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   3802篇
  免费   292篇
  国内免费   119篇
电工技术   101篇
综合类   208篇
化学工业   1113篇
金属工艺   91篇
机械仪表   109篇
建筑科学   477篇
矿业工程   30篇
能源动力   114篇
轻工业   418篇
水利工程   39篇
石油天然气   229篇
武器工业   64篇
无线电   146篇
一般工业技术   690篇
冶金工业   65篇
原子能技术   15篇
自动化技术   304篇
  2024年   9篇
  2023年   56篇
  2022年   82篇
  2021年   73篇
  2020年   106篇
  2019年   113篇
  2018年   112篇
  2017年   144篇
  2016年   151篇
  2015年   122篇
  2014年   202篇
  2013年   216篇
  2012年   237篇
  2011年   232篇
  2010年   161篇
  2009年   208篇
  2008年   188篇
  2007年   253篇
  2006年   215篇
  2005年   175篇
  2004年   179篇
  2003年   156篇
  2002年   123篇
  2001年   127篇
  2000年   103篇
  1999年   88篇
  1998年   75篇
  1997年   66篇
  1996年   55篇
  1995年   39篇
  1994年   21篇
  1993年   16篇
  1992年   29篇
  1991年   22篇
  1990年   23篇
  1989年   7篇
  1988年   6篇
  1987年   4篇
  1986年   4篇
  1985年   2篇
  1984年   1篇
  1983年   1篇
  1982年   1篇
  1981年   3篇
  1980年   2篇
  1979年   1篇
  1976年   2篇
  1967年   1篇
  1963年   1篇
排序方式: 共有4213条查询结果,搜索用时 15 毫秒
1.
Context: The administration of pharmabiotics is a promising alternative to antimicrobial drugs for the treatment and/or prevention of female urogenital infections.

Objective: To design pharmabiotic formulations including bioactive ingredients of microbial origin combined with non-microbial substances and then to evaluate the stability of the combinations during freeze-drying and storage.

Materials and methods: Different formulations including Lactobacillus gasseri CRL 1263, Lactobacillus salivarius CRL 1328, salivaricin CRL 1328 (a bacteriocin) and non-microbial compounds (lactose, inulin and ascorbic acid) were assayed, and the ingredients were freeze-dried together or separately. The formulations were stored in gelatin capsules at 4?°C for 360?d.

Results: The viability of lactobacilli was affected to different extents depending on the strains and on the formulations assayed. L. salivarius and ascorbic acid were successfully combined only after the freeze-drying process. Salivaricin activity was not detected in formulations containing L. gasseri. However, when combined with ascorbic acid, lactose, inulin or L. salivarius, the bacteriocin maintained its activity for 360?d. The selected microorganisms proved to be compatible for their inclusion in multi-strain formulations together with lactose, inulin and ascorbic acid. Salivaricin could be included only in a L. salivarius CRL 1328 single-strain formulation together with non-microbial substances.

Conclusions: This study provides new insights into the design of urogenital pharmabiotics combining beneficial lactobacilli, salivaricin CRL 1328 and compounds with different functionalities.  相似文献   
2.
报导一种模糊逻辑控制系统的建模与优化方法。以此方法设计的模糊逻辑控制器,用于双波长稳频CO2激光器的控制得到令人满意的结果。  相似文献   
3.
防治水泥稳定碎石基层沥青路面裂缝的措施浅析   总被引:3,自引:0,他引:3  
水泥稳定碎石基层沥青路面裂缝产生的原因复杂 ,但非荷载型裂缝更为主要。防治水泥稳定碎石基层沥青路面的裂缝应该从设计和施工两方面考虑 ,其中由结构、材料组成设计 ,以及施工工艺出发控制水泥稳定碎石基层本身的收缩也是一项重要措施。  相似文献   
4.
伏喜胜  续景 《润滑油》1998,13(2):30-36
介绍85W/90卡车手动变速箱油的组分和添加剂,提出符合85W/90粘度级别的基础油,讨论影响85W/90卡车手动变速箱油性能的各种因素,给出符合85W/90卡车手动变速箱油规格的油品配方。  相似文献   
5.
乙炔在磁稳定床中的选择性加氢研究   总被引:1,自引:0,他引:1  
 制备了一种磁性Pd/Al2O3催化剂,采用磁稳定床考察了活性组分负载量、反应条件及CO浓度对乙炔加氢反应性能的影响。结果表明,当反应温度80℃、反应压力1.5MPa、空速9000h-1、磁场强度(H)25kA/m时,乙炔转化率为100%,乙烯选择性可达81%,具有优良的乙炔加氢活性和乙烯选择性,优于相同反应条件下的进口催化剂;250h稳定性实验结果表明,磁性Pd/Al2O3催化剂具有良好的初活性和乙烯选择性,催化剂性能稳定。  相似文献   
6.
This paper presents an inelastic element for the analysis of beams on foundations. The element is derived from a two-field mixed formulation with independent approximation of forces and displacements. The state determination algorithm for the implementation of the element in a general purpose nonlinear finite element analysis program is presented and its stability characteristics are discussed. Numerical studies are performed to compare the model with the classical displacement formulation. The studies confirm the superiority of the proposed model in describing the inelastic behavior of beams on foundations.  相似文献   
7.
Business, not technology leaders should manage the change of Information Technology (IT) from a self-contained business support unit of the sixties to a distributed strategic business function of the nineties. Top management should recognize that a good business plan can only be developed and executed through the partnership between the business unit managers and the managers of the financial, the personnel, and the IT resource units. The technical problems associated with the management of IT may again be the easier part of the total management challenge.  相似文献   
8.
Decoupling the constitutive equations from the balance and constraint equations allows for reformulating a conventional forward problem into two reverse problems. The first reverse problem is the reverse of a simulation problem, where the process model is solved in terms of the constitutive (synthesis/design) variables instead of the process variables, thus providing the synthesis/design targets. The second reverse problem (reverse property prediction) solves the constitutive equations to identify unit operations, operating conditions and/or products by matching the synthesis/design targets. Visualization of the problem is achieved by employing recently developed property clustering techniques, which allows a high-dimensional problem to be visualized in two or three dimensions. The clusters by definition satisfy intra-stream and inter-stream conservation through linear “mixing” rules, which allows for the development of consistent additive rules along with their ternary representation.  相似文献   
9.
 In this paper, a new approach for powder cold compaction simulations is presented. A density-dependent plastic model within the framework of finite strain multiplicative hyperelastoplasticity is used to describe the highly nonlinear material behaviour; the Coulomb dry friction model is used to capture friction effects at die-powder contact; and an Arbitrary Lagrangian–Eulerian (ALE) formulation is used to avoid the (usual) excessive distortion of Lagrangian meshes caused by large mass fluxes. Several representative examples, involving structured and unstructured meshes are simulated. The results obtained agree with the experimental data and other numerical results reported in the literature. It is shown that, contrary to other Lagrangian and adaptive h-remeshing approaches recently reported for this type of problems, the present approach verifies the mass conservation principle with very low relative errors (less than 1% in all ALE examples and exactly in the pure Lagrangian examples). Moreover, thanks to the use of an ALE formulation and in contrast with other simulations, the presented density distributions do not present spurious oscillations. Received: 20 March 2002 / Accepted: 15 October 2002 The partial financial support of the Ministerio de Ciencia y Tecnología (grant number DPI 2001-2204) is gratefully acknowledged.  相似文献   
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