全文获取类型
收费全文 | 3919篇 |
免费 | 3篇 |
专业分类
电工技术 | 6篇 |
化学工业 | 16篇 |
机械仪表 | 3篇 |
轻工业 | 26篇 |
水利工程 | 1篇 |
无线电 | 6篇 |
一般工业技术 | 9篇 |
冶金工业 | 3839篇 |
自动化技术 | 16篇 |
出版年
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2013年 | 2篇 |
2012年 | 7篇 |
2011年 | 3篇 |
2010年 | 1篇 |
2009年 | 2篇 |
2008年 | 4篇 |
2006年 | 5篇 |
2005年 | 1篇 |
2004年 | 5篇 |
2003年 | 16篇 |
2000年 | 2篇 |
1999年 | 141篇 |
1998年 | 1263篇 |
1997年 | 781篇 |
1996年 | 481篇 |
1995年 | 233篇 |
1994年 | 220篇 |
1993年 | 221篇 |
1992年 | 20篇 |
1991年 | 32篇 |
1990年 | 35篇 |
1989年 | 47篇 |
1988年 | 31篇 |
1987年 | 28篇 |
1986年 | 22篇 |
1985年 | 24篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 15篇 |
1981年 | 23篇 |
1980年 | 29篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 59篇 |
1976年 | 136篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1970年 | 2篇 |
1963年 | 1篇 |
1929年 | 1篇 |
1928年 | 1篇 |
排序方式: 共有3922条查询结果,搜索用时 15 毫秒
101.
Thirty-three HIV-positive women, 12 of whom were pregnant, participated in semistructured interviews to define areas of psychosocial need. Eighty-eight percent of the subjects reported current unemployment. A history of substance abuse was reported by 82 percent, suicide attempts by 52 percent, and sexual problems by 43 percent. Approximately 30 percent reported elevated levels of depressive symptoms on standardized symptom inventories. The pregnant women appeared psychologically healthier than the nonpregnant group. HIV-positive women face multiple psychosocial stressors and may experience significant psychological distress. 相似文献
102.
MC Giarratana L Kobari TM Neildez Nguyen H Firat S Bouchet M Lopez NC Gorin D Thierry L Douay 《Canadian Metallurgical Quarterly》1998,22(7):707-715
The aim of this study was to evaluate the ex vivo expansion of normal CD34+ cells in gas-permeable polypropylene bags suitable for clinical use. Cells were cultured for 14 days in serum-free medium supplemented with SCF, IL3, IL6, FLT3-1, G-CSF + MGDF or Epo. The bags supported the expansion of hematopoietic cells in a similar manner to small scale well or flask systems, allowing mean expansions of up to 2193-fold for total nucleated cells, 140-fold for CFU-GM and 66-fold for LTC-IC. Increasing the initial cell concentration from 5 x 10(3) to 1 x 10(5)CD34+ cells/ml induced the production of granulocytic cells with terminal differentiation while simultaneously decreasing the overall extent of expansion of the white blood cells produced. We tested the phagocytic activity and oxidative metabolism of the white blood cells produced. The percentage of phagocytic cells was 39+/-0.5% in expanded cultures derived from fractions initiated at 5 x 10(3), 10(4) or 10(5) cells/ml and 45+/-6% in cultured cells obtained from starting fractions containing 5 x 10(4) cells/ml, as compared to 58+/-4% in normal controls. A study of the potential for oxygen-dependent microbe killing showed that the expanded cells produced H2O2, although in lesser quantities than control cells. We subsequently investigated the possibility of freezing expanded cells. Total cell recovery after thawing was 45+/-4%, while recoveries of progenitors and stem cells ranged from 65 to 90%, without any influence of the initial cell concentration. This new approach could be of major interest for clinical practice, as it would allow evaluation of the quality of a graft prior to its infusion and employs experimental conditions which meet the criteria for potential clinical use. 相似文献
103.
Flexion reflexes, elicited by surface stimulation, can be used to produce a simple form of stepping in spinal cord injured (SCI) humans. A drawback of this approach is a decreasing magnitude of flexion reflex to repeated presentations of the stimuli (habituation). Pilot data indicated that high intensity stimulation could produce dishabituation of the reflex. The aim of this study was to examine and quantify the inter- and intra-subject variability of the short and long term conditioning effect of high intensity stimulation on the magnitude of flexion reflexes in a larger number of SCI subjects. Dishabituation was observed in all subjects, however the amount of dishabituation observed was small and highly variable. However the use of high intensity conditioning stimulation may offer a means of coping with habituation in a small number of subjects. 相似文献
104.
105.
AH Sarker S Ikeda H Nakano H Terato H Ide K Imai K Akiyama K Tsutsui Z Bo K Kubo K Yamamoto A Yasui MC Yoshida S Seki 《Canadian Metallurgical Quarterly》1998,282(4):761-774
The association patterns between maternal anthropometric characteristics (stature, prepregnancy weight, prepregnancy body mass index, pregnancy weight gain) and newborn size (birth weight, length, head circumference) were tested with 10,240 single births taking place between 1985 and 1995 in Vienna, Austria, and 3,452 single births taking place between 1989 and 1995 in Westerstede-Ammerland (Friesland), northern Germany. Maternal size and newborn size differed highly significantly (p < 0.001) between the two genetically and socioeconomically different population groups. Furthermore, the incidence of macrosomia among newborns (birth weight greater than 4000 g) was extraordinarily high (17.9%) in the Frisian group from northern Germany. In both populations taller and heavier women with a higher weight gain during pregnancy gave birth to heavier offspring. Nevertheless, the pregnancy weight gain, which indicates environmental conditions of the mother, had only a minor impact on newborn size compared with stature and prepregnancy weight, which reflect the maternal genetic potential to a higher degree. 相似文献
106.
D Savioz B Roche T Glauser A Dobrinov C Ludwig MC Marti 《Canadian Metallurgical Quarterly》1998,13(4):154-156
Rubber band ligation is a well established treatment of internal second-degree hemorrhoids. Up to now, the long-term results (> 5 years) of this method have not been assessed. The aim of this study was to determine the long-term success rate of rubber band ligation in patients with a first episode of second-degree hemorrhoids not responding to medical treatment (local cream with laxative). A total of 92 patients who were treated between 1979 and 1997 for second-degree hemorrhoids responded to a questionnaire. The need for complementary conservative (sclerotherapy, cryotherapy or rubber band ligation) or surgical treatment was considered indicative of relapse. The collected data were analyzed according to the Kaplan-Meier method. The average follow-up time was 5.6 years. There were 21 patients who suffered a relapse. The probability of successful treatment was 0.77 (range: 0.67-0.88) after 5 years and 0.68 (range: 0.5-0.86) after 10.6 years. We conclude that rubber band ligation represent an efficient long-term treatment for second-degree hemorrhoids. Approximately two thirds of the patients are cured after 5 years and more than a half after 10 years. 相似文献
107.
JE Monteiro da Cunha MC Machado P Herman T Bacchella EE Abdo S Penteado J Jukemura A Montagnini MA Machado HW Pinotti 《Canadian Metallurgical Quarterly》1998,45(23):1452-1456
BACKGROUND/AIMS: Cicatricial biliary strictures are usually associated with high morbidity and mortality rates, frequently related to technical difficulties of their surgical repair, mainly in hilar lesions. Interference with bile duct blood supply during surgical attempts for correction is a major factor for unsuccessful results. The aim of this study is to evaluate, after an extended follow-up period, the results obtained with a modified technique for surgical correction of cicatricial biliary strictures. METHODOLOGY: The medical records of 57 patients surgically treated for cicatricial biliary strictures between January 1984 and July 1995 were reviewed and the immediate and long term results retrospectively analyzed. Patients consisted of 46 females and 11 males. The average age was 43 years. The etiology of the biliary lesion was: cholecystectomy alone (23); cholecystectomy with duct exploration (8); T tube CBD drainage (6); Biliary-enteric anastomosis stricture (16); choledochoplasty (2) and trauma (2). In 28 cases (49.1%) the stricture was located in the upper third of the bile duct, in 28 (49.1%) in the middle third and in one case (1.7%) it was low. All patients were submitted to longitudinal Roux-en-Y hepaticojejunostomy with mucosa apposition after dissection of the anterior aspect of the biliary tract. No transanastomotic stents were used. RESULTS: Ten patients (17.5%) presented 11 postoperative complications: biliary fistula (4), duodenal fistula (1), wound infection (5), and acute pancreatitis (1). Average hospital stay was 11 days and there were no postoperative mortalities. The follow-up study was possible in 54 patients and ranged from one to ten years, with an average of 2.9 years. Four patients of 28 (14%) with hilar lesions developed stricture recurrence and cholangitis episodes, whereas no patients bearing lesions below the biliary junction had such complications. CONCLUSION: Roux-en-Y hepaticojejunostomy with mucosa apposition without transanastomotic stent performed after minimal dissection of the biliary duct, thus avoiding major interference with the bile duct blood supply, is a safe and efficient method for the surgical repair of cicatricial biliary strictures. Using this technique excellent results can be obtained in the lesions below the biliary junction and acceptable results may be achieved in patients with hilar lesions. 相似文献
108.
Assembly of functional cytochrome oxidase in yeast requires Cox17, which has been postulated to deliver copper ions to the mitochondrion for insertion into the enzyme. This role for Cox17 is supported by the observation that it binds copper as a binuclear cuprous-thiolate cluster. X-ray absorption spectroscopy, together with UV-visible absorption and emission spectroscopy, indicates the presence of bound cuprous ions, trigonally coordinated by thiolate ligands. Analysis of the EXAFS shows three Cu-S bonds at 2.26 A, plus a short Cu-Cu distance of 2.7 A, indicating a binuclear cluster in Cox17. The cuprous-thiolate cluster in Cox17 is substantially more labile than structurally related clusters in metallothioneins. 相似文献
109.
Both the Na+-dependent glucose cotransporter (SGLT1) and the cystic fibrosis transmembrane conductance regulator (CFTR) modulate Na+ and fluid movement, although in opposite directions. Yet few studies have investigated a possible interrelationship between these two transporters. By using the Caco-2 human colon carcinoma cell line, we confirmed that the activities of these transporters increased with spontaneous differentiation to the enterocytic phenotype. We showed that SGLT1 was positively regulated by Cl- and that optimal activity of CFTR was dependent on the presence of glucose. We also demonstrated that inhibition of CFTR by glibenclamide or diphenylamine-2-carboxylate did not modify the activity of SGLT1 and inhibition of SGLT1 by phlorizin did not modify the activity of CFTR, although it resulted in inhibition of glycoconjugate synthesis. These results point to positive substrate-cross regulation of SGLT1 and CFTR and suggest that NaCl and glucose are important for not only Na+ absorption and fluid movement, but also for cAMP-dependent Cl- efflux, and glycoconjugate synthesis, functions that are known to be anomalous in cystic fibrosis. 相似文献
110.