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   2451篇
  免费   144篇
  国内免费   22篇
电工技术   33篇
综合类   66篇
化学工业   531篇
金属工艺   78篇
机械仪表   87篇
建筑科学   105篇
矿业工程   25篇
能源动力   64篇
轻工业   338篇
水利工程   19篇
石油天然气   49篇
武器工业   1篇
无线电   132篇
一般工业技术   390篇
冶金工业   274篇
原子能技术   32篇
自动化技术   393篇
  2024年   4篇
  2023年   24篇
  2022年   85篇
  2021年   113篇
  2020年   59篇
  2019年   63篇
  2018年   91篇
  2017年   85篇
  2016年   98篇
  2015年   71篇
  2014年   94篇
  2013年   182篇
  2012年   154篇
  2011年   163篇
  2010年   137篇
  2009年   110篇
  2008年   111篇
  2007年   90篇
  2006年   75篇
  2005年   79篇
  2004年   57篇
  2003年   63篇
  2002年   60篇
  2001年   24篇
  2000年   41篇
  1999年   56篇
  1998年   72篇
  1997年   67篇
  1996年   35篇
  1995年   41篇
  1994年   33篇
  1993年   22篇
  1992年   10篇
  1991年   10篇
  1990年   5篇
  1988年   6篇
  1987年   5篇
  1986年   6篇
  1985年   7篇
  1984年   9篇
  1983年   13篇
  1982年   10篇
  1981年   4篇
  1980年   8篇
  1979年   5篇
  1978年   10篇
  1977年   10篇
  1976年   14篇
  1974年   5篇
  1972年   6篇
排序方式: 共有2617条查询结果,搜索用时 0 毫秒
1.
Physically based simulation of human hair is a well studied and well known problem. But the “pure” physically based representation of hair (and other animation elements) is not the only concern of the animators, who want to “control” the creation and animation phases of the content. This paper describes a sketch-based tool, with which a user can both create hair models with different styling parameters and produce animations of these created hair models using physically and key frame-based techniques. The model creation and animation production tasks are all performed with direct manipulation techniques in real-time.  相似文献   
2.
The GC/MS and NMR analysis of the reaction products of naphthalene with 1-bromohexane were reported. The products obtained were suggested to have six isomers of linear hexylnaphthalene and the structure of each isomer was determined by GC/MS and NMR spectra. For the first time, the unique chemical shift data were obtained. The content of each isomer calculated by 1H NMR and 13C NMR spectra was consistent with that by GC/MS spectra, which confirmed the accuracy of NMR data.  相似文献   
3.
4.
5.
Polyarteritis nodosa is a rare disorder and a form of systemic vasculitis. A 48 year-old female was admitted to the hospital because menorrhagia and pelvic pain in February 1993. The patient underwent exploratory laparotomy resulting in a total hysterectomy and bilateral salpingo-oophorectomy for myoma of uterus and a right adnexal cystic mass. Histopathologic examination revealed left ovarian periarteritis nodosa. Further investigation and 9 months follow-up failed to show any systemic involvement. To our knowledge the isolated ovarian polyarteritis nodosa is the first case in the literature.  相似文献   
6.
The paper presents a computational approach and numerical data which facilitate the use of the smeared-tip method for cohesive fracture in large enough structures. In the recently developed K-version of the smeared tip method, the large-size asymptotic profile of the stress intensity factor density along a cohesive crack is considered as a material characteristic, which is uniquely related to the softening stress-displacement law of the cohesive crack. After reviewing the K-version, an accurate and efficient numerical algorithm for the computation of this asymptotic profile is presented. The algorithm is based on solving a singular Abel's integral equation. The profiles corresponding to various typical softening stress-displacement laws of the cohesive crack model are computed, tabulated and plotted. The profiles for a certain range of other typical softening laws can be approximately obtained by interpolation from the tables. Knowing the profile, one can obtain with the smeared-tip method an analytical expression for the large-size solution to fracture problems, including the first two asymptotic terms of the size effect law. Consequently, numerical solutions of the integral equations of the cohesive crack model as well as finite element simulations of the cohesive crack are made superfluous. However, when the fracture process zone is attached to a notch or to the body surface and the cohesive zone ends with a stress jump, the solution is expected to be accurate only for large-enough structures.  相似文献   
7.
8.
9.
The concentration of heat-shock proteins of 70 kD (HSP70) in heart tissue has been shown to increase during transient myocardial ischaemia and to persist during several hours of reperfusion. In this study the relationship between the local myocardial HSP70 concentration and blood flow was addressed for control physiological conditions and acute myocardial ischaemia. A specific aim of this study was to address the question of whether low flow areas under control physiological conditions have undergone a transient ischaemia during the preceding hours and thus may be in a state of hibernation or stunning. In 12 anaesthetized, open-chest beagle dogs (6 control and 6 with 60-min coronary artery stenosis) heart rate, mean aortic pressure, mean arterial partial pressure of O2 and partial pressure of CO2 averaged 85+/-16 beats/min, 94+/-14 mmHg, 102+/-17 mmHg and 39+/-6 mmHg, respectively. Regional HSP70 and myocardial blood flow (RMBF) were measured using an HSP70-enzyme-linked immunosorbent assay and the tracer microsphere technique, respectively, in samples of 250 mg wet mass. In the control group the mean RMBF was 1.06+/-0.59 ml.min-1.g-1 and the local HSP70 concentration was 7.08+/-1.03 microg/mg cytosolic protein. Myocardial HSP70 showed a blood flow-independent regional biological heterogeneity, equivalent to a coefficient of variation of 0.31. Local HSP70 concentrations did not differ (P>0.05) between control low and high flow samples, 6.16+/-1.0 vs 6.08+/-0.75 microg/mg cytosolic protein, respectively. However, after 60 min of coronary artery occlusion the local HSP70 concentration increased from 7.08 +/-1.03 to 13.43+/-3.19 microg/mg cytosolic protein (P<0. 001). There was a significant inverse relationship between the percent reduction of local blood flow and HSP70 (r=-0.56, P<0.001). From these results it is concluded that: (1) low flow samples under control physiological conditions are unlikely to be in a state of hibernation or stunning since their HSP70 concentration is normal and (2) the increase in the local HSP70 concentration during myocardial ischaemia reflects the degree of impairment of O2 delivery.  相似文献   
10.
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