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   2913篇
  免费   48篇
  国内免费   2篇
电工技术   166篇
综合类   5篇
化学工业   493篇
金属工艺   40篇
机械仪表   89篇
建筑科学   48篇
矿业工程   4篇
能源动力   83篇
轻工业   220篇
水利工程   6篇
石油天然气   7篇
无线电   413篇
一般工业技术   478篇
冶金工业   743篇
原子能技术   50篇
自动化技术   118篇
  2023年   10篇
  2022年   23篇
  2021年   44篇
  2020年   14篇
  2019年   30篇
  2018年   31篇
  2017年   43篇
  2016年   34篇
  2015年   27篇
  2014年   49篇
  2013年   120篇
  2012年   82篇
  2011年   84篇
  2010年   77篇
  2009年   74篇
  2008年   96篇
  2007年   79篇
  2006年   82篇
  2005年   88篇
  2004年   75篇
  2003年   91篇
  2002年   76篇
  2001年   67篇
  2000年   45篇
  1999年   77篇
  1998年   312篇
  1997年   186篇
  1996年   131篇
  1995年   107篇
  1994年   76篇
  1993年   71篇
  1992年   53篇
  1991年   34篇
  1990年   36篇
  1989年   39篇
  1988年   39篇
  1987年   39篇
  1986年   40篇
  1985年   26篇
  1984年   28篇
  1983年   30篇
  1982年   23篇
  1981年   24篇
  1980年   19篇
  1979年   17篇
  1978年   14篇
  1977年   27篇
  1976年   41篇
  1975年   8篇
  1972年   5篇
排序方式: 共有2963条查询结果,搜索用时 31 毫秒
1.
2.
Metallothionein (MT) synthesis induced by the inflammatory cytokines, interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF), was studied in vivo. Administration of recombinant human IL-6 or TNF to rats caused the acute phase responses including rapid decreases in plasma zinc (Zn), and increases in plasma copper (Cu) and ceruloplasmin. Hepatic concentration of MT-I, one of MT isoforms, began to increase within 3 h after the injection of IL-6 or TNF. In IL-6-treated rats, MT-I concentration in liver reached a maximum level at 12 h and decreased with a transient rebound, whereas, in TNF-treated rats, a high level of MT-I lasted for about 48 h. MT-II, the other MT isoform, was induced more than MT-I in liver by both cytokines. MT-I was also induced in lung and heart by TNF, but little by IL-6. The data suggest that IL-6 may be responsible for MT synthesis in liver, whereas TNF may be responsible not only in liver but also in lung and heart. Furthermore plasma concentration of MT did not always reflect the enhanced concentration of MT by TNF and IL-6 in liver, suggesting involvement of many factors influencing plasma MT levels. The interrelation between IL-6 and TNF for MT synthesis has also been discussed.  相似文献   
3.
A new lateral MOS-gated thyristor, called the Base-Current-Controlled Thyristor, is described. This device is designed so that most holes at the on-stage reach the P base through the floating P+ region adjacent to the P base and the on-state MOSFET. At the turn-off stage, the interruption of the hole current to the P base due to switching off the above MOSFET occurs simultaneously with the conventional turn-off operation. The concept of this device is verified experimentally by using the fabricated lateral device with the external MOSFET. This device exhibits a better trade-off relation between the on-state voltage and the turn-off time compared uith the conventional MOS-gated thyristor  相似文献   
4.
Recent advances in gene technology have helped to identify novel proteins and allowed study of their distribution and functions in the mammalian brain. One class of these proteins is that of transporters, which exist in plasma and organellar membranes of neurons and other cells to move substances selectively across membranes. These transporters can be categorized further into subclasses by their structural property, substrate selectivity, and site of action. Some of them have been identified in the hypothalamus, which is the only brain site where a neural signal is converted to a humoral one, namely, a hormone for a target organ. This unique neural mechanism has long attracted attention as the neuroendocrine system, part of which has been extensively studied as the hypothalamic-neurohypophysial system involved in secretion of vasopressin and oxytocin. However, transporters in this system have been less well studied. A morphological examination of novel transporters would give us cues to a better understanding of the neuronal organization and function of the system. In this review, we first summarize recent findings on expression of transporter gene and immunoreactivity in the hypothalamus. In the second part, we explain our observations on two vesicular glutamate (inorganic phosphate) transporters (BNPI and DNPI) in the supraoptic and paraventricular nuclei and neurohypophysis. Further study of these and other transporters will provide a basis on which to reevaluate the organization and function of the hypothalamic-neurohypophysial system.  相似文献   
5.
Gas absorption accompanied by an instantaneous irreversible chemical reaction into laminar falling films of power-law liquids was studied theoretically. The convective-diffusion equations for a solute gas and a liquid-phase reactant were solved numerically and the numerical solution for the reaction factor was obtained as a function of the Graetz number, the concentration ratio, the diffusivity ratio and the power-law index of the liquid.  相似文献   
6.
A transceiver PIC consisting of a DFB-LD, a receiver PD and a Y-shaped branch waveguides is realized by in-plane bandgap energy controlled selective MOVPE. Both active and passive core layers are formed in one step selective growth, and complicated fabrication procedure is no longer required. More than 1 mW fiber coupled power and 7 GHz receiver bandwidth are obtained. The modulation and detection operations at 500 Mb/s are successfully demonstrated.  相似文献   
7.
8.
Three phase partitioning (TPP) uses t-butanol and ammonium sulfate to precipitate enzymes and proteins from aqueous solutions. The method is useful both upstream with crude samples and downstream where a scaleable simple step is needed. About 25 enzymes and proteins have been isolated by various laboratories using TPP-t-butanol. The relation of t-butanol used in TPP, with n-butanol used as an extraction agent from Morton's work, is reviewed. Some t-butanol appears bound to TPP-precipitated proteins which are actually protein-t-butanol coprecipitates. They float above denser aqueous salts because bound t-butanol increases their buoyancy, similar to the behavior of many lipoproteins. On redissolving TPP-precipitated enzymes, total and specific activities usually are regained and sometimes increased. Sulfate ion-in large concentrations-likely exerts itself through its kosmotropic action as in conventional salting out. t-Butanol likewise appears to be a kosmotrope and crowding agent at room temperature or above, whereas C1 and C2 cosolvents (e.g., ethanol) do not so behave except at near or below zero temperatures. However, kosmotropy is not the entire origin of TPP, nor probably of conventional salting out. Electrostatic forces, capacity to force protein conformation tightening and protein hydration shifts, also contribute. Electrostatic forces, and the tendency for salt ions to bind and tighten protein molecule conformation, are indicated by the sharp pH dependency of both conventional salting out and TPP, around pH regions where proteins undergo conformation changes. Sulfate anion is densely-perhaps extraordinarily-hydrated, adding much to its effective size, and therefore it has a tendency to crowd or exclude proteins, when sulfate concentrations are in the 0.5 to 3 M range.  相似文献   
9.
10.
We recorded all-night polysomnograms of four schizophrenic patients with neuroleptic-induced akathisia (NIA) before and during treatment with clonazepam. Also, four non-akathitic schizophrenic patients were recorded all-night polysomnograms as control subjects. Daily treatment with 1.5 to 3 mg clonazepam improved subjective complaints of all the 4 patients with NIA. Three of 4 patients with NIA exhibited periodic limb movements (PLM) on bilateral legs, but none of 4 control subjects showed PLM. Total number of PLM and PLM per hour decreased during clonazepam treatment. Moreover, mean inter-movement intervals of PLM of 3 patients were prolonged on bilateral legs. NIA might change its feature as PLM during night sleep.  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