全文获取类型
收费全文 | 1848篇 |
免费 | 66篇 |
国内免费 | 19篇 |
专业分类
电工技术 | 102篇 |
综合类 | 2篇 |
化学工业 | 490篇 |
金属工艺 | 58篇 |
机械仪表 | 51篇 |
建筑科学 | 26篇 |
能源动力 | 87篇 |
轻工业 | 106篇 |
水利工程 | 3篇 |
石油天然气 | 1篇 |
无线电 | 156篇 |
一般工业技术 | 322篇 |
冶金工业 | 302篇 |
原子能技术 | 50篇 |
自动化技术 | 177篇 |
出版年
2023年 | 14篇 |
2022年 | 55篇 |
2021年 | 63篇 |
2020年 | 33篇 |
2019年 | 35篇 |
2018年 | 43篇 |
2017年 | 33篇 |
2016年 | 55篇 |
2015年 | 30篇 |
2014年 | 61篇 |
2013年 | 106篇 |
2012年 | 78篇 |
2011年 | 119篇 |
2010年 | 75篇 |
2009年 | 83篇 |
2008年 | 85篇 |
2007年 | 61篇 |
2006年 | 60篇 |
2005年 | 63篇 |
2004年 | 42篇 |
2003年 | 46篇 |
2002年 | 44篇 |
2001年 | 31篇 |
2000年 | 31篇 |
1999年 | 38篇 |
1998年 | 119篇 |
1997年 | 85篇 |
1996年 | 58篇 |
1995年 | 45篇 |
1994年 | 44篇 |
1993年 | 35篇 |
1992年 | 14篇 |
1991年 | 19篇 |
1990年 | 15篇 |
1989年 | 11篇 |
1988年 | 8篇 |
1987年 | 11篇 |
1986年 | 5篇 |
1985年 | 13篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 3篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 7篇 |
1976年 | 13篇 |
1972年 | 2篇 |
1969年 | 2篇 |
排序方式: 共有1933条查询结果,搜索用时 12 毫秒
991.
Susumu Matsuzaki Kiyoshi Hashimoto Takahiro Tomiku Hitoshi Fujimoto Kenji Ichimura 《Fullerenes, Nanotubes and Carbon Nanostructures》1995,3(1):59-68
A new absorption band assigned to C60- was observed around 1000 nm in the electronic spectra of (BEDT-TTF)2C60 and (ferrocene)2C60 at high pressures. The result suggests an increase in the ionicity of the complexes with increasing pressure. 相似文献
992.
R Uranishi Y Nikaido T Eguchi H Bessho T Fujimoto T Inui 《Canadian Metallurgical Quarterly》1996,36(7):458-461
In order to clarify the pathogenesis of hemorrhagic fever with renal syndrome (HFRS), we detected HFRS virus structural proteins expressed in perepheral blood mononuclear cells (PBMC) by using immunohistochemical technique. Meanwhile we also determined plasma endothelin (ET), substance P (SP) and some sensitive markers of renal function with radioimmunoassay. The result showed that in HFRS patients, from the day of admission up to the thirteenth day of illness, the antigens of HFRS virus membrane protein (MP) and nucleocapsid (NP) could simultaneously be found in PBMC, though their expressive degree gradually decreased when the condition of the patients became better. Based on the external appearance and nucleus pattern of PBMC we recognized the MP and NP positive cells were mainly monocytes among which only a few presented faint IgM and C3 stain. On admission there was difference in expressive intensity between MP and NP. The MP expressive intensity was in parallel with plasma ET/SP ratio, the general condition and the severity of renal damage. These data suggest that HFRS virus can invade PBMC, replicate in them, and express their structural proteins. MP may be related with the pathogenesis of HFRS virus and the increase of plasma ET/SP ratio may be an important factor aggravating kidney injury. 相似文献
993.
High-speed InP-InGaAs heterojunction phototransistors (HPT's) with a base terminal (three-terminal HPT's) have been fabricated. These HPT's have nonalloyed electrodes functioning as reflectors and a configuration in which light is incident through the substrate. These features lead to an increase in quantum efficiency in spite of the thin base and collector light-absorbing layers. Optical gain dependence on collector current is weak because of the low recombination current at the emitter-base interface. Maximum optical-gain cutoff frequencies of 22 and 14 GHz are obtained for a 3×3-μm2 emitter HPT illuminated by 1.3- and 1.55-μm light, respectively. This HPT has the capability of operating as a high-speed heterojunction bipolar transistor (HBT) as well. A current-gain cutoff frequency (fT) of 128 GHz is obtained for a 3×9-μm2 emitter HBT fabricated on the same wafer. Equivalent circuit analysis, in which all the components are determined by measuring both the electrical and optical characteristics of a three-terminal HPT, shows good agreement with experimental results 相似文献
994.
K Fujimoto H Machidori R Iwakiri K Yamamoto J Fujisaki T Sakata P Tso 《Canadian Metallurgical Quarterly》1993,608(2):233-237
To characterize the anorectic effect of apolipoprotein A-IV (apo A-IV), we examined the effect of apo A-IV on the patterns of feeding, drinking and ambulation of rats fed ad libitum. A single dose of 200, 135 or 60 micrograms was infused intravenously through a chronically indwelling right atrial catheter just before the dark period. Apo A-IV suppressed food intake by decreasing meal size, but did not affect the interval between meals, the speed of eating, or the latency to eat the first meal after infusion. The anorectic effect of apo A-IV was dose-dependent and was effective for about 3 h after the infusion. The anorectic effect of apo A-IV is specific because inactivation of apo A-IV abolishes its anorectic effect. The anorectic effect of apo A-IV is not shared by apo A-I. Apo A-IV had no effect on drinking behavior or ambulatory activity. The results seem to indicate that apo A-IV specifically decreases the meal size, which supports our hypothesis that apo A-IV may act as a physiological signal for satiation after the ingestion of a lipid meal. 相似文献
995.
Poly(N-isopropylacrylamide) (PNIPAM) hydrogel microspheres were prepared by precipitation polymerization above the polymer's lower critical solution temperature (LCST) in water. The hydrodynamic size of PNIPAM microspheres exhibited a thermo-sensitive change around the LCST. In order to obtain information about the interface of the hydrogels, contact angle measurement, protein adsorption, and fluorescence analysis were performed. Contact angle measurement and protein adsorption showed a gradual change around the LCST similar to the change of the hydrodynamic size. However, fluorescence study exhibited a sharp change at the LCST. In addition, a quenching experiment was employed to elucidate the location of the fluorescent probes. In the PNIPAM latex, the probes were located where they were less quenchable as compared to the PNIPAM solution. It seems probable that the probes can penetrate into the crosslinked PNIPAM hydrogel and might reflect the inner environment of the hydrogel. The effect of salt on thermo-sensitive behaviour was also detected by fluorescence analysis. On the other hand, the hydrogel microsphere prepared from poly(acryloyl pyrrolidine) (PAPr) showed a gradual change in fluorescence with temperature. 相似文献
996.
The paper proposes a function of active path selection to the destination by users and implements the function into the FTP application by using the routing header defined in IPv6 specifications. It also develops the "support system for quality selection", which supports the selection by providing information on each path, experimentally. The details of the function and an implementation of the application also are described. 相似文献
997.
Richard M. Fujimoto Ioanis Nikolaidis C. Anthony Cooper 《Discrete Event Dynamic Systems》1995,5(2-3):115-140
The simulation of high-speed telecommunication systems such as ATM (Asynchronous Transfer Mode) networks has generally required excessively long run times. This paper reviews alternative approaches using parallelism to speed up simulations of discrete event systems, and telecommunication networks in particular. Subsequently, a new simulation method is introduced for the fast parallel simulation of a common network element, namely, a work-conserving finite capacity statistical multiplexer of bursty ON/OFF sources arriving on input links of equal peak rate. The primary performance measure of interest is the cell loss ratio, due to buffer overflows. The proposed method is based on two principal techniques: (1) the derivation of low-level (cell level) statistics from a higher level (burst level) simulation and (2) parallel execution of the burst level simulation program. For the latter, atime-division parallel simulation method is used where simulations operating at different intervals of simulated time are executed concurrently on different processors. Both techniques contribute to the overall speedup. Furthermore, these techniques support simulations that are driven by traces of actual network traffic (trace-driven simulation), in addition to standard models for source traffic. An analysis of this technique is described, indicating that it offers excellent potential for delivering good performance. Measurements of an implementation running on a 32 processor KSR-2 multiprocessor demonstrate that, for certain model parameter settings, the simulator is able to simulate up to 10 billion cell arrivals per second of wallclock time. 相似文献
998.
Masako Omori Tomoyuki Watanabe Jo Takai Hiroki Takada Masaru Miyao 《Behaviour & Information Technology》2002,21(5):313-316
Although mobile phones (MPs) have become important IT devices, there are few studies on the visibility of MPs for elderly people. Using six types of MPs, we analysed the reading performance among elderly people who read 11 numerics on each MP. The subjects were 130 people aged 18 to 86 years, including 60 people over 60 years of age. The subjects' visual functions of cataract cloudiness (CC) and near vision for a 50 cm distant target (NV) were measured. In a twoway ANOVA, two kinds of dependant variables, reading speed (RS) and the number of errors in reading (Error) were used for the subjects' reading performance. Two independent variables were taken from five variables. Each time one variable was fixed as the type of MPs. The other was taken as either age, CC, NV, individual history on MP operation or room illuminance (RI). Eventually, 10 ANOVAs were calculated. Significant differences were found in all ANOVAs except that for RI. We undertook a multiple logistic regression analysis. Independent variables of CC, NV and vertical length of characters (VL) and two kinds of dependent variables, RS and Error, were used. Visual functions and a short VL were related to slow RS and increased Errors. 相似文献
999.
K Tsuganezawa N Kiyokawa Y Matsuo F Kitamura N Toyama-Sorimachi K Kuida J Fujimoto H Karasuyama 《Canadian Metallurgical Quarterly》1998,92(11):4317-4324
Three novel monoclonal antibodies (MoAbs) have been established that recognize distinct epitopes of a human pre-B-cell receptor (pre-BCR) composed of a mu heavy (muH) chain and a lambda5/VpreB surrogate light (SL) chain. HSL11 reacts with lambda5 whereas HSL96 reacts with VpreB. Intriguingly, HSL2 does not bind to each component of the pre-BCR but does bind to the completely assembled pre-BCR complex. Flow cytometric analyses with cytoplasmic staining of a panel of human cell lines showed that HSL11 and HSL96 specifically stained cell lines derived from the pro-B and pre-B-cell stages of B-cell development. In contrast, HSL2 stained exclusively cell lines derived from the pre-B-cell stage. These results prompted us to explore the possibility of clinical application of these MoAbs for the determination of the cell lineage and developmental stage of acute lymphoblastic leukemia (ALL). Whereas none of mature B-lineage ALLs (B-ALLs), T-lineage ALLs (T-ALLs), and acute myeloid leukemias analyzed were stained in the cytoplasm with these three MoAbs, the vast majority of non-B- and non-T-ALLs (53 out of 56 cases) were found positive for either lambda5, Vpre-B, or both in their cytoplasm. Among these 53 cytoplasmic SL chain-positive ALLs, 19 cases were also positive for cytoplasmic muH chain, indicative of pre-B-cell origin. Interestingly, 6 out of these 19 pre-B-ALL cases were found negative for cytoplasmic staining with HSL2. From these results, we propose a novel classification of B-ALL in which five subtypes are defined on the basis of the differential expression of SL chain, muH chain, pre-BCR, and light chain along the B-cell development. 相似文献
1000.
T Obara T Okamoto Y Ito T Yamashita M Kawano T Nishi M Tani K Sato H Demura Y Fujimoto 《Canadian Metallurgical Quarterly》1993,114(6):1040-8; discussion 1048-9
BACKGROUND: The aim of this study was to characterize patients with pulmonary metastasis of parathyroid carcinoma and to evaluate the long-term effect of surgical and medical therapy. METHODS: Seven patients with pulmonary metastasis of parathyroid carcinoma were treated between 1980 and 1992. Six patients underwent resection of pulmonary metastases, and one patient has had long-term bisphosphonate therapy alone. Bisphosphonate was also given before or after operation to three patients. RESULTS: Two patients underwent a unilateral thoracotomy for a single pulmonary lesion, and four other patients with multiple lesions underwent staged bilateral thoracotomies. The postoperative serum calcium level returned to normal after each thoracotomy in three patients who were alive and well 3, 8, and 12 years after the first thoracotomy. Hypercalcemia persisted in the other three patients. In two of the patients, bisphosphonate therapy was also unable to control hypercalcemia. In one patient the serum calcium level has been maintained in the 13 mg/dl range by bimonthly bisphosphonate therapy alone for 3 years. CONCLUSIONS: The aggressive surgical approach to pulmonary metastasis of parathyroid carcinoma was shown to be effective for palliation in selected patients. Bisphosphonate therapy is an alternative to resection but has only a temporary calcium-lowering effect. 相似文献