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   5451篇
  免费   2篇
  国内免费   1篇
电工技术   1篇
综合类   2篇
化学工业   14篇
建筑科学   7篇
轻工业   10篇
水利工程   1篇
无线电   10篇
一般工业技术   9篇
冶金工业   5384篇
自动化技术   16篇
  2017年   3篇
  2015年   1篇
  2013年   3篇
  2012年   3篇
  2011年   6篇
  2010年   2篇
  2009年   2篇
  2008年   2篇
  2007年   5篇
  2006年   7篇
  2005年   4篇
  2004年   4篇
  2003年   3篇
  2002年   1篇
  2001年   1篇
  2000年   3篇
  1999年   165篇
  1998年   1672篇
  1997年   921篇
  1996年   582篇
  1995年   334篇
  1994年   293篇
  1993年   311篇
  1992年   40篇
  1991年   61篇
  1990年   70篇
  1989年   61篇
  1988年   68篇
  1987年   69篇
  1986年   54篇
  1985年   62篇
  1984年   1篇
  1983年   10篇
  1982年   27篇
  1981年   27篇
  1980年   53篇
  1979年   3篇
  1978年   13篇
  1977年   156篇
  1976年   341篇
  1975年   3篇
  1973年   1篇
  1972年   1篇
  1969年   1篇
  1955年   4篇
排序方式: 共有5454条查询结果,搜索用时 0 毫秒
1.
2.
3.
A dynamic investigation was done of the immunologic status in 75 patients with purulent surgical lesions of soft tissues. Applied in the complex of therapeutic measures was intracorporeal irradiation of blood with ultraviolet light under control of partial pressure of oxygen and carbon dioxide. The above irradiation was found out to make for a more rapid and marked stabilization of bodily immunologic status.  相似文献   
4.
Activated ABL oncogenes cause B-cell leukemias in mice and chronic myelogenous leukemia in humans. However, the mechanism of transformation is complex and not well understood. A method to rapidly and reversibly activate c-ABL was created by fusing the extra-cytoplasmic and transmembrane domain of the erythropoietin (EPO) receptor with c-ABL (EPO R/ABL). When this chimeric receptor was expressed in Ba/F3 cells, the addition of EPO resulted in a dose-dependent activation of c-ABL tyrosine kinase and was strongly antiapoptotic and weakly mitogenic. To evaluate the contributions of various ABL domains to biochemical signaling and biological effects, chimeric receptors were constructed in which the ABL SH3 domain was deleted (triangle upSH3), the SH2 domain was deleted (triangle upSH2), the C-terminal actin-binding domain was deleted (triangle upABD), or kinase activity was eliminated by a point mutation, K290M (KD). The mutant receptors were stably expressed in Ba/F3 cells and analyzed for signaling defects, proliferation, viability, and EPO-induced leukemia in nude mice. When compared with the ability of the full-length EPO R/ABL receptor to induce proliferation and support viability in vitro, the triangle upSH3 mutant was equivalent, the triangle upSH2 mutant was moderately impaired, and the triangle upABD and KD mutants were profoundly impaired. None of these cell lines caused leukemia in mice in the absence of pharmacological doses of EPO. However, in mice treated with EPO (10 U/d), death from leukemia occurred rapidly with wild-type and triangle upSH3. However, time to death was prolonged by at least twofold for triangle upSH2 and greater than threefold for triangle upABD. This inducible model of ABL transformation provides a method to link specific signaling defects with specific biological defects and has shown an important role for the C-terminal actin-binding domain in proliferation and transformation in the context of this receptor/oncogene.  相似文献   
5.
6.
7.
Until recently, an HIV test was of limited importance for persons who had been at risk for HIV as effective drugs were not available. With the advent of a new generation of antiretroviral drugs with beneficial effect after early treatment, knowledge of the HIV serostatus has become of more importance to asymptomatic persons. There is no need for a mass screening campaign however, as there is no cure as yet.  相似文献   
8.
The EIR1 gene of Arabidopsis is a member of a family of plant genes with similarities to bacterial membrane transporters. This gene is expressed only in the root, which is consistent with the phenotypes of the eir1 mutants-the roots are agravitropic and have a reduced sensitivity to ethylene. The roots of eir1 mutants are also insensitive to the excess auxin produced by alf1-1 and fail to induce an auxin-inducible gene in the expansion zone. Although they fail to respond to internally generated auxin, they respond normally to externally applied auxin. Expression of the EIR1 gene in Saccharomyces cerevisiae confers resistance to fluorinated indolic compounds. Taken together, these data suggest that the EIR1 protein has a root-specific role in the transport of auxin.  相似文献   
9.
The Internet technology known as the World Wide Web is rapidly emerging as the most powerful medium of mass communication this century and it can be harnessed to dispense global, cost-effective, high-quality, multimedia patient education material. This paper reviews how the Internet has progressed from delivering simple static, text-based material to sophisticated interactive Web sites based on CGI Technology. Interactive Web sites can be used to deliver health assessment questionnaires and Web-based decision-support systems can give patients advice on the emergency management of acute medical problems. The advantages and drawbacks of this new technology, including information regulation and quality are discussed. The role of the Hospital Intranet as a patient education resource is described. The paper concludes by illustrating how patients can appreciate the 3-D structure of bones and organs using virtual reality in a VRML Web environment.  相似文献   
10.
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