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   1414134篇
  免费   97942篇
  国内免费   2298篇
耳鼻咽喉   19985篇
儿科学   46212篇
妇产科学   41097篇
基础医学   206782篇
口腔科学   40239篇
临床医学   116008篇
内科学   281633篇
皮肤病学   30391篇
神经病学   110385篇
特种医学   53526篇
外国民族医学   367篇
外科学   212943篇
综合类   27210篇
现状与发展   1篇
一般理论   321篇
预防医学   108617篇
眼科学   32898篇
药学   108472篇
  1篇
中国医学   3020篇
肿瘤学   74266篇
  2018年   16104篇
  2017年   11605篇
  2016年   12716篇
  2015年   14544篇
  2014年   19275篇
  2013年   29415篇
  2012年   42239篇
  2011年   45150篇
  2010年   25737篇
  2009年   23343篇
  2008年   42437篇
  2007年   45957篇
  2006年   46248篇
  2005年   45129篇
  2004年   43160篇
  2003年   41688篇
  2002年   40903篇
  2001年   61746篇
  2000年   63643篇
  1999年   53800篇
  1998年   14799篇
  1997年   13185篇
  1996年   13420篇
  1995年   12658篇
  1994年   12025篇
  1992年   42715篇
  1991年   41872篇
  1990年   41417篇
  1989年   40013篇
  1988年   37370篇
  1987年   36497篇
  1986年   34902篇
  1985年   33222篇
  1984年   24724篇
  1983年   21483篇
  1982年   12741篇
  1981年   11253篇
  1979年   23604篇
  1978年   16532篇
  1977年   14364篇
  1976年   13579篇
  1975年   14935篇
  1974年   17565篇
  1973年   17025篇
  1972年   16209篇
  1971年   15123篇
  1970年   14035篇
  1969年   13628篇
  1968年   12892篇
  1967年   11285篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
991.
992.
993.
994.
995.
WT-1 positivity has previously been noted in nonneoplastic endometrial stroma. In this study we examined WT-1 expression in endometrial stromal neoplasms to ascertain whether these tumors are immunoreactive and whether this antibody might be of value in the diagnosis of these lesions. We also stained cases of cellular and highly cellular leiomyomas to investigate whether WT-1 might be of value in distinguishing these from an endometrial stromal neoplasm. We compared WT-1 staining with CD10, desmin, alpha smooth muscle actin, h-caldesmon, and AE1/3, many of these antibodies being commonly used to distinguish between an endometrial stromal and a smooth muscle phenotype. Cases of ESN (n = 5), low grade ESS (n = 14), and cellular or highly cellular leiomyoma (n = 14) were stained with the aforementioned antibodies. Cases were scored on a scale of 0 to 4+, with 4+ cases exhibiting positivity of >50% of cells. Sixteen of 19 endometrial stromal neoplasms were positive with WT-1, most (14 of 16) with 4+ positivity. Staining was nuclear (5 cases), cytoplasmic (5 cases), or combined nuclear and cytoplasmic (6 cases). All endometrial stromal neoplasms exhibited 4+ staining with CD10. Staining for alpha smooth muscle actin was present in most cases (14 of 19) and desmin and h-caldesmon were positive in a smaller number of cases (8 and 2 respectively). There was 4+ positivity with desmin in only 1 case. The 2 cases that were h-caldesmon positive both exhibited 1+ staining (<5% cells positive). Six cases were positive with AE1/3, 1 with 4+ staining. Leiomyomatous neoplasms always exhibited 4+ staining with desmin and alpha smooth muscle actin and in most cases (12 of 14) with h-caldesmon. The other 2 cases exhibited 2+ positivity. Most cases (12 of 14) were positive with WT-1 (7 of 14 with 4+ staining) and CD10 (5 of 14 with 4+ positivity). One case was positive with AE1/3. We conclude that diffuse WT-1 positivity is characteristic of endometrial stromal neoplasms and that this may be of value in diagnosis. However, WT-1 is of limited use in the distinction between an endometrial stromal and a cellular leiomyomatous neoplasm because many of the latter are also positive. This study confirms the value of h-caldesmon in the distinction between an endometrial stromal neoplasm (almost always h-caldesmon negative) and a cellular leiomyomatous neoplasm (h-caldesmon positive). Although CD10 is positive in endometrial stromal neoplasms, the commonly observed immunoreactivity of cellular and highly cellular leiomyomas with this antibody limits its diagnostic usefulness. Desmin is useful as all leiomyomatous neoplasms exhibited diffuse positivity, whereas only a small number of endometrial stromal neoplasms were focally positive and only 1 case exhibited 4+ positivity. Smooth muscle actin is of limited value since most neoplasms studied were positive. The overlapping immunophenotype of endometrial stromal and leiomyomatous neoplasms may reflect the origin of both cell types from a common progenitor within the uterus.  相似文献   
996.
Members of the R7 subfamily of regulators of G-protein signaling (RGS) proteins (RGS6, RGS7, RGS9-2, and RGS11) are found in the mouse CNS. The expression of these proteins was effectively reduced in different neural structures by blocking their mRNA with antisense oligodeoxynucleotides (ODNs). This was achieved without noticeable changes in the binding characteristics of labeled beta-endorphin to opioid receptors. Knockdown of R7 proteins enhanced the potency of antinociception promoted by morphine and [D-Ala(2), N-MePhe(4), Gly-ol(5)]-enkephalin (DAMGO)-both agonists at mu-opioid receptors. The duration of morphine analgesia was greatly increased in RGS9-2 and in RGS11 knockdown mice. The impairment of R7 proteins brought about different changes in the analgesic activity of selective delta agonists. Knockdown of RGS11 reduced [D-Ala(2)]deltorphin II analgesic effects. Those of RGS6 and RGS9-2 proteins caused [D-Ala(2)]deltorphin II to produce a smoothened time-course curve-the peak effect blunted and analgesia extended during the declining phase. RGS9-2 impairment also promoted a similar pattern of change for [D-Pen(2,5)]-enkephalin (DPDPE). RGS7-deficient mice showed an increased response to both [D-Ala(2)]deltorphin II and DPDPE analgesic effects. A single intracerebroventricular (i.c.v.) ED(80) analgesic dose of morphine gave rise to acute tolerance in control mice, but did not promote tolerance in RGS6, RGS7, RGS9-2, or RGS11 knockdown animals. Thus, R7 proteins play a critical role in agonist tachyphylaxis and acute tolerance at mu-opioid receptors, and show differences in their modulation of delta-opioid receptors.  相似文献   
997.
Chronically elevated levels of corticotropin-releasing factor (CRF) in transgenic mice overexpressing CRF in the brain (CRF-OE) appear to be associated with alterations commonly associated with major depressive disorder, as well as with sensorimotor gating deficits commonly associated with schizophrenia. In the present study, we tested the hypothesis that antipsychotics may be effective in normalizing prepulse inhibition (PPI) of acoustic startle in CRF-OE mice, which display impaired sensorimotor gating compared to wild-type (WT) mice. The typical antipsychotic haloperidol and atypical antipsychotic risperidone improved PPI in the CRF-OE mice, but were ineffective in WT mice. The atypical antipsychotic clozapine did not influence PPI in CRF-OE mice, but reduced gating in WT mice. This effect of clozapine in the CRF-OE mice may thus be regarded as a relative improvement, consistent with the observed effect of haloperidol and risperidone. As expected, the anxiolytic, nonantipsychotic chlordiazepoxide was devoid of any effect. All four compounds dose-dependently reduced the acoustic startle response irrespective of genotype. These results indicate that antipsychotic drugs are effective in improving startle gating deficits in the CRF-OE mice. Hence, the CRF-OE mouse model may represent an animal model for certain aspects of psychotic depression, and could be a valuable tool for research addressing the impact of chronically elevated levels of CRF on information processing.  相似文献   
998.
999.
Abstract – Traumatic dental injuries often occur to the teeth and their supporting tissues and they are the main reasons for emergency visit to a dental clinic. Management of a fracture depends on its position and the extent of root involvement. Horizontal root fractures are not seen frequently and the treatment consists of reduction and long‐term rigid fixation of the coronal segment. The present case demonstrates the successful management of two horizontally fractured maxillary central incisors with a follow‐up period of 9 months.  相似文献   
1000.
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