全文获取类型
收费全文 | 2023篇 |
免费 | 9篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 19篇 |
化学工业 | 152篇 |
金属工艺 | 9篇 |
机械仪表 | 10篇 |
建筑科学 | 29篇 |
矿业工程 | 1篇 |
能源动力 | 60篇 |
轻工业 | 20篇 |
水利工程 | 3篇 |
无线电 | 78篇 |
一般工业技术 | 180篇 |
冶金工业 | 1422篇 |
自动化技术 | 52篇 |
出版年
2023年 | 5篇 |
2021年 | 10篇 |
2020年 | 8篇 |
2019年 | 11篇 |
2018年 | 11篇 |
2017年 | 5篇 |
2016年 | 9篇 |
2015年 | 4篇 |
2014年 | 13篇 |
2013年 | 42篇 |
2012年 | 17篇 |
2011年 | 20篇 |
2010年 | 14篇 |
2009年 | 16篇 |
2008年 | 23篇 |
2007年 | 27篇 |
2006年 | 16篇 |
2005年 | 11篇 |
2004年 | 8篇 |
2003年 | 14篇 |
2002年 | 14篇 |
2001年 | 12篇 |
2000年 | 10篇 |
1999年 | 48篇 |
1998年 | 393篇 |
1997年 | 263篇 |
1996年 | 165篇 |
1995年 | 90篇 |
1994年 | 93篇 |
1993年 | 93篇 |
1992年 | 26篇 |
1991年 | 36篇 |
1990年 | 29篇 |
1989年 | 34篇 |
1988年 | 21篇 |
1987年 | 49篇 |
1986年 | 43篇 |
1985年 | 26篇 |
1984年 | 16篇 |
1983年 | 18篇 |
1982年 | 30篇 |
1981年 | 27篇 |
1980年 | 26篇 |
1979年 | 13篇 |
1978年 | 12篇 |
1977年 | 46篇 |
1976年 | 88篇 |
1975年 | 6篇 |
1974年 | 7篇 |
1972年 | 5篇 |
排序方式: 共有2035条查询结果,搜索用时 546 毫秒
1.
Wireless Personal Communications - This paper summarizes the ongoing research initiatives based on the advanced multiple access techniques towards the fifth generation (5G) wireless communication... 相似文献
2.
3.
L Giorgi A Di Filippo A Franchini L Rizzo S Benvenuti M Conti GP Novelli 《Canadian Metallurgical Quarterly》1994,60(1-2):43-47
OBJECTIVE: The reflex response to orotracheal intubation provokes an increase of arterial pressure accompanied by an increase of chorioides volume and a consequent ocular hypertone. There are several methods to reduce the reflex response due to intubation. One of the most effective is topical anaesthesia of larynx and trachea. Experiments were directed to evaluate the efficacy of topical anaesthesia to reduce the intraocular hypertone due to orotracheal intubation. DESIGN: A prospective randomized mask study was conduct on patients undergoing ophthalmologic (anterior segment) surgery at the Eye Clinic of Florence University. METHODS: Intraocular pressure was measured by a Goldman tonometer at four times: T0 = basal, T1 = 2' minutes after induction of general anaesthesia, T2 = 2' minutes after laryngoscopy, T3 = 2' minutes after orotracheal intubation. At the same moments, systolic blood pressure, heart rate, rate pressure pro duct were measured. Patients were randomly divided in two groups: Group L (n = 10) in which was evaluated the efficacy of laryngotracheal topical spray of lidocaine 4% (2 ml) and Group F (n = 10) in which saline was used instead of anesthetic. The filling of the LTA kit (Abbott) was made by a person not involved in the experiments. DATA ANALYSIS: Student's t test for unpaired data. RESULTS: Topical anaesthesia reduces the increase of intraocular pressure, hypertension and rate pressure product due to intubation. The intraocular pressure reduces to 13% less than basal value in Group L and increase to 50% more than basal value in Group F. CONCLUSION: The topical anaesthesia of larynx and trachea is effective to reduce the intraocular hypertension due to the reflex response evoked by orotracheal intubation. 相似文献
4.
5.
AD Santin PL Hermonat JC Hiserodt J Fruehauf V Schranz D Barclay S Pecorelli GP Parham 《Canadian Metallurgical Quarterly》1997,64(3):477-480
Tumor cells from eight freshly isolated cervical cancers (i.e., four adenocarcinomas and four squamous carcinomas) were analyzed for their production of the immune-inhibitory cytokine transforming growth factor-beta (TGF-beta) in vitro. All fresh adenocarcinomas secreted significant levels of TGF-beta (mean 397, range between 207 and 782 pg/ml/10(5) cells/48 hr). In contrast, no detectable TGF-beta was present in the supernatants from the four fresh squamous carcinoma cultures (P < 0.001). These data suggest that major differences in the secretion of the immunoinhibitory cytokine TGF-beta exist between squamous cell carcinomas and adenocarcinomas of the uterine cervix. Furthermore, these findings suggest that at least some of the differences in the natural biologic behavior, as well as in the response to radiation treatment, between these two histologic types of cervical cancer could be related to differences in secretion of this immune-inhibitory cytokine. 相似文献
6.
Geoffrey M. Eggert Paul R. Dawson Kapil K. Mathur 《International journal for numerical methods in engineering》1991,31(6):1031-1054
A forming model based on a viscoplastic flow formulation is derived which includes the effects of small elastic strains. A significant feature of the formulation is its reliance on the dominant inelastic material characteristics in the formation of the stiffness matrix for large strain problems. The resultant non-linear system of equations is solved by an adaptive descent method which combines the rapid convergence of Newton's method near the solution with the robustness of a method of successive approximations. The use of the adaptive descent method effectively extends the viscoplastic flow formulations into the nearly rate-insensitive range of behaviours exhibited, for example, by metals at low temperature, where slow convergence of the non-linear solution algorithm has traditionally hampered their use. 相似文献
7.
Crystallization behaviour of amorphous Ni60 Nb40-x
Cr
x
(x = 0, 5, 10 and 13 at%) alloys was studied by differential Scanning calorimetry and X-ray diffraction measurements. It is shown that the addition of chromium reduces the crystallization temperature, stages of crystallization and activation energies associated with the crystallization sages of the Ni60Nb40 glass. Crystallization of the Ni60Nb40 glass occurred in three stages; in the initial stage a metastable M-phase formed in the amorphous matrix as reported earlier [1] . However, contrary to earlier observation [1], M -phase was not very stable and transformed together with some amorphous phase to the equilibrium Ni3Nb phase in the second stage of crystallization. In the third stage, the remaining amorphous matrix transformed to the equilibrium NiNb phase. On addition of chromium the formation/stability of the M-phase was found to be suppressed and equilibrium NbCr2 phase precipitated preferentially in the first stage. The second stage, corresponding to the formation of Ni3Nb phase, remained almost unaltered. The third stage corresponding to the crystallization of NiNb phase disappeared completely at 13 at% Cr. In the fully crystallized samples the proportion of the NiNb phase decreased and that of NbCr2 phase increased continuously with chromium concentration. 相似文献
8.
9.
M Hafezparast CG Cole GP Kaur RS Athwal PA Jeggo 《Canadian Metallurgical Quarterly》1994,20(6):541-548
A hamster-human hybrid containing only the q arm of chromosome 2 has been used to construct a panel of hybrids bearing reduced regions of chromosome 2 using the technique of irradiation fusion gene transfer. The human chromosome 2 carried the Ecogpt gene and all hybrids were selected using this marker. The integrated Ecogpt gene was localized to the region 2q33-34, resulting in the selective retention of this region in the hybrids. These data were combined with another previously constructed panel of hybrids containing regions of 2q, which were enriched for the region 2q36-37. The combined hybrid panel is useful for the mapping of new markers to defined regions of chromosome 2 and for the cloning of genes located on 2q by a positional strategy. 相似文献
10.