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   864篇
  免费   0篇
电工技术   1篇
化学工业   2篇
轻工业   3篇
一般工业技术   3篇
冶金工业   855篇
  2020年   1篇
  2013年   1篇
  2011年   1篇
  2010年   2篇
  2006年   1篇
  2004年   2篇
  2003年   1篇
  1999年   21篇
  1998年   218篇
  1997年   144篇
  1996年   96篇
  1995年   63篇
  1994年   42篇
  1993年   45篇
  1992年   9篇
  1991年   13篇
  1990年   16篇
  1989年   18篇
  1988年   31篇
  1987年   13篇
  1986年   10篇
  1985年   14篇
  1982年   5篇
  1981年   8篇
  1980年   6篇
  1977年   23篇
  1976年   55篇
  1975年   2篇
  1955年   3篇
排序方式: 共有864条查询结果,搜索用时 328 毫秒
131.
OBJECTIVE: To determine the utility of the pressure-flow studies in the diagnosis of voiding dysfunction in women. METHODS: A case-control study was conducted on 80 women. These subjects were divided into two groups: 24 controls with a maximum flow percentile greater than or equal to 50 and no residual volume, and 56 cases with a maximum flow percentile less than or equal to 10. The clinically and statistically significant parameters of the pressure-flow study were entered into a multiple regression logistic equation as explanation variables of voiding dysfunction. RESULTS: The clinical variables that influenced voiding dysfunction were age and the presence of stress urinary incontinence. The urethral resistance average (URA) was found to be the only significant urodynamic parameter. Patients with stress urinary incontinence showed a lower probability of voiding dysfunction. Age and URA directly correlated with the probability of voiding dysfunction. CONCLUSIONS: The URA was found to be the only significant urodynamic parameter. The contractility parameters [power at maximum flow (Pw) and maximum power per bladder unit surface (Wmax)] were not found to be useful as detrusor contractility index in women.  相似文献   
132.
Composition on surface lipids of coniferous from Picea, Pinus and Larix genera (six plant species) are studied by spectral and chromatographic methods. Different content of carbonyl compounds in the summary fraction of surface lipids of coniferous, concerning componental content of hydrocarbon fraction and predominance of concrete fatty acids was shown. A substantial quantity of unethereficated fatty acids in surface lipids of plants is shown.  相似文献   
133.
Ursodeoxycholic acid (UDCA) has been shown to have beneficial effects on patients with primary biliary cirrhosis, suggesting that UDCA has immunomodulating effects. We investigated the effect of UDCA in patients with autoimmune hepatitis (AIH) which is characterized by immunological abnormalities. Eight patients with type 1 AIH were treated with 600 mg of UDCA per day for 2 years. Based on the criteria of the International Autoimmune Hepatitis Group, five patients were diagnosed as definite and three as probable type 1 AIH. Liver function tests were performed every 4 weeks, before and during UDCA therapy and the serum levels of anti-nuclear antibodies (ANA), smooth muscle antibodies (SMA), immunoglobulin G and gamma globulin were determined every 3 months. The levels of serum aspartate aminotransferase and alanine aminotransferase significantly decreased from 154 +/- 24 IU/L and 170 +/- 17 IU/L before UDCA therapy to 31 +/- 3 IU/L and 25 +/- 5 IU/L (P < 0.001) after 1 year of treatment and 28 +/- 2 IU/L and 23 +/- 4 IU/L (P < 0.001) after 2 years of treatment. After 2 years of treatment, the levels of serum immunoglobulin G and gamma globulin significantly decreased (P < 0.05) and ANA titres (5/8 patients) were reduced and SMA (3/5 patients) became negative. Furthermore, hepatic histopathological changes of four patients were assessed after 1 year of treatment, and an improvement of intrahepatic inflammation, but not fibrosis, was observed. In conclusion, these results suggest that UDCA has a beneficial therapeutic effect in patients with type 1 autoimmune hepatitis.  相似文献   
134.
Thiobarbituric acid reactant substances (TBARs) content, and the activities of glucose-6-phosphate dehydrogenase (G6PDh), citrate synthase (CS), Cu/Zn- and Mn-superoxide dismutase (SOD), catalase, and glutathione peroxidase (GPX) were measured in the lymphoid organs (thymus, spleen, and mesenteric lymph nodes (MLN)) and skeletal muscles (gastrocnemius and soleus) of adrenodemedullated (ADM) rats. The results were compared with those obtained for sham-operated rats. TBARs content was reduced by adrenodemedullation in the lymphoid organs (MLN) (28%), thymus (40%) and spleen (42%)) and gastrocnemius muscle (67%). G6PDh activity was enhanced in the MLN (69%) and reduced in the spleen (28%) and soleus muscle (75%). CS activity was reduced in all tissues (MLN (75%), spleen (71%), gastrocnemius (61%) and soleus (43%)), except in the thymus which displayed an increment of 56%. Cu/Zn-SOD activity was increased in the MLN (126%), thymus (223%), spleen (80%) and gastrocnemius muscle (360%) and was reduced in the soleus muscle (31%). Mn-SOD activity was decreased in the MLN (67%) and spleen (26%) and increased in the thymus (142%), whereas catalase activity was reduced in the MLN (76%), thymus (54%) and soleus muscle (47%). It is particularly noteworthy that in ADM rats the activity of glutathione peroxidase was not detectable by the method used. These data are consistent with the possibility that epinephrine might play a role in the oxidative stress of the lymphoid organs. Whether this fact represents an important mechanism for the establishment of impaired immune function during stress remains to be elucidated.  相似文献   
135.
Outcome as a function of employment status or return to school was evaluated in severely head-injured patients. A priori we selected the most salient demographic, physiological, neuropsychological and psychosocial outcome predictors with the aim of identifying which of there variables captured at baseline or 6 months would best predict employability at 6 or 12 months. Based on the patients evaluated at 6 months, 18% of former workers had returned to gainful employment and 62% of former students had returned to school. For those not back to work or school at 6 months, 31% of the former workers and 66% of the former students had returned by 12 months. Age, length of coma, speed for both attending and motor movements, spatial integration, and intact vocabulary were all significantly related to returning to work or school. The three most potent predictors for returning to work or school were intactness of the patient's verbal intellectual power, speed of information processing and age.  相似文献   
136.
When mammalian sperm cells are exposed to solutions of albumin there are changes in the membranes of some species that resemble those that normally occur in the uterus prior to fertilization. We have shown that albumin molecules absorb on to the membranes of ejaculated rabbit sperm cells, and that the equilibrium binding constant, K, (1) varies inversely with the albumin concentration, (2) is independent of the sperm cell concentration in the range of 10(6)--10(7) per ml, (3) is independent of the time of exposure of the sperm cells to the albumin solution, and (4) decreases in the presence of Ca++ and Mg++ ions. An unusual aspect of the adsorption is that if the albumin concentration is given the symbol [A], K[A] is a constant in our measurements. This means that for virtually the entire range of [A] studied, the sperm cells bind albumin so that half of the available surface is coated and half remains uncoated. This situation is rather remarkable and it suggests a role that adsorption could play in the physical processes preceding fertilization. In purely physical systems, the optimum for the bridging and flocculation of particles that are coated with adsorbed macromolecular films occurs when half of the available surface is covered. The sperm cell appears to provide the optimal situation for interacting with itself or with another surface.  相似文献   
137.
Rats fed pellets containing locoweed developed typical microscopic lesions of locoweed poisoning. Rats fed a water extract of locoweed or urine from sheep given locoweed also developed microscopic lesions. This indicated that the locoweed toxin is water soluble and is excreted in the urine.  相似文献   
138.
139.
140.
We have examined six individuals from a two-generation Dutch family for a suspected hemoglobin (Hb) abnormality. The propositus presented with polycythemia and complained of persistent weakness, headache, and epistaxis. All family members initially showed a normal Hb-electrophoretic pattern, but on isoelectric focusing, three of them displayed a fast-moving band associated with high packed red cell volumes (PCV) and increased red blood cell count. The Hb mutant was analyzed at the DNA level by specific gene fragment amplification (PCR), followed by direct DNA sequencing, and the mutation was confirmed by restriction enzyme analysis. We found a C-->G transversion (CAC-->CAG) at codon 97 of the beta-chain, which corresponded to the His-->Gln amino acid substitution previously described as Hb Malm?. We report here the clinical history of the patient, the effects of phlebotomy treatment, and the effect of subnormal iron conditions on the erythropoietic recovery after phlebotomy. The mechanism responsible for the induction of the higher oxygen affinity is discussed, as are some aspects concerning the occurrence, pathology treatment, and the genetic risk of Hb variants with high O2 affinity.  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