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   474篇
  免费   0篇
  国内免费   1篇
化学工业   4篇
轻工业   4篇
石油天然气   1篇
无线电   1篇
一般工业技术   1篇
冶金工业   461篇
原子能技术   1篇
自动化技术   2篇
  2011年   2篇
  2010年   1篇
  2009年   1篇
  2005年   2篇
  2004年   2篇
  2003年   2篇
  2000年   2篇
  1999年   12篇
  1998年   123篇
  1997年   76篇
  1996年   40篇
  1995年   27篇
  1994年   23篇
  1993年   33篇
  1992年   4篇
  1991年   11篇
  1990年   12篇
  1989年   9篇
  1988年   7篇
  1987年   6篇
  1986年   12篇
  1985年   7篇
  1983年   2篇
  1982年   2篇
  1981年   3篇
  1980年   3篇
  1979年   2篇
  1978年   1篇
  1977年   15篇
  1976年   30篇
  1975年   2篇
  1974年   1篇
排序方式: 共有475条查询结果,搜索用时 15 毫秒
41.
We describe a patient with Hirschsprung disease and autism. High-resolution karyotyping indicated that the patient has an interstitial deletion of 20p11.22-p11.23. Microsatellite analysis showed a deletion involving a 5-6 cM region from the maternally derived chromosome 20. The deleted region is proximal to, and does not overlap, the recently characterized Alagille syndrome region. This region of 20p has not yet been implicated in Hirschsprung disease or autism. However, this region contains several genes that could plausibly contribute to any phenotype that includes abnormal neural development.  相似文献   
42.
43.
The fibrinolytic process in the plasma of patients operated for abdominal haemorrhages have been investigated. The results allowed to conclude that the blockade of fibrinolysis did not effect on the course of the disease. The high level of the inhibitors and of the platelets hypoaggregation can be considered as a cause increased of the recurring gastrointestinal haemorrhages. It was demonstrated that the probability of DIC-syndrome development increased at the aggravation of the patient's state after the operation.  相似文献   
44.
The purpose of this study was to determine whether a brace designed to unload varus degenerative knees actually alters medial compartment loads by decreasing the adduction moment. Eleven patients who had arthrosis confined to the medial compartment were fitted with a valgus brace and tested before and after brace wear with pain and function scoring instruments and by automated gait analysis. The biomechanical data from these patients were compared with those from 11 healthy control subjects. Scores from an analog pain scale decreased 48% with brace wear, and function with activities of daily living increased 79%. Mean adduction moment without the brace measured 4.0 +/- 0.8% body weight times height versus 3.6 +/- 0.8% body weight times height when wearing the brace (10% decrease). The mean adduction moment for control subjects was 3.5 +/- 0.6% body weight times height. Thus, the mean adduction moment decreased from approximately one standard deviation from the normal mean to a value that is similar to the control value. Nine of 11 patients had a decrease in the adduction moment with the brace, five of 11 patients had a reduction higher than 10%, and decreases in this moment were as high as 32%. This study shows that pain, function, and biomechanical knee loading can be altered by a brace designed to unload the medial compartment of the knee.  相似文献   
45.
Middiaphyseal 2.5-cm segmental defects in the right femurs of 12 sheep were stabilized with stainless steel plates and implanted with (1) 2 mg recombinant human bone morphogenetic protein 2 and poly[D,L-(lactide-co-glycolide)] bioerodible polymer with autologous blood (n = 7), (2) 4 mg recombinant human bone morphogenetic protein 2 and poly[D,L-(lactide-co-glycolide)] and blood (n = 3), or (3) poly[D,L-(lactide-co-glycolide)] and blood only (n = 2). Bone healing was evaluated for 1 year using clinical, radiographic, gross pathologic, and histologic techniques. Union occurred in three sheep in Group 1, two in Group 2, and none in Group 3. In the animals that healed, new bone first was visible radiographically between Weeks 2 and 6 after implantation; new bone mineral content equaled that of the intact femur not surgically treated by Week 16; recanalization of the medullary cavity approached completion at Week 52; and at necropsy the surgical treated femurs were rigidly healed, the poly[D,L-(lactide-co-glycolide)] was resorbed completely, and woven and lamellar bone bridged the defect site. In two Group 1 sheep euthanized at Weeks 2 and 6, polymer particles were permeated by occasional multinucleated giant cells. Some plasma cells, lymphocytes, and neutrophils were present locally. The poly[D,L-(lactide-co-glycolide)] tended to fragment during surgical implantation. Despite these observations, the recombinant human bone morphogenetic protein 2/poly[D,L-(lactide-co-glycolide)] implant was able to heal large segmental bone defects in this demanding model.  相似文献   
46.
47.
Common molecular and cellular targets for alkaloids sanguinarine and ellipticine, isolated from well-known antitumor plants (as well as from their various natural and synthetic derivatives), have been studied and described. Sanguinarine and ellipticine are characterized by significant biological activities including a high antitumor potential. Among the important targets of their action the following are to be noted. 1. DNA and other double helical polynucleotides. Due to the ability of DNA-intercalation sanguinarine, ellipticine and some of their derivatives can modify the double helical structures and topological forms of polynucleotides. The results of these modifications in intercalative complexes manifest themselves in the inhibition of numerous enzymatic reactions, dependent on the structures and topological forms of DNA and other polynucleotides. 2. ATP synthesis in mitochondria. Most of DNA-intercalators, including sanguinarine and ellipticine, belong to a group of penetrating (hydrophobic) cations, which are accumulated near the external side of inner mitochondrial membranes during the membrane energization. They neutralize negative charges, arising just as the inner mitochondrial membranes become energized. By this neutralization of membrane charges the ATP synthesis in inhibited and the oxidative phosphorylation renders to be uncoupled. All studied DNA-intercalators under certain conditions uncouple the mitochondrial oxidative phosphorylation. Apparent correlation between the agents' ability for DNA-intercalation and for mitochondrial ATP synthesis inhibition seems to be determined by the importance for both types of reactions of molecule hydrophobicity and positive charges. 3. Cholinesterase systems. Sanguinarine, ellipticine and some of their derivatives, like other DNA-intercalators studied, inhibit also the enzymatic activities of cholinesterase systems due to hydrophobicity and positive charges of their molecules. 4. Sanguinarine (and chelerythrine), are also capable of inhibiting the biological activity of SH-dependent enzymes and proteins. Due to the reactivity of iminium groups in sanguinarine and chelerythrine molecules with nucleophilic reagents, e.g. thiol groups of enzymes and other proteins, the activities of SH-enzymes and proteins are inhibited. In particular, sanguinarine and chelerythrine inhibit enzymatic activity of some SH-dependent ATPases, including membrane-bound cation-transport ATPases. The earlier accumulated experience of the application in medicine of plant saps and extracts containing these alkaloids, and of the treatment of many diseases (including benign and malignant tumors) by isolated alkaloids may be explained, to a certain extent, by the inhibition of activities of the above mentioned cellular targets. The selective toxicity of these alkaloids for the number of transformed cells can be explained in the same manner.  相似文献   
48.
Despite a growing body of evidence predominantly, but not exclusively, from Thailand suggesting that the risk of developing dengue shock syndrome (DSS) is greatest following an anamnestic dengue infection, particularly if the most recent infection was with dengue 2 virus, there continues to be debate about the justification for these claims. This report describes a five-year, prospective study in two townships (suburbs) in Yangon (Rangoon) Myanmar (Burma) in which attempts were made to confirm the data from an earlier prospective study in Thailand and to address some of the criticism of earlier studies. This investigation found the incidence of anamnestic dengue infections in DSS patients to be significantly higher than in the community from which they were drawn and a significantly higher risk of developing DSS following an anamnestic infection (particularly with dengue 2 virus) than following a primary infection with any serotype.  相似文献   
49.
50.
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