全文获取类型
收费全文 | 2636273篇 |
免费 | 202845篇 |
国内免费 | 4987篇 |
专业分类
耳鼻咽喉 | 37833篇 |
儿科学 | 83953篇 |
妇产科学 | 76104篇 |
基础医学 | 371420篇 |
口腔科学 | 79623篇 |
临床医学 | 229353篇 |
内科学 | 512534篇 |
皮肤病学 | 58506篇 |
神经病学 | 212838篇 |
特种医学 | 105401篇 |
外国民族医学 | 879篇 |
外科学 | 404146篇 |
综合类 | 64359篇 |
现状与发展 | 9篇 |
一般理论 | 919篇 |
预防医学 | 195969篇 |
眼科学 | 62138篇 |
药学 | 199514篇 |
7篇 | |
中国医学 | 5390篇 |
肿瘤学 | 143210篇 |
出版年
2018年 | 24121篇 |
2015年 | 24315篇 |
2014年 | 33754篇 |
2013年 | 51757篇 |
2012年 | 68779篇 |
2011年 | 72703篇 |
2010年 | 43169篇 |
2009年 | 41332篇 |
2008年 | 69794篇 |
2007年 | 74666篇 |
2006年 | 75646篇 |
2005年 | 73547篇 |
2004年 | 71998篇 |
2003年 | 69439篇 |
2002年 | 68227篇 |
2001年 | 122351篇 |
2000年 | 126086篇 |
1999年 | 107403篇 |
1998年 | 29285篇 |
1997年 | 26629篇 |
1996年 | 26117篇 |
1995年 | 25108篇 |
1994年 | 23602篇 |
1993年 | 22142篇 |
1992年 | 86581篇 |
1991年 | 83953篇 |
1990年 | 82197篇 |
1989年 | 80096篇 |
1988年 | 74582篇 |
1987年 | 73421篇 |
1986年 | 70088篇 |
1985年 | 67248篇 |
1984年 | 50371篇 |
1983年 | 43255篇 |
1982年 | 25676篇 |
1981年 | 23225篇 |
1980年 | 21764篇 |
1979年 | 48285篇 |
1978年 | 34043篇 |
1977年 | 29075篇 |
1976年 | 26832篇 |
1975年 | 29317篇 |
1974年 | 35486篇 |
1973年 | 34244篇 |
1972年 | 32048篇 |
1971年 | 30135篇 |
1970年 | 28140篇 |
1969年 | 26734篇 |
1968年 | 24861篇 |
1967年 | 22386篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
The case report presents a 25-year-old woman who got pregnant twice in 1 year. Both pregnancies were terminated after ultrasound examination demonstrated limb abnormalities. Radiological and pathological examinations showed diastrophic dysplasia, a rare form of an osteochondrodysplasia with autosomal recessive inheritance. Here the histopathological findings in the cartilage and prenatal diagnosis by ultrasound are discussed. 相似文献
972.
Figure-Ground Segregation at Contours: a Neural Mechanism in the Visual Cortex of the Alert Monkey 总被引:1,自引:0,他引:1
An important task of vision is the segregation of figure and ground in situations of spatial occlusion. Psychophysical evidence suggests that the depth order at contours is defined early in visual processing. We have analysed this process in the visual cortex of the alert monkey. The animals were trained on a visual fixation task which reinforced foveal viewing. During periods of active visual fixation, we recorded the responses of single neurons in striate and prestriate cortex (areas V1, V2, and V3/V3A). The stimuli mimicked situations of spatial occlusion, usually a uniform light (or dark) rectangle overlaying a grating texture of opposite contrast. The direction of figure and ground at the borders of these rectangles was defined by the direction of the terminating grating lines (occlusion cues). Neuronal responses were analysed with respect to figure-ground direction and contrast polarity at such contours. Striate neurons often failed to respond to such stimuli, or were selective for contrast polarity; others were non-selective. Some neurons preferred a certain combination of figure-ground direction and contrast polarity. These neurons were rare both in striate and prestriate cortex. The majority of neurons signalled figure-ground direction independent of contrast polarity. These neurons were only found in prestriate cortex. We explain these responses in terms of a model which also explains neuronal signals of illusory contours. These results suggest that occlusion cues are used at an early level of processing to segregate figure and ground at contours. 相似文献
973.
Congenital intermaxillary fusion is a rare anomaly. Combination of the anomaly with any type of facial cleft is extremely rare. Death in a majority of these patients as a result of feeding and aspiration problems in early life may have caused the reports to be limited. In this article a 5-year-old patient, probably the first in the literature having Tessier type VI-VII facial cleft combination associated with bimaxillary fusion and anophthalmia on the right side, is presented. The patient has survived on fluid meal through a very small opening for 5 years. The features of the case are presented, and the time and method of the management of such a rare anomaly are discussed with a review of the literature. 相似文献
974.
M. NEUBRAND I. GREINWALD H. LOBENTANZER G. PAUMGARTNER H. HERMEKING T. SAUERBRUCH 《European journal of clinical investigation》1997,27(3):234-241
Efficient fragmentation is the most important prerequisite for successful treatment of gallstones by extracorporeally induced shock waves. No data are available on the amount of energy necessary for stone disintegration and on the threshold energy below which no further fragmentation occurs. We therefore performed an in vitro investigation on human cholesterol gallstones to elucidate physical laws governing shock-wave lithotripsy. First, the focal pressure of the lithotripter was measured to calculate the energy traversing a stone. Second, 96 gallstones from 16 gall bladders were analysed with respect to physicochemical composition, radiological features and ultrasound before fragmentation was performed. Energy for stone disintegration was constant within each stone family but varied between 4.6 J mL?1 and 36.8 J mL?1 in different families. This energy correlated linearly with stone volume. None of the radiological and physicochemical factors revealed a clear-cut correlation of the different energies necessary for similar stone disintegration. The threshold energy differed between 0.26 mJ and 1.04 mJ per pulse. In conclusion, stone volume was the best parameter predicting stone fragmentation. However, in cholesterol stones with a similar composition the required energy per volume varies considerably together with the threshold energy. Radiological and ultrasound parameters appear to be of minor importance in explaining these differences. 相似文献
975.
Inflammatory bowel disease: re-evaluation of the diagnosis in a prospective population based study in south eastern Norway. 总被引:1,自引:0,他引:1
BACKGROUND: The incidence figures for ulcerative colitis (UC) and Crohn's disease (CD) have been difficult to interpret, and geographical variations may be due to differences in classification criteria and study design. Few studies have based the incidence on prospective systematic follow up to confirm the initial diagnosis. METHODS: Between 1990 and 1993, in a prospective incidence study of inflammatory bowel disease (IBD) in south eastern Norway, 527 cases of UC, 228 cases of CD, 36 cases of indeterminate colitis (IND), and 55 cases of possible IBD were identified, yielding an annual incidence of 13.6, 5.9, 0.9, and 1.4 per 10(5) respectively. The diagnosis and all clinical data were reviewed by two gastroenterologists independently of each other. One to two years after diagnosis, all patients were offered a clinical follow up in which the initial diagnosis was assessed. RESULTS: Between the time of diagnosis and the follow up, 16 patients had died, four of complications related to IBD. Of the remaining 830 patients, 98% (814/830) were available for follow up, 93% (772/830) attended a clinical examination which included a colonoscopy in 77% (637/830), and the remainder had had a telephone interview, or reassessment based on hospital records, or both. Twenty seven patients were reclassified as not having IBD (3%), and 65 patients were characterised as possible IBD (8%). Of the patients initially classified as UC, 88% had their diagnosis confirmed, compared with 91% with an initial diagnosis of CD. In patients with indeterminate colitis, 33% were classified as definite UC and 17% as CD. This reclassification of patients yielded a corrected annual incidence of 12.8 for UC and 6.0 for CD. CONCLUSION: At follow up one to two years after the diagnosis of IBD, the initial incidence was only marginally altered. This is probably due to uniform inclusion criteria and careful diagnostic methods. The study also illustrates the importance of the re-evaluation of the initial diagnosis as close to 10%, both among patients with UC and CD, were reclassified at follow up. 相似文献
976.
977.
An indirect immunofluorescence assay using a cell culture-derived antigen for detection of antibodies to the agent of human granulocytic ehrlichiosis. 总被引:18,自引:11,他引:7 下载免费PDF全文
W L Nicholson J A Comer J W Sumner C Gingrich-Baker R T Coughlin L A Magnarelli J G Olson J E Childs 《Journal of clinical microbiology》1997,35(6):1510-1516
An indirect immunofluorescence assay for the detection of human antibodies to the agent of human granulocytic ehrlichiosis (HGE) was developed and standardized. Antigen was prepared from a human promyelocytic leukemia cell line (HL-60) infected with a tick-derived isolate of the HGE agent (USG3). Suitable antigen presentation and preservation of cellular morphology were obtained when infected cells were applied and cultured on the slide, excess medium was removed, and cells were fixed with acetone. Use of a buffer containing bovine serum albumin and goat serum reduced background fluorescence, and use of an immunoglobulin G (gamma-specific) conjugate reduced nonspecific binding. The assay readily detected specific antibody from HGE patients and did not detect antibody from healthy individuals. No significant reactivity was noted in sera from patients with high titers of antibodies to other rickettsial species. We were able to identify antibodies reactive to USG3 antigen in samples from areas where HGE is endemic that had tested negative to other rickettsial agents. Animal sera reactive against Ehrlichia equi or Ehrlichia phagocytophila bound to the HGE antigen, indicating that the assay may be useful for veterinary use. Comparability between two different laboratories was assessed by using coded human sera exchanged between laboratories. Results from the two laboratories were similar, indicating that the assay can be easily integrated into use for routine testing for HGE. The assay was then compared to an assay using horse neutrophils infected with ehrlichiae. The two assays gave comparable results, indicating that the cell culture-derived antigen can be used for testing samples that have been previously tested with E. equi as an antigen. The new assay offers several advantages over other immunofluorescence methods that use animal-derived antigen and is suitable for use in testing for human antibodies to the HGE agent. 相似文献
978.
While the benefits of training manuals can hardly be questioned, they are exceedingly limited in reducing variability attributed to the "therapist factor." We propose that manuals provide a useful outline of the general principles of a therapeutic approach, but can only reduce therapist variability at the expense of other essential therapeutic phenomena. Manuals cannot adequately convey, for example, how the effective therapist functions as a model of adult living and as a person who provides guidance. We suggest that such an experience cannot readily be packaged in manualized form, though manuals may serve as a useful beginning. Recommendations for therapist manualized training include greater attention to the subtleties of human relationships and adequately conveying that any technique is effective only when catalysed by a living, relational process. 相似文献
979.
M. D. Mashkovskii V. A. Parshin R. B. Parimbetova 《Bulletin of experimental biology and medicine》1997,123(3):257-259
It is found that the cholinomimetic aceclidine stimulates learning and memory processes and exerts antiamnestic effect in
rats with conditioned avoidance reaction. The effect of aceclidine is not inferior to that of amiridin and surpasses that
of physostigmine.
Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 123, No. 3, pp. 296–298, March, 1997 相似文献
980.