全文获取类型
收费全文 | 739075篇 |
免费 | 19024篇 |
国内免费 | 7025篇 |
专业分类
电工技术 | 19212篇 |
技术理论 | 9篇 |
综合类 | 9185篇 |
化学工业 | 116060篇 |
金属工艺 | 35263篇 |
机械仪表 | 29074篇 |
建筑科学 | 22739篇 |
矿业工程 | 8080篇 |
能源动力 | 18247篇 |
轻工业 | 55552篇 |
水利工程 | 10191篇 |
石油天然气 | 22514篇 |
武器工业 | 1083篇 |
无线电 | 78777篇 |
一般工业技术 | 145217篇 |
冶金工业 | 105440篇 |
原子能技术 | 17508篇 |
自动化技术 | 70973篇 |
出版年
2022年 | 7333篇 |
2021年 | 11100篇 |
2020年 | 8187篇 |
2019年 | 8682篇 |
2018年 | 17516篇 |
2017年 | 18163篇 |
2016年 | 16368篇 |
2015年 | 11283篇 |
2014年 | 16632篇 |
2013年 | 33735篇 |
2012年 | 25589篇 |
2011年 | 34421篇 |
2010年 | 28853篇 |
2009年 | 29705篇 |
2008年 | 30138篇 |
2007年 | 30524篇 |
2006年 | 22900篇 |
2005年 | 22155篇 |
2004年 | 19325篇 |
2003年 | 18910篇 |
2002年 | 17919篇 |
2001年 | 16697篇 |
2000年 | 15619篇 |
1999年 | 14947篇 |
1998年 | 29889篇 |
1997年 | 21856篇 |
1996年 | 17272篇 |
1995年 | 13494篇 |
1994年 | 12063篇 |
1993年 | 11561篇 |
1992年 | 9192篇 |
1991年 | 8818篇 |
1990年 | 8600篇 |
1989年 | 8324篇 |
1988年 | 7965篇 |
1987年 | 7170篇 |
1986年 | 6879篇 |
1985年 | 7701篇 |
1984年 | 6991篇 |
1983年 | 6694篇 |
1982年 | 6067篇 |
1981年 | 6187篇 |
1980年 | 5901篇 |
1979年 | 6045篇 |
1978年 | 5993篇 |
1977年 | 6478篇 |
1976年 | 8015篇 |
1975年 | 5426篇 |
1974年 | 5202篇 |
1973年 | 5291篇 |
排序方式: 共有10000条查询结果,搜索用时 822 毫秒
971.
M Fern? PO Bendahl A Brisfors K Byman M Ekeberg L Ferraud K Grankvist B Hjalmers A Nilsson G Sellberg L Skoog O St?l I Wingmo 《Canadian Metallurgical Quarterly》1997,36(8):793-798
Estrogen and progesterone receptor analysis results were compared within and between six laboratories in Sweden using frozen breast cancer cytosol samples, and the same technique (enzyme immunoassay, Abbott Laboratories). The concordance in receptor status (positive vs. negative) was excellent (98.4% (571/580)). The discordant results were attributable to values near cut-off (n = 4) or outliers (n = 5), the latter probably being due to analytical errors. One laboratory reported significantly higher ER concentrations than the others; thus caution should be observed when comparing absolute values from different centers. For PgR there were similar differences between the laboratories. However, the intra- and inter-laboratory differences were small compared with the overall variability in ER and PgR content between different samples in a large database. The range of the median intra-laboratory coefficient of variation was 11-23% for ER and 12-19% for PgR, indicating that there is room for improvement in the quality of assay performance. 相似文献
972.
973.
Improved atrial function in bicaval versus standard orthotopic techniques in cardiac transplantation
A Beniaminovitz MT Savoia M Oz M Galantowicz MR Di Tullio S Homma D Mancini 《Canadian Metallurgical Quarterly》1997,80(12):1631-1635
Atrial geometry is preserved in the bicaval technique of cardiac transplantation. Using Doppler echocardiography, we investigated the impact of this technique on preservation of atrial function and found that echocardiographic indexes of atrial function are improved in bicaval cardiac transplants versus the standard orthotopic transplants. 相似文献
974.
An EIA method on single donor solubilized HLA antigens for the identification of anti-HLA antibodies
MP Emonds H Claeys A Volckaerts J Dendievel C Vermylen 《Canadian Metallurgical Quarterly》1997,19(2):129-136
Primary biliary cirrhosis (PBC) is an immunologically mediated disease in which activated T lymphocytes attack and destroy epithelial cells in the small intralobular bile ducts of genetically susceptible patients. This article reviews the results of treatment of PBC with immunomodulatory agents. Results with drugs such as glucocorticoids, azathioprine, and chlorambucil have been disappointing because of either limited efficacy (azathioprine), toxicity (chlorambucil), or both (glucocorticoids). Colchicine improved tests of liver function in three prospective studies and was associated with improved survival for up to 4 years. However, survival benefits were lost at 8 years. Colchicine appears to slow the rate of progression of PBC but not to stop it. Preliminary results suggest that colchicine may have synergistic effects if used together with ursodeoxycholic acid, particularly in patients who are only partially responsive to ursodeoxycholic acid. Results with cyclosporine have been disappointing because of limited efficacy and predictable toxicity. The modest improvement in tests of liver function and survival are counterbalanced by the development of hypertension in some and worsening renal function in most. There is little beneficial effect on symptoms or histology. Results with methotrexate are promising. There are improvements in symptoms and tests of liver function that are equal to those seen with ursodeoxycholic acid and significant improvement in liver histology. Some patients, particularly those with striking inflammation and granulomas in portal triads, appear to have achieved sustained remission while on methotrexate. The effects of methotrexate are additive to those of ursodeoxycholic acid in patients whose blood tests have responded only partially to ursodeoxycholic acid. The most effective treatment of PBC will most likely use a combination of drugs such as ursodeoxycholic acid, colchicine, and methotrexate. 相似文献
975.
976.
977.
Recent observations at operating plants and subsequent US NRC requirements have identified flow stratification in surge lines as a phenomenon that must be considered in the design basis of surge lines. To address these concerns, the stratified loading conditions were included in the design of YGN 3 and 4 surge line as a design basis transient and pipe temperature and displacement measurement were taken during YGN 3 pre-core hot functional testing to determine the degree of surge line flow stratification. The measured displacements and temperatures were extensively reviewed and evaluated in detail: (1) to verify the validity of the thermal hydraulic model used to predict the pipe top-to-bottom temperature differentials; (2) to analytically correlate measured surge line temperatures and displacements; and (3) to confirm the validity of the stratified flow analysis procedure. This paper shows that the stratified flow phenomenon is generic and therefore generic loadings can be developed and evaluated for the surge line analyses. 相似文献
978.
M Beltramo N Stella A Calignano SY Lin A Makriyannis D Piomelli 《Canadian Metallurgical Quarterly》1997,277(5329):1094-1097
Anandamide, an endogenous ligand for central cannabinoid receptors, is released from neurons on depolarization and rapidly inactivated. Anandamide inactivation is not completely understood, but it may occur by transport into cells or by enzymatic hydrolysis. The compound N-(4-hydroxyphenyl)arachidonylamide (AM404) was shown to inhibit high-affinity anandamide accumulation in rat neurons and astrocytes in vitro, an indication that this accumulation resulted from carrier-mediated transport. Although AM404 did not activate cannabinoid receptors or inhibit anandamide hydrolysis, it enhanced receptor-mediated anandamide responses in vitro and in vivo. The data indicate that carrier-mediated transport may be essential for termination of the biological effects of anandamide, and may represent a potential drug target. 相似文献
979.
N. Mitchell A. Alekseev R. Gallix D. Holland R. Meyder A. Panin M. Shimada F. Wong E. Zapretelina 《Journal of Fusion Energy》1997,16(1-2):25-35
The ITER magnet system consists of structurally linked sets of toroidal (TF) and poloidal (PF) field coils, central solenoid (CS), and various support structures. The coils are superconducting, force flow Helium cooled with a Kapton-Glass-Epoxy multilayer insulation system. The stored magnetic energy is about 100GJ in the TF system and 20GJ in the PF-CS. Coils and structure are maintained at 4 K by enclosing them in a vacuum cryostat. The cryostat, comprising an outer envelope to the magnets, forms most of the second radioactivity confinement barrier. The inner primary barrier is formed by the vacuum vessel, its ports and their extensions. To keep the machine size within acceptable bounds, it is essential that the magnets are in close proximity to both of the nuclear confinement barriers. The objective of the magnet design is that, although local damage to one of the barriers may occur in very exceptional circumstances, large scale magnet structural or thermal failure leading to simultaneous breaching of both barriers is not credible. Magnet accidents fall into three categories: thermal (which includes arcing arising from insulation failure and local overheating due to discharge failure in the event of a superconductor quench), structural (which includes component mechanical failure arising from material inadequacies, design errors and exceptional force patterns arising from coil shorts or control failures), and fluid (Helium release due to cooling line failure). After a preliminary survey to select initial faults conceivable within the present design, these faults are systematically analyzed to provide an assessment of the damage potential. The results of this damage assessment together with an assessment of the reliability of the monitoring and protective systems, shows that the magnets can operate with the required safety condition. 相似文献
980.