-O-tetradecanoyl phorbol-13-acetate (TPA). 相似文献
93.
Marelise E M W Eekhoff Marjolein van der Klift Herman M Kroon Cyrus Cooper Albert Hofman Huibert A P Pols Socrates E Papapoulos 《Journal of bone and mineral research》2004,19(4):566-570
Serum ALP may be a good indicator of Paget's disease in epidemiologic studies. Subjects with raised and normal ALP from a population cohort were matched (1 in 6, total 548), and radiographs were taken. ALP was an excellent marker of the disease (RR, 10.9), but the majority of those affected had normal ALP. INTRODUCTION: Evidence from radiographic surveys of limited skeletal sites has shown that Paget's disease of bone (PDB) is common in the elderly and has a distinct geographic variation. There is no information, however, about the relation of serum alkaline phosphatase (ALP) activity, a marker of the disease, and its prevalence in the population. MATERIALS AND METHODS: We analyzed data from a well-defined Dutch population cohort (the Rotterdam study) with the following specific aims: (1) to assess the relationship between serum ALP activity and prevalence of radiographically diagnosed PDB, (2) to estimate the overall prevalence of the disease in the Netherlands, and (3) to assess the appearance of the disease with time. Using a nested case-control design, subjects with an increased serum ALP and normal serum liver enzymes were matched for gender and age (1 to 6) with subjects with normal serum ALP activity. Radiographs of the thoracic and lumbar spine, pelvis, proximal femurs, knees, wrists, and hands were taken. RESULTS AND CONCLUSIONS: PDB was diagnosed in 20.5% of subjects with elevated serum ALP activity and in 2.3% in those with normal serum ALP activity, increasing with age in both groups. The relative risk (RR) for PDB in the presence of raised serum ALP activity was 10.9 (95% CI, 4.8, 24.9). The estimated prevalence of PDB in the population was 3.6%, and the large majority (about 86%) had normal serum ALP activity, contrasting findings in bone clinics where the opposite is the case. Finally, in subjects with normal and raised serum ALP activity but no PDB at baseline, radiographs taken 6-9 years later showed no evidence of the disease. This study demonstrated that serum ALP activity is a sensitive marker of PDB in men and women >55 years of age, but the majority of those affected have normal serum ALP activity. 相似文献
94.
Resorption rate and biocompatibility characteristics of two polyester ventilation tubes in a guinea pig model 总被引:5,自引:0,他引:5
Becky L. Massey MD Xuejun Wen PHD L. Ralph Rohr MD Patrick A. Tresco PHD Lisa Dahlstrom MS Albert H. Park MD 《Otolaryngology--head and neck surgery》2004,131(6):921-925
OBJECTIVES: Determine the resorption rate and biocompatibility characteristics of 2 polyester ventilation tubes, and to determine whether soap and water exposure accelerates polyester tube degradation. STUDY DESIGN AND SETTING: 50/50 poly (D, L-lactide-co-glycolide; PLGA-50) and poly (L-lactide; PLA) polymers were placed into the tympanic membranes of Hartley pigmented guinea pigs. Integrity of the tubes was determined by weekly otoscopic examination. Biocompatibility was assessed by comparing auditory brainstem response (ABR) thresholds and by examining tympanic membrane changes following tube resorption. Shah minigrommet ventilation tubes were used as controls. In the second portion of this study, implanted PLGA-50 and PLA tubes were exposed weekly to a mixture of soap and water (1:5) until complete resorption was observed. Biocompatibility was assessed by periodic ABR testing and tympanic membrane examination. RESULTS: The PLA tubes remained in the tympanic membrane for a longer period (63.2 +/- 19.3 days) than the PLGA-50 (18.8 +/- 8.1 days). The tympanic membrane and resorbable tube interface demonstrated equivalent findings for auditory thresholds and tissue histopathology at the implant site compared to nonresorbable controls. The resorption behavior was not altered by exposure to soap and water. Tympanic membranes of all animals following tube degradation and soap water exposure were intact with minimal scarring and no signs of persistent foreign body response. The histological analysis showed that implantation of resorbable tubes was not accompanied by secondary infection with otorrhea through the tube, did not result in a permanent perforation or dislocation of the tube into the middle ear cavity, and was not followed by excess tympanosclerosis or localized or diffuse membrane atrophy. CONCLUSIONS AND SIGNIFICANCE: Resorbable polyester pressure equalization tubes demonstrate predictable resorption behavior and similar biocompatibility characteristics when compared with nonresorbable Shah minigrommet ventilation tubes. Exposure to soap water does not accelerate polyester tube degradation nor change the host tissue response during the indwelling period or after complete resorption. The data suggests that resorbable ventilation tubes are substantially equivalent to other FDA-approved tympanostomy devices with regard to safety and biocompatibility in the guinea pig model examined and may provide improved clinical performance by combining this approach with sustained release technology. EBM RATING: B-2. 相似文献
95.
Modic changes following lumbar disc herniation 总被引:4,自引:3,他引:1
Only a small proportion (20%) of patients with LBP can be diagnosed based on a patho-anatomical entity. Therefore, the identification
of relevant subgroups, preferably on a patoanatomical basis, is strongly needed. Modic changes have been described by several
authors as being closely linked with LBP. The aims of this study were to describe the prevalence of Modic changes, their development
as well as their association to LBP, previous disc contour, and surgery in patients with previous severe sciatica. This is
a longitudinal cohort study where the patients were recruited from an RCT comparing two active conservative treatments, the
181 patients, who at baseline had radicular pain in or below the knee; all underwent a physical examination and MRI. MRI’s,
pain history and physical examination of 166 patients were obtained at follow-up 14 months later. The prevalence of Modic
changes type 1 increased from 9% at baseline to 29% at follow-up. At that time, a strong association between Modic changes
and non-specific LBP was noted. Apparently, Modic changes type 1 was more strongly associated with non-specific lumbar pain
than Modic changes type 2. The development of new Modic changes was closely related to the level of a previous disc herniation.
A lumbar disc herniation is a strong risk factor for developing Modic changes (especially type 1) during the following year.
Furthermore, Modic changes are strongly associated with LBP. 相似文献
96.
Fibroblast radiosensitivity and intraocular fibrovascular proliferation following radiotherapy for bilateral retinoblastoma. 下载免费PDF全文
D M Albert D S Walton R R Weichselbaum J R Cassady J B Little D Leombruno R Trantravahi C A Puliafito 《The British journal of ophthalmology》1986,70(5):336-342
A 5-day-old female patient was found to have large hereditary retinoblastomas in the posterior pole of each eye. The patient received radiation treatment over a 39-day period, with each retina receiving 4600 rad. Two weeks after the complete treatment the tumours had regressed to approximately one-quarter of their original size. By 14 weeks following completion of radiotherapy the patient had developed in each eye extensive iris neovascularisation with progressive closure of the filtration angles, secondary glaucoma, and retinal detachments resulting from fibrovascular proliferation on the retinal surface. Radiosensitivity studies were from separate conjunctival biopsies obtained before and after radiation. These showed a D0 (calculated survival curve parameters, defined in the Methods section) in the exponential growth phase of 110 prior to radiation and a postirradiation exponential growth phase D0 of 70. Karotype studies showed several chromosomal abnormalities following radiotherapy. The clinical course and pathology findings are thought to represent an unusually severe orbital and ocular response to radiation therapy. These findings are consistent with our hypothesis that some patients with hereditary retinoblastoma may have a defect in the accumulation repair of x-irradiation induced DNA damage. 相似文献
97.
K M Harris D L Morris R Tudor P Toghill J D Hardcastle 《The British journal of surgery》1986,73(10):835-838
The advances of hydatid chemotherapy and the non-operative management of simple (epithelial) hepatic cysts make a correct diagnosis of increasing importance. Twenty-six patients with hepatic hydatid cysts and eleven with simple cysts were reviewed. In both groups clinical presentation was most frequently due to pain. Sex, age and size of the cysts were similar. Hydatid serology was negative in six of the hydatid patients (23 per cent). None of the simple cyst patients had positive serology but one had a borderline titre. Ultrasound and computerized tomography identified daughter cysts within the main cyst in only 17 hydatid cysts (65 per cent) and considerable intra-cyst debris was also present in five of the simple cysts. Seven of the simple cysts were deroofed surgically and the remainder underwent percutaneous aspiration. Sixteen of the hydatid cysts were found to have a biliary communication whereas this was not found with any simple cyst. The difficulties in making a precise diagnosis in some patients with a liver cyst should deter the interventional radiologist and restrain the hydatid chemotherapist. 相似文献
98.
Schjelderup Lise Kozlowski Michael R. Weissman Albert Aasen Arne J. 《Pharmaceutical research》1988,5(4):236-237
The (R)-( + )- and (S)-( – )-enantiomers of the anticholinergic compound, oxyphencyclimine, were synthesized from (R)-( – )- and (S)-( + )-2-cyclohexyl-2-hydroxy-2-phenylethanoic acid, respectively. The potencies of the enantiomers were compared using a cholinergic receptor binding assay. The (R)-( + )-enantiomer inhibited binding 29 times more potently than the (S)-( – )-enantiomer. 相似文献
99.
100.
Albert Kingman PhD 《Journal of public health dentistry》1992,52(6):353-360
Statistical issues associated with demonstrating significance between treatment groups (efficacy or superiority) and nonsignificance (equivalence) are presented and discussed. Methodologies for demonstrating efficacy of a product are proposed and contrasted, incorporating clinical and statistical criteria, with emphasis on situations in which placebo groups are precluded from the study design. Distinctions are drawn between study designs for demonstrating superiority and those for equivalence, including the determination of sample sizes needed for the different approaches. The "at least as good as" criterion is proposed as a reasonable alternative to that of equivalence in active control equivalence studies for demonstrating that dental product modifications or new products are efficacious. 相似文献