全文获取类型
收费全文 | 412944篇 |
免费 | 5822篇 |
国内免费 | 1386篇 |
专业分类
电工技术 | 7717篇 |
综合类 | 350篇 |
化学工业 | 62037篇 |
金属工艺 | 14291篇 |
机械仪表 | 11873篇 |
建筑科学 | 11640篇 |
矿业工程 | 869篇 |
能源动力 | 11126篇 |
轻工业 | 43811篇 |
水利工程 | 3312篇 |
石油天然气 | 1836篇 |
武器工业 | 13篇 |
无线电 | 55409篇 |
一般工业技术 | 76685篇 |
冶金工业 | 74967篇 |
原子能技术 | 5568篇 |
自动化技术 | 38648篇 |
出版年
2021年 | 2672篇 |
2019年 | 2435篇 |
2018年 | 3842篇 |
2017年 | 3906篇 |
2016年 | 4150篇 |
2015年 | 3431篇 |
2014年 | 5721篇 |
2013年 | 19295篇 |
2012年 | 10214篇 |
2011年 | 14690篇 |
2010年 | 11296篇 |
2009年 | 12891篇 |
2008年 | 13922篇 |
2007年 | 14295篇 |
2006年 | 12785篇 |
2005年 | 11967篇 |
2004年 | 11581篇 |
2003年 | 11283篇 |
2002年 | 10920篇 |
2001年 | 11135篇 |
2000年 | 10274篇 |
1999年 | 10772篇 |
1998年 | 24015篇 |
1997年 | 17592篇 |
1996年 | 13909篇 |
1995年 | 10986篇 |
1994年 | 9779篇 |
1993年 | 9359篇 |
1992年 | 7121篇 |
1991年 | 6790篇 |
1990年 | 6400篇 |
1989年 | 6106篇 |
1988年 | 5861篇 |
1987年 | 4884篇 |
1986年 | 4834篇 |
1985年 | 5981篇 |
1984年 | 5605篇 |
1983年 | 4832篇 |
1982年 | 4506篇 |
1981年 | 4448篇 |
1980年 | 4208篇 |
1979年 | 4080篇 |
1978年 | 3771篇 |
1977年 | 4548篇 |
1976年 | 6100篇 |
1975年 | 3115篇 |
1974年 | 3011篇 |
1973年 | 2890篇 |
1972年 | 2318篇 |
1971年 | 2005篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
S Murakami T Igarashi T Yuhiki T Tobe K Mikami S Akimoto J Shimazaki O Matsuzaki 《Canadian Metallurgical Quarterly》1994,85(8):1213-1217
In order to evaluate the significance of repeat transurethral resection (TUR) in differentiating stage A1 prostatic adenocarcinoma from those with stage A2, we performed repeat TUR in 34 patients with an initial diagnosis of stage A1 prostatic adenocarcinoma. It was found that residual adenocarcinoma was present in five cases (14.7%), but the diagnosis was changed from stage A1 to stage A2 in only one case (2.9%). In one patient with final diagnosis of stage A1 carcinoma, bone metastases were detected seven months after the repeat TUR. It was concluded that repeat TUR for stage A1 prostatic adenocarcinoma did not yield clinically significant information. 相似文献
962.
963.
The main maturation stages of Norway rat megakaryocytic series, megakaryoblasts and mature megakaryocytes, stained by silver for demonstration of argyrophil nucleolus organizer regions (AgNORs) were investigated to provide basic information on the number of nucleoli and interphasic AgNORs in these cells. The results showed that megakaryoblasts as well as mature megakaryocytes possess numerous nucleoli; their number and also the number of AgNORs is significantly higher in less mature than in more mature cells. The number of AgNORs in megakaryocytes of the Norway rat and man are virtually the same, although the numbers of nucleolar organizers per haploid chromosome set differ markedly. This fact leads to the conclusion that the number of interphasic AgNORs depends on the function and metabolic state of the cell rather than on the number of nucleolar organizers. 相似文献
964.
965.
Summary The dynamic interaction of an elastically supported rigid cylinder and a surrounding incompressible fluid in a coaxial cylindrical duct is studied. Attention is focussed on a fluid of low viscosity so that conventional approaches lead to uncertain results. Here a singular perturbation analysis is performed which overcomes the difficulties. As a quantitative result, the complex-valued eigenvalue of the vibrating body in the fluid is computed. 相似文献
966.
A Guhlmann K Krauss F Oberdorfer T Siegel PH Scheuber J Müller B Csuk-Gl?nzer S Ziegler H Ostertag D Keppler 《Canadian Metallurgical Quarterly》1995,21(6):1568-1575
N-Acetyl-leukotriene E4 has been identified as an endogenous, biologically less active cysteinyl leukotriene metabolite in rodents and humans. To evaluate the ratio of hepatobiliary to renal elimination of leukotrienes noninvasively by positron emission tomography (PET), we synthesized N-[11C]acetyl-leukotriene E4 by chemical N-acetylation of leukotriene E4. After the intravenous injection of N-[11C]acetyl-leukotriene E4 in normal rats and monkey, uptake by the liver and subsequent excretion into bile were largely responsible for its rapid elimination from blood. In the Cynomolgus monkey, renal excretion of the leukotriene into urine was of additional quantitative importance. Kinetic modeling indicated a mean transit time through the liver of 17 minutes and 34 minutes in rat and monkey, respectively; the corresponding hepatic excretion half-times amounted to 8.5 minutes and 16 minutes. In a mutant rat strain deficient in the hepatobiliary excretion of cysteinyl leukotrienes across the canalicular membrane, the apparent mean liver transit time was 54 minutes, and the hepatic excretion half-time was 29 minutes, indicating prolonged organ storage and metabolism. After transport from the liver back into the circulating blood of omega-oxidized and beta-oxidized metabolites of N-[11C]acetyl-leukotriene E4, renal excretion compensated for the impairment of hepatobiliary elimination in the transport mutant. Metabolite analyses in urine after intravenous injection of N-[3H]acetyl-leukotriene E4 indicated the extensive inactivation of N-acetyl-leukotriene E4 by beta-oxidation from the omega-end in the mutants. A similar shift from hepatobiliary to renal cysteinyl leukotriene elimination was monitored in rats with cholestasis due to bile duct obstruction.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
967.
The first VLSI digital signal processor that performs both high-precision image backprojection and spatial histogram calculations at raster-scan rates as high as 30 MHz is described. Realized in 1 μm CMOS technology, this 13.3 mm×13.3 mm chip is designed to handle images as large as 1024×1024 12 b pixels. Loadable coefficients and a unified architecture allow this IC to be used with a variety of computed-tomography scanners for image reconstructions, including fan- and parallel-beam reconstruction. This chip also computes the forward Radon transform, which is a spatial histogram, permitting it to be used for iterative reconstruction algorithms. The bit lengths in the fixed-point architecture assure 12 b reconstruction accuracy 相似文献
968.
AC Fluckiger P Garrone I Durand JP Galizzi J Banchereau 《Canadian Metallurgical Quarterly》1993,178(5):1473-1481
Interleukin 10 (IL-10) has recently been shown to induce normal human B lymphocytes to proliferate and differentiate into immunoglobulin (Ig)-secreting cells. Herein, we show that IL-10 also promotes DNA synthesis and IgM production by anti-CD40 activated B cell chronic lymphocytic leukemia (B-CLL). Most strikingly, IL-2 and IL-10 were found to synergize to induce the proliferation and differentiation of B-CLL cells. This synergy between IL-2 and IL-10 was also observed with normal B cells which proliferated strongly and secreted large amounts of IgM, IgG, and IgA. The observed synergy is likely to be due to the IL-10-induced increase of high affinity IL-2 receptors on both normal and leukemic B cells. This increase of high affinity receptor is associated to an increase of Tac/CD25 expression that can be detected by flow cytometric analysis. Taken together, these results indicate that IL-10 permits anti-CD40 activated B cells to respond to IL-2 through an induction of high affinity IL-2 receptors. This effect of IL-10 may partly explain how T cells, which activate B cells in a CD40-dependent fashion, induce B cell proliferation and differentiation mostly through IL-2. 相似文献
969.
970.
JM Vaugeois JJ Bonnet D Duterte-Boucher J Costentin 《Canadian Metallurgical Quarterly》1993,230(2):195-201
We have recently found that allogenic bone marrow transplantation (BMT) can be used to treat lupus nephritis in NZB x NZW F1 (B/W F1) and BXSB mice. To elucidate why and how glomerular damage is repaired, serial renal biopsies were carried out using B/W F1 mice before, and after BMT. Donor-derived B cells and macrophages with normal functions developed two weeks after BMT, whereas donor-derived functional T cells were generated after seven weeks of BMT. Visceral epithelial cells as well as macrophages in the glomeruli were activated (probably by T cell-derived lymphokines) at this time; they showed marked phagocytic activity, resulting in clearance of immune complexes (ICs) and repair of damaged basement membranes. These results suggest that normal T cell functions, which have the capacity to activate macrophages and epithelial cells, are essential in repairing IC-mediated glomerular damage. 相似文献