全文获取类型
收费全文 | 701399篇 |
免费 | 9657篇 |
国内免费 | 2244篇 |
专业分类
电工技术 | 12515篇 |
综合类 | 690篇 |
化学工业 | 104987篇 |
金属工艺 | 25567篇 |
机械仪表 | 20142篇 |
建筑科学 | 17504篇 |
矿业工程 | 2708篇 |
能源动力 | 19679篇 |
轻工业 | 65217篇 |
水利工程 | 6588篇 |
石油天然气 | 10895篇 |
武器工业 | 41篇 |
无线电 | 82735篇 |
一般工业技术 | 132991篇 |
冶金工业 | 137476篇 |
原子能技术 | 12759篇 |
自动化技术 | 60806篇 |
出版年
2021年 | 6051篇 |
2020年 | 4444篇 |
2019年 | 5629篇 |
2018年 | 9461篇 |
2017年 | 9293篇 |
2016年 | 9858篇 |
2015年 | 6979篇 |
2014年 | 11582篇 |
2013年 | 32684篇 |
2012年 | 18850篇 |
2011年 | 26421篇 |
2010年 | 20687篇 |
2009年 | 23209篇 |
2008年 | 23989篇 |
2007年 | 23609篇 |
2006年 | 21012篇 |
2005年 | 19182篇 |
2004年 | 18403篇 |
2003年 | 18178篇 |
2002年 | 17178篇 |
2001年 | 17421篇 |
2000年 | 16125篇 |
1999年 | 17235篇 |
1998年 | 43994篇 |
1997年 | 30701篇 |
1996年 | 23367篇 |
1995年 | 17598篇 |
1994年 | 15316篇 |
1993年 | 15008篇 |
1992年 | 10755篇 |
1991年 | 10104篇 |
1990年 | 9815篇 |
1989年 | 9462篇 |
1988年 | 8906篇 |
1987年 | 7676篇 |
1986年 | 7504篇 |
1985年 | 8649篇 |
1984年 | 8021篇 |
1983年 | 7151篇 |
1982年 | 6710篇 |
1981年 | 6856篇 |
1980年 | 6415篇 |
1979年 | 6198篇 |
1978年 | 5864篇 |
1977年 | 7059篇 |
1976年 | 9170篇 |
1975年 | 5060篇 |
1974年 | 4743篇 |
1973年 | 4941篇 |
1972年 | 3928篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
131.
Dissolved organic carbon (DOC) dynamics were investigated over a two year period in the Upper Rhǒne River to examine the role of side-arms in providing DOC to the main channel in relation to discharge fluctuations, especially floods. Concentrations of DOC are shown to remain low in space and in time (average 1.5 mg ?1) and to be more related to global hydrological events (precipitation) than to any local flushing for backwaters during floods. The results do not support the general assumption that side-arms are the providers of DOC to the main channel. 相似文献
132.
A case of traumatic extracranial vertebral arterial dissection leading to vertebrobasilar thrombosis and respiratory compromise requiring mechanical ventilation was managed with intraarterial thrombolysis and stenting of the vertebral intimal dissection. In contrast to similar, previously reported cases, this critically ill patient made a full recovery, returning to his job as a secondary school teacher. 相似文献
133.
M Camilleri 《Canadian Metallurgical Quarterly》1996,25(2):361-378
Gastrointestinal symptoms are often encountered in patients with diabetes mellitus. Symptoms may arise in any region of the alimentary tract; common symptoms are heartburn, nausea, vomiting, diarrhea, constipation, fecal incontinence, and abdominal pain. This article reviews practical approaches to the identification of the pathophysiologic mechanisms involved in diabetic enteropathies and their complications and briefly outlines strategies to treat these symptoms. Particular emphasis is placed on applied physiologic tests and the choice of pharmacotherapy (e.g., cisapride, erythromycin, or octeotide). The current role of pancreatic transplantations also is briefly reviewed. 相似文献
134.
C Wittekind 《Canadian Metallurgical Quarterly》1996,121(6):435-441
A subpopulation of rabbit polyclonal anti-idiotypic antibody (anti-Id) was previously produced to a murine monoclonal antibody (mAb) (M1875) specific for the bluetongue virus core protein VP7. In this report, mimicry of VP7 by this anti-Id (designated RAb2-A) was functionally analyzed through immunization of Balb/c mice with RAb2-A or purified VP7. Animals immunized with RAb2-A were able to produce an M1875-like Ab3 antibody response with idiotype and epitope specificity resembling that of M1875 without subsequent exposure to the nominal antigen. This conclusion was supported by experiments showing that the RAb2-A-induced Ab3 antibodies (i) reacted specifically with the immunizing anti-Id; (ii) were capable of binding VP7; (iii) inhibited M1875 from binding to VP7; and (iv) inhibited M1875 from binding to RAb2-A. Similarly, mice immunized with purified VP7 also produced antibodies that exhibited characteristics such as idiotype and epitope specificity in common with M1875. No antibody response to VP7 was detected in control groups of mice immunized with either normal rabbit IgG or BHK-21 cell components. Therefore, it can be concluded that rabbit anti-Id RAb-2-A mimics an M1875-defined VP7 epitope sufficiently to function as a surrogate antigen for inducing an anti-bluetongue virus response. 相似文献
135.
W. Lim C. K. Wang 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1996,370(2-3):568-572
The one-dimensional (1D) position-sensitive superheated-liquid-droplet dosimeter (SLDD) has been fabricated and tested in the laboratory. The 1D SLDD is fabricated from a 9.525-mm OD, 6.35-mm ID, 20-cm long, Plexiglas-walled tube filled with a mixture of superheated-liquid Freon droplets and host medium glycerol. Washer-shaped piezoelectric acoustic transducers are positioned at both ends of the tube; they determine the number and positions of the acoustic events when the superheated-liquid droplets evaporate upon neutron irradiation. The SLDD is irradiated with the 137Cs and 60Co γ-sources, as well as 252Cf neutron source to test for its radiation response and spatial resolution. The SLDD based on the Freon-134a superheated-liquid droplets operating at 20°C and 1 atm is found to be ideal for measuring absorbed neutron dose. This study also proves that the positions of the radiation-induced nucleation acoustic events can be linearly determined from the differences in the transmission times received by the acoustic transducers on the 1D SLDD. The spatial resolution of the neutron depth-dose is 1 mm due the finite response time (1 μs) of the piezoelectric acoustic transducers. 相似文献
136.
In a prospective study we found good results concerning postoperative complications (21%), perioperative lethality (3.2%) and lethality during hospital stay (6.5%) after implantation of dynamic hip screws (DHS) in patients with per- and subtrochanteric fractures of the femur. The ability to walk, as well as housing and social care postoperatively and follow-up for at least six months after dismissal demonstrates the importance of these fractures for the elderly. One of three patients needs professional care, 21% at home, 13% in nursing homes. Six months after operation the lethality is nearly 20%, i.e. three times higher than in hospital. These are the essential data for all techniques of osteosynthesis used in patients with these fractures, which could only be documented in prospective studies. 相似文献
137.
138.
139.
This article presents the results of a pilot-study conducted on a small sample of women with breast cancer and the members of their social support system. The purpose was to determine the potential link between the mental health of the breast cancer patient and their support system. Mental health was assessed with the SCL-90-R (Derogatis, 1977), a self-report scale composed of 90 items divided into nine categories, offering three global indicators of distress: the Global Severity Index (GSI); the Positive Symptom Distress Index (PSDI), and the Positive Symptom Total (PST). The SCL-90-R was distributed to a sample of 14 subjects: seven women treated for breast cancer and seven significant others (social support). The results led to the definition of symptoms such as hostility, phobic anxiety and psychosis specific to either the woman or the support system. 相似文献
140.
M.E.W. Eggenkamp V. A. Shvarts R. Blaauwgeers A. Storm R. Jochemsen G. Frossati 《Journal of Low Temperature Physics》1998,110(1-2):299-304
This paper focuses on the hydrodynamics of third sound on a superfluid
3
He film. We solve the hydrodynamical equations in the limit of thick films with weak interaction with the substrate. The surface tension at the free interface is shown to have a large effect on the third sound velocity and on the attenuation for frequencies larger than 1Hz. In the case of a diffusely scattering substrate a ripplon-like dispersion relation is found for this frequency range. 相似文献