全文获取类型
收费全文 | 4201篇 |
免费 | 84篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 212篇 |
综合类 | 3篇 |
化学工业 | 857篇 |
金属工艺 | 95篇 |
机械仪表 | 98篇 |
建筑科学 | 72篇 |
矿业工程 | 1篇 |
能源动力 | 137篇 |
轻工业 | 361篇 |
水利工程 | 13篇 |
石油天然气 | 15篇 |
无线电 | 418篇 |
一般工业技术 | 674篇 |
冶金工业 | 967篇 |
原子能技术 | 100篇 |
自动化技术 | 272篇 |
出版年
2023年 | 26篇 |
2022年 | 45篇 |
2021年 | 66篇 |
2020年 | 35篇 |
2019年 | 43篇 |
2018年 | 49篇 |
2017年 | 58篇 |
2016年 | 71篇 |
2015年 | 47篇 |
2014年 | 79篇 |
2013年 | 189篇 |
2012年 | 146篇 |
2011年 | 169篇 |
2010年 | 147篇 |
2009年 | 133篇 |
2008年 | 153篇 |
2007年 | 143篇 |
2006年 | 122篇 |
2005年 | 105篇 |
2004年 | 101篇 |
2003年 | 133篇 |
2002年 | 91篇 |
2001年 | 88篇 |
2000年 | 95篇 |
1999年 | 138篇 |
1998年 | 400篇 |
1997年 | 225篇 |
1996年 | 171篇 |
1995年 | 112篇 |
1994年 | 118篇 |
1993年 | 117篇 |
1992年 | 71篇 |
1991年 | 58篇 |
1990年 | 44篇 |
1989年 | 35篇 |
1988年 | 34篇 |
1987年 | 34篇 |
1986年 | 33篇 |
1985年 | 34篇 |
1984年 | 37篇 |
1983年 | 39篇 |
1982年 | 26篇 |
1981年 | 33篇 |
1980年 | 27篇 |
1979年 | 25篇 |
1978年 | 27篇 |
1977年 | 21篇 |
1976年 | 48篇 |
1973年 | 13篇 |
1972年 | 10篇 |
排序方式: 共有4295条查询结果,搜索用时 0 毫秒
31.
T Nakagawa S Konno T Maemura K Goto Y Hayashibe T Yoshida 《Canadian Metallurgical Quarterly》1993,41(11):2245-2249
A 45-year-old woman with atrial septal defect and pulmonary hypertension was admitted for surgical repair. Cardiac catheterization data revealed pulmonary to systemic flow ratio (Qp/Qs) of 1.81, pulmonary artery pressure (PAP) of 82/30 mmHg and pulmonary vascular resistance (PVR) of 10.8 unit. Open lung biopsy was added to evaluate pulmonary vascular obstructive disease (PVOD) which was shown Heath-Edwards grade 3 PVOD. Following closure of the defect, PAP (systolic) exceeded momentarily systemic level after cardiopulmonary bypass. Prostaglandin E1 drip was remarkably effective to bring down PAP during early postoperative period. Although PAP has not been shown significant decrease on catheterization of one year after surgery, great symptomatic improvement has been achieved. 相似文献
32.
The most frequent and important symptoms in primary biliary cirrhosis (PBC) are pruritus and jaundice. In the majority, jaundice appears within one half to two years of onset of pruritus. Xanthoma, bone change and sicca syndrome are often observed. The recent increase in number of asymptomatic PBC is the result of progagation of medical examination. In the biochemical tests, elevation of the biliary enzymes, such as ALP and gamma-GTP, is characteristic, as well as, a high level of serum IgM. Serum bilirubin values are gradually raised along with the clinical course of the disease. Positive antimitochondrial antibody (AMA) is the most valuable immunological finding for the diagnosis of PBC. Anti-pyruvate dehydrogenase complex E2 component E2 has the same significance as AMA. Diagnostic criteria si shown in this paper. 相似文献
33.
34.
A.B. Dalton A. Ortiz‐Acevedo V. Zorbas E. Brunner W.M. Sampson S. Collins J.M. Razal M. MikiYoshida R.H. Baughman R.K. Draper I.H. Musselman M. Jose‐Yacaman G.R. Dieckmann 《Advanced functional materials》2004,14(12):1147-1151
Numerous applications, from molecular electronics to super‐strong composites, have been suggested for carbon nanotubes. Despite this promise, difficulty in assembling raw carbon nanotubes into functional structures is a deterrent for applications. In contrast, biological materials have evolved to self‐assemble, and the lessons of their self‐assembly can be applied to synthetic materials such as carbon nanotubes. Here we show that single‐walled carbon nanotubes, coated with a designed amphiphilic peptide, can be assembled into ordered hierarchical structures. This novel methodology offers a new route for controlling the physical properties of nanotube systems at all length scales from the nano‐ to the macroscale. Moreover, this technique is not limited to assembling carbon nanotubes, and could be modified to serve as a general procedure for controllably assembling other nanostructures into functional materials. 相似文献
35.
Persistence of the hypoglossal artery is an unusual congenital abnormality of the carotid arterial system, and the simultaneous occurrence of atheromatous disease in the internal carotid artery and persistent hypoglossal artery is even more uncommon. Carotid surgery in this situation is challenging, and the surgeon must be aware of potential inherent pitfalls. A 74-year-old woman with asymptomatic stenosis of both internal carotid and hypoglossal arteries associated with occlusion of the contralateral internal carotid artery underwent successful revascularization. The anatomy of this unusual lesion and the surgical strategies, which included cranial nerve dissection and mandibular subluxation, are reviewed. 相似文献
36.
Satohiro Yoshida Tsunehiro Tanaka Tomoko Hanada Takeshi Hiraiwa Hiroyoshi Kanai Takuzo Funabiki 《Catalysis Letters》1992,12(1-3):277-285
XANES of vanadium and niobium oxide on silica or alumina have been analyzed quantitatively by a deconvolution technique. Based on the results for reference compounds, local structures of supported vanadium and niobium species were identified. The composition was estimated from difference spectra for the samples which consisted of two kinds of species. 相似文献
37.
J. Masamoto K. Matsuzaki T. Iwaisako K. Yoshida K. Kagawa H. Nagahara 《应用聚合物科学杂志》1993,50(8):1317-1329
Conventionally, acetal homopolymer or copolymer is obtained by the polymerization of formaldehyde or trioxane, following the end-capping using acetic anhydride or unzipping of the unstable polymer end fraction. First, Asahi Chemical developed a new process to obtain an end-capped polymer during polymerization of highly purified formaldehyde using acetic anhydride as the chain-transfer agent. Use of highly purified formaldehyde and endcapping during polymerization using acetic anhydride as a chain-transfer agent or an endcapping agent will provide a simple process for manufacturing acetal homopolymer. The polymerization mechanism was confirmed by infrared spectroscopy analysis and proton NMR analysis of the polymer obtained. Second, for the acetal copolymer, purified trioxane was copolymerized with ethylene oxide in the presence of methylal, which gave an endcapped polymer with high thermal stability. Two new intermediates from the initiation reaction of the copolymerization, 1,3,5,7-tetraoxacyclononane (TOCN) and 1,3,5,7,10-pentaoxacyclododecane (POCD), were isolated and a new initiation mechanism was proposed. © 1993 John Wiley & Sons, Inc. 相似文献
38.
S Ohkawa A Yamadori K Maeda M Tabuchi Y Ohsumi E Mori T Yoshida Y Yoneda T Uehara 《Canadian Metallurgical Quarterly》1993,56(8):894-896
In right middle cerebral territory infarction a new sign, excessive closure of the right eye ipsilateral to the lesion and mild closure of the left eye on command, was noted. The excessive ipsilateral eye closure was not observed on spontaneous eye closure. 相似文献
39.
Kume T. Sawa T. Yoshida T. Sawmaura M. Sakamoto M. 《Industry Applications, IEEE Transactions on》1992,28(2):421-426
A 40000-r/min vector-controlled induction motor drive is introduced. The vector control of induction motors has been widely accepted in spindle drives of machine tools where they replace conventional DC motors because of the low maintenance requirements. Another important feature of the AC spindle drive is its high-speed capability. The magnetic encoder is most widely used as the speed detector because it is suited for use in an adverse environment. However, the magnetic encoder with high resolution and a high S/N ratio loses the output pulses at extremely high speed. In the drive system introduced, the conventional vector control is used in the low-speed range, and the vector control without the encoder is used in the high-speed range. Close transition between two modes is made without interrupting the operation 相似文献
40.
M Kojima S Nakamura Y Kurabayashi H Itoh K Yoshida S Asano T Suchi T Joshita 《Canadian Metallurgical Quarterly》1995,191(11):1072-1077
To clarify the clinicopathological significance of the suppurative lesions without an epithelioid granulomatous response (SLs without Ep) in lymph nodes and their relationship to abscess-forming granulomatous lymphadenitis (AGL) and cat scratch disease (CSD), 10 cases were assessed clinicopathologically and immunohistologically. SLs without Ep were located in the subcapsular sinus, paracortical area and medullary cords, but not in the germinal centers. The microabscesses were surrounded by collections of monocytoid B-lymphocytes (MBLs), histiocytes without epithelioid features, neutrophils, small lymphocytes and small numbers of plasma cells. The majority of the MBLs seen in the SLs without Ep were of the large cell type. The histological triad of toxoplasmic lymphadenitis, i.e., reactive follicular hyperplasia, small clusters of epithelioid cells and aggregates of MBLs, were also seen in all cases. Some of the clinical and pathological findings in our 10 cases were characteristic of CSD, i.e., (1) cat exposure before the lymphadenopathy was in four of the 10 cases, (2) occurrence in autumn and winter months in all cases, (3) typical suppurative granulomas surrounded by palisaded epithelioid cells were in four of the 10 cases, and (4) Warthin-Starry silver stain-positive bacteria were detected in seven of the 10 cases. The results of our study suggest that SLs without Ep are an early stage of CSD. 相似文献