全文获取类型
收费全文 | 8746篇 |
免费 | 656篇 |
国内免费 | 33篇 |
专业分类
耳鼻咽喉 | 56篇 |
儿科学 | 256篇 |
妇产科学 | 241篇 |
基础医学 | 1472篇 |
口腔科学 | 217篇 |
临床医学 | 1013篇 |
内科学 | 1722篇 |
皮肤病学 | 190篇 |
神经病学 | 863篇 |
特种医学 | 451篇 |
外科学 | 1082篇 |
综合类 | 114篇 |
一般理论 | 3篇 |
预防医学 | 687篇 |
眼科学 | 93篇 |
药学 | 488篇 |
中国医学 | 9篇 |
肿瘤学 | 478篇 |
出版年
2023年 | 38篇 |
2022年 | 57篇 |
2021年 | 126篇 |
2020年 | 97篇 |
2019年 | 162篇 |
2018年 | 178篇 |
2017年 | 142篇 |
2016年 | 185篇 |
2015年 | 173篇 |
2014年 | 217篇 |
2013年 | 359篇 |
2012年 | 445篇 |
2011年 | 427篇 |
2010年 | 258篇 |
2009年 | 249篇 |
2008年 | 366篇 |
2007年 | 443篇 |
2006年 | 446篇 |
2005年 | 391篇 |
2004年 | 362篇 |
2003年 | 349篇 |
2002年 | 350篇 |
2001年 | 288篇 |
2000年 | 293篇 |
1999年 | 276篇 |
1998年 | 145篇 |
1997年 | 112篇 |
1996年 | 119篇 |
1995年 | 84篇 |
1994年 | 82篇 |
1993年 | 76篇 |
1992年 | 188篇 |
1991年 | 157篇 |
1990年 | 137篇 |
1989年 | 180篇 |
1988年 | 132篇 |
1987年 | 137篇 |
1986年 | 118篇 |
1985年 | 116篇 |
1984年 | 105篇 |
1983年 | 76篇 |
1982年 | 51篇 |
1981年 | 46篇 |
1980年 | 40篇 |
1979年 | 71篇 |
1978年 | 39篇 |
1977年 | 53篇 |
1975年 | 38篇 |
1974年 | 44篇 |
1971年 | 37篇 |
排序方式: 共有9435条查询结果,搜索用时 15 毫秒
41.
42.
Sybille Spicker Jörg B. Schulz Dirk Petersen Michael Fetter Thomas Klockgether Johannes Dichgans 《Journal of neurology》1995,242(8):517-521
Eye movements were studied in 13 patients with Friedreich's ataxia and correlated with MRI findings to investigate whether oculomotor abnormalities can be traced to cerebellar disturbances in this disease. One of the most prominent eye signs was fixation instability (square-wave jerks, SWJ.). Besides SWJ the patients showed various combinations of cerebellar, vestibular and brain-stem oculomotor signs. Our patients did not comprise a homogeneous group with regard to their oculomotor findings. There was no correlation between the severity of any of the so-called cerebellar oculomotor disturbances and the number of SWJ. We tried to correlate the extent of oculomotor disturbances with floccular atrophy and atrophy of the dorsal vermis on MRI in seven of the patients. None of the oculomotor features (including SWJ) correlated with flocculus or dorsal vermis size. Furthermore, floccular and vermal measurements on MRI were normal. Accordingly, we think it unlikely that the oculomotor disturbances, including SWJ, are attributable to cerebellar pathology per se. 相似文献
43.
44.
Genotype-phenotype correlation for nucleotide substitutions in the IgII- IgIII linker of FGFR2 总被引:6,自引:3,他引:3
45.
46.
Sister chromatid exchange (SCE) and chromosomal aberration studies have been used to monitor human populations for genotoxic exposure to chemical substances. These monitoring techniques involve collection of blood and/or bone marrow from the exposed subjects and culturing cells for one or two cell cycles with various treatments in culture. The results obtained from such in vivo/in vitro studies may lead to an over- or underestimation of the damage that could occur in vivo. In the present study, which uses a mouse model, the in vivo/in vitro cytogenetic assays (SCEs and chromosomal aberrations) have been compared with similar in vivo systems in bone marrow and spleen cells treated with various doses of cyclophosphamide (CPA). The results indicate a significant difference in CPA-induced cytogenetic endpoints between in vivo and in vivo/in vitro conditions in both organs. However, linear relationships were found between CPA dose and cytogenetic end point analyzed under both conditions. Based on these results it appears that the in vivo/in vitro assay is a useful technique for indicating potential in vivo damage of chemicals. 相似文献
47.
48.
Josephine Shallo-Hoffmann Dirk Watermeier Jürgen Petersen Hermann Mühlendyck 《Neurosurgical review》1988,11(2):151-158
Verification of inheritance in congenital nystagmus (CN) is only possible through the identification of more than one affected member in a family, since in a single case there are no accurate clinical differentiations between spontaneous and inherited CN. We performed electronystagmographic examinations (ENG) to search for abnormal involuntary eye movements as a sign of heredity in seemingly unaffected members of CN families.ENG registrations were performed under three test conditions: (1) with the subject fixating a target, (2) with the room lights off and (3) with closed eyes.Fifty normally sighted individuals (group (a) underwent the test procedure to provide a baseline of normality. Five CN families (three dominant, two sex-linked recessive) were tested as group (b). The eye movement recordings were analysed in terms of nystagmus intensity (amplitude x frequency of the involuntary saccade). In every one of the five families, abnormalities in seemingly non-affected members could be demonstrated: in four families, fastphase instabilities, in the fifth family a true (CN) (slowphase instability).All certain gene carriers were diagnosed correctly by the ENG.These findings indicate a method for detecting slightly affected members in dominant pedigrees and female gene carriers in sex-linked mode of transmission. 相似文献
49.
Interaction with basement membrane serves to rapidly distinguish growth and differentiation pattern of normal and malignant human breast epithelial cells. 总被引:19,自引:1,他引:18
下载免费PDF全文
![点击此处可从《Proceedings of the National Academy of Sciences of the United States of America》网站下载免费的PDF全文](/ch/ext_images/free.gif)
O W Petersen L R?nnov-Jessen A R Howlett M J Bissell 《Proceedings of the National Academy of Sciences of the United States of America》1992,89(19):9064-9068
Normal human breast epithelial cells show a high degree of phenotypic plasticity in monolayer culture and express many traits that otherwise characterize tumor cells in vivo. Paradoxically, primary human breast carcinoma cells are difficult to establish in culture: most outgrowths arise from the normal tissue surrounding the tumor. These characteristics have posed major obstacles to the establishment of simple reliable criteria for mammary epithelial transformation in culture. In the present study, we show that a reconstituted basement membrane (BM) can be used to culture all normal human breast epithelial cells and a subset of human breast carcinoma cells. The two cell types can be readily distinguished by virtue of the ability of normal cells to reexpress a structurally and functionally differentiated phenotype within BM. Twelve specimens of normal breast tissue and 2 normal breast epithelial cell lines (total 14 samples) embedded in BM as single cells were able to form multicellular spherical colonies with a final size close to that of true acini in situ. Sections of mature spheres revealed a central lumen surrounded by polarized luminal epithelial cells expressing keratins 18 and 19 and sialomucin at the apical membrane. Significantly, two-thirds of normal spheres deposited a visible endogenous type IV collagen-containing BM even though they were in contact with exogenously provided BM. Growth was arrested completely within the same time period. In contrast, none of 6 carcinoma cell lines or 2 cultures of carcinoma from fresh samples (total 8 samples) responded to BM by growth regulation, lumen formation, correct polarity, or deposition of endogenous BM. These findings may provide the basis of a rapid assay for discriminating normal human breast epithelial cells from their malignant counterparts. Furthermore, we propose that the ability to sense BM appropriately and to form three-dimensional organotypic structures may be the function of a class of "suppressor" genes that are lost as cells become malignant. 相似文献
50.
Immunomodulation by cryosurgery in malignant melanoma 总被引:1,自引:0,他引:1
U Weyer I Petersen C Ehrke A Carstensen A Nüssgen C Russ B G?ttsch L Kowalzick R Arndt E W Breitbart 《Onkologie》1989,12(6):291-296
Cryosurgery is a well-known, established method for the local destruction of tumor tissue by freezing. The assumption that, in addition to a physical and blood vascular phase, an immunological phase exists, has been discussed by many authors and tested using animal models. These results can only be transferred to humans in a limited sense. During the last year, we initiated a randomized study "Cryosurgery versus Conventional Surgery", whereby the peripheral blood and the normal skin from the areas surrounding the resection were compared. We were able to demonstrate in the peripheral blood of 8 cryosurgery patients a postoperative increase in the total and helper T-cells, HLA-DR-positive cells, and the ratio helper/suppressor T-cells in comparison to preoperative values. In the 8 patients treated with conventional surgery, these parameters decreased slightly or remained the same. The differences were highly significant (p = 0.001) to significant (p = 0.01). The results from the first 16 are patients studied presented and discussed here. 相似文献