全文获取类型
收费全文 | 13486篇 |
免费 | 1205篇 |
国内免费 | 467篇 |
专业分类
电工技术 | 742篇 |
综合类 | 554篇 |
化学工业 | 2105篇 |
金属工艺 | 560篇 |
机械仪表 | 672篇 |
建筑科学 | 788篇 |
矿业工程 | 201篇 |
能源动力 | 407篇 |
轻工业 | 1267篇 |
水利工程 | 225篇 |
石油天然气 | 372篇 |
武器工业 | 85篇 |
无线电 | 1806篇 |
一般工业技术 | 1730篇 |
冶金工业 | 1530篇 |
原子能技术 | 191篇 |
自动化技术 | 1923篇 |
出版年
2024年 | 70篇 |
2023年 | 234篇 |
2022年 | 468篇 |
2021年 | 682篇 |
2020年 | 489篇 |
2019年 | 419篇 |
2018年 | 492篇 |
2017年 | 459篇 |
2016年 | 471篇 |
2015年 | 536篇 |
2014年 | 664篇 |
2013年 | 795篇 |
2012年 | 855篇 |
2011年 | 942篇 |
2010年 | 718篇 |
2009年 | 639篇 |
2008年 | 648篇 |
2007年 | 577篇 |
2006年 | 494篇 |
2005年 | 379篇 |
2004年 | 330篇 |
2003年 | 291篇 |
2002年 | 315篇 |
2001年 | 263篇 |
2000年 | 218篇 |
1999年 | 237篇 |
1998年 | 527篇 |
1997年 | 340篇 |
1996年 | 266篇 |
1995年 | 153篇 |
1994年 | 148篇 |
1993年 | 134篇 |
1992年 | 83篇 |
1991年 | 81篇 |
1990年 | 69篇 |
1989年 | 77篇 |
1988年 | 42篇 |
1987年 | 41篇 |
1986年 | 42篇 |
1985年 | 45篇 |
1984年 | 38篇 |
1983年 | 38篇 |
1982年 | 38篇 |
1981年 | 29篇 |
1980年 | 29篇 |
1979年 | 23篇 |
1977年 | 43篇 |
1976年 | 62篇 |
1975年 | 16篇 |
1973年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
It has been proposed that the immune system can be partitioned into central and peripheral immune systems. Recently, Carneiro et al. (1996a, b) proposed a network, model incorporating B and T lymphocytes that explicitly accounts for that partition. This model however, had some limitations that are tackled here. Two main changes were introduced: the average idiotypic connectivity is now an explicit function of time based on empirical evidence; and the activation of T lymphocytes by antigen is described by a log-bell shaped dose response curve. The new model, which also accounts for the CIS and PIS distinction, shows more reasonable results since the frequencies of tolerant, immune or autoimmune responses to an antigen are now correct. The model provides a new interpretation for tolerance induction during the neonatal period, and for the adult tolerance by low or high doses of antigen. It predicts that natural tolerance for antigens available during the neonatal period can be kept indefinitely upon their removal, while tolerance induced in the adult stages is rapidly lost upon transient removal of the antigen. A semiquantitative analysis of the model provides a simple explanation for the different results in terms of the frequency at which a limited set of canonical connectivity structures emerge during ontogenesis. 相似文献
102.
103.
E Elstner M Linker-Israeli J Le T Umiel P Michl JW Said L Binderup JC Reed HP Koeffler 《Canadian Metallurgical Quarterly》1997,99(2):349-360
Patients with acute promyelocytic leukemia (APL) usually relapse after all-trans retinoic acid (RA) treatment because this therapy fails to eradicate the malignant clone. Our data showed that KH 1060 and other 20-epi vitamin D3 analogs alone were potent inhibitors of clonal growth of NB4 cells, an APL cell line (ED50, approximately 5 x 10(-11) M). The combination of KH 1060 and 9-cis-RA synergistically and irreversibly enhanced this effect. Neither KH 1060 nor 9-cis-RA (10(-6) M, 3 d) were strong inducers of differentiation of NB4 cells. However, 98% of the cells underwent differentiation to a mature phenotype with features of both granulocytes and monocytes after exposure to a combination of both compounds. Apoptosis only increased after incubation of NB4 cells with 9-cis-RA alone (28%) or with a combination of 9-cis-RA plus KH1060 (32%). Immunohistochemistry showed that the bcl-2 protein decreased from nearly 100% of the wild-type NB4 cells to 2% after incubation with a combination of KH 1060 and 9-cis-RA, and the bax protein increased from 50% of wild-type NB4 cells to 92% after culture with both analogs (5 x 10(-7) M, 3 d). Western blot analysis paralleled these results. Studies of APL cells from one untreated individual paralleled our results with NB4 cells. Taken together, the data demonstrated that nearly all of the NB4 cells can be irreversibly induced to differentiate terminally when exposed to the combination of KH 1060 and 9-cis-RA. 相似文献
104.
105.
VI Korol''kov VP Krotov V Konvertino P Le?tem EV Trambovetski? J Fanton R Krisman IuV Gordeev D Evert AM Nosovski? J Konnolli 《Canadian Metallurgical Quarterly》1998,32(3):30-37
Medical practice guidelines are being developed rapidly and advocated as a crucial component in transforming and improving the delivery of health care services. However, little is known about the ability of hospitals to institute guidelines outside of experimental settings. This article approaches guideline implementation from the viewpoint of process innovation assimilation and presents specific recommendations for organizational tactics leading to successful implementation of practice guidelines. 相似文献
106.
ZH150重油钢包烘烤装置具有点火方便,雾化好,燃烧稳定,燃烧效率高,火焰刚性好,调节性能好等优点,适合于钢包的烘烤,也可应用在基他工业炉窑中,该装置用蒸汽或压缩空气作为雾化介质,能燃用柴油,原油,重油,渣油等液体燃料,介绍了该装置的基本结构,工作原理,工作特点及设计对策,以及在生产中的应用情况。 相似文献
107.
滑坡发生与地形因子的关系是区域滑坡静态规律研究的重点,但以往的研究多注重考虑其与反映几何形态的基本地形属性因子(几何形态属性因子)之间的关系,如坡度和坡向等。首先提出一种新的基于子流域内相对位置定量描述坡位(相对位置因子)的方法,并以温州地区瓯江流域1990~2001年发生的滑坡为研究对象,使用证据权法对比滑坡发生与两种不同类型地形因子之间的关系。结果表明,相对位置因子与滑坡发生的相关性大于滑坡危险性评价经常使用的几何形态属性因子;并且滑坡大多发生在定量坡位值较低的区域,这些地区处在下游,遭受流水侵蚀的强度更大、频率更高。 相似文献
108.
109.
110.
G. Le Caër E. Bauer-Grosse A. Pianelli E. Bouzy P. Matteazzi 《Journal of Materials Science》1990,25(11):4726-4731
Most metal carbides or slicides may be synthesized at room temperature, by ball milling mixtures of elemental powders for some tens of hours with a vibratory mill. Both stable and metastable compounds containing a high density of defects can be obtained. In general, phases stable at low temperatures are synthesized. This observation allows us to confirm recent estimations for the maximum temperature (600 K) attained in these powders during mechanical alloying. Exceptions are found for some MSi2 suicides with M = titanium, iron or molybdenum for which both low- and high-temperature phases are formed. 相似文献