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   3630篇
  免费   201篇
  国内免费   22篇
耳鼻咽喉   17篇
儿科学   184篇
妇产科学   61篇
基础医学   481篇
口腔科学   58篇
临床医学   246篇
内科学   638篇
皮肤病学   87篇
神经病学   241篇
特种医学   131篇
外科学   396篇
综合类   211篇
一般理论   1篇
预防医学   253篇
眼科学   46篇
药学   315篇
中国医学   15篇
肿瘤学   472篇
  2022年   37篇
  2021年   98篇
  2020年   56篇
  2019年   48篇
  2018年   77篇
  2017年   56篇
  2016年   81篇
  2015年   85篇
  2014年   114篇
  2013年   161篇
  2012年   221篇
  2011年   235篇
  2010年   176篇
  2009年   113篇
  2008年   194篇
  2007年   193篇
  2006年   176篇
  2005年   146篇
  2004年   141篇
  2003年   144篇
  2002年   136篇
  2001年   120篇
  2000年   92篇
  1999年   84篇
  1998年   39篇
  1997年   33篇
  1996年   30篇
  1995年   32篇
  1994年   26篇
  1993年   29篇
  1992年   48篇
  1991年   50篇
  1990年   41篇
  1989年   37篇
  1988年   43篇
  1987年   30篇
  1986年   27篇
  1985年   26篇
  1984年   23篇
  1983年   27篇
  1981年   16篇
  1980年   16篇
  1979年   27篇
  1978年   16篇
  1977年   19篇
  1976年   20篇
  1975年   19篇
  1974年   17篇
  1973年   16篇
  1971年   16篇
排序方式: 共有3853条查询结果,搜索用时 46 毫秒
61.
62.
63.
Sarcoma of the small bowel is an extremely rare type of small bowel malignancy and represents around 10 per cent of small bowel cancers. Usually asymptomatic, patients can present with chronic abdominal distention with pain and/or weight loss. Most pathologists now refer to small bowel sarcomas (SBS) as gastrointestinal stromal tumours as they are mesenchymal neoplasms believed to be derived from the interstitial cells of Cajal in the gastrointestinal tract. SBS can be highly vascular and commonly ulcerate and/or bleed. They tend to be aggressive and have a poor prognosis. Surgery is the treatment of choice for SBS, with definitive diagnosis usually made postoperatively with the aid of histopathology. We would like to highlight the importance of careful intra-operative examination of an unknown small bowel (SB) mass, which can give the surgeon clues to the type of tumour present. This case report aims to demonstrate this important process: recognising SBS intra-operatively will aid the surgeon with performing the appropriate resection as minute omental metastasis can be present with SBS; in such cases an omentectomy during the laparotomy is recommended. In institutions where available, intra-operative radiotherapy is ideal.  相似文献   
64.
Das  Nikita  Raymick  James  Sarkar  Sumit 《Metabolic brain disease》2021,36(7):1627-1639
Metabolic Brain Disease - Metal homeostasis in the central nervous system (CNS) is a crucial component of healthy brain function, because metals serve as enzymatic cofactors and are key components...  相似文献   
65.
Succinic dehydrogenase activity of the DMBA induced tumor explants cultured with or without hormones was assessed histochemically while receptors for estrogen (ER) and progesterone (PgR) were estimated from the cytosol fraction of the tumor tissue. Tumor regression following ovariectomy (OVX) was kept as the end point for determining hormone dependency. By in vitro method positive correlation was observed in 5 of 6 responsive or hormone dependent tumors, and 13 out of 14 independent tumors. Presence of receptors (ER + PgR, PgR) correlated with responsiveness in 4 of 6 tumors while their absence in the non-responsive group correlated in 6 of 14 tumors. Prolactin responsive tumors did not regress following OVX even if ER + PgR or ER/PgR were present. Using the same tumor tissue the results of hormone dependency by the two methods were identical in only 9 of 20 tumors.  相似文献   
66.
67.
Raloxifene has been shown to increase bone mineral density and reduce the risk of vertebral fracture in postmenopausal women with osteoporosis. In this study, we report the results of the first prospective longitudinal study to evaluate the mean degree of mineralization of bone (MDMB) in a group of patients enrolled in the Multiple Outcomes of Raloxifene Evaluation trial. Patients were randomly assigned to one of three treatment groups: placebo (n = 24), raloxifene 60 mg/d (RLX60; n = 22), or raloxifene 120 mg/d (RLX120; n = 18). All patients received daily calcium (500 mg) and vitamin D(3) (400-600 IU) supplementation for the duration of the study. Iliac crest biopsies were taken at baseline and after 2 yr of treatment. Quantitative microradiography was used to analyze the biopsy specimens and revealed a statistically significant (P < 0.05) mean percentage increase in total MDMB of 7.0, 5.3, and 5% for RLX60-, RLX120-, and placebo-treated patients, respectively, compared with baseline. Raloxifene treatment was found to shift the distribution of total bone mineral to higher values of MDMB (RLX60, 29%; RLX120, 8%) with greater heterogeneity, compared with placebo. The profile of MDMB observed in biopsies after treatment with placebo and raloxifene, compared with baseline, closely resembles physiological premenopausal bone.  相似文献   
68.
Ovariectomized rats, when transplanted with 4 anterior pituitaries (APs) to the kidney capsule for 2-3 weeks, had elevated plasma prolactin (PRL) levels (3.8-fold) and showed decreased in situ AP weights (0.62-fold) and PRL concentrations (0.63-fold). The concentrations of dopamine (DA) and oxytocin (OT) in pituitary portal plasma of hyperprolactinemic rats were increased 1.7- and 1.9-fold, respectively. However, the levels of vasoactive intestinal peptide (VIP) in pituitary portal plasma of these rats were decreased 0.31-fold. The secretion of DA, dihydroxyphenylalanine (DOPA) and OT from fetal hypothalamic cells in primary culture was increased, whereas VIP secretion from these cells was reduced in a dose-dependent fashion following PRL treatment. These data are the first in vivo and in vitro demonstration of a stimulatory action of PRL on OT release and an inhibitory action of PRL on VIP release. Furthermore, these data suggest that a subtle imbalance between the secretion of the PRL-inhibiting factor (DA) and the PRL-releasing factors (VIP and OT) during elevated systemic levels of PRL is responsible for decreased lactotrophic function.  相似文献   
69.
BACKGROUND: Alcohol drinking is known to cause hyperprolactinemia in both humans and laboratory animals. The mechanism by which alcoholism causes hyperprolactinemia is not known. This study investigated whether increased pituitary production of prolactin, which leads to alcohol-induced hyperprolactinemia, results from an increase in cell number and/or cell production of prolactin in the pituitary. METHODS: The effects of ethanol on lactotropes were determined in vivo using female rats as an animal model and in vitro using primary cultures of mixed rat anterior pituitary cells and enriched lactotropes. In vivo experiments involved administration of ethanol for 2 and 4 weeks using a liquid diet containing 8.7% ethanol (v/v), which provides 37% of the calories in cyclic, ovariectomized, and estradiol-17beta-treated ovariectomized Fischer-344 rats. The control group was pair-fed an isocaloric diet minus the ethanol or fed a normal diet ad libitum. These animals were used to determine ethanol's effects on plasma prolactin levels, pituitary wet weights, pituitary total protein levels, and the number of mitotic lactotropes. In vitro studies determined ethanol's effects in the presence and absence of estradiol on prolactin release and lactotropic cell proliferation. Prolactin levels in plasma and media samples were measured using radioimmunoassay. Mitotic lactotropes were determined using bromodeoxyuridine incorporation assay. RESULTS: Ethanol treatment increased in a time-dependent manner the plasma levels of prolactin in cyclic, ovariectomized, and estradiol-treated ovariectomized rats. Ethanol treatment also increased pituitary wet weight and/or pituitary total protein levels and DNA synthesis in lactotropes. Determination of ethanol's action on lactotropic cell proliferation and hormone secretion in vitro using primary cultures of mixed pituitary cells revealed that ethanol stimulated both basal and estradiol-induced prolactin secretion and lactotropic cell proliferation. When ethanol's actions were studied in isolated lactotropes, ethanol alone or in combination with estradiol stimulated prolactin secretion but failed to increase lactotropic cell proliferation. CONCLUSIONS: These results suggest that ethanol causes hyperprolactinemia by elevating prolactin release from lactotropes and by increasing the number of lactotropes in the anterior pituitary gland. The mitotic action of ethanol requires cell-cell communication between lactotropes and other pituitary cells. Furthermore, ethanol's mode of action on prolactin release and lactotrope growth is similar to that observed for estradiol.  相似文献   
70.
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