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   136924篇
  免费   7287篇
  国内免费   296篇
耳鼻咽喉   2125篇
儿科学   5548篇
妇产科学   4337篇
基础医学   18823篇
口腔科学   3332篇
临床医学   10189篇
内科学   26315篇
皮肤病学   3940篇
神经病学   10313篇
特种医学   6177篇
外国民族医学   32篇
外科学   21770篇
综合类   2366篇
现状与发展   1篇
一般理论   43篇
预防医学   6882篇
眼科学   4110篇
药学   9651篇
中国医学   493篇
肿瘤学   8060篇
  2021年   1311篇
  2019年   1163篇
  2018年   1590篇
  2017年   1281篇
  2016年   1709篇
  2015年   2032篇
  2014年   2600篇
  2013年   3429篇
  2012年   4787篇
  2011年   4781篇
  2010年   2889篇
  2009年   2755篇
  2008年   4410篇
  2007年   4621篇
  2006年   4741篇
  2005年   4791篇
  2004年   4520篇
  2003年   4237篇
  2002年   4064篇
  2001年   7534篇
  2000年   7459篇
  1999年   6252篇
  1998年   1754篇
  1997年   1668篇
  1996年   1409篇
  1995年   1287篇
  1994年   1171篇
  1993年   1181篇
  1992年   3919篇
  1991年   3739篇
  1990年   3698篇
  1989年   3477篇
  1988年   3101篇
  1987年   3027篇
  1986年   2909篇
  1985年   2711篇
  1984年   2016篇
  1983年   1663篇
  1982年   963篇
  1981年   941篇
  1979年   1882篇
  1978年   1378篇
  1977年   1150篇
  1976年   964篇
  1975年   1216篇
  1974年   1251篇
  1973年   1234篇
  1972年   1077篇
  1971年   1009篇
  1970年   914篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
22.
PurposeCongenital high airway obstruction syndrome (CHAOS) is a devastating fetal condition of complete airway discontinuity resulting in significant hydrops and extreme lung hyperplasia. It is universally fatal with survival reported only in the rare spontaneous fistulization or EXIT intervention (Ex Utero Intrapartum Treatment). Even in these cases, mortality remains high, and current investigations are targeting prenatal interventions. This report describes our experience with management and fetal interventions for CHAOS, including laser laryngotomy.MethodsWe retrospectively reviewed all patients diagnosed with CHAOS at a single academic institution between 2006 and 2017.ResultsFifteen patients were identified. Eight had obstruction at the trachea and seven at the larynx. In the laryngeal obstructions, three expired shortly after birth, and one survived after spontaneous fistulization and subsequent EXIT to tracheostomy. The remaining three underwent in-utero treatment with laser laryngotomy. One had preterm premature rupture of membranes (PPROM), delivered 3 days post-operatively, and died. Two underwent EXIT to tracheostomy with one surviving to discharge and is currently 2 years old.ConclusionOur study demonstrates the outcomes of a large series of patients diagnosed with CHAOS. While mortality remains high, options for fetal intervention are being explored to allow alterations in the prenatal natural history and improve postnatal outcomes.Type of StudyRetrospective Treatment Study.Level of EvidenceLevel IV.  相似文献   
23.
24.
25.
We investigated whether protein kinase C (PKC) is involved in trimethyltin (TMT)-induced neurotoxicity. TMT treatment (2.8 mg/kg, i.p.) significantly increased PKCδ expression out of PKC isozymes (i.e., α, βI, βII, δ, and ?) in the hippocampus of wild-type (WT) mice. Consistently, treatment with TMT resulted in significant increases in cleaved PKCδ expression. Genetic or pharmacological inhibition (PKCδ knockout or rottlerin) was less susceptible to TMT-induced seizures than WT mice. TMT treatment increased glutathione oxidation, lipid peroxidation, protein oxidation, and levels of reactive oxygen species. These effects were more pronounced in the WT mice than in PKCδ knockout mice. In addition, the ability of TMT to induce nuclear translocation of Nrf2, Nrf2 DNA-binding activity, and upregulation of γ-glutamylcysteine ligase was significantly increased in the PKCδ knockout mice and rottlerin (10 or 20 mg/kg, p.o. × 6)-treated WT mice. Furthermore, neuronal degeneration (as shown by nuclear chromatin clumping and TUNEL staining) in WT mice was most pronounced 2 days after TMT. At the same time, TMT-induced inhibition of phosphoinositol 3-kinase (PI3K)/Akt signaling was evident, thereby decreasing phospho-Bad, expression of Bcl-xL and Bcl-2, and the interaction between phospho-Bad and 14-3-3 protein, and increasing Bax expression and caspase-3 cleavage were observed. Rottlerin or PKCδ knockout significantly protected these changes in anti- and pro-apoptotic factors. Importantly, treatment of the PI3K inhibitor LY294002 (0.8 or 1.6 µg, i.c.v.) 4 h before TMT counteracted protective effects (i.e., Nrf-2-dependent glutathione induction and pro-survival phenomenon) of rottlerin. Therefore, our results suggest that down-regulation of PKCδ and up-regulations of Nrf2-dependent glutathione defense mechanism and PI3K/Akt signaling are critical for attenuating TMT neurotoxicity.  相似文献   
26.
27.
28.
29.
Chronic transplant dysfunction is a complex dynamic pathogenic process. Clinically, a decrease in glomerular filtration rate (GFR) becomes apparent leading to chronic renal insufficiency and dialysis or death from cardiovascular events. Chronic transplant dysfunction can develop into a chronic alIograft nephropathy (CAN) as a specific entity with dynamic progression. CAN includes a collection of immunologic and non-immunologic factors, rejection, ischemia time, donor and recipient characteristics and toxicity of calcineurin inhibitors. Despite improvements in immunosuppression, the long-range prognosis of renal allografts has not improved. Whether modern immunosuppressive concepts with reduction or avoidance of calcineurin inhibitors and a therapy based on antimetabolites, such as mycophenolate or mTOR-inhibitors could lead to a prolongation of transplant survival, remains to be seen.  相似文献   
30.
Multi-day signals, generally with duration of 2-10 days, are a prominent temporal variation type of radon (Rn) in geogas in the unsaturated zone. Rare multi-day Rn signals have been found which are characterized by: (a) a declining limb lasting up to 10 days which conforms to the radioactive decay of Rn, (b) recurs at the same location and (c) is recorded in diverse situations-volcanic and seismogenic. It suggested that a Rn blob is injected at a lower level on a steady upward flow of geogas whereby the rise and final fall of the signal are attributed to the edges of the blob while the central Rn-decay segment records the passing of the decaying blob itself. Rn-decay signals are a small subset of multi-day Rn signals which are considered as highly irregular and unusable for the understanding of geophysical processes. In difference, it is concluded that multi-day Rn signals are probably proxies of subtle geodynamic processes at upper crustal levels and are therefore significant for studying such processes.  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