全文获取类型
收费全文 | 10993篇 |
免费 | 474篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 117篇 |
综合类 | 42篇 |
化学工业 | 2201篇 |
金属工艺 | 226篇 |
机械仪表 | 184篇 |
建筑科学 | 601篇 |
矿业工程 | 20篇 |
能源动力 | 281篇 |
轻工业 | 843篇 |
水利工程 | 87篇 |
石油天然气 | 44篇 |
武器工业 | 1篇 |
无线电 | 658篇 |
一般工业技术 | 1452篇 |
冶金工业 | 2847篇 |
原子能技术 | 58篇 |
自动化技术 | 1816篇 |
出版年
2023年 | 75篇 |
2022年 | 154篇 |
2021年 | 332篇 |
2020年 | 184篇 |
2019年 | 200篇 |
2018年 | 270篇 |
2017年 | 233篇 |
2016年 | 313篇 |
2015年 | 233篇 |
2014年 | 341篇 |
2013年 | 624篇 |
2012年 | 483篇 |
2011年 | 615篇 |
2010年 | 428篇 |
2009年 | 491篇 |
2008年 | 454篇 |
2007年 | 412篇 |
2006年 | 343篇 |
2005年 | 294篇 |
2004年 | 269篇 |
2003年 | 259篇 |
2002年 | 189篇 |
2001年 | 137篇 |
2000年 | 139篇 |
1999年 | 191篇 |
1998年 | 858篇 |
1997年 | 525篇 |
1996年 | 386篇 |
1995年 | 238篇 |
1994年 | 200篇 |
1993年 | 223篇 |
1992年 | 75篇 |
1991年 | 84篇 |
1990年 | 85篇 |
1989年 | 97篇 |
1988年 | 83篇 |
1987年 | 71篇 |
1986年 | 79篇 |
1985年 | 75篇 |
1984年 | 62篇 |
1983年 | 52篇 |
1982年 | 40篇 |
1981年 | 48篇 |
1980年 | 53篇 |
1979年 | 35篇 |
1978年 | 41篇 |
1977年 | 71篇 |
1976年 | 138篇 |
1975年 | 44篇 |
1973年 | 37篇 |
排序方式: 共有10000条查询结果,搜索用时 170 毫秒
121.
J Benbassat G Zajicek GJ van Oortmarssen I Ben-Dov MH Eckman 《Canadian Metallurgical Quarterly》1993,13(3):237-244
Cell cultures were derived from adult human brain biopsies [from cortical gray (cultures 9-HB-G and 33-HB-G) and white (culture 14-HB-W) and stroke-injured white matter (culture 33-HB-IW)]. The morphology and growth rate of cultured cells were examined and correlated with the presence of vimentin and glial fibrillary acidic protein (GFAP). The cultures from various brain matters differed in cell morphology and rate of growth but not in GFAP and vimentin staining. Cells of primary and rapidly proliferating cultures were GFAP-negative and vimentin-positive. Spontaneous growth deceleration occurred in culture 14-HB-W within passages 5 to 10 and in cultures 9-HB-G, 33-HB-G, and 33-HB-W within passages 17 to 20. This deceleration, as well as the successive complete growth arrest, were accompanied by an appearance of GFAP-positive cells and an elevated intensity for vimentin staining. We propose that GFAP-positive astrocytes originate from glial precursor cells that migrate from the explants and differentiate under prolonged subcultivation. 相似文献
122.
M Albert C Athanassopoulos LB Auerbach D Bauer R Bolton B Boyd RL Burman I Cohen DO Caldwell BD Dieterle JB Donahue AM Eisner A Fazely FJ Federspiel GT Garvey RM Gunasingha V Highland J Hill R Imlay K Johnston WC Louis A Lu AK Mann J Margulies K McIlhany W Metcalf RA Reeder V Sandberg M Schillaci D Smith I Stancu W Strossman MK Sullivan GJ VanDalen W Vernon YX Wang DH White D Whitehouse D Works Y Xiao S Yellin 《Canadian Metallurgical Quarterly》1995,51(3):R1065-R1069
123.
124.
We discuss the surgical approach used for and outcome in 11 infants (< or =3 years) who were treated at our institution for ependymomas arising in the cerebellar-pontine (C-P) angle. The median age of the group was 19 months (range: 6-26 months). Of these 11 patients, the initial surgery for 8 was performed at our center and achieved a gross total resection (GTR) in 4 patients and a subtotal resection (STR) in the remaining 4. The 3 patients who had tumor debulking performed elsewhere were subsequently referred to our institution and had definitive surgery after receiving 3-4 courses of chemotherapy; one of these children had a GTR, whereas the remaining 2 had an STR. During the immediate postoperative period, 9 patients had cranial nerve deficits that necessitated placement of a tracheostomy and a gastrostomy feeding tube; these were discontinued in 6 of the 9 patients as the deficits resolved. The majority of the permanent cranial nerve deficits involved the sixth and seventh cranial nerves. Of the 11 patients, 4 have died (progressive disease, n = 1; accidental death, n = 2; withdrawal of life support, n = 1); the remaining 7 patients are alive, with a median follow-up of 37 months (range: 20-73 months). Aggressive surgical resection for tumors arising in the C-P region is associated with postoperative deficits, which resolve over time with appropriate supportive care. This approach may increase the number of children in whom GTR is achieved, thereby potentially increasing the cure rate for these patients. 相似文献
125.
126.
We present a technique for approximating isotropic BRDFs and precomputed self-occlusion that enables accurate and efficient prefiltered environment map rendering. Our approach uses a nonlinear approximation of the BRDF as a weighted sum of isotropic Gaussian functions. Our representation requires a minimal amount of storage, can accurately represent BRDFs of arbitrary sharpness, and is above all, efficient to render. We precompute visibility due to self-occlusion and store a low-frequency approximation suitable for glossy reflections. We demonstrate our method by fitting our representation to measured BRDF data, yielding high visual quality at real-time frame rates. 相似文献
127.
128.
129.
The role of gut intraepithelial lymphocytes (IEL) in immunity to cryptosporidial infection was investigated with a murine infection model involving Cryptosporidium muris. Oocyst shedding was monitored in severe combined immunodeficiency (SCID) mice infected with C. muris following intravenous injection of mesenteric lymph node (MLN) cells or intestinal IEL from BALB/c donor mice which were naive or previously infected with C. muris. SCID mice receiving no lymphoid cells developed chronic infections and excreted large numbers of oocysts until the end of the experiment. SCID mice injected with IEL from immune animals, however, were able to overcome the infection, and furthermore, these animals produced fewer oocysts and recovered sooner than ones which received IEL or MLN cells from naive BALB/c donors. Similar levels of protection were obtained in SCID mice injected with either 2 X 10(6) IEL or MLN cells from immune donor mice. Depletion of CD4+ cells from immune IEL, however, abrogated the ability to transfer immunity to SCID mice, while depletion of CD8+ cells only marginally reduced the protective capacity of immune IEL. Finally, control SCID mice which received no lymphocytes had < or = 1% CD4+ cells in the IEL from the small intestine, whereas the IEL from SCID mice recovered from infection, as a result of injection with immune IEL, contained 15% CD4+ cells. Thus, the ability to control C. muris infection correlated with the presence of the protective CD4+ cells in the gut epithelium. 相似文献
130.
Weijing He Haiyan Li Siu-Lun Fok J. Derek Jackson Jan R. Wright 《Nuclear Engineering and Design》2007,237(12-13):1437-1444
A series of quench tests on hollow cylindrical specimens made of the machinable ceramic, Pyrophyllite, has been performed. The specimens consistently fractured with two diametrically opposite longitudinal cracks. Finite element analysis indicates that the primary crack occurred at the stage when the strain energy of the cylinder reached its maximum during the thermal transient process, while the secondary crack was caused by stress waves generated following the primary crack. This is supported by experimental observation of the time of fracture and the crack morphology. The work reported here helps to shed light on the fracture criterion for brittle cylindrical components under transient thermal and dynamic loadings. 相似文献