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   6309篇
  免费   1篇
综合类   1篇
化学工业   23篇
机械仪表   1篇
建筑科学   1篇
轻工业   1篇
石油天然气   1篇
无线电   2篇
一般工业技术   6篇
冶金工业   6270篇
自动化技术   4篇
  2019年   1篇
  2015年   2篇
  2013年   2篇
  2010年   1篇
  2009年   1篇
  2007年   1篇
  2006年   1篇
  2005年   2篇
  2004年   3篇
  2003年   17篇
  2002年   1篇
  2001年   1篇
  2000年   1篇
  1999年   203篇
  1998年   1992篇
  1997年   1085篇
  1996年   782篇
  1995年   402篇
  1994年   334篇
  1993年   365篇
  1992年   41篇
  1991年   87篇
  1990年   50篇
  1989年   68篇
  1988年   64篇
  1987年   65篇
  1986年   67篇
  1985年   48篇
  1983年   6篇
  1982年   24篇
  1981年   38篇
  1980年   63篇
  1979年   6篇
  1978年   16篇
  1977年   135篇
  1976年   316篇
  1975年   11篇
  1973年   1篇
  1955年   6篇
  1954年   1篇
排序方式: 共有6310条查询结果,搜索用时 0 毫秒
101.
102.
Susceptibility of C57BL/6 (Bcgs) and C3H/HeN (Bcgr) mice to an intraperitoneal infection with Mycobacterium paratuberculosis strain 19698 was compared (by histopathology and the number of mycobacteria isolated from the spleen). Mycobacterial counts from the spleen of Bcgr mice progressively decreased over the course of infection but remained unchanged in Bcgs mice. Granulomatous lesions and acid-fast bacteria were consistently present in the liver and lymph nodes of Bcgs mice, whereas lesions were transient or absent in Bcgr mice. These results indicate that Bcgr mice are inherently resistant to M. paratuberculosis, whereas Bcgs mice are inherently susceptible. These differences may prove useful in elucidating the mechanisms of resistance and susceptibility to paratuberculosis and other mycobacterial infections.  相似文献   
103.
The crystal structure of the peptide Boc-Phe-Val-OMe determined by X-ray diffraction methods is reported in this paper. The crystals grown from aqueous methanol are orthorhombic, space group P2(1)2(1)2(1),a = 11.843(2), b = 21.493(4), c = 26.676(4) A3 and V = 6790 A3. Data were collected on a CAD4 diffractometer using MoK alpha radiation (lambda = 0.7107 A) up to Bragg angle theta = 26 degrees. The structure was solved by direct methods and refined by a least-squares procedure to an R value of 6.8% for 3288 observed reflections. There are three crystal-lographically independent peptide molecules in the asymmetric unit. All the three molecules exhibit extended conformation. The sidechain of the Val2 residue shows two different conformations. The conformation of the peptide Boc-Phe-Val-OMe is compared with the conformation of Ac-delta Phe-Val-OH. It is observed that while Boc-Phe-Val-OMe exhibits an extended conformation, Ac-delta Phe-Val-OH shows a folded conformation. The results of this comparison highlight the conformation constraining property of the delta Phe residue. Interestingly, even though Boc-Phe-Val-OMe and Ac-delta Phe-Val-OH are conformationally different, they exhibit similar packing patterns in the solid state.  相似文献   
104.
In response to a university mandate and general faculty dissatisfaction with work assignments, faculty developed a faculty work load formula. The authors discuss the development of the teaching portion of the formula. Implementation of the formula and publication of teaching work loads has resulted in greater awareness of other's responsibilities, improved faculty morale, increased accountability, and a greater sense of control. Some problem areas are also discussed.  相似文献   
105.
Mesenteric venous thrombosis (MVT) after appendicectomy has not been reported in the pediatric literature. This complication is associated with significant morbidity and mortality rates in adults. The report of this case attempts to analyze the features found in an appendicectomized child documented by radiological examination and surgery before and after starting heparin therapy. Anticoagulation treatment should be started as soon as possible and continued for a long time to decrease the risk of relapse.  相似文献   
106.
We investigated whether inhibition of the BCR-ABL tyrosine kinase by the CGP57418B compound would render chronic myeloid leukaemia (CML) cells susceptible to Fas (CD95, Apo-1)-mediated cell death. Only two (AR230 and SD1) out of 10 BCR-ABL positive cell lines were found to express the CD95 protein. No change in Fas expression was observed in any of the 10 cell lines after 48 h exposure to CGP57418B. AR230 cells were resistant and SD1 cells were partially resistant to Fas-mediated apoptosis induced by ligation of the Fas receptor to an anti-Fas IgM antibody. Pre-incubation with 1 microM CGP57418B did not change the susceptibility of these cell lines to Fas-mediated cell death. Similar results were observed in experiments with CD34+ cells from CML patients and from normal individuals. The data suggest that, in contrast to some cytotoxic drugs, the CGP57148B tyrosine kinase inhibitor utilizes a pathway other than the CD95 system in order to induce apoptosis in CML cells.  相似文献   
107.
A micellar electrokinetic capillary chromatographic (MECC) method has been developed and optimised for the separation of 5-aminolaevulinic acid (ALA) and porphobilinogen (PBG). The running buffer consisted of a mixture of 20 mM sodium phosphate and 20 mM sodium borate containing 50 mM sodium dodecyl sulphate (SDS) adjusted to pH 9.5 with 1 M NaOH. The running voltage and temperature were 20-25 kV and 30 degrees C, respectively. The MECC method for the analysis of PBG is fast and simple and is useful for the screening of PBG in the urine of patients suspected to have acute intermittent porphyria (AIP), and for the confirmation of lead exposure by measuring red-cell ALA-dehydratase (ALA-D) activity with ALA as the enzyme substrate.  相似文献   
108.
Undertreatment of all types of acute and chronic pain is common, both in the United States and around the world. Moreover, a literature review of pressure ulcer pain and its management suggests that this area of pain medicine is truly in its infancy. This article includes a discussion of current literature, anatomy and physiology of pain related to pressure and ischemic ulcers and assessment methods. It also describes treatment modalities, including conservative measures, medication management and invasive procedures. Special emphasis is placed on the use of opioid analgesics in the management of severe acute and chronic wound pain.  相似文献   
109.
Chronic myopathy is a common complication of alcoholism, but its natural history has not been well described. We, therefore, studied muscle structure and function in a 5-year study of 30 chronic alcoholics who became abstinent and 20 who relapsed, and 40 control subjects. The mean strength of the abstaining alcoholics increased from 18.6 to 23.2 kg; but, after 5 years, they were still substantially weaker than controls. In a subset who showed histological myopathy, the strength of half of the patients remained two standard deviations below that of controls. Alcoholics who relapsed tended to become progressively weaker (21.7 kg vs. 18.2 kg) and develop histological evidence of myopathy. Thus, continued alcohol abuse was generally reflected in deterioration of muscle strength and the appearance of histological injury to muscle. Importantly, almost half of the sober patients did not recover to normal levels, indicating that alcoholic myopathy is only partially reversible. We also unexpectedly found that, in some alcoholics, a substantial reduction in the amount of alcohol consumed may be as effective as complete abstinence in improving muscle strength or preventing its deterioration.  相似文献   
110.
A simple, rapid and reproducible high-performance liquid chromatographic assay for cisapride and norcisapride in human plasma is described. Samples of plasma (150 microl) were extracted using a C18 solid-phase cartridge. Regenerated tubes were eluted with 1.0 ml of methanol, dried, redissolved in 150 microl of methanol and injected. Chromatography was performed at room temperature by pumping acetonitrile-methanol-0.015 M phosphate buffer pH 2.2-2.3 (680:194:126, v/v/v) at 0.8 ml/min through a C18 reversed-phase column. Cisapride, norcisapride and internal standard were detected by absorbance at 276 nm and were eluted at 4.3, 5.3 and 8.1 min, respectively. Calibration plots in plasma were linear (r>0.998) from 10 to 150 ng/ml. Intraday precisions for cisapride and norcisapride were 3.3% and 5.4%, respectively. Interday precisions for cisapride and norcisapride were 9.6% and 9.0%, respectively. Drugs used which might be coadministered were tested for interference.  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