全文获取类型
收费全文 | 6150篇 |
免费 | 389篇 |
国内免费 | 4篇 |
学科分类
工业技术 | 6543篇 |
出版年
2024年 | 13篇 |
2023年 | 60篇 |
2022年 | 115篇 |
2021年 | 189篇 |
2020年 | 140篇 |
2019年 | 149篇 |
2018年 | 237篇 |
2017年 | 218篇 |
2016年 | 214篇 |
2015年 | 188篇 |
2014年 | 242篇 |
2013年 | 467篇 |
2012年 | 385篇 |
2011年 | 405篇 |
2010年 | 283篇 |
2009年 | 257篇 |
2008年 | 278篇 |
2007年 | 270篇 |
2006年 | 203篇 |
2005年 | 160篇 |
2004年 | 143篇 |
2003年 | 112篇 |
2002年 | 106篇 |
2001年 | 92篇 |
2000年 | 70篇 |
1999年 | 74篇 |
1998年 | 504篇 |
1997年 | 273篇 |
1996年 | 195篇 |
1995年 | 102篇 |
1994年 | 85篇 |
1993年 | 77篇 |
1992年 | 25篇 |
1991年 | 14篇 |
1990年 | 18篇 |
1989年 | 16篇 |
1988年 | 14篇 |
1987年 | 22篇 |
1986年 | 17篇 |
1985年 | 15篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1981年 | 12篇 |
1980年 | 8篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1976年 | 22篇 |
1975年 | 5篇 |
1973年 | 3篇 |
1968年 | 3篇 |
排序方式: 共有6543条查询结果,搜索用时 0 毫秒
31.
RM Mu?oz LA Pulpón M Yebra J Segovia M San Martín C Salas 《Canadian Metallurgical Quarterly》1998,17(11):801-806
The fibrinolytic capacity of patients with acute myocardial infarction (AMI) is known to be impaired. The primary regulatory element of the fibrinolytic system is plasminogen activator inhibitor (PAI). It has been previously observed that there are 2 peaks in the plasma PAI level of AMI patients at 4h and 16h after thrombolytic therapy with recombinant tissue plasminogen activator (rtPA). Lanoteplase/SUN9216 is a mutant tPA with a biological half-life longer than that of rtPA. Thrombolytic therapy with mutant tPA or rtPA was carried out consecutively in 21 patients with AMI (8 patients as the mutant tPA group, and 13 patients as the rtPA group). The recanalization time of the mutant tPA group was significantly faster than that of the rtPA group (16.1 +/- 3.9 min vs 39.6 +/- 4.8 min, p<0.01). The PAI activity at 4h after the initiation of thrombolysis was significantly lower in the mutant tPA group than in the rtPA group (8.74 +/- 5.46IU/L vs 26.74 +/- 3.35 IU/L, p<0.01). There was a one mild peak in serial plasma PAI activity levels 24h after the initiation of thrombolysis. The results suggest that thrombolytic therapy with mutant tPA reduced the impairment of fibrinolytic capacity. The mutant tPA gives faster recanalization and lower PAI activity after successful thrombolysis, compared with rtPA. 相似文献
32.
33.
34.
This study was designed to examine whether cyclosporine (CyA) acts on the endocrine system by modifying the pulsatile secretion pattern of prolactin and LH. Both pituitary-grafted and sham-operated rats were submitted to a subcutaneous vehicle or CyA (5 mg/kg) treatment daily for 10 days beginning on the day of surgery. Pituitary grafting and/or CyA administration changed the pulsatile pattern of prolactin observed in sham-operated animals. The mean values of serum prolactin were significantly increased by pituitary grafting and the treatment with CyA further increased them. The mean half-life of prolactin was significantly increased in pituitary-grafted rats and was not changed by CyA administration, although it was decreased in sham-operated rats. The frequency of prolactin pulses was significantly decreased in pituitary-grafted as compared to sham-operated controls and was not further modified by CyA administration. However, in sham-operated rats a significant decrease of this parameter was observed. Duration of the prolactin peaks was significantly increased by pituitary grafting, and was not modified by CyA administration in any of the groups studied. The absolute amplitude of the prolactin peaks was significantly increased in pituitary-grafted as compared to sham-operated animals, and the treatment with CyA further increased this parameter in both groups. Mean values of LH were significantly increased in pituitary-grafted as compared to control rats. CyA administration significantly increased LH levels in sham-operated rats and decreased them in pituitary-grafted animals. The mean half-life, the pulse frequency and the duration of LH peaks were not modified by either pituitary grafting or CyA administration.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
35.
López-Robles J. R. Cobo M. J. Gutiérrez-Salcedo M. Martínez-Sánchez M. A. Gamboa-Rosales N. K. Herrera-Viedma E. 《Applied Intelligence》2021,51(9):6547-6568
Applied Intelligence - Applied Intelligence is one of the most important international scientific journals in the field of artificial intelligence. From 1991, Applied Intelligence has been oriented... 相似文献
36.
J. M. Martínez 《Computing》1987,39(4):307-325
We introduce a new method for solving Nonlinear Least Squares problems when the Jacobian matrix of the system is large and sparse. The main features of the new method are the following:
- The Gauss-Newton equation is “partially” solved at each iteration using a preconditioned Conjugate Gradient algorithm.
- The new point is obtained using a two-dimensional trust region scheme, similar to the one introduced by Bulteau and Vial.
37.
Irene Castellano-Pellicena Ciaran G. Morrison Mike Bell Clare OConnor Desmond J. Tobin 《International journal of molecular sciences》2021,22(6)
Melanin granules cluster within supra-nuclear caps in basal keratinocytes (KCs) of the human epidermis, where they protect KC genomic DNA against ultraviolet radiation (UVR) damage. While much is known about melanogenesis in melanocytes (MCs) and a moderate amount about melanin transfer from MC to KC, we know little about the fate of melanin once inside KCs. We recently reported that melanin fate in progenitor KCs is regulated by rare asymmetric organelle movement during mitosis. Here, we explore the role of actin, microtubules, and centrosome-associated machinery in distributing melanin within KCs. Short-term cultures of human skin explants were treated with cytochalasin-B and nocodazole to target actin filaments and microtubules, respectively. Treatment effects on melanin distribution were assessed by the Warthin–Starry stain, on centrosome-associated proteins by immunofluorescence microscopy, and on co-localisation with melanin granules by brightfield microscopy. Cytochalasin-B treatment disassembled supra-nuclear melanin caps, while nocodazole treatment moved melanin from the apical to basal KC domain. Centrosome and centriolar satellite-associated proteins showed a high degree of co-localisation with melanin. Thus, once melanin granules are transferred to KCs, their preferred apical distribution appears to be facilitated by coordinated movement of centrosomes and centriolar satellites. This mechanism may control melanin’s strategic position within UVR-exposed KCs. 相似文献
38.
Bernhard Beckermann Jorge Bustamante Reinaldo Martínez-Cruz José M. Quesada 《Calcolo》2014,51(2):319-328
For a given $\theta \in (a,b)$ , we investigate the question whether there exists a positive quadrature formula with maximal degree of precision which has the prescribed abscissa $\theta $ plus possibly $a$ and/or $b$ , the endpoints of the interval of integration. This study relies on recent results on the location of roots of quasi-orthogonal polynomials. The above positive quadrature formulae are useful in studying problems in one-sided polynomial $L_1$ approximation. 相似文献
39.
Jorge González-Domínguez Osni A. Marques María J. Martín Juan Touriño 《The Journal of supercomputing》2014,70(2):816-829
This paper examines four different strategies, each one with its own data distribution, for implementing the parallel conjugate gradient (CG) method and how they impact communication and overall performance. Firstly, typical 1D and 2D distributions of the matrix involved in CG computations are considered. Then, a new 2D version of the CG method with asymmetric workload, based on leaving some threads idle during part of the computation to reduce communication, is proposed. The four strategies are independent of sparse storage schemes and are implemented using Unified Parallel C (UPC), a Partitioned Global Address Space (PGAS) language. The strategies are evaluated on two different platforms through a set of matrices that exhibit distinct sparse patterns, demonstrating that our asymmetric proposal outperforms the others except for one matrix on one platform. 相似文献
40.
Enterotoxigenic <Emphasis Type="Italic">Escherichia coli</Emphasis> strains bind bovine milk gangliosides in a ceramide-dependent process 总被引:2,自引:0,他引:2
Diarrhea caused by enterotoxigenic Escherichia coli (ETEC) is the main infectious disease of newborn calves. The first step of infection involves bacterial attachment to the
intestinal mucosa. This adhesion is mediated by fimbriae that recognize some glycoconjugates on the host cell surface, in
particular, several gangliosides. Because milk also contains gangliosides, these have been suggested to serve as ligands for
bacterial fimbriae and thus prevent the bacterial attachment to mucosa. The most relevant ETEC strains in calves, including
those with K99 and F41 fimbriae, were assayed to determine whether they are able to bind gangliosides isolated from several
stages of bovine lactation. Both GM3 and GD3, the main gangliosides of milk, were recognized by ETEC strains, although the
different fimbriae showed diverse levels of affinity. Unexpectedly, the adhesion to colostral gangliosides was considerably
weaker than that to gangliosides from the other stages of lactation. Because the carbohydrate moiety did not change and because
differences in the percentages of unsaturated FA and sphingosine between colostrum and other stages were observed, we conclude
that the differences in adhesion could be due to a different composition of the ganglioside caramide. 相似文献