首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1291篇
  免费   82篇
  国内免费   1篇
电工技术   18篇
综合类   2篇
化学工业   206篇
金属工艺   28篇
机械仪表   94篇
建筑科学   47篇
矿业工程   3篇
能源动力   40篇
轻工业   121篇
水利工程   7篇
石油天然气   2篇
无线电   170篇
一般工业技术   216篇
冶金工业   202篇
原子能技术   7篇
自动化技术   211篇
  2024年   2篇
  2023年   16篇
  2022年   30篇
  2021年   50篇
  2020年   22篇
  2019年   39篇
  2018年   44篇
  2017年   39篇
  2016年   66篇
  2015年   41篇
  2014年   53篇
  2013年   99篇
  2012年   58篇
  2011年   74篇
  2010年   49篇
  2009年   74篇
  2008年   49篇
  2007年   42篇
  2006年   53篇
  2005年   56篇
  2004年   41篇
  2003年   29篇
  2002年   29篇
  2001年   21篇
  2000年   14篇
  1999年   21篇
  1998年   76篇
  1997年   47篇
  1996年   37篇
  1995年   13篇
  1994年   9篇
  1993年   25篇
  1992年   8篇
  1991年   4篇
  1990年   2篇
  1988年   3篇
  1987年   4篇
  1986年   4篇
  1985年   4篇
  1983年   2篇
  1982年   2篇
  1979年   3篇
  1976年   5篇
  1975年   2篇
  1974年   2篇
  1973年   1篇
  1972年   2篇
  1971年   1篇
  1965年   1篇
  1939年   1篇
排序方式: 共有1374条查询结果,搜索用时 0 毫秒
151.
This paper presents a procedure for finding the reliability-based optimum design of cable-stayed bridges. The minimisation problem is stated as the minimisation of stresses, displacements, reliability and bridge cost. A finite-element approach is used for structural analysis. It includes a direct analytic sensitivity analysis module, which provides the structural behaviour responses to changes in the design variables. An equivalent multicriteria approach is used to solve the non-differentiable, non-linear optimisation problem, turning the original problem into the sequential minimisation of unconstrained convex scalar functions, from which a Pareto optimum is obtained. Examples are given illustrating the procedure.  相似文献   
152.
This paper investigates the work function adjustment on fully silicided (FUSI) NiSi metal gates for dual-gate CMOS, and how it is effected by the poly-Si dopants. By comparing FUSI on As-, B-, and undoped poly-Si using the same p-Si substrates, it is shown that both As and B influence the work function of NiSi FUSI gate significantly, with As showing more effects than B possibly due to more As pile-up at the NiSi-SiO/sub 2/ interface. No degradations on the underlying gate dielectrics are observed in terms of interface state density (D/sub it/), fixed oxide charges, leakage current, and breakdown voltage, suggesting that NiSi FUSI is compatible with dual-gate CMOS processing.  相似文献   
153.
We propose a filter‐free wavelength conversion using a Mach‐Zehnder interferometer with monolithically integrated 2×2 multimode interference semiconductor optical amplifiers (MMI‐SOAs). The device has been optimized by considering a non‐homogeneous carrier distribution due to the self‐imaging properties of the MMI‐SOA. Static measurements show an extinction ratio of up to 18 dB and an input signal rejection ratio of up to 20 dB.  相似文献   
154.
A linear programming (LP) model has been developed to optimize the amount of power system peak load reduction through scheduling of control periods in commercial/industrial and residential load control programs at Florida Power and Light Company, USA. The LP model can be used to determine both long and short term control scheduling strategies and for planning the number of customers which should be enrolled in each program. Results of applying the model to a forecasted late 1990s summer peak day load shape are presented. It is concluded that LP solutions provide a relatively inexpensive and powerful approach to planning and scheduling load control. Also, it is not necessary to model completely general scheduling of control periods in order to obtain near best solutions to peak load reduction  相似文献   
155.
The aim of this study is to provide evidence on the aphrodisiac property of Eurycoma longifolia Jack. An electric grid was used as an obstruction in the electrical copulation cage in order to determine how much an aversive stimulus the sexually naive male rat for both the treated with E. longifolia Jack and control groups were willing to overcome to reach the estrous receptive female in the goal cage. The intensity of the grid current was maintained at 0.12 mA and this was the intensity in which the male rats in the control group failed to crossover to reach the goal cage. Results showed that E. longifolia Jack continued to enhance and also maintain a high level of both the total number of successful crossovers, mountings, intromissions and ejaculations during the 9-12th week observation period. In conclusion, these results further enhanced and strengthened the aphrodisiac property of E. longifolia Jack.  相似文献   
156.
A compact and novel modified planar inverted-F antenna (PIFA) for dual ISM-band application is proposed. The proposed antenna, including a small ground plane, occupies a volume of 20/spl times/23.7/spl times/0.8 mm/sup 3/ (FR-4). The impedance bandwidth with 10 dB return loss is about 150 MHz (2380-2530 MHz) for 2.4 GHz band and 1450 MHz (5130-6580 MHz) for 5 GHz band. The measured radiation patterns are approximately omnidirectional and yield a gain of 1.0 dBi at 2440 MHz and 3.98 dBi at 5600 MHz, respectively.  相似文献   
157.
The authors report the first highly reliable all-MOVPE BH lasers. These devices have extremely low threshold currents (≃10 mA) and show excellent uniformity of device characteristics. Data are presented to show the high yields achieved and demonstrate the very low degradation rates achieved under accelerated aging  相似文献   
158.
159.
The role of the post-processor in computer programming systems for numerically controlled machines is described. Although many of the points discussed apply to the special purpose programs available, attention is concentrated on the position of the post-processor within the general purpose systems such as APT and NELAPT.

The design of modular programs which allow rapid adaptation for different machine tools is considered in detail and the features of an adequate user specification are described.  相似文献   

160.
Evidence accumulated in in-vitro fertilization (IVF) cycles suggests that the use of long-acting forms of gonadotrophin-releasing hormone analogues (GnRHa) for pituitary desensitization may impair the outcome of IVF as compared to classical short-acting formulations. Whether the negative effects are directed against the corpus luteum, the endometrium, or both is unknown. However, the presence of high affinity binding sites for gonadotrophin-releasing hormone (GnRH) in the human endometrium suggests a possible role of these analogues on this target organ, affecting embryo implantation. In the present study, we tested direct effects of two different forms of GnRHa on implantation using the ovum donation model. Patients were prospectively allocated to one of the three study groups: the short-acting form of the analogue leuprolide acetate (group I; n=64), the long-acting form of the same analogue (group II; n=58), and the long-acting preparation of the analogue tryptorelin (group III; n=61). A total of 68 cycles of embryo transfer was carried out in group I, whereas 67 were performed in group II and 65 in group III. Cancellation rates were respectively 18.1, 17.3 and 18.8% because of bleeding while being on the waiting list for anonymous oocyte donation. The number of oocytes donated, fertilization rates and embryos replaced in each group were similar. As a result, pregnancy rate per transfer was 38.2, 49.3 and 44.6% respectively. Implantation rates per embryo replaced were respectively 13.4, 19.1 and 17.0%. These data suggest that the use of a long-acting form of GnRHa provides success rates similar to the short-acting preparations, resulting in more convenient medication for patients with ovarian function included in ovum donation programmes.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号