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991.
F(2)-Isoprostanes (F(2)-IsoPs), regio- and stereoisomers of prostaglandin F(2alpha) (PGF(2alpha)), and urinary F(2)-IsoP metabolites including 2,3-dinor-5,6-dihydro-8-iso-PGF(2alpha) [2,3-dinor-8-iso-PGF(1alpha) (2,3-dinor-F1)] and 2,3 dinor-8-iso-PGF(2alpha) (2,3-dinor-F2), have all been used as biomarkers of oxidative stress. A novel method was developed to measure these biomarkers using a single solid phase extraction (SPE) cartridge, separation by HPLC, and detection by negative mode selected reaction monitoring (SRM) mass spectrometry (MS), using authentic standards of PGF(2alpha); 8-iso-PGF(2alpha); 2,3-dinor-F1 and 2,3-dinor-F2 to identify specific chromatographic peaks. The method was validated in a population of healthy, college-aged nonsmokers (n = 6 M/8F) and smokers (n = 6 M/5F). Urinary F(2)-IsoP concentrations were approximately 0.2-1.5 microg/g creatinine, 2,3-dinor-F1 was approximately1-3 microg/g and 2,3-dinor-F2 was approximately 3-5 microg/g. Additional F(2)-IsoPs metabolites were identified using SRM. The sum of all urinary F(2)-IsoP metabolites was 50-100 microg/g creatinine indicating their greater abundance than F(2)-IsoPs. Women had higher F(2)-IsoP metabolite concentrations than did men (MANOVA, main effect P = 0.003); cigarette smokers had higher concentrations than did nonsmokers (main effect P = 0.036). For men or women, respectively, smokers had higher metabolite concentrations than did nonsmokers (P < 0.05). Thus, our method simultaneously allows measurement of urinary F(2)-IsoPs and their metabolites for the determination of oxidative stress. 相似文献
992.
Single-crystalline K2Nb8O21 nanoribbons with width of 100–500 nm and thickness of ca. 30 nm, and length up to tens of micron, have been successfully synthesized by simply calcining Nb2O5 powders in molten KCl, and characterized with XRD, SEM, SEM, HRTEM and selected-area electron diffraction technique. The growth direction of the obtained K2Nb8O21 nanoribbons was determined to be the 〈1 0 0〉 crystallography direction. 相似文献
993.
The present work deals with pre-reforming of logistic hydrocarbon fuel (jet fuel) as a part of an integrated approach to developing an on-board fuel reformer for use in a micro-solid-oxide fuel cell system. The purpose of doing pre-reforming is to ensure carbon-free reformulation of JP-8 jet fuel into hydrogen and carbon monoxide for use in a micro-solid-oxide fuel cell. Several model jet fuels have been tested for the pre-reforming at low temperature (450–550 °C) in a lab-scale reforming reactor. Proper temperature control and pre-mixing of feed fuels and steam have been found to be important for the prevention of coke formation prior to pre-reforming. Both noble metal and base-metal catalysts have been prepared and tested. As compared with an Al2O3-supported Ni catalyst, supported Rh catalysts show not only high activity but also high resistance to deactivation due to carbon formation. Removal of residual Cl− from Rh/CeO2–Al2O3 improves the metal dispersion and the pre-reforming activity. The reformates from the current pre-reformer contain mainly CH4, CO, H2, in which CH4 can be further converted to H2 and CO by subsequent main-reforming. 相似文献
994.
新型水溶性萘啶基荧光材料的制备及性能研究 总被引:1,自引:0,他引:1
本文制备得到一种新型萘啶基的水溶性光致发光聚合物:聚丙烯酸(PAA)-2-苄氨基-7-甲基-1,8-蔡啶,PAA5-PAMN2(PAMN是2-phenmethy-lamino-7-methyl-1,8-naphthyridine的缩写),经光谱分析和密度泛函理论计算,研究了化合物的结构和组成,这种聚合物在酸性和碱性条件下呈现最大的吸收波长分别为364和342nm.Zn(OAc)2,的加入致使PAA5-PAMN,水溶液的荧光猝灭,而当OAcˉ改变为NO3ˉ时,在荧光强度不断降低的同时,由于NO3ˉ离子的配位使最大发射波长从410nm蓝移到400nm.Na^+离子对其没有明显的荧光猝灭效应, 相似文献
995.
Theoretical and experimental study on hydrodynamic characteristics of fluidization in air-sand conical beds 总被引:1,自引:0,他引:1
Rachadaporn Kaewklum 《Chemical engineering science》2008,63(6):1471-1479
This work was aimed at modeling hydrodynamic characteristics of fluidization in conical beds using quartz sand as the inert bed material and air as the fluidizing agent. The minimum fluidization velocity, umf, and the minimum velocity of full fluidization, umff, were determined by Peng and Fan's models modified for conical fluidized bed. Meanwhile, the pressure drop across a bed, Δp (including Δpmax and Δpmff corresponding to umf and umff, respectively), was predicted by using modified Ergun's equations for variable superficial air velocity at an air distributor, u0. The predicted results were validated by experimental data for some operating conditions. Effects of the sand particle size, cone angle and static bed height on the fluidization pattern and hydrodynamic characteristics are discussed. With the proposed models, the Δp-u0 diagram were obtained with rather high accuracy for the conical air-sand beds of 30-45° cone angles and 20-30 cm static bed heights, when using 300-886X-si40.gif"> sand particles. For the predicted umf and umff, the relative computational errors were found to be within 20% for wide ranges of operating variables, whereas Δpmax and Δpmff could be predicted with lower (10-15%) relative errors. With higher cone angles and/or bed heights, the computational accuracy was found to deteriorate. 相似文献
996.
Robert P. Warzinski David E. Riestenberg Igor V. Haljasmaa Costas Tsouris 《Chemical engineering science》2008,63(12):3235-3248
Sinking CO2 composite particles consisting of seawater, liquid CO2, and CO2 hydrate were produced by a coaxial flow injector fed with liquid CO2 and artificial seawater. The particles were injected into a high-pressure water tunnel facility to permit determination of their settling velocities and dissolution rates. Injections were performed at fixed pressures approximately equivalent to 1200-m, 1500-m, and 1800-m depths and at temperatures varying from approximately 2 to 5 °C. Immediately after injection, the cylindrical particles were observed to break away from the injector tip and often aggregated into sinking clusters. The seawater flow in the tunnel was then adjusted in a countercurrent flow mode to suspend the particles in an observation window so that images of the particles could be recorded for later analysis. The flow would often break or cause rearrangement of some of the clusters. Selected individual particles and some clusters were studied until they became too hydrodynamically unstable to follow. In general, the flow required to suspend clusters or individual particles decreased with time as the particles dissolved. For example, one particle was produced and observed for over 6 min at an average pressure of 15.022 MPa and an average temperature of 5.1 °C. Its sinking rate, determined from the flow required for stabilization, changed from 37.2 to 3.3 mm/s over this time. Particle sinking rates were compared to correlations from the literature for uniform cylindrical objects. Reasonable agreement was observed for short times; however, the observed decrease in sinking velocity with time was greater than that predicted by the correlations for longer times. Particle dissolution rates, based on changes in diameter, were also determined and varied from 5 to 800122X-si45.gif">. A pseudo-homogeneous mass transfer model was used to predict single-particle dissolution rates. Good agreement was achieved between experimental dissolution data and the modeling results. 相似文献
997.
目的观察旋毛虫感染对BALB/c小鼠体内人结肠癌HCT-8细胞生长的作用。方法用不同剂量的旋毛虫感染BALB/c小鼠,并在不同时间接种HCT-8细胞,荷瘤20 d后解剖小鼠,测定小鼠体内肿瘤的体积、重量,计算抑瘤率,并检测T淋巴细胞亚群。结果各实验组小鼠肿瘤体积和重量均显著低于对照组,CD3+、CD4+、CD8+、CD4+/CD8+比值、未长瘤小鼠比例、小鼠死亡率和抑瘤率均显著高于对照组;先接虫后荷瘤组抑瘤效果优于先荷瘤后接虫组。结论旋毛虫对BALB/c小鼠体内的人结肠癌HCT-8细胞的生长有一定的抑制作用。 相似文献
998.
基于XC2VP30的多路数字视频光端机 总被引:1,自引:0,他引:1
为了降低多路数据光纤通信的系统成本,提高性能,提出了一种基于XC2VP30的多路数字视频光端机的设计.光端机利用视频压缩和XC2VP30內嵌的MGT模块,实现多路数字视频的实时传输.设计主要包括数字信号的复用/解复用,数字视频压缩/解压缩,高速并/串转换等部分,应用FPGA编程,8B/10B编码以及视频压缩等技术实现了高速视频信息的无误传输.利用Virtex II Pro开发板进行硬件调试,实验证明设计结构简单,成本低,性能稳定,抗干扰能力强,可用于管道、公路、楼宇等处进行监控,在工业中具有很大的应用价值. 相似文献
999.
Kee Young No Gi Dae Kim Gyu Man Kim 《Journal of Mechanical Science and Technology》2008,22(9):1765-1771
We report the results of diffuser lithography applied to a negative-type thick photoresist to fabricate 3-dimensional microstructures
suspended on supports. When UV light passes through a diffuser film, the direction of the light is randomized because of the
irregular surface of the diffuser. By exposing through a diffuser on a Cr-mask, a circular or an elliptical cross-section
of exposed region can be formed on a spin-coated photoresist. When applied to a negative-type thick photoresist, diffuser
lithography gives a 3-dimensional circular cross-section of the exposed and cross-linked regions, which could be used for
making suspended microstructures. The size of the exposed region has been controlled by the dose of the UV light. The current
study clearly shows that the depth of exposed region of photoresist is affected by the geometry of the pattern. By controlling
the depth of the exposed region using different pattern size, beam structures suspended on the support structures could be
fabricated by single exposure process. The characteristics of the diffuser lithography process were investigated on a negative
type photopolymer, SU-8, with different doses of UV-light and different geometry. 相似文献
1000.
Hiroshi Yamaguchi Xin-Rong Zhang Katsumi Fujima 《International Journal of Refrigeration》2008,31(3):404-410
In this paper, a cryogenic refrigeration method is described, which utilizes CO2 solid–gas two phase flow and the dry ice. The CO2 solid–gas two phase flow is achieved by expanding liquid CO2 and thus refrigeration process less than CO2 triple point −56.6 °C can be available. The experimental work is divided into two parts and two experimental set-ups were designed, constructed and tested. The interest of the first experiment test is the feasibility of expanding liquid CO2 into CO2 solid–gas flow in a horizontal circular tube by expansion valve. The second experiment focuses on the feasibility of the refrigeration of liquid CO2 expanding into solid–gas two phase flows used in a prototype CO2 heat pump system. The results show that solid–gas two phase flows can be achieved by expanding liquid CO2 by expansion valve in a closed CO2 heat pump system loop and low temperature refrigeration below −56.6 °C is achieved in the experiments, which give greater possibility to create a cryogenic refrigeration process below −56.6 °C for food industries, bio-medical engineering, etc. 相似文献