全文获取类型
收费全文 | 4452篇 |
免费 | 27篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 24篇 |
综合类 | 6篇 |
化学工业 | 188篇 |
金属工艺 | 48篇 |
机械仪表 | 34篇 |
建筑科学 | 38篇 |
矿业工程 | 9篇 |
能源动力 | 28篇 |
轻工业 | 95篇 |
水利工程 | 10篇 |
石油天然气 | 67篇 |
无线电 | 120篇 |
一般工业技术 | 418篇 |
冶金工业 | 3178篇 |
原子能技术 | 38篇 |
自动化技术 | 180篇 |
出版年
2021年 | 30篇 |
2020年 | 24篇 |
2019年 | 32篇 |
2018年 | 42篇 |
2017年 | 26篇 |
2016年 | 34篇 |
2014年 | 32篇 |
2013年 | 67篇 |
2012年 | 39篇 |
2011年 | 49篇 |
2010年 | 46篇 |
2009年 | 36篇 |
2008年 | 43篇 |
2007年 | 41篇 |
2006年 | 63篇 |
2005年 | 38篇 |
2004年 | 36篇 |
2003年 | 40篇 |
2002年 | 27篇 |
2001年 | 21篇 |
2000年 | 18篇 |
1999年 | 141篇 |
1998年 | 981篇 |
1997年 | 572篇 |
1996年 | 379篇 |
1995年 | 203篇 |
1994年 | 172篇 |
1993年 | 221篇 |
1992年 | 37篇 |
1991年 | 40篇 |
1990年 | 47篇 |
1989年 | 53篇 |
1988年 | 33篇 |
1987年 | 55篇 |
1986年 | 45篇 |
1985年 | 51篇 |
1984年 | 19篇 |
1983年 | 24篇 |
1982年 | 35篇 |
1981年 | 19篇 |
1980年 | 47篇 |
1978年 | 25篇 |
1977年 | 88篇 |
1976年 | 146篇 |
1974年 | 16篇 |
1973年 | 18篇 |
1970年 | 19篇 |
1969年 | 20篇 |
1968年 | 19篇 |
1966年 | 16篇 |
排序方式: 共有4481条查询结果,搜索用时 93 毫秒
1.
2.
3.
This report analyzes the intracorporal lengths of 236 consecutive organically impotent men who underwent insertion of a penile prosthesis. The average right or left intracorporal length in this series was 20.9 cm, with a standard deviation of 2.2 cm. Intracorporal length ranged from 14-27 cm. This data may be used as reference ranges for penile prosthesis manufacturers, and for Urologists who implant prostheses or perform penile lengthening procedures. 相似文献
4.
5.
The results of block model calculations for multiple discretizations of a dielectric sphere and circular cylinder suggest that it is essential that the cells must be arranged for a best-fit of the body being modeled, the matrix elements must be reasonably accurate, and the cells must be small enough so that the pulse-function basis approximation is not blatantly unreasonable. When these criteria are approximately satisfied the remaining errors appear to be mainly due to imperfect representation of the shape of the object being modeled. It appears that the accuracy can be improved by using discretizations having cells of reduced size near the surface of the object. Geometric factors are defined which allow testing the potential accuracy of a solution without dimensioning or inverting a large matrix. Several unique procedures for discretization are also described that have the potential of partially mitigating the errors due to inaccurate representation of the shape of a scatterer. 相似文献
6.
Recent research has found that family caregivers do not discuss their caregiving in terms of tasks but instead describe their care as shaped by concerns, commitments and goals. The purpose of this paper is to challenge the ways in which nurses approach the family caregiving process and to explore possibilities for evolving nursing knowledge by questioning existing practice in the light of developing insight into the ways in which being a family caregiver is meaningful. A critique of the philosophical orientations of rationalism and empiricism provides a platform to discuss the merits of a Heideggerian phenomenological approach in assisting nurses to better understand family caring experience. Such critique serves to support the notion of displacing the traditional scientific view as the prime means of disclosing truth, acknowledging alternative ways of knowing. 相似文献
7.
N. S. Pronkin R. B. Sharafutdinov O. M. Kovalevich A. A. Smetnik A. G. Levin S. A. Kabakchi O. L. Masanov 《Atomic Energy》2003,94(6):398-404
This paper is devoted to the development of a method for hazard classification of holding ponds at the Industrial Association Mayak, the Siberian Intergrated Chemical Plant, and the Integrated Iron-Mining and Mining-Chemical Plant. The method is based on a combined approach employing the qualitative characteristics and quantitative parameters of the ponds. The classification of holding ponds is intended to be used for developing the requirements for the composition and content of the documentation presented by enterprises for licensing the operation and decommissioning of holding ponds. 相似文献
8.
The Trichuris muris-mouse model of intestinal helminth infection provides a convenient system to examine the immune mechanisms operating during acute and chronic infection. Particular subsets of helper T lymphocytes (CD4+Th cells) play an important role in regulating infection via the secretion of distinct groups of cytokines. Reciprocal activation of Th cell subsets is associated with either expulsion of the parasites from the intestine (Th2 cells) or chronic infection (Th1 cells). In vivo neutralization experiments using anti-cytokine monoclonal antibodies show that critical cytokines are involved, with interferon-gamma playing an important role in the establishment of chronic trichuriasis and interleukin-4 in expulsion of the parasite from the gut. This model has provided clear evidence of a crucial role for distinct cytokines in mediating host protection against intestinal helminth infection and that manipulation of the immune response through the Th cell-cytokine axis can benefit either the host or the parasite. As such, the T. muris model is poised to generate important new data relevant not only to intestinal helminthiasis but to the wider field of parasite immunity and infection in general. 相似文献
9.
Among a variety of experimental protocols used, the combined use of 0.5% dextrose in bottom agar and 1 micromol of flavin mononucleotide (FMN) in preincubation mixtures without fraction S9 mix resulted in the highest level of induced Salmonella typhimurium his reversions with both dyes metanil yellow and orange 11 with strain TA100. Strain TA98 yielded notably lower levels of reversions under the same conditions. The presence of uninduced hamster liver S9 fraction resulted in a weak mutagenic response while Aroclor 1254-induced rat liver S9 fraction resulted in the complete absence of mutagenicity with both strains and with both dyes. 相似文献
10.
Infection in a wound represents a colony count of 10(5) or greater. Contamination is the presence of many surface organisms. Moist wound healing, not dehydration, protects and prepares the wound for coverage and closure. Relief of pain is a critical factor in achieving healing: a biological or pharmaceutical device can achieve protection and facilitate healing. 相似文献