全文获取类型
收费全文 | 26446篇 |
免费 | 48篇 |
国内免费 | 93篇 |
专业分类
系统科学 | 187篇 |
丛书文集 | 312篇 |
教育与普及 | 77篇 |
理论与方法论 | 132篇 |
现状及发展 | 11106篇 |
研究方法 | 1211篇 |
综合类 | 13060篇 |
自然研究 | 502篇 |
出版年
2013年 | 167篇 |
2012年 | 417篇 |
2011年 | 947篇 |
2010年 | 159篇 |
2009年 | 157篇 |
2008年 | 448篇 |
2007年 | 528篇 |
2006年 | 533篇 |
2005年 | 535篇 |
2004年 | 596篇 |
2003年 | 501篇 |
2002年 | 493篇 |
2001年 | 792篇 |
2000年 | 778篇 |
1999年 | 522篇 |
1992年 | 476篇 |
1991年 | 379篇 |
1990年 | 418篇 |
1989年 | 396篇 |
1988年 | 368篇 |
1987年 | 417篇 |
1986年 | 425篇 |
1985年 | 521篇 |
1984年 | 419篇 |
1983年 | 336篇 |
1982年 | 276篇 |
1981年 | 286篇 |
1980年 | 357篇 |
1979年 | 844篇 |
1978年 | 650篇 |
1977年 | 628篇 |
1976年 | 510篇 |
1975年 | 540篇 |
1974年 | 768篇 |
1973年 | 666篇 |
1972年 | 632篇 |
1971年 | 800篇 |
1970年 | 1091篇 |
1969年 | 772篇 |
1968年 | 659篇 |
1967年 | 765篇 |
1966年 | 703篇 |
1965年 | 486篇 |
1959年 | 261篇 |
1958年 | 454篇 |
1957年 | 308篇 |
1956年 | 295篇 |
1955年 | 232篇 |
1954年 | 218篇 |
1948年 | 234篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
Margherita Ratti Andrea Lampis Jens C. Hahne Rodolfo Passalacqua Nicola Valeri 《Cellular and molecular life sciences : CMLS》2018,75(22):4151-4162
Gastric cancer is one of the most aggressive malignancies, with limited treatment options in both locally advanced and metastatic setting, resulting in poor prognosis. Based on genomic characterization, stomach tumour has recently been described as a heterogeneous disease composed by different subtypes, each of them with peculiar molecular aspects and specific clinical behaviour. With an incidence of 22% among all western gastric tumour cases, stomach cancer with microsatellite instability was identified as one of these subgroups. Retrospective studies and limited prospective trials reported differences between gastric cancers with microsatellite stability and those with instability, mainly concerning clinical and pathological features, but also in regard to immunological microenvironment, correlation with prognostic value, and responses to treatment. In particular, gastric cancer with microsatellite instability constitutes a small but relevant subgroup associated with older age, female sex, distal stomach location, and lower number of lymph-node metastases. Emerging data attribute to microsatellite instability status a favourable prognostic meaning, whereas the poor outcomes reported after perioperative chemotherapy administration suggest a detrimental role of cytotoxic drugs in this gastric cancer subgroup. The strong immunogenicity and the widespread expression of immune-checkpoint ligands make microsatellite instability subtype more vulnerable to immunotherapeutic approach, e.g., with anti-PD-L1 and anti-CTLA4 antibodies. Since gastric cancer with microsatellite instability shows specific features and clinical behaviour not overlapping with microsatellite stable disease, microsatellite instability test might be suitable for inclusion in a diagnostic setting for all tumour stages to guarantee the most targeted and effective treatment to every patient. 相似文献
2.
Patricio Atanes Inmaculada Ruz-Maldonado Ross Hawkes Bo Liu Min Zhao Guo Cai Huang Israa Mohammed Al-Amily Albert Salehi Stefan Amisten Shanta J. Persaud 《Cellular and molecular life sciences : CMLS》2018,75(16):3039-3050
Introduction
Islets synthesise and secrete numerous peptides, some of which are known to be important regulators of islet function and glucose homeostasis. In this study, we quantified mRNAs encoding all peptide ligands of islet G protein-coupled receptors (GPCRs) in isolated human and mouse islets and carried out in vitro islet hormone secretion studies to provide functional confirmation for the species-specific role of peptide YY (PYY) in mouse islets.Materials and methods
GPCR peptide ligand mRNAs in human and mouse islets were quantified by quantitative real-time PCR relative to the reference genes ACTB, GAPDH, PPIA, TBP and TFRC. The pathways connecting GPCR peptide ligands with their receptors were identified by manual searches in the PubMed, IUPHAR and Ingenuity databases. Distribution of PYY protein in mouse and human islets was determined by immunohistochemistry. Insulin, glucagon and somatostatin secretion from islets was measured by radioimmunoassay.Results
We have quantified GPCR peptide ligand mRNA expression in human and mouse islets and created specific signalomes mapping the pathways by which islet peptide ligands regulate human and mouse GPCR signalling. We also identified species-specific islet expression of several GPCR ligands. In particular, PYY mRNA levels were ~ 40,000-fold higher in mouse than human islets, suggesting a more important role of locally secreted Pyy in mouse islets. This was confirmed by IHC and functional experiments measuring insulin, glucagon and somatostatin secretion.Discussion
The detailed human and mouse islet GPCR peptide ligand atlases will allow accurate translation of mouse islet functional studies for the identification of GPCR/peptide signalling pathways relevant for human physiology, which may lead to novel treatment modalities of diabetes and metabolic disease.3.
Raza Syed Arshad Siddiqui Atiq W. Standing Craig 《Systemic Practice and Action Research》2019,32(2):125-153
Systemic Practice and Action Research - Most of the traditional technology acceptance models revolve around information systems (IS)/information technology (IT) adoption at individual user level.... 相似文献
4.
5.
系统地总结和介绍了我国高性能计算机,包括“银河”系列巨型机、“曙光”系列巨型机、“神威”系列巨型机、“深腾”系列巨型机以及“深超”系列巨型机的开发研制以及应用情况。 相似文献
6.
刘伟霞 《科技情报开发与经济》2004,14(6):147-148
对矿井索车优化设计中的几个关键性问题进行了探讨,包括驱动轮和尾轮的设计、钢丝绳直径的选择计算、托绳轮间距的确定、绳卡的设计、张紧力和张紧行程的确定、互锁问题的解决等。 相似文献
7.
董文伟 《科技情报开发与经济》2004,14(6):296-297
以具体工程为例,介绍了建筑物地基处理的设计、施工中遵循的原则,施工中遇到特殊情况时采取的处理方法和必要的检测方法,对几种桩基的设计要求、施工工艺及过程、质量控制等情况进行了简单阐述。 相似文献
8.
王永红 《科技情报开发与经济》2004,14(6):139-141
通过1998年、2000年的试验研究,系统分析了顶凌覆盖技术在高寒区节水增温保温、增产增收的机理及其应用效果。提出该技术可以缓解低温干旱特别是春旱对农业生产的困扰,是一项可以抗旱保春播增产增收的实用技术,在高寒地区具有较高的推广价值。 相似文献
9.
Ten-day treatment with nicotine (5, 25 or 50 micrograms/ml drinking water) dose-dependently intensified gastric ulceration induced by cold-restraint, and emptying rate. Stomach contractions produced by graded doses of bethanechol i.v. were elevated further by nicotine treatment. It is suggested that chronic nicotine administration produces hypersensitivity of the gastric muscarinic receptors; stomach hypermotility contributes to the ulcer-worsening action of the alkaloid. 相似文献
10.
新的、高密度树木种植正在给林业生物技术带来迅速的变化。但是如果不能克服生态风险和经济障碍.这些新的方法或许永远也无法使用—— 相似文献