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   3240篇
  免费   1篇
化学工业   21篇
金属工艺   4篇
建筑科学   4篇
矿业工程   2篇
能源动力   2篇
轻工业   7篇
水利工程   5篇
无线电   2篇
一般工业技术   9篇
冶金工业   3168篇
原子能技术   9篇
自动化技术   8篇
  2022年   3篇
  2021年   1篇
  2020年   2篇
  2018年   1篇
  2015年   2篇
  2013年   4篇
  2012年   2篇
  2011年   3篇
  2010年   3篇
  2009年   1篇
  2008年   2篇
  2006年   4篇
  2005年   2篇
  2004年   4篇
  2003年   4篇
  2001年   1篇
  2000年   1篇
  1999年   70篇
  1998年   923篇
  1997年   540篇
  1996年   392篇
  1995年   236篇
  1994年   162篇
  1993年   183篇
  1992年   20篇
  1991年   33篇
  1990年   27篇
  1989年   29篇
  1988年   24篇
  1987年   19篇
  1986年   18篇
  1985年   21篇
  1984年   1篇
  1983年   5篇
  1982年   20篇
  1981年   25篇
  1980年   35篇
  1979年   3篇
  1978年   10篇
  1977年   132篇
  1976年   259篇
  1975年   9篇
  1973年   2篇
  1965年   1篇
  1964年   1篇
  1954年   1篇
排序方式: 共有3241条查询结果,搜索用时 15 毫秒
1.
2.
3.
This report analyzes the intracorporal lengths of 236 consecutive organically impotent men who underwent insertion of a penile prosthesis. The average right or left intracorporal length in this series was 20.9 cm, with a standard deviation of 2.2 cm. Intracorporal length ranged from 14-27 cm. This data may be used as reference ranges for penile prosthesis manufacturers, and for Urologists who implant prostheses or perform penile lengthening procedures.  相似文献   
4.
Two cases of female patients operated fo the tumors of the stomach are presented. Result of histologic examination was rather surprising in both cases--leiomyoma.  相似文献   
5.
In the review there analyzed the results of ground-based studies of rotation effects (at a gravity value near 1 g) on the animals, the experimental findings to determine a minimum effective value of artificial gravity as well as the data of biosatellite experiments. The major trends of animal studies in the artificial gravity area is presented.  相似文献   
6.
7.
The proteolytic activity produced by a Bacillus subtilis isolated from a hot spring was investigated. Maximum protease production was obtained after 38 h of fermentation. Effects of various carbon and nitrogen sources indicate the requirement of starch and bacteriological peptone to be the best inducers for maximum protease production. Requirement for phosphorus was very evident, and the protease was secreted over a wide range of pH 5-11. The partially purified enzyme was stable at 60 degrees C for 30 min. Calcium ions were effective in stabilizing the enzyme, especially at higher temperature. The enzyme was extremely salt tolerant and retained 100% activity in 5M NaCl over 96 h. The molecular weight of the purified enzymes as determined by SDS-PAGE was 28,000. The enzyme was completely inactivated by PMSF, but little affected by urea, sodium dodecyl sulfate, and sodium tripoly phosphate.  相似文献   
8.
Magnetic resonance (MR) images of skeletal muscle tears can clearly delineate the severity of muscle injury. Although MR imaging is seldom necessary in patients with acute muscle trauma, it can be helpful in deciding on clinical management. The two major MR findings in acute muscle tears are deformity of the muscle and the presence of abnormal signal reflecting hemorrhage and edema. In acute tears, methemoglobin within the extravascular blood causes high-signal areas on both T1- and T2-weighted images. With partial tears, the blood may dissect in a distinctive linear pattern along the muscle bundles and fibers. As healing begins, the muscle signal diminishes, first on the T1-weighted images and then on the T2-weighted images. When there is residual abnormal signal on images obtained more than several months after the injury, it is presumed to represent hemorrhage from recurrent tears. In patients with a questionable history of a remote injury, the clinical presentation may be that of persistent pain or a soft tissue mass. In these cases MR imaging may identify the cause of the pain and can exclude a neoplasm by proving that the mass is a hypertrophied or retracted muscle. Thus, MR imaging has a limited, but occasionally important role in selected patients with skeletal muscle tears.  相似文献   
9.
Prenatal exposure to diazepam and other benzodiazepines (BDZ) has been found to result in a marked reduction of T-lymphocyte proliferation during postnatal development of rats. In search for pathogenic changes underlying this effect, we investigated the mitogen lipopolysaccharide (LPS) and concanavalin A (ConA) stimulated release of tumour necrosis factor (TNF)-alpha by mixed splenocytes of male offspring from Long Evans rats treated with 1.25 mg/kg per day diazepam from gestational day 14 to 20. In response to LPS, TNF-alpha release was found to be significantly lower in mixed splenocytes of two- and four-week-old treated than in control offspring. However, at eight weeks of age, prenatally diazepam-treated animals showed a significantly higher LPS-induced TNF-alpha release than control rats. Since monocytes/macrophages represent a major source of TNF-alpha, additional experiments were performed on purified spleen macrophages and lymphocytes stimulated with LPS. TNF-alpha release was only detectable in supernatants of adherent spleen macrophages and not in supernatants of lymphocytes. Thus, our data indicate that a disturbance in TNF-alpha release from macrophages is involved in the deficient immune response of prenatally diazepam-exposed rats.  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