全文获取类型
收费全文 | 2100篇 |
免费 | 1篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 15篇 |
金属工艺 | 1篇 |
建筑科学 | 1篇 |
矿业工程 | 5篇 |
能源动力 | 1篇 |
轻工业 | 11篇 |
水利工程 | 4篇 |
石油天然气 | 2篇 |
无线电 | 11篇 |
一般工业技术 | 14篇 |
冶金工业 | 2032篇 |
原子能技术 | 2篇 |
自动化技术 | 1篇 |
出版年
2023年 | 2篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 2篇 |
2014年 | 4篇 |
2013年 | 2篇 |
2012年 | 1篇 |
2011年 | 3篇 |
2010年 | 1篇 |
2009年 | 1篇 |
2008年 | 2篇 |
2007年 | 1篇 |
2005年 | 1篇 |
2004年 | 5篇 |
2003年 | 6篇 |
2000年 | 2篇 |
1999年 | 56篇 |
1998年 | 603篇 |
1997年 | 404篇 |
1996年 | 247篇 |
1995年 | 147篇 |
1994年 | 111篇 |
1993年 | 124篇 |
1992年 | 12篇 |
1991年 | 22篇 |
1990年 | 13篇 |
1989年 | 19篇 |
1988年 | 30篇 |
1987年 | 21篇 |
1986年 | 17篇 |
1985年 | 10篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 10篇 |
1981年 | 15篇 |
1980年 | 15篇 |
1979年 | 1篇 |
1978年 | 5篇 |
1977年 | 45篇 |
1976年 | 117篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1965年 | 1篇 |
1962年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有2101条查询结果,搜索用时 31 毫秒
991.
992.
Multiple cystic lesions in brain parenchyma supplied by the anterior cerebral circulation is a recognized pattern of cerebral injury associated with hypoxic-ischemic encephalopathy in the term infant. This report presents a series of seven infants (gestational age, 39.3 +/- 2.8 weeks; range, 36 to 44 weeks) who developed multicystic encephalomalacia in the distribution of the anterior cerebral circulation after severe neonatal asphyxia. Cerebral imaging and pathologic studies demonstrate relative preservation of the cerebellum, brain stem, and cerebral structures supplied by the vertebrobasilar circulation. Compared to the vertebrobasilar vasculature, the anterior cerebral vessels in the term infant have dense sympathetic innervation. Asphyxia, a potent sympathetic stimulator, may induce vasoconstriction in the anterior circulation and differentially accentuate the effects of hypoxia/ischemia on cerebral tissue. 相似文献
993.
This study examined gender differences in 162 female and 65 male patients with cancer referred to home care. Data were collected before hospital discharge using the Multidimensional Functional Assessment Questionnaire, the Karnofsky Performance Status, and the Quality of Life-Cancer Scale. Controlling for age and stage of disease, the results showed that men reported significantly more cancer-related impairments, more limitations in activity of daily living, and poorer social resources than women. No gender differences were found in quality of life, perceived emotional health, perceived physical health, performance status, and comorbidity. Significant predictors of self-care activities were: for women perceived physical health, Karnofsky Performance Status, and stage of disease (58% variance explained); for men Karnofsky Performance Status and medication taken (67% variance explained). Gender differences should be considered in discharge planning to provide appropriate home care services for male and female patients with cancer. 相似文献
994.
Progress in understanding the basis of resistance to rifampicin (RifR) has allowed molecular tests for the detection of drug-resistant tuberculosis to be developed. One hundred thirteen strains of Mycobacterium tuberculosis isolated from patients with multidrug resistant tuberculosis (MDR-TB) were investigated for genotypic analysis of RifR by polymerase chain reaction-heteroduplex formation (PCR-HDF) and characterization of mutations by automated DNA sequencing of the rpoB gene. A subset of isolates (22) representative of different mutations as confirmed by sequence analysis were also evaluated by the Line Probe Assay (LiPA). In 106 of the RifR strains, 24 mutations within an 81-bp region of the rpoB gene affecting 13 amino acids were observed. Most isolates (7/8) harboring Leu533 --> Pro codon mutation required minimum inhibitory concentrations (MICs) of < or = 8 microg/ml. There was geographic variation in the frequency of occurrence of particular rpoB mutations, with the Ser531 --> Leu/Trp codon mutation found in 59/113 of isolates. Although there are certain limitations in the use of both the rapid PCR-HDF diagnostic assay and the LiPA for the detection of rifampicin susceptibility of M. tuberculosis, these provide important and convenient tools for identifying and managing patients with MDR-TB. 相似文献
995.
LIa Mel'nichenko II Sheleketina LP Averianova SS Iagmur 《Canadian Metallurgical Quarterly》1997,(6):53-56
Our studies on phosphatide, a food concentrate, produced as a by-product during the extraction of an edible oil in the oil-extraction plants, showed its high efficacy in patients (n = 52) with abnormalities of the hepatobiliary system. The drug having more than 40 weight percent of phosphorus-containing lipids appeared to be efficacious not only in respect of the subjective status of the patients but also the functional state of the liver and paraments characterizing lipid metabolism. 相似文献
996.
OBJECTIVE: To determine if the use of a catheter-valve rather than a standard drainage system decreases the morbidity associated with the use of a long-term catheter. PATIENTS AND METHODS: One hundred patients undergoing long-term catheterization were recruited into a prospective randomized study to investigate the acceptability and determine any increase in infection associated with the use of a catheter-valve, compared with the standard drainage system. Each patient participated in the study protocol for 3 months, during which the frequency of urinary tract infection was assessed, and the patients' views obtained using a standard questionnaire and by interview. RESULTS: Ninety-four patients completed the study; most (92%) were happy or satisfied with the valve, as opposed to only 35% of those using a standard drainage bag. There was no significant difference between the groups in the incidence of urinary tract infections. CONCLUSION: The patients who used the standard drainage system felt their level of activity was impaired, whereas the group who were using the valve did not. In the long-term the valve was cheaper and caused less morbidity, but because it is constructed to allow one-way flow, this was not associated with an increase in the incidence of urinary tract infections. 相似文献
997.
998.
The lpxC (envA) gene of Escherichia coli encodes UDP-3-O-acyl-GlcNAc deacetylase, the second and committed step of lipopolysaccharide biosynthesis. Although present in all gram-negative bacteria examined, the deacetylase from E. coli is the only example of this enzyme that has been expressed and purified. In order to examine other variants of this protein, we cloned the Pseudomonas aeruginosa deacetylase structural gene from a lambda library as a 5.1-kb EcoRI fragment. The LpxC reading frame encodes an inferred protein of 33,435 Da that is highly homologous to the E. coli protein and that possesses a nearly identical hydropathy profile. In order to verify function, we subcloned the P. aeruginosa lpxC gene into the T7-based expression vector pET11a. Upon induction at 30 degrees C, this construct yielded active protein to approximately 18% of the soluble fraction. We devised a novel, rapid, and reproducible assay for the deacetylase which facilitated purification of the enzyme in three steps. The purified recombinant protein was found to be highly sensitive to EDTA yet was reactivated by the addition of excess heavy metal, as was the case for crude extracts of P. aeruginosa. In contrast, deacetylase activity in crude extracts of E. coli was insensitive to EDTA, and the extracts of the envA1 mutant were sensitive in a time-dependent manner. The lpxC gene has no significant homology with amidase signature sequences. Therefore, we assign this protein to the metalloamidase family as a member with a novel structure. 相似文献
999.
1000.
EJ Hoffenberg SS Rothenberg D Bensard JM Sondheimer RJ Sokol 《Canadian Metallurgical Quarterly》1997,151(10):993-998
BACKGROUND: Abdominal pain in childhood is common yet frustrating when unexplained. OBJECTIVE: To describe the clinical features and outcome of 8 children (6 girls and 2 boys; mean[+/- SD] age, 13 +/- 2 years) with unexplained abdominal pain who underwent exploratory laparoscopy. SETTING: All 8 patients were examined at an academic pediatric gastroenterology center and referred for exploratory laparoscopy because of unexplained abdominal pain. Laparoscopy was offered after family agreement to pursue behavioral management if the pain and disability did not improve. RESULTS: In all 8 children, laparoscopy detected an anomaly at a site corresponding to that of the abdominal pain. Findings were adhesions in 7 children (3 colonic, 2 ileocecal, 1 gastric, and 1 appendiceal) and ovarian torsion in 1 child. At a mean follow-up of 12.6 months, the abdominal pain had completely resolved in 6 children, notably improved in 1 child, and continued unchanged in 1 child. Disability completely resolved in 2 of 3 children. CONCLUSIONS: In children with unexplained abdominal pain that is acute in onset, well described, and suggestive of peritoneal involvement, exploratory laparoscopy (1) successfully ends the cycle of abdominal pain in most cases; and (2) commonly identifies abnormalities, usually adhesions. However, whether laparoscopy, the placebo effect, or both promote the healing process is unclear. Further study is needed to develop criteria for referral for laparoscopic evaluation of unexplained abdominal pain. 相似文献