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   227篇
  免费   3篇
  国内免费   1篇
电工技术   4篇
综合类   1篇
化学工业   23篇
金属工艺   3篇
机械仪表   4篇
建筑科学   8篇
轻工业   32篇
水利工程   2篇
石油天然气   1篇
无线电   12篇
一般工业技术   52篇
冶金工业   55篇
原子能技术   4篇
自动化技术   30篇
  2022年   3篇
  2021年   2篇
  2020年   3篇
  2019年   7篇
  2018年   7篇
  2017年   2篇
  2016年   6篇
  2015年   3篇
  2014年   4篇
  2013年   12篇
  2012年   5篇
  2011年   13篇
  2010年   10篇
  2009年   9篇
  2008年   4篇
  2007年   5篇
  2006年   10篇
  2005年   9篇
  2004年   9篇
  2003年   3篇
  2002年   6篇
  2001年   5篇
  2000年   6篇
  1999年   4篇
  1998年   17篇
  1997年   7篇
  1996年   9篇
  1995年   6篇
  1994年   5篇
  1993年   3篇
  1992年   1篇
  1991年   1篇
  1990年   4篇
  1988年   1篇
  1987年   1篇
  1986年   3篇
  1985年   4篇
  1983年   2篇
  1982年   5篇
  1980年   2篇
  1979年   1篇
  1978年   2篇
  1977年   2篇
  1976年   2篇
  1973年   3篇
  1966年   1篇
  1928年   2篇
排序方式: 共有231条查询结果,搜索用时 15 毫秒
131.
Potassium hydroxide (KOH) in dimethyl sulfoxide (DMSO) forms a superbasic medium that allows one to access cross‐coupling products from reactions between aryl halides with various sulfur‐, oxygen‐ and nitrogen‐based nucleophiles under transition metal‐free conditions.  相似文献   
132.
This paper addresses job shop scheduling with sequence dependent family set-ups. Based on a simple, single-machine dynamic scheduling problem, state dependent scheduling rules for the single machine problem are developed and tested using Markov Decision Processes. Then, a generalized scheduling policy for the job shop problem is established based on a characterization of the optimal policy. The policy is combined with a 'forecasting' mechanism to utilize global shop floor information for local dispatching decisions. Computational results show that performance is significantly better than that of existing alternative policies.  相似文献   
133.
Traditional new product development aims to integrate people, tools, and technology to shorten time-to-market and boost economic gains. Under the triple bottom line of sustainability, the integration with the environment brings an additional layer of complexity. Sustainable new product development (SNPD) is a new and ever-growing research area. This paper offers a novel combination of systematic literature review and bibliometric analysis of themes in SNPD in the past 25 years. The search for the relevant literature in Scopus citation database returned 1541 peer-reviewed papers. The analysis of co-occurrence of keywords identified the main themes of product life cycle, product design, sustainable products, production and environmental standards, innovation, human component of sustainability, supply chains, polymer, and renewable resource. Concerns with economic and environmental sustainability were present since the early research on SNPD. However, there is a growing concern with a holistic approach to SNDP integrating people, the economy, and the planet. The evolution of themes showed a need to integrate further the social aspects of sustainability into SNDP. A research agenda closes the paper proposing themes that deserve further scrutiny, related to sustainable products, product life cycle, and product design.  相似文献   
134.
135.
136.
Our study was designed to evaluate the pharmacokinetics, tissue distribution, toxicity and therapeutic efficacy of liposome-encapsulated paclitaxel (LET) in comparison to conventional paclitaxel. In normal mice, LET was much less toxic than the conventional drug. A dose of 32.5 mg/kg of conventional paclitaxel administered i.v. on three consecutive days produced 100% mortality by day three, while liposomal paclitaxel exhibited no mortality. The control group which received Diluent 12 (Chremophor EL and ethanol; 1:1 v/v), a vehicle used in conventional paclitaxel, 30% mortality was observed at this dosage level. In murine ascitic L1210 leukemia model, liposomal paclitaxel and conventional paclitaxel showed comparable antitumor activity. The pharmacokinetics of conventional paclitaxel and LET was studied in mice at dose levels of 5 mg/kg and 20 mg/kg. After intravenous administration of conventional paclitaxel at a dose of 5 mg/kg, the area under the plasma-concentration-time curve (AUC) was 2-fold lower and, the elimination half-life was 2-times shorter compared to LET. At a dose of 20 mg/kg, the terminal half-lives were comparable, however, conventional paclitaxel displayed non-linear pharmacokinetics with disproportionate increase in AUC. At the two dose levels studied, LET demonstrated linear kinetics. Tissue distribution of paclitaxel after administration of LET showed levels 10-fold higher in spleen and 3.5-fold higher in liver as compared to conventional paclitaxel. The significant decrease in toxicity shown by LET, coupled with an increase in plasma AUC and half-life indicates that LET may be a viable alternative to the therapeutic use of the conventional preparation of paclitaxel.  相似文献   
137.
Villous trophoblast in the human placenta consists of a population of proliferating stem cells which differentiate and individually fuse into the syncytiotrophoblast. We studied the apoptotic cascade in this complex epithelial layer by immunohistochemical localization of Fas, FasL, Bcl-2, Mcl-1, pro-caspase-3 and caspase-3, T-cell-restricted intracellular antigen-related protein (TIAR), poly(ADP-ribose) polymerase (PARP), lamin B, topoisomerase IIalpha, and transglutaminase II in cryostat and paraffin-fixed tissue sections from normal human first-trimester and term placental villi. The relationship between the apoptotic cascade and syncytial fusion was studied by coincubation of intact villi with FITC-coupled annexin-V, to detect the phosphatidylserine flip, and propidium iodide, to detect plasma membrane permeability. The final events of the apoptotic cascade were studied by the TUNEL reaction and ultrastructural appearance of the trophoblast. The phosphatidylserine flip was identified in some of the villous cytotrophoblastic cells, but the presence of both Bcl-2 and Mcl-1 proteins presumably prevented continuation of the apoptotic cascade. The syncytiotrophoblast demonstrated heterogeneous findings, suggesting variable progression along the apoptotic cascade. In some areas Bcl-2 and Mcl-1 predominated, with preservation of the nuclear proteins PARP, lamin B, and topoisomerase IIalpha; in other areas, especially in and around syncytial sprouts, Bcl-2 and Mcl-1 were absent, accompanied by loss of nuclear proteins, presence of phosphatidylserine flip, and TUNEL positivity. These data suggest that the apoptotic cascade is initiated in the villous cytotrophoblast, which in turn promotes syncytial fusion. Donation of anti-apoptotic proteins into the syncytium, such as Bcl-2 and Mcl-1, focally inhibits further progression along this cascade. Completion of the apoptotic cascade takes place in and around syncytial sprouts, providing further evidence that these are the sites of trophoblast shedding into the maternal circulation.  相似文献   
138.
This article provides an overview of ITU-T Recommendation H.323, “Visual telephone systems and equipment for local area networks which provide a non-guaranteed quality of service.” This recommendation applies to multimedia communications over packet-switched networks, such as Ethernet, which run TCP/IP, IXP/SPX, or other related protocols. In addition to the multimedia terminal, other H.323 components are defined which provide for conference admissions (gatekeeper), multipoint communications (multipoint controller, multipoint processor), and interoperability (gateway) with terminals on other types of networks. H.323 has application to a variety of network media, including local area networks, enterprise networks, metropolitan area networks, wide area networks, dial-up line connections to LANs, and the Internet. This provides the capability to have global multimedia communications from the desktop using existing network infrastructures  相似文献   
139.
140.
Little is known about how the vascular reactivity of the coronary microcirculation is affected by upstream atherosclerotic disease. We have examined, with a wire myograph, the responses of intramyocardial arteries from hearts in which the epicardial vessels were either free of atherosclerotic lesions (non-diseased group) or were affected by atherosclerosis (diseased group). Vasodilator responses of preconstricted vessels to substance P (84.1 +/- 12.6 compared to 42.0 +/- 19.7%) were less in vessels from the diseased group (p < 0.05). In contrast, the relaxation to bradykinin (70.2 +/- 21.2 compared to 100.6 +/- 7.9%) was increased in vessels from the diseased group (p < 0.05). The dilator responses to acetylcholine, adenosine diphosphate, histamine and sodium nitroprusside showed no significant differences between arteries from each group. 5-Hydroxytryptamine was without any significant vasodilator effect in arteries from either group. Assessment of contractile function revealed that the responses to 5-hydroxytryptamine, acetylcholine, U46619, endothelin-1 and L-N(G)-monomethylarginine in each group were not significantly different. Histamine, noradrenaline and dopamine were without any significant contractile response. These results demonstrate that upstream atherosclerosis does not confer any global impairment of endothelium-dependent vasorelaxant responses or smooth muscle hyperreactivity to vasoconstrictors in the arteries that penetrate the myocardium.  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