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   4514篇
  免费   1篇
综合类   1篇
化学工业   15篇
建筑科学   4篇
轻工业   3篇
无线电   3篇
一般工业技术   4篇
冶金工业   4473篇
自动化技术   12篇
  2019年   1篇
  2014年   6篇
  2013年   2篇
  2012年   3篇
  2011年   1篇
  2009年   2篇
  2006年   3篇
  2004年   1篇
  2003年   9篇
  2000年   2篇
  1999年   127篇
  1998年   1388篇
  1997年   848篇
  1996年   490篇
  1995年   268篇
  1994年   250篇
  1993年   278篇
  1992年   35篇
  1991年   49篇
  1990年   73篇
  1989年   61篇
  1988年   68篇
  1987年   63篇
  1986年   45篇
  1985年   35篇
  1984年   1篇
  1983年   8篇
  1982年   12篇
  1981年   29篇
  1980年   44篇
  1979年   2篇
  1978年   7篇
  1977年   92篇
  1976年   203篇
  1975年   5篇
  1964年   1篇
  1955年   3篇
排序方式: 共有4515条查询结果,搜索用时 31 毫秒
161.
162.
163.
Changes in the emission intensities of ultraweak biophoton emission during the cell proliferation of human carcinoma cell culture (TE9 cell line) were detected using a highly sensitive and low noise measurement apparatus coupled with a flow culture system. In the sampling period of 93 h, the biophoton emission intensity from the culture followed a similar course as that of the growth curve. Spectral analysis of the biophoton emission from the cell culture demonstrated a significant peak at around 530 nm. Our results suggest that the emission intensity mainly depends on the cell population and that this noninvasive technique has a potential role in cancer diagnosis.  相似文献   
164.
Human females have been reported to be uniquely sensitive to the deleterious effects of ethanol, thus it is important to study the characteristics of and mechanisms underlying alcohol consumption that may be specific to females. Models of ethanol self-administration in female rats that take into consideration the estrous cycle have the potential to provide important information concerning these characteristics and mechanisms. The purpose of this study was to explore the effect of the cycle on ethanol self-administration using a limited access operant paradigm. Female Wistar rats were trained to lever press for 10% ethanol versus water using a saccharin fading procedure. Responses were examined across the four phases of the estrous cycle. No effects of estrous cycle phase were observed when these rats were allowed to cycle freely. Subsequently, estrous phase effects were investigated in females whose cycles had been synchronized. Under this condition, an effect of estrous phase was present, with lower ethanol intake observed in estrus (and in some cases proestrus). Synchronized rats all showed at least one very clear 4-day estrous cycle, whereas free-running rats' cycles ranged from 3 to 5 days. Thus, it is more likely that synchronized rats were tested in the identical portion of each phase, when hormone levels were less variable. These results suggest that ethanol may be more reinforcing during diestrus than proestrus and estrus in female rats.  相似文献   
165.
A 54 year-old man had symptoms of acute right hemispheric cerebral ischemia. He was initially considered for participation in a trial of early thrombolysis in stroke, but an innominate artery embolus was found with no apparent arterial source. The embolus was removed by means of a combined brachial and carotid bifurcation approach to protect the cerebral vasculature from embolic fragmentation during extraction. Further investigation revealed deep venous thrombosis, evidence of pulmonary emboli, and a patent foramen ovale, supporting a diagnosis of paradoxic embolus. Additional treatment included anticoagulation and placement of an inferior vena caval filter. The unusual condition of paradoxic embolus is reviewed, and the management of this patient is discussed.  相似文献   
166.
This paper presents a full reconstruction process of magnetic resonance images. The first step is to bring the acquired data from the frequency domain, using a Fast Fourier Transform algorithm. A Tomographic Image Interpolation is then used to transform a sequence of tomographic slices in an isotropic volume data set, a process also called 3D Reconstruction. This work describes an automatic method whose interpolation stage is based on a previous matching stage using Delaunay Triangulation. The reconstruction approach uses an extrapolation procedure that permits appropriate treatment of the boundaries of the object under analysis.  相似文献   
167.
168.
Agonistic and antagonistic properties of LPS and partial structures in the induction of cytokines are reviewed. Studies on structure-activity relationships of LPS and lipid A with human mononuclear cells reveal that S- and notably R-form LPS are very potent cytokine inducers. Synthetic E. coli lipid A is somewhat less active, whereas synthetic S. minnesota-type lipid A is significantly less active. Pentaacylated forms of lipid A are less potent than hexaacylated forms, and tetraacylated synthetic precursor Ia and bisacylated disaccharides and monosaccharides are completely inactive, indicating that a structure-dependent hierarchy of LPS and lipid A partial structures determines the monokine-inducing capacity in human mononuclear cells. Precursor Ia is a potent LPS antagonist. The mechanism of its inhibitory activity is shown to be due to competitive binding to cellular binding sites (receptors). Proinflammatory and antiinflammatory cytokines, receptor antagonists, and soluble cytokine receptors influence the cytokine-inducing activity of LPS, suggesting a complex regulatory network.  相似文献   
169.
An integrated process for the design, plasma spray processing, laboratory evaluation, rig test verification and hardware evaluation of thermal barrier coatings for diesel engine applications is described. This method relies heavily on a thorough understanding of the process at each step. The properties and residual stress condition of the coating were modified to meet design criteria through control of the various plasma spray processing parameters. Coating uniformity and repeatability issues were also addressed by adjusting the process conditions to properly account for the specific geometric features of the substrate. These steps are described in detail with particular emphasis on the effect of the process on the coating characteristics. It is shown that a thick thermal barrier can be produced which is durable under accelerated engine test conditions through proper choice of material and processing parameters.  相似文献   
170.
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