全文获取类型
收费全文 | 6965篇 |
免费 | 104篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 41篇 |
综合类 | 5篇 |
化学工业 | 544篇 |
金属工艺 | 57篇 |
机械仪表 | 55篇 |
建筑科学 | 137篇 |
矿业工程 | 22篇 |
能源动力 | 62篇 |
轻工业 | 332篇 |
水利工程 | 26篇 |
石油天然气 | 8篇 |
无线电 | 234篇 |
一般工业技术 | 603篇 |
冶金工业 | 4595篇 |
原子能技术 | 34篇 |
自动化技术 | 315篇 |
出版年
2022年 | 20篇 |
2021年 | 43篇 |
2020年 | 24篇 |
2019年 | 22篇 |
2018年 | 50篇 |
2017年 | 31篇 |
2016年 | 53篇 |
2015年 | 41篇 |
2014年 | 51篇 |
2013年 | 195篇 |
2012年 | 98篇 |
2011年 | 139篇 |
2010年 | 105篇 |
2009年 | 110篇 |
2008年 | 147篇 |
2007年 | 147篇 |
2006年 | 108篇 |
2005年 | 107篇 |
2004年 | 79篇 |
2003年 | 100篇 |
2002年 | 83篇 |
2001年 | 71篇 |
2000年 | 83篇 |
1999年 | 180篇 |
1998年 | 1158篇 |
1997年 | 721篇 |
1996年 | 468篇 |
1995年 | 268篇 |
1994年 | 263篇 |
1993年 | 287篇 |
1992年 | 66篇 |
1991年 | 77篇 |
1990年 | 104篇 |
1989年 | 108篇 |
1988年 | 93篇 |
1987年 | 114篇 |
1986年 | 93篇 |
1985年 | 106篇 |
1984年 | 56篇 |
1983年 | 49篇 |
1982年 | 53篇 |
1981年 | 56篇 |
1980年 | 74篇 |
1979年 | 28篇 |
1978年 | 54篇 |
1977年 | 166篇 |
1976年 | 295篇 |
1975年 | 38篇 |
1974年 | 23篇 |
1969年 | 19篇 |
排序方式: 共有7070条查询结果,搜索用时 15 毫秒
991.
992.
993.
DM Adams JS Sholl EI Haney TL Russell RK Silver 《Canadian Metallurgical Quarterly》1998,178(4):843-847
A recent review of the relevant literature indicates that different approaches to the exploration of nurses' clinical reasoning are being adopted in North America, Australia and the United Kingdom. These differing approaches, which tend to cluster chronologically and which include decision analysis, information processing and skills acquisition theory and their limitations will be outlined; it will be argued that it is through their conflation that nurses' collective understanding of nurses' clinical reasoning is deepened. The author is attempting to develop an international network of nurse scholars interested in clinical reasoning with the aim of achieving this. The purposes of this network will be to facilitate international collaboration to expedite both the growth of knowledge related to nurses' clinical reasoning and the development of programs of international comparative research related to it. The setting up of this network and progress to date is described. 相似文献
994.
The advantages of the laparoscopic mode of access for hysterectomy include shorter recovery time and less pain and scarring. The laparoscopic component of the hysterectomy is usually combined with a vaginal component. The relative proportions of the procedure, performed laparoscopically and vaginally, vary considerably between surgeons. The main problem associated with the laparoscopic approach is to ensure adequate hemostasis while avoiding damage to the urinary tract. A variety of differing techniques have been developed in attempts to ensure the safe and efficient removal of the uterus laparoscopically. 相似文献
995.
A simple and powerful method for the determination of labeling sites on oligodeoxynucleotides (ODN) has been developed. The method is based on the finding that nuclease P1 (NP1) digestions of label-containing ODNs produce site-specific products: 5'-labeled ODNs produce label-nucleotide (L-N); 3'-labeled ODN produces phosphorylated label (pL); and a label in between the ODN termini produces pL-N. Mass spectrometry spectra of these products from the digestion mixture can be easily utilized for structural verification of labeled ODNs such as DNA probes. We also developed a method for the determination of the labeling sites of ODNs with unknown label structures. In this method, NP1 digestion products generate site-specific fragmentation patterns upon collision-induced dissociation. These patterns can be easily recognized and used for the identification of labeling sites of ODNs with unknown label structures. When an ODN is internally labeled, phosphodiesterase digestion may be used to determine the exact labeling site (sequence location). It was demonstrated that these methods can be applied for ODNs with single or multiple labels, and for ODNs with the same or different labels within an ODN. 相似文献
996.
GS Treiman PA Schneider PF Lawrence WC Pevec RL Bush L Ichikawa 《Canadian Metallurgical Quarterly》1998,28(1):104-12; discussion 113-4
OBJECTIVE: This study was undertaken to determine the results and complications of stents placed for initially unsuccessful or complicated iliac percutaneous transluminal angioplasty (PTA), the effect of location (external iliac or common iliac) on outcome, and the influence of superficial femoral artery patency on benefit. DESIGN: From 1992 through 1997, 350 patients underwent iliac artery PTA at the authors' institutions. Of this group, 88 patients (88 arteries) had one or more stents placed after PTA (140 stents in total) for residual stenosis or pressure gradient (63 patients), iliac dissection (12 patients), long-segment occlusion (10 patients), or recurrent stenosis (3 patients). Thirty patients required the placement of more than one stent. The indications for PTA in these 88 patients were claudication (48 patients) and limb-threatening ischemia (40 patients). Forty-seven patients had stents placed in the common iliac, 29 patients had stents placed in the external iliac, and 12 patients had stents placed in both. Seventy-one arteries (81%) were stenotic, and 17 (19%) were occluded before PTA. Sixty-six arteries were treated by interventional radiologists, 15 by a vascular surgeon, and 7 jointly. MAIN OUTCOME MEASURE: Criteria for success included (1) increase of at least one clinical category of chronic limb ischemia from baseline or satisfactory wound healing, (2) maintenance of an ankle/brachial index increase of more than 0.10 above the preprocedure index, and (3) residual angiographic stenosis less than 25% and, for patients with pressure gradient measurements, a residual gradient less than 10 mm Hg. RESULTS: Stent placement was accomplished in all 88 patients with 16 (18%) major complications. Mean follow-up was 17 months (range, 3 to 48 months). By life-table analysis, success was 75% at 1 year, 62% at 2 years, and 57% at 3 years. No cardiovascular risk factor or independent variable was statistically significant in predicting success. There was no difference in success rates for common iliac or external iliac lesions. Superficial femoral artery patency did not correlate with outcome. CONCLUSIONS: Although stents can eliminate residual lesions and arterial dissection, these patients are likely to require adjuvant or subsequent procedures to attain clinical success. By controlling the PTA complication and treating the emergent problem, stents may allow for subsequent elective intervention. 相似文献
997.
998.
RL Summitt TG Stovall GH Lipscomb SA Washburn FW Ling 《Canadian Metallurgical Quarterly》1994,171(6):1480-4; discussion 1484-7
OBJECTIVE: This study examines our continuing experience in performing vaginal hysterectomies and laparoscopy-assisted vaginal hysterectomies with an outpatient protocol. The purpose was to review factors associated with discharge and hospitalization. STUDY DESIGN: Surgical records from all women entering our previously reported outpatient hysterectomy protocol were reviewed. Demographics, surgical indications, intraoperative data, and postoperative data were studied, and their associations with patient discharge and hospitalization were determined. Specific attention was directed to complications. RESULTS: The study group consisted of 133 women. Twelve women (9.0%) were not discharged from the hospital and 5 (3.8%) required readmission. Surgical indications, the type of hysterectomy, and the requirement for pain medication revealed no association with hospitalization. The occurrence of an intraoperative complication (p < 0.000), the need for transfusion (p = 0.043), and postoperative antiemetics (p = 0.013) were statistically associated with hospitalization. In addition, low hematocrit values and elevated temperatures on the first and second postoperative days were associated with hospitalization. CONCLUSION: Long-term experience with outpatient hysterectomy reveals a hospitalization rate of 12.8%. Complications, blood loss, elevated temperatures, and postoperative nausea are the major determinants of patient discharge and hospitalization. Readmission rates continue to remain low. 相似文献
999.
TT Postolache TA Hardin FS Myers EH Turner LY Yi RL Barnett JR Matthews NE Rosenthal 《Canadian Metallurgical Quarterly》1998,155(11):1614-1616
OBJECTIVE: The authors sought to compare the degree of mood improvement after light treatment with mood improvement in the subsequent summer in patients with seasonal affective disorder. METHOD: By using the Seasonal Affective Disorder Version of the Hamilton Depression Rating Scale, the authors rated 15 patients with seasonal affective disorder on three occasions: during winter when the patients were depressed, during winter following 2 weeks of light therapy, and during the following summer. They compared the three conditions by using Friedman's analysis of variance and the Wilcoxon signed ranks test. RESULTS: The patients' scores on the depression scale were significantly higher after 2 weeks of light therapy in winter than during the following summer. CONCLUSIONS: Light treatment for 2 weeks in winter is only partially effective when compared to summer. Further studies will be necessary to assess if summer's light or other factors are the main contributors to this difference. 相似文献
1000.