全文获取类型
收费全文 | 3220篇 |
免费 | 69篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 37篇 |
化学工业 | 513篇 |
金属工艺 | 34篇 |
机械仪表 | 66篇 |
建筑科学 | 183篇 |
矿业工程 | 13篇 |
能源动力 | 94篇 |
轻工业 | 319篇 |
水利工程 | 21篇 |
石油天然气 | 19篇 |
无线电 | 241篇 |
一般工业技术 | 440篇 |
冶金工业 | 995篇 |
原子能技术 | 20篇 |
自动化技术 | 296篇 |
出版年
2022年 | 35篇 |
2021年 | 44篇 |
2020年 | 24篇 |
2019年 | 34篇 |
2018年 | 32篇 |
2017年 | 40篇 |
2016年 | 48篇 |
2015年 | 38篇 |
2014年 | 71篇 |
2013年 | 140篇 |
2012年 | 100篇 |
2011年 | 117篇 |
2010年 | 83篇 |
2009年 | 96篇 |
2008年 | 110篇 |
2007年 | 127篇 |
2006年 | 109篇 |
2005年 | 107篇 |
2004年 | 85篇 |
2003年 | 96篇 |
2002年 | 73篇 |
2001年 | 74篇 |
2000年 | 52篇 |
1999年 | 63篇 |
1998年 | 204篇 |
1997年 | 147篇 |
1996年 | 88篇 |
1995年 | 72篇 |
1994年 | 75篇 |
1993年 | 77篇 |
1992年 | 48篇 |
1991年 | 35篇 |
1990年 | 37篇 |
1989年 | 43篇 |
1988年 | 44篇 |
1987年 | 37篇 |
1986年 | 42篇 |
1985年 | 38篇 |
1984年 | 22篇 |
1983年 | 43篇 |
1982年 | 44篇 |
1981年 | 36篇 |
1980年 | 28篇 |
1979年 | 25篇 |
1978年 | 26篇 |
1977年 | 29篇 |
1976年 | 59篇 |
1975年 | 27篇 |
1974年 | 25篇 |
1973年 | 19篇 |
排序方式: 共有3291条查询结果,搜索用时 0 毫秒
1.
The smooth muscle of the normal bladder wall must have some specific properties. It must be very compliant and able to reorganise itself during filling and emptying to accommodate the change in volume without generating any intravesical pressure, but whilst maintaining the normal shape of the bladder. It must be capable of synchronous activation to generate intravesical pressure at any length to allow voiding. The cells achieve this through spontaneous electrical activity combined with poor electrical coupling between cells, and a dense excitatory innervation. In the diseased state, alterations of the smooth muscle may lead to failure to store or failure to empty properly. The diseased states discussed are bladder instability and diabetic neuropathy. Bladder instability is characterised urodynamically by uninhibitable rises in pressure during filling, and is seen idiopathically and in association with bladder outflow obstruction and neuropathy. In diabetic neuropathy, many of the smooth muscle changes are a consequence of diuresis, but there is evidence for alterations in the sensory arm of the micturition reflex. In the unstable bladder, additional alterations of the smooth muscle are seen, which are probably caused by the patchy denervation that occurs. The causes of this denervation are not fully established. Nonsurgical treatment of instability is not yet satisfactory; neuromodulation has some promise, but is expensive, and the mechanisms poorly understood. Pharmacological treatment is largely through muscarinic receptor blockade. Drugs to reduce the excitability of the smooth muscle are being sought, since they may represent a better pharmacological option. 相似文献
2.
Surveyed 70 practicing attorneys and 150 law students to determine the extent to which they felt it was their responsibility to inform clients they referred for psychological testing about the testing process and about the validity scales on tests. Results showed that almost 50% of the attorneys and over 33% of the students believe that clients referred for testing always or usually should be informed of validity scales on tests. These results suggest that many test takers, particularly in forensic settings, may have information about validity scales that facilitates their giving biased responses without detection. Psychologists doing forensic evaluations should be alert to this possibility and should consider using more than one approach to detect response distortions. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
3.
In this paper we shall review the main appraches to nonmonotonic reasoning which we classify from the perspective of their underlying logical settings as classical, intuitionistic, three-valued/partial models, and conditional. We shall be placing special emphasis on some of the prominent approaches. We shall also give hints on potential future directions and emphasize that more theoretical work is still needed before a move to application is made. 相似文献
4.
Brough Turner 《卫星与网络》2008,(5):66-66
在车站等车的时候你或许有几分钟的时间需要打发。这时,你拿起手机输入一串紧缩码,只几秒钟,便看到一段你想看的电影片花或是最近朋友们谈论的YouTube上的某个3min的视频剪辑。 相似文献
5.
在基于项目的组织中实现创新 在本节我们将探讨如何在项目环境中进行创新.首先我们来了解一下人们进行改变,进而实现创新的规律;然后我们介绍两种截然不同的管理创新的方法,即常用的线性推理方法和有机推进法;最后,我们对它们的优缺点做一个比较,看看它们各自适用于什么情况. 相似文献
6.
JA McCrohon WA Walters JT Robinson RJ McCredie L Turner MR Adams DJ Handelsman DS Celermajer 《Canadian Metallurgical Quarterly》1997,29(7):1432-1436
OBJECTIVES: We sought to assess whether high dose estrogen treatment is associated with enhanced arterial reactivity in genetic males. BACKGROUND: Although estrogens have been shown to enhance arterial reactivity in women, and are thereby thought to confer cardiovascular benefit, the vascular effects of long-term estrogen therapy in genetic males is unknown. METHODS: We studied the arterial physiology of 30 genetic males--15 male to female transsexuals receiving long-term high dose estrogen therapy and 15 healthy male control subjects matched for age, smoking history and vessel size. Using external vascular ultrasound, brachial artery diameter was measured at rest, after flow increase (causing endothelium-dependent dilation [EDD]) and after nitroglycerin (GTN), an endothelium-independent dilator. Blood pressure, cholesterol and testosterone levels were also measured in each subject. RESULTS: Total testosterone and free testosterone index levels were lower in the transsexuals compared with the control subjects (p < 0.001). In contrast, EDD was significantly higher in the transsexuals than in the control males (mean [+/-SD] 7.1 +/- 3.1% vs. 3.2 +/- 2.8%, p = 0.001), as was the GTN response (21.2 +/- 6.7% vs. 14.6 +/- 3.3%, p = 0.002). Total and high density lipoprotein cholesterol, blood pressure levels and baseline vessel size were similar in the two groups. On multivariate analysis, enhanced EDD was associated independently with estrogen therapy (p = 0.02) and with low total cholesterol (p = 0.04). An enhanced GTN response was also significantly associated with estrogen therapy (p = 0.03). CONCLUSIONS: Long-term treatment with high dose estrogens is associated with enhanced arterial reactivity in genetic males, which may be due to the effects of estrogen excess or androgen deprivation, or both. 相似文献
7.
8.
Since its introduction into the analytical laboratory, CE has had to prove that it was capable of generating results comparable to HPLC or GC techniques in the six areas (specificity, precision, accuracy, linearity, ruggedness, and range) typically required of validated methods intended for submission to governmental agencies. This paper will showcase the development and validation of two analytical methods: one for specific identification of HEPES (N-[2-hydroxyethyl]piperazine-N'-[2-ethane sulfonic acid]) and the other to quantitate millimolar concentrations of tris (tris[hydroxymethyl]aminomethane) in high electrolyte solutions. Utilizing neutral markers and internal standards, results for HEPES demonstrate that migration time reproducibility, expressed as %RSD of 2% or less on a variety of capillaries, is obtainable. Additionally, for quantitation of tris, the values obtained for accuracy (%relative mean bias), precision (%RSD), and linearity (r2) over multiple days and capillaries meet the rigorous standards we require of HPLC or GC methods. 相似文献
9.
We have measured cardiovascular changes associated with insufflation of carbon dioxide and the reverse Trendelenburg position during laparoscopic cholecystectomy, using transoesophageal echocardiography in 13 healthy patients. End-tidal carbon dioxide values increased after insufflation of carbon dioxide, with values significantly (P < 0.05) increased after lateral tilt positioning. Creation of a pneumoperitoneum was associated with increases (P < 0.05) in left ventricular end-systolic wall stress, concomitant with increases (P < 0.01) in peak airway pressure and systemic arterial pressure. In addition, left ventricular end-diastolic area decreased (P < 0.05) after reverse Trendelenburg positioning. Left ventricular ejection fraction was maintained throughout the study. 相似文献
10.
Professional software engineering continues to face problems that involve large-scale (complex) software systems development. Such efforts typically require team collaboration over months, possibly years. Once implemented, the system must be maintained for sometimes decades. This development and maintenance life cycle requires not only technical knowledge and skills in software development, but also the knowledge and skills associated with software process. We believe the traditional computer science curriculum fails to consider this spectrum of needs. We also believe, however, that software engineering must use certain elements of the core knowledge and skills taught by computer scientists as its foundation. We describe lessons learned from the 10-year collaboration between Monmouth University and the Software Engineering Center of the US Army's CECOM (Communications Electronics Command). The center recruits electrical engineering and computer science graduates from academic institutions in the geographic regions surrounding its various installations to be part of its intern program; Monmouth University, in turn, incorporates the demands of the intern program in its Master of Science in software engineering curriculum 相似文献