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   1342篇
  免费   1篇
  国内免费   1篇
电工技术   2篇
化学工业   5篇
金属工艺   1篇
矿业工程   1篇
能源动力   1篇
轻工业   2篇
水利工程   6篇
石油天然气   1篇
无线电   2篇
一般工业技术   5篇
冶金工业   1313篇
自动化技术   5篇
  2014年   2篇
  2013年   3篇
  2011年   1篇
  2008年   3篇
  2007年   4篇
  2006年   3篇
  2004年   1篇
  2003年   2篇
  2002年   1篇
  2000年   1篇
  1999年   45篇
  1998年   364篇
  1997年   204篇
  1996年   144篇
  1995年   76篇
  1994年   70篇
  1993年   76篇
  1992年   11篇
  1991年   17篇
  1990年   19篇
  1989年   23篇
  1988年   23篇
  1987年   32篇
  1986年   18篇
  1985年   14篇
  1984年   1篇
  1983年   1篇
  1982年   11篇
  1981年   10篇
  1980年   22篇
  1979年   2篇
  1978年   7篇
  1977年   25篇
  1976年   102篇
  1975年   3篇
  1972年   1篇
  1955年   2篇
排序方式: 共有1344条查询结果,搜索用时 11 毫秒
1.
2.
3.
Pulmonary angiograms and pulmonary lung perfusion scans on 162 patients with pulmonary embolism were comparatively analyzed. Among the expert angiographic panel members who independently evaluated the studies there was consistent agreement on the diagnosis, size of the emboli, and severity. Consistency of agreement among the expert pulmonary lung perfusion scan panelists was considerably less. These data demonstrate that, in addition to the lack of specificity of the lung perfusion scan for the diagnosis of pulmonary thromboemboli, there is a considerable problem of interpretation in this patient population.  相似文献   
4.
A total of 98 colposcopically directed biopsies were obtained from the vagina, cervix, and cervicovaginal ridge (hood) of 80 young women believed to have had intrauterine exposure to stilbestrol (DES). Specific investigation of the patient's medical records corroborated the history of maternal stilbestrol administration in 36 patients (45%), while in the remainder the drug history was regarded as presumptive since medical records were unavailable for review. The findings did not differ significantly in those biopsies taken from patients with confirmed or presumptive drug histories. Histologic evidence of vaginal adenosis was detected in vaginal biopsies from 43 patients. In 30 cases (70%) benign Müllerian-type glandular epithelium was in the superficial vaginal wall, residing on the mucosal surface and/or in the lamina propria. The glandular epithelium predominantly was of endocervical type, but in six instances it resembled endometrial or fallopian tubal epithelium. The glands were accompanied by varying degrees of squamous metaplasia in 22 cases. When extensive the metaplasia produced transformation zones similar to those seen in the normal cervix. Vaginal biopsies of adenosis from the other 13 patients (30%) revealed squamous metaplasia without demonstrable glands due to complete transformation of all antecedent glandular epithelium by squamous metaplasia. Our studies indicate that squamous metaplasia is a component of major importance in the natural history of adenosis and that the concept of adenosis should be broadened to include those examples comprised exclusively of metaplastic epithelium. In such examples metaplasia is identified by the immaturity and poor glycogenation of the squamous cells and their accompanying squamous pegs which often contain residual gland openings or squamous "eddies." Similar findings were present in biopsies of seven cervicovaginal ridges and in cervical biopsies from 37 patients, except for the absence of endometrial or tubal type glands in the latter site. Although no adenocarcinomas were detected, six patients had squamous dysplasia of the vagina and/or cervix. In no case were premalignant or dysplastic changes of glandular cells found. Our findings support the thesis that stilbestrol-associated adenosis represents anomalous embryologic localization of the original squamocolumnar junction in the vagina rather than in the cervix. It is closely related to so-called cervical "erosions." The development of squamous metaplasia accounts for modifications in the clinical and histologic appearances by producing transformation zones which then may be subject to the same oncogenic stimuli for squamous neoplasia as are their counterparts in the cervix.  相似文献   
5.
The complexes 1,10-phenanthrolineethylenediamineplatinum(II) and 2,2'-bipyridineethylenediamineplatinum(II) have a planar, aromatic ligand system that facilitates intercalation, as shown by their ability to unwind closed circular duplex DNA. Nonbonded steric interactions can rotate the pryidine ligands out of the coordination plane in bis(pyridine)ethylenediamineplatinum(II), thus preventing intercalation. Fiber x-ray diffraction patterns of the two metallointeracalators indicate that the binding is governed by the neighbor exclusion principle.  相似文献   
6.
7.
The body's equilibrium is possible thanks to the integration of skeletal structure, vertebrae, ligaments and muscles to form one functional unity. The forces which determine posture are composed of two complementary systems, the ligamentary and the muscular systems, which together determine a dynamic act of balance. The ligaments operate mainly against the visco-hydraulic pressure of the nucleus pulposus and bind the vertebral bodies together, whereas the muscles exhibit an antigravity function and support spinal stability. A mathematical model based on a mixed theory of directed and oriented curves is proposed. Through this model it is possible to develop an exact theory governing the deformation of the ligamentous spine. This theory should be universal in the sense that it can be used to supply the spine in any of its environments.  相似文献   
8.
Progesterone and oestrone alone or in combination were administered to sows during early gestation. A dose of 25 mg progesterone and 12-5 mug oestrone injected together for 10,5 or 2 consecutive days during the implantation interval caused increased litter size at term.  相似文献   
9.
Hyperchannel interfaces are designed to interface computer mainframes and peripheral equipment to a high speed bus to form a local network. Each interface executes a distributed control contention access algorithm operation revolves about fixed priorities assigned to the individual interfaces. The access algorithm is extended to provide for message-assigned priorities, to provide better bus access rights for higher classes of messages at the expense of degraded access rights for the lower classes of messages. The extension requires little additional new hardware but instead employs a replication in each interface of existing hardware.The original hyperchannel interface access mechanism is explained. The algorithm extension is described and two models are developed to assess its effect on message transmission access rights, and via these models the viability of the extended algorithm can be demonstrated quantitatively.  相似文献   
10.
The goal of this research was to identify patients' preferences for physician inquiry into various aspects of health status and to examine whether the preconsultation availability of health status data (collected from the SF-36 Health Status Questionnaire) influenced the physician's conduct during the consultation. Results from 58 prenatal patient visits yielded the following findings. First, patients expressed strong preferences for physicians to ask about the patient's perceptions of health in general and about physical dimensions of health status such as pain, vitality, and role limitations due to physical functioning. Patients also were more satisfied when doctors were perceived as having asked about these issues. Second, patients varied considerably in their preferences for physician inquiries into psychosocial issues such as social functioning, mental health, and role limitations due to emotional problems. Approximately half the patients wanted these matters discussed, whereas the remainder either did not care or preferred that doctors not ask about these topics. Third, the preconsultation availability of health status information had little effect on the degree to which physicians asked about the patient's health-related quality of life. Clinical implications are discussed.  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