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   595篇
  免费   14篇
  国内免费   7篇
电工技术   47篇
化学工业   64篇
金属工艺   10篇
机械仪表   11篇
建筑科学   9篇
矿业工程   1篇
能源动力   8篇
轻工业   29篇
水利工程   1篇
无线电   41篇
一般工业技术   62篇
冶金工业   285篇
原子能技术   5篇
自动化技术   43篇
  2023年   5篇
  2022年   5篇
  2021年   8篇
  2019年   4篇
  2018年   5篇
  2016年   4篇
  2015年   8篇
  2014年   7篇
  2013年   16篇
  2012年   25篇
  2011年   19篇
  2010年   10篇
  2009年   17篇
  2008年   12篇
  2007年   17篇
  2006年   9篇
  2005年   13篇
  2004年   4篇
  2003年   8篇
  2002年   5篇
  2001年   7篇
  2000年   7篇
  1999年   22篇
  1998年   101篇
  1997年   60篇
  1996年   44篇
  1995年   19篇
  1994年   11篇
  1993年   17篇
  1991年   6篇
  1990年   5篇
  1989年   3篇
  1988年   4篇
  1987年   4篇
  1986年   5篇
  1985年   7篇
  1984年   3篇
  1983年   4篇
  1982年   3篇
  1981年   7篇
  1980年   5篇
  1979年   4篇
  1977年   4篇
  1976年   23篇
  1970年   4篇
  1930年   4篇
  1912年   2篇
  1911年   2篇
  1909年   3篇
  1903年   2篇
排序方式: 共有616条查询结果,搜索用时 31 毫秒
71.
72.
The ongoing NCCAM-supported experimental and clinical translational approaches should shed light not only on the physiologic mechanisms underlying the benefits of massage therapy but could also, if successful in defined populations of patients, have a substantial impact by providing a simpler, more cost-effective LE treatment alternative worldwide.  相似文献   
73.
A-131701 (3-[2-((3aR,9bR)-cis-6-methoxy-2,3,3a,4,5,9b, hexahydro-[1H]-benz[e]isoindol-2-yl)ethyl]pyrido [3',4': 4,5]thieno[3,2-d]pyrimidine-2,4(1H,3H)-dione) is a novel compound previously shown to be selective for alpha-1a sites compared with alpha-1b adrenoceptors in radioligand binding studies and isolated tissue bioassays and to block canine urethral pressure (IUP) responses to exogenous alpha-1 adrenergic agonists to a greater extent than blood pressure responses. In conscious dogs in which IUP and mean arterial blood pressure (MABP) responses were measured periodically up to 24 hr, A-131701 blocked phenylephrine (PHE)-induced increases in IUP to a greater extent than MABP responses, and the blockade of the IUP effects of PHE was significantly different from control for up to 12 hr after doses greater than 0.3 mg/kg p.o., whereas blood pressure effects were of a lesser extent and duration. In addition to the weak antagonism of PHE-induced blood pressure responses, A-131701 also exhibited minimal effects on basal blood pressure in the dog, unlike terazosin, doxazosin or tamsulosin. Pharmacokinetic analysis of plasma samples from dogs indicated that A-131701 had a half-life of 0.4 to 0.8 hr and a bioavailability of 30 to 50% in dogs. Somewhat longer half-lives were observed in rat and monkey, with bioavailability values in the 25 to 30% range. Evidence of nonlinearity of pharmacokinetics was obtained in dogs and monkeys. Pharmacodynamic analysis revealed differences between A-131701 and nonselective alpha-1 adrenoceptor antagonists in selectivity for prostatic versus vascular alpha-1 adrenoceptors based on either extent or duration of blockade, which were either similar to or superior to compounds such as tamsulosin or REC 15/2739. These data demonstrate that A-131701 selectively blocks canine prostatic alpha-1 adrenoceptors for prolonged periods compared with MABP responses in vivo. Therefore, A-131701 should have clinical utility in the pharmacotherapy of benign prostatic hyperplasia.  相似文献   
74.
75.
A software package is described which is used by six universities in the Netherlands for Computer Managed Instruction. Special attention is given to the structuring and implementation of courses and blocks in a course. The facilities provided for guiding students through a course and for evaluation will also be discussed.  相似文献   
76.
There is an early period of puberty in boys at the age of 10 to 13, accompanied by an increase in the level of follicle stimulating hormone and a low secretion of luteinizing hormone and testosterone, with no secondary sexual signs. The beginning of an increase in the luteinizing hormone and testosterone concentration in boys coincides with the development of secondary sexual signs. The stabilization of the level of luteinizing hormone takes place in boys already at the 2nd degree of the sexual development. The secretion of luteinizing hormone at this point corresponds already to the normal level in adult men. The level of testosterone in the blood continues to increase and does not reach its definitive level until after the age of 17, or at the 5th degree of sexual development. Like in boys, the increase of the follicle stimulating hormone in girls precedes the increase of the luteinizing hormone secretion. The beginning of the increase in the follicle stimulating hormone coincides with an increase in the level of estrogens and testosterone in the blood, and with the appearance of secondary signs of sexual maturation. The increase of the luteinizing hormone secretion takes place later in girls than in boys and is accompanied by a new and significant increase in the level of estrogens in the blood. At the 2nd degree of sexual development, the level of testosterone in the blood of girls is substantially higher than at the other stages.  相似文献   
77.
78.
79.
The T lineage repertoire is shaped by T cell receptor (TCR)-dependent positive and negative thymic selection processes. Using TCR-transgenic (N15tg) beta2-microglobulin-deficient (beta2m-/-) RAG-2(-/-) H-2(b) mice specific for the VSV8 (RGYVYQGL) octapeptide bound to Kb, we identified a single weak agonist peptide variant V4L (L4) inducing phenotypic and functional T cell maturation. The cognate VSV8 peptide, in contrast, triggers negative selection. The crystal structure of L4/Kb was determined and refined to 2.1 A for comparison with the VSV8/Kb structure at similar resolution. Aside from changes on the p4 side chain of L4 and the resulting alteration of the exposed Kb Lys-66 side chain, these two structures are essentially identical. Hence, a given TCR recognizes subtle distinctions between highly related ligands, resulting in dramatically different selection outcomes. Based on these finding and the recent structural elucidation of the N15-VSV8/Kb complex, moreover, it appears that the germ-line Valpha repertoire contributes in a significant way to positive selection.  相似文献   
80.
For the non-invasive measurement of the oxygen saturation in human retinal vessels, the light reflected by a vessel and its surroundings is evaluated. Differences in the absorption and scattering properties of the optical media provide so-called vessel profiles, but the central vessel section is often disturbed by a regular reflex. In order to eliminate this reflex, a method based on the Hilbert transform is presented, which can be used for the determination of logarithmic differences between the reflected light on and that beside the vessel. The data for our investigations were produced by simulation of the radiation transport in multi-layered tissue. A linear regression between expected and measured values based on 40 pairs was used for the evaluation of the proposed method. A linear relationship was shown to exist.  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