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   4029篇
  免费   242篇
  国内免费   16篇
电工技术   51篇
综合类   14篇
化学工业   787篇
金属工艺   76篇
机械仪表   171篇
建筑科学   142篇
矿业工程   1篇
能源动力   130篇
轻工业   286篇
水利工程   27篇
石油天然气   7篇
武器工业   2篇
无线电   724篇
一般工业技术   699篇
冶金工业   514篇
原子能技术   19篇
自动化技术   637篇
  2024年   8篇
  2023年   35篇
  2022年   56篇
  2021年   106篇
  2020年   75篇
  2019年   99篇
  2018年   114篇
  2017年   105篇
  2016年   115篇
  2015年   102篇
  2014年   146篇
  2013年   254篇
  2012年   175篇
  2011年   222篇
  2010年   187篇
  2009年   203篇
  2008年   198篇
  2007年   212篇
  2006年   166篇
  2005年   144篇
  2004年   136篇
  2003年   125篇
  2002年   114篇
  2001年   97篇
  2000年   86篇
  1999年   90篇
  1998年   176篇
  1997年   129篇
  1996年   95篇
  1995年   62篇
  1994年   62篇
  1993年   52篇
  1992年   28篇
  1991年   20篇
  1990年   26篇
  1989年   36篇
  1988年   29篇
  1987年   24篇
  1986年   34篇
  1985年   28篇
  1984年   19篇
  1983年   10篇
  1982年   8篇
  1981年   12篇
  1980年   9篇
  1979年   4篇
  1978年   8篇
  1977年   13篇
  1976年   12篇
  1973年   5篇
排序方式: 共有4287条查询结果,搜索用时 0 毫秒
271.
Although thoracoscopic sympathectomy or sympathicotomy is the best treatment for hyperhidrosis palmaris, a new approach of clipping only without transection of T2-sympathetic trunk is just as effective. Aside from the guaranteed cure of hyperhidrosis, this new method has fewer complications and has the advantage of recovery of the sympathetic tone in the hands if the procedure is reversed by the removal of the clips. Between March 18 and September 30 of 1996, 326 patients (190 female and 136 male with a mean age of 20.5 years) underwent thoracoscopic T2-sympathetic block by clipping to treat hyperhidrosis. Good results and few complications were noted during follow up six months to one year postoperatively. Five of the 326 patients, all female, had the operation reversed because of intolerable compensatory sweating. Three recovered from the compensatory sweating within two months and had less palmar sweating than before their sympathetic block; the fourth achieved relief of compensatory sweating after nine months, and the fifth reported no improvement.  相似文献   
272.
Carcinoma of the large bowel is the second leading cause of cancer mortality in Singapore. Although the great majority of patients are discovered at a stage where resection with curative intent is possible, almost half of the patients afflicted will die of it. The combination of 5-fluorouracil + levamisole used in patients with curatively resected high risk Dukes B2 and all Dukes' C colon cancers has been shown to reduce cancer recurrence rate and improve overall survival. Since 1990 adjuvant chemotherapy has been recommended for this group of patients. This report describes patients treated in Singapore, their toxicities and their outcome. A total of 341 patients were treated between 1990 and 1996. Treatment compliance was 71.8%. Toxicity was moderate with mainly grade 1-2 nausea and vomiting, diarrhoea, stomatitis, alopecia, and neutropenia. There was 1 treatment-related death. Median recurrence-free interval was 81 months and median survival was not reached at 90 months. This regimen is tolerable. Until further randomised reports comparing 5-fluorouracil + levamisole to other combinations are available, this combination chemotherapy is recommended to patients after surgical resection of the high risk Dukes' B2 and Dukes' C colon cancer to reduce cancer recurrence and improve overall survival.  相似文献   
273.
274.
275.
PURPOSE: Present radiobiological studies for different cell lines in vitro demonstrate the equivalence and efficacy of continuous low-dose-rate brachytherapy (LDR-BT) and pulsed dose rate brachytherapy (PDR-BT) when using small and frequent dose pulses. The aim of this study was to examine monolayer fibroblast cultures in vitro to examine the biological effects of different pulse doses and dose rates under clinically conditions. MATERIAL AND METHODS: B14 cells, Hy B14 FAF 28, peritoneal fibroblasts, were cultured in multi-well plates and exposed to a PDR radiation source at a distance of 9 mm. The following PDR-schemes were compared: dose per pulse: 1 Gy, 2.5 Gy and 5 Gy to a total dose of 5 Gy/5 h (overall time), 10 Gy/10 h, 20 Gy/20 h and 30 Gy/30 h. The pulse duration for the examination of dose rate effects was 20 min, 30 min or 52 min corresponding by dye pulse dose rate of 300 cGy/h, 200 cGy/h or 115 cGy/h. Treatment endpoints were cell measured by dye exclusion test and clonogenic cell survival. RESULTS: Cell survival decreased for pulse doses of 5 Gy compared to 2.5 Gy or 1 Gy per pulse (mean dose rate 200 to 300 cGy/h). No differences were observed with dose rates during irradiation of 300 cGy/h, 200 cGy/h or 115 cGy/h (20 Gy/1 Gy). CONCLUSION: Radiobiological effects of PDR-RT are dependent on the dose per pulse, with differences in biological effects only with a dose per pulse of more than 2.5 Gy, considering the described in-vitro conditions. More examinations with a more pronounced difference in dose rate will be continued for evaluation of dose rate effects.  相似文献   
276.
An increasing number of hepatic resections are being performed as potentially curative surgery for malignant liver neoplasms. Hepatectomy and subsequent liver regeneration produce a local environment that enhances growth of microscopic residual tumor. To determine if pretreatment with murine interferon gamma (IFN-gamma) can protect against such enhanced tumor growth, Buffalo rats were randomized to receive a 3-day treatment of IFN-gamma (50,000 U/qD intraperitoneally) or saline. Groups then underwent intrasplenic injection of 10(6) Morris hepatoma cells, followed 1 hour later by sham (control) or partial hepatectomy (PH) of 70%. PH significantly enhanced tumor growth within the liver (control, 8 +/- 3 nodules per liver; PH, 73 +/- 12 nodules per liver; P < .001). This enhancement was attenuated by prior administration of IFN-gamma IFN-gamma/PH, 16 +/- 3; P < .001 vs. PH). Growth factor release and liver regeneration were not affected significantly by pretreatment with IFN-gamma. The effect of IFN-gamma on tumor growth is associated with a significant enhancement of Kupffer cell (KC)-mediated tumoricidal activity (percentage of specific lysis, 55 +/- 10% control, 78 +/- 11% IFN-gamma, P < .01) but not lymphocyte-mediated tumoricidal activity. Because microscopic residual disease may be present after hepatectomies for cancer, IFN-gamma may be useful agent in retarding growth of residual tumors.  相似文献   
277.
Driven by the need for a readily available, non-immunological tissue that possesses many of the characteristics of normal human skin, tissue-engineered skin has been developed. For over a decade, laboratory grown or processed skin has been under investigation and, in some cases, available as an alternative to autologous grafts. Apligraf, derived from neonatal foreskin and bovine type I collagen, is the first bi-layered living skin equivalent approved in the US and other countries for use in venous ulcers. Apligraf is effective both in the treatment of refractory venous ulcers and for acute wounds such as surgical excision sites and split thickness donor sites. Apligraf is safe and is not clinically rejected. Its ultimate fate is not known, so it may well work to aid healing in a variety of ways including graft 'take' and as a stimulus for healing.  相似文献   
278.
All of 16 infants with neonatal meningitis treated during a 30-month period were found to have accompanying ventriculitis at the time of the initial ventricular puncture. Fifteen of these infants were caused by gramm-negative organisms. All infants received antibiotics systemically and intraventricularly via an implanted ventriculostomy reservoir or by direct ventricular injection. Antibiotic concentrations within the ventricular fluid were monitored during chemotherapy; the complications encountered during treatment are discussed. Fifteen infants survived the infection; of these, seven infants were normal at follow-up examinations. In our experience intraventricular chemotherapy as an adjunct to systemic administration of antibiotics has greatly reduced the mortality rate in neonatal meningitis.  相似文献   
279.
The two-channel system previously reported has been implemented in hardware using system parameters appropriate to consumer television. The basic system divides the spectrum into lowand high-frequency spatial components. The lows are coarsely sampled and finely quantized and the highs finely sampled and coarsely quantized using a companded, randomized quantizer. The purpose of this experiment was to demonstrate the potential of the system for low-cost practical application, to study the effect of the character of the randomizing noise, and to ascertain that there were no deleterious effects due to interlace, motion, or input noise. Theoretical noise calculations were qualitatively confirmed.  相似文献   
280.
The dynamic-mechanical and thermal scanning behaviour of a series of specially synthesized linear segmented polyurethanes is presented. These materials possess a well defined segment molecular weight and molecular weight distribution and no possibility of intermolecular hydrogen bonding. The dynamic-mechanical transitions observed are assigned to specific molecular motions and the effect of segment size and molecular weight distribution is described. The results are explained in terms of hard segment domain perfection. Differential scanning calorimetry (d.s.c.) curves of annealed samples indicate that domain morphology may be affected by thermal treatment. A comparison of dynamic mechanical and d.s.c. results to hydrogen-bonded polyurethanes is made.  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