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   1507篇
  免费   21篇
  国内免费   12篇
电工技术   3篇
综合类   6篇
化学工业   48篇
金属工艺   11篇
机械仪表   11篇
建筑科学   15篇
矿业工程   4篇
能源动力   6篇
轻工业   21篇
水利工程   2篇
石油天然气   9篇
无线电   31篇
一般工业技术   75篇
冶金工业   1229篇
原子能技术   7篇
自动化技术   62篇
  2022年   5篇
  2021年   3篇
  2020年   4篇
  2019年   2篇
  2017年   4篇
  2016年   6篇
  2015年   7篇
  2014年   7篇
  2013年   13篇
  2012年   21篇
  2011年   21篇
  2010年   21篇
  2009年   14篇
  2008年   14篇
  2007年   18篇
  2006年   9篇
  2005年   22篇
  2004年   19篇
  2003年   14篇
  2002年   20篇
  2001年   15篇
  2000年   7篇
  1999年   41篇
  1998年   346篇
  1997年   222篇
  1996年   140篇
  1995年   73篇
  1994年   81篇
  1993年   81篇
  1992年   13篇
  1991年   14篇
  1990年   15篇
  1989年   10篇
  1988年   22篇
  1987年   13篇
  1986年   13篇
  1985年   10篇
  1984年   3篇
  1983年   6篇
  1982年   5篇
  1981年   18篇
  1980年   21篇
  1978年   4篇
  1977年   31篇
  1976年   75篇
  1975年   2篇
  1974年   2篇
  1973年   2篇
  1968年   3篇
  1955年   4篇
排序方式: 共有1540条查询结果,搜索用时 187 毫秒
831.
Cushing's disease appears as a functionally heterogeneous disease, but criteria that are able to distinguish between different clinical forms remain elusive. We compared two subgroups of patients with proven Cushing's disease according to the size of the pituitary adenoma, evaluated by computed tomography or magnetic resonance imaging. Our series comprised 11 patients with a microadenoma and 10 with a macroadenoma (median volumes (range): 173 (13-270) and 3022 (500-10312) mm3 respectively; P < 0.0001). The clinical presentation was similar in the two groups, but the time elapsed before diagnosis was longer, and visual impairment was less frequent in the patients with a microadenoma (1.5+/-0.8 years and 0%) than in those with a macroadenoma (0.7+/-0.6 years and 40%; P < 0.05). Morning and evening peripheral concentrations of ACTH were greater in patients with macroadenoma (134+/-78 and 130+/-7 ng/l respectively) than in those with microadenoma (52+/-28 and 56+/-19 ng/l, P < 0.05). Hypokalaemia and lymphopenia were also more pronounced in patients with macroadenoma (3.4+/-0.3 mmol/l and 1273+/-401 lymphocytes/mm3) than in those with microadenoma (3.8+/-0.3 mmol/l and 1852+/-668 lymphocytes/mm3 P < 0.05), although morning and evening plasma cortisol concentrations were similar in both groups. In patients with macroadenoma, there was less relative nycthemeral variation of ACTH concentrations (28+/-24%, compared with 62+/-39% in those with microadenoma; P < 0.05), less suppression of plasma cortisol by high doses of dexamethasone (-30+/-14%, compared with -61+/-25%; P < 0.05), and a reduced concentration ratio of mean basal cortisol to ACTH (7+/-3, compared with 12+/-5; P < 0.05). Plasma IGF-I concentration and the TSH peak response to TRH were significantly lower in patients with macroadenoma than in those with microadenoma (0.4+/-0.2 x 10(3) IU/I and 2.3+/-1.8 mIU/I, compared with 1.8+/-0.6 x 10(3) IU/I and 5.2+/-1.6 mUI/l; P < 0.05). Thus, in comparison with microadenomas, corticotroph macroadenomas are characterized by a greater and more autonomous ACTH secretion, inducing more pronounced biological signs of hypercorticism, and are more often accompanied by visual field defects and impairment of other pituitary hormonal secretions.  相似文献   
832.
A case history of a young man with a bowing fracture of the forearm is presented. The fracture was reduced and stabilized using shortened Ender's nails. Both soft tissues and fractures healed uneventfully and complete restoration of function resulted.  相似文献   
833.
STUDY OBJECTIVE: To determine if 450 micrograms/kg (1.5 times the ED95) of rocuronium would result in a comparable onset with a shorter duration of action when compared with 600 micrograms/kg (2 times the ED95). DESIGN: Randomized, single-blind study. SETTING: Teaching hospital. PATIENTS: 85 ASA physical status I and II children ages 2 through 12, undergoing elective surgery with an inhalation induction using halothane. INTERVENTIONS: Group 1 received 600 micrograms/kg rocuronium, and Group 2 received 450 micrograms/kg rocuronium. MEASUREMENTS AND MAIN RESULTS: The two groups were compared using a Student's t-test, with p < 0.05 significant. The time of onset, or time to 95% suppression of neuromuscular twitch with standard errors, was 140 +/- 13 seconds (range 46 to 365 sec) in Group 1 and 148 +/- 13 seconds (range 82 to 345 sec) in Group 2 (NS = not significant). The times to 25% return of twitch from baseline (T25) in Groups 1 and 2 were 28 +/- 1.5 minutes (range 14 to 45 min) and 26 +/- 1.6 minutes (range 10 to 55 min), respectively (NS). The differences between these two doses in onset of, and recovery from, block were not found to be statistically significant. The results, however, excluded 5% of the higher dose group and 31% of the lower dose group who did not achieve 95% suppression of twitch. Time to maximal suppression of neuromuscular blockade, however, was not statistically significant for the 85 patients with a time of 270 +/- 28 seconds (range 91 to 605 sec) with a mean maximal suppression of 98.7% in Group 1 and 313 +/- 25 seconds (range 91 to 899 sec) with a mean maximal suppression of 93.1% in Group 2. CONCLUSION: The two doses of rocuronium did not differ statistically in onset or duration. Rocuronium at 600 micrograms/kg offers more reliability than 450 micrograms/kg in achieving adequate muscle relaxation, and the lower dose may result in a significantly large number of patients who may have inadequate intubating conditions.  相似文献   
834.
835.
To detect extravasation of contrast media during mechanical power injection at dynamic computed tomography, a 5 x 8-cm pliable adhesive patch was applied to the skin over the intravenous cannula and connected to the power injector with a cable to monitor electrical skin impedance. If the rate of change or the slope of impedance over time indicated an extravasation event, the power injector was set into a pause mode. In animal and human studies, monitoring with the device was successful. Extravasation of ionic contrast agents decreased impedance and that of nonionic agents increased impedance.  相似文献   
836.
How to measure pain is a great challenge to those who desire to control adequately such a complex experience. Standardized instruments that take into consideration the patient's own account, have been developed in order to make such a task easier. In this article we carry out a revision of the instruments used mostly for measuring postoperative pain, and we point out some of the advantages and disadvantages. We emphasize the need for specific research focusing on the measurement of surgical pain, taking into consideration the multiple dimensions of a painful experience.  相似文献   
837.
838.
Measurements have been made in the Cooler ring at the Indiana University Cyclotron Facility (IUCF) of the mean lifetime of stored and electron-cooled proton beams in the presence of various target gas species at two ring locations differing in dispersion. A broad range of beam energy Tb, target atomic number Zt and thickness xt was employed. The loss (removal) cross sectionσL per target atom, extracted from the lifetime measurement, exhibits a minimum for small xt which is found to scale with . This behavior is expected because forward Coulomb scattering from target nuclei should be the dominant loss mechanism under the conditions of measurement. A marked increase in σL for larger xt is attributed to emittance growth arising from multiple scattering in competition with the transverse cooling rate. Lattice dispersion at the target increases the contribution to beam heating by electrons in the target atoms and introduces an additional loss mechanism. From the measured σL and beam lifetime, a time cycle may be selected which gives the optimum time-averaged luminosity for a given experiment. Scaling of σL allows prediction of the optimum luminosity over the full operating regime of the cooling ring.  相似文献   
839.
In 1991 the International Council of Nurses (ICN) initiated a long-term project to develop an International Classification for Nursing Practice (ICNP). To identify existing classifications and nomenclatures of nursing, a literature search and survey of national nurses' associations and individuals involved in classification across the world were conducted, in addition to a pilot search for articles describing nursing nomenclatures and classifications in countries other than the US and Canada, the latter having provided most of the examples in the original ICNP proposals. Three sources of literature were examined: international conference proceedings, Med-Line and Exerpta Medica.  相似文献   
840.
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