全文获取类型
收费全文 | 1295篇 |
免费 | 19篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 102篇 |
金属工艺 | 11篇 |
机械仪表 | 5篇 |
建筑科学 | 10篇 |
能源动力 | 10篇 |
轻工业 | 86篇 |
水利工程 | 9篇 |
石油天然气 | 6篇 |
无线电 | 35篇 |
一般工业技术 | 53篇 |
冶金工业 | 931篇 |
原子能技术 | 6篇 |
自动化技术 | 50篇 |
出版年
2024年 | 5篇 |
2023年 | 6篇 |
2022年 | 20篇 |
2021年 | 29篇 |
2020年 | 16篇 |
2019年 | 23篇 |
2018年 | 12篇 |
2017年 | 21篇 |
2016年 | 13篇 |
2015年 | 9篇 |
2014年 | 19篇 |
2013年 | 22篇 |
2012年 | 26篇 |
2011年 | 24篇 |
2010年 | 21篇 |
2009年 | 21篇 |
2008年 | 18篇 |
2007年 | 12篇 |
2006年 | 7篇 |
2005年 | 10篇 |
2004年 | 9篇 |
2003年 | 6篇 |
2002年 | 3篇 |
2001年 | 4篇 |
2000年 | 7篇 |
1999年 | 30篇 |
1998年 | 293篇 |
1997年 | 168篇 |
1996年 | 121篇 |
1995年 | 73篇 |
1994年 | 49篇 |
1993年 | 56篇 |
1992年 | 9篇 |
1991年 | 15篇 |
1990年 | 10篇 |
1989年 | 15篇 |
1988年 | 13篇 |
1987年 | 9篇 |
1986年 | 10篇 |
1985年 | 14篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 8篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 18篇 |
1976年 | 23篇 |
1975年 | 2篇 |
排序方式: 共有1316条查询结果,搜索用时 31 毫秒
991.
992.
993.
A patient with non-African Burkitt's lymphoma is reported in whom bilateral breast involvement was detected by both mammography and 67-Ga-citrate scintigraphy. The causes of breast uptake of 67Ga-citrate are reviewed, and it is noted that not only asymmetrical increases in uptake of 6767Ga-citrate are indicative of disease. 相似文献
994.
M. F. D. Medeiros S. C. S. Rocha O. L. S. Alsina C. E. M. Jer nimo U. K. L. Medeiros A. L. M. L. da Mata 《Drying Technology》2002,20(4):855-881
Studies on drying of pulps of several tropical fruits in spouted beds had shown advantages in relation to the quality of the products. However, most of the processed pulps presented serious problems of accumulation in the bed and consequently, instability of the spouted bed dynamic. The objective of this work is to analyze the influence of the chemical composition on the spouted bed performance in drying pulps of tropical fruits. Mango pulp “in natura” was used as a standard pulp. Modified pulps were obtained increasing the concentrations of reducer sugars, lipids, fibers, starch and pectin. The effect of these compositions on the fluid-dynamic and efficiency of the powder production was investigated using a factorial design. The operational conditions were maintained fixed in all experiments. The efficiency of powder production, the stable spout pressure drop and the minimum spouting flow rate were the responses analyzed. The statistical analysis of the results showed that the concentration of fibers is not a significant variable for the process. The concentrations of reducer sugars and starch showed significant influence on the fluid dynamic and these concentrations together with the lipids and pectin concentrations showed significant influences on the efficiency of powder production. 相似文献
995.
Mouse oocytes secrete a factor(s) that inhibits progesterone and enhances estradiol production by cumulus granulosa cells. The purpose of this study was to investigate the mechanisms by which the production of these steroids is modulated. Mouse oocyte-cumulus cell complexes (intact) and complexes from which the oocytes were removed microsurgically (oocytectomized; OOX) were cultured for up to 48 h in the presence of FSH (150 ng/ml) and testosterone (5 x 10(-7) M). For these experiments, all cells were obtained from antral follicles of 24- to 26-day-old mice primed with eCG. Intact complexes produced primarily estradiol, with significant accumulation occurring between 24 and 48 h. In contrast, OOX complexes produced little estradiol but, starting at 18 h of culture, released significantly more progesterone than did intact complexes. Progesterone accumulation in cocultures of denuded oocytes with either OOX complexes or monolayers of mural granulosa cells was significantly reduced compared to that with OOX complexes or mural granulosa cells cultured alone. If dibutyryl cAMP replaced FSH in the cocultures, similar results were obtained, suggesting that the oocyte-secreted steroid-regulating factor acts downstream of the generation of cAMP to inhibit progesterone production. Since estradiol can inhibit progesterone production by granulosa cells, we investigated the possibility that the increased progesterone released by OOX complexes was secondary to the lower estradiol production. Intact complexes cultured in the presence of the nonaromatizable androgen, 5 alpha-dihydrotestosterone, or steroidal (4-hydroxyandrostenedione) or non-steroidal (CGS 16949A) aromatase inhibitors produced little estradiol; however, progesterone production by these complexes was no different from that of estradiol-producing intact complexes. These results suggest that the steroid-regulating factor(s) secreted by occytes acts to regulate granulosa cell production of estradiol and progesterone by independent mechanisms. 相似文献
996.
E Rodney BC Vasavada TJ Sacchi 《Canadian Metallurgical Quarterly》1994,330(3):216-7; author reply 217-8
997.
998.
This in vitro study evaluated the effects of etchant type, surface moisture, and resin composite type on the shear bond strength of dentin adhesives. Three adhesives which bond to etched dentin were used in the study: All-Bond 2, Amalgambond, and Clearfil Photo Bond. Occlusal enamel was removed from 200 human molars to expose dentin. The dentin surfaces were etched, treated with a dentin adhesive system, and bonded with resin composite. After thermocycling and storage, the composite columns were fractured from dentin using an Instron machine. Bond strengths were calculated and subjected to a statistical analysis. Etchant type, surface moisture, and resin composite type all had significant effects on dentin bond strengths. Overall, the highest bond strengths were obtained with 10/3 etchant, moist dentin, and hybrid composite. The highest bond strengths for All-Bond 2 and Amalgambond were obtained by using the manufacturer's recommended etchant, moist dentin, and a hybrid composite. The mean bond strengths for All-Bond and Amalgambond under these conditions were 22.5 and 19.0 MPa, respectively. Clearfil Photo Bond had significantly lower bond strengths, but was relatively unaffected by changes in experimental conditions. 相似文献
999.
Twenty-five patients with liver cirrhosis and portal hypertension were admitted for creation of a transjugular intrahepatic portosystemic shunt (TIPS). The procedure was successful in 22 patients (technical success 88%). The mean portal pressure gradient was lowered from 24.5 mmHg before to 11.4 mmHg after TIPS. Two early and three late occlusions were observed (primary patency rate 78%). The rate of secondary interventions was 41%. Five times a hepatic vein stenosis was dilated and stented, two times an occluded shunt was recanalized, two times a new shunt was created parallel to an occluded (secondary patency rate within a maximum of 16 months 95%). In two patients sepsis occurred which was effectively treated with antibiotics, two patients died shortly after TIPS due to hepatorenal syndrome and hepatic failure, respectively. There was no recurrent bleeding. Two patients developed hepatic encephalopathy; both improved after protein restriction. The authors conclude that TIPS is an alternative procedure to shunt surgery, especially for patients who cannot benefit from sclerotherapy. 相似文献
1000.
Many, but not all, adult rhesus monkeys spontaneously develop significant increases in body fat mass, and many, but not all, progress to develop overt adult-onset type II diabetes. The purpose of this study was to determine whether both an increase in body fat and onset of diabetes could be simultaneously prevented through long-term maintenance of stable normal adult body weight by caloric titration. Eight adult male monkeys were provided a complete normal chow diet, but with daily amounts restricted and titrated on a weekly basis to maintain a constant body weight (weight-stabilized group). This regimen has been continued for 5-9 yr (mean +/- SD of 7 +/- 0.5 yr) with monkeys attaining the age of 17.9 +/- 0.6 yr and with maintenance of normal body fat (17.7 +/- 1.8%). The age-matched ad libitum fed group (18.1 +/- 0.2 yr of age) consisted of 19 monkeys maintained under identical laboratory conditions and diet, but with food available ad libitum. Results showed weight-stabilized monkeys weighed significantly less than ad libitum fed monkeys (10.4 +/- 0.2 vs. 16.1 +/- 0.7 kg, respectively, P < 0.05) and had significantly better glucose tolerance as measured by Kglucose (glucose disappearance rate) (3.9 +/- 0.3 vs. 2.4 +/- 0.2, P +/- 0.05). Of the 19 ad libitum fed age-matched monkeys, 4 were overtly diabetic, and 6 others had significantly reduced glucose tolerance. Hyperinsulinemia did not develop in the weight-stabilized group, and beta-cell response to glucose remained normal; both were significantly different from the exaggerated levels of the ad libitum fed group (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献