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   3623篇
  免费   128篇
  国内免费   8篇
电工技术   38篇
综合类   1篇
化学工业   970篇
金属工艺   97篇
机械仪表   91篇
建筑科学   123篇
矿业工程   12篇
能源动力   97篇
轻工业   481篇
水利工程   23篇
石油天然气   19篇
无线电   240篇
一般工业技术   780篇
冶金工业   161篇
原子能技术   23篇
自动化技术   603篇
  2024年   28篇
  2023年   63篇
  2022年   69篇
  2021年   145篇
  2020年   114篇
  2019年   119篇
  2018年   178篇
  2017年   164篇
  2016年   197篇
  2015年   137篇
  2014年   173篇
  2013年   351篇
  2012年   199篇
  2011年   225篇
  2010年   191篇
  2009年   177篇
  2008年   136篇
  2007年   93篇
  2006年   67篇
  2005年   39篇
  2004年   49篇
  2003年   49篇
  2002年   48篇
  2001年   46篇
  2000年   41篇
  1999年   31篇
  1998年   52篇
  1997年   47篇
  1996年   35篇
  1995年   25篇
  1994年   33篇
  1993年   27篇
  1992年   17篇
  1991年   20篇
  1990年   15篇
  1987年   19篇
  1986年   13篇
  1985年   30篇
  1984年   26篇
  1983年   21篇
  1982年   23篇
  1981年   24篇
  1980年   17篇
  1979年   14篇
  1978年   13篇
  1977年   19篇
  1976年   19篇
  1975年   16篇
  1974年   14篇
  1973年   17篇
排序方式: 共有3759条查询结果,搜索用时 31 毫秒
1.
Summary After a 10 year interval from the first state-wide registration of landslides, a new system of landslide register is being introduced in Czechoslovakia in relation to the transfer to the Geological Data Bank system for processing by electronic computer. Each recorded phenomenon is plotted on a map and described. The final record is made by means of a code on a punched register card ready for computerizing. In the field, however, a questionnaire form has to be filled up, arranged in such a way as to enable easy processing. From the field questionnaire, the data are transcribed on to a punched card by means of a numerical or alphabetical code. A review of the data to be recorded is given.
Inventaire Des Glissements de Terrain
Résumé Dix ans après le premier enregistrement national des glissements de terrain, un nouveau système d’enregistrement est en cours d’installation en Tchécoslovaquie, ce qui permettra d’établir la liaison avec le système de la Banque de données géologiques et d’exploiter ces informations avec un ordinateur. Chaque phénomène enregistré est reporté sur une carte et décrit. L’enregistrement final est fait au moyen d’un code sur une carte perforée prête à être utilisée dans l’ordinateur; mais sur le terrain, on devra remplir une formule de questionnaire, préparée pour permettre un traitement aussi facile que possible. Les données du questionnaire de terrain doivent être transcrites sur une carte perforée au moyen d’un code numérique ou alphabétique. On donne la liste des informations à enregistrer.
  相似文献   
2.
This study investigates the effects of wood weathering on changes in its macroscopic and colour characteristics in connection with changes in its molecular and anatomical structure. Seven hardwoods suitable for outdoor architecture—bangkirai, cumaru, cumaru rosa, ipé, jatobá, kusia, and massaranduba—were exposed to the exterior out of ground contact for 1–36 months according to EN 927-3, and for 1–12 weeks in Xenotest with water spraying according to partly modified EN 927-6. With prolonged weathering, the following changes occurred in the top surfaces of all tropical woods: (1) visual—creation of longitudinal macro-cracks, (2) spectrophotometry and CIE-L ? a ? b ? —darkening in exterior exposure mainly due to pollutants, except for ipé, and vice versa lightening in Xenotest, as well as greening and blueing in both modes of exposure, (3) FTIR—faster decrease of guaiacyl than syringyl lignin, absolute decrease of conjugated and unconjugated carbonyl groups in the newly formed lignin-polysaccharide-extractive substrate in the photo-oxidized and washed-out cell walls, and decrease of cellulose crystallinity, (4) SEM—damaging of cell-walls by micro-cracks, and their degradation by thinning. Connections between changes of the individual characteristics of weathered woods, for example, between the colour (ΔE*, etc.) and the molecular structure (carbonyls, etc.), were also determined.  相似文献   
3.
4.
Frequent consumption of diet drinks was associated with oocyte dysmorphism, decreased embryo quality, and an adverse effect on pregnancy rate. We investigated the harmful effects of aspartame and potential mechanisms through which it increases infertility risk through clinical observations and in vivo and in vitro studies. Methods: We established a cohort of 840 pregnant women and retrospectively determined their time to conceive. We assessed the estrus cycle, the anti-Mullerian hormone level, ovarian oxidative stress, and ovarian mitochondrial function in an animal study. We also evaluated mitochondria function, mitochondrial biogenesis, and progesterone release with in vitro studies. Aspartame consumption was associated with increased infertility risk in the younger women (Odds ratio: 1.79, 95% confidence interval: 1.00, 3.22). The results of the in vivo study revealed that aspartame disrupted the estrus cycle and reduced the anti-Mullerian hormone level. Aspartame treatment also suppressed antioxidative activities and resulted in higher oxidative stress in the ovaries and granulosa cells. This phenomenon is caused by an aspartame-induced decline in mitochondrial function (maximal respiration, spare respiratory capacity, and ATP production capacity) and triggered mitochondrial biogenesis (assessed by examining the energy depletion signaling-related factors sirtuin-1, phosphorylated adenosine monophosphate-activated protein kinase, peroxisome proliferator-activated receptor-gamma coactivator-1α, and nuclear respiratory factor 1 expression levels). Aspartame may alter fertility by reserving fewer follicles in the ovary and disrupting steroidogenesis in granulosa cells. Hence, women preparing for pregnancy are suggested to reduce aspartame consumption and avoid oxidative stressors of the ovaries.  相似文献   
5.
Homeostasis is a self-regulatory dynamic process that maintains a stable internal environment in the human body. These regulations are essential for the optimal functioning of enzymes necessary for human health. Homeostasis elucidates disrupted mechanisms leading to the development of various pathological conditions caused by oxidative stress. In our work, we discuss redox homeostasis and salivary antioxidant activity during healthy periods and in periods of disease: dental carries, oral cavity cancer, periodontal diseases, cardiovascular diseases, diabetes mellitus, systemic sclerosis, and pancreatitis. The composition of saliva reflects dynamic changes in the organism, which makes it an excellent tool for determining clinically valuable biomarkers. The oral cavity and saliva may form the first line of defense against oxidative stress. Analysis of salivary antioxidants may be helpful as a diagnostic, prognostic, and therapeutic marker of not only oral, but also systemic health.  相似文献   
6.
The multidrug transporter ABCB1 (MDR1, Pgp) plays an important role in the absorption, distribution, metabolism, and elimination of a wide range of pharmaceutical compounds. Functional investigation of the ABCB1 expression is also essential in many diseases, including drug-resistant cancer, inflammatory conditions, or Alzheimer disease. In this study, we examined the potential interaction of the ABCB1 multidrug transporter with a group of commercially available viability dyes that are generally considered not to penetrate into intact cells. Here, we demonstrate that the slow cellular accumulation of TO-PRO™-1 (TP1) or TO-PRO™-3 (TP3) was strongly inhibited by ABCB1-dependent dye extrusion. TP1/3 dye accumulation was not affected by the presence of ABCC1 or ABCG2, while this uptake was increased to the level in the ABCB1-negative cells by a specific P-glycoprotein inhibitor, Tariquidar. We suggest that TP compounds can be used as highly sensitive, selective, non-toxic, and stable dyes to examine the functional expression and properties of the ABCB1 multidrug transporter, especially in microplate-based high-throughput flow cytometry assays. In addition, we demonstrate the applicability of the TP dyes to efficiently select and separate even a very low number of Pgp-expressing intact cells.  相似文献   
7.
8.
Bücher     
Ohne Zusammenfassung VDI  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