全文获取类型
收费全文 | 16219篇 |
免费 | 1006篇 |
国内免费 | 39篇 |
专业分类
17264篇 |
出版年
2023年 | 155篇 |
2022年 | 484篇 |
2021年 | 750篇 |
2020年 | 443篇 |
2019年 | 555篇 |
2018年 | 623篇 |
2017年 | 456篇 |
2016年 | 638篇 |
2015年 | 798篇 |
2014年 | 933篇 |
2013年 | 1220篇 |
2012年 | 1284篇 |
2011年 | 1112篇 |
2010年 | 667篇 |
2009年 | 554篇 |
2008年 | 673篇 |
2007年 | 688篇 |
2006年 | 606篇 |
2005年 | 570篇 |
2004年 | 493篇 |
2003年 | 410篇 |
2002年 | 388篇 |
2001年 | 233篇 |
2000年 | 204篇 |
1999年 | 161篇 |
1998年 | 105篇 |
1997年 | 72篇 |
1996年 | 75篇 |
1995年 | 70篇 |
1994年 | 51篇 |
1993年 | 51篇 |
1992年 | 110篇 |
1991年 | 117篇 |
1990年 | 119篇 |
1989年 | 105篇 |
1988年 | 113篇 |
1987年 | 81篇 |
1986年 | 71篇 |
1985年 | 94篇 |
1984年 | 82篇 |
1983年 | 71篇 |
1982年 | 47篇 |
1981年 | 51篇 |
1980年 | 46篇 |
1979年 | 55篇 |
1978年 | 62篇 |
1977年 | 48篇 |
1976年 | 57篇 |
1975年 | 42篇 |
1974年 | 49篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
Although proteomics has been exploited in a wide range of diseases for identification of biomarkers and pathophysiological mechanisms, there are still biomedical disciplines such as otology where proteomics platforms are underused due to technical challenges and/or complex features of the disease. Thus, in the past few years, healthcare and scientific agencies have advocated the development and adoption of proteomic technologies in otological research. However, few studies have been conducted and limited literature is available in this area. Here, we present the state of the art of proteomics in otology, discussing the substantial evidence from recent experimental models and clinical studies in inner-ear conditions. We also delineate a series of critical issues including minute size of the inner ear, delicacy and poor accessibility of tissue that researchers face while undertaking otology proteomics research. Furthermore, we provide perspective to enhance the impact and lead to the clinical implementation of these proteomics-based strategies. 相似文献
92.
93.
Ammerpohl O Thormeyer D Khan Z Appelskog IB Gojkovic Z Almqvist PM Ekström TJ 《Biochemical and biophysical research communications》2004,324(1):8-14
Malignant glioma patients have a dismal prognosis with an urgent need of new treatment modalities. Previously developed gene therapies for brain tumors showed promising results in experimental animal models, but failed in clinical trials due to low transfection rates and insufficient expression of the transgene in tumor cells, as well as low bystander killing effects. We have previously shown that the histone deacetylase inhibitor 4-phenylbutyrate (4-PB) enhances gap junction communication between glioma cells in culture. In this study, we demonstrate an activation of recombinant HSV-tk gene expression, and a dramatic enhancement of gap junction-mediated bystander killing effect by administration of the HSV-tk prodrug ganciclovir together with 4-PB. These findings that 4-PB potentiates "suicide gene" expression as well as enhances gap junctional communication and bystander killing of tumor cells justify further testing of this paradigm as an adjunct to suicide gene therapy of malignant gliomas. 相似文献
94.
Showket Hussain Vilas Nasare Malasha Kumari Shashi Sharma Mohammad Aijaz Khan Bhudev C. Das Mausumi Bharadwaj 《PloS one》2014,9(11)
Background
Human Papillomavirus (HPV) -associated cervical cancer is the second-most common cancer in women worldwide but it is the most frequent gynaecological cancer and cancer associated death in India women. The objective of this study was to assess knowledge about cervical cancer, HPV, HPV vaccine, HPV vaccine acceptance among school and undergraduates students and their parent’s perception about acceptance of HPV vaccine in Northern part of India (Delhi and NCR regions).Materials and Methods
A qualitative questionnaire based survey among 2500 urban/rural students aged 12–22 years was conducted.Results
Overall, a low frequency (15%) of HPV and cervical cancer awareness was observed in students and their parents. However, the awareness was much higher in females belonging to urban setup compared to boys with a perception that HPV causes cervical cancer in women only. Additionally, only (13%) participants who were aware of cervical cancer and HPV) were willing to accept HPV vaccination. Apparently, parents of female students were two times more willing to accept HPV vaccination for their ward than male students (p<0.001; OR 95%CI = 2.09 (1.58–2.76).Conclusion
Cervical cancer and HPV awareness among school, undergraduate students and also to their parents was found to be very low in this part of India. The level of awareness and education appears to be insignificant determinants in rural compared to urban setup. Better health education will be needed to maximize public awareness for cervical cancer prevention. 相似文献95.
Ali Sadeghi-Naini Ervis Sofroni Naum Papanicolau Omar Falou Linda Sugar Gerard Morton Martin J. Yaffe Robert Nam Alireza Sadeghian Michael C. Kolios Hans T. Chung Gregory J. Czarnota 《Translational oncology》2015,8(1):25-34
Three-dimensional quantitative ultrasound spectroscopic imaging of prostate was investigated clinically for the noninvasive detection and extent characterization of disease in cancer patients and compared to whole-mount, whole-gland histopathology of radical prostatectomy specimens. Fifteen patients with prostate cancer underwent a volumetric transrectal ultrasound scan before radical prostatectomy. Conventional-frequency (~ 5 MHz) ultrasound images and radiofrequency data were collected from patients. Normalized power spectra were used as the basis of quantitative ultrasound spectroscopy. Specifically, color-coded parametric maps of 0-MHz intercept, midband fit, and spectral slope were computed and used to characterize prostate tissue in ultrasound images. Areas of cancer were identified in whole-mount histopathology specimens, and disease extent was correlated to that estimated from quantitative ultrasound parametric images. Midband fit and 0-MHz intercept parameters were found to be best associated with the presence of disease as located on histopathology whole-mount sections. Obtained results indicated a correlation between disease extent estimated noninvasively based on midband fit parametric images and that identified histopathologically on prostatectomy specimens, with an r2 value of 0.71 (P < .0001). The 0-MHz intercept parameter demonstrated a lower level of correlation with histopathology. Spectral slope parametric maps offered no discrimination of disease. Multiple regression analysis produced a hybrid disease characterization model (r2 = 0.764, P < .05), implying that the midband fit biomarker had the greatest correlation with the histopathologic extent of disease. This work demonstrates that quantitative ultrasound spectroscopic imaging can be used for detecting prostate cancer and characterizing disease extent noninvasively, with corresponding gross three-dimensional histopathologic correlation. 相似文献
96.
Lucia Pitzurra Manuela Puliti Mohamed Ali Burhan Fuad Francesco Bistoni Elisabetta Blasi 《FEMS immunology and medical microbiology》1993,7(4):289-295
Abstract The present study was designed to establish the susceptibility of macrophage-mediated effector functions to tetanus toxin (TT). Using the murine macrophage cell line, GG2EE, generated in vitro by v- raf /v- myc oncogenes, we have previously provided evidence that TT selectively inhibits interferon gamma (IFN-γ), but not basal, lysozyme activity. Here we show that while neither phagocytic nor candidacidal activities are affected by TT treatment, antitumoral activity is significantly impaired after exposure to TT. This phenomenon, which is dose-dependent, is fully ascribed to the holotoxin, as heat inactivated TT, C or A-B fragments result ineffective. Furthermore, C but not A-B fragment competes with TT in abrogating its inhibitory effects. Overall, these data indicate that TT is not a broad-spectrum, down-regulating signal on macrophage-mediated functions, thus implying that its toxic action is exerted on specific molecular targets. 相似文献
97.
98.
99.
M. A. Khan J. M. Papadimitriou P. G. Holt B. A. Kakulas 《Histochemistry and cell biology》1973,36(2):173-183
Summary The histochemical activities of succinic dehydrogenase (SDH), creatine kinase (CK), sarcoplasmic reticular ATPase (SR-ATPase) and myosin ATPase were studied in serial sections of rabbit adductor muscle. Three fibre types were distinguished depending upon the distribution of the enzyme activities. The type II white fibres posessing minimal SDH showed high myosin ATPase, SR-ATPase and ATPase dependent CK activities. Red oxidative fibres showing high SDH fell into two distinct groups: One category had mainly a peripheral localization of SDH and showed an enzymatic profile identical to that of type II white fibres. The second category of red fibres displayed both a homogeneous distribution of small diformazan granules throughout the fibre as well as a sub-sarcolemmal collection when tested for SDH activity but possessed very low amounts of reaction product of the various enzymes of the energetic metabolism studied. Since it is well established that the myosin ATPase of a fibre correlates with its contraction time, the present histochemical investigation provides further support for this concept by demonstrating the presence of high SR-ATPase and ATPase dependent CK activities in all white and red fibres rich in myosin ATPase. 相似文献
100.
In this paper we present SNUAGE, a platform-as-a-service security framework for building secure and scalable multi-layered services based on the cloud computing model. SNUAGE ensures the authenticity, integrity, and confidentiality of data communication over the network links by creating a set of security associations between the data-bound components on the presentation layer and their respective data sources on the data persistence layer. SNUAGE encapsulates the security procedures, policies, and mechanisms in these security associations at the service development stage to form a collection of isolated and protected security domains. The secure communication among the entities in one security domain is governed and controlled by a standalone security processor and policy attached to this domain. This results into: (1) a safer data delivery mechanism that prevents security vulnerabilities in one domain from spreading to the other domains and controls the inter-domain information flow to protect the privacy of network data, (2) a reusable security framework that can be employed in existing platform-as-a-service environments and across diverse cloud computing service models, and (3) an increase in productivity and delivery of reliable and secure cloud computing services supported by a transparent programming model that relieves application developers from the intricate details of security programming. Last but not least, SNUAGE contributes to a major enhancement in the energy consumption and performance of supported cloud services by providing a suitable execution container in its protected security domains for a wide suite of energy- and performance-efficient cryptographic constructs such as those adopted by policy-driven and content-based security protocols. An energy analysis of the system shows, via real energy measurements, major savings in energy consumption on the consumer devices as well as on the cloud servers. Moreover, a sample implementation of the presented security framework is developed using Java and deployed and tested in a real cloud computing infrastructure using the Google App Engine service platform. Performance benchmarks show that the proposed framework provides a significant throughput enhancement compared to traditional network security protocols such as the Secure Sockets Layer and the Transport Layer Security protocols. 相似文献