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   659篇
  免费   29篇
  国内免费   2篇
综合类   1篇
化学工业   96篇
金属工艺   5篇
机械仪表   9篇
建筑科学   19篇
能源动力   9篇
轻工业   55篇
水利工程   2篇
无线电   190篇
一般工业技术   120篇
冶金工业   88篇
原子能技术   1篇
自动化技术   95篇
  2023年   4篇
  2022年   2篇
  2021年   15篇
  2020年   14篇
  2019年   10篇
  2018年   23篇
  2017年   16篇
  2016年   19篇
  2015年   13篇
  2014年   13篇
  2013年   32篇
  2012年   23篇
  2011年   25篇
  2010年   24篇
  2009年   15篇
  2008年   25篇
  2007年   26篇
  2006年   17篇
  2005年   15篇
  2004年   28篇
  2003年   25篇
  2002年   23篇
  2001年   19篇
  2000年   17篇
  1999年   13篇
  1998年   25篇
  1997年   30篇
  1996年   19篇
  1995年   10篇
  1994年   21篇
  1993年   17篇
  1992年   7篇
  1991年   17篇
  1990年   16篇
  1989年   12篇
  1988年   10篇
  1987年   3篇
  1986年   2篇
  1985年   8篇
  1984年   8篇
  1983年   4篇
  1982年   2篇
  1981年   5篇
  1980年   4篇
  1979年   4篇
  1977年   4篇
  1976年   4篇
  1967年   1篇
  1964年   1篇
排序方式: 共有690条查询结果,搜索用时 15 毫秒
91.
The nutritional and antioxidant properties of peels, pulp and seeds of kembayau (Dacryodes rostrata) fruits were evaluated. Kembayau seeds and pulp were rich in fat, while peels had the highest ash contents. Potassium was the most prevalent mineral in peels (380.72-1112.00 mg/100 g). In kembayau fruits, total flavonoid content (1012.74-28,022.28 mg rutin equivalent/100 g) was higher than total phenolic and total monomeric anthocyanin contents. Kembayau seeds exhibited high flavonoid and phenolic contents compared to the contents in peels and pulp. Antioxidant capacities were also higher in seeds as typified by trolox equivalent antioxidant capacity assay (51.39-74.59 mmol TE/100 g), ferric reducing antioxidant power assay (530.05-556.98 mmol Fe2+/100 g) and by 1,1-diphenyl-2-picryl hydrazyl radical scavenging activity (92.18-92.19%) when compared to peels and pulp. Pulp and peels of kembayau fruit may be an important source of energy and minerals for human consumption, while seeds have a good potential as antioxidants.  相似文献   
92.
Connectors are developed to satisfy the needs of advanced technology in telecommunication switching systems and companies have several products designed to fulfil the needs of the many switching networks available. The Four-wall-header is one such product from one company. The traditional manufacturing line relies heavily on hard tooling which is both expensive and time-consuming. This paper presents an alternative method of integrating rapid prototyping technologies, in particular, stereolithography apparatus (SLA), with a vacuum casting system to produce a wide range of polyurethane parts. Altogether, three approaches are analysed and evaluated for making the moulds: rapid pattern, rapid tooling and a hybrid approach.  相似文献   
93.
Recent studies have shown a high frequency of genetic hemochromatosis in the Caucasian population. In addition, the well known organ involvement of genetic hemochromatosis was evident; more than 50% of patients develop a typical arthropathy which may result in severe physical disability. Among approximately 5000 patients referred to the rheumatology outpatient clinics of Bad Nauheim and Frankfurt with different rheumatologic diagnoses, 11 patients with typical signs of hemochromatotic arthropathy were identified. In none of those cases had the diagnosis "genetic hemochromatosis" been previously established. These patients had been treated for rheumatoid arthritis and other rheumatologic disorders over several years. All showed severe organ dysfunction due to iron overload, resulting in a reduced life expectancy. This investigation shows that knowledge of the typical signs of hemochromatotic arthropathy could lead to an earlier diagnosis of genetic hemochromatosis which is necessary to prevent the complications of iron overload in those patients.  相似文献   
94.
This paper establishes new criteria for stochastic suppression and stabilization of hybrid functional differential systems with general 1‐sided polynomial growth condition. For an unstable nonlinear hybrid functional differential system with general 1‐sided polynomial growth condition, 2 independent Brownian noise processes are used to perturb the system into the stochastic hybrid differential system. Theoretical analysis shows that one of the nonlinear diffusion terms may suppress the explosive solution of deterministic system, and the other one can make the perturbed hybrid system almost surely stable with general decay rate.  相似文献   
95.
This paper studies a storage yard management problem in a transshipment hub where the loading and unloading activities are both heavy and concentrated. In order to reduce the number of reshuffles, which helps to reduce the vessel turnaround time, the port operator uses the consignment strategy to group export and transshipment containers according to their destination vessel. To reduce the potential traffic congestion of prime movers, a high–low workload balancing protocol is used. A mixed integer programming model is formulated to determine the storage locations of incoming containers, the number of incoming containers and the smallest number of yard cranes to deploy in each shift. An iterative improvement method is developed to solve the problem, in which a tabu search based heuristic algorithm is used to generate an initial yard template, and then the generated yard template is improved by an improvement algorithm iteratively until an optimal or a satisfactory solution is obtained. Experiment results show that the proposed method can generate excellent results within a reasonable time, even for the extreme cases.  相似文献   
96.
97.
A simple steam-assisted solid phase synthesis method was developed for synthesis of boehmite nanowires in the presence of TEAOH surfactant. The boehmite nanowires had uniform diameters (12-16 nm) and length up to 1-2 microm. The morphology of the nanostructured wires was well preserved after being converted to pure gamma-Al2O3 by thermal treatment at 600 degrees C for 5 h. The nanowires of Al2O3 exhibited excellent thermal stability by retarding the phase transformation and maintaining the wires-like nanostructure after being aged up to 1300 degrees C by preventing sintering between particles at high temperatures. The surface areas of Al2O3 nanowires could be maintained as high as 68 m2/g at 1300 degrees C while the surface areas of Al2O3 micropowder shrank to 0.89 m2/g after same thermal treatment. Both in-situ XRD and 27Al NMR results indicated that the crystal structure of gamma-Al2O3 nanowires was not transformed to alpha-Al2O3 at 1300 degrees C whereas micropowder Al2O3 was fully converted to alpha-Al2O3 at 1100 degrees C.  相似文献   
98.
In this work, we study a liner shipping operational problem which considers how to dynamically determine the vessel speed and refueling decisions, for a single vessel in one service route. Our model is a multi-stage dynamic model, where the stochastic nature of the bunker prices is represented by a scenario tree structure. Also, we explicitly incorporate the uncertainty of bunker consumption rates into our model. As the model is a large-scale mixed integer programming model, we adopt a modified rolling horizon method to tackle the problem. Numerical results show that our framework provides a lower overall cost and more reliable schedule compared with the stationary model of a related work.  相似文献   
99.
We report a patient with a metastatic parathyroid carcinoma and medullary carcinoma of the thyroid. This patient represents a variation of the multiple endocrine neoplasia syndrome (MEN) type 2A. There was no evidence of a phaeochromocytoma. The case illustrates the difficulties that may be encountered in localising the source of PTH secretion; the patient underwent four unsuccessful exploratory operations of the neck and mediastinum before further investigations revealed a single metastatic deposit of parathyroid carcinoma involving the first thoracic vertebra. PCR amplification and sequencing of the RET oncogene from the metastatic parathyroid carcinoma and genomic DNA revealed a heterozygous mutation (Cys634Tyr) in exon 11, as has previously been described to occur in MEN 2A. In addition, loss of tumour heterozygosity was demonstrated at loci from chromosomes 1, 2, 3p, 13q and 16p. This represents the first report of a parathyroid carcinoma in a MEN2A patient, in which the multiple allelic deletions are consistent with the generalised losses observed in aggressive tumours.  相似文献   
100.
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