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   578篇
  免费   48篇
  国内免费   2篇
耳鼻咽喉   10篇
儿科学   32篇
妇产科学   12篇
基础医学   60篇
口腔科学   5篇
临床医学   108篇
内科学   113篇
皮肤病学   9篇
神经病学   24篇
特种医学   38篇
外科学   67篇
综合类   3篇
预防医学   63篇
眼科学   3篇
药学   40篇
中国医学   3篇
肿瘤学   38篇
  2023年   14篇
  2022年   27篇
  2021年   36篇
  2020年   15篇
  2019年   21篇
  2018年   16篇
  2017年   13篇
  2016年   17篇
  2015年   28篇
  2014年   30篇
  2013年   32篇
  2012年   39篇
  2011年   32篇
  2010年   12篇
  2009年   24篇
  2008年   32篇
  2007年   26篇
  2006年   30篇
  2005年   26篇
  2004年   9篇
  2003年   15篇
  2002年   8篇
  2001年   5篇
  2000年   3篇
  1999年   11篇
  1998年   12篇
  1997年   13篇
  1996年   13篇
  1995年   4篇
  1994年   12篇
  1993年   8篇
  1992年   2篇
  1991年   3篇
  1990年   3篇
  1987年   6篇
  1986年   4篇
  1985年   3篇
  1984年   2篇
  1982年   2篇
  1980年   2篇
  1979年   2篇
  1978年   1篇
  1977年   5篇
  1975年   2篇
  1973年   1篇
  1972年   1篇
  1970年   1篇
  1968年   1篇
  1966年   1篇
  1962年   1篇
排序方式: 共有628条查询结果,搜索用时 31 毫秒
81.
Review of 20 patients with glucocorticoid deficiency (three cases also with salt loss) associated with absent tear secretion (19 cases) and achalasia of the cardia (15 cases) revealed neurological abnormalities in 17 including hyper-reflexia, muscle weakness, dysarthria, and ataxia together with impaired intelligence and abnormal autonomic function, particularly postural hypotension. These findings indicate that significant neurological problems are common in this multisystem disorder.  相似文献   
82.
83.
84.
This community-based cross-sectional study in 533 participants from 135 households with multiple generations living in the same household aimed at investigating the relationship between Helicobacter pylori infection in children and the other household members. H. pylori infection in children was found significantly associated with the infection in mothers [OR (95% CI): 2.50 (1.19–5.26)], even after being adjusted for sex, age group and sibling number [adjusted OR (95% CI): 2.47 (1.12–5.47)]. It was also significantly associated with the infection in␣both parents [adjusted OR (95% CI): 4.14 (1.29–13.23)]. No significant association between H. pylori infection in the father, grandparent(s), uncle or aunt with that in their children was found. Results from the present study showed intra-familial transmission in a multi-generation population and supported the␣hypothesis of person-to-person transmission of H.␣pylori infection.  相似文献   
85.
Lung neoplasms commonly develop in patients previously treated for head and neck carcinomas. The derivation of these tumors, either as new primary lung cancers or as metastatic head and neck cancers, is difficult to establish based on clinical or histopathologic criteria since both are squamous cell carcinomas and have identical features under light microscopy. However, this distinction has significant treatment and prognostic implications. Gene expression profiling was performed on a panel of 52 sequentially collected patients with either primary lung (n = 21) or primary head and neck (n = 31) carcinomas using the Affymetrix HG_U95Av2 high-density oligonucleotide microarray. Unsupervised hierarchical clustering with Ward linkage and the Pearson correlation metric was performed. To assess robustness, bootstrap resampling was performed with 1,000 iterations. A t test of the normalized values for each gene was used to determine the genes responsible for segregating head and neck from lung primary carcinomas, and those with the most differential expression were used for later analyses. In the absence of a large "test" set of tumors, we used a supervised leave-one-out cross-validation to test how well we could predict the tumor origin. Once a gene expression profile was established, 12 lung lesions taken from patients with previously treated head and neck cancers were similarly analyzed by gene expression profiling to determine their sites of origin. Unsupervised clustering analysis separated the study cohort into two distinct groups which reliably remained segregated with bootstrap resampling. Group 1 consisted of 30 tongue carcinomas. Group 2 consisted of 21 lung cancers and 1 tongue carcinoma. The clustering was not changed even when normal lung or tongue profiles were subtracted from the corresponding carcinomatous lesions, and a leave-one-out cross-validation showed a 98% correct prediction (see Supplementary Data 1). A minimum set of 500 genes required to distinguish these groups was established. Given the ability to segregate these lesions using molecular profiling, we analyzed the lung tumors of undetermined origin. All cases clearly clustered with either lung or tongue tumor subsets, strongly supporting our hypothesis that this technique could elucidate the tissue of origin of metastatic lesions. Although histologically similar, squamous cell carcinomas have distinct gene expression profiles based on their anatomic sites of origin. Accordingly, the application of gene expression profiling may be useful in identifying the derivation of lung nodules and consequently enhances treatment planning.  相似文献   
86.
87.
Aim: Hospital care and advanced medical technologies for sick neonates are increasingly available, but not always readily accessible, in many countries. We characterised parents' and providers' perceptions of barriers to neonatal care in developing countries. Methods: We interviewed parents whose infant was hospitalised within the first month of life in Cambodia, Malaysia, Laos and Vietnam, asking about perceived barriers to obtaining newborn care. We also surveyed health-care providers about perceived barriers to providing care. Results: We interviewed 198 parents and 212 newborn care providers (physicians, nurses, midwives, paediatric and nursing trainees). Most families paid all costs of newborn care, which they reported as a hardship. Although newborn care is accessible, 39% reported that hospitals are too distant; almost 20% did not know where to obtain care. Parents cited lack of cleanliness (46%), poor availability of medications (42%) or services (36%), staff friendliness (42%), poor infant outcome (45%), poor communications with staff (44%) and costs of care (34%) as significant problems during prior newborn care. Providers cited lack of equipment (74%), lack of staff training (61%) and poor infrastructure (51%) as barriers to providing neonatal care. Providers identified distance to hospital, lack of transportation, care costs and low parental education as barriers for families. Conclusions: Improving cleanliness, staff friendliness and communication with parents may diminish some barriers to neonatal care in developing countries. Costs of newborn care, hospital infrastructure, distance to hospital, staffing shortages, limited staff training and limited access to medications pose more difficult barriers to remedy.  相似文献   
88.

Background and purpose:

β-Arrestins are critical scaffold proteins that shape spatiotemporal signalling from seven transmembrane domain receptors (7TMRs). Here, we study the association between neuropeptide Y (NPY) receptors and β-arrestin2, using bimolecular fluorescence complementation (BiFC) to directly report underlying protein–protein interactions.

Experimental approach:

Y1 receptors were tagged with a C-terminal fragment, Yc, of yellow fluorescent protein (YFP), and β-arrestin2 fused with the complementary N-terminal fragment, Yn. After Y receptor–β-arrestin association, YFP fragment refolding to regenerate fluorescence (BiFC) was examined by confocal microscopy in transfected HEK293 cells. Y receptor/β-arrestin2 BiFC responses were also quantified by automated imaging and granularity analysis.

Key results:

NPY stimulation promoted association between Y1–Yc and β-arrestin2–Yn, and the specific development of BiFC in intracellular compartments, eliminated when using non-interacting receptor and arrestin mutants. Responses developed irreversibly and were slower than for downstream Y1 receptor–YFP internalization, a consequence of delayed maturation and stability of complemented YFP. However, β-arrestin2 BiFC measurements delivered appropriate ligand pharmacology for both Y1 and Y2 receptors, and demonstrated higher affinity of Y1 compared to Y2 receptors for β-arrestin2. Receptor mutagenesis combined with β-arrestin2 BiFC revealed that alternative arrangements of Ser/Thr residues in the Y1 receptor C tail could support β-arrestin2 association, and that Y2 receptor–β-arrestin2 interaction was enhanced by the intracellular loop mutation H155P.

Conclusions and implications:

The BiFC approach quantifies Y receptor ligand pharmacology focused on the β-arrestin2 pathway, and provides insight into mechanisms of β-arrestin2 recruitment by activated and phosphorylated 7TMRs, at the level of protein–protein interaction.  相似文献   
89.
90.
Three saponins, oleanolic acid-28- O -ß-D-glucopyranoside (1), chikusetsusaponin V (2), and 3- O -ß-D-glucopyranosyl-oleanolic acid-28- O -ß-D-glucopyranoside (3) were isolated from the roots of Achyranthes bidentata Blume (Amaranthaceae). No activity was shown in the granulocyte phagocytosis test nor in the test of the potentiation of the cytotoxicity of cisplatin in human colon cancer cells. This is the first report of compounds 1, 2 and 3 isolated from Achyranthes species. Furthermore, the NMR data of 2 completed the partially published data.  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