全文获取类型
| 收费全文 | 4448篇 |
| 免费 | 13篇 |
学科分类
| 工业技术 | 4461篇 |
出版年
| 2023年 | 24篇 |
| 2022年 | 27篇 |
| 2021年 | 45篇 |
| 2020年 | 23篇 |
| 2019年 | 37篇 |
| 2018年 | 31篇 |
| 2017年 | 32篇 |
| 2016年 | 57篇 |
| 2015年 | 39篇 |
| 2014年 | 63篇 |
| 2013年 | 111篇 |
| 2012年 | 70篇 |
| 2011年 | 150篇 |
| 2010年 | 98篇 |
| 2009年 | 113篇 |
| 2008年 | 140篇 |
| 2007年 | 93篇 |
| 2006年 | 90篇 |
| 2005年 | 82篇 |
| 2004年 | 79篇 |
| 2003年 | 105篇 |
| 2002年 | 101篇 |
| 2001年 | 97篇 |
| 2000年 | 67篇 |
| 1999年 | 158篇 |
| 1998年 | 627篇 |
| 1997年 | 349篇 |
| 1996年 | 261篇 |
| 1995年 | 164篇 |
| 1994年 | 152篇 |
| 1993年 | 121篇 |
| 1992年 | 63篇 |
| 1991年 | 75篇 |
| 1990年 | 76篇 |
| 1989年 | 61篇 |
| 1988年 | 59篇 |
| 1987年 | 49篇 |
| 1986年 | 51篇 |
| 1985年 | 40篇 |
| 1984年 | 39篇 |
| 1983年 | 29篇 |
| 1982年 | 20篇 |
| 1981年 | 26篇 |
| 1980年 | 41篇 |
| 1979年 | 26篇 |
| 1978年 | 24篇 |
| 1977年 | 38篇 |
| 1976年 | 76篇 |
| 1973年 | 13篇 |
| 1972年 | 10篇 |
排序方式： 共有4461条查询结果，搜索用时 15 毫秒
91.
T. Yokono K. Murakami Y. Sanada S. Shimokawa E. Yamada 《Journal of Materials Science》1987,22(2):638-642
We have proposed a model of carbon microbead formation from the mixture of coal-tar pitch and n-paraffin under mild conditions, supported by results obtained by high-temperature and high-pressure1H nuclear magnetic resonance and electron spin resonance in conjunction with thermogravimetric and differential thermal analysis. The data obtained by different techniques are in good agreement with each other. 相似文献
92.
Atsushi Yamada Kenji Shimada Takayuki Itoh 《International journal for numerical methods in engineering》1999,46(8):1221-1236
In the initial phase of structural part design, wire‐frame models are sometimes used to represent the shapes of curved surfaces. Finite Element Analysis (FEA) of a curved surface requires a well shaped, graded mesh that smoothly interpolates the wire frame. This paper describes an algorithm that generates such a triangular mesh from a wire‐frame model in the following two steps: (1) construct a triangulated surface by minimizing the strain energy of the thin‐plate‐bending model, and (2) generate a mesh by the bubble meshing method on the projected plane and project it back onto the triangulated surface. Since the mesh elements are distorted by the projection, the algorithm generates an anisotropic mesh on the projected plane so that an isotropic mesh results from the final projection back onto the surface. Extensions of the technique to anisotropic meshing and quadrilateral meshing are also discussed. The algorithm can generate a well‐shaped, well‐graded mesh on a smooth curved surface. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
93.
M Dubuc M Talajic D Roy B Thibault TK Leung PL Friedman 《Canadian Metallurgical Quarterly》1998,2(3):285-292
BACKGROUND AND PURPOSE: Accurate contouring of the clinical target volume (CTV) is a fundamental prerequisite for successful conformal radiotherapy of prostate cancer. The purpose of this study was to investigate intra- and inter-observer variability in contouring prostate (P) and seminal vesicles (SV) and its impact on conformal treatment planning in our working conditions. MATERIALS AND METHODS: Inter-observer variability was investigated by asking five well-trained radiotherapists of contouring on CT images the P and the SV of six supine-positioned patients previously treated with conformal techniques. Short-term intra-observer variability was assessed by asking the radiotherapists to contour the P and SV of one patient for a second time, just after the first contouring. The differences among the inserted volumes were considered for both intra- and inter-observer variability. Regarding intra-observer variability, the differences between the two inserted contours were estimated by taking the relative differences in correspondence to the CT slices on BEV plots (antero-posterior and left-right beams). Concerning inter-observer variability, the distances between the internal and external envelopes of the inserted contours (named projected diagnostic uncertainties or PDUs) and the distances from the mean inserted contours (named mean contour distances or MCDs) were measured from BEV plots (i.e. parallel to the CT slices). RESULTS: Intra-observer variability was relatively small (the average percentage variation of the volume was approximately 5%; SD of the differences measured on BEV plots within 1.8 mm). Concerning inter-observer variability, the percentage SD of the inserted volumes ranged from 10 to 18%. Differences equal to 1 cm in the cranio-caudal extension of P + SV were found in four out of six patients. The largest inter-observer variability was found when considering the anterior margin in the left-right beam of P top (MCD = 7.1 mm, 1 SD). Relatively high values for MCDs were also found for P bottom, for the posterior and lateral margins of P top (2.6 and 3.1 mm, respectively, I SD) and for the anterior margin of SV (2.8 mm, 1 SD). Relatively small values were found for P central (from 1.4 to 2.0 mm, 1 SD) and the posterior margin of SV (1.5 mm, 1 SD). CONCLUSIONS: The application of larger margins taking inter-observer variability into account should be taken into consideration for the anterior and the lateral margins of SV and P top and for the lateral margin of P. The impact of short-term intra-observer variability does not seem to be relevant. 相似文献
94.
NE Skakkebaek E Rajpert-De Meyts N J?rgensen E Carlsen PM Petersen A Giwercman AG Andersen TK Jensen AM Andersson J Müller 《Canadian Metallurgical Quarterly》1998,106(1):3-11; discussion 12
Why is there a small peak of germ cell tumours in the postnatal period and a major peak in young age, starting at puberty? And, paradoxically, small risk in old age, although spermatogenesis is a lifelong process? Why is this type of cancer more common in individuals with maldeveloped gonads, including undescended testis, gonadal dysgenesis and androgen insensitivity syndrome? Why has there, during the past 50 years, been a quite dramatic increase in testicular cancer in many developed countries? These are just a few of many questions concerning testicular cancer. However, the recent progress in research in the early stages of testicular cancer (carcinoma in situ testis (CIS)) allows us to begin to answer some of these questions. There is more and more evidence that the CIS cell is a gonocyte with stem cell potential, which explains why an adult man can develop a non-seminoma, which is a neoplastic caricature of embryonic growth. We consider the possibility that CIS cells may loose their stem cell potential with ageing. Along these lines, a seminoma is regarded a gonocytoma where the single gonocytes have little or no stem cell potential. The Sertoli and Leydig cells, which are activated postnatally and during and after puberty, may play a crucial role for both the development of the CIS gonocyte and progression of the neoplasm to invasiveness. The reported increase in testicular cancer is not the only sign that male reproductive health is at risk. There are reports that undescended testis and hypospadias have become more common. Also semen quality has deteriorated, at least in some countries. The epidemiological evidence suggests that environmental factors may play a role. Are the environmental hormone disrupters (e.g. DDT, PCB, nonylphenol, bisphenol A) to be blamed for the apparently synchronised deterioration in these aspects of male reproductive health? 相似文献
95.
1. To examine whether insulin resistance in vivo is manifest equally in both muscle and adipose tissues, we measured arteriovenous glucose and lactate fluxes across forearm (muscle) and abdominal subcutaneous (adipose) tissue in nine obese, glucose-intolerant subjects and 13 non-obese subjects of similar age and sex. 2. Compared with non-obese subjects, the forearm of the obese subjects was resistant to insulin stimulation of glucose uptake after a mixed meal. In contrast, adipose tissue showed little evidence of insulin stimulation of glucose uptake, and adipose tissue in subjects in both normal and obese groups behaved very similarly (assessed per 100 g of tissue). 3. For lactate flux, adipose tissue behaved very similarly (per 100 g of tissue) in obese and non-obese subjects, and was a consistent lactate exporter. 4. We conclude that insulin resistance of glucose uptake observed in the forearm of obese subjects is not evident in adipose tissue. Adipose tissue glucose uptake in obese, insulin-resistant subjects is similar to that in lean control subjects, although it occurs at elevated circulating insulin and glucose concentrations. 相似文献
96.
97.
An automated optical mass storage system (optical MSS) with high-speed magnetooptical (MO) disk drives has been developed. It features a high data transfer rate for writing with the use of the 130-mm ISO standard MO disk, and disk cartridges with high storage efficiency. As the key device, a high-speed MO disk drive has been developed. It provides a high-speed data writing capability of about ten times that of conventional MO disk drives. The optical MSS provides a data transfer rate for reading and writing of 2.1 MB/s, a storage capacity of 250 GB to 1 TB, and an average cartridge handling time of 5 s. From performance simulations, the optical MSS is proved to be applicable to a low-traffic random-access file that stores multimedia data and a high-speed direct-access storage device (DASD) backup file 相似文献
98.
Xiang PH Asanuma S Yamada H Inoue IH Sato H Akoh H Sawa A Ueno K Yuan H Shimotani H Kawasaki M Iwasa Y 《Advanced materials (Deerfield Beach, Fla.)》2011,23(48):5822-5827
A prototype Mott transistor, the electric double layer transistor with a strained CaMnO(3) thin film, is fabricated. As predicted by the strain phase diagram of electron-doped manganite films, the device with the compressively strained CaMnO(3) exhibits an immense conductivity modulation upon applying a tiny gate voltage of 2 V. 相似文献
99.
Hasegawa H. Nagaishi H. Kominami S. Yamada H. Nishino T. 《Applied Superconductivity, IEEE Transactions on》1995,5(4):3504-3510
This paper describes the development of a dc-powered Josephson logic family that uses hybrid unlatching flip-flop logic elements (Huffles). The Huffle circuit used in this study is modified by adding a parallel resistor to the original Hebard-type Huffle circuit. Analysis of the circuit's operation shows that the undesirable hung-up phenomena are prevented by this modification. Based on the result of the analysis, the circuit's parameters are derived and a typical operating margin of ±26% is obtained. Besides AND/OR operations using a threshold logic operation, two-input exclusive OR (XOR), two-input multiplexor (MUX), and three-input majority (MAJ) operations are realized using a Huffle gate in which 2-Josephson-interferometers (2JI) in the standard Huffle gate are replaced by stacked-2JI's. Thus, a Huffle logic family, formed from NOT, AND, OR, XOR, MUX, MAJ, and flip-flop (FF), are constructed. By using this Huffle logic family, a 6-b arithmetic logic operating unit (ALU), a 6-b analog-to-digital converter (ADC), and a 6-b gray-to-binary converter (GBC) have been successfully operated. During high-speed testing, a 1-b comparator was operated up to an input bandwidth of 6 GHz 相似文献
100.
