全文获取类型
收费全文 | 43274篇 |
免费 | 882篇 |
国内免费 | 178篇 |
专业分类
电工技术 | 526篇 |
综合类 | 630篇 |
化学工业 | 4493篇 |
金属工艺 | 580篇 |
机械仪表 | 856篇 |
建筑科学 | 823篇 |
矿业工程 | 390篇 |
能源动力 | 395篇 |
轻工业 | 2040篇 |
水利工程 | 609篇 |
石油天然气 | 48篇 |
武器工业 | 4篇 |
无线电 | 1818篇 |
一般工业技术 | 3332篇 |
冶金工业 | 22058篇 |
原子能技术 | 183篇 |
自动化技术 | 5549篇 |
出版年
2024年 | 55篇 |
2023年 | 187篇 |
2022年 | 112篇 |
2021年 | 100篇 |
2018年 | 446篇 |
2017年 | 669篇 |
2016年 | 1042篇 |
2015年 | 773篇 |
2014年 | 412篇 |
2013年 | 403篇 |
2012年 | 2123篇 |
2011年 | 2417篇 |
2010年 | 656篇 |
2009年 | 746篇 |
2008年 | 590篇 |
2007年 | 617篇 |
2006年 | 553篇 |
2005年 | 3334篇 |
2004年 | 2553篇 |
2003年 | 2038篇 |
2002年 | 836篇 |
2001年 | 728篇 |
2000年 | 273篇 |
1999年 | 629篇 |
1998年 | 6328篇 |
1997年 | 3913篇 |
1996年 | 2565篇 |
1995年 | 1491篇 |
1994年 | 1113篇 |
1993年 | 1131篇 |
1992年 | 245篇 |
1991年 | 317篇 |
1990年 | 311篇 |
1989年 | 294篇 |
1988年 | 304篇 |
1987年 | 231篇 |
1986年 | 206篇 |
1985年 | 173篇 |
1984年 | 68篇 |
1983年 | 82篇 |
1982年 | 131篇 |
1981年 | 181篇 |
1980年 | 195篇 |
1979年 | 59篇 |
1978年 | 97篇 |
1977年 | 625篇 |
1976年 | 1354篇 |
1975年 | 102篇 |
1973年 | 46篇 |
1971年 | 49篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
C Held P Hjemdahl N Rehnqvist NH Wallén I Bj?rkander SV Eriksson L Forslund B Wiman 《Canadian Metallurgical Quarterly》1997,95(10):2380-2386
BACKGROUND: Disturbed fibrinolytic function may influence the progression of coronary atherosclerosis and contribute to thrombotic cardiovascular (CV) events. METHODS AND RESULTS: In the Angina Prognosis Study in Stockholm (APSIS), patients with stable angina pectoris were studied prospectively during double-blind treatment with metoprolol or verapamil. Various measures of fibrinolytic function were studied in 631 (of 809) patients. During a median follow-up time of 3.2 years (2132 patient-years), 32 patients suffered a CV death, 21 had a nonfatal myocardial infarction (MI), and 77 underwent revascularization. Plasma levels of tissue plasminogen activator (TPA) activity and antigen (ag), plasminogen activator inhibitor (PAI-1) activity at test, and TPA responses to exercise were determined at baseline and after 1 month's treatment and were related to subsequent fatal and nonfatal CV events. Univariate Cox regression analysis revealed that elevated levels of TPA-ag at rest (P < .05), high PAI-1 activity (P < .05), and low TPA-ag responses to exercise (P < .05) were associated with increased risk of subsequent CV death. After adjustment for baseline risk factors, TPA-ag independently predicted CV death or MI. In addition, PAI-1 activity independently predicted CV death or MI in male patients. Verapamil treatment was associated with a 10% decrease of TPA-ag levels and metoprolol treatment with a 2% increase (P < .001 for treatment difference). CONCLUSIONS: Plasma TPA-ag levels at rest, and among male patients PAI-1 activity as well, independently predict subsequent CV death or MI in patients with stable angina pectoris. 相似文献
63.
A theoretical model is presented by which a true expression of pregnancy rate resulting from stimulated cycles can be calculated. This includes the transfer of both fresh and cryopreserved embryos. It is concluded that the total reproductive potential of a single cycle of stimulation can only be evaluated by including pregnancies arising from all fresh and frozen embryo transfers resulting from that cycle. 相似文献
64.
65.
VV Grigorovski? 《Canadian Metallurgical Quarterly》1997,(9-10):76-79
The tibial diaphysis osteotomy with limited separation of periosteum on the ends of the fragments with subsequent local infection by Staphylococcus aureus culture was conducted. In 90% of observations chronic inflammation was revealed in affected bones while morphological investigation conduction. An acute traumatic disorders of intraosseous blood circulation (the bone infarction) and local staphylococcal infection play the main role in the traumatic osteomyelitis pathogenesis. 相似文献
66.
67.
S Benk? S Drabant G Grézal I Urm?s M Cs?rg? I Klebovich 《Canadian Metallurgical Quarterly》1997,47(8):913-916
A comparative pharmacokinetic study has been performed in 19 healthy male volunteers in a single-dose, randomized, two way cross-over design with two preparations of gemfibrozil (CAS 25812-30-0) capsules each of them containing 300 mg active ingredient. The test preparation was Innogem 300 mg capsule. The plasma concentration of gemfibrozil was determined by a validated HPLC-UV analytical method. The statistical comparison of individual pharmacokinetic parameters (AUC0-16, AUC0-oc Cmax, tmax) of the two capsule preparations was performed by three-way analysis of variance (ANOVA), Wilcoxon's, Westlake's, Schuirmann's and Hanck-Anderson's method as well as by the calculation of confidence intervals on the ratio of test/reference. The relative bioavailability of the test preparation with respect to the reference preparation in terms of the AUC0-oc was 104.06 +/- 21.61%. No statistically significant difference was found between the pharmacokinetic parameters, calculated from plasma concentration-time curves, indicating that the two preparations were bioequivalent. 相似文献
68.
D Popovi? 《Canadian Metallurgical Quarterly》1997,50(11-12):559-563
Tissue and organ transplantation is a very complex interdisciplinary treatment, particularly in regard to unpaired organs, and it carries numerous risks for all participants in such an action. For the purpose of minimizing the risks to the allowed level and the preservation the humanitarian goals in medicine when performing the transplantation, professional and scientific doctrines and the respect of ethical and legal principles should be strictly observed. The paper presents the basic approaches in the estimation of justification, usefulness and certain forms of responsibility in the process of transplantation. Ethical and legal postulates which support transplantation to prevent deviation, deprivation or delinquency have also been reviewed. 相似文献
69.
70.
NE Joseph C Fiocchi AD Levine 《Canadian Metallurgical Quarterly》1997,122(4):809-14; discussion 814-6
BACKGROUND: Crohn's disease (CD) and ulcerative colitis (UC) are chronic inflammatory diseases, and their pathogenesis is attributed, in part, to alterations of the mucosal immune system. This study was designed to define the possible contribution of epithelial cells to the activation of lamina propria T lymphocytes (LPTs) in CD and UC. METHODS: LPTs isolated from CD, UC, and control surgical specimens were cocultured with freshly isolated allogeneic or autologous epithelial cells or epithelial cell lines. Resulting T-cell proliferation was evaluated by tritiated thymidine incorporation on day 5. RESULTS: When intestinal epithelial cells were used to stimulate mucosal T-cell proliferation, CD and UC LPTs were less responsive than control LPTs (p < 0.05 and p < 0.03, respectively). This difference between inflamed and control T cells was consistently observed by using a variety of different intestinal epithelial cell types. CONCLUSIONS: CD and UC mucosal T cells are hyporesponsive to activation by intestinal epithelial cells when compared with control LPTs. Elucidating the mechanism underlying the differential activation of CD and UC LPTs may help to better understand the immunopathogenesis of these conditions. 相似文献