首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   600篇
  免费   27篇
  国内免费   13篇
儿科学   39篇
妇产科学   15篇
基础医学   53篇
口腔科学   15篇
临床医学   73篇
内科学   111篇
皮肤病学   7篇
神经病学   25篇
特种医学   146篇
外科学   30篇
综合类   6篇
预防医学   24篇
眼科学   52篇
药学   18篇
肿瘤学   26篇
  2021年   8篇
  2020年   3篇
  2019年   13篇
  2018年   5篇
  2017年   5篇
  2016年   6篇
  2015年   14篇
  2014年   12篇
  2013年   10篇
  2012年   15篇
  2011年   9篇
  2010年   19篇
  2009年   14篇
  2008年   15篇
  2007年   22篇
  2006年   16篇
  2005年   12篇
  2004年   14篇
  2003年   16篇
  2002年   17篇
  2001年   11篇
  2000年   27篇
  1999年   12篇
  1998年   29篇
  1997年   41篇
  1996年   29篇
  1995年   21篇
  1994年   22篇
  1993年   11篇
  1992年   14篇
  1991年   6篇
  1990年   10篇
  1989年   15篇
  1988年   14篇
  1987年   5篇
  1986年   16篇
  1985年   9篇
  1984年   5篇
  1983年   19篇
  1982年   9篇
  1981年   7篇
  1980年   8篇
  1979年   6篇
  1978年   11篇
  1977年   16篇
  1976年   8篇
  1975年   7篇
  1974年   2篇
  1973年   2篇
  1970年   1篇
排序方式: 共有640条查询结果,搜索用时 850 毫秒
1.
The Video Display Terminal Eye Clinic was designed to relieve the symptoms of video display terminal users by diagnosing and treating visual problems and by analyzing the patients' work station environment through an in-office simulation and making suggestions for improvements. The Clinic was open to the public and patients were therefore self-selected. The symptoms, diagnoses, and treatments were compiled retrospectively and reported for 153 patients. Vision problems were diagnosed in most patients. The most frequent diagnoses included: presbyopia, improper spectacle design for presbyopia, accomodative deficiencies, esophoria, exophoria, and hyperopia. The results suggest that proper visual care and work station arrangement can improve comfort.  相似文献   
2.
3.
Abdominal abnormalities in AIDS: detection at US in a large population   总被引:1,自引:0,他引:1  
  相似文献   
4.
5.
A comparison of Skirrow's, Butzler's, Blaser's, Campy-BAP and Preston media for Campylobacter spp was made using human, animal and environmental specimens. Butzler's medium gave the lowest isolation rate and Preston medium, which was the most selective, the highest isolation rate. Enrichment culture using Preston enrichment broth gave a higher isolation rate than direct plating onto Preston medium.  相似文献   
6.
A 77-year-old woman with neurofibromatosis type 1 presented with ill-fitting dentures due to intraoral extension of a right temporal fossa mass. Computed tomographic scanning demonstrated that the masticator space mass bowed the zygomatic arch and remodeled the lateral orbit and maxillary sinus walls, findings that were consistent with the clinical diagnosis of a neurofibroma with possible malignant transformation. However, light microscopic, immunohistochemical, and ultrastructural examination of tissue from an incisional biopsy specimen were diagnostic of meningioma. This case illustrates that the clinicopathologic differential diagnosis of an enlarging mass in patient with neurofibromatosis should include sporadic, unrelated neoplasms as well as tumors known to be associated with the syndrome.  相似文献   
7.
The increasing trend of utilizing nonprofessional personnel in community mental health has led to considerable controversy. It is suggested that studies comparing the relative competence and efficacy of professional therapists to that of nonprofessional therapists may be counterproductive and in need of augmentation. The present study employed a role perception procedure in which members of three different randomly chosen groups (11 professional therapists, 11 nonprofessional therapists, and 11 children-clients) from a community mental health program were asked to rank various aspects of the therapeutic relationship in order of importance to the children-clients' improvement. It was hypothesized that (a) due to their relatively low self-concept, nonprofessionals would underestimate their own role importance in comparison to that of the professionals; (b) professionals would overestimate their own role importance; and (c) children would selectively value certain aspects of each role without preferring one over the other. The last two hypotheses were supported, but the first hypothesis was not: nonprofessionals, in fact, showed the highest level of overestimation of their own role importance. A further analysis of the data showed that inexperienced nonprofessionals did not overestimate their own role performance. This suggested specific training procedures for nonprofessionals.  相似文献   
8.
Friedreich ataxia is a progressive neurodegenerative disorder caused by loss of function mutations in the frataxin gene. In order to unravel frataxin function we developed monoclonal antibodies raised against different regions of the protein. These antibodies detect a processed 18 kDa protein in various human and mouse tissues and cell lines that is severely reduced in Friedreich ataxia patients. By immunocytofluorescence and immunocytoelectron microscopy we show that frataxin is located in mitochondria, associated with the mitochondrial membranes and crests. Analysis of cellular localization of various truncated forms of frataxin expressed in cultured cells and evidence of removal of an N-terminal epitope during protein maturation demonstrated that the mitochondrial targetting sequence is encoded by the first 20 amino acids. Given the shared clinical features between Friedreich ataxia, vitamin E deficiency and some mitochondriopathies, our data suggest that a reduction in frataxin results in oxidative damage.   相似文献   
9.
The present study was designed to ascertain whether the negative effects on reproductive potential of post-ovulatory ageing in vitro of oocytes can be prevented by antioxidant therapy. Mouse metaphase II (MII) oocytes were aged in vitro for 12 h prior to insemination in the presence of varying concentrations of L-ascorbic acid, 6-methoxy- 2,5,7,8-tetramethylchromane-2-carboxylic acid (Trolox), L-cystine dihydrochloride, ethylenediaminetetraacetic acid (EDTA), beta- mercaptoethanol and DL-dithiothreitol (DTT). In-vitro ageing of oocytes was associated with lower fertilization rate, higher proportion of concepti exhibiting cellular fragmentation at 24 h post-insemination and lower percentage of concepti reaching the blastocyst stage. Ascorbic acid, Trolox and EDTA had no effect on cellular fragmentation or potential of oocytes for development. However, the probability of an oocyte reaching the blastocyst stage was decreased (P < or = or = 0.05) in oocytes incubated in the presence of L-cystine (50 and 500 microM) and beta-mercaptoethanol (5, 50 and 500 microM) when compared to control aged oocytes. Age-associated cellular fragmentation at 24 h post-insemination was partially prevented (P < or = 0.05) by incubating oocytes in the presence of beta-mercaptoethanol (500 microM). DTT (50 and 500 microM) increased (P < or = 0.05) fertilization rate and number of cells at 81 h post-insemination to levels similar to those exhibited by control oocytes. Furthermore, both age-associated fragmentation at 24 h post-insemination (P < or = 0.05) and decreased potential of oocytes for development to the blastocyst stage (P < or = 0.05) were prevented, at least in part, by culturing oocytes in the presence of DTT (50 microM). Although the mechanism by which DTT exerts its beneficial effects on aged oocytes remains to be elucidated, it may protect oocytes by preventing oxidation of free thiol groups and/or altering a redox-independent signalling pathway that mediates cellular fragmentation and death.   相似文献   
10.
Submicroscopic deletions of the Y chromosome and polymorphisms of the androgen receptor (AR) gene in the X chromosome have been observed in men with defective spermatogenesis. To further define the subregions/genes in the Y chromosome causing male infertility and its relationship to polymorphisms of the AR polyglutamine tract, we screened the genomic DNA of 202 subfertile males and 101 healthy fertile controls of predominantly Chinese ethnic origin. Y microdeletions were examined with 16 sequence-tagged site (STS) probes, including the RBM and DAZ genes, spanning the AZFb and AZFc subregions of Yq11, and related to the size of trinucleotide repeat encoding the AR polyglutamine tract. Y microdeletions were detected and confirmed in three out of 44 (6.8%) of azoospermic and three out of 86 (3.5%) severely oligozoospermic patients. No deletions were detected in any of the patients with sperm counts of >0.5 x 10(6)/ml, nor in any of the 101 fertile controls. All six affected patients had almost contiguous Y microdeletions spanning the entire AZFc region including the DAZ gene. The AZFb region, containing the RBM1 gene, was intact in five of the six subjects. Y deletions were not found in those with long AR polyglutamine tracts. Our study, the first in a Chinese population, suggest a cause and effect relationship between Y microdeletions in the AZFc region (possibly DAZ), and azoospermia or near-azoospermia. Y microdeletions and long AR polyglutamine tracts appear to be independent contributors to male infertility.   相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号