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   4752篇
  免费   210篇
  国内免费   5篇
电工技术   54篇
综合类   4篇
化学工业   971篇
金属工艺   80篇
机械仪表   116篇
建筑科学   166篇
矿业工程   29篇
能源动力   108篇
轻工业   380篇
水利工程   65篇
石油天然气   12篇
无线电   284篇
一般工业技术   929篇
冶金工业   1169篇
原子能技术   34篇
自动化技术   566篇
  2023年   25篇
  2022年   48篇
  2021年   82篇
  2020年   60篇
  2019年   90篇
  2018年   85篇
  2017年   78篇
  2016年   109篇
  2015年   79篇
  2014年   111篇
  2013年   274篇
  2012年   218篇
  2011年   313篇
  2010年   231篇
  2009年   206篇
  2008年   266篇
  2007年   248篇
  2006年   215篇
  2005年   186篇
  2004年   155篇
  2003年   132篇
  2002年   124篇
  2001年   99篇
  2000年   80篇
  1999年   76篇
  1998年   126篇
  1997年   105篇
  1996年   93篇
  1995年   81篇
  1994年   68篇
  1993年   73篇
  1992年   80篇
  1991年   35篇
  1990年   62篇
  1989年   61篇
  1988年   48篇
  1987年   56篇
  1986年   34篇
  1985年   34篇
  1984年   48篇
  1983年   38篇
  1982年   42篇
  1981年   34篇
  1980年   34篇
  1979年   21篇
  1978年   25篇
  1977年   24篇
  1976年   25篇
  1975年   21篇
  1973年   19篇
排序方式: 共有4967条查询结果,搜索用时 473 毫秒
1.
The noninvasive sampling of dermal interstitial fluid (ISF) for the monitoring of clinical biomarkers is a greatly appealing area of research. The identification of molecular biomarkers in biological fluids has been accelerated with -omics analyses but remains limited in ISF because of its time-consuming and complex extraction process. Here, the generation of microneedle (MN) patches made of superabsorbent acrylate-based hydrogels for the rapid sampling of dermal ISF is described to explore its proteome. In depth, iterative optimization allows the identification of novel acrylate-based compositions with the required chemical, mechanical, and biocompatibility properties allowing proteomic analysis of the extracted ISF for the first time after sampling with swelling MNs. The generated MN arrays show no cytotoxic effect, successfully cross the stratum corneum, and can collect up to 6 µL of dermal ISF in 10 min in vivo. Proteomics lead to the detection of 176 clinically relevant biomarkers in the collected samples validating the use of ISF as a relevant bodily fluid for disease monitoring and diagnostic. Importantly, it is discovered that extraction fingerprint is strongly dependent on the MNs chemistry, and thus specific biomarkers could be selectively extracted by tuning the composition of the patch, making the system versatile and specific.  相似文献   
2.
Tumor suppressor genes such as p53 contribute to the oncogenic process via loss-of-function mechanisms such as genetic mutation or complex formation with other cellular or viral proteins. p53 is mutated in approximately 50% of human tumors and has an important role in the genesis or progression of both colorectal and hepatocellular cancers. Colorectal cancer is leading cause of cancer mortality in the United States, whereas hepatocellular cancer is the leading worldwide cause of cancer death; the liver is a primary site of morbidity in both diseases. Because systemic tumor suppressor gene therapy is currently not feasible, we have chosen to develop a regional form of such therapy directed at primary or metastatic liver neoplasms. Gene replacement therapy with p53 is a promising new strategy to treat advanced human cancers.  相似文献   
3.
New IS technology is contributing to continuous quality improvement throughout the organization. Hypertext and hypermedia offer new ways for decision makers to gain easy and relevant access to information. By combining hypertext with total quality tools, decision makers are able to explore the richness of data bases in more creative and useful ways. This article describes how you can develop a hypertext system that can help employees improve their job performance through better problem solving.  相似文献   
4.
Several methodological and ethical issues are addressed in the context of 3 related school-based studies of the primary and targeted prevention of depressive symptoms and disorder in high school adolescents. These issues include obtaining S consent and the protection of confidentiality, minimizing attrition over long-term follow-up periods, the "unit of assignment" issue common to most school-based research, and ensuring therapist fidelity to the intervention protocol. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
5.
6.
Interest in medical savings accounts (MSAs) as a potential tool to reduce healthcare costs has been widespread. A small number of countries have either implemented or run pilot programs of MSAs, and vigorous policy debates have taken place in several other countries about the potential merits of introducing MSAs as a method of paying for health care. In this paper we develop a model to assess the cost saving potential of MSAs in a publicly funded healthcare system. We assume that the public healthcare payer may choose between reimbursing healthcare expenditures through an MSA or through a form of third‐party payer insurance. We use the model to identify the conditions under which MSAs may reduce costs. We illustrate using data on healthcare expenditures from Canada.  相似文献   
7.
Nanostructured polymer blends prepared via anionic ring opening polymerizations of cyclic monomers in the presence of a pre-made polymer melt exhibit a number of special properties over traditional polymer blends and homopolymers. Here, we report on a simple and versatile method of in situ polymerization of macrocyclic carbonates in the presence of a maleic anhydride polypropylene (mPP) matrix and a surface-active compatibilizer (i.e. PC grafted onto a mPP backbone generated in situ) to yield a micro- and nanostructured polymer blends consisting of a polycarbonate (PC) minor phase, and a polypropylene (PP) major phase. By varying the processing conditions and concentration of the macrocyclic carbonate it was possible to reduce the size of the PC dispersions to an average minor diameter of 150 nm. NMR and TEM characterizations indicate that the PC dispersions do not influence crystal content in the PP phase. Overall, the results point to a simple strategy and versatile route to new polymeric materials with enhanced benefits.  相似文献   
8.
Local Strain Measurement within Tendon   总被引:2,自引:0,他引:2  
Abstract:  Tendon is a dense connective tissue, responsible for transmitting the forces generated by muscles to the skeleton. It is composed of a hierarchical arrangement of crimped collagen fibres, interspersed with proteoglycan matrix and cells, known as tenocytes. During physiological loading, tendons are subjected to strains in the region of 5–6%, which result in the straightening and realignment of the collagen fibres, generating variable local strain fields within the tendon. This study demonstrates a technique for analysing local strains within viable tendon explants, during both loading and unloading of the tissue. Samples were strained in a custom-designed rig, allowing real-time visualisation of cell nuclei, used as local discrete markers, on a confocal microscope. Results indicated that local strains within the fascicle are smaller than the applied strains, never exceeding 1.2%, even at 8% gross applied strain. By contrast, the sliding of adjacent collagen units was recorded at each strain increment in this study, reaching a mean maximum of 3.9% of the applied displacement. Loading–unloading studies indicated that sliding behaviour is reversible up to strains of 5%, and provides the major extension mechanism within the rat-tail tendon. This technique can be extended to further analyse shearing behaviour within the matrix.  相似文献   
9.
10.
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