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   578篇
  免费   0篇
化学工业   8篇
轻工业   2篇
一般工业技术   1篇
冶金工业   566篇
原子能技术   1篇
  2020年   1篇
  2013年   1篇
  2011年   1篇
  2006年   1篇
  2005年   1篇
  1999年   8篇
  1998年   141篇
  1997年   94篇
  1996年   53篇
  1995年   44篇
  1994年   31篇
  1993年   40篇
  1992年   6篇
  1991年   10篇
  1990年   7篇
  1989年   8篇
  1988年   5篇
  1987年   7篇
  1986年   8篇
  1985年   10篇
  1983年   1篇
  1982年   2篇
  1981年   5篇
  1980年   5篇
  1978年   5篇
  1977年   18篇
  1976年   59篇
  1975年   3篇
  1973年   1篇
  1964年   1篇
  1955年   1篇
排序方式: 共有578条查询结果,搜索用时 15 毫秒
11.
12.
Elastofibroma, or elastofibroma dorsi as it was first described, is an uncommon tumor-like process that characteristically appears as an ill-defined mass in the infrascapular region of elderly patients. This lesion can occur bilaterally and may appear asynchronously. The occurrence of elastofibroma in other anatomic sites has been reported, although with much less frequency. Elastofibromas display typical diagnostic histologic, cytologic, and electron microscopic features. The use of magnetic resonance imaging can lead to a presumptive diagnosis in elderly individuals with suprascapular lesions. It is important to differentiate this lesion from other soft-tissue lesions, such as sarcomas and desmoid tumors. This study presents a case of bilateral elastofibromas in a 72-year-old man and a review of the literature.  相似文献   
13.
Today, when the number of high-risk patients is increasing, special attention should be paid to polyresistant gram-positive microorganisms staphylococci and enterococci, whose role in infective complications and septic states is increasing. The author analyzes published reports on the rate of isolation of methicillin-resistant staphylococci (MRS) and enterococci in different countries and relationship of this parameter with antibiotic policy. Special attention is paid to unjustified wide use of third-generation cephalosporines and their role in selection of polyresistant bacteria. The rate of MRS isolation vs. all other staphylococci at intensive care wards for newborns is as high as 63.9%. The incidence of coagulase-negative staphylococci (most often S. epidermidis) in clinical material (blood, cerebrospinal fluid, urine) from high-risk patients increased 2-3 times during two recent years. Glycopeptides vancomycin and teicoplanine are drugs of choice for the treatment of infections caused by such microorganisms (sepsis, endocarditis, osteomyelitis, pneumonia, etc.). These drugs should be listed among obligatory antibiotics for resuscitation and intensive care wards as life-saving drugs.  相似文献   
14.
15.
Two cases of simultaneous typhoid perforation of terminal ileum and appendix are reported from Harare Central Hospital. These findings have not been reported before. Perforations were associated with schistosomiasis and HIV/AIDS. Definitive diagnosis was made only after laparotomy, serology and histopathology. With early diagnosis, effective resuscitation and timely intervention, this life-threatening condition is not necessarily fatal. Septic shock is however, an ominous sign of poor prognosis. In the tropics, bradycardia, leukopaenia and perforation in a febrile patient with right iliac fossa tenderness should arouse suspicion. Perforations may occur in patients with underlying diseases.  相似文献   
16.
17.
Salt effects on ligand-DNA binding. Minor groove binding antibiotics   总被引:4,自引:0,他引:4  
Salt dependent electrostatic effects play a central role in intermolecular interactions involving nucleic acids. In this paper, the finite-difference solution to the nonlinear Poisson-Boltzmann (NLPB) equation is used to evaluate the salt dependent contribution to the electrostatic binding free energy of the minor groove binding antibiotics DAPI, Hoechst 33258 and netropsin to DNA using detailed molecular structures of the complexes. For each of these systems, a treatment based on the NLPB equation accurately describes the variation of the experimentally observed binding constant with bulk salt concentration. A solvation formalism is developed in which salt effects are described in terms of three free energy contributions: the electrostatic ion-molecule interaction free energy, delta delta G degrees im; the electrostatic ion-ion interaction free energy, delta delta G degrees ii; and the entropic ion organization free energy, delta delta G degrees org. The electrostatic terms, delta delta G degrees im and delta delta G degrees ii, have both enthalpic and entropic components, while the term delta delta G degrees org is purely a cratic entropy. Each of these terms depends significantly on salt dependent changes in the counterion and coion concentrations around the DNA. In each of the systems studied, univalent ions substantially destabilize charged ligand-DNA complexes at physiological salt concentrations. This effect involves a salt dependent redistribution of counterions near the DNA. The free energy associated with the redistribution of counterions upon binding is dominated by the unfavorable change in the electrostatic ion-molecule interactions, delta delta G degrees im, rather than the change in the cratic entropy of ion organization, delta delta G degrees org. In addition, the observed slope of the salt dependence of the free energy is determined by electrostatic ion-molecule and ion-ion interactions as well as the cratic entropy of ion release. These findings are in contrast to models in which the cratic entropy of counterion release drives binding.  相似文献   
18.
Acute and subacute extrapyramidal movement disorders are rarely reported in uremic patients. We report three such cases with basal ganglia lesions. All three had advanced renal failure with high serum creatinine levels. One of the patients had a history of ischemic heart disease and acute pulmonary edema with hypoxemia. Another patient had experienced arterial hypotension during previous hemodialysis. The third had prominent metabolic acidosis. One of the patients developed generalized dyskinesias, whereas the other two developed gait disturbances. Neuroimaging studies in all three cases showed bilateral changes in the basal ganglia. The natural history was self-limiting with gradual improvement. Diminution of the basal ganglia lesions was demonstrated on follow-up imaging in two of the three cases. We conclude that acute or subacute movement disorders with bilateral basal ganglia lesions may occur in uremia. Hypoperfusion with global brain ischemia and selective vulnerability of the basal ganglia to uremic toxins may account for these lesions.  相似文献   
19.
20.
The hypothesis that the capability of agents to mobilize arachidonic acid (AA) could predict increased anandamide (ANA) synthesis in a macrophage cell line has been examined. Lipopolysaccharide (LPS), platelet-activating factor (PAF) and cannabinoids such as Delta9-tetrahydrocannabinol (THC) and anandamide were all found to be agonists for the release of AA and led to increased ANA synthesis in RAW264.7 mouse macrophage cells. Nitric oxide, in contrast, stimulated AA release without raising ANA levels. ANA stimulation of its own synthesis indicates the existence of a positive feedback mechanism. The possible involvement of the CB2 receptor in THC-mediated AA release and ANA synthesis is addressed using the antagonist SR144528. ANA synthesis is also increased by the combination of calcium ionophore and indomethacin, suggesting that ANA is metabolized by a cyclooxygenase in this system. The data imply that ANA could play a role in the response of the immune system to cannabinoids and bacterial endotoxins and that AA mobilization is a predictor for increased ANA synthesis.  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