全文获取类型
收费全文 | 4795篇 |
免费 | 4篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 15篇 |
化学工业 | 160篇 |
金属工艺 | 67篇 |
机械仪表 | 39篇 |
建筑科学 | 13篇 |
矿业工程 | 6篇 |
能源动力 | 2篇 |
轻工业 | 10篇 |
水利工程 | 13篇 |
石油天然气 | 21篇 |
无线电 | 30篇 |
一般工业技术 | 173篇 |
冶金工业 | 4137篇 |
原子能技术 | 90篇 |
自动化技术 | 24篇 |
出版年
2022年 | 14篇 |
2021年 | 22篇 |
2020年 | 12篇 |
2019年 | 13篇 |
2018年 | 18篇 |
2017年 | 18篇 |
2016年 | 18篇 |
2015年 | 9篇 |
2014年 | 20篇 |
2013年 | 16篇 |
2012年 | 27篇 |
2011年 | 21篇 |
2010年 | 16篇 |
2009年 | 19篇 |
2008年 | 19篇 |
2007年 | 27篇 |
2006年 | 22篇 |
2005年 | 21篇 |
2004年 | 18篇 |
2003年 | 17篇 |
2002年 | 15篇 |
2001年 | 12篇 |
2000年 | 13篇 |
1999年 | 135篇 |
1998年 | 1377篇 |
1997年 | 771篇 |
1996年 | 477篇 |
1995年 | 282篇 |
1994年 | 245篇 |
1993年 | 239篇 |
1992年 | 40篇 |
1991年 | 68篇 |
1990年 | 44篇 |
1989年 | 44篇 |
1988年 | 65篇 |
1987年 | 56篇 |
1986年 | 38篇 |
1985年 | 52篇 |
1984年 | 13篇 |
1983年 | 14篇 |
1982年 | 20篇 |
1981年 | 33篇 |
1980年 | 41篇 |
1978年 | 17篇 |
1977年 | 90篇 |
1976年 | 147篇 |
1975年 | 13篇 |
1974年 | 16篇 |
1973年 | 10篇 |
1972年 | 10篇 |
排序方式: 共有4800条查询结果,搜索用时 15 毫秒
91.
SM Ouellette 《Canadian Metallurgical Quarterly》1997,8(2):62-68
Health care spending in the United States outpaces all other nations or 14% of the gross domestic product. Although the escalating increases in health care costs which have characterized the industry over the past quarter century have begun to slow down, if changes in the current health care policy are not implemented, spending is expected to increase at a rate of 11.5% during each of the next 5 years. Health care spending will reach $1.1 trillion or 15% of the gross domestic product in the near future. Both hospitals and universities are facing mounting pressures to reduce their costs and improve their services. In this environment, it becomes increasingly important for directors of nurse anesthesia programs to financially justify their existence. This discussion begins with a brief overview of nurse anesthesia education in the United States. The value of and need for nurse anesthetists in the US health care system is addressed. Advantages and disadvantages of hospital versus university-based programs are highlighted and funding sources identified. Future needs and challenges in nurse anesthesia education conclude this discussion. 相似文献
92.
Quinine induces changes in the motion of the cupula in the lateral line canal of the African knife-fish in response to sinusoidal water movements. Two different phases in the action of quinine on the cupular frequency response can be discerned. In the first phase the best frequency, i.e., the frequency at which the cupular vibratory displacement is maximal in response to constant-amplitude sinusoidal canal fluid displacement, shifts toward higher frequencies. During this phase, lasting about 70-100 min, the best frequency increases by a factor between 1.3 and 1.5. In the second phase, during roughly the following 90 min, the best frequency decreases gradually to a value 0.3-0.5 times that observed before the application of quinine. 相似文献
93.
94.
beta2-Integrin adhesion molecules play crucial roles in monocyte transmigration and adherence to the inflamed extracellular matrix. While integrin engagement contributes to inflammatory cell activation, little is known about the precise signaling pathways that are important to integrin-dependent monocyte activation. We examined the role of tyrosine phosphorylation and extracellular-signal regulated kinase (ERK) activity in beta2-integrin signaling in monocytes. Cross-linking of the LFA-1 (CD11a/CD18) and MAC-1 (CD11b/CD18) integrins on the surface of THP-1 monocytic cells induced the accumulation of tyrosine phosphoproteins. As part of this signal both ERK-1 and ERK-2 are tyrosine phosphorylated. In vitro kinase assays documented an increase in ERK-2 activity following both LFA-1 and MAC-1 cross-linking. beta2-Integrin cross-linking also led to a marked increase in 4-h procoagulant activity (PCA) in THP-1 cells and purified human monocytes. Inhibition of tyrosine phosphorylation by genistein (10 microg/ml), or selective ERK inhibition with PD98059 (10 microM), was able to block the integrin-dependent induction of PCA in both THP-1 cells and human monocytes. Thus, beta2 integrin signaling in monocytic cells can flow through the tyrosine phosphorylation and activation of the ERK mitogen activated protein kinases, which is essential for the subsequent expression of tissue factor. These results suggest that the ERK proteins likely function to integrate various adhesion-dependent signals during the process of monocyte transmigration. 相似文献
95.
LG Lee SL Spurgeon CR Heiner SC Benson BB Rosenblum SM Menchen RJ Graham A Constantinescu KG Upadhya JM Cassel 《Canadian Metallurgical Quarterly》1997,25(14):2816-2822
We have synthesized a set of four energy transfer dyes and demonstrated their use in automated DNA sequencing. The donor dyes are the 5- or 6-carboxy isomers of 4'-aminomethylfluorescein and the acceptor dyes are a novel set of four 4,7-dichloro-substituted rhodamine dyes which have narrower emission spectra than the standard, unsubstituted rhodamines. A rigid amino acid linker, 4-aminomethylbenzoic acid, was used to separate the dyes. The brightness of each dye in an automated sequencing instrument equipped with a dual line argon ion laser (488 and 514 nm excitation) was 2-2.5 times greater than the standard dye-primers with a 2 times reduction in multicomponent noise. The overall improvement in signal-to-noise was 4- to 5-fold. The utility of the new dye set was demonstrated by sequencing of a BAC DNA with an 80 kb insert. Measurement of the extinction coefficients and the relative quantum yields of the dichlororhodamine components of the energy transfer dyes showed their values were reduced by 20-25% compared with the dichlororhodamine dyes alone. 相似文献
96.
97.
SM Banajeh 《Canadian Metallurgical Quarterly》1998,44(6):343-346
In May 1996, the team working on infantile laparoscopy (GECI) carried out a retrospective study (using questionnaires) to analyse the use of laparoscopy in child postoperative obstructions (involving bands or adhesions). Of the 86 laparoscopic attempts, 66 could have been performed without conversion. Technical difficulties were responsible for the majority of the conversions performed on children aged 3 years younger than the average age in this study (10 years old). Digestive perforation accounts for a fifth of conversions, the perforations either occurring when the operational trocars were introduced (3 cases), or during viscerolysis (2 cases). For 5 children the treatment failed at an early stage (in the month following the operation). Relapses occurred in 3 children, usually at a later date (between 6 months and 3 years). Laparoscopic treatment of bowel obstruction should always be attempted, for as the results of the study show, morbidity is low and mortality is nil and the postoperative phase is quick and painless. 相似文献
98.
99.
100.
OBJECTIVE: To test the efficacy and safety of low-dose oral pulse methotrexate therapy in patients with idiopathic granulomatous hepatitis who had complications of, did not respond to, or refused glucocorticoid therapy. DESIGN: Prospective case study. SETTING: Academic medical center hospital. PATIENTS: Seven patients with biopsy-proven, idiopathic granulomatous hepatitis who could not tolerate or were unresponsive to glucocorticoid therapy. INTERVENTION: Low-dose oral pulse methotrexate, 15 mg/wk. MEASUREMENTS: Temperature, symptoms, dose of concurrent glucocorticoids, biochemical tests of liver function, side effects of methotrexate, and assessment of liver biopsy specimens. RESULTS: All six febrile patients became afebrile within 3 months of starting methotrexate. Fatigue and anorexia improved in all patients. Glucocorticoid therapy was successfully discontinued within 6 months of starting methotrexate in four patients receiving prednisone at entry. Liver biopsy specimens were obtained again after methotrexate therapy and showed absence of granulomas in four of four patients. The minimum effective dose of methotrexate was 0.20 mg/kg body weight per week. No serious adverse effects and no failures to respond to methotrexate therapy were noted in this group of patients. In three patients, methotrexate therapy has been successfully tapered without signs or symptoms of recurrent disease. CONCLUSIONS: Low-dose oral pulse methotrexate was effective in treating patients with granulomatous hepatitis. 相似文献