全文获取类型
收费全文 | 3282篇 |
免费 | 104篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 197篇 |
综合类 | 4篇 |
化学工业 | 1084篇 |
金属工艺 | 84篇 |
机械仪表 | 79篇 |
建筑科学 | 78篇 |
矿业工程 | 2篇 |
能源动力 | 112篇 |
轻工业 | 347篇 |
水利工程 | 9篇 |
石油天然气 | 2篇 |
无线电 | 196篇 |
一般工业技术 | 583篇 |
冶金工业 | 312篇 |
原子能技术 | 70篇 |
自动化技术 | 234篇 |
出版年
2023年 | 12篇 |
2022年 | 39篇 |
2021年 | 67篇 |
2020年 | 39篇 |
2019年 | 38篇 |
2018年 | 55篇 |
2017年 | 53篇 |
2016年 | 73篇 |
2015年 | 48篇 |
2014年 | 94篇 |
2013年 | 186篇 |
2012年 | 135篇 |
2011年 | 198篇 |
2010年 | 120篇 |
2009年 | 164篇 |
2008年 | 166篇 |
2007年 | 156篇 |
2006年 | 126篇 |
2005年 | 133篇 |
2004年 | 114篇 |
2003年 | 108篇 |
2002年 | 101篇 |
2001年 | 86篇 |
2000年 | 71篇 |
1999年 | 71篇 |
1998年 | 117篇 |
1997年 | 100篇 |
1996年 | 88篇 |
1995年 | 47篇 |
1994年 | 62篇 |
1993年 | 52篇 |
1992年 | 37篇 |
1991年 | 24篇 |
1990年 | 34篇 |
1989年 | 32篇 |
1988年 | 23篇 |
1987年 | 28篇 |
1986年 | 35篇 |
1985年 | 29篇 |
1984年 | 29篇 |
1983年 | 23篇 |
1982年 | 27篇 |
1981年 | 14篇 |
1980年 | 18篇 |
1979年 | 14篇 |
1978年 | 12篇 |
1976年 | 23篇 |
1975年 | 14篇 |
1974年 | 14篇 |
1973年 | 11篇 |
排序方式: 共有3393条查询结果,搜索用时 15 毫秒
41.
Kenta Miura Takeshi Tanemura Shunya Yamamoto Masaki Sugimoto 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2007,263(2):532-534
We fabricated fused-silica substrates which emit blue light by using Si-ion implantation and high-temperature annealing. Photoluminescence peak wavelengths are around 400 nm, and the peak intensities can be remarkable after annealing above 1150 °C. 相似文献
42.
M Yamamoto C Furihata Y Fujimitsu T Imai K Inada H Nakanishi M Tatematsu 《Canadian Metallurgical Quarterly》1997,88(3):238-244
BACKGROUND: Cigarette smoking has been shown to increase oxidative DNA damage in human sperm cells. Assessment of the role of cigarette smoking in the etiology of childhood cancer has focused primarily on the effect of maternal smoking. Similar studies in relation to paternal smoking, however, have been inconclusive. Few studies have evaluated the effect of paternal smoking in the preconception period, and most of these could not disentangle the effects of paternal from maternal smoking. PURPOSE: We investigated the relationship of paternal smoking, particularly in the preconception period, with childhood cancer among offspring of the nonsmoking mothers. METHODS: We conducted a population-based, case-control study in Shanghai, People's Republic of China, where the prevalence of smoking is high among men but extremely low among women. The study included 642 childhood cancer case patients (<15 years of age) and their individually matched control subjects. Information concerning parental smoking, alcohol drinking, and other exposures of the index child was obtained by direct interview of both parents of the study subjects. Odds ratios (ORs), derived from conditional logistic regression models, were used to measure the association between paternal smoking and risk of childhood cancers. RESULTS AND CONCLUSIONS: Paternal preconception smoking was related to a significantly elevated risk of childhood cancers, particularly acute leukemia and lymphoma. The risks rose with increasing pack-years of paternal preconception smoking for acute lymphocytic leukemia (ALL) (P for trend = .01), lymphoma (P for trend = .07), and total cancer (P for trend = .006). Compared with children whose fathers had never smoked cigarettes, children whose fathers smoked more than five pack-years prior to their conception had adjusted ORs of 3.8 (95% confidence interval [CI] = 1.3-12.3) for ALL, 4.5 (95% CI = 1.2-16.8) for lymphoma, 2.7 (95% CI = 0.8-9.9) for brain tumors, and 1.7 (95% CI = 1.2-2.5) for all cancers combined. Statistically significant increased risks of cancer were restricted to children under the age of 5 years at diagnosis or those whose fathers had smoked during all of the 5 years prior to conception. IMPLICATIONS: Further studies are needed to confirm the association of paternal smoking with increased risk of cancer in offspring, to clarify the pattern of risks in relation to the timing of cigarette smoking, and to elucidate the biologic mechanism involved in predisposing the offspring to cancer. For example, it may be that paternal smoking induces prezygotic genetic damage that, in turn, acts as the predisposing factor. 相似文献
43.
Nobuo Ishizawa Atsushi Saiki Takeshi Yagi Nobuyasu Mizutani Masanori Kato 《Journal of the American Ceramic Society》1986,69(2):18-C-
Crystals of yttria partially stabilized zirconia were grown by the arc-image floating-zone technique and studied by transmission electron microscopy. Crystals annealed at 1700°C consist of tetragonal precipitates and a cubic matrix. The platelike domains in a precipitate are twin-related tetragonal variants stacked alternately parallel to the (011) twin plane. The axial relations between the tetragonal precipitate and the cubic matrix are [100]tetragonal |[100]cubic , [011]tetragonal |[011]cubic . 相似文献
44.
The behavior of a premixed flame propagating from a chamber into a narrow channel at a high speed was examined using high speed and instantaneous schlieren photography, ion current measurement with electrostatic probes, and temperature measurement with an optical method. From detailed measurements of flames passing through the channel, flame extinguishment in the channel, no matter whether transient or not, was found to occur due to quenching of the reacting gas by rapid turbulent mixing with cold fresh mixture at the downstream of the contraction region and by heat transfer to the cold channel walls. Extinguishment must occur when these heat losses exceed the heat released by the chemical reaction of the flowing mixture. 相似文献
45.
MQ Fujita N Hashida M Shin H Nakanishi W Yoshihara K Aozasa 《Canadian Metallurgical Quarterly》1998,55(6):600-606
Poly(A)+ mRNA was isolated from leaves of potato plants (Solanum tuberosum L. cv. Desiree) according to standard protocols. This poly(A)+ mRNA was injected via glass microcapillaries into oocytes that were surgically removed from the African clawed toad Xenopus laevis. As a control, oocytes were either injected with H2O or remained untreated. Three days after injection the oocytes were analyzed by two electrode voltage clamping. Current voltage analysis revealed that a K+ channel from potato was functionally expressed in injected oocytes. The identity of this K+ channel was confirmed by its substrate specificity and a shift in the reversal potential. In particular, when the outside K+ concentration was increased the reversal potential of poly(A)+ injected oocytes shifted to more positive values. Furthermore, K+ outward currents declined when the outside K+ concentration was raised from 0.1 to 100 mM. Inward currents increased with an elevation of the K+ concentration. Several pharmaceuticals were tested for their potential to block this K+ channel. As a result, the channel was completely blocked by BaCl2. A three state reaction kinetic model was used to simulate the currents through the K+ transport protein as function of the extracellular K+ concentration. In particular, the simulation revealed current voltage relations that exactly matched the measured ones. Saturation of current voltage curves emerged from the simulation as a consequence of high extracellular potassium concentration. 相似文献
46.
T Ezaki N Koyanagi T Toyomasu Y Ikeda N Nakanishi K Sugimachi 《Canadian Metallurgical Quarterly》1998,45(23):1837-1841
BACKGROUND/AIMS: Liver cancer extension to the adjacent organs does not necessarily indicate tumor invasion. It is very hard to diagnose extrahepatic cancer invasion to the adjacent organs using preoperative imaging. This study was undertaken, therefore, to determine the real cancer invasion using a manual dissection. METHODOLOGY: Of the 51 consecutive patients with liver cancer, 6 cases with extrahepatically growing tumors were suspected to have cancer invasion both preoperatively and intraoperatively. Thus, we diagnosed whether or not any real extrahepatic cancer invasion was present by either removing the tumour by hand or by performing a blunt gauze dissection. RESULTS: Three hepatocellular carcinomas and one metastatic cancer were stripped off from the adjacent organ using a manual blunt dissection. However, the other two tumors could not be removed in the same manner and therefore a combined resection of the invaded portion had to be performed along with the hepatectomy. A postoperative detailed pathological examination revealed no cancer cells on the surface of the adjacent organ in the former 4 tumors. Cancer invasion was recognized, however, on the outside of the liver in the latter 2 combined resected tumors. CONCLUSIONS: An accurate intraoperative diagnosis of extrahepatic cancer invasion can be made using manual blunt dissection. 相似文献
47.
Kazuko Satake Ai Katayama Hideki Ohkoshi Takeshi Nakahara Takashi Takeuchi 《Sensors and actuators. B, Chemical》1994,20(2-3):111-117
Oxide semiconductors have been examined to develop NOx sensors for exhaust monitoring. Titania doped with trivalent elements, such as Al3+, Sc3+, Ga3+ or In3+, has a good sensitivity and selectivity to NO between 450 and 550 °C, and shows rapid response. A sensor probe for monitoring exhaust NOx has been fabricated. Many kinds of interference gases, such as C3H6, CO and SO2, have been found to have only a slight influence on the sensor response to NO. The influence of O2 and H2O is also negligible, except for the cases of 0% H2O and fuel-rich conditions. In accordance with these results, the sensor probe operates satisfactority in the exhaust gas of various combustion conditions without interference from the various kinds of gas species in the exhaust gases. 相似文献
48.
Takeshi Kikuchi Yoshizo Kitami Masato Yokoyama Hiroshi Sakai 《Journal of Materials Science》1989,24(12):4275-4278
The phase equilibria in the pseudo-binary system Bi2O3-TeO2 at 600° 950° C in air were examined by solid-state reaction techniques and X-ray powder diffraction method. Four pseudo-binary compounds appeared, i.e., -Bi2O3 type solid solution having a compositional range of (1-x)Bi2O3·xTeO2 wherex=0 0.4 a new compound Bi6Te2O15 which has an orthorhombic cell of a=2.27(4) nm, b=1.06(1) nm and c = 0.539(8) nm, 2Bi2O3 · 3TeO2, and an unidentified phase Bi2O3·2TeO2. The formation of the phase Bi6Te2O15, in which all the Te ions are hexavalent, was confirmed by the thermogravimetry and by the Mössbauer spectra. The liquidus curves for whole system were determined by DTA method. 相似文献
49.
Fuminori Tanihara Maki Hirata Nhien Thi Nguyen Osamu Sawamoto Takeshi Kikuchi Takeshige Otoi 《International journal of molecular sciences》2021,22(5)
Xenoantigens cause hyperacute rejection and limit the success of interspecific xenografts. Therefore, genes involved in xenoantigen biosynthesis, such as GGTA1, CMAH, and B4GALNT2, are key targets to improve the outcomes of xenotransplantation. In this study, we introduced a CRISPR/Cas9 system simultaneously targeting GGTA1, CMAH, and B4GALNT2 into in vitro-fertilized zygotes using electroporation for the one-step generation of multiple gene-edited pigs without xenoantigens. First, we optimized the combination of guide RNAs (gRNAs) targeting GGTA1 and CMAH with respect to gene editing efficiency in zygotes, and transferred electroporated embryos with the optimized gRNAs and Cas9 into recipient gilts. Next, we optimized the Cas9 protein concentration with respect to the gene editing efficiency when GGTA1, CMAH, and B4GALNT2 were targeted simultaneously, and generated gene-edited pigs using the optimized conditions. We achieved the one-step generation of GGTA1/CMAH double-edited pigs and GGTA1/CMAH/B4GALNT2 triple-edited pigs. Immunohistological analyses demonstrated the downregulation of xenoantigens; however, these multiple gene-edited pigs were genetic mosaics that failed to knock out some xenoantigens. Although mosaicism should be resolved, the electroporation technique could become a primary method for the one-step generation of multiple gene modifications in pigs aimed at improving pig-to-human xenotransplantation. 相似文献