首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2477篇
  免费   2篇
化学工业   8篇
金属工艺   1篇
轻工业   4篇
石油天然气   1篇
一般工业技术   2篇
冶金工业   2457篇
自动化技术   6篇
  2016年   2篇
  2015年   1篇
  2014年   1篇
  2013年   1篇
  2012年   1篇
  2006年   2篇
  2004年   3篇
  2003年   6篇
  1999年   76篇
  1998年   809篇
  1997年   408篇
  1996年   288篇
  1995年   159篇
  1994年   121篇
  1993年   175篇
  1992年   30篇
  1991年   24篇
  1990年   29篇
  1989年   20篇
  1988年   30篇
  1987年   29篇
  1986年   22篇
  1985年   25篇
  1983年   1篇
  1982年   12篇
  1981年   10篇
  1980年   26篇
  1978年   4篇
  1977年   52篇
  1976年   108篇
  1974年   1篇
  1955年   3篇
排序方式: 共有2479条查询结果,搜索用时 12 毫秒
31.
Dextropropoxyphene hydrochloride increases significantly oxygen uptake in whole rat brain homogenates at concentrations of 10(-4), 10(-5), 10(-6) M when using sucrose 0.25 M pH 7.4 as incubation medium. If substrate and cofactors are added to the sucrose, this drug decreases oxygen uptake at 10(-3) M concentration in brain and liver rat homogenates, and it also decreases significantly the P:O quotient of mitochondria in both organs by uncoupling the oxidative phosphorylation.  相似文献   
32.
In 13 patients with systemic lupus erythematosus, globulin fractions of sera from serial bleedings were assayed for the induction of serotonin release from normal platelets. Releasing activity appeared at some time in the sera of seven patients, five of whom had episodes of thrombocytopenia. Conversely, only one patient manifested thrombocytopenia without the occurrence of serotonin releasing activity at any time. In three patients with episodes of thrombocytopenia, increases in serotonin releasing activity temporally coincided with drops in platelet count. These data show that levels of circulating platelet serotonin releasing factor(s) vary in the course of systemic lupus erythematosus and these variations may be inversely related to the platelet count in particular patients.  相似文献   
33.
The treatment of high blood pressure at the general medical clinic of a traditionally oriented university hospital was found to be unsatisfactory for most patients. Charts of all hypertensive patients (diastolic blood pressure, greater than or equal to 105 mm Hg) who made their first clinic visit in 1964 or 1971 were reviewed. Half of all patients were lost to follow-up within the first year, and blood pressure control was achieved by only one third of the patients. New information contained in the Veterans Administration study reports (1967 and 1970) had no effect on workup, compliance, or blood pressure decline. Furthermore, no significant relationship was found between blood pressure reduction and medical process, therapeutic regimens, or patient compliance. These data suggest that, in contrast to experience obtained in programs specifically designed for long-term management of this chronic disease, the present-day general medical clinic cannot satisfy the needs of most hypertensive patients.  相似文献   
34.
1. The characteristics of absorption of individual amino acids from amino acid mixtures simulating casein and from enzymic hydrolysates of casein containing oligopeptides as well as free amino acids are known to be different. The differences, which are attributable to mucosal uptake of small peptides, involve more rapid absorption from the enzymic hydrolysates of certain amino acids which are relatively slowly absorbed from the amino acid mixtures. This could lead to more effective utilization of amino acids from the enzymic hydrolysates than from the amino acid mixtures. 2. To obtain further information bearing on this hypothesis, we have used a recently developed technique for portal cannulation in the guinea pig to make a preliminary investigation of amino acid concentrations in the portal venous plasma at intervals after the infusion into the duodenum of equivalent amounts of (a) an amino acid mixture simulating casein and (b) a partial enzymic (papain followed by kidney peptidases) hydrolysate of casein, the two preparations being infused in separate experiments. 3. For some amino acids, such as leucine, isoleucine, valine, phenylalanine and lysine, the curves after the enzymic hydrolysate were fairly similar to the corresponding curves after the amino acid mixture, though usually slightly lower. With other amino acids, the curves after the enzymic hydrolysate were very much lower than the corresponding curves after the amino acid mixture. With serine, glutamine, proline and glycine this discrepancy was particularly great. 4. The results cannot yet be fully explained, but their main features are explicable by the hypothesis that the lower amino acid concentrations in portal plasma after the enzymic hydrolysate are the result of entry of amino acids into the portal blood in peptide form, in which they would not be detectable by the analytical technique employed, and possibly also of more rapid clearance of amino acids from the blood during absorption of this preparation.  相似文献   
35.
Cyclofenil is a new diphenyl ethylene derivative related to stilboestrol without oestrogenicity but with marked effects on connective tissue metabolism. The drug has been tested, in a daily dose of 200mg X3, in six patients with progressive systemic sclerosis (PSS) to analyze the expected beneficial effects on the PSS symptoms. The typical skin hardness, joint and muscle rigidity, and reduced breathing capacity were improved to varying dgrees. The only side-effect was a slight transient liver enzyme elevation in 1 out of 6 patients. A slight increase was found in urinary calcium and hydroxyproline excretion. In several cases serum calcium, cholesterol, triglyceride and in some cases the serum uric acid levels were decreased. The ANF titres diminished to varying degrees in 4 out of 6 patients. These results indicate that further detailed clinical and laboratory studies on the therapeutic potential of cyclofenil in PSS and other diseases affecting connective tissue seen to be justified.  相似文献   
36.
The effects of zinc and copper salts on the survival of the two species of freshwater fish, common carp, Cyprinus carpio, and grass carp, Ctenopharyngodon idellus, were investigated. It was discovered that the levels of tolerance to the concentration of the metals were species-specific. Cyprinus carpio was found to be more susceptible to copper, whereas Ctenopharyngodon idellus was more susceptible to zinc. In general, copper was more toxic than zinc, as revealed by the survival times. The body and the gills of dead fish seemed to be covered by a veil-like film which looked like coagulated mucus and which was formed by the heavy-metal ions reacting with some constituents of the mucus and which was formed by the heavy-metal ions reacting with some constituents of the mucus secreted by the gill. The histopathological assessment of the gill and liver of Cyprinus carpio was also carried out. Particles were observed around the gills of the dead fish treated with zinc and copper salts, although no other major changes were found in the gill. Several histopathological changes were observed in the livers, including the presence of particles. The symptoms of the liver suggested that the internal injury was also an important feature of the intoxicants.  相似文献   
37.
PURPOSE: The 4-defect repair of grade 4 cystocele corrects discrete and severe deficiencies of vesicourethral support. We describe this technique used during pelvic reconstruction in 130 women. MATERIALS AND METHODS: During a 3-year period 130 patients (age range 35 to 96 years) underwent repair of grade 4 cystocele using the 4-defect repair technique. Cystocele repair had been performed in 60 patients (46%) and hysterectomy had been performed in 85 (65%). A "goalpost incision" is used in the vaginal wall to facilitate separation of the wall from underlying perivesical fascia, entry into the retropubic space, and exposure of the urethropelvic ligament, cardinal ligament and perivesical fascia. The 4 polypropylene sutures are used to provide an anterior vaginal wall sling which is modified to incorporate perivesical fascia and cardinal ligaments. Central defect repair is achieved by approximation of the cardinal ligaments and midline plication of the perivesical fascia over absorbable mesh. RESULTS: A total of 112 patients were available for followup which ranged from 6 to 42 months (mean 21). Repair of grade 4 cystocele was accompanied by other transvaginal repairs in 94 patients (83%), including rectocele repair in 81, hysterectomy in 22 and enterocele repair in 31. Of the patients 92% had excellent objective and subjective results for anatomical cystocele repair. Of the patients with preoperative stress urinary incontinence 90% had excellent or good subjective results. De novo urge incontinence was seen in 7% of patients. CONCLUSIONS: The 4-defect repair technique relies on anatomical restoration of 4 distinct deficiencies of pelvic support and is highly effective for relief of symptoms of grade 4 cystocele.  相似文献   
38.
39.
Colonization of the nasopharynx by a middle ear pathogen is the first step in the development of otitis media in humans. The establishment of an animal model of nasopharyngeal colonization would therefore be of great utility in assessing the potential protective ability of candidate vaccine antigens (especially adhesins) against otitis media. A chinchilla nasopharyngeal colonization model for nontypeable Haemophilus influenzae (NTHI) was developed with antibiotic-resistant strains. This model does not require coinfection with a virus. There was no significant difference in the efficiency of NTHI colonization between adult (1- to 2-year-old) and young (2- to 3-month-old) animals. However, the incidence of middle ear infection following nasopharyngeal colonization was significantly higher in young animals (83 to 89%) than in adult chinchillas (10 to 30%). Chinchillas that had recovered either from a previous middle ear infection caused by NTHI or from an infection by intranasal inoculation with NTHI were completely protected against nasopharyngeal colonization with a homologous strain and were found to be the best positive controls in protection studies. Systemic immunization of chinchillas with inactivated whole-cell preparations significantly protected animals not only against homologous NTHI colonization but also partially against heterologous NTHI infection. In all protected animals, significant serum anti-P6 and anti-HMW antibody responses were observed. The outer membrane P6 and high-molecular-weight (HMW) proteins appear to be promising candidate vaccine antigens to prevent nasopharyngeal colonization and middle ear infection caused by NTHI.  相似文献   
40.
OBJECTIVE: To compare the composition and mechanical properties of the newly developed bladder acellular matrix graft (BAMG) with the normal urinary bladder in rat, pig and human. MATERIALS AND METHODS: Rat, pig and human urinary bladders were harvested and divided into control and experimental groups. For the latter, BAMGs were prepared, and light and transmission electron microscopic studies performed. Strips from the normal bladders and the BAMGs (10 in each group) were tested under tension, and the ultimate tensile strength, maximum strain, and elastic modulus were determined from stress/strain curves. RESULTS: Both types I and III collagen, as well as elastic fibres, were observed as major components of the matrix scaffold. There were more collagen type I fibres in the rat than in the pig and human BAMGs, whereas the pig, and particularly the human, both showed higher levels of type III collagen and elastic fibres. These different matrix scaffold patterns were confirmed by electron microscopy. Results from biomechanical testing showed no significant differences for strength, strain or elastic modulus between BAMG and control bladder strips, except in the rat where the maximum strain values were significantly lower. CONCLUSION: There are variations in the acellular matrix structure with similar biomechanical properties between the BAMG and the normal urinary bladder in three different species. These results may underscore the potential of the BAMG. Furthermore, this in vitro model provides a suitable method to study the mechanical properties of the urinary bladder and may serve as a diagnostic tool for various investigations.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号