全文获取类型
收费全文 | 15967篇 |
免费 | 734篇 |
国内免费 | 66篇 |
专业分类
电工技术 | 229篇 |
综合类 | 28篇 |
化学工业 | 2777篇 |
金属工艺 | 250篇 |
机械仪表 | 386篇 |
建筑科学 | 959篇 |
矿业工程 | 24篇 |
能源动力 | 464篇 |
轻工业 | 1140篇 |
水利工程 | 131篇 |
石油天然气 | 53篇 |
武器工业 | 3篇 |
无线电 | 2158篇 |
一般工业技术 | 2944篇 |
冶金工业 | 2359篇 |
原子能技术 | 70篇 |
自动化技术 | 2792篇 |
出版年
2023年 | 108篇 |
2022年 | 211篇 |
2021年 | 303篇 |
2020年 | 234篇 |
2019年 | 279篇 |
2018年 | 339篇 |
2017年 | 311篇 |
2016年 | 386篇 |
2015年 | 333篇 |
2014年 | 467篇 |
2013年 | 974篇 |
2012年 | 852篇 |
2011年 | 1103篇 |
2010年 | 738篇 |
2009年 | 768篇 |
2008年 | 912篇 |
2007年 | 820篇 |
2006年 | 738篇 |
2005年 | 638篇 |
2004年 | 527篇 |
2003年 | 519篇 |
2002年 | 434篇 |
2001年 | 316篇 |
2000年 | 322篇 |
1999年 | 323篇 |
1998年 | 606篇 |
1997年 | 417篇 |
1996年 | 339篇 |
1995年 | 286篇 |
1994年 | 196篇 |
1993年 | 209篇 |
1992年 | 156篇 |
1991年 | 123篇 |
1990年 | 126篇 |
1989年 | 110篇 |
1988年 | 90篇 |
1987年 | 100篇 |
1986年 | 90篇 |
1985年 | 116篇 |
1984年 | 80篇 |
1983年 | 91篇 |
1982年 | 88篇 |
1981年 | 74篇 |
1980年 | 65篇 |
1979年 | 62篇 |
1978年 | 46篇 |
1977年 | 48篇 |
1976年 | 67篇 |
1975年 | 38篇 |
1973年 | 30篇 |
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
991.
992.
BACKGROUND: The treatment of choice for cancer of the breast are mastectomy and axillary clearance or wide excision with axillary clearance. The most common complication following such a procedure is seroma formation. Various methods have been used to prevent it. However, the use of a pressure garment in this context has not been fully evaluated in the current literature. RESULTS: In a randomised trial comparing patients with a pressure garment with those without one, we have found no improvement in post-operative drainage with the use of a pressure garment. There were more complications in the group without the pressure garment (19%) compared with those with the garment (15.7%). The only seroma occurred in those patients not using the garment. The use of the pressure garment appeared to increase the duration of use of the drain (6.8 vs 6.1 days), these differences in the two groups was not significant. One of the patients in the pressure garment group was unable to tolerate the warmth and discontinued wearing the garment in the third post-operative day. This gave a rejection rate of 5%. CONCLUSION: The use of a pressure garment does not reduce the post-operative drainage, however, the complication rate appears to be higher when the pressure garment is not being used. 相似文献
993.
994.
J Devlin D Doherty L Thomson T Wong P Donaldson B Portmann R Williams 《Canadian Metallurgical Quarterly》1998,27(4):926-933
Successful immunosuppression withdrawal should benefit the natural history of organ transplantation patients. To identify the clinical hazards of removing drug treatment and possible characteristics that predict a favorable outcome in long-term liver recipients, immunosuppression was withdrawn completely and the clinicopathological outcome documented in 18 liver recipients. Indication for transplantation, HLA matching, early rejection history, and presence of microchimerism were examined as predictors of outcome. Chimerism was determined by polymerase chain reaction-based examination for donor-specific HLA-DRB1 alleles and Y-gene-specific nucleotide sequences. At 3 years, 5 patients (28%) remained completely off immunosuppression; 12 patients (67%) experienced histological graft changes: acute rejection in 4, portal tract inflammation/hepatitis in 7, and necrosis in 1. Hepatitis B or C viral infections did not account for the nonrejection patterns. Unmasking of systemic disorders occurred. Chimerism, demonstrated in 7 patients (39%), with skin the optimal tissue, was not associated with tolerance. Parameters associated with successful drug withdrawal were transplantation for non-immune-mediated liver disorders, fewer donor-recipient HLA A, B, and DR mismatches, and a low incidence of early rejection. Immunosuppression withdrawal is a feasible option in a proportion of selected liver recipients, but identification of tolerant patients remains imprecise. 相似文献
995.
996.
Gary Tyson Matthew Farrens John Matthews Andrew R. Pleszkun 《International journal of parallel programming》1997,25(3):213-242
As processor performance continues to improve, more demands are being placed on the performance of the memory system. The
caches employed in current processor designs are very similar to those described in early cache studies. In this paper, a
detailed characterization of data cache behavior for individual load instructions is given. It will be shown that by selectively
allocating cache lines according the characteristics of individual load instructions, overall performance can be improved
for both the data cache and the memory system. This approach can improve some aspects of memory performance by as much as
60 percent on existing executables.
This work was supported by National Science Foundation Grants CCR-94-03651, CCR-92-13651, CCR-92-13627, MIP-92-57259, and
generous grants from the SUN Microsystems and Tektronix corporations. 相似文献
997.
A user model neural network for a personal news service 总被引:1,自引:0,他引:1
User modelling has been widely applied to pedantic situations, where we are attempting to infer the user's knowledge. In teaching it is important to know that the user has mastered the elementary concepts before proceeding with the advanced topics. However, the application of user modelling to information retrieval demands a quite different type of user model. Here we construct a user model for browsing, where the user is uncertain of exactly which information he desires. This requires a more inexact and robust user model, that can quickly give guidance to the system. We propose a user model based on neural networks that can be constructed incrementally. Performance of the model shows some promise for this approach. We discuss the advantages and limitations of the approach and its implications for user modelling. 相似文献
998.
This paper examines the evolution of the LCD industry in Hong Kong, from the beginnings in the 1970s, when imitation strategies were relatively easily implemented, to the 1990s, when some local companies are finding niches in the global market. Increasingly, however, they are facing pressures to re-examine their product development systems in more fundamental fashion. The paper points to the possibilities and limits of a “growth without R&D” strategy. 相似文献
999.
1000.
Andrew I Cooper Joseph M DeSimone 《Current Opinion in Solid State & Materials Science》1996,1(6):761-768
The use of carbon dioxide as an inert solvent has emerged recently as an important development in polymer chemistry. The past year has seen major advances in the synthesis of a variety of polymeric materials in carbon dioxide. At the same time complementary studies have successfully elucidated the physical behavior of a range of polymers in carbon dioxide solution. Herein we review both synthetic and physical studies that are defining the scope of this approach. 相似文献