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   1696213篇
  免费   123762篇
  国内免费   3783篇
耳鼻咽喉   21739篇
儿科学   55756篇
妇产科学   46163篇
基础医学   241298篇
口腔科学   48778篇
临床医学   151379篇
内科学   333661篇
皮肤病学   38675篇
神经病学   131226篇
特种医学   63898篇
外国民族医学   242篇
外科学   257362篇
综合类   38971篇
现状与发展   4篇
一般理论   531篇
预防医学   124264篇
眼科学   40240篇
药学   123721篇
  7篇
中国医学   4483篇
肿瘤学   101360篇
  2021年   12815篇
  2019年   13540篇
  2018年   19983篇
  2017年   15234篇
  2016年   16638篇
  2015年   18983篇
  2014年   26265篇
  2013年   37991篇
  2012年   52800篇
  2011年   55512篇
  2010年   32814篇
  2009年   30718篇
  2008年   51542篇
  2007年   54844篇
  2006年   55301篇
  2005年   52583篇
  2004年   50784篇
  2003年   48183篇
  2002年   46389篇
  2001年   91794篇
  2000年   93626篇
  1999年   76970篇
  1998年   19727篇
  1997年   17273篇
  1996年   17393篇
  1995年   16745篇
  1994年   15301篇
  1993年   14079篇
  1992年   57395篇
  1991年   55290篇
  1990年   52988篇
  1989年   50763篇
  1988年   46145篇
  1987年   44945篇
  1986年   42235篇
  1985年   39999篇
  1984年   29352篇
  1983年   24913篇
  1982年   13904篇
  1979年   25531篇
  1978年   17575篇
  1977年   14907篇
  1976年   13877篇
  1975年   14567篇
  1974年   17636篇
  1973年   16953篇
  1972年   15674篇
  1971年   14461篇
  1970年   13437篇
  1969年   12517篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Preclinical research suggests adrenal beta-adrenergic receptors to be involved in the regulation of steroid synthesis. In a group of healthy male volunteers, we compared ACTH-induced cortisol and dehydroepiandrosterone (DHEA) secretion after pre-treatment with orciprenaline, propranolol or placebo. Neither baseline nor ACTH-induced steroid secretion differed between these conditions. Our data do not support the hypothesis that the adrenal beta-receptor plays a major role in steroid secretion in humans.  相似文献   
992.
993.
994.
The effects of OSM on proliferation and differentiation of osteosarcoma and nontransformed osteoblasts were analyzed. OSM downregulates osteoblast markers but induces the glial fibrillary acidic protein by the combined activation of PKCdelta and STAT3, offering new lines of therapeutic investigations. INTRODUCTION: Oncostatin M (OSM) is a multifunctional cytokine of the interleukin-6 family implicated in embryonic development, differentiation, inflammation, and regeneration of various tissues, mainly the liver, bone, and the central nervous and hematopoietic systems. One particularity of OSM relies on its growth inhibitory and pro-differentiating effects on a variety of tumor cell lines such as melanoma, providing arguments for a therapeutic application of OSM. The objective of this study was to analyze the effects of OSM on osteosarcoma cell lines proliferation and differentiation. MATERIALS AND METHODS: Proliferation was analyzed by 3H thymidine incorporation. Differentiation was analyzed by semiquantitative RT-PCR and immunocytochemistry for various markers. Alizarin red S staining was used to evaluate bone nodule formation. Morphological changes were studied by confocal and electron microscopy. Western blotting, kinases inhibitors, and dominant negative STAT3 were used to identified the signaling pathways implicated. RESULTS: OSM inhibits the growth of rat osteosarcoma cell lines as well as normal osteoblasts, in correlation with induction of the cyclin-dependent kinases inhibitor p21WAF1. However, OSM reduces osteoblast markers such as alkaline phosphatase, osteocalcin, and bone sialoprotein, leading to strong inhibition of mineralized nodule formation. This inhibitory effect is restricted to mature osteoblasts and differentiated osteosarcoma because OSM effectively stimulates osteoblast markers and bone nodule formation in early, but not late, bone marrow mesenchymal stem cell (BMSC) cultures. In osteosarcoma cells or BMSC, OSM induces expression of the glial fibrillary acidic protein (GFAP) as well as morphological and ultrastructural changes, for example, elongated shape and bundles of microfilaments in cell processes. Rottlerin (PKCdelta inhibitor), and to a lesser degree UO126 (MEK/ERK inhibitor), prevents the loss of osteoblastic markers by OSM, whereas dominant negative STAT3 prevents GFAP induction. CONCLUSIONS: These results highlight the particular gene expression profile of OSM-treated osteosarcoma cells and BMSCs, suggesting either a osteocytic or a glial-like phenotype. Together with the implication of PKCdelta, ERK1/2, and STAT3, these results offer new lines of investigations for neural cell transplantation and osteosarcoma therapy.  相似文献   
995.
996.
Neuronavigation has become an effective therapeutic modality and is used routinely for intra-axial tumor removal. This retrospective study was conducted to evaluate the clinical impact of neuronavigation and image-guided extensive resection for adult patients with supratentorial malignant astrocytomas. Between 1990 and 2002, 76 adult patients with pathologically confirmed malignant astrocytomas underwent craniotomy and removal of the tumors at the Toyama Medical and Pharmaceutical University Hospital. Of these 76 patients, 42 were treated using neuronavigation with conventional microneurosurgery and the other 34 were treated with conventional microneurosurgery alone. Postoperative early MRI with contrast enhancement was done, and gross total resection was defined as the complete absence of residual tumor. Survival time was analyzed with the Kaplan-Meier method. Prognostic factors were obtained from the Cox proportional hazards model. In univariate analysis, age (< 65), grade 3, preoperative KPS (>/= 80), use of neuronavigation, and gross total resection were significantly associated with longer survival. However, when the data were submitted to multivariate analysis, grade 3, preoperative KPS (>/= 80), and gross total resection were independent prognostic factors. The median survival periods of patients receiving gross total resection (vs. partial resection) and neuronavigation (vs. no neuronavigation) were 16 (vs. 9) months and 16 (vs. 10) months, respectively. The percentage of a gross total resection was significantly higher in the neuronavigation group compared to that in the no-navigation group (64.3 % vs. 38.2 %, p < 0.05). Neurological deterioration occurred in 4 of 42 (9.5 %) and in 6 of 34 (17.6 %) patients after surgery with neuronavigation and surgery without neuronavigation, respectively, although this difference was not statistically significant. Our results showed that neuronavigation increases the radicality in the resection of malignant astrocytomas and is objectively useful for improving survival time.  相似文献   
997.
998.
999.
1000.
OBJECTIVES: To assess the attitudes and practices of contraceptive behaviors of Western Ukraine women. METHODS: A survey of 500 women in the Oblast was conducted to assess their knowledge, attitudes and practices on a variety of health topics. Convenience sampling was used to access the subjects in 16 different towns/villages in nine rayons throughout the Oblast. Respondents were asked more than 100 questions pertaining to their knowledge, attitudes and practices on a variety of health topics, including stress, contraception, breast health, sexually transmitted diseases, parity, abortion, nutrition, alcohol and tobacco use, domestic violence, and depression and mental health. RESULTS: Of married women, 44% (112/256) would terminate their pregnancy while 56% (144/256) said they would keep their baby. Of unmarried women, 35% (31/88) would abort while 65% (57/88) would keep their baby. A large proportion of married women (82%; 222/271) and unmarried women (70%; 52/74) did not use condoms at all. CONCLUSION: These results suggest lack of birth control education and contribution to poor protection from sexually transmitted infections. Higher abortion practices may also play a role in the infertility issues that Ukrainian women currently face.  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