全文获取类型
收费全文 | 18559篇 |
免费 | 2214篇 |
国内免费 | 1736篇 |
专业分类
电工技术 | 910篇 |
综合类 | 1065篇 |
化学工业 | 5129篇 |
金属工艺 | 1588篇 |
机械仪表 | 965篇 |
建筑科学 | 655篇 |
矿业工程 | 392篇 |
能源动力 | 774篇 |
轻工业 | 1459篇 |
水利工程 | 214篇 |
石油天然气 | 1132篇 |
武器工业 | 51篇 |
无线电 | 2204篇 |
一般工业技术 | 3513篇 |
冶金工业 | 811篇 |
原子能技术 | 1314篇 |
自动化技术 | 333篇 |
出版年
2024年 | 73篇 |
2023年 | 315篇 |
2022年 | 531篇 |
2021年 | 660篇 |
2020年 | 770篇 |
2019年 | 768篇 |
2018年 | 754篇 |
2017年 | 822篇 |
2016年 | 777篇 |
2015年 | 704篇 |
2014年 | 984篇 |
2013年 | 1079篇 |
2012年 | 1260篇 |
2011年 | 1335篇 |
2010年 | 935篇 |
2009年 | 957篇 |
2008年 | 864篇 |
2007年 | 1120篇 |
2006年 | 1085篇 |
2005年 | 915篇 |
2004年 | 840篇 |
2003年 | 765篇 |
2002年 | 649篇 |
2001年 | 591篇 |
2000年 | 506篇 |
1999年 | 371篇 |
1998年 | 290篇 |
1997年 | 243篇 |
1996年 | 251篇 |
1995年 | 205篇 |
1994年 | 207篇 |
1993年 | 137篇 |
1992年 | 146篇 |
1991年 | 109篇 |
1990年 | 96篇 |
1989年 | 71篇 |
1988年 | 68篇 |
1987年 | 47篇 |
1986年 | 58篇 |
1985年 | 35篇 |
1984年 | 31篇 |
1983年 | 15篇 |
1982年 | 17篇 |
1981年 | 19篇 |
1980年 | 9篇 |
1979年 | 2篇 |
1978年 | 7篇 |
1974年 | 4篇 |
1959年 | 4篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
四川盆地中部上三叠统香溪群岩性油气藏圈闭类型及其特征 总被引:4,自引:0,他引:4
四川盆地川中地区构造平缓,大型断裂欠发育,已发现的油气藏与背斜关系并不十分密切。研究认为,川中地区香溪群主要发育岩性圈闭,根据圈闭形成主控因素,结合香溪群沉积前的古地貌特征和裂缝发育特点,将川中香溪群岩性圈闭划分为4种类型:①与地层尖灭相关的地层—岩性圈闭;②与沉积—成岩相变密切相关的成岩—岩性圈闭;③与古地貌有关的差异压实作用形成的岩性圈闭;④与断层转化调节相关的裂缝—岩性复合圈闭。其中成岩—岩性圈闭和地层—岩性圈闭,是川中香溪群最重要的、分布最广泛的圈闭类型。 相似文献
103.
在分析负离子净化空气的原理及环境状况与空气中负离子浓度的关系基础上,应用负离子功能粘胶长丝和涤纶短纤混纺纱针织物作为空调滤材,利用空调出风(冷风)使针织物滤材试样飘动,相互拍击摩擦,使空调出风中的氧气分子和水分发生有效电离,从而产生大量空气负离子。实验结果表明,负离子功能粘胶长丝和涤纶短纤混纺纱针织物都有释放空气负离子的功能;而且在同规格纱线的平针组织、双罗纹组织、蜂巢组织和畦编组织针织物中,畦编组织针织物释放的负离子量最大;空气相对湿度对功能材料释放负离子数量有明显影响,当相对湿度在65%~70%时释放的负离子量趋于最大。 相似文献
104.
Poly(vinylbenzyltrimethylammonium chloride)‐graft‐cotton cellulose, an anion‐exchange matrix, was synthesized by a mutual radiation‐induced grafting technique with a 60Co γ‐radiation source. The grafted matrix was characterized by grafting yield estimation, elemental analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy. The grafting yield decreased with the increase in the dose rate. However, the grafting yield and nitrogen content of grafted samples increased almost linearly with an increase in the total irradiation dose. To evaluate the performance of the grafted anion‐exchange matrix, the protein adsorption and elution behavior were investigated in a continuous column process under various experimental conditions, with bovine serum albumin used as a model protein. The binding and elution behavior of the anion‐exchange matrix depended on different experimental parameters, such as the grafting yield, ionic strength, pH of the medium, and amount of protein loaded. From a breakthrough curve, the equilibrium binding capacity and elution percentage of the grafted anion‐exchange matrix were estimated to be 40 mg/g and 94%, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5512–5521, 2006 相似文献
105.
In order to study the influence of cerium ion implantation on the aqueous corrosion behavior of zircaloy-4, specimens were implanted by cerium ions with a fluence range from 1×1016 to 1×1017 ions/cm2 at maximum 150°C, using MEVVA source at an extracted voltage of 40 kV. The valence and elements penetration distribution of the surface layer were analyzed by X-ray photoelectron spectroscopy (XPS) and auger electron spectroscopy (AES) respectively. Glancing angle X-ray diffraction (GAXRD) was employed to examine the phase transformation due to the cerium ion implantation in the oxide films. Three-sweep potentiodynamic polarization measurement was employed to value the aqueous corrosion resistance of zircaloy-4 in a 1 N H2SO4 solution. It was found that a significant improvement in the aqueous corrosion behavior of zircaloy-4 implanted with cerium ions compared with that of the as-received zircaloy-4. The improvement effect will declined with raising the implantation fluence. The bigger is the fluence, the less is the improvement. Finally, the mechanism of the corrosion behavior of the cerium-implanted zircaloy-4 is discussed. 相似文献
106.
尽管当前有许多维护网络安全的策略,但是局域网内部通讯安全却往往被忽略,文章首先分析当前一些安全策略在维护局域网内部通讯安全的不足,然后提出一种具有加密功能的以太网网卡,用以解决局域网内部通讯的安全问题。 相似文献
107.
Co^3+—modified Surface of LiMn2O4 Spinel for its Improvementof Electrochemical Properties 总被引:3,自引:0,他引:3
ZishanZHENG ZilongTANG ZhongtaiZHANG JunbiaoLU WanciSHEN 《材料科学技术学报》2003,19(4):359-362
Cobalt was used to modify the surface of spinel LiMn2O4 by a solution technique to produce Co^3 -modified surface material (COMSM). Cobalt was only doped into the surface of LiMn2O4 spinel. XPS(X-ray photoelectron spectroscopy) analysis confirms the valence state of Co^3 . COMSM has stable spinel structure and can prevent active materials from the corrosion of electrolyte. The ICP(inductively coupled plasma) determination of the spinel dissolution in electrolyte showed the content of Mn dissolved from COMSM was smaller than that from the pure spinel. AC impedance patterns show that the charge-transfer resistance (Rct) for COMSM is smaller than that for pure spinel. The particles of COMSM are bigger in size than those of pure spinel according to the micrographs of SEM(scanning electron microscopy). The determinations of the electrochemical characterization show that COMSM has both good cycling performance and high initial capacity of 124.1 mA/h at an average capacity loss of 0.19 mAh/g per cycle. 相似文献
108.
109.
A novel elastic polymer containing 4,4′-bipyridinium salts with tetrakis[3,5-bis(trifluoromethyl)phenyl]borate as part of the main chain was synthesized. The cast film showed persistent and reversible colour changes due to photoinduced electron transfer upon excitation of an ion-pair charge-transfer band (ex >365 nm) in vacuo. The lifetime of the coloured state markedly depended on temperature. The optically written data were stored without decay below 0°C and were erased thermally at elevated temperatures. The colour changes were reversibly repeatable for many times. 相似文献
110.
油气沉积学原理及其在勘探开发中的应用 总被引:2,自引:0,他引:2
本文以油气藏形成条件中的生、储、盖、运、圈为纲讨论了油气勘探沉积学;以油气藏开发过程中与沉积、成岩的关系讨论了油气开发沉积学。在油气勘探沉积学中重点论述了陆相沉积与储层及圈闭的关系;在油气开发沉积学中重点论述了储层研究的基础—储层的沉积属性和成岩特征。强调储层沉积、成岩研究应成为储层评价最重要的内容。 相似文献