全文获取类型
收费全文 | 38428篇 |
免费 | 3509篇 |
国内免费 | 1807篇 |
学科分类
工业技术 | 43744篇 |
出版年
2024年 | 242篇 |
2023年 | 720篇 |
2022年 | 1273篇 |
2021年 | 1744篇 |
2020年 | 1272篇 |
2019年 | 1149篇 |
2018年 | 1293篇 |
2017年 | 1333篇 |
2016年 | 1196篇 |
2015年 | 1585篇 |
2014年 | 1988篇 |
2013年 | 2203篇 |
2012年 | 2478篇 |
2011年 | 2410篇 |
2010年 | 2171篇 |
2009年 | 2097篇 |
2008年 | 2023篇 |
2007年 | 1941篇 |
2006年 | 1891篇 |
2005年 | 1561篇 |
2004年 | 1135篇 |
2003年 | 1372篇 |
2002年 | 1606篇 |
2001年 | 1330篇 |
2000年 | 1018篇 |
1999年 | 942篇 |
1998年 | 684篇 |
1997年 | 620篇 |
1996年 | 586篇 |
1995年 | 438篇 |
1994年 | 346篇 |
1993年 | 265篇 |
1992年 | 190篇 |
1991年 | 161篇 |
1990年 | 138篇 |
1989年 | 86篇 |
1988年 | 68篇 |
1987年 | 42篇 |
1986年 | 40篇 |
1985年 | 19篇 |
1984年 | 17篇 |
1983年 | 14篇 |
1982年 | 13篇 |
1981年 | 9篇 |
1980年 | 16篇 |
1979年 | 3篇 |
1973年 | 2篇 |
1970年 | 1篇 |
1959年 | 2篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Xue‐Yong Liu Xiao‐Bin Ding Zhao‐Hui Zheng Yu‐Xing Peng Albert S
C Chan C
W Yip Xin‐Ping Long 《Polymer International》2003,52(2):235-240
Amphiphilic magnetic microspheres ranging in diameter from 5 to 100 µm were prepared by dispersion copolymerization of styrene and poly(ethylene oxide) vinylbenzyl (PEO‐VB) macromonomer (MPEO) in the presence of Fe3O4 magnetic fluid. The effects of various polymerization parameters on the average particle size were systematically investigated. The average particle size was found to increase with increasing styrene concentration and initiator concentration. It also increased with decreasing stabilizer concentration and molecular weight of MPEO. The content of the hydroxyl groups localized in the microspheres ranged from 0.01 to 0.2 mmol g?1. © 2003 Society of Chemical Industry 相似文献
3.
The catalytic activities of alumina prepared from an Al alkoxide-amine adduct monomer for the reaction of cyclopentene oxide with piperidine was determined after various pretreatments, including calcination and exposure to moisture. They were compared with the activity of alumina prepared by the conventional hydrolysis method. It was found that the as-prepared sample from the alkoxide-amine monomer preparation was five times more active than a conventional preparation, suggesting that it has a higher density of surface Lewis acid sites. However, its activity was much more severely suppressed by exposure to moisture. 相似文献
4.
5.
6.
7.
8.
Jun-Fa Mao Zheng-Fan Li 《Microwave Theory and Techniques》1992,40(4):637-644
A new method for analysis of the time response of multiconductor transmission lines with frequency-dependent losses is presented. This method can solve the time response of various kinds of transmission lines with arbitrary terminal networks. Particularly, it can analyze nonuniform lines with frequency-dependent losses, for which no effective method for analyzing their time response exists. This method starts from the frequency-domain telegrapher's equations. After decoupling and inversely Fourier transforming, then a set of decoupled time-domain equations including convolutions are given. These equations can be solved with the characteristic method. The results obtained with this method are stable and accurate. Two examples are given to illustrate the application of this method to various multiconductor transmission lines 相似文献
9.
Laparoscopic retroperitoneal lymph node dissection is a new surgical procedure used to enhance staging in men with clinical stage I nonseminomatous germ cell tumors of the testis. The procedure has been performed in a limited number of patients at several centers with extensive laparoscopic experience. Laparoscopic retroperitoneal lymphadenectomy is a technically demanding procedure which can be successfully completed in the majority of patients. However, the risk of complications is greater than in patients who undergo standard open retroperitoneal lymph node dissection. The primary advantage of a laparoscopic approach is shortened hospitalization and rapid return to normal activity. The role of laparoscopy in the management of patients with testis malignancy has not been defined. The use of this staging procedure may help minimize the need for surveillance studies following surgery and may be best utilized in men with a lower likelihood of nodal metastases. Ultimately, prospective study in large groups of patients will be necessary to determine the role of laparoscopic retroperitoneal lymph node dissection in patients with testis cancer. 相似文献
10.
Modeling ion implantation of HgCdTe 总被引:2,自引:0,他引:2
H. G. Robinson D. H. Mao B. L. Williams S. Holander-Gleixner J. E. Yu C. R. Helms 《Journal of Electronic Materials》1996,25(8):1336-1340
Ion implantation of boron is used to create n on p photodiodes in vacancy-doped mercury cadmium telluride (MC.T). The junction
is formed by Hg interstitials from the implant damage region diffusing into the MC.T and annihilating Hg vacancies. The resultant
doping profile is n+/n-/p, where the n+ region is near the surface and roughly coincides with the implant damage, the n- region is where Hg vacancies have been annihilated revealing a residual grown-in donor, and the p region remains doped by
Hg vacancy double acceptors. We have recently developed a new process modeling tool for simulating junction formation in MC.T
by ion implantation. The interstitial source in the damage region is represented by stored interstitials whose distribution
depends on the implant dose. These interstitials are released into the bulk at a constant, user defined rate. Once released,
they diffuse away from the damage region and annihilate any Hg vacancies they encounter. In this paper, we present results
of simulations using this tool and show how it can be used to quantitatively analyze the effects of variations in processing
conditions, including implant dose, annealing temperature, and doping background. 相似文献