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   10931篇
  免费   1191篇
  国内免费   21篇
耳鼻咽喉   66篇
儿科学   317篇
妇产科学   213篇
基础医学   1448篇
口腔科学   235篇
临床医学   1252篇
内科学   2061篇
皮肤病学   117篇
神经病学   958篇
特种医学   344篇
外国民族医学   1篇
外科学   2180篇
综合类   368篇
一般理论   12篇
预防医学   1095篇
眼科学   199篇
药学   647篇
中国医学   7篇
肿瘤学   623篇
  2023年   84篇
  2022年   91篇
  2021年   243篇
  2020年   161篇
  2019年   235篇
  2018年   278篇
  2017年   205篇
  2016年   189篇
  2015年   226篇
  2014年   337篇
  2013年   452篇
  2012年   625篇
  2011年   637篇
  2010年   363篇
  2009年   310篇
  2008年   481篇
  2007年   550篇
  2006年   504篇
  2005年   463篇
  2004年   444篇
  2003年   421篇
  2002年   410篇
  2001年   271篇
  2000年   260篇
  1999年   256篇
  1998年   124篇
  1997年   115篇
  1996年   92篇
  1995年   97篇
  1994年   86篇
  1992年   209篇
  1991年   202篇
  1990年   191篇
  1989年   169篇
  1988年   153篇
  1987年   136篇
  1986年   166篇
  1985年   155篇
  1984年   115篇
  1983年   101篇
  1982年   78篇
  1979年   98篇
  1978年   93篇
  1977年   66篇
  1976年   70篇
  1975年   69篇
  1974年   70篇
  1973年   85篇
  1972年   86篇
  1971年   73篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
72.
73.
In this report we compare the bioactivities of pure, human monocyte-derived interleukin 1 (IL-1) alpha and beta in the standard murine thymocyte proliferation assay, a human dermal fibroblast proliferation assay, and in an assay measuring stimulation of prostaglandin E2 (PGE2) release from human rheumatoid synoviocytes. In each case the different species of IL-1 produced saturable stimulation and gave similar dose response curves. Half-maximal stimulation was observed at average IL-1 concentrations of 29 pM in the thymocyte assay, 2 pM in the dermal fibroblast proliferation assay, and 5 pM in the synovial cell assay. Our results show that native, monocyte-derived IL-1 alpha and IL-1 beta are both potent stimulators of connective tissue cells and that the specific bioactivities of these molecules are similar to each other in tests on human connective tissue cells, as well as on murine lymphoid cells.  相似文献   
74.
This data would suggest that psychiatric training programs may not be organized according to the interest or needs of many trainees. The emphasis on fulltime research in neurobiological psychiatry is centre stage in most programs, and yet according to our survey, few residents view this as a desirable career path. Our data from 8 years of trainees at the University of Toronto indicates that a new model of training streams would best suit the needs of the trainee, the profession and the community. This report is a continuation of a study into the recruitment process. An earlier report was published in the Canadian Journal of Psychiatry Vol. 29, December 1984. Our present data is on two groups of trainees as well as from faculty.  相似文献   
75.
This paper examines medical malpractice law as it applies to medically necessary oral health care. The basic legal concepts and reported cases involving medically necessary oral health care are reviewed. It is concluded that dental professionals and consumer advocates must advance their educational and legislative advocacy efforts so that health professional colleagues and the public will become aware of the importance of these services and insurers will routinely include coverage of medically necessary oral health care in their medical and dental policies. While failure to provide medically necessary oral health care can be violative of patient rights and legally actionable, medical malpractice litigation should always be the behavior modifier of last resort.  相似文献   
76.
77.
Several molecules, such as growth factors and neurotrophic factors, are required both for the differentiation of specific retinal cell types and the long-term cell survival of all retinal neurons. As diffusible factors, these molecules act non-cell-autonomously. Here, we describe the loss of function phenotype for dazed (dzd), a gene that acts cell-autonomously for retinal cell survival and affects the differentiation of rod photoreceptors and the Muller glia. By 3 days after fertilization, dazed mutant embryos have small eyes and slight heart edema. Acridine orange staining indicated a significant degree of retinal cell death occurring by 48 hr after fertilization, and histological analysis revealed that dying cells were found in the inner and outer nuclear layers and near the marginal zones. Although molecular and morphological differentiation of the inner retina and cone photoreceptors occurred, rod photoreceptors failed to differentiate beyond a small patch in the ventral retina and rod precursors failed to respond to exogenously added retinoic acid, which normally potentiated rod differentiation. Mosaic analysis indicated that the dazed gene acts cell-autonomously for rod production and cell survival, as dazed clones failed to produce rods outside the ventral patch and dazed cells were not maintained in wild-type hosts. Raising mutants under constant light resulted in severe retinal degeneration, whereas raising embryos under constant darkness did not provide any additional protection from cell death. Behavioral analysis showed that a subpopulation of adult fish that were heterozygous for the dazed mutation had elevated visual thresholds and were night blind, suggesting that dazed may also be required for long-term dim-light vision. Taken together, our studies suggest a role for the dazed gene in rod and Muller cell development and overall retinal cell survival and maintenance.  相似文献   
78.
Dendritic cells (DC) for cancer immunotherapy protocols are generated most commonly by in vitro differentiation of monocytes with exogenous cytokines (Mo-DC). However, Mo-DC differ in their molecular phenotype and function from blood DC (BDC). Clinical isolation of BDC has been limited to the use of density gradients, which result in low yields of variable purity. We have developed a DC enrichment platform, which uses the CMRF-44 (IgM) or CMRF-56 (IgG) monoclonal antibodies (mAb) to select BDC that express these antigens after a short overnight incubation. After culture of peripheral blood mononuclear cells (PBMC) in autologous/AB serum, biotinylated CMRF-44 was used to select DC in a single step immuno-magnetic bead procedure; this produced populations containing up to 99% CMRF-44(+) cells, including up to 67% CMRF-44(+) CD14(-) CD19(-) DC, from an initial starting population of approximately 0.5%. We observed consistent differences in the purities obtained from individual donors with a mean of 54% CMRF-44(+) cells (range 19-99%). Similar results were obtained using biotinylated CMRF-56 mAb, an antibody identifying a comparable population in cultured PBMC. We recovered an average of 54% and 66% of the available BDC in separations performed with the CMRF-44 and CMRF-56 mAb, respectively. The reproducibility of the procedure and the ability to perform it in a closed sterile system makes it suitable for clinical use. Larger scale preparations starting from apheresis derived PBMC will produce sufficient BDC for immunotherapy protocols. The purified BDC elicited strong allogeneic mixed leukocyte reactions and HLA classes II- and I-restricted antigen-specific primary immune responses.  相似文献   
79.
An education program to reduce unnecessary laboratory tests by residents   总被引:1,自引:0,他引:1  
What are often called "little-ticket" items--X-rays and laboratory tests--account for 25-30% of all health care costs. Two such items were the focus of this study, which took place at an inner-city community health center operated by the Department of Family Medicine of Cook County Hospital and involved 20 family practice residents over a period of nine weeks. The first item was the complete blood count (CBC) with differential, a prototype of a low-cost, high-volume test often ordered by reflex; the second, the thyroid stimulating hormone (TSH) test, a high-cost, low-volume test normally associated with a differential diagnosis or clinical reasoning. Through the use of a simple educational intervention based on quality of care, not cost-containment, and an audit feedback system, the authors were able to reduce significantly the rates of ordering TSH tests (p less than .0001) and CBCs (p = .05). This effect on the rates persisted five months after the intervention terminated. In addition, the percentage of TSH tests clinically indicated by explicit criteria increased significantly (p less than .001) during the intervention. However, this effect showed signs of diminishing five months after the intervention ended. The percentage of CBCs clinically indicated did not change significantly as a result of this intervention.  相似文献   
80.
Guinea pigs develop a lethal pneumonia after intratracheal infection with Legionella micdadei, and the lung displays pathological changes similar to those observed in humans. To investigate the role of the resident alveolar macrophage in the pathogenesis of L. micdadei pneumonia, guinea pig alveolar macrophages obtained by bronchoalveolar lavage were cultured in vitro and infected with L. micdadei. In the absence of opsonins L. micdadei was phagocytized by, and multiplied within, alveolar macrophages with greater than a 100-fold increase in cell-associated colony forming units over 20 h. L. micdadei opsonized with complement or antibody multiplied within alveolar macrophages at the same rate as unopsonized bacteria. Guinea pigs which were treated with antimicrobials after infection with L. micdadei and recovered from the pneumonia were immune to challenge with an otherwise lethal inoculum of L. micdadei. However, the growth curve of both unopsonized and opsonized L. micdadei in the alveolar macrophages from immune animals was essentially identical to that in macrophages from susceptible animals. Thus, the resident alveolar macrophage is not capable of limiting the growth of Legionella. Rather, the alveolar macrophages appear to be the primary site of Legionella multiplication within the lung. Although alveolar macrophages may participate in other aspects of pulmonary immunity to the legionellae, these data indicate that the alveolar macrophage alone does not act as an effector cell in cell-mediated immunity to Legionella.  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