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   1878篇
  免费   3篇
电工技术   2篇
化学工业   23篇
金属工艺   2篇
机械仪表   3篇
建筑科学   1篇
能源动力   2篇
轻工业   5篇
水利工程   1篇
无线电   19篇
一般工业技术   13篇
冶金工业   1801篇
原子能技术   2篇
自动化技术   7篇
  2021年   2篇
  2020年   2篇
  2019年   2篇
  2018年   2篇
  2016年   2篇
  2014年   1篇
  2013年   1篇
  2012年   1篇
  2011年   4篇
  2010年   1篇
  2007年   10篇
  2006年   4篇
  2005年   7篇
  2004年   3篇
  2003年   3篇
  2002年   2篇
  2001年   2篇
  2000年   7篇
  1999年   57篇
  1998年   601篇
  1997年   301篇
  1996年   205篇
  1995年   86篇
  1994年   84篇
  1993年   105篇
  1992年   12篇
  1991年   30篇
  1990年   24篇
  1989年   26篇
  1988年   21篇
  1987年   28篇
  1986年   23篇
  1985年   27篇
  1984年   2篇
  1983年   5篇
  1982年   7篇
  1981年   9篇
  1980年   18篇
  1979年   2篇
  1978年   6篇
  1977年   41篇
  1976年   91篇
  1975年   5篇
  1974年   1篇
  1973年   1篇
  1972年   2篇
  1970年   1篇
  1962年   1篇
  1955年   1篇
  1928年   2篇
排序方式: 共有1881条查询结果,搜索用时 15 毫秒
991.
992.
Measures that can be taken to reduce exposure to potentially infected body fluids are of particular relevance in obstetric and gynaecological surgery due to high rates of glove puncture and relatively higher prevalence of human immunodeficiency virus seropositivity in the obstetric age group. We describe the use of a simple electronic device that alarms following puncture of surgical gloves or the creation of a fluid bridge between surgeon and patient. Further exposure to potentially infected body fluids is thus prevented. This present study was performed in the context of caesarean section, but the application of the technique to gynaecological procedures is appropriate.  相似文献   
993.
Proper positioning and assessment of abnormalities and complications of the above-mentioned devices have a significant impact on the management of critically ill patients in the intensive care unit (ICU). The timely assessment of new or rapidly evolving findings is critical. Optimal radiographic technique, availability of images to the clinicians, and rapid reporting by the radiologist all serve to maximize the efficacy of bedside chest radiography in the ICU. Sometimes, changes in cardiopulmonary status may only be appreciated on chest radiographs (CXRs). Complications from ventilatory assistance, such as barotrauma, occur frequently and must be detected promptly. The position of monitoring devices, an important component of critical care management, is best checked radiographically. Indications for CXRs and the recommended frequency for repeat follow-up CXRs are based on the existing literature and the consensus of an expert panel formed by the American College of Radiology.  相似文献   
994.
995.
PURPOSE: We determined the need and sequence of retroperitoneal lymph node dissection and thoracotomy in patients with nonseminomatous testicular cancer, and with residual retroperitoneal and pulmonary masses after chemotherapy. MATERIALS AND METHODS: We studied 159 patients undergoing retroperitoneal lymph node dissection and a thoracotomy following cisplatin based induction chemotherapy for metastatic testicular nonseminomatous germ cell tumor. Several well-known predictors for residual histology (necrosis, mature teratoma and cancer) were evaluated. RESULTS: As expected, necrosis was found more often at retroperitoneal lymph node dissection if the primary tumor was negative for teratoma, the residual mass was small or the decrease in size was great. Contrary, neither residual mass size nor the decrease in size was predictive of the histological status of the residual lung lesion. Histological findings in the retroperitoneum and lung were strongly correlated, such that necrosis at retroperitoneal lymph node dissection was associated with an 89% probability of necrosis in the lung. CONCLUSIONS: Retroperitoneal lymph node dissection should be performed before thoracotomy is considered, since the histological status at dissection is a strong predictor of that at thoracotomy.  相似文献   
996.
OBJECTIVE: To investigate the effect of cataract extraction on the results of automated perimetry in persons with glaucomatous visual field loss. SUBJECTS: Subjects from a retrospective study of visual field progression who underwent cataract extraction during follow-up were identified. Subjects came from the glaucoma service of a hospital-based tertiary referral center. METHODS: Subjects had at least 7 Humphrey 24-2 or 30-2 visual fields over 5 years or more, with an abnormal glaucoma hemifield test result on the first 2 examinations. Visual field data were transferred to a microcomputer and comparison of the visual fields immediately before and after cataract extraction was performed. RESULTS: Sixty-five eyes of 50 subjects (mean age, 71.8 years) were included in the analysis. A mean improvement in mean deviation (MD) of 1.68 dB (P<.001), and a mean worsening in corrected pattern SD (CPSD) of 0.54 dB (P=.09) was observed. The mean unweighted change in threshold in the 52 points of program 24-2 was 1.58 dB, corresponding to a 43.9% increase in sensitivity. A significant correlation between improvement in visual acuity and improvement in MD was also found. A mean increase in CPSD of 1.61 dB (P=.005) occurred in subjects with dense scotomas (minimum threshold value < or = 5 dB) and preoperative CPSD of 8 dB or less. CONCLUSIONS: In persons with glaucomatous visual field defects, cataract extraction produces only a modest improvement in MD. After cataract surgery, the CPSD index worsened in many subjects with dense scotomas. This suggests that the development of cataract can mask progressive glaucomatous visual field loss in such persons.  相似文献   
997.
Role of renin-angiotensin system in hypertension induced by cadmium chloride (CdCl2) in rats has been investigated. Intravenous administration of CdCl (1 mg/kg) produced a biphasic response i.e. a transient fall followed by a marked and consistent rise in blood pressure. The peak hypertensive effect was accompanied by raised PRA levels. Pretreatment with captopril (1 mg/kg, i.v.) losartan (1 mg/kg, i.v.) or captopril + losartan attenuated the pressor response to Cd by 62%, 42% and 100% respectively in separate groups. Central administration of Cd (10 micrograms/rat, i.c.v.) showed a biphasic response similar to that observed after i.v. route. However, it was not accompanied by raised PRA levels. Prior treatment with losartan (10 micrograms/rat, i.c.v.) completely abolished the pressor response to Cd (i.c.v.) whereas it was not affected significantly by captopril (10 micrograms/rat, i.c.v.). On the other hand, centrally administered losartan only partially reduced the pressor response to i.v. Cd. The results are discussed in light of a differential involvement of central vs peripheral renin-angiotensin system in the hypertensive effect of Cd.  相似文献   
998.
The effect of NMDA receptor antagonist phencyclidine (PCP) on expression of cyclooxygenase (COX)-2 mRNA in the rat brain was studied. Administration of PCP (12.5, 25 or 50 mg/kg, i.p., 6 h) caused marked induction of COX-2 mRNA and heat shock gene hsp-70 mRNA, a marker of neuronal injury, in the retrosplenial cortex, in a dose-dependent manner. These results suggest that COX-2 may play a role in the neurotoxicity of NMDA receptor antagonists.  相似文献   
999.
Apnoea, bradycardia and hypotension were elicited by right atrial injections of capsaicin in anaesthetized monkeys. At the threshold dose (2.5 +/- 0.3 microgram/kg), tachypnoea was elicited (latency 1.6 +/- 0.2 s) which got replaced by apnoea with higher doses of capsaicin. These responses persisted (1) after cooling the cervical vagi to 6-8 degrees C, and (2) after instilling xylocaine into the pericardial sac. Tachypnoea and apnoea were elicited after bilateral cervical vagotomy also, but only with higher doses and after a longer latency (5.0 +/- 0.3 s). Right atrial injection of capsaicin and insufflation of halothane stimulated vagal pulmonary C-fibre receptors with a latency of 1.7 +/- 0.7 s and 0.2 +/- 0.1 s, respectively. Tachypnoea/apnoea, bradycardia and hypotension were elicited by left atrial injection of capsaicin also (threshold dose: 5.0 +/- 1.2 micrograms/kg). The respiratory responses persisted (1) after instilling xylocaine into the pericardial sac, and (2) after bilateral cervical vagotomy suggesting that they were due to stimulation of non-cardiac receptors with sympathetic afferents. It is concluded that the initial respiratory responses elicited by right atrial injection of capsaicin were due to stimulation of pulmonary C-fibre receptors with vagal afferents.  相似文献   
1000.
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