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   13724篇
  免费   1087篇
  国内免费   39篇
电工技术   213篇
综合类   6篇
化学工业   3196篇
金属工艺   508篇
机械仪表   881篇
建筑科学   259篇
矿业工程   2篇
能源动力   627篇
轻工业   992篇
水利工程   55篇
石油天然气   37篇
无线电   2676篇
一般工业技术   3115篇
冶金工业   848篇
原子能技术   249篇
自动化技术   1186篇
  2024年   10篇
  2023年   157篇
  2022年   238篇
  2021年   416篇
  2020年   346篇
  2019年   344篇
  2018年   439篇
  2017年   516篇
  2016年   544篇
  2015年   424篇
  2014年   639篇
  2013年   930篇
  2012年   945篇
  2011年   1164篇
  2010年   795篇
  2009年   832篇
  2008年   751篇
  2007年   587篇
  2006年   531篇
  2005年   473篇
  2004年   427篇
  2003年   382篇
  2002年   370篇
  2001年   313篇
  2000年   310篇
  1999年   294篇
  1998年   385篇
  1997年   239篇
  1996年   187篇
  1995年   127篇
  1994年   130篇
  1993年   94篇
  1992年   63篇
  1991年   76篇
  1990年   56篇
  1989年   50篇
  1988年   41篇
  1987年   40篇
  1986年   33篇
  1985年   24篇
  1984年   22篇
  1983年   15篇
  1982年   13篇
  1981年   16篇
  1980年   11篇
  1979年   8篇
  1977年   14篇
  1976年   11篇
  1975年   4篇
  1974年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
In this paper, we propose a new robust code division multiple access (CDMA) receiver of which weight vector is obtained by projecting the effective spatio-temporal signature waveform onto the signal subspace of the data covariance matrix. We verified our proposed algorithm by the field measured data obtained with a custom-built wideband CDMA test-bed. It will be shown that the proposed algorithm is robust to the signal mismatch.  相似文献   
72.
The IBF has for some years made use of finite element programmes to solve metal-forming problems. In the course of this investigation, it has become evident that a problem-oriented adaptation of FEM simulation to the problem in hand is beneficial in terms of computation effort. The computation time for the process parameters is optimised in a multi-level simulation. At level 1 (global analysis) integral parameters such as the required force and required work are computed using a coarse FEM mesh. At level 2 (local analysis) an optimised number of elements is used to determine continuum mechanics parameters like stress, strain and temperature. Microscopic phenomena are simulated at level 3 (microscopic analysis), using special micro-material elements and thermodynamic models.  相似文献   
73.
A logic language is suitable for specification if it is equipped with features for data abstraction and modularization. In this paper, an effective mechanism to incorporate function and type into logic programming is presented as the means to embed data abstraction mechanism into logic programming. This incorporation is essentially based on Horn clause logic with equality and a polymorphic type system that is an extension of Mycroft and O’Keefe’s system. This paper also presents an implementation based on Warren Abstract Machine (WAM) and shows the performance, along with a comparison with WAM.  相似文献   
74.
75.
We report three children with hemidystonia in whom anti-cardiolipin (aCL) antibodies were demonstrated. Systemic lupus erythematosus was excluded on the basis of both clinical and serological criteria, and the diagnosis of primary antiphospholipid syndrome (PAPS) was made. In two cases, aCL antibodies could be causally related to a presumed immune-mediated thrombotic event involving the basal ganglia as shown by magnetic resonance imaging (MRI). In the remaining patient the finding of white matter alteration on NMR might be due to cross-reactivity of anti-phospholipid (aPL) antibodies with cerebral phospholipids, resulting in demyelination. We suggest that PAPS must always be considered when isolated or recurrent focal cerebral ischaemia, and particularly hemidystonia, occur in childhood.  相似文献   
76.
77.
In this paper, we propose queueing strategies employing the service interval-based priority (sip) which can provide delay-bounded, and loss-free services, while maximizing bandwidth utilization in the atm network. We also describe a variation of the sip, the residual service interval-based priority (rsip) which can achieve almost full utilization by assigning priorities dynamically on the basis of the residual service interval. We store the realtime cells belonging to different connections in logically separated queues, and for each queue, we set a parameter called service interval, during which only one cell is allowed to be transmitted. The sip server takes and transmits the head-of-line (hol) cell of the queue which has the smallest service interval, while the rsip server selects the queue with the smallest residual service interval. When there is no eligible real-time cell, it transmits non-real-time cell, thus enabling a maximized bandwidth utilization. Employing the above queueing strategies, we analyze the delay characteristics deterministically with the leaky bucket bounded input traffic and then dimension the optimal service interval. In dimensioning the service interval and buffer space of each real-time service queue, we consider burstiness of traffic in conjunction with delay constraints, so that bandwidth utilization can get maximized. In addition, we consider the issues of protection from malicious users, average bandwidth utilization, and coupling between the delay bound and the bandwidth allocation granularity.  相似文献   
78.
The need for frequent injections and monitoring, the possibility of multiple gestations, and the higher cost compared to clomiphene citrate, prevents many clinicians from using human menopausal gonadotrophin (HMG) for ovulation induction. A sequential medication regimen, in which HMG is taken after clomiphene, overcomes these problems. We retrospectively compared per cycle fecundity and birth rates in 119 cycles of clomiphene-HMG, 524 cycles of clomiphene alone, 57 cycles of HMG alone, and 79 cycles of concurrent HMG and clomiphene in patients receiving intra-uterine insemination (IUI), who were free of endometriosis or tubal disease. Per cycle fecundity for clomiphene-HMG was 22% [95% confidence interval (CI) 12-34%], double that of clomiphene alone (11%) (95% CI 8-14%) (P < 0.01), and equal to HMG alone (18%) (95% CI 7-29%) or HMG and clomiphene together (19%) (95% CI 10-28%). The multiple birth rate for clomiphene-HMG (7/21) equalled that for HMG alone (3/12) and HMG and clomiphene together (3/8). The average number of ampoules of HMG required [follicle stimulating hormone (FSH) 75 mIU, luteinizing hormone (LH) 75 mIU] was decreased by 65% from 24.5 +/- 1.0 for HMG or HMG and clomiphene together to 8.6 +/- 0.3 for clomiphene-HMG (P < 0.001). Per cycle fecundity was identical when one, two or three ampoules of HMG per day were administered after clomiphene. We conclude that ovulation induction with sequential clomiphene-HMG results in fecundity double that of clomiphene alone and equal to HMG alone or concurrent with clomiphene, thereby reducing the requirement for HMG.  相似文献   
79.
Artificially layered Bi2Sr2Can–1CunO4+n films were synthesized by sequential sputter deposition of BiO, SrCu0.5O1.5 and CaCuO2 layers. Annealing behavior of these films which were irradiated by Ar ions was studied. Defect assisted improvement of their crystalline perfection is expected which might results in the improvement of the superconducting properties of these films. An artificial film, such as an intergrowth of 2223 and 2234 phases, and superstructure films of (2245)1(2201)1 and (2234)1(2212)1, were irradiated by Ar ions (150 keV, 2–10×1012 ions/cm2) and annealed at 730 °C. An improvement of superconducting transition temperatures were observed.  相似文献   
80.
The on-line sensing of viable cell weight in plant cell culture process is applied to analysis and control of process. The fiber-optic fluorescence sensor was constructed to measure the NADH-dependent fluorescence inNicotiana tabacum plant cell culture and the analysis of fluorescence signal was done to be correlated with the viable cell weight. The structured kinetic model for cell growth was proposed to estimate the theoretical viable cell weight. The dimensional analysis was proposed for the interpretation of fluorescence signal, in which the path length, the inner filter effect and the hydrodynamic conditions were considered as the key factors on fluorescence signal. The dimensional analysis and empirical correlation of fluorescence signal to viable cell weight was applied to the interpretation of the detected fluorescence signal during cultivation. The proposed interpretation of fluorescence signal using dimensional analysis was well correlated with the viable cell weight estimated by the structured kinetic model as well as by empirical correlation.  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