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   30820篇
  免费   2820篇
  国内免费   1551篇
电工技术   2133篇
技术理论   2篇
综合类   2099篇
化学工业   4922篇
金属工艺   1613篇
机械仪表   2038篇
建筑科学   3079篇
矿业工程   818篇
能源动力   846篇
轻工业   2437篇
水利工程   551篇
石油天然气   1395篇
武器工业   233篇
无线电   3846篇
一般工业技术   3565篇
冶金工业   1196篇
原子能技术   413篇
自动化技术   4005篇
  2024年   115篇
  2023年   542篇
  2022年   998篇
  2021年   1438篇
  2020年   1021篇
  2019年   847篇
  2018年   911篇
  2017年   1013篇
  2016年   943篇
  2015年   1174篇
  2014年   1558篇
  2013年   1807篇
  2012年   2030篇
  2011年   2206篇
  2010年   2068篇
  2009年   1905篇
  2008年   1758篇
  2007年   1647篇
  2006年   1590篇
  2005年   1354篇
  2004年   949篇
  2003年   885篇
  2002年   867篇
  2001年   777篇
  2000年   712篇
  1999年   733篇
  1998年   531篇
  1997年   514篇
  1996年   492篇
  1995年   388篇
  1994年   325篇
  1993年   247篇
  1992年   193篇
  1991年   119篇
  1990年   89篇
  1989年   88篇
  1988年   67篇
  1987年   43篇
  1986年   27篇
  1985年   24篇
  1984年   17篇
  1983年   12篇
  1982年   13篇
  1981年   9篇
  1980年   12篇
  1979年   13篇
  1977年   4篇
  1962年   43篇
  1961年   39篇
  1960年   16篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
A model of a human neural knowledge processing system is presented that suggests the following. First, an entity in the outside world lends to be locally encoded in neural networks so that the conceptual information structure is mirrored in its physical implementation. Second, the knowledge of problem solving is implemented in a quite implicit way in the internal structure of the neural network (a functional group of associated hidden neurons and their connections to entity neurons) not in individual neurons or connections. Third, the knowledge system is organized and implemented in a modular fashion in neural networks according to the local specialization of problem solving where a module of neural network implements an inter-related group of knowledge such as a schema, and different modules have similar processing mechanisms, but differ in their input and output patterns. A neural network module can be tuned just as a schema structure can be adapted for changing environments. Three experiments were conducted to try to validate the suggested cognitive engineering based knowledge structure in neural networks through computer simulation. The experiments, which were based on a task of modulo arithmetic, provided some insights into the plausibility of the suggested model of a neural knowledge processing system.  相似文献   
92.
汪太龙  杨敏  叶明 《石油沥青》2007,21(1):33-36
超稠油的密度大、粘度高、轻油收率低、酸值高,沥青组成分布不合理,生产沥青困难。探索合适的超稠油生产沥青的加工工艺,不但可以解决超稠油加工困难问题,而且增加了生产道路沥青产品的原料资源。试验及生产证明,采用调和、预处理-蒸馏等工艺加工超稠油能够生产出合格的重交通道路石油沥青产品。  相似文献   
93.
The thermal decompositions of mechanically activated and nonactivated galenas were studied by thermogravimetry analysis (TGA) at the heating rate of 10 K min−1 in argon. Results indicate that the initial temperature of thermal decomposition (abbreviated as T di) in the TGA curves for different galenas decreases gradually with increased grinding time. The specific granulometric surface area (S G), the structural disorder, and the content of elemental sulfur of mechanically activated galenas were analyzed by an X-ray diffraction (XRD) laser particle-size analyzer, XRD analysis, and the gravimetric method, respectively, which shows that the specific granulometric surface area of mechanically activated galenas remains almost constant after a certain grinding time, but the lattice distortions (ε) rise, the crystallite sizes (D) decrease, and the elemental sulfur contents of mechanically activated galenas increase with increased grinding time. The results imply that the decrease of the initial temperature of thermal decomposition in the TGA curves for mechanically activated galenas is mainly caused by the increase of lattice distortions, and the formation of new dangling bonds resulted from the production of elemental sulfur of mechanically activated galenas with increased grinding time. Finally, the differences in the thermal-decomposition reactivity between nonactivated and mechanically activated galenas were also discussed.  相似文献   
94.
Fred Y. Ye 《Scientometrics》2007,71(3):407-413
There exists a quantitative relationship, which can be expressed as G=kF(lgP)N, where G is per capita GDP, F gross expenditure on R&D as % of GDP, P patent applications, N Internet users per 10,000 inhabitants, and k a constant ranging from 0.4 to 1.2 in most countries. The mechanism of the relationship is explained in the paper.  相似文献   
95.
We report on the optimized characteristics of a small-size bactericidal lamp pumped by transverse RF (f=1.76 MHz) discharge, operating on a system of the molecular emission bands of chlorine in a wavelength range of 195–310 nm. The spectral characteristics of the plasma emission were measured and the intensity of chlorine emission bands were studied as functions of the total pressure and partial composition of a helium-chlorine mixture. Oscillograms of the pumping current and output radiation intensity were measured and the total output radiation power was determined. It is established that the lamp radiates predominantly in a bactericidal wavelength interval on an electron-vibrational transition at 200 nm in Cl2** molecules. The optimum partial pressures of helium and chlorine are 100–300 and 90–120 Pa, respectively. The maximum output power of UV emission from the side cylindrical surface of the lamp reached 10 W. The lamp can be used in photochemistry, ecology, genetics, and medicine.  相似文献   
96.
本文在研究人类设计技能模型的基础上,建立暖通空调广义设计过程模式,提出暖通空调广义设计过程及其CAD系统的信息模型,并以此为基础建立了暖通空调广义CAD系统的框架。  相似文献   
97.
In China,RFID technology has been applied to some extents,and also has a huge market and development margin. During this progress,the government will help to build up the basic information construction,then to make the basic informa- tion resource open,at the same time to avoid the policy management over-commercialized,and push RFID technology applica- tion forward and speed up its development.  相似文献   
98.
根据Requisition的词义和询价、招标、订购文件的意义,建议将不能准确表达意思的中文译词“请购”改成“询购”。  相似文献   
99.
Parity space approach and H2 approach are two important fault detection approaches. This paper studies the relationship between these two approaches, which reveals frequency domain characteristics of the optimal solution of the parity space approach on the one side and provides a numerical solution of the H2-optimal design of residual generators on the other side.  相似文献   
100.
Volatile anaesthetics have historically been considered to act in a nonspecific manner on the central nervous system. More recent studies, however, have revealed that the receptors for inhibitory neurotransmitters such as gamma-aminobutyric acid (GABA) and glycine are sensitive to clinically relevant concentrations of inhaled anaesthetics. The function of GABA(A) and glycine receptors is enhanced by a number of anaesthetics and alcohols, whereas activity of the related GABA rho1 receptor is reduced. We have used this difference in pharmacology to investigate the molecular basis for modulation of these receptors by anaesthetics and alcohols. By using chimaeric receptor constructs, we have identified a region of 45 amino-acid residues that is both necessary and sufficient for the enhancement of receptor function. Within this region, two specific amino-acid residues in transmembrane domains 2 and 3 are critical for allosteric modulation of both GABA(A) and glycine receptors by alcohols and two volatile anaesthetics. These observations support the idea that anaesthetics exert a specific effect on these ion-channel proteins, and allow for the future testing of specific hypotheses of the action of anaesthetics.  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